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).