Condensation heat transfer in smooth inclined tubes for R134a at different saturation temperatures

摘要: Abstract This paper presents the effects of saturation temperature and inclination angle on convective heat transfer during condensation R134a in an inclined smooth tube inner diameter 8.38 mm. Experiments were conducted for angles ranging from −90° (vertical downwards) to +90° upwards) mass fluxes between 100 kg/m2 s 400 kg/m2 s mean vapour qualities 0.1 0.9 temperatures 30 °C 50 °C a test matrix 637 data points. The results showed that strongly influenced coefficient. With respect temperature, increase generally led decrease coefficient irrespective angle. effect was found be more pronounced at 200 kg/m2 s range considered. Within region influence inclination, there optimum angle, which −15° −30° (downward flow). corresponded predominance gravity flow distribution. An increased two-phase transfer.