Experimental Study On Operation Characteristics Of Commercial Air Source Heat Pump Unit

With the rapid development of China's economy and science,the use of energy and the aggravation of environmental pollution are inevitable.As an energy-saving,efficient,adaptable and widely used refrigeration and heating device,air source heat pump is more and more in line with the development needs of the era.In the low and high temperature environment,air source heat pump will have the problems of low efficiency,poor effect and high exhaust temperature,which greatly limits the application of air source heat pump products.Based on the theory of quasi-two-stage compression,the air-cooled heat pump chiller with R410 a as refrigerant was theoretically analyzed and experimentally tested by means of medium-pressure gas-supply enthalpy-increasing measures.The results are as follows:(1)Under the refrigeration condition of ambient temperature from 21? to 50 ?,the refrigeration capacity and EER of the system decrease with the increase of ambient temperature,while the exhaust temperature and exhaust pressure increase with the increase of ambient temperature.Compared with the standard operating condition,the refrigeration capacity and EER decrease by 26.55% and 37.80% respectively,and the exhaust temperature and exhaust pressure increase by 33.69% and 26.44%,respectively.(2)Middle-pressure vapor injection can reduce the exhaust temperature and increase the refrigeration capacity of the system.When refrigerated at high temperature at 50 ?,compared with ordinary system without vapor injection,the exhaust temperature can be reduced from 111.90? to 106.23? by Middle-pressure vapor injection.At the same time,the refrigeration capacity can be increased by 13.50%.(3)Enhanced middle-pressure vapor injection can also enhance the system calorific and heating COP.Compared with ordinary system without vapor injection,the medium-pressure vapor injection can raise the system calorific value from 11.89% to 19.44% and the heating COP from 1.12% to 8.56% in the ambient temperature range-15? to 7?.(4)Experiments on variable compressor frequency and fan speed are carried out.It is found that when compressor frequency is 55 Hz,the refrigeration coefficient EER reaches the maximum value of 2.69,and when compressor frequency is 60 Hz,the heating COP reaches the maximum value of 2.81.When fan speed varies in the range 400r/min to 600r/min,the variation range of refrigeration performance parameters is larger than that in the range of high speed.When heating,the variation of system performance parameters with fan speed is small.