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