Performance Research Of A Heat Pump Water Heater With The Hybrid Resources

Based on the use of available energy and the protection of environment, a hybrid heat source heat pump water heater was put forward, considering the use of solar/air energy and natural refrigerant Through simulation research and experiments, heating capability, power consumption and heating rate and so on were studied in the hybrid heat source CO₂ heat pump water heater. Specific research contents and conclusions are as follows:（1） In order to obtain operating characteristics of CO₂ transcritical cycle and the advantages of the hybrid heat source, the refrigerant and heat modes were compared, respectively in this chapter. On the one hand, mathematical and physical models of heat pump hot water system of CO₂, R134a and R22 were established. The accuracy of the model was verified by the experimental data of the hybrid heat pump water heater of R22 in the literature. Then the operating characteristics of hybrid heat source heat pump water heater of CO₂, R134a and R22 were analyzed, heating performance of three refrigerants, solar absorption rate, circulating heating time and the suction and exhaust temperature/pressure of different ambient temperatures were compared. It can be concluded that heating performance at ambient temperatures below 13℃ of CO₂ was better than R134a and R22; in addition, under different conditions, CO₂ heating period was more than R22 and less than R134a, suction and discharge pressure of CO₂ was higher than the ones of R22 and R134a. On the other hand, the simulation model of the composite source heat pump water heater was compared with single air source heat pump hot water system. The simulation results show that the hybrid heat source water heater was higher about 20% than a single air source heat system in some typical conditions. So, the use of hybrid heat sources of CO₂ heat pump hot water system has a unique environmental advantages, low temperature strength and performance advantages.（2） In order to analyze the operating characteristics and influencing parameters of hybrid heat source CO₂ heat pump water heater system in typical operating conditions. Physical and mathematical models of CO₂ heat pump water heater were established. At the same time, simulation program of the CO₂ heat pump water heater system was written, The system performance in different seasons especially in the low-temperature environment were studied, and from the point of view that the cooling pressure, ambient temperature, solar radiation intensity, the gas cooler structure parameters, collector/evaporator structure parameters, operating pressures and gas cooler outlet temperature and so on to analyze the operating characteristics. The simulation results show that the COP of hybrid heat source system can be higher than 3.0 in different seasons, especially in the environmental temperature was only 0℃; and obtain the trends of environmental parameters and structural parameters of the system to the system performance. This can provide guidance to optimize the design and operation of the system.（3） In order to obtain the heat-absorbing performance of self-designed solar collector/evaporator and operating characteristics of and system, related equipments of hybrid heat sources systems were selected and produced, then an experimental platform system were built By experimental, operating characteristics and the change trends of the ratio of solar energy absorbed in the collector/evaporator were studied. The results showed that, the system can take full advantage of solar energy when there were continuous strong solar radiation, the system average COP was to 3.77; when the solar radiation instability, ratio of refrigerant absorbs solar energy also can up to 92%, with an average COP of 3.48. Under the same environmental conditions, experimental values were compared with simulation data. Simulation data can provide evidence for further study.