A novel, near-counterflow gas cooler for CO₂ air-conditioning systems was presented and modeled in this study. This configuration, which uses microchannel tubes and multilouver fins, is ideally suited for the nonisothermal heat transfer in CO₂ gas coolers. The model uses heat exchanger geometry and inlet conditions as the inputs to predict the overall duty as well as temperature profiles of the refrigerant and air. The effects of design conditions, such as air and CO₂ mass flow rates, and geometric parameters on heat transfer rates and pressure drops can be investigated using this model. The study demonstrated that a gas cooler heat load of 6.97 kW, typical of an automotive air-conditioning system, can be transferred in very small envelope (0.546 m x 0.408 m x 19 mm) due to the use of the counterflow, serpentine tube-side flow configuration. Small approach temperature differences (5.33°C) were also demonstrated. The study also provided, through detailed refrigerant and air temperature profiles, preliminary indications that conductive heat transfer in the heat exchanger tube walls and fins may play a role in determining the overall heat duty.

Units: Dual