Effect of gravity forces on heat transfer and pressure drop during condensation of R134a

Abstract

The present paper is dedicated to an experimental study of the effect of gravity forces during condensation of R134a in an 8.38 mm inner diameter smooth tube in inclined orientations. Flow pattern, heat transfer coefficient and pressure drop are presented as a function of the inclination angle for different mass fluxes (G = 200 − 400 kg/m2s) and different vapour qualities (x = 0.1 − 0.9). An apparent void fraction was also defined from the pressure drop measurements. Maps of the inclination effect on the flow pattern, heat transfer coefficient and apparent void fraction were drawn and a limit between the gravity-dependent and gravity-non-dependent zone was determined for each case. It was shown that the flow can be considered as gravity-non-dependent for high mass fluxes (G ≥ 300 kg/m2s) and high vapour qualities (x > 0.6 − 0.7).