Study of New Mini-Channel Trans-Critical CO(2) Heat Pump Gas Cooler

A gas cooler is one of the important parts of a carbon dioxide (CO(2)) heat pump water heater, and it must meet the needs of not only pressurization but also heat transfer. It is important to study gas coolers. In this paper, a heat exchanger with a spiral channel is studied. ANSYS CFX software was used to analyze the flow and heat transfer characteristics of the heat exchanger (single-plate model). The influences of the cooling pressure of CO(2), the mass flux of CO(2), the mass flux of water and the channel radius of CO(2) are discussed. In this paper, the results show that the cooling pressure of CO(2), the mass flux of CO(2) and the channel radius of CO(2) all have a large influence on the local heat transfer coefficient: with an increase in the cooling pressure of CO(2), the peak value of the heat transfer coefficient of CO(2) decreases and the average heat transfer coefficient decreases; with an increase in the mass flux of CO(2), the peak value of the heat transfer coefficient of CO(2) increases and the average heat transfer coefficient increases; and with a decrease in the channel radius of CO(2), the peak value of the heat transfer coefficient of CO(2) increases. The water mass flux has only a slight effect on heat transfer, and the lower cooling pressure of CO(2) corresponds to a higher peak heat transfer coefficient, which can reach 27.5 kW∙m(−2)∙K(−1) at 9 MPa.