Performance of a CO2 water to water heat pump with less charge: Inlet temperature effects

A CO₂ water to water heat pump system was used to investigate the effects of cooling and chilling water inlet temperature at reduced charge capacity (approximately 75% of the full charge). The temperature were adjusted between 10 °C to 30 °C in nine steps while the throttle valve opening adjusted between 100%, 50% and 25%. It was observed that the as the cooling water inlet temperature increased, the heat output and general performance of the system diminished but as the chilling water temperature increased, there was an improvement of the system performance. Therefore, the best temperature combination was cooling - chilling water temperature of 10 °C - 30 °C. The opposite, i.e. cooling - chilling water temperature of 30 °C - 10 °C was the worst. Nevertheless, the effects of the cooling water temperature were higher on the system performance than the effect of the chilling water temperature. These observations were true in all throttle valve settings, where, the smaller the throttle valve opening, the higher the performance.