high temperature heat pump, gas injection, economizer
Gas injection technology is often used in cold regions to solve heat pump’s low heating capacity and high discharge temperature at low ambient temperature. Injecting gas into port opened at specific position of compressor could increase mass flow rate of compressor and total heating capacity of heat pump. Gas injection also changes compression ratio of compressor and decreases discharge temperature. An optimal gas injection pressure is got when the coefficient of performance reached to peak value at a certain working condition. It’s a feasible way to increase performance of heat pump at cold regions. High temperature heat pump could provide higher temperature water for industrial usage regions but there still existed some problems on its usage. Total heating capacity decreased and discharge temperature increased with the raise of condensation temperature. Refrigerant temperature before throttling valve was high and may exceed working temperature range of electrical expansion valve. Gas injection technology with an economizer was adopted to solve these problems. A new high temperature heat pump cycle was designed based on gas injection and outlets water temperature of the prototype manufactured was reached to 90?. Temperature before throttling valve was well controlled by the usage of economizer. Heating capacity, discharge temperature, compressor power consumption of the heat pump system at different amount of injected gas was conducted by theoretical and experimental research in this paper. This study showed the function of gas injection technology which used in high temperature heat pump.