Cooling Performance Enhancement of a 20 RT (70 kW) Two-Evaporator Heat Pump with a Vapor-Liquid Separator

20 RT (70 kW) two-evaporator heat pump system was developed, manufactured, and tested to enhance the cooling performance using a vapor-liquid separator. In the proposed system, two evaporators are connected in series, and the refrigerant passing through the primary evaporator is separated into vapor and liquid using a vapor-liquid separator. The vapor refrigerant is passed to the compressor, whereas the liquid phase flows into the second evaporator. The amount of vapor refrigerant sent to the compressor can be adjusted through a needle valve opening (0%, 50%, and 100%). The influence of this parameter on the cooling performance was analyzed. The cooling performance tests were repeated five times to check repeatability. Data associated with the air and refrigerant sides were obtained, and the average coefficients of performance (COPs) were calculated. The average COP associated with the air side was approximately 5% lower than that pertaining to the refrigerant side owing to the heat loss. In terms of the air-side cooling performance, the average COP was 3.14, 3.40, and 3.68 when the valve openings were 0%, 50%, and 100%, respectively. The cooling performance when the valve opening was 100% was 17.2% higher than that for the valve opening of 0%. The findings demonstrated that the cooling performance of a heat pump can be enhanced using two evaporators and a vapor-liquid separator.