Frost Formation and Defrost Methods of Electric Vehicle Heat Pump Air Conditioning System

doi:10.3969/j.issn.1000-1093.2017.01.022

Abstract

Abstract: Heat exchanger frosting deteriorates the heat performance of electrical vehicle heat pump air conditioning system ( HPACS ) in winter. Specially designed micro-channel heat exchangers are applied to electrical vehicle HPACS here. The system is tested at different surrounding air temperature, different surrounding air relative humidity and different air flow rate. Frost area proportion and frosting rate of outdoor heat exchanger are monitored and analyzed to understand different factors that could influence frosting performance of HPACS. The results show that the increase in air relative humidity, and the decrease in ambient temperature and air flow rate lead to quick frosting and bigger frost area proportion. The relationships between dynamic coefficient of performance (COP) and frosting rate are observed in detail. It reveals that frosting rate keeps the same change tendency to COP. At the period of frost beginning to form, COP and frosting rate increase at almost the same time, and as frosting rate curve start to drop, COP curve also drop at the same time. This phenomenon has been validated at different conditions. It is considered as the switch point of defrosting when the frosting sharply drops and the frost area proportion reaches to 30%. On the other hand, the frost area proportion calculated from binary image of frosting is taken as switch point of defrosting finish. When sharp drop of frosting rate and frost area proportion of 30% are detected, HPACS starts to defrost; when frost area proportion is reduced to same value as non-frosting’s, HPACS stops defrosting. The defrosting control strategy may save defrosting energy and improve the heating performance of electrical vehicle HPACS. Key

Key words: engineeringthermophysics, electricalvehicle, heatpumpairconditioning, COP, frostingrate, frostareaproportion

CLC Number:

LIANG Zhi-hao, WU Jiang-hong, JIN Peng, LI Hui-xi. Frost Formation and Defrost Methods of Electric Vehicle Heat Pump Air Conditioning System[J]. Acta Armamentarii, 2017, 38(1): 168-176.

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第38卷
第1期2017 年1月兵工学报ACTA
ARMAMENTARIIVol.38No.1Jan.2017

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