Experimental study on heat transfer of supercritical Freon flowing upward in a circular tube

Abstract

Experiments of heat transfer to supercritical Freon R134a flowing upward in a circular tube with inner diameter of 7.6mm were carried out with mass fluxes of 600–2500kgm−2s−1, heat fluxes of 20–180kWm−2, bulk fluid temperature of 71–115°C and pressures of 4.3–4.7MPa. Effects of various parameters on heat transfer behavior are analyzed. Significant heat transfer deterioration is observed at low mass flux and high heat flux conditions. Four representative correlations are selected and compared with the test data. The correlation of Jackson gives the best prediction of the test data among the selected correlations. Based on a detailed analysis of the effect of various dimensionless parameters on heat transfer, a simple correlation containing only the acceleration parameter πA to modify the Dittus–Bolter correlation is proposed. The present correlation shows good agreement with the test data.