Heat transfer rate prediction and performance optimization of CO2 air cooler in refrigeration system

Abstract

In order to determine the heat transfer rate of CO2, heat transfer criterion equations were selected and validated using experiment data. The impacts of various operating conditions and structural parameters on CO2 air coolers were numerical simulation investigated. The results show that the inlet dryness and mass flow rate are proportional to heat transfer coefficient (HTC) and pressure drop (PD). When the mass flow reaches 240 kg/h, CO2 reaches the critical state, and further increasing the mass flow rate has little effect on the HTC. The HTC reaches its maximum value at a dryness of 0.2, after which, it decreases due to the flow pattern changing from wavy/intermittent flow to annular flow. Moreover, the tube spacing, tube diameter, and fin spacing affect the HTC, heat exchange area, and heat exchange capacity differently. Hence, a thoroughly consideration of the structural parameter design is crucial during the actual design process.