Hardy-Cross법을 이용한 CO2 냉동기용 내부 열교환기의 열전달 특성 연구

초록

The heat transfer characteristics of an internal heat exchanger for CO2 refrigeration cycle is numerically investigated. The numerical model is verified using the published experimental results for the concentric tube type internal heat exchanger. The Hardy-Cross Method gives very good agreement between the calculation and experimental results on the heat transfer rates and exit temperatures. Also, appropriate combination of heat transfer correlations is found. The operating parameters of the heat exchanger are calculated at transcritical region of CO2. The heat transfer rate of the counter flow type heat exchanger shows the 32% greater than that of the parallel flow type heat exchanger. The increase of heat exchanger length enhances the heat transfer rate. The thermodynamic characteristics and heat transfer coefficient of CO2 in the internal heat exchanger are estimated.