Experimental Investigation of Convective Heat Transfer to Supercritical Carbon Dioxide

Abstract

Recently, there is also renewed interest in using supercritical carbon dioxide as the alternative substitution of refrigerants, such as CFCs and HCFCs, in refrigeration and cryogenic engineering.But accurate prediction of convective heat transfer coefficients for supercritical fluids is still an unsolved problem, due to the rapid variation of thermal physical properties in pseudo-critical zone. Experimental investigation of turbulent convective heat transfer in vertical supercritical carbon dioxide flow was conducted ina heated bare tube with an inner diameter of 10mm. The data shows that the phenomenon of buoyancy and acceleration is obvious. For the upward cases, as the buoyancy effect increasing the forced convective heat transfer to carbon dioxide will transient to mixed convective heat transfer, then free convective heat transfer, in which the heat transfer capacity is weakened firstly, then resumed and strengthened. The acceleration often weakens the heat transfer capacity both for upward and downward flow. A new heat transfer correlation for vertical upward flow of supercritical carbon dioxide was developed, of which the accuracy has been improved obviously.