Convection Heat Transfer of CO2 at Supercritical Pressures in Microtubes

Convection heat transfer of supercritical pressure CO2 in microtubes as well as characteristics of fluid flow and heat transfer were investigated. Alterations of physical properties of supercritical CO2 and the impact of buoyancy on the heat transfer were analyzed when the inlet Reynolds (Re) number of CO2, diameter of heat exchanger, and inlet Re of cooling water were changed. The temperatures of hot fluid in numerical simulations from several classical turbulence calculation models were compared with experimental results from the literature. The physical properties of CO2 changed significantly around the critical point, causing a distinct decline of buoyancy and strengthening of heat transfer.