Simulation and performance evaluation of finned-tube CO2 gas coolers for refrigeration systems

This paper describes a detailed mathematical model and its application for air-cooled finned-tube CO2 gas coolers. The model has been developed utilizing a distributed method which is necessary to predict accurately the great variation of both refrigerant thermophysical properties and local heat transfer coefficients during CO2 gas cooling processes. The modelling method also enables performance analyses with different circuit arrangements and changed structure parameters in gas coolers to be assessed. The model has been validated with the test results from a published literature by comparing the gas temperature profiles along the coil pipes from refrigerant inlet to outlet at different operating states. With the aim of increasing the heat capacity or minimizing the approach temperature for a gas cooler, the validated model is used to carry out performance simulation and analysis when the circuit arrangement of the original heat exchanger is redesigned. It is found that the approach temperature and the heat capacity are both improved with the increase of heat exchanger circuit numbers.