Characteristics and performance of a CO2 trans-critical water to water heat pump

In order to make CO₂ as a preferred refrigerant, its efficiency of operation and/or heat output values should be higher than those achieved by convectional systems. It is in this context that this study was conducted. A CO₂ trans-critical water to water test bed was used to study the output of the heat pump. In a bid to improve the output of this system, the effect of throttle valve opening and water flow rates were investigated by adjusting them relevantly. The output of the system was in terms of the components energies and system efficiencies. It was observed that as the throttle valve opening is reduced, the performance increased until around 20% opening where the performance started to reduce. Also, the higher the flow rate, the better the performance.