| Air-source heat pump water heater is becoming popular in the water heater market because of the characteristics of energy conservation and environmental protection, safety and high efficiency.By reason of the restriction of refrigerant and condensing pressure, hot water temperature of heat pump water heater is nearly 60?, which is restricted to get further promotion and application for some special industries requiring moderate and high temperature hot water more than70 ?. This paper was aimed at a 5-horsepower air-source heat pump water heater to carry out performance test and simulation study of a air-source moderate and high temperature heat pump water heater.(1) Based on the theoretical cycle performance computation of the zeotropic refrigerant mixtures composed of R22 and R142 b under different mass ratios, experimental system was set up to research on the performance change rules under different environment temperature,including maximum attainable water temperature within safe compressor exhaust pressure, and the effect laws of the heating capacity, input power,COP, exhaust pressure and temperature of the compressor underdifferent refrigerant charge. The results showed that when the compressor exhaust pressure was set to 2.8MPa and the unit didn't work,the temperature of attainable hot water charging R22 and R142 b at different mass ratios ranged from 64?to 91?, and it met requirement for moderate and high temperature hot water; the refrigerant charge had a little effect on the heating capacity, input power and COP, but a marked impact on the suction and exhaust temperature, compression ratio, and the optimal charge of the water heater was almost 2.3kg so as to enable the system to operate safely and steadily.(2) The designed small diameter tubes of heat exchanger was to match the heat pump system and accomplish the optimization for the important component of heat pump by virtue of CFD software simulation to study the property of heat transfer and pressure drop of flat finned evaporator and analyze the influence of pipe diameter and air speed on the heat exchange capacity and frictional drag. The simulated result indicated that with the increasing air speed and more smaller tube diameter the heat exchange capacity and frictional drag both increased,but the indicator to evaluate performance of heat exchanger decreased gradually. It was suggested that the evaporator with refrigerant pipe diameter of 7mm should be adopted relatively, and the air velocity flowing into the finned heat exchanger be not more than 3m/s. |
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