An Experimental Study On The Performance Of A Heat Pump System Based On A Two-stage Casing Series Condenser

Under the dual pressure of energy and environmental problems,the HVAC industry as the key energy consuming part in the field of building energy consumption is developing various new energy technologies.As a result,heat pump technology has developed rapidly.At present,the research on heat pump system mainly focuses on three aspects:the research of working medium,the performance improvement of compressor and the performance improvement of important parts.In this article,taking the condenser in the heat pump system as the research target,the performance of the two-stage tandem annular tubes condenser in the heat pump operating condition is numerically simulated,and its flow and heat transfer characteristics are analyzed.The main research contents are as follows:(1)The heat exchanger models of single tube and three tube two-stage tandem annular tubes condenser are established,.At the same time,the heat transfer process of single-tube and triple-tube condensers is calculated and analyzed under the same working condition.The heat transfer coefficient in the first casing is basically the same,but in the middle section and the second casing,the heat transfer coefficient of the three-tube structure is higher than that of the single-tube structure.At the same time,at the inlet偶of the second casing,the heat transfer coefficient of the three-tube structure is 6611.65W/(m~2·k),which is 6.34%higher than that of the single-tube structure.(2)The pressure drop of the single pipe structure and the three pipe structure is basically the same in the first casing,but the pressure drop of the single pipe structure is smaller than that of the three pipe structure from the middle pipe section.At the exit,the pressure drop of the three-tube structure was 6898.23Pa,which was 4.08%higher than that of the single-tube structure.Although the pressure drop is increased to a certain extent,the compact three tube structure can make up for the shortage of the tube heat exchanger.(3)At the same time,a two-stage tandem annular tubes heat pump system was built,and the system cycle operation characteristics under different working conditions were analyzed by using pure working medium R32 as the operating medium.The results show that when the inlet temperature of the heat sink is 10℃and the outlet temperature is 40℃,the COP of the heat pump system is 2.98.Under the same inlet temperature of the heat sink,when the temperature of the heat sink water is 45℃,50℃and55℃,the COP of the system’s heating performance coefficient decreases by1.89%,8.09%and 17.79%respectively.Under the same heat transfer water temperature,when the heat transfer water inlet temperature is 15℃and20℃,the COP of system heating performance coefficient decreases by3.36%and 9.06%respectively.(4)With the increasing of the outlet temperature of the heat sink,the condensing pressure of the heat pump system under three different inlet temperatures presents an increasing trend.At the same time,when the temperature of heat transfer water is the same,the condensation pressure shows a trend of increasing with the increasing inlet temperature.When the outlet water temperature is 55℃,the inlet water temperature is 10℃and the condensation pressure at 15℃is 8.72%and 6.12%lower than that at20℃.When the inlet temperature is 20℃,the condensation pressure is reduced by 10.28%,7.70%and 5.55%when the outlet temperature is 40℃,45℃and 50℃respectively.(5)with the continuous increase of the outlet temperature of the heat sink,the exhaust temperature of the heat pump system with three different inlet temperatures shows a trend of increasing.At the same time,when the temperature of heat discharge water is the same,the exhaust temperature shows a trend of increasing with the increasing inlet temperature.When the water outlet temperature is 55℃,the inlet temperature is 10℃and the exhaust temperature at 15℃drops by 10.31%and 6.52%compared with that at 20℃.When the inlet temperature is 20℃,the exhaust temperature of the heat pump system is reduced by 8.89%,6.71%and 2.31%when the outlet temperature is 40℃,45℃and 50℃respectively.