ISSN Online: 2377-424X
International Heat Transfer Conference 12
Experimental Investigation and Prediction of Flooding during Reflux Condensation in a Small Diameter Inclined Tube
Abstrakt
In this experimental investigation flooding points are determined during reflux condensation of R134a and steam in an inclined, small diameter tube. The inner diameter of the tube is 7 mm and the cooled length is 500 mm. In addition the condensate film thickness of R134a is measured using the ultrasonic pulse-echo technique before the onset of flooding. The R134a experiments show that the inclination angle has a significant effect on the flooding point. The optimum inclination angle at which the highest flooding vapour velocity occurs is between 45° and 60°. In contrast, due to the much higher surface tension of water such a significant effect cannot be observed in the steam experiments. The experimental flooding data are compared with values predicted by correlations but a satisfying agreement cannot be noticed. A modified form of a flooding correlation by English et al. is proposed for the R134a experiments that is valid for all inclination angles. The derivation of a general correlation for the prediction of flooding during reflux condensation in inclined, small diameter tubes for a wide range of fluid properties appears to be difficult. The condensate film thickness data that have been obtained with the pulse-echo
technique give information about the distribution of the condensate film in the inclined tube. This might be helpful
for obtaining a more general flooding correlation for reflux condensation in inclined, small diameter tubes.