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Experimental analysis of an air-source transcritical CO2 heat pump water heater using the hot gas bypass defrosting method

Citation

Hu, B and Wang, X and Cao, F and He, Z and Xing, Z, Experimental analysis of an air-source transcritical CO2 heat pump water heater using the hot gas bypass defrosting method, Applied Thermal Engineering, 71, (1) pp. 528-535. ISSN 1359-4311 (2014) [Refereed Article]

Copyright Statement

Copyright 2014 Elsevier

DOI: doi:10.1016/j.applthermaleng.2014.07.017

Abstract

When an air-source CO2 heat pump water heater operates at low ambient temperatures in cold regions in winter, frost can form on the coil surface of its outdoor evaporator. The frost substantially affects the operating performance and energy efficiency of CO2 heat pump water heaters and hence periodic defrosting is essential. In this paper, defrosting characteristics of an air-source CO2 heat pump water heater using the hot gas bypass defrosting method is experimentally studied at different ambient conditions. An experimental setup is developed for this purpose and experimental procedures are detailed. Thereafter, the pressure and temperature in the outdoor evaporator, at the compressor and gas cooler outlets are evaluated during the defrosting period. An energy analysis is then performed of different system components during the defrosting process. Results indicate that 35% of the supplied energy is used for melting the frost, and 7.6% is used to heat the evaporator tubes and fins. About 57.4% of the supplied energy is consumed to increase the internal energy of the gas cooler. The typical efficiency of the hot gas bypass defrosting method applied in the CO2 heat pump water heater ranges from 30 to 40%. It increases with increasing dry bulb temperature, and decreasing relative humidity.

Item Details

Item Type:Refereed Article
Keywords:CO2 heat pump, hot gas bypass, defrost, energy consumption
Research Division:Engineering
Research Group:Mechanical Engineering
Research Field:Energy Generation, Conversion and Storage Engineering
Objective Division:Energy
Objective Group:Energy Conservation and Efficiency
Objective Field:Energy Conservation and Efficiency not elsewhere classified
Author:Wang, X (Associate Professor Xiaolin Wang)
ID Code:93358
Year Published:2014
Web of Science® Times Cited:11
Deposited By:Engineering
Deposited On:2014-07-29
Last Modified:2017-11-06
Downloads:0

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