Performance Analysis of Tube in Tube CO2 Gas Cooler
ANKUSH HARISHCHANDRA UMBARKAR
Gas cooler, CO2 Heat pump,Transcritical, approach temperature difference
As a kind of promising natural refrigerant, carbon dioxide has been attracting much attention from many researchers, especially in the fields of automobile air conditioners, commercial refrigeration, and water heating. When the CO2 refrigerant is used in heat pump water heaters (HPWHs), it exhibits excellent performance in HPWH applications. The coefficient of performance (COP) of the system may achieve higher values than conventional refrigerants because of better temperature glide matching. Additionally, CO2 HPWHs could provide higher temperature water up to 90 °C. In CO2 air-conditioning and heat pump systems, CO2 rejects heat at a pressure above the critical pressure (7.38 MPa) in the gas cooler without phase change. When the CO2 is at supercritical pressures, some small fluid temperature and pressure variations may produce large changes in the thermophysical properties, and this is especially pronounced when the temperature is near the critical point. The gigantic change in the thermophysical properties may result in significant deviations in both heat transfer and fluid flow behaviors. This study will show the effect of nonlinear variation of supercritical CO2 specific heat capacity with temperature on local heat transfer rate.