Optimization Design Of Air-source Carbon Dioxide Heat Pump Water Heater

With its continuous development, air source carbon dioxide heat pump water heater is gradually gaining application ground in China. According to GB/T21362-2008specified test conditions, effects of the charging amount of water mass flow rate, the outlet water temperature and other factors from the refrigerant on the heat pump performance were investigated. The results showed that:There is an optimum amount of filling in the CO2heat pump water heating system. If the filling is too small, the refrigerant flow rate through the compressor and the evaporator is small, resulting in a waste of equipment, thus the water temperature is too low. Over loading could get a large operation pressure that causes the reduction of system COP. The optimal amount of CO2charge is8MPa in this paper.The impact of water quality on the COP and outlet water flow is opposite. Increasing water mass flow will increase COP, and reduce the outlet water temperature. The determination of suitable water flow rate should take both the system COP and hot water requirements in consideration.Based on the experimental results, exergy analysis of CO2air source heat pump water heaters was conducted, and the compressors and other system components exergy analysis models were set up to calculate the exergy efficiency of the various components of the exergy losses and systems. The calculation indicated that exergy efficiency of the system is only27.7%that was quite low. The compressor exergy losses contributed most in the system exergy lose, and it was followed by the throttle, the gas cooler, and the evaporator.Therefore, in this paper, a carbon dioxide injector was designed and used in air-source heat pump water heater. A detailed introduction of injector design methods for jet coefficient ejector structure sizes was presented. Visual Basic was used for ejector design calculations programming, and the maximum injection coefficient can be achieved through the calculation of the ejector was0.7.In order to study the internal injector flow process, numerical simulation methods were used. Using the obtained mass flow rate at the inlet, the error injection coefficient can be calculated with the theoretical calculation of11.4%. In addition, the infection of the speed and pressure were analyzed.