Experimental Study to Evaluate Effect of Source Temperature on COP and Compressor Status in Water-to Heat Pumps

Abstract

Heat pump devices have been researched and analyzed from different aspects, which indicates the importance of these devices. In fact, these devices transfer heat energy effectively from one source to another by consuming power. In this work, the importance of source temperature and its effect on system performance and compressor status has been investigated. It is shown that if the temperature of the heat source is low, the refrigerant at the inlet of the compressor will be in the two-phase region, which could cause damage to the compressor. In these cases, the evaporator design can be changed as available solutions or a high-temperature heat source can be provided in the present study. On the other hand, in the two-phase region, calculating the work of the compressor with enthalpy values will be a problem and may cause a computational error in the power consumption of the compressor. The reason for this is that the enthalpy of refrigerant in the compressor cannot be obtained with two properties, i.e., temperature and pressure. This issue has been considered and the rate of computational error has been obtained. R134a refrigerant was used as circulating gas in the used water-to-air heat pump. The results obtained in the experiments performed showed that the COP value of the heat pump increased by 172% when the source temperature increased from 6 degrees C to 34 degrees C. As the source temperature increases, more energy is transferred to the system. This issue raises both high-pressure and low-pressure values. This increase was recorded as 34% for high pressure and 17% for low pressure when the source temperature increased from 6 degrees C to 34 degrees C.