This study investigated the performance of a single-stage scroll compressed air source heat pump coupled with a flash tank indirect vapor injection. In the refrigerant circulating piping of the heat pump, an indirect vapor injection piping connecting a flash tank at the refrigerant outlet of a condenser and the suction of a scroll compressor was designed. By the indirect refrigerant vapor injection from the flash tank, the saturation pressure and temperature of the refrigerant (R134a) in the evaporator can be raised and the sub-cooling of the refrigerant at the inlet of expansion valve can be enlarged as well. Thus, energy consumption of the compressor can be reduced and cooling capacity of the evaporator can be boosted. It was found that the suitable amount of indirect vapor refrigerant strongly depends on the operational environmental temperatures. By adjusting the suitable indirect vapor injection volume into the compressor, the performance of the heat pump was enhanced. In this study, a suitable indirect vapor injection volume was found and 5~15% performance increments can be obtained while the heat pump operated under ambient temperatures in a range from 5°C to 35°C.
This study developed a heat recovery air conditioner to supply on-demand air conditioning and reclaim waste heat during operation. In addition to the conventional refrigerant pipe, a plate heat exchanger was designed and connected in parallel to the condenser and evaporator. While refrigerant with high pressure and high temperature flows through the plate heat exchanger, the refrigerant flow is cooled down and condensed by cooling water from a water tank, and condensation heat in the exchanger is absorbed by the cooling water and stored in the water tank. In this study, solenoid valves were installed in the pipe to regulate the refrigerant volume in parallel connected pipes based on the tank water temperature by duty control logic. This multi-function heat recovery air conditioner has various operation modes. In summer, the air conditioner not only provides on-demand cooled air to air-conditioned rooms but also reclaims waste condensation heat through the plate heat exchanger. In winter, the air conditioner supplies on-demand heated air to indoor spaces and heats the water tank by simultaneously reclaiming waste condensation heat. According to an experimental operation test, the value of average water heating efficiency (COP h) of this air conditioner can reach 3.77 in the summer operating mode and 1.91 in the winter operating mode.
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