Convective condensation heat transfer of R134a in tubes at different inclination angles

Abstract

An experimental study of convective condensation heat transfer of R134a was conducted in an inclined smooth copper tube of inner diameter of 8.38 mm. The test condenser had a straight copper tube section with an effective length of 1.488 m and was cooled by water circulated in the surrounding annulus in a counter-flow arrangement. The rate of heat transfer was maintained at an average of 250 W throughout the experiment while the mean vapour qualities ranged between 0.1 and 0.9, mass flux between 200 kg/m2s and 400 kg/m2s for inclination angles varied between -90o (vertical downward) and +90o (vertical upward) covering the whole range of inclination at saturation temperature of 50oC. The results show that the inclination angles and mean vapour qualities strongly influence the coefficient of heat transfer and an optimum inclination angle was found to be between -15o and -30o (downward flow). The developed correlation gave an average and mean deviations of -3.44% and 9.22% respectively for horizontal flow and, 5.25% and 19.41% respectively for vertical downward flow.