{"title":"Experimental study on defrosting multi outdoor units in turn for air source heat pump using hot gas","authors":"Xiang Li, Guoyuan Ma, Tianyu Lu, Lei Gao, Weilai Rong, Yuexuan Gong, Shuxue Xu","doi":"10.1016/j.ijrefrig.2025.03.007","DOIUrl":null,"url":null,"abstract":"<div><div>To improve the efficiency of air source heat pumps and eliminate the performance degradation caused by frost in winter, a hot gas bypass defrosting experimental platform was built and the hot gas bypass defrosting experiment under different outdoor temperature and different opening degree of hot gas bypass valve were carried out. The results showed that the defrosting of the heat pump evaporator can be completed well by adopting the hot gas bypass defrosting method without interrupting the heat pump heating. At outdoor temperatures of -10 °C, -5 °C and 0 °C, the most appropriate time for heat pump to activate hot gas bypass defrosting were 30 min, 40 min and 50 min, respectively. The corresponding peak value of average heating capacity were 7.96 kW, 10.16 kW, and 12.08 kW, and the heating <em>COP<sub>C</sub></em> values were 3.03, 3.56, and 4.19, respectively. The increase of bypass exhaust volume would shorten the defrosting time but also reduce the heating capacity of the heat pump during the defrosting process. Hence the optimum defrosting start time of the system is different with different bypass valve opening. For the system built by this paper, the 20 % bypass valve opening had the best performance in defrosting, and the optimal defrosting start time was 40 min, during which the average heating capacity and <em>COP<sub>C</sub></em> achieved peak values of 10.16 kW and 3.56, respectively. These results provide a reference for the defrosting design of air source heat pumps.</div></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":"174 ","pages":"Pages 76-85"},"PeriodicalIF":3.5000,"publicationDate":"2025-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"International Journal of Refrigeration-revue Internationale Du Froid","FirstCategoryId":"5","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0140700725000970","RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"ENGINEERING, MECHANICAL","Score":null,"Total":0}
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Abstract
To improve the efficiency of air source heat pumps and eliminate the performance degradation caused by frost in winter, a hot gas bypass defrosting experimental platform was built and the hot gas bypass defrosting experiment under different outdoor temperature and different opening degree of hot gas bypass valve were carried out. The results showed that the defrosting of the heat pump evaporator can be completed well by adopting the hot gas bypass defrosting method without interrupting the heat pump heating. At outdoor temperatures of -10 °C, -5 °C and 0 °C, the most appropriate time for heat pump to activate hot gas bypass defrosting were 30 min, 40 min and 50 min, respectively. The corresponding peak value of average heating capacity were 7.96 kW, 10.16 kW, and 12.08 kW, and the heating COPC values were 3.03, 3.56, and 4.19, respectively. The increase of bypass exhaust volume would shorten the defrosting time but also reduce the heating capacity of the heat pump during the defrosting process. Hence the optimum defrosting start time of the system is different with different bypass valve opening. For the system built by this paper, the 20 % bypass valve opening had the best performance in defrosting, and the optimal defrosting start time was 40 min, during which the average heating capacity and COPC achieved peak values of 10.16 kW and 3.56, respectively. These results provide a reference for the defrosting design of air source heat pumps.
期刊介绍：
The International Journal of Refrigeration is published for the International Institute of Refrigeration (IIR) by Elsevier. It is essential reading for all those wishing to keep abreast of research and industrial news in refrigeration, air conditioning and associated fields. This is particularly important in these times of rapid introduction of alternative refrigerants and the emergence of new technology. The journal has published special issues on alternative refrigerants and novel topics in the field of boiling, condensation, heat pumps, food refrigeration, carbon dioxide, ammonia, hydrocarbons, magnetic refrigeration at room temperature, sorptive cooling, phase change materials and slurries, ejector technology, compressors, and solar cooling.
As well as original research papers the International Journal of Refrigeration also includes review articles, papers presented at IIR conferences, short reports and letters describing preliminary results and experimental details, and letters to the Editor on recent areas of discussion and controversy. Other features include forthcoming events, conference reports and book reviews.
Papers are published in either English or French with the IIR news section in both languages.
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