A new moving-boundary algorithm to predict heat transfer rate of counter-flow water-cooled transcritical CO2 gas cooler

Abstract

A new moving-boundary model was proposed for predicting steady-state heat transfer rate of water-cooled transcritical CO2 gas cooler. The new model aims to separate the CO2 gas cooler into up to three zones depending on the local thermal capacitance rate, which is significantly different from the moving-boundary models used in subcritical region, which is based on fluid phase. The experimental data from the literature were used for model validation, and the results show that the prediction accuracy of the new moving-boundary model is comparable to that of the finite volume method. The deviations between predicted and measured heating capacities are within ±5%, and the predicted CO2 outlet temperatures are within ±4°C. The averaged computation time of the model is 22% of that of the finite volume model for the 45 data points in the present study. The proposed new model is suitable for steady-state simulation of transcritical CO2 water-cooled gas cooler, either standalone or integrated into overall CO2 heat pump water heater systems.