Experimental investigation of convection heat transfer of n-decane at supercritical pressures in small vertical tubes

This paper presents experimental investigations of the convection heat transfer of n-decane at supercritical pressures in vertical tubes with inner diameters of 0.95 and 2.00 mm for various inlet pressures, heat fluxes and flow directions. The effects of the heat fluxes, property variations, buoyancy and flow acceleration on the convection heat transfer were studied. The results show that for high inlet Reynolds numbers neither buoyancy nor flow acceleration affects heat transfer significantly, while for low inlet Reynolds numbers buoyancy strongly reduces heat transfer coefficient in upward flow cases. The threshold for Bo∗ was found to be about 2.0 × 10−7. Two local Nusselt number correlations for the convection heat transfer of supercritical pressures n-decane with and without buoyancy effect were developed based on the experimental data.