Modeling and effects of air temperature and humidity on vapor compression refrigeration system energy performance

Indoor air temperature and humidity control are the main tasks of the air conditioning system for keeping the indoor thermal comfort and consume considerable energy. It is essential to have a thorough comprehension of heat and mass transfer process of air temperature and humidity in vapor compression refrigerant system. Therefor the effects of air temperature and humidity on vapor compression refrigeration system energy performance is investigated in this paper. Model of VCR system is developed to predict the system energy consumption and COP. Collected operation data from a lab-scale VCR testing platform are used to verified the proposed model in prediction the outlet air temperature, relative humidity and system energy consumption with the relative errors less than 6%. Furthermore, the effects of compressor rotation speed on system energy consumption and COP are analyzed under different air temperature and relative humidity. Simulation results show that both the ambient air relative humidity and temperature have significant impacts on energy consumption and COP of VCR cycle system. In the process that the ambient air temperature increases from 36°C to 45°C, the VCR system energy consumption will increase by 18.6% and COP decreases by 17.3%. On the other hand, the system energy consumption will increase by 26.3% and the COP will decrease by 18% when the outdoor air relative humidity is rising from 60% to 90%. Therefore, both air temperature and humidity have the considerable influences on the VCR energy efficiency and should be seriously paid attention to when optimization the VCR system.