Study On The Performance Of Direct Expansion Solar Assisted Heat Pump Water Heater

Solar-assisted heat pump water heater has the advantages of high efficiency and energy saving,and has good development prospects.The experiment in this paper is to conduct a performance study on a ready-made direct-expansion solar heat pump water heater.The purpose of this experiment is to understand the operating conditions and working performance of the solar heat pump water heater,establish a mathematical model of the solar heat pump system and analyze its performance.The research method is to measure the temperature of each point,the pressure before and after the throttle valve,the flow of the working fluid,the power consumption of the water heater and the solar radiation value to help analyze the performance of the running process.This paper focuses on several factors affecting the performance of solar heat pump water heaters,including the effects of different dip angles of collectors;the effects of different weather conditions;the influence of ambient temperature;the different coefficient of performances under nighttime and daytime operating conditions.This paper proposes optimization opinions for different influencing factors.After analyzing and processing the experimental data,the following conclusions were obtained:The choice of the optimal inclination of the collector should be considered as follows:to obtain the maximum solar energy for one year,the local latitude value should be used as the collector inclination;to obtain the maximum solar energy in the summer,the collector installation angle should be used as the median value of the minimum optimum inclination angle and the local latitude value;to obtain the maximum solar energy in winter,the collector installation angle should be used as the median value of the local latitude value and the maximum optimum inclination angle.Under sunny conditions,the solar radiation intensity is large at noon time,and it is best to run the heat pump water heater during this time.When the average irradiation value is the same,the solar heat pump water heater works better on a rainy day than on a cloudy day.The hot water obtained at night can meet the demand for use,and the ratio of collector area to tank volume is 12:1(m2/m3),which is reasonable and efficient.It has reference value for heat pump water heater selection design..When the heat pump water heater is running at night and the solar radiation intensity is weak during the day,the influence of the ambient temperature on the heat pump water heater will be relatively large.Reducing the increase of evaporation pressure and the reduction of condensing pressure are beneficial to the stable operation of water heaters.