Numerical analysis of energy saving performance for domestic refrigerator with SSPCM thermal storage of evaporator and condenser using TiO2-R600a or CuO-R600a nano-refrigerants Fatma Ezzahra Cherif and Habib Sammouda Laboratory of Energy and materials

Numerical analysis of energy saving performance for domestic refrigerator with SSPCM thermal storage of evaporator and condenser using TiO2-R600a or CuO-R600a nano-refrigerants
Fatma Ezzahra Cherif and Habib Sammouda
Laboratory of Energy and materials ( LR11ES34) at the School of Science and Technology of Hammam Sousse, University of Sousse, Tunisia.

Abstract
The efficiency of domestic refrigerators is largely affected by heat transfer performances of condensers and evaporators. This paper presents the potential improvement of heat transfer from evaporators and condensers by modeling an energy storage refrigerator. By simulation, the novel energy storage refrigerator used shape-stabilized phase change materials (SSPCM) in the condenser and evaporator shows a higher energy saving performance in which the electrical consumption saving can achieve 32%. Moreover, the effect of the application of nano-refrigerant on the heat transfer of a domestic refrigerator is also investigated and showed a higher enhancement on energy saving. Most important of all, the domestic refrigerator using both SSPCMs and nano-refrigerant reaches the large energy saving performance in which the electrical consumption saving can achieve 64%, which is better than the novel refrigerator using SSPCMs and pure refrigerant.

We Will Write a Custom Essay Specifically
For You For Only $13.90/page!


order now

Keywords:
Domestic refrigerator, Numerical simulation, Shape stabilized phase change material, Thermal storage, Energy saving, Nano-refrigerant.

Nomenclature
C mass fraction
Cp specific heat capacity (J kg-1 K-1)
COP coefficient of performance
K thermal conductivity (W m-1 K-1)
m mass (kg)
n polytropic index
P power (W)
p pressure (Pa)
PCM phase change material
SSPCM shape-stabilized phase change
material
T temperature (K)
t time (s)
U average heat transfer coefficient
(W m-2 K-1)
V volume flow rate (m3 s-1)
Greek letters
? compressor gaz transmission coefficient
density (kg m-3)
efficiency coefficient
volume fraction
Subscripts
amb ambient
air indoor air
c condenser
cd condenser tube
Com compressor
e evaporator
ev evaporator tube
f base fluid
ins insulation
nf nano-fluid
ref refrigerant
s solid nanoparticules
sspcm shape stabilized PCM
Wall cabinet wall
Th theoretical value
1. Introduction
Domestic refrigerators are one of the enormous reasons of the expanding pattern of energy consumption. It has been assumed that there are nearly one billion refrigeration appliances in usage in 2008 ADDIN CSL_CITATION {“citationItems”:{“id”:”ITEM-1″,”itemData”:{“DOI”:”10.1016/j.ijrefrig.2008.04.005″,”ISSN”:”0140-7007″,”author”:{“dropping-particle”:””,”family”:”Amara”,”given”:”S”,”non-dropping-particle”:”Ben”,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Laguerre”,”given”:”O”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Charrier-mojtabi”,”given”:”M”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Lartigue”,”given”:”B”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Flick”,”given”:”D”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},”container-title”:”International Journal of Refrigeration”,”id”:”ITEM-1″,”issue”:”8″,”issued”:{“date-parts”:”2008″},”page”:”1328-1340″,”publisher”:”Elsevier Ltd and IIR”,”title”:”PIV measurement of the flow field in a domestic refrigerator model : Comparison with 3D simulations ` l ‘ aide de la ve ´ locime ´ trie par image des particules du Mesures a ´ coulement dans un mode ` le de re ´ frige ´ rateur champ d ‘ e ` l ‘ aide de si”,”type”:”article-journal”,”volume”:”31″},”uris”:”http://www.mendeley.com/documents/?uuid=efe1593c-1a38-4eb8-a2e0-314f296ee2b6″},”mendeley”:{“formattedCitation”:”(Ben Amara et al. 2008)”,”plainTextFormattedCitation”:”(Ben Amara et al. 2008)”,”previouslyFormattedCitation”:”;sup;1;/sup;”},”properties”:{“noteIndex”:0},”schema”:”https://github.com/citation-style-language/schema/raw/master/csl-citation.json”}(Ben Amara et al. 2008). Thus, even a small performance enhancement of these appliances could bring great amounts of energy saving. The study of energy-saving technology of domestic refrigerators has important significance for relieving scarce energy sources and reducing greenhouse gas emission ADDIN CSL_CITATION {“citationItems”:{“id”:”ITEM-1″,”itemData”:{“DOI”:”10.1016/j.ijrefrig.2014.03.002″,”ISSN”:”0140-7007″,”author”:{“dropping-particle”:””,”family”:”Oró”,”given”:”Eduard”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Miró”,”given”:”Laia”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Farid”,”given”:”Mohammed M”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Martin”,”given”:”Viktoria”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Cabeza”,”given”:”Luisa F”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},”container-title”:”International Journal of Refrigeration”,”id”:”ITEM-1″,”issued”:{“date-parts”:”2014″},”publisher”:”Elsevier Ltd”,”title”:”Energy management and CO2 mitigation using phase change materials (PCM) for thermal energy storage (TES) in cold storage and transport”,”type”:”article-journal”},”uris”:”http://www.mendeley.com/documents/?uuid=016463ac-638a-4837-a8d4-01d8f65d0e39″},”mendeley”:{“formattedCitation”:”(Oró et al. 2014)”,”plainTextFormattedCitation”:”(Oró et al. 2014)”,”previouslyFormattedCitation”:”;sup;2;/sup;”},”properties”:{“noteIndex”:0},”schema”:”https://github.com/citation-style-language/schema/raw/master/csl-citation.json”}(Oró et al. 2014).

Many research institutions are exploring numerous methods to enhance energy performance of domestic refrigerator without increasing (or a small increasing) refrigerators’ production cost ADDIN CSL_CITATION {“citationItems”:{“id”:”ITEM-1″,”itemData”:{“DOI”:”10.1016/j.enconman.2014.09.064″,”ISSN”:”0196-8904″,”author”:{“dropping-particle”:””,”family”:”Ahmadi”,”given”:”Mohammad Hossein”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Ahmadi”,”given”:”Mohammad Ali”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},”container-title”:”ENERGY CONVERSION AND MANAGEMENT”,”id”:”ITEM-1″,”issued”:{“date-parts”:”2015″},”page”:”147-155″,”publisher”:”Elsevier Ltd”,”title”:”Thermodynamic analysis and optimization of an irreversible Ericsson cryogenic refrigerator cycle”,”type”:”article-journal”,”volume”:”89″},”uris”:”http://www.mendeley.com/documents/?uuid=dd8c8bdf-416d-46ba-a98f-d9a2be95f30d”},”mendeley”:{“formattedCitation”:”(Ahmadi and Ahmadi 2015)”,”plainTextFormattedCitation”:”(Ahmadi and Ahmadi 2015)”,”previouslyFormattedCitation”:”;sup;3;/sup;”},”properties”:{“noteIndex”:0},”schema”:”https://github.com/citation-style-language/schema/raw/master/csl-citation.json”}(Ahmadi and Ahmadi 2015) ADDIN CSL_CITATION {“citationItems”:{“id”:”ITEM-1″,”itemData”:{“DOI”:”10.1016/j.enconman.2014.04.086″,”ISSN”:”0196-8904″,”author”:{“dropping-particle”:””,”family”:”Yuan”,”given”:”Xu-dong”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Cheng”,”given”:”Wen-long”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},”container-title”:”ENERGY CONVERSION AND MANAGEMENT”,”id”:”ITEM-1″,”issued”:{“date-parts”:”2014″},”page”:”550-561″,”publisher”:”Elsevier Ltd”,”title”:”Multi-objective optimization of household refrigerator with novel heat-storage condensers by Genetic algorithm”,”type”:”article-journal”,”volume”:”84″},”uris”:”http://www.mendeley.com/documents/?uuid=bdb66ad2-305c-4488-b075-3db2e24aa932″},”mendeley”:{“formattedCitation”:”(Yuan and Cheng 2014)”,”plainTextFormattedCitation”:”(Yuan and Cheng 2014)”,”previouslyFormattedCitation”:”;sup;4;/sup;”},”properties”:{“noteIndex”:0},”schema”:”https://github.com/citation-style-language/schema/raw/master/csl-citation.json”}(Yuan and Cheng 2014). The performance of refrigeration appliance can be improved by enhancing the performance of the compressor ADDIN CSL_CITATION {“citationItems”:{“id”:”ITEM-1″,”itemData”:{“DOI”:”10.1016/j.ijrefrig.2013.12.004″,”ISSN”:”0140-7007″,”author”:{“dropping-particle”:””,”family”:”Xing”,”given”:”Meibo”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Wang”,”given”:”Ruixiang”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Yu”,”given”:”Jianlin”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},”container-title”:”International Journal of Refrigeration”,”id”:”ITEM-1″,”issued”:{“date-parts”:”2014″},”page”:”398-403″,”publisher”:”Elsevier Ltd”,”title”:”Application of fullerene C60 nano-oil for performance enhancement of domestic refrigerator compressors”,”type”:”article-journal”,”volume”:”40″},”uris”:”http://www.mendeley.com/documents/?uuid=eab69d6e-0f02-4d23-adad-779c0dbf89a3″},”mendeley”:{“formattedCitation”:”(Xing, Wang, and Yu 2014)”,”plainTextFormattedCitation”:”(Xing, Wang, and Yu 2014)”,”previouslyFormattedCitation”:”;sup;5;/sup;”},”properties”:{“noteIndex”:0},”schema”:”https://github.com/citation-style-language/schema/raw/master/csl-citation.json”}(Xing, Wang, and Yu 2014), or enhancing thermal insulation of refrigerator compartment ADDIN CSL_CITATION {“citationItems”:{“id”:”ITEM-1″,”itemData”:{“DOI”:”10.1016/j.ijrefrig.2014.07.010″,”ISSN”:”0140-7007″,”author”:{“dropping-particle”:””,”family”:”Hammond”,”given”:”E C”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Evans”,”given”:”J A”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},”container-title”:”International Journal of Refrigeration”,”id”:”ITEM-1″,”issue”:”0″,”issued”:{“date-parts”:”2014″},”page”:”58-65″,”publisher”:”Elsevier Ltd and IIR”,”title”:”ScienceDirect Application of Vacuum Insulation Panels in the cold chain e Analysis of viability Application de panneaux d ‘ isolation sous vide dans la chaine du froid e Analyse de la viabilit e”,”type”:”article-journal”,”volume”:”47″},”uris”:”http://www.mendeley.com/documents/?uuid=dba9ac9d-49e4-415d-a270-842f02a24fea”},”mendeley”:{“formattedCitation”:”(Hammond and Evans 2014)”,”plainTextFormattedCitation”:”(Hammond and Evans 2014)”,”previouslyFormattedCitation”:”<sup>6</sup>”},”properties”:{“noteIndex”:0},”schema”:”https://github.com/citation-style-language/schema/raw/master/csl-citation.json”}(Hammond and Evans 2014). Moreover, the efficiency of domestic refrigerator is largely affected by the performances of condenser and evaporator. Thus an optimization of them can widely improve the refrigerator performance ADDIN CSL_CITATION {“citationItems”:{“id”:”ITEM-1″,”itemData”:{“DOI”:”10.1016/j.energy.2015.05.005″,”ISSN”:”0360-5442″,”author”:{“dropping-particle”:””,”family”:”Islam”,”given”:”M R”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Jahangeer”,”given”:”K A”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Chua”,”given”:”K J”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},”container-title”:”Energy”,”id”:”ITEM-1″,”issued”:{“date-parts”:”2015″},”publisher”:”Elsevier Ltd”,”title”:”Experimental and numerical study of an evaporatively-cooled condenser of air-conditioning systems”,”type”:”article-journal”},”uris”:”http://www.mendeley.com/documents/?uuid=0089f01c-8bf7-4534-9fb3-1d7289257494″},”mendeley”:{“formattedCitation”:”(Islam, Jahangeer, and Chua 2015)”,”plainTextFormattedCitation”:”(Islam, Jahangeer, and Chua 2015)”,”previouslyFormattedCitation”:”<sup>7</sup>”},”properties”:{“noteIndex”:0},”schema”:”https://github.com/citation-style-language/schema/raw/master/csl-citation.json”}(Islam, Jahangeer, and Chua 2015). Many of these technologies have been relatively maturely developed, but there are some bottleneck issues to further enhance those technologies at present. Therefore, getting a better refrigerator performance requires numerous approaches, with the frame of smart buildings.
PCMs and nano-refrigerants have received great attention for heat transfer improvement of evaporator and condenser due to their multiple advantages.
Due to its high latent heat, PCMs are largely used in various applications as energy storage materials ADDIN CSL_CITATION {“citationItems”:{“id”:”ITEM-1″,”itemData”:{“DOI”:”10.1016/j.ijrefrig.2012.01.004″,”author”:{“dropping-particle”:””,”family”:”Oró”,”given”:”Eduard”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Miró”,”given”:”Laia”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Farid”,”given”:”Mohammed M”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Cabeza”,”given”:”Luisa F”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},”id”:”ITEM-1″,”issued”:{“date-parts”:”2012″},”page”:”984-991″,”title”:”Improving thermal performance of freezers using phase change materials ´ lioration de la performance thermique des conge ´ lateurs Ame ` l ‘ aide de mate ´ riaux a ` changement de phase a”,”type”:”article-journal”,”volume”:”35″},”uris”:”http://www.mendeley.com/documents/?uuid=1b6c2ee5-0205-46d0-be55-d266abf8cd2b”},”mendeley”:{“formattedCitation”:”(Oró et al. 2012)”,”plainTextFormattedCitation”:”(Oró et al. 2012)”,”previouslyFormattedCitation”:”;sup;8;/sup;”},”properties”:{“noteIndex”:0},”schema”:”https://github.com/citation-style-language/schema/raw/master/csl-citation.json”}(Oró et al. 2012). In domestic refrigerators, PCMs can be used as either cold or heat storage.
Some researchers integrated PCMs to condenser side of a refrigerator ADDIN CSL_CITATION {“citationItems”:{“id”:”ITEM-1″,”itemData”:{“author”:{“dropping-particle”:””,”family”:”Sonnenrein”,”given”:”G”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Elsner”,”given”:”A”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Morbach”,”given”:”A”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Fieback”,”given”:”K”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Vrabec”,”given”:”J”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Technology”,”given”:”Energy”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},”container-title”:”International Journal of Refrigeration”,”id”:”ITEM-1″,”issued”:{“date-parts”:”2015″},”page”:”154-160″,”title”:”Reducing the power consumption of household refrigerators through the integration of latent heat storage elements in wire-and- tube condensers”,”type”:”article-journal”,”volume”:”51″},”uris”:”http://www.mendeley.com/documents/?uuid=4d2651e5-b687-4a4c-9e86-d40dd1f64859″},”mendeley”:{“formattedCitation”:”(Sonnenrein et al. 2015)”,”plainTextFormattedCitation”:”(Sonnenrein et al. 2015)”,”previouslyFormattedCitation”:”;sup;9;/sup;”},”properties”:{“noteIndex”:0},”schema”:”https://github.com/citation-style-language/schema/raw/master/csl-citation.json”}(Sonnenrein et al. 2015). This enables the heat storage condenser refrigerator to have higher COP ADDIN CSL_CITATION {“citationItems”:{“id”:”ITEM-1″,”itemData”:{“DOI”:”10.1016/j.applthermaleng.2005.06.011″,”author”:{“dropping-particle”:””,”family”:”Wang”,”given”:”Fuqiao”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Maidment”,”given”:”Graeme”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Missenden”,”given”:”John”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Tozer”,”given”:”Robert”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},”id”:”ITEM-1″,”issued”:{“date-parts”:”2007″},”page”:”2893-2901″,”title”:”The novel use of phase change materials in refrigeration plant . Part 1 : Experimental investigation”,”type”:”article-journal”,”volume”:”27″},”uris”:”http://www.mendeley.com/documents/?uuid=4c0d8ff5-3f7b-43c2-bc28-427162ce3b2b”},”mendeley”:{“formattedCitation”:”(Wang et al. 2007)”,”plainTextFormattedCitation”:”(Wang et al. 2007)”,”previouslyFormattedCitation”:”;sup;10;/sup;”},”properties”:{“noteIndex”:0},”schema”:”https://github.com/citation-style-language/schema/raw/master/csl-citation.json”}(Wang et al. 2007), and some other advantages such as: continuous heat transfer, shorter compressor global On-time ratio, lower condensation temperature and lower energy consumption (about 12% saving) ADDIN CSL_CITATION {“citationItems”:{“id”:”ITEM-1″,”itemData”:{“DOI”:”10.1016/j.energy.2013.06.045″,”author”:{“dropping-particle”:””,”family”:”Cheng”,”given”:”Wen-long”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Yuan”,”given”:”Xu-Dong”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},”container-title”:”Energy”,”id”:”ITEM-1″,”issue”:”September 2013″,”issued”:{“date-parts”:”2013″},”page”:”265-276″,”title”:”Numerical analysis of a novel household refrigerator with shape-stabilized PCM ( phase change material ) heat …”,”type”:”article-journal”,”volume”:”59″},”uris”:”http://www.mendeley.com/documents/?uuid=bc528f0d-68ef-42ab-ad0f-26e0d287c479″},”mendeley”:{“formattedCitation”:”(Cheng and Yuan 2013)”,”plainTextFormattedCitation”:”(Cheng and Yuan 2013)”,”previouslyFormattedCitation”:”;sup;11;/sup;”},”properties”:{“noteIndex”:0},”schema”:”https://github.com/citation-style-language/schema/raw/master/csl-citation.json”}(Cheng and Yuan 2013). However, this enables the heat storage condenser refrigerator to have some disadvantages, such as more frequent compressor start/stop, and heat gain from heat storage condenser to indoor air during OFF time ADDIN CSL_CITATION {“citationItems”:{“id”:”ITEM-1″,”itemData”:{“DOI”:”10.1016/j.energy.2011.08.050″,”ISSN”:”0360-5442″,”author”:{“dropping-particle”:””,”family”:”Cheng”,”given”:”Wen-long”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Mei”,”given”:”Bao-jun”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Liu”,”given”:”Yi-ning”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Huang”,”given”:”Yong-hua”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Yuan”,”given”:”Xu-dong”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},”container-title”:”Energy”,”id”:”ITEM-1″,”issue”:”10″,”issued”:{“date-parts”:”2011″},”page”:”5797-5804″,”publisher”:”Elsevier Ltd”,”title”:”A novel household refrigerator with shape-stabilized PCM ( Phase Change Material ) heat storage condensers : An experimental investigation”,”type”:”article-journal”,”volume”:”36″},”uris”:”http://www.mendeley.com/documents/?uuid=38579dac-76e7-4925-8c21-ab8f9bce76a3″},”mendeley”:{“formattedCitation”:”(Cheng et al. 2011)”,”plainTextFormattedCitation”:”(Cheng et al. 2011)”,”previouslyFormattedCitation”:”;sup;12;/sup;”},”properties”:{“noteIndex”:0},”schema”:”https://github.com/citation-style-language/schema/raw/master/csl-citation.json”}(Cheng et al. 2011).
Other researchers integrated PCMs to evaporator side of a refrigerator. The refrigerator with cold storage evaporator allows the refrigeration system to reach higher COP compared with the conventional one ADDIN CSL_CITATION {“citationItems”:{“id”:”ITEM-1″,”itemData”:{“DOI”:”10.1016/j.applthermaleng.2017.07.113″,”ISSN”:”1359-4311″,”author”:{“dropping-particle”:””,”family”:”Elarem”,”given”:”R”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Mellouli”,”given”:”S”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Abhilash”,”given”:”E”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Jemni”,”given”:”A”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},”container-title”:”Applied Thermal Engineering”,”id”:”ITEM-1″,”issued”:{“date-parts”:”2017″},”publisher”:”Elsevier Ltd”,”title”:”Performance analysis of a household refrigerator integrating a PCM heat exchanger”,”type”:”article-journal”},”uris”:”http://www.mendeley.com/documents/?uuid=7814d1bc-1018-4cd9-8cd0-b95321524afc”},”mendeley”:{“formattedCitation”:”(Elarem et al. 2017)”,”plainTextFormattedCitation”:”(Elarem et al. 2017)”,”previouslyFormattedCitation”:”;sup;13;/sup;”},”properties”:{“noteIndex”:0},”schema”:”https://github.com/citation-style-language/schema/raw/master/csl-citation.json”}(Elarem et al. 2017), lower frequent compressor start/stop due to prolonged compressor OFF time ADDIN CSL_CITATION {“citationItems”:{“id”:”ITEM-1″,”itemData”:{“DOI”:”10.1142/S2010132513500296″,”ISBN”:”2010132513″,”author”:{“dropping-particle”:””,”family”:”AFROZ”,”given”:”H.M.M”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”KHAN”,”given”:”I.H”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},”container-title”:”International Journal of Air-Conditioning and Refrigeration”,”id”:”ITEM-1″,”issue”:”4″,”issued”:{“date-parts”:”2013″},”page”:”1-8″,”title”:”EXPERIMENTAL INVESTIGATION OF PERFORMANCE IMPROVEMENT OF HOUSEHOLD REFRIGERATOR USING PHASE”,”type”:”article-journal”,”volume”:”21″},”uris”:”http://www.mendeley.com/documents/?uuid=1aab47fc-9b94-4773-8b1c-d19a7798b3a6″},”mendeley”:{“formattedCitation”:”(AFROZ and KHAN 2013)”,”plainTextFormattedCitation”:”(AFROZ and KHAN 2013)”,”previouslyFormattedCitation”:”;sup;14;/sup;”},”properties”:{“noteIndex”:0},”schema”:”https://github.com/citation-style-language/schema/raw/master/csl-citation.json”}(AFROZ and KHAN 2013). However, this allows the refrigeration system to have at the same time some disadvantages, such as, higher condensation temperature and a prolonged compressor ON time during a cycle ADDIN CSL_CITATION {“citationItems”:{“id”:”ITEM-1″,”itemData”:{“DOI”:”10.1016/j.ijrefrig.2007.09.007″,”author”:{“dropping-particle”:””,”family”:”Azzouz”,”given”:”K”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Leducq”,”given”:”D”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Gobin”,”given”:”D”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},”id”:”ITEM-1″,”issued”:{“date-parts”:”2008″},”page”:”892-901″,”title”:”Performance enhancement of a household refrigerator by addition of latent heat storage ´ lioration des performances d ‘ un re ´ frige ´ rateur Ame domestique par usage d ‘ un accumulateur a”,”type”:”article-journal”,”volume”:”31″},”uris”:”http://www.mendeley.com/documents/?uuid=ba71bdac-85f8-401f-a1e0-26a7490479ec”},”mendeley”:{“formattedCitation”:”(Azzouz, Leducq, and Gobin 2008)”,”plainTextFormattedCitation”:”(Azzouz, Leducq, and Gobin 2008)”,”previouslyFormattedCitation”:”;sup;15;/sup;”},”properties”:{“noteIndex”:0},”schema”:”https://github.com/citation-style-language/schema/raw/master/csl-citation.json”}(Azzouz, Leducq, and Gobin 2008).

Evidently, the construction of cold storage evaporator has some advantages which can cover disadvantages of the construction of cold storage condenser and vice versa. It seems that simultaneous integration of PCMs at evaporator and condenser could be more beneficial ADDIN CSL_CITATION {“citationItems”:{“id”:”ITEM-1″,”itemData”:{“DOI”:”10.1016/j.enbuild.2015.06.016″,”ISSN”:”0378-7788″,”author”:{“dropping-particle”:””,”family”:”Joybari”,”given”:”M.M”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Haghighat”,”given”:”F”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Moffat”,”given”:”J”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Sra”,”given”:”P”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},”container-title”:”Energy ; Buildings”,”id”:”ITEM-1″,”issued”:{“date-parts”:”2015″},”page”:”111-124″,”publisher”:”Elsevier B.V.”,”title”:”Heat and Cold Storage using Phase Change Materials in Domestic Refrigeration Systems: The State-of-the-Art Review”,”type”:”article-journal”,”volume”:”106″},”uris”:”http://www.mendeley.com/documents/?uuid=8b89b20b-a9f3-40cb-a731-2e31b48714db”},”mendeley”:{“formattedCitation”:”(Joybari et al. 2015)”,”plainTextFormattedCitation”:”(Joybari et al. 2015)”,”previouslyFormattedCitation”:”;sup;16;/sup;”},”properties”:{“noteIndex”:0},”schema”:”https://github.com/citation-style-language/schema/raw/master/csl-citation.json”}(Joybari et al. 2015) . The manner of integration varied with climatic conditions and will be considered as variable parameter study.

Due to its wonderful potential in enhancing the heat transfer of evaporator and condenser, nano-refrigerants are largely used in modern domestic refrigerator. ADDIN CSL_CITATION {“citationItems”:{“id”:”ITEM-1″,”itemData”:{“author”:{“dropping-particle”:””,”family”:”Senthilkumara”,”given”:”A”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Praveenb”,”given”:”R”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},”container-title”:”Journal of chemical and pharmaceutical sciences”,”id”:”ITEM-1″,”issue”:”9″,”issued”:{“date-parts”:”2015″},”page”:”30-33″,”title”:”PERFORMANCE ANALYSIS OF A DOMESTIC REFRIGERATOR USING CUO – R600A NANO – REFRIGERANT AS WORKING FLUID”,”type”:”article-journal”},”uris”:”http://www.mendeley.com/documents/?uuid=2f528439-22c3-48ba-8ef8-ca334c8f8b47″},”mendeley”:{“formattedCitation”:”(Senthilkumara and Praveenb 2015)”,”manualFormatting”:”Senthilkumara and Praveenb (2015)”,”plainTextFormattedCitation”:”(Senthilkumara and Praveenb 2015)”,”previouslyFormattedCitation”:”;sup;17;/sup;”},”properties”:{“noteIndex”:0},”schema”:”https://github.com/citation-style-language/schema/raw/master/csl-citation.json”}Senthilkumara and Praveenb (2015) explored the efficiency of a domestic refrigerator using R600a/CuO nano-refrigerant. They concluded that 0.5 g/L concentration of CuO/R600a can save 20% of energy consumption compared with the conventional refrigerator using pure R600a. ADDIN CSL_CITATION {“citationItems”:{“id”:”ITEM-1″,”itemData”:{“author”:{“dropping-particle”:””,”family”:”Mohod”,”given”:”Vaishali P”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Kale”,”given”:”Nishikant W”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},”id”:”ITEM-1″,”issue”:”1″,”issued”:{“date-parts”:”2015″},”page”:”191-194″,”title”:”A Review on Heat Transfer Enhancement Using Nanoparticles Suspended With Refrigerants / Lubricating Oils in Refrigeration Systems”,”type”:”article-journal”,”volume”:”2″},”uris”:”http://www.mendeley.com/documents/?uuid=7bf50fe6-760c-460b-b938-9a5c1207d99e”},”mendeley”:{“formattedCitation”:”(Mohod and Kale 2015)”,”manualFormatting”:”Mohod and Kale (2015)”,”plainTextFormattedCitation”:”(Mohod and Kale 2015)”,”previouslyFormattedCitation”:”;sup;18;/sup;”},”properties”:{“noteIndex”:0},”schema”:”https://github.com/citation-style-language/schema/raw/master/csl-citation.json”}Mohod and Kale (2015) carried out analysis on heat transfer enhancement using nanoparticles suspended with refrigerants/lubricating oils in refrigeration systems. They concluded that nano-refrigerants have better thermal conductivity relatively to pure refrigerants. Consequently, the efficiency of refrigeration appliances increases with increasing nanoparticles concentration. In some cases reported, it increases up to specific volume concentration of nanoparticles and then decreases.
According to this bibliographic research, it appears that simultaneous integration of PCMs at heat exchangers (evaporator and condenser) and nano-refrigerants could be more beneficial in order to enhance the efficiency domestic refrigerators. Thus, in this paper, we propose to analyze these case by varying different tropical conditions such as the exterior ambient temperature and others parameters such as the concentration of the nanoparticles in refrigerant. Besides, two types of shape-stabilized phase change materials ADDIN CSL_CITATION {“citationItems”:{“id”:”ITEM-1″,”itemData”:{“DOI”:”10.1016/j.solmat.2010.05.020″,”ISSN”:”0927-0248″,”author”:{“dropping-particle”:””,”family”:”Cheng”,”given”:”Wen-long”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Zhang”,”given”:”Rong-ming”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Xie”,”given”:”Kun”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Liu”,”given”:”Na”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Wang”,”given”:”Jun”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},”container-title”:”Solar Energy Materials and Solar Cells”,”id”:”ITEM-1″,”issue”:”10″,”issued”:{“date-parts”:”2010″},”page”:”1636-1642″,”publisher”:”Elsevier”,”title”:”Heat conduction enhanced shape-stabilized paraffin / HDPE composite PCMs by graphite addition : Preparation and thermal properties”,”type”:”article-journal”,”volume”:”94″},”uris”:”http://www.mendeley.com/documents/?uuid=9129f3b8-190d-4921-86f7-95b46fbfdd11″},”mendeley”:{“formattedCitation”:”(Cheng et al. 2010)”,”plainTextFormattedCitation”:”(Cheng et al. 2010)”,”previouslyFormattedCitation”:”;sup;19;/sup;”},”properties”:{“noteIndex”:0},”schema”:”https://github.com/citation-style-language/schema/raw/master/csl-citation.json”}(Cheng et al. 2010) were chosen for constructing the cold storage evaporator and heat storage condenser. The following advantages of these SSPCMs are ADDIN CSL_CITATION {“citationItems”:{“id”:”ITEM-1″,”itemData”:{“DOI”:”10.1016/j.enconman.2016.11.029″,”ISSN”:”0196-8904″,”author”:{“dropping-particle”:””,”family”:”Cheng”,”given”:”Wen-long”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Ding”,”given”:”Miao”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Yuan”,”given”:”Xu-dong”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Han”,”given”:”Bing-chuan”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},”container-title”:”Energy Conversion and Management”,”id”:”ITEM-1″,”issued”:{“date-parts”:”2017″},”page”:”180-188″,”publisher”:”Elsevier Ltd”,”title”:”Analysis of energy saving performance for household refrigerator with thermal storage of condenser and evaporator”,”type”:”article-journal”,”volume”:”132″},”uris”:”http://www.mendeley.com/documents/?uuid=db7457a1-5ec2-4386-81d7-0480edcc9cce”},”mendeley”:{“formattedCitation”:”(Cheng et al. 2017)”,”plainTextFormattedCitation”:”(Cheng et al. 2017)”,”previouslyFormattedCitation”:”;sup;20;/sup;”},”properties”:{“noteIndex”:0},”schema”:”https://github.com/citation-style-language/schema/raw/master/csl-citation.json”}(Cheng et al. 2017): appropriate phase change temperatures to the two heat exchangers (evaporator and condenser), low cost of the SSPCMs, no corrosion and no liquid leakage during phase change progress and high thermal conductivity, which may improve the heat transfer during heat storage progress.
The isobutane (R600a) is more widely adopted in domestic ADDIN CSL_CITATION {“citationItems”:{“id”:”ITEM-1″,”itemData”:{“DOI”:”10.1016/j.ijrefrig.2013.02.012″,”ISSN”:”0140-7007″,”author”:{“dropping-particle”:””,”family”:”Joybari, Mahmood Mastani Hatamipour”,”given”:”Mahmood Sadegh”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Rahimi”,”given”:”Amir”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Modarres”,”given”:”Fatemeh Ghadiri”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},”container-title”:”International Journal of Refrigeration”,”id”:”ITEM-1″,”issued”:{“date-parts”:”2013″},”page”:”2-11″,”publisher”:”Elsevier Ltd and IIR”,”title”:”Exergy analysis and optimization of R600a as a replacement of R134a in a domestic refrigerator system ´ tique et optimisation du R600a comme Analyse exerge ` ne de remplacement du R134a dans le syste ` me frigorige ´ frige ´ rateur domestique frigorifique”,”type”:”article-journal”},”uris”:”http://www.mendeley.com/documents/?uuid=98d0d81c-2896-4e46-8d99-7944d6ab96d8″},”mendeley”:{“formattedCitation”:”(Joybari, Mahmood Mastani Hatamipour, Rahimi, and Modarres 2013)”,”plainTextFormattedCitation”:”(Joybari, Mahmood Mastani Hatamipour, Rahimi, and Modarres 2013)”,”previouslyFormattedCitation”:”;sup;21;/sup;”},”properties”:{“noteIndex”:0},”schema”:”https://github.com/citation-style-language/schema/raw/master/csl-citation.json”}(Joybari, Mahmood Mastani Hatamipour, Rahimi, and Modarres 2013) because it’s better environmental and energy performances with zero ozone depleting potential (ODP) and less global warming potential (GWP).
So, a novel SSPCMs dual energy storage refrigerator using nano-refrigerants is proposed and the dynamic simulation model of the refrigerator is established. The energy saving effect of the novel refrigerator is analyzed and compared with the conventional one.

2. Physical Models
The simulation model is composed of five parts: cold storage evaporator model, heat storage condenser model, compressor model, capillary model, and refrigerator compartment model ADDIN CSL_CITATION {“citationItems”:{“id”:”ITEM-1″,”itemData”:{“DOI”:”10.1016/j.energy.2013.06.045″,”author”:{“dropping-particle”:””,”family”:”Cheng”,”given”:”Wen-long”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Yuan”,”given”:”Xu-Dong”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},”container-title”:”Energy”,”id”:”ITEM-1″,”issue”:”September 2013″,”issued”:{“date-parts”:”2013″},”page”:”265-276″,”title”:”Numerical analysis of a novel household refrigerator with shape-stabilized PCM ( phase change material ) heat …”,”type”:”article-journal”,”volume”:”59″},”uris”:”http://www.mendeley.com/documents/?uuid=bc528f0d-68ef-42ab-ad0f-26e0d287c479″},”mendeley”:{“formattedCitation”:”(Cheng and Yuan 2013)”,”plainTextFormattedCitation”:”(Cheng and Yuan 2013)”,”previouslyFormattedCitation”:”;sup;11;/sup;”},”properties”:{“noteIndex”:0},”schema”:”https://github.com/citation-style-language/schema/raw/master/csl-citation.json”}(Cheng and Yuan 2013), ADDIN CSL_CITATION {“citationItems”:{“id”:”ITEM-1″,”itemData”:{“DOI”:”10.1016/j.enconman.2016.11.029″,”ISSN”:”0196-8904″,”author”:{“dropping-particle”:””,”family”:”Cheng”,”given”:”Wen-long”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Ding”,”given”:”Miao”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Yuan”,”given”:”Xu-dong”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Han”,”given”:”Bing-chuan”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},”container-title”:”Energy Conversion and Management”,”id”:”ITEM-1″,”issued”:{“date-parts”:”2017″},”page”:”180-188″,”publisher”:”Elsevier Ltd”,”title”:”Analysis of energy saving performance for household refrigerator with thermal storage of condenser and evaporator”,”type”:”article-journal”,”volume”:”132″},”uris”:”http://www.mendeley.com/documents/?uuid=db7457a1-5ec2-4386-81d7-0480edcc9cce”},”mendeley”:{“formattedCitation”:”(Cheng et al. 2017)”,”plainTextFormattedCitation”:”(Cheng et al. 2017)”,”previouslyFormattedCitation”:”;sup;20;/sup;”},”properties”:{“noteIndex”:0},”schema”:”https://github.com/citation-style-language/schema/raw/master/csl-citation.json”}(Cheng et al. 2017). The heat storage condenser and cold storage evaporator with SSPCMs are the only two different components of the novel refrigerator that are different of the ordinary one. In this paper we introduce in detail the numerical models of heat storage condenser and cold storage evaporator through the calculation of temperature fields by resolving energy equations of each exchanger system. The interactions between the different components of the ordinary refrigerator are presented in Fig. 1. The interactions between the different components of the energy storage refrigerator are presented in Fig. 2a, Fig 2.b and Fig 2.c.
2.1. Cold storage evaporator model
For cold storage evaporator, when the compressor starts, a portion of the cooling capacity passes to the phase change material and is stocked as the latent heat. During this process, a portion of the SSPCM passes from liquid state to solid state. Conversely, when the compressor stops, a part of SSPCM will pass from solid state to liquid state and the cooling capacity stocked in the material is liberated to the internal air of freezer to maintain its temperature constant. The SSPCM used was a novel composite phase change material in which the organic phase change material was combined in the support material of the organic high polymer material such as high density polyethylene (HDPE). So, we can assume that the SSPCM is in a “single solid phase” ADDIN CSL_CITATION {“citationItems”:{“id”:”ITEM-1″,”itemData”:{“DOI”:”10.1016/j.applthermaleng.2011.10.046″,”ISSN”:”1359-4311″,”author”:{“dropping-particle”:””,”family”:”Cheng”,”given”:”Wen-long”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Liu”,”given”:”Na”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Wu”,”given”:”Wan-fan”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},”container-title”:”Applied Thermal Engineering”,”id”:”ITEM-1″,”issued”:{“date-parts”:”2012″},”page”:”345-352″,”publisher”:”Elsevier Ltd”,”title”:”Studies on thermal properties and thermal control effectiveness of a new shape-stabilized phase change material with high thermal conductivity”,”type”:”article-journal”,”volume”:”36″},”uris”:”http://www.mendeley.com/documents/?uuid=900af903-8aa6-42b0-9594-fba890931419″},”mendeley”:{“formattedCitation”:”(Cheng, Liu, and Wu 2012)”,”plainTextFormattedCitation”:”(Cheng, Liu, and Wu 2012)”,”previouslyFormattedCitation”:”;sup;22;/sup;”},”properties”:{“noteIndex”:0},”schema”:”https://github.com/citation-style-language/schema/raw/master/csl-citation.json”}(Cheng, Liu, and Wu 2012), Thus, when the phase change progress occurred, the impact of convection can be neglected.

The assumptions of evaporator in this study are: (1) the flow of the inner tube is one-dimensional; (2) the refrigerant is supposed to be a Newtonian and incompressible fluid; (3) the refrigerant flow is assumed to be laminar, homogeneous and unidirectional; (4) the heat conduction of refrigerant and tube wall along axial direction are neglected; (5) pressure drop and the effect of the gravity are neglected.

According to above reasons, we consider the heat conduction is the only heat transfer form during the cold storage. The two-dimensional heat conduction differential equation of the SSPCM is expressed as follows (on subdomain SB1):

where and indicates the density, specific heat capacity, thermal conductivity and phase change temperature of the SSPCM, respectively.

Initial condition is expressed as follows:

where is the ambient temperature.

Boundary conditions are defined as below:

where U is the heat transfer coefficient. Tev is the evaporator tube temperature and Tair is the air temperature in the freezer. Subscript ”a” represents the boundary surface between the SSPCM and the evaporator tube and subscript ”b” represents the boundary surface between the SSPCM and the internal air.

The energy equation of the evaporator tube, completely encased by undecane, is expressed as follows (on subdomain SB2):

Boundary conditions are defined as below:
Boundary condition imposed between refrigerant flow and evaporator tube:
Boundary condition imposed between SSPCM and evaporator tube:

where and indicate the density, specific heat capacity and thermal conductivity of the evaporator tube, respectively. U is the heat transfer coefficient. Subscript ”ref” is refrigerant.

2.2. Heat storage condenser model
The sketch of the novel condenser is showed in the Fig. 2a. For the condenser, we selected the same assumptions of the evaporator. The two-dimensional heat conduction differential equation of the SSPCM is expressed as follows on (on subdomain SB3):

where and indicate the density, specific heat capacity, thermal conductivity and phase change temperature of the SSPCM, respectively.

Initial condition is expressed a follows:

Boundary conditions are defined as below:
where U is the heat transfer coefficient. Subscript ”a” represents the boundary surface between the SSPCM and the condenser tube, subscript ”b” represents the boundary surface between the SSPCM and the insulation, and subscript ”c” represents the boundary surface between the SSPCM and cabinet wall.

The energy equation of the condenser tube, completely encased by paraffin, is expressed as follows (on subdomain SB4):

Boundary conditions are defined as below:
Boundary condition imposed between refrigerant flow and condenser tube:
Boundary condition imposed between SSPCM and condenser tube:

where and indicate the density, specific heat capacity and thermal conductivity of the condenser tube, respectively. Tref is temperature of the refrigerant. U is the heat transfer coefficient.

2.3. Compressor model
In this paper, we used a hermetic reciprocating compressor in the domestic refrigerator. The compression process is assumed to be polytropic. The model of the compressor is referenced according to reference ADDIN CSL_CITATION {“citationItems”:{“id”:”ITEM-1″,”itemData”:{“DOI”:”10.1016/j.energy.2013.06.045″,”author”:{“dropping-particle”:””,”family”:”Cheng”,”given”:”Wen-long”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Yuan”,”given”:”Xu-Dong”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},”container-title”:”Energy”,”id”:”ITEM-1″,”issue”:”September 2013″,”issued”:{“date-parts”:”2013″},”page”:”265-276″,”title”:”Numerical analysis of a novel household refrigerator with shape-stabilized PCM ( phase change material ) heat …”,”type”:”article-journal”,”volume”:”59″},”uris”:”http://www.mendeley.com/documents/?uuid=bc528f0d-68ef-42ab-ad0f-26e0d287c479″},”mendeley”:{“formattedCitation”:”(Cheng and Yuan 2013)”,”plainTextFormattedCitation”:”(Cheng and Yuan 2013)”,”previouslyFormattedCitation”:”;sup;11;/sup;”},”properties”:{“noteIndex”:0},”schema”:”https://github.com/citation-style-language/schema/raw/master/csl-citation.json”}(Cheng and Yuan 2013).
The power of the compressor is ADDIN CSL_CITATION {“citationItems”:{“id”:”ITEM-1″,”itemData”:{“DOI”:”10.1016/j.energy.2013.06.045″,”author”:{“dropping-particle”:””,”family”:”Cheng”,”given”:”Wen-long”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Yuan”,”given”:”Xu-Dong”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},”container-title”:”Energy”,”id”:”ITEM-1″,”issue”:”September 2013″,”issued”:{“date-parts”:”2013″},”page”:”265-276″,”title”:”Numerical analysis of a novel household refrigerator with shape-stabilized PCM ( phase change material ) heat …”,”type”:”article-journal”,”volume”:”59″},”uris”:”http://www.mendeley.com/documents/?uuid=bc528f0d-68ef-42ab-ad0f-26e0d287c479″},”mendeley”:{“formattedCitation”:”(Cheng and Yuan 2013)”,”plainTextFormattedCitation”:”(Cheng and Yuan 2013)”,”previouslyFormattedCitation”:”;sup;11;/sup;”},”properties”:{“noteIndex”:0},”schema”:”https://github.com/citation-style-language/schema/raw/master/csl-citation.json”}(Cheng and Yuan 2013):

where Vth is the theoretical displacement, ? is the compressor gas transmission coefficient, is compressor efficiency, n is polytropic index; pc is condensation pressure and pe is evaporating pressure.
2.4. Thermophysical properties of nano-refrigerant
The definition of the thermophysical properties is one of the key parameters related to nano-fluids. In this paper, we assume that the nanoparticles are dispersed in the base fluid (refrigerant). Besides, the nature and the concentration of the nanoparticles significantly affect the thermophysical properties of the base fluid. These properties are approached by different classical models in the literature.
2.4.1. Density
In the literature, and in absence of experimental results, the density of the nano-fluids is often calculated on the basis of the mixture rule ADDIN CSL_CITATION {“citationItems”:{“id”:”ITEM-1″,”itemData”:{“DOI”:”10.1016/j.ijheatmasstransfer.2013.06.057″,”ISSN”:”0017-9310″,”author”:{“dropping-particle”:””,”family”:”Dhaidan”,”given”:”Nabeel S”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Khodadadi”,”given”:”J M”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Al-hattab”,”given”:”Tahseen A”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Al-mashat”,”given”:”Saad M”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},”container-title”:”International Journal of Heat and Mass Transfer”,”id”:”ITEM-1″,”issued”:{“date-parts”:”2013″},”page”:”672-683″,”publisher”:”Elsevier Ltd”,”title”:”Experimental and numerical investigation of melting of phase change material / nanoparticle suspensions in a square container subjected to a constant heat flux”,”type”:”article-journal”,”volume”:”66″},”uris”:”http://www.mendeley.com/documents/?uuid=392d140b-d314-4370-9d02-1df3811ef36c”},”mendeley”:{“formattedCitation”:”(Dhaidan et al. 2013)”,”plainTextFormattedCitation”:”(Dhaidan et al. 2013)”,”previouslyFormattedCitation”:”;sup;23;/sup;”},”properties”:{“noteIndex”:0},”schema”:”https://github.com/citation-style-language/schema/raw/master/csl-citation.json”}(Dhaidan et al. 2013) in which the nano-fluid is assumed to be homogeneous.

where subscripts nf, s and f are nano-fluid, nanoparticules and base fluid, respectively. is the volume fraction.
However, the volume fraction depends on the temperature of the nano-fluid at the time of mixing. It would be better to carry out this study, to take another parameter independent of the temperature, which is the mass fraction C.

where ms and mf are mass of nanoparticules and mass of base fluid, respectively. Therefore, it should be noted that the original equation is modified using a mass fraction instead of the volume fraction ADDIN CSL_CITATION {“citationItems”:{“id”:”ITEM-1″,”itemData”:{“DOI”:”10.1155/2014/138725″,”author”:{“dropping-particle”:””,”family”:”Aktas”,”given”:”Melih”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Dalkilic”,”given”:”Ahmet Selim”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Celen”,”given”:”Ali”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Cebi”,”given”:”Alican”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Mahian”,”given”:”Omid”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Wongwises”,”given”:”Somchai”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},”id”:”ITEM-1″,”issued”:{“date-parts”:”2014″},”title”:”A Theoretical Comparative Study on Nanorefrigerant Performance in a Single-Stage Vapor-Compression Refrigeration Cycle”,”type”:”article-journal”},”uris”:”http://www.mendeley.com/documents/?uuid=b0ae3e78-a8d1-4d13-a5a6-ffad796d3c58″},”mendeley”:{“formattedCitation”:”(Aktas et al. 2014)”,”plainTextFormattedCitation”:”(Aktas et al. 2014)”,”previouslyFormattedCitation”:”;sup;24;/sup;”},”properties”:{“noteIndex”:0},”schema”:”https://github.com/citation-style-language/schema/raw/master/csl-citation.json”}(Aktas et al. 2014) :

2.4.2. Heat conductivity
The effective heat conductivity (knf) of nano-refrigerant was determined using the Maxwell’s model ADDIN CSL_CITATION {“citationItems”:{“id”:”ITEM-1″,”itemData”:{“DOI”:”10.1016/j.ijheatmasstransfer.2013.06.057″,”ISSN”:”0017-9310″,”author”:{“dropping-particle”:””,”family”:”Dhaidan”,”given”:”Nabeel S”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Khodadadi”,”given”:”J M”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Al-hattab”,”given”:”Tahseen A”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Al-mashat”,”given”:”Saad M”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},”container-title”:”International Journal of Heat and Mass Transfer”,”id”:”ITEM-1″,”issued”:{“date-parts”:”2013″},”page”:”672-683″,”publisher”:”Elsevier Ltd”,”title”:”Experimental and numerical investigation of melting of phase change material / nanoparticle suspensions in a square container subjected to a constant heat flux”,”type”:”article-journal”,”volume”:”66″},”uris”:”http://www.mendeley.com/documents/?uuid=392d140b-d314-4370-9d02-1df3811ef36c”},”mendeley”:{“formattedCitation”:”(Dhaidan et al. 2013)”,”plainTextFormattedCitation”:”(Dhaidan et al. 2013)”,”previouslyFormattedCitation”:”;sup;23;/sup;”},”properties”:{“noteIndex”:0},”schema”:”https://github.com/citation-style-language/schema/raw/master/csl-citation.json”}(Dhaidan et al. 2013) :

2.4.3. Effective heat capacity Most studies in the literature use one of two models to determine the effective heat capacity of nano-fluids. One of these models is based on the mixture rule for homogeneous suspension ADDIN CSL_CITATION {“citationItems”:{“id”:”ITEM-1″,”itemData”:{“DOI”:”10.1016/j.ijheatmasstransfer.2013.06.057″,”ISSN”:”0017-9310″,”author”:{“dropping-particle”:””,”family”:”Dhaidan”,”given”:”Nabeel S”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Khodadadi”,”given”:”J M”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Al-hattab”,”given”:”Tahseen A”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Al-mashat”,”given”:”Saad M”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},”container-title”:”International Journal of Heat and Mass Transfer”,”id”:”ITEM-1″,”issued”:{“date-parts”:”2013″},”page”:”672-683″,”publisher”:”Elsevier Ltd”,”title”:”Experimental and numerical investigation of melting of phase change material / nanoparticle suspensions in a square container subjected to a constant heat flux”,”type”:”article-journal”,”volume”:”66″},”uris”:”http://www.mendeley.com/documents/?uuid=392d140b-d314-4370-9d02-1df3811ef36c”},”mendeley”:{“formattedCitation”:”(Dhaidan et al. 2013)”,”plainTextFormattedCitation”:”(Dhaidan et al. 2013)”,”previouslyFormattedCitation”:”;sup;23;/sup;”},”properties”:{“noteIndex”:0},”schema”:”https://github.com/citation-style-language/schema/raw/master/csl-citation.json”}(Dhaidan et al. 2013).

3. Results and discussion
3.1. Numerical models and Grid sensitivity analysis
The proposed problem has been investigated by developing a numerical code by means of the commercial software Comsol Multiphysics, which use finite elements method (FEM) to solve the conservation equations. To apply the FEM method a discretization of the computational domain is necessary in which we used convenient triangular reference elements for each subdomain. In order to ensure the consistency as well as the accuracy of the results, a successive mesh refinement of the grid (M1, M2,….., Mn) is necessary. Fig. 3 illustrates different grids (511167 elements, 867515 elements, 1219563 elements, ……, 1419474 elements) that are subjected to extensive testing procedures and the most appropriate one in terms of results accuracy has been considered. It is found that the operating time of the compressor do not vary from the grid M = 1219563 elements that are adapted in our study.

3.2. Validation
In this study, the research object is a double-door three-star refrigerator. The physical parameters of two types of SSPCMs are illustrated in Table 1: we choose undecane and paraffin as the phase change materials matrix when the undecane is integrated around the evaporator tube and paraffin is integrated around the condenser tube , respectively; high-density polyethylene (HDPE) as the supporting material; and expanded graphite powder (EG) as the thermal conduction improved material. The physical parameters of two types of solid nanoparticles, which are added to the pure refrigerant, are listed in Table 2 ADDIN CSL_CITATION {“citationItems”:{“id”:”ITEM-1″,”itemData”:{“DOI”:”10.1016/j.ijheatmasstransfer.2013.06.057″,”ISSN”:”0017-9310″,”author”:{“dropping-particle”:””,”family”:”Dhaidan”,”given”:”Nabeel S”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Khodadadi”,”given”:”J M”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Al-hattab”,”given”:”Tahseen A”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Al-mashat”,”given”:”Saad M”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},”container-title”:”International Journal of Heat and Mass Transfer”,”id”:”ITEM-1″,”issued”:{“date-parts”:”2013″},”page”:”672-683″,”publisher”:”Elsevier Ltd”,”title”:”Experimental and numerical investigation of melting of phase change material / nanoparticle suspensions in a square container subjected to a constant heat flux”,”type”:”article-journal”,”volume”:”66″},”uris”:”http://www.mendeley.com/documents/?uuid=392d140b-d314-4370-9d02-1df3811ef36c”},”mendeley”:{“formattedCitation”:”(Dhaidan et al. 2013)”,”plainTextFormattedCitation”:”(Dhaidan et al. 2013)”,”previouslyFormattedCitation”:”;sup;23;/sup;”},”properties”:{“noteIndex”:0},”schema”:”https://github.com/citation-style-language/schema/raw/master/csl-citation.json”}(Dhaidan et al. 2013) ADDIN CSL_CITATION {“citationItems”:{“id”:”ITEM-1″,”itemData”:{“author”:{“dropping-particle”:””,”family”:”Kaviarasu”,”given”:”C”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Prakash”,”given”:”D”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},”container-title”:”enginnering science and technologies review”,”id”:”ITEM-1″,”issue”:”4″,”issued”:{“date-parts”:”2016″},”page”:”26-36″,”title”:”Review on phase change materials with nanoparticule in engineering applications”,”type”:”article-journal”,”volume”:”9″},”uris”:”http://www.mendeley.com/documents/?uuid=05966524-77cc-4570-bf41-eca54f608d29″},”mendeley”:{“formattedCitation”:”(Kaviarasu and Prakash 2016)”,”plainTextFormattedCitation”:”(Kaviarasu and Prakash 2016)”,”previouslyFormattedCitation”:”;sup;25;/sup;”},”properties”:{“noteIndex”:0},”schema”:”https://github.com/citation-style-language/schema/raw/master/csl-citation.json”}(Kaviarasu and Prakash 2016) .

To validate our proposed thermal considerations, we initiated by modeling a previously published work of ADDIN CSL_CITATION {“citationItems”:{“id”:”ITEM-1″,”itemData”:{“DOI”:”10.1016/j.enconman.2016.11.029″,”ISSN”:”0196-8904″,”author”:{“dropping-particle”:””,”family”:”Cheng”,”given”:”Wen-long”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Ding”,”given”:”Miao”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Yuan”,”given”:”Xu-dong”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Han”,”given”:”Bing-chuan”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},”container-title”:”Energy Conversion and Management”,”id”:”ITEM-1″,”issued”:{“date-parts”:”2017″},”page”:”180-188″,”publisher”:”Elsevier Ltd”,”title”:”Analysis of energy saving performance for household refrigerator with thermal storage of condenser and evaporator”,”type”:”article-journal”,”volume”:”132″},”uris”:”http://www.mendeley.com/documents/?uuid=db7457a1-5ec2-4386-81d7-0480edcc9cce”},”mendeley”:{“formattedCitation”:”(Cheng et al. 2017)”,”manualFormatting”:”Cheng et al. (2017)”,”plainTextFormattedCitation”:”(Cheng et al. 2017)”,”previouslyFormattedCitation”:”;sup;20;/sup;”},”properties”:{“noteIndex”:0},”schema”:”https://github.com/citation-style-language/schema/raw/master/csl-citation.json”}Cheng et al. (2017) to carried out the effect of our assumptions on enhancing the thermal performances of domestic refrigerator, as will discussed later. The overall simulation models were tested under an ambient temperature around 25 °C and a freezer temperature around -18 °C. It was difficult to study some key parameters of the refrigerator such as the condensation pressure; which was taken from the experimental study ADDIN CSL_CITATION {“citationItems”:{“id”:”ITEM-1″,”itemData”:{“DOI”:”10.1016/j.energy.2011.08.050″,”ISSN”:”0360-5442″,”author”:{“dropping-particle”:””,”family”:”Cheng”,”given”:”Wen-long”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Mei”,”given”:”Bao-jun”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Liu”,”given”:”Yi-ning”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Huang”,”given”:”Yong-hua”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Yuan”,”given”:”Xu-dong”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},”container-title”:”Energy”,”id”:”ITEM-1″,”issue”:”10″,”issued”:{“date-parts”:”2011″},”page”:”5797-5804″,”publisher”:”Elsevier Ltd”,”title”:”A novel household refrigerator with shape-stabilized PCM ( Phase Change Material ) heat storage condensers : An experimental investigation”,”type”:”article-journal”,”volume”:”36″},”uris”:”http://www.mendeley.com/documents/?uuid=38579dac-76e7-4925-8c21-ab8f9bce76a3″},”mendeley”:{“formattedCitation”:”(Cheng et al. 2011)”,”plainTextFormattedCitation”:”(Cheng et al. 2011)”,”previouslyFormattedCitation”:”;sup;12;/sup;”},”properties”:{“noteIndex”:0},”schema”:”https://github.com/citation-style-language/schema/raw/master/csl-citation.json”}(Cheng et al. 2011).

For the refrigerator equipped with SSPCMs, the evaporator tube and condenser tube were only encased by the SSPCMs and the characteristics of the each component of this refrigerator were the same as those of the ordinary one. The results of Wen-long Cheng et al.ADDIN CSL_CITATION {“citationItems”:{“id”:”ITEM-1″,”itemData”:{“DOI”:”10.1016/j.enconman.2016.11.029″,”ISSN”:”0196-8904″,”author”:{“dropping-particle”:””,”family”:”Cheng”,”given”:”Wen-long”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Ding”,”given”:”Miao”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Yuan”,”given”:”Xu-dong”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Han”,”given”:”Bing-chuan”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},”container-title”:”Energy Conversion and Management”,”id”:”ITEM-1″,”issued”:{“date-parts”:”2017″},”page”:”180-188″,”publisher”:”Elsevier Ltd”,”title”:”Analysis of energy saving performance for household refrigerator with thermal storage of condenser and evaporator”,”type”:”article-journal”,”volume”:”132″},”uris”:”http://www.mendeley.com/documents/?uuid=db7457a1-5ec2-4386-81d7-0480edcc9cce”},”mendeley”:{“formattedCitation”:”(Cheng et al. 2017)”,”plainTextFormattedCitation”:”(Cheng et al. 2017)”,”previouslyFormattedCitation”:”;sup;20;/sup;”},”properties”:{“noteIndex”:0},”schema”:”https://github.com/citation-style-language/schema/raw/master/csl-citation.json”}(Cheng et al. 2017) and our results of evaporator temperature are illustrated in one figure. Fig. 4 illustrates the comparison of the ordinary refrigerator, and Fig. 5 illustrates the comparison of the refrigerator encased by SSPCMs. According to these figures, our results agree well with the results of ADDIN CSL_CITATION {“citationItems”:{“id”:”ITEM-1″,”itemData”:{“DOI”:”10.1016/j.enconman.2016.11.029″,”ISSN”:”0196-8904″,”author”:{“dropping-particle”:””,”family”:”Cheng”,”given”:”Wen-long”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Ding”,”given”:”Miao”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Yuan”,”given”:”Xu-dong”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Han”,”given”:”Bing-chuan”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},”container-title”:”Energy Conversion and Management”,”id”:”ITEM-1″,”issued”:{“date-parts”:”2017″},”page”:”180-188″,”publisher”:”Elsevier Ltd”,”title”:”Analysis of energy saving performance for household refrigerator with thermal storage of condenser and evaporator”,”type”:”article-journal”,”volume”:”132″},”uris”:”http://www.mendeley.com/documents/?uuid=db7457a1-5ec2-4386-81d7-0480edcc9cce”},”mendeley”:{“formattedCitation”:”(Cheng et al. 2017)”,”manualFormatting”:”Cheng et al. (2017)”,”plainTextFormattedCitation”:”(Cheng et al. 2017)”,”previouslyFormattedCitation”:”;sup;20;/sup;”},”properties”:{“noteIndex”:0},”schema”:”https://github.com/citation-style-language/schema/raw/master/csl-citation.json”}Cheng et al. (2017).

3.3. Work characteristics of the refrigerator using pure refrigerant (R600a) and SSPCMs
3.3.1. Evaporator temperature
The evaporator is the key component of domestic refrigerator. Thus, even small performance enhancement of its heat transfer brings great amounts of energy saving.
Fig. 6 illustrates the evaporator temperature comparison between the ordinary refrigerator and the energy storage refrigerator. For the ordinary refrigerator, the evaporator temperature decreases quickly and approaches to a steady value (about 243.78 K) when the compressor starts. When it is switched off, the evaporator temperature increases rapidly and approaches to a maximum value (about 254 K) until the next cycle begins. For the refrigerator equipped with SSPCMs, the evaporator temperature is reduced to a minimum value (about 245.72 K) during the On-time, and then it is back to the maximum value (about 254.9 K) during the off-time until the next cycle begins. Evidently, the evaporator temperature, for the refrigerator equipped with SSPCMs, is higher than that of the ordinary one.
Considering the close relationship between the evaporator temperature and the evaporating temperature, the higher evaporator temperature may leads to a higher evaporating temperature. The increase of evaporating temperature leads to an increasing evaporating pressure and decreasing compressor inlet specific volume. This enables to enhance the cooling capacity and the refrigeration efficiency.
3.3.2. Condenser temperature
The comparison of the condenser outlet temperatures between the ordinary refrigerator and the refrigerator equipped with SSPCMs is illustrated in Fig. 7. The condenser outlet temperature for the ordinary refrigerator rises rapidly from a minimum temperature (ambient temperature: about 298.15 K) to the highest temperature (about 306.5 K) after the compressor is switched on, and keeps at the highest temperature. The isobutane in the energy storage refrigerator is stocked in the condenser tube when the compressor is stopped and it stays at a higher temperature (more than the ambient temperature) due to the influence of the heat dissipation of SSPCM encased around the condenser. The condenser outlet temperature of the refrigerator equipped with SSPCMs increases more slowly after the compressor starts, and reaches the highest temperature which is lower than that of the ordinary one by about 7.8 °C, thus, the subcooling degree of the novel domestic refrigerator at the condenser outlet is larger. For the ordinary refrigerator when the compressor is stopped the outlet temperature begins to fall and reaches a stable value approximated to the ambient temperature. However, for the refrigerator equipped with SSPCMS another peak temperature is detected when the compressor is stopped. This can be explained by the fact that a portion of R600a flowing out of the condensers due to inertia is heated by the heat storage condenser-SSPCM with a temperature higher than the ambient temperature. Based on the above discussions, it can be simply concluded that the refrigerator equipped with SSPPCMs can achieves a higher enhancement on energy saving due to the lower condensation temperature and higher subcooling degree.

3.3.3. Evaporating pressure
The comparison of evaporating pressures between ordinary refrigerator and energy storage refrigerator are illustrated in Fig. 8. The evaporating pressure for the ordinary refrigerator decreases quickly and then maintains at a stable value (about 48 kPa) after the compressor starts. When the compressor stops, the evaporating pressure increases rapidly and turn back to the initial value (about 75 kPa). For the refrigerator equipped with SSPCMs, the maximum and minimum of evaporating pressures are about 77 kPa and 53.47 kPa respectively. Evidently, the evaporating pressure for the refrigerator equipped with SSPCMs is larger than that of the ordinary one. The enhancement of the evaporating pressure can lead to increasing evaporating temperature. This enables to enhance the cooling capacity and the refrigeration efficiency.
3.3.4. Refrigerating capacity
Fig. 9 illustrates the refrigerating capacity for the two types of refrigerators. It is found that the refrigerating capacity of the refrigerator equipped with SSPCMs is clearly larger than that of the ordinary one which is explained by the larger subcooling degree at the heat storage condenser according to Fig. 7.

3.3.5. Heat leakage
Fig. 10 illustrates the heat leakages of the refrigerator equipped with SSPCMs and the ordinary refrigerator in the frozen-food storage compartments. It can be observed that the heat leakage of the refrigerator equipped with SSPCMs is higher than that of the ordinary one during off-time, however slightly lower than and close to that of the ordinary one during on-time.
For the heat leakage, the heat transfer mechanism of the condenser of novel refrigerator is different from that of the ordinary one during on-time period; this can be explained according to Fig.11. For the ordinary condenser seen in Fig.11a, the condensation heat from the condenser tube was directly transferred to the outside wall; afterwards the outside wall transferred the heat to ambient and the indoor air of compartment through insulation. However for the condenser encased by SSPCM illustrated in Fig. 11b, a portion of condensation heat was stored within SSPCM, the other portion of condensation heat was passed to outside wall and then released to ambient and the indoor air of freezer. It can be simply concluded that the heat absorption to the out-sidewall of the refrigerator equipped with SSPCMs was less than that of the ordinary one in the on-time period.

For the heat leakage during off time, Fig. 11b illustrates the emplacement of SSPCM inside the insulation. The SSPCMs stores the large heat of condenser and then releases it to ambient air to reach continuous heat dissipation through the outside wall, therefore, the heat absorption to the out-sidewall of the refrigerator equipped with SSPCMs was higher than that of the ordinary one during off-time. Thus, the temperature difference between the outside wall and the indoor air of the refrigerator equipped with SSPCMs is larger than that of the ordinary one during off time and smaller than that of the ordinary one during on-time. It can be simply concluded that the lower outside wall temperature of the refrigerator equipped with SSPCMs during ON-time compensate the deficiency of the insulation amount decrease during OFF-time.

3.3.6. Compressor power
Fig. 12 illustrates the compressor power comparison of the refrigerator equipped with SSPCMs and the ordinary refrigerator. It can be observed that the refrigerator equipped with SSPCMs has the higher compressor power during ON-time. Besides, the operating time of two refrigerators in a total cycle are different, their comparisons are illustrated in Table 3.
For the ordinary refrigerator, its cycle time is only 60 min. So this type of refrigerators has more frequent compressor ON/OFF that leads to prolong the compressor work and increase noise generation. For the energy storage refrigerator, its cycle time is 230.5 min and has a compressor ON-time about 45.3 min and a compressor OFF-time about 185 min during a cycle.
Therefore, integration of SSPCM at evaporator side of a refrigerator prolongs the compressor OFF-time. Compared with the ordinary refrigerator, the refrigerator equipped with SSPCMs has larger OFF-time to ON-time ratio (4.08), thus, it will decrease the electrical energy consumption of the system. Also this leads two new important options for domestic refrigerators; to work off-peak and to keeps the freezer cold for longer periods even during power outages or blackouts.
Besides, the novel refrigerator equipped with SSPCMs encased around the evaporator and the condenser has a long cycle time (230.5 min) than refrigerator with only heat storage condenser (about 38 min) ADDIN CSL_CITATION {“citationItems”:{“id”:”ITEM-1″,”itemData”:{“DOI”:”10.1016/j.enconman.2016.11.029″,”ISSN”:”0196-8904″,”author”:{“dropping-particle”:””,”family”:”Cheng”,”given”:”Wen-long”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Ding”,”given”:”Miao”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Yuan”,”given”:”Xu-dong”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Han”,”given”:”Bing-chuan”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},”container-title”:”Energy Conversion and Management”,”id”:”ITEM-1″,”issued”:{“date-parts”:”2017″},”page”:”180-188″,”publisher”:”Elsevier Ltd”,”title”:”Analysis of energy saving performance for household refrigerator with thermal storage of condenser and evaporator”,”type”:”article-journal”,”volume”:”132″},”uris”:”http://www.mendeley.com/documents/?uuid=db7457a1-5ec2-4386-81d7-0480edcc9cce”},”mendeley”:{“formattedCitation”:”(Cheng et al. 2017)”,”plainTextFormattedCitation”:”(Cheng et al. 2017)”,”previouslyFormattedCitation”:”;sup;20;/sup;”},”properties”:{“noteIndex”:0},”schema”:”https://github.com/citation-style-language/schema/raw/master/csl-citation.json”}(Cheng et al. 2017) ) and a shorter ON time (45.3 min) during a cycle than refrigerator with only cold storage evaporator (about 65 min ADDIN CSL_CITATION {“citationItems”:{“id”:”ITEM-1″,”itemData”:{“DOI”:”10.1016/j.enconman.2016.11.029″,”ISSN”:”0196-8904″,”author”:{“dropping-particle”:””,”family”:”Cheng”,”given”:”Wen-long”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Ding”,”given”:”Miao”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Yuan”,”given”:”Xu-dong”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Han”,”given”:”Bing-chuan”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},”container-title”:”Energy Conversion and Management”,”id”:”ITEM-1″,”issued”:{“date-parts”:”2017″},”page”:”180-188″,”publisher”:”Elsevier Ltd”,”title”:”Analysis of energy saving performance for household refrigerator with thermal storage of condenser and evaporator”,”type”:”article-journal”,”volume”:”132″},”uris”:”http://www.mendeley.com/documents/?uuid=db7457a1-5ec2-4386-81d7-0480edcc9cce”},”mendeley”:{“formattedCitation”:”(Cheng et al. 2017)”,”plainTextFormattedCitation”:”(Cheng et al. 2017)”,”previouslyFormattedCitation”:”;sup;20;/sup;”},”properties”:{“noteIndex”:0},”schema”:”https://github.com/citation-style-language/schema/raw/master/csl-citation.json”}(Cheng et al. 2017)), which makes up the disadvantages of the refrigerator used only a SSPCM encased around the condenser and the refrigerator used only a SSPCM encased around the evaporator to some extent.

3.3.7. Electrical consumption
Table 4 illustrates the comparison of electrical consumption in 24 h and COP of two refrigerators. The energy consumption saving effect of the refrigerator equipped with SSPCMs is 32% compared with the ordinary refrigerator, Thus it can be concluded that the presence of undecane encased around the evaporator and paraffin encased around the condenser results in increasing COP and reducing the power consumption largely. Most important of all, the refrigerator equipped with both heat storage condenser and cold storage evaporator has the higher energy-saving efficiency, and the energy consumption is larger than the energy-saving efficiency of single energy storage refrigerators using only cold storage evaporator (12% ADDIN CSL_CITATION {“citationItems”:{“id”:”ITEM-1″,”itemData”:{“DOI”:”10.1016/j.enconman.2016.11.029″,”ISSN”:”0196-8904″,”author”:{“dropping-particle”:””,”family”:”Cheng”,”given”:”Wen-long”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Ding”,”given”:”Miao”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Yuan”,”given”:”Xu-dong”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Han”,”given”:”Bing-chuan”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},”container-title”:”Energy Conversion and Management”,”id”:”ITEM-1″,”issued”:{“date-parts”:”2017″},”page”:”180-188″,”publisher”:”Elsevier Ltd”,”title”:”Analysis of energy saving performance for household refrigerator with thermal storage of condenser and evaporator”,”type”:”article-journal”,”volume”:”132″},”uris”:”http://www.mendeley.com/documents/?uuid=db7457a1-5ec2-4386-81d7-0480edcc9cce”},”mendeley”:{“formattedCitation”:”(Cheng et al. 2017)”,”plainTextFormattedCitation”:”(Cheng et al. 2017)”,”previouslyFormattedCitation”:”;sup;20;/sup;”},”properties”:{“noteIndex”:0},”schema”:”https://github.com/citation-style-language/schema/raw/master/csl-citation.json”}(Cheng et al. 2017)) or heat storage condenser (12% ADDIN CSL_CITATION {“citationItems”:{“id”:”ITEM-1″,”itemData”:{“DOI”:”10.1016/j.enconman.2016.11.029″,”ISSN”:”0196-8904″,”author”:{“dropping-particle”:””,”family”:”Cheng”,”given”:”Wen-long”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Ding”,”given”:”Miao”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Yuan”,”given”:”Xu-dong”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Han”,”given”:”Bing-chuan”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},”container-title”:”Energy Conversion and Management”,”id”:”ITEM-1″,”issued”:{“date-parts”:”2017″},”page”:”180-188″,”publisher”:”Elsevier Ltd”,”title”:”Analysis of energy saving performance for household refrigerator with thermal storage of condenser and evaporator”,”type”:”article-journal”,”volume”:”132″},”uris”:”http://www.mendeley.com/documents/?uuid=db7457a1-5ec2-4386-81d7-0480edcc9cce”},”mendeley”:{“formattedCitation”:”(Cheng et al. 2017)”,”plainTextFormattedCitation”:”(Cheng et al. 2017)”,”previouslyFormattedCitation”:”;sup;20;/sup;”},”properties”:{“noteIndex”:0},”schema”:”https://github.com/citation-style-language/schema/raw/master/csl-citation.json”}(Cheng et al. 2017) ).

3.4. Effects of ambient temperature on the refrigerator performances using R600a and SSPCMs
The ambient temperature that varies with climatic conditions is the most important key parameter which can affect refrigerator performances. Thus we tested the effect of this parameter on the evaporator temperature and compressor operating time in the configuration without/with SSPCMs.
3.4.1 Ordinary refrigerator
The simulations of evaporator temperature in different ambient temperatures are illustrated in Fig. 13. The ambient temperatures are respectively 15 °C, 20 °C, 25 °C, 30 °C, 35°C and 40°C. The ON-time and OFF-time of a cycle and total cycle time are showed in Table 5.

For an ambient temperature less than 25 °C , the on-time, off-time and total cycle time are all shorter than those for an ambient temperature equal to 25°C according to Table 5, therefore, the compressor of the ordinary refrigerator starts more frequently. From Figure 13, it can be also observed that the temperature of the evaporator decreases with decreasing ambient temperature. The reason is that when the refrigerator is operating in a low thermal load, compartment temperature drops faster (due to the low heat gain through the walls). However, for an ambient temperature above 25 ° C, the compressor operates during a complete cycle. With increasing ambient temperature the temperature of the evaporator increases. This is due to the rapid increase in compartment temperature generated by heat generation increase. So the compressor has to work longer in order to maintain the freezer compartment cold.

It can be simply concluded that ambient temperature widely affects the performance of ordinary refrigerator. Thus, we must look for innovative solutions that allow us to solve this problem whatever the value of the ambient temperature. Among these solutions, the use of phase change materials appears to be an effective solution.

3.4.2 Energy storage refrigerator
The simulations of evaporator temperature in different ambient temperatures when the evaporator is completely encased by undecane, and the condenser is completely encased by the paraffin, are illustrated in Fig. 14. The ambient temperatures are respectively 15 °C, 20 °C, 25 °C, 30 °C, 35°C and 40°C.
Figure. 14 shows that, for an ambient temperature below 25 ° C, the compressor OFF-time increases. However, for an ambient temperature above 25 ° C, the compressor OFF-time decreases. The reason of the OFF-time decreasing or increasing is that the OFF-time of the compressor depends on the heat leakage in the frozen-food storage compartment and the thermo-physical properties of the SSPCM encased around the evaporator.

Due to its high thermal inertia (very high latent heat), the SSPCM is able to absorb the heat leakage whatever the value of the ambient temperature, which will accelerate or delay its melting time by keeping a constant temperature in the evaporator since it is completely encased by the SSPCM. Therefore a constant compressor ON period. It is as if the SSPCM will protect the evaporator against these leakage fluctuations.

The heat leakages during OFF-time, ON-time, complete cycle time and OFF/ON ratio under different ambient temperature are listed in Table 6.

So, we can conclude that we always get an OFF/ON ratio greater than that of the ordinary refrigerator (1.75) even with a decrease in compressor OFF-time. Therefore, whatever the value of the ambient temperature, it leads to a reduction in power consumption which proves the usefulness of our application.

3.5. Work characteristics of the refrigerator using nano-refrigerants
In order to enhance the performance of refrigerator technology, one of the methods applied is the addition of nanoparticles to the pure refrigerant.

During the performance tests, the operating parameters were recorded including evaporator temperature and operating time of compressor in both ordinary and energy storage refrigerator to compare the performance of the system with nano-refrigerant and pure refrigerant, so as to provide the basic data for the addition of the nanoparticles in the refrigeration appliances.

In this study, we use two types of nanoparticles which are: titanium oxide (TiO2) and copper oxide (CuO).

3.5.1. Ordinary refrigerator
Fig.15 compares the evaporator temperature of the ordinary refrigerator over one On-Off cycle using different mass fractions of R600a/TiO2 (the average particle diameters are about 50 nm ADDIN CSL_CITATION {“citationItems”:{“id”:”ITEM-1″,”itemData”:{“DOI”:”10.1016/j.enconman.2010.07.052″,”ISBN”:”2982663708″,”author”:{“dropping-particle”:””,”family”:”Bi”,”given”:”Shengshan”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Guo”,”given”:”Kai”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Liu”,”given”:”Zhigang”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Wu”,”given”:”Jiangtao”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},”id”:”ITEM-1″,”issued”:{“date-parts”:”2011″},”page”:”733-737″,”title”:”Performance of a domestic refrigerator using TiO 2 -R600a nano-refrigerant as working fluid”,”type”:”article-journal”,”volume”:”52″},”uris”:”http://www.mendeley.com/documents/?uuid=fab4664e-ed04-4eec-9996-6008b2e75309″},”mendeley”:{“formattedCitation”:”(Bi et al. 2011)”,”plainTextFormattedCitation”:”(Bi et al. 2011)”,”previouslyFormattedCitation”:”;sup;26;/sup;”},”properties”:{“noteIndex”:0},”schema”:”https://github.com/citation-style-language/schema/raw/master/csl-citation.json”}(Bi et al. 2011)), showing that evaporator temperature and compressor ON-time are reduced for the nano-refrigerant relative to the pure R600a, in which the largest reduction one is with 5g of TiO2.The addition of 1 g of TiO2 is sufficient because with 5 g there can be a risk of agglomeration. also, the total cycle time of the refrigerator are shortened, resulting in more frequent starts of the compressor which can damage the quality of the food and the life of the compressor.

Table 7 summarizes the compressor ON-time reduction with different mass fractions. These results confirm that the refrigerator performance with R600a/TiO2 nano-refrigerant is better than with the pure R600a. The reason may be that the nanoparticles enhance the heat transfer characteristics of the refrigerant, thus, nanoparticules help in performance enhancement of heat exchanger. The power consumption is reduced.
The results above are similar with the former investigation of ADDIN CSL_CITATION {“citationItems”:{“id”:”ITEM-1″,”itemData”:{“DOI”:”10.1016/j.enconman.2010.07.052″,”ISBN”:”2982663708″,”author”:{“dropping-particle”:””,”family”:”Bi”,”given”:”Shengshan”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Guo”,”given”:”Kai”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Liu”,”given”:”Zhigang”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Wu”,”given”:”Jiangtao”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},”id”:”ITEM-1″,”issued”:{“date-parts”:”2011″},”page”:”733-737″,”title”:”Performance of a domestic refrigerator using TiO 2 -R600a nano-refrigerant as working fluid”,”type”:”article-journal”,”volume”:”52″},”uris”:”http://www.mendeley.com/documents/?uuid=fab4664e-ed04-4eec-9996-6008b2e75309″},”mendeley”:{“formattedCitation”:”(Bi et al. 2011)”,”manualFormatting”:”Bi et al. (2011)”,”plainTextFormattedCitation”:”(Bi et al. 2011)”,”previouslyFormattedCitation”:”;sup;26;/sup;”},”properties”:{“noteIndex”:0},”schema”:”https://github.com/citation-style-language/schema/raw/master/csl-citation.json”}Bi et al. (2011) about R600a/TiO2 nano-refrigerant as working fluid. Moreover, these results indicate that R600a/TiO2 nano-refrigerant works normally and safely in the refrigerator.

Fig. 16 compares the evaporator temperature of the ordinary refrigerator over one On-Off cycle using different mass fractions of R600a/CuO (the average particle diameters are about 50 nm ADDIN CSL_CITATION {“citationItems”:{“id”:”ITEM-1″,”itemData”:{“author”:{“dropping-particle”:””,”family”:”Senthilkumara”,”given”:”A”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Praveenb”,”given”:”R”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},”container-title”:”Journal of chemical and pharmaceutical sciences”,”id”:”ITEM-1″,”issue”:”9″,”issued”:{“date-parts”:”2015″},”page”:”30-33″,”title”:”PERFORMANCE ANALYSIS OF A DOMESTIC REFRIGERATOR USING CUO – R600A NANO – REFRIGERANT AS WORKING FLUID”,”type”:”article-journal”},”uris”:”http://www.mendeley.com/documents/?uuid=2f528439-22c3-48ba-8ef8-ca334c8f8b47″},”mendeley”:{“formattedCitation”:”(Senthilkumara and Praveenb 2015)”,”plainTextFormattedCitation”:”(Senthilkumara and Praveenb 2015)”,”previouslyFormattedCitation”:”;sup;17;/sup;”},”properties”:{“noteIndex”:0},”schema”:”https://github.com/citation-style-language/schema/raw/master/csl-citation.json”}(Senthilkumara and Praveenb 2015)). The results were similar to the application of R600a/TiO2.
Table 8 summarizes the compressor ON-time reduction with different mass fractions of R600a/CuO. From Table 8, the ON-time reduction is 25% for the 1 g of CuO which is 9 % more than for the 1 g of TiO2. As well, The ON-time reduction was 49% for the 2 g of CuO which is 33 % more than for the 2 g of TiO2. This is due in fact to the high thermal conductivity of CuO (18 W / m K ADDIN CSL_CITATION {“citationItems”:{“id”:”ITEM-1″,”itemData”:{“DOI”:”10.1016/j.ijheatmasstransfer.2013.06.057″,”ISSN”:”0017-9310″,”author”:{“dropping-particle”:””,”family”:”Dhaidan”,”given”:”Nabeel S”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Khodadadi”,”given”:”J M”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Al-hattab”,”given”:”Tahseen A”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Al-mashat”,”given”:”Saad M”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},”container-title”:”International Journal of Heat and Mass Transfer”,”id”:”ITEM-1″,”issued”:{“date-parts”:”2013″},”page”:”672-683″,”publisher”:”Elsevier Ltd”,”title”:”Experimental and numerical investigation of melting of phase change material / nanoparticle suspensions in a square container subjected to a constant heat flux”,”type”:”article-journal”,”volume”:”66″},”uris”:”http://www.mendeley.com/documents/?uuid=392d140b-d314-4370-9d02-1df3811ef36c”},”mendeley”:{“formattedCitation”:”(Dhaidan et al. 2013)”,”plainTextFormattedCitation”:”(Dhaidan et al. 2013)”,”previouslyFormattedCitation”:”;sup;23;/sup;”},”properties”:{“noteIndex”:0},”schema”:”https://github.com/citation-style-language/schema/raw/master/csl-citation.json”}(Dhaidan et al. 2013)) compared to TiO2 (8.4 W / m K ADDIN CSL_CITATION {“citationItems”:{“id”:”ITEM-1″,”itemData”:{“author”:{“dropping-particle”:””,”family”:”Kaviarasu”,”given”:”C”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Prakash”,”given”:”D”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},”container-title”:”enginnering science and technologies review”,”id”:”ITEM-1″,”issue”:”4″,”issued”:{“date-parts”:”2016″},”page”:”26-36″,”title”:”Review on phase change materials with nanoparticule in engineering applications”,”type”:”article-journal”,”volume”:”9″},”uris”:”http://www.mendeley.com/documents/?uuid=05966524-77cc-4570-bf41-eca54f608d29″},”mendeley”:{“formattedCitation”:”(Kaviarasu and Prakash 2016)”,”plainTextFormattedCitation”:”(Kaviarasu and Prakash 2016)”,”previouslyFormattedCitation”:”;sup;25;/sup;”},”properties”:{“noteIndex”:0},”schema”:”https://github.com/citation-style-language/schema/raw/master/csl-citation.json”}(Kaviarasu and Prakash 2016)).

The results above are similar with the former investigation of ADDIN CSL_CITATION {“citationItems”:{“id”:”ITEM-1″,”itemData”:{“author”:{“dropping-particle”:””,”family”:”Senthilkumara”,”given”:”A”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Praveenb”,”given”:”R”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},”container-title”:”Journal of chemical and pharmaceutical sciences”,”id”:”ITEM-1″,”issue”:”9″,”issued”:{“date-parts”:”2015″},”page”:”30-33″,”title”:”PERFORMANCE ANALYSIS OF A DOMESTIC REFRIGERATOR USING CUO – R600A NANO – REFRIGERANT AS WORKING FLUID”,”type”:”article-journal”},”uris”:”http://www.mendeley.com/documents/?uuid=2f528439-22c3-48ba-8ef8-ca334c8f8b47″},”mendeley”:{“formattedCitation”:”(Senthilkumara and Praveenb 2015)”,”manualFormatting”:”Senthilkumara and Praveenb (2015)”,”plainTextFormattedCitation”:”(Senthilkumara and Praveenb 2015)”,”previouslyFormattedCitation”:”;sup;17;/sup;”},”properties”:{“noteIndex”:0},”schema”:”https://github.com/citation-style-language/schema/raw/master/csl-citation.json”}Senthilkumara and Praveenb (2015) about R600a/CuO nano-refrigerant as working fluid. Moreover, these results indicate that R600a/CuO nano-refrigerants work normally and safely in the refrigerator.

3.5.2. Energy storage refrigerator
Fig. 17 compares the evaporator temperature of the refrigerator equipped with SSPCMs over one On-Off cycle using different mass fractions of R600a/TiO2. Table 9 summarizes the compressor ON-time reduction with different mass fractions of R600a/TiO2.

According to Figure 17 and Table 9, the temperature of evaporator increases, the ON-time cycle of compressor decreases, when mass fraction of R600a/TiO2 increases up to specific mass fraction (0,014). However, these modifications are reduced for a mass fraction of the order of 0,065. Thus, in some cases reported (as in our application for a domestic refrigerator with energy storage materials), there are certain specific concentrations for which the heat transfer performance increases and then decreases ADDIN CSL_CITATION {“citationItems”:{“id”:”ITEM-1″,”itemData”:{“author”:{“dropping-particle”:””,”family”:”Mohod”,”given”:”Vaishali P”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Kale”,”given”:”Nishikant W”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},”id”:”ITEM-1″,”issue”:”1″,”issued”:{“date-parts”:”2015″},”page”:”191-194″,”title”:”A Review on Heat Transfer Enhancement Using Nanoparticles Suspended With Refrigerants / Lubricating Oils in Refrigeration Systems”,”type”:”article-journal”,”volume”:”2″},”uris”:”http://www.mendeley.com/documents/?uuid=7bf50fe6-760c-460b-b938-9a5c1207d99e”},”mendeley”:{“formattedCitation”:”(Mohod and Kale 2015)”,”plainTextFormattedCitation”:”(Mohod and Kale 2015)”,”previouslyFormattedCitation”:”;sup;18;/sup;”},”properties”:{“noteIndex”:0},”schema”:”https://github.com/citation-style-language/schema/raw/master/csl-citation.json”}(Mohod and Kale 2015). In fact, the increase in temperature is helpful for: Maintaining the temperature stability of the freezer, enhancing the efficiency of the system and the quality of the food. In addition, it helps to reduce power consumption.
The reduction in compressor operating time is due to the improvement of the heat transfer characteristics of the R600a caused by nanoparticules added. An optimal concentration of nanoparticles mixed with base fluid need to be investigated in order to achieve the best performance enhancement.

These results confirm that the energy storage refrigerator performance with R600a/TiO2 nano-refrigerant is better than with the pure R600a. Compared with ordinary one used R600a/TiO2 as working fluid, the enhancement in heat transfer is observed more in the refrigerator with thermal storage, because more heat transfer through the exchangers due to SSPCM, thus, the power consumption is more reduced.

Fig. 18 compared the evaporator temperature of the energy storage refrigerator over one On-Off cycle using different mass fractions of R600a/CuO. The results were similar to the application of R600a/TiO2.
Table 10 summarizes the compressor ON-time reduction with different mass fractions of R600a/CuO. From Table 10, with 0.5 g of CuO, the ON-time reduction of the compressor is about 32% instead of 0% with 0.5 g of TiO2. This is due in fact to the high thermal conductivity of CuO (18 W / m K ADDIN CSL_CITATION {“citationItems”:{“id”:”ITEM-1″,”itemData”:{“DOI”:”10.1016/j.ijheatmasstransfer.2013.06.057″,”ISSN”:”0017-9310″,”author”:{“dropping-particle”:””,”family”:”Dhaidan”,”given”:”Nabeel S”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Khodadadi”,”given”:”J M”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Al-hattab”,”given”:”Tahseen A”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Al-mashat”,”given”:”Saad M”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},”container-title”:”International Journal of Heat and Mass Transfer”,”id”:”ITEM-1″,”issued”:{“date-parts”:”2013″},”page”:”672-683″,”publisher”:”Elsevier Ltd”,”title”:”Experimental and numerical investigation of melting of phase change material / nanoparticle suspensions in a square container subjected to a constant heat flux”,”type”:”article-journal”,”volume”:”66″},”uris”:”http://www.mendeley.com/documents/?uuid=392d140b-d314-4370-9d02-1df3811ef36c”},”mendeley”:{“formattedCitation”:”(Dhaidan et al. 2013)”,”plainTextFormattedCitation”:”(Dhaidan et al. 2013)”,”previouslyFormattedCitation”:”;sup;23;/sup;”},”properties”:{“noteIndex”:0},”schema”:”https://github.com/citation-style-language/schema/raw/master/csl-citation.json”}(Dhaidan et al. 2013)) compared to TiO2 (8.4 W / m K ADDIN CSL_CITATION {“citationItems”:{“id”:”ITEM-1″,”itemData”:{“author”:{“dropping-particle”:””,”family”:”Kaviarasu”,”given”:”C”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Prakash”,”given”:”D”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},”container-title”:”enginnering science and technologies review”,”id”:”ITEM-1″,”issue”:”4″,”issued”:{“date-parts”:”2016″},”page”:”26-36″,”title”:”Review on phase change materials with nanoparticule in engineering applications”,”type”:”article-journal”,”volume”:”9″},”uris”:”http://www.mendeley.com/documents/?uuid=05966524-77cc-4570-bf41-eca54f608d29″},”mendeley”:{“formattedCitation”:”(Kaviarasu and Prakash 2016)”,”plainTextFormattedCitation”:”(Kaviarasu and Prakash 2016)”,”previouslyFormattedCitation”:”;sup;25;/sup;”},”properties”:{“noteIndex”:0},”schema”:”https://github.com/citation-style-language/schema/raw/master/csl-citation.json”}(Kaviarasu and Prakash 2016)).

4. Conclusion
In order to enhance the performance of the refrigeration technology and ensure the power consumption reduction, a novel cold storage evaporator and heat storage condenser refrigerator using nano-refrigerant is proposed. In this paper, a dynamic simulation model was carried out to investigate the work characteristics of the novel refrigerator and the effects of some key parameters. By simulation, some important conclusions can be cited as follows:
The refrigerator with cold storage evaporator and heat storage condenser can achieve better heat transfer and better performances than ordinary one, which can improve the cooling capacity and enhance the refrigeration efficiency.
The refrigerator equipped with SSPCMs operates under a lower condensation temperature and a larger subcooling degree. Consequently, it had a larger COP.

The refrigerator equipped with SSPCMs can reach continuous heat/cold rejection from condenser/evaporator during a complete cycle.
Most important of all, the refrigerator equipped with SSPCMs can reach a higher energy saving with largest Off-time to On-time ratio of 4 and the electrical consumption saving can achieve 32%.

Because of their enhanced heat transfer characteristic and enhancement in energy saving, it is safe to consider that nano-refrigerants will be used as a portion of many modern refrigeration appliances rather than later. The most important findings can be extracted from this work:
The addition of nanoparticles to pure refrigerant can improve heat transfer of heat exchangers through the enhancement of thermal conductivities.

Nano-refrigerants help in performance enhancement of heat exchanger (Condenser and evaporator). This can help in increasing the efficiency of the refrigerator, thus enhancing the energy saving feature.

An optimal concentration of nanoparticles dispersed in base fluid need to be investigated in order to obtain the best performance improvement.

According to the simulation results, it can be found that the refrigerator used only thermal storage has a longer compressor ON time during a cycle. The ordinary refrigerator used only nano-refrigerant has frequent compressor ON/OFF. However the refrigerator equipped with SSPCMs using 0.1 g of CuO has a shorter ON time (30 min) and a longer OFF time (185) during a cycle, which achieve the highest energy saving effect (64%). Obviously, the refrigerator equipped with SSPCMs used nano-refrigerant can couple the advantages of thermal storage and nanoparticles added, and makes up their disadvantages in some aspects: lower compressor ON/OFF frequency, lower noise generation, lower vibration, shorter compressor ON time and longer compressor OFF time during a cycle which can significantly increase the energy saving effect.

References
ADDIN Mendeley Bibliography CSL_BIBLIOGRAPHY AFROZ, H.M.M, and I.H KHAN. 2013. “EXPERIMENTAL INVESTIGATION OF PERFORMANCE IMPROVEMENT OF HOUSEHOLD REFRIGERATOR USING PHASE.” International Journal of Air-Conditioning and Refrigeration 21(4): 1–8.

Ahmadi, Mohammad Hossein, and Mohammad Ali Ahmadi. 2015. “Thermodynamic Analysis and Optimization of an Irreversible Ericsson Cryogenic Refrigerator Cycle.” ENERGY CONVERSION AND MANAGEMENT 89: 147–55. http://dx.doi.org/10.1016/j.enconman.2014.09.064.

Aktas, Melih et al. 2014. “A Theoretical Comparative Study on Nanorefrigerant Performance in a Single-Stage Vapor-Compression Refrigeration Cycle.”
Ben Amara, S et al. 2008. “PIV Measurement of the Flow Field in a Domestic Refrigerator Model?: Comparison with 3D Simulations.” International Journal of Refrigeration 31 (8): 1328–40 http://dx.doi.org/10.1016/j.ijrefrig.2008.04.005.

Azzouz, K, D Leducq, and D Gobin. 2008. “Performance Enhancement of a Household Refrigerator by Addition of Latent Heat Storage ´ Lioration Des Performances d ‘ Un Re ´ Frige ´ Rateur Ame Domestique Par Usage d ‘ Un Accumulateur a.” 31: 892–901.

Bi, Shengshan, Kai Guo, Zhigang Liu, and Jiangtao Wu. 2011. “Performance of a Domestic Refrigerator Using TiO 2 -R600a Nano-Refrigerant as Working Fluid.” 52: 733–37.

Cheng, Wen-long et al. 2010. “Heat Conduction Enhanced Shape-Stabilized Paraffin / HDPE Composite PCMs by Graphite Addition?: Preparation and Thermal Properties.” Solar Energy Materials and Solar Cells 94(10): 1636–42. http://dx.doi.org/10.1016/j.solmat.2010.05.020.

———. 2011. “A Novel Household Refrigerator with Shape-Stabilized PCM ( Phase Change Material ) Heat Storage Condensers?: An Experimental Investigation.” Energy 36(10): 5797–5804. http://dx.doi.org/10.1016/j.energy.2011.08.050.

Cheng, Wen-long, Miao Ding, Xu-dong Yuan, and Bing-chuan Han. 2017. “Analysis of Energy Saving Performance for Household Refrigerator with Thermal Storage of Condenser and Evaporator.” Energy Conversion and Management 132: 180–88. http://dx.doi.org/10.1016/j.enconman.2016.11.029.

Cheng, Wen-long, Na Liu, and Wan-fan Wu. 2012. “Studies on Thermal Properties and Thermal Control Effectiveness of a New Shape-Stabilized Phase Change Material with High Thermal Conductivity.” Applied Thermal Engineering 36: 345–52. http://dx.doi.org/10.1016/j.applthermaleng.2011.10.046.

Cheng, Wen-long, and Xu-Dong Yuan. 2013. “Numerical Analysis of a Novel Household Refrigerator with Shape-Stabilized PCM ( Phase Change Material ) Heat …” Energy 59(September 2013): 265–76.

Dhaidan, Nabeel S, J M Khodadadi, Tahseen A Al-hattab, and Saad M Al-mashat. 2013. “Experimental and Numerical Investigation of Melting of Phase Change Material / Nanoparticle Suspensions in a Square Container Subjected to a Constant Heat Flux.” International Journal of Heat and Mass Transfer 66: 672–83. http://dx.doi.org/10.1016/j.ijheatmasstransfer.2013.06.057.

Elarem, R, S Mellouli, E Abhilash, and A Jemni. 2017. “Performance Analysis of a Household Refrigerator Integrating a PCM Heat Exchanger.” Applied Thermal Engineering. http://dx.doi.org/10.1016/j.applthermaleng.2017.07.113.

Hammond, E C, and J A Evans. 2014. “ScienceDirect Application of Vacuum Insulation Panels in the Cold Chain e Analysis of Viability Application de Panneaux d ‘ Isolation Sous Vide Dans La Chaine Du Froid e Analyse de La Viabilit E.” International Journal of Refrigeration 47(0): 58–65. http://dx.doi.org/10.1016/j.ijrefrig.2014.07.010.

Islam, M R, K A Jahangeer, and K J Chua. 2015. “Experimental and Numerical Study of an Evaporatively-Cooled Condenser of Air-Conditioning Systems.” Energy. http://dx.doi.org/10.1016/j.energy.2015.05.005.

Joybari, Mahmood Mastani Hatamipour, Mahmood Sadegh, Amir Rahimi, and Fatemeh Ghadiri Modarres. 2013. “Exergy Analysis and Optimization of R600a as a Replacement of R134a in a Domestic Refrigerator System ´ Tique et Optimisation Du R600a Comme Analyse Exerge ` Ne de Remplacement Du R134a Dans Le Syste ` Me Frigorige ´ Frige ´ Rateur Domestique Frigorifique.” International Journal of Refrigeration: 2–11. http://dx.doi.org/10.1016/j.ijrefrig.2013.02.012.

Joybari, M.M, F Haghighat, J Moffat, and P Sra. 2015. “Heat and Cold Storage Using Phase Change Materials in Domestic Refrigeration Systems: The State-of-the-Art Review.” Energy & Buildings 106: 111–24. http://dx.doi.org/10.1016/j.enbuild.2015.06.016.

Kaviarasu, C, and D Prakash. 2016. “Review on Phase Change Materials with Nanoparticule in Engineering Applications.” enginnering science and technologies review 9(4): 26–36.

Mohod, Vaishali P, and Nishikant W Kale. 2015. “A Review on Heat Transfer Enhancement Using Nanoparticles Suspended With Refrigerants / Lubricating Oils in Refrigeration Systems.” 2(1): 191–94.

Oró, Eduard et al. 2014. “Energy Management and CO2 Mitigation Using Phase Change Materials (PCM) for Thermal Energy Storage (TES) in Cold Storage and Transport.” International Journal of Refrigeration. http://dx.doi.org/10.1016/j.ijrefrig.2014.03.002.

Oró, Eduard, Laia Miró, Mohammed M Farid, and Luisa F Cabeza. 2012. “Improving Thermal Performance of Freezers Using Phase Change Materials ´ Lioration de La Performance Thermique Des Conge ´ Lateurs Ame ` l ‘ Aide de Mate ´ Riaux a ` Changement de Phase a.” 35: 984–91.

Senthilkumara, A, and R Praveenb. 2015. “PERFORMANCE ANALYSIS OF A DOMESTIC REFRIGERATOR USING CUO – R600A NANO – REFRIGERANT AS WORKING FLUID.” Journal of chemical and pharmaceutical sciences (9): 30–33.

Sonnenrein, G et al. 2015. “Reducing the Power Consumption of Household Refrigerators through the Integration of Latent Heat Storage Elements in Wire-and- Tube Condensers.” International Journal of Refrigeration 51: 154–60.

Wang, Fuqiao, Graeme Maidment, John Missenden, and Robert Tozer. 2007. “The Novel Use of Phase Change Materials in Refrigeration Plant . Part 1?: Experimental Investigation.” 27: 2893–2901.

Xing, Meibo, Ruixiang Wang, and Jianlin Yu. 2014. “Application of Fullerene C60 Nano-Oil for Performance Enhancement of Domestic Refrigerator Compressors.” International Journal of Refrigeration 40: 398–403. http://dx.doi.org/10.1016/j.ijrefrig.2013.12.004.

Yuan, Xu-dong, and Wen-long Cheng. 2014. “Multi-Objective Optimization of Household Refrigerator with Novel Heat-Storage Condensers by Genetic Algorithm.” ENERGY CONVERSION AND MANAGEMENT 84: 550–61. http://dx.doi.org/10.1016/j.enconman.2014.04.086.

CompressorLeft condenserRight condenserCapillaryInsulationInsulationFrozen-food storage compartmentEvaporator Tamb
Figure 1
CompressorLeft condenser (SB4)Right condenser (SB4)CapillaryInsulationInsulationFrozen-food storage compartmentEvaporator (SB2) TambUndecane (SB1) Paraffin (SB3)
Insulation
Figure 2.a
Insulation
BC3BC2BC1,BC4 BC8BC7BC5,BC9BC6
Figure 2.b Figure 2.c
Figure 3
Figure 4
Figure 5

Figure 6
Figure 7
Figure 8
Figure 9
Figure 10
Condenser tubeSSPCMOutside wall(a)(b)
Figure 11
Figure 12
Figure 13
Figure 14
Figure 15
Figure 16
Figure 17

Figure 18
List of figures
Fig. 1: Interaction among each component of ordinary refrigerator.

Fig. 2 a: Interaction among each component of energy storage refrigerator.

Fig. 2.b: Cross section of Cold storage evaporator.

Fig. 2.c: Cross section of heat storage condenser.
Fig. 3: Grid sensitivity analysis.

Fig. 4: Validation by comparison with Wen-long Cheng et al. results ADDIN CSL_CITATION {“citationItems”:{“id”:”ITEM-1″,”itemData”:{“DOI”:”10.1016/j.enconman.2016.11.029″,”ISSN”:”0196-8904″,”author”:{“dropping-particle”:””,”family”:”Cheng”,”given”:”Wen-long”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Ding”,”given”:”Miao”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Yuan”,”given”:”Xu-dong”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Han”,”given”:”Bing-chuan”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},”container-title”:”Energy Conversion and Management”,”id”:”ITEM-1″,”issued”:{“date-parts”:”2017″},”page”:”180-188″,”publisher”:”Elsevier Ltd”,”title”:”Analysis of energy saving performance for household refrigerator with thermal storage of condenser and evaporator”,”type”:”article-journal”,”volume”:”132″},”uris”:”http://www.mendeley.com/documents/?uuid=db7457a1-5ec2-4386-81d7-0480edcc9cce”},”mendeley”:{“formattedCitation”:”(Cheng et al. 2017)”,”plainTextFormattedCitation”:”(Cheng et al. 2017)”,”previouslyFormattedCitation”:”;sup;20;/sup;”},”properties”:{“noteIndex”:0},”schema”:”https://github.com/citation-style-language/schema/raw/master/csl-citation.json”}(Cheng et al. 2017) of ordinary refrigerator.

Fig. 5: Validation by comparison with Wen-long Cheng et al. results ADDIN CSL_CITATION {“citationItems”:{“id”:”ITEM-1″,”itemData”:{“DOI”:”10.1016/j.enconman.2016.11.029″,”ISSN”:”0196-8904″,”author”:{“dropping-particle”:””,”family”:”Cheng”,”given”:”Wen-long”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Ding”,”given”:”Miao”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Yuan”,”given”:”Xu-dong”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Han”,”given”:”Bing-chuan”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},”container-title”:”Energy Conversion and Management”,”id”:”ITEM-1″,”issued”:{“date-parts”:”2017″},”page”:”180-188″,”publisher”:”Elsevier Ltd”,”title”:”Analysis of energy saving performance for household refrigerator with thermal storage of condenser and evaporator”,”type”:”article-journal”,”volume”:”132″},”uris”:”http://www.mendeley.com/documents/?uuid=db7457a1-5ec2-4386-81d7-0480edcc9cce”},”mendeley”:{“formattedCitation”:”(Cheng et al. 2017)”,”plainTextFormattedCitation”:”(Cheng et al. 2017)”,”previouslyFormattedCitation”:”;sup;20;/sup;”},”properties”:{“noteIndex”:0},”schema”:”https://github.com/citation-style-language/schema/raw/master/csl-citation.json”}(Cheng et al. 2017) of energy storage refrigerator.

Fig. 6: Effect of SSPCMs on evaporator temperature.
Fig. 7: Effect of SSPCMs on condenser temperature.
Fig. 8: Effect of SSPCMs on evaporating pressure.
Fig. 9: Effect of SSPCMs on refrigerating capacity.
Fig. 10: Effect of SSPCMs on heat leakage.
Fig. 11: Heat transfer mechanism diagram of condensers.

Fig. 12: Effect of SSPCMs on compressor power.
Fig. 13: Effect of ambient temperature on evaporator temperature of ordinary refrigerator.
Fig. 14: Effect of ambient temperature on evaporator temperature of energy storage refrigerator.

Fig. 15: Effect of R600a/TiO2 on evaporator temperature of ordinary refrigerator.

Fig. 16: Effect of R600a/CuO on evaporator temperature of energy storage refrigerator.

Fig. 17: Effect of R600a/TiO2 on evaporator temperature of ordinary refrigerator.

Fig. 18: Effect of R600a/CuO on evaporator temperature of energy storage refrigerator.

Location Main material Phase change temperature °C Effective heat capacity (kJ/ kg) Heat conductivity (W /m K) Density (kg/m3)
Evaporator
Condenser Undecane
Paraffin -26
50 100
106 1.35
1.38 750
800
Table 1: The physical parameters of SSPCMs
Nanoparticule Heat conductivity (W/m K) Density (kg/m3) Effective heat capacity (J/Kg K)
TiO2 ADDIN CSL_CITATION {“citationItems”:{“id”:”ITEM-1″,”itemData”:{“author”:{“dropping-particle”:””,”family”:”Kaviarasu”,”given”:”C”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Prakash”,”given”:”D”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},”container-title”:”enginnering science and technologies review”,”id”:”ITEM-1″,”issue”:”4″,”issued”:{“date-parts”:”2016″},”page”:”26-36″,”title”:”Review on phase change materials with nanoparticule in engineering applications”,”type”:”article-journal”,”volume”:”9″},”uris”:”http://www.mendeley.com/documents/?uuid=05966524-77cc-4570-bf41-eca54f608d29″},”mendeley”:{“formattedCitation”:”(Kaviarasu and Prakash 2016)”,”plainTextFormattedCitation”:”(Kaviarasu and Prakash 2016)”,”previouslyFormattedCitation”:”;sup;25;/sup;”},”properties”:{“noteIndex”:0},”schema”:”https://github.com/citation-style-language/schema/raw/master/csl-citation.json”}(Kaviarasu and Prakash 2016) 8,4 4157 710
CuO ADDIN CSL_CITATION {“citationItems”:{“id”:”ITEM-1″,”itemData”:{“DOI”:”10.1016/j.ijheatmasstransfer.2013.06.057″,”ISSN”:”0017-9310″,”author”:{“dropping-particle”:””,”family”:”Dhaidan”,”given”:”Nabeel S”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Khodadadi”,”given”:”J M”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Al-hattab”,”given”:”Tahseen A”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Al-mashat”,”given”:”Saad M”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},”container-title”:”International Journal of Heat and Mass Transfer”,”id”:”ITEM-1″,”issued”:{“date-parts”:”2013″},”page”:”672-683″,”publisher”:”Elsevier Ltd”,”title”:”Experimental and numerical investigation of melting of phase change material / nanoparticle suspensions in a square container subjected to a constant heat flux”,”type”:”article-journal”,”volume”:”66″},”uris”:”http://www.mendeley.com/documents/?uuid=392d140b-d314-4370-9d02-1df3811ef36c”},”mendeley”:{“formattedCitation”:”(Dhaidan et al. 2013)”,”plainTextFormattedCitation”:”(Dhaidan et al. 2013)”,”previouslyFormattedCitation”:”;sup;23;/sup;”},”properties”:{“noteIndex”:0},”schema”:”https://github.com/citation-style-language/schema/raw/master/csl-citation.json”}(Dhaidan et al. 2013) 18 6350 535
Table 2: The physical parameters of nanoparticles
Cycle time (min) ON-time (min) OFF-time (min) OFF- time to ON- time ratio
Ordinary 60 21,8 38,2 1,75
Energy storage 230,5 45,3 185,185 4,08
Table 3: The comparison of two refrigerators’ cycle time
Electrical consumption (KWh) COP Energy saving
Ordinary 0,659 1,16 –
Energy storage 0,445 1,38 32%
Table 4: The comparison of two refrigerators’ electrical consumption and COP
Ambient temperature (°C) Complete cycle time (min) ON-time of a cycle (min) OFF-time of a cycle (min)
15 40 14,5 25,5
20 43,3 15,5 28
25 60 21,8 38,2
30 60 60 0
35 60 60 0
40 60 60 0
Table 5: Complete cycle time, ON-time and OFF-time of a cycle of ordinary
refrigerator in different ambient temperature
Ambient temperature (°C) Heat leakage (W) ON-time of a cycle (min) OFF-time of a cycle (min) OFF- time to ON- time ratio
15 10,75 45,3 232,5 5,13
20 12,12 45,3 206 4,54
25 13,5 45,3 185,185 4,08
30 14 ,63 45,3 170 3,75
35 15,7 45,3 160 3,53
40 17,13 45,3 146 3,22
Table 6: OFF-time to ON-time ratio of energy storage refrigerator in different ambient temperature
Mass of TiO2 (g) Mass fraction of R600a/TiO2 On-time of a cycle (min) On-time reduction
0 0 21,8 0.1 0,0014 21,8 0%
0.5 0,0069 21,8 0%
1 0,014 18,3 16%
2 0,027 18,3 16%
5 0,065 6 72%
Table 7: On-time reduction of ordinary refrigerator using different mass fraction
of R600a/TiO2.

Mass of CuO (g) Mass fraction  of R600a/CuO On-time of a cycle (min) On-time reduction
0 0 21,8 0.1 0,0014 21,8 0%
0.5 0,0069 21,8 0%
1 0,014 16,33 25%
2 0,027 11,05 49%
5 0,065 2,86 86%
Table 8: On-time reduction of ordinary refrigerator using different mass fraction of R600a/CuO
Mass of TiO2 (g) Mass fraction of R600a/TiO2 On-time of a cycle (min) On-time reduction
0 0 45,3 0.1 0,0014 45,3 0%
0.5 0,0069 45,3 0%
1 0,014 30,61 32%
2 0,027 30,61 32%
5 0,065 32,45 28%
Table 9: On-time reduction of energy storage refrigerator using different mass fraction
of R600a/TiO2
Mass of CuO (g) mass fraction C R600a/CuO On-time of a cycle On-time reduction
0 0 45,3 0.1 0,0014 45,3 0%
0.5 0,0069 30,61 32%
1 0,014 30,61 32%
2 0,027 32 29%
5 0,065 32 29%
Table 10: On-time reduction of energy storage refrigerator using different mass fraction of R600a/CuO
H I G H L I G H T S
-A numerical study was carried out on a domestic refrigerator with SSPCMs heat exchangers.

-The electrical consumption saving of the energy storage refrigerator with SSPCMs can achieve 32%.

-The effects of nano-refrigerants on the temperature and operation time of the compressor are studied.

– The electrical consumption saving of the energy storage refrigerator using nano-refrigerants as working fluid can achieve 64%.