Horizontal tube-side condensation of steam in the presence' of a non-condensable gas.

Abstract

An apparatus was constructed for experimental work on condensation of steam-air mixtures in a horizontal tube.The effects of inlet fluid temperature,air mass concentration and tube diameter on the rate of condensation were investigated. It was found that condensation heat transfer coefficient drops by approximately 50% within an air mass of 3% and there after the drop in the heat transfer coefficient became gradual. For fixed air mass concentration and inlet fluid temperature, the heat transfer coefficient increased with a decrease in tube diameter. For fixed tube diameter and air mass concentration , the mean heat transfer coefficient decreased with increasing inlet fluid temperature. From measurement of pressure drop across the test section, it was found that the theoretical m" lel based on a two phase pressure drop equation,integrated piece wise along the test section and making use of global parameters

for every section gave values comparable to those determined from the experiment. From the theoretical model based on condensation heat transfer coefficient in the presence of non condensable gases correlation, it was found that t he model predicted temperature profiles accurately in the range of saturated steam but was subjected to errors in the superheat region.

The comparison between the experimental values of condensation heat transfer coefficient at zero concentration of air and those predicted by Shah(1979) and

Akers et al(1958) showed that the former correlation consistently predicted much higher values at all conditions while the latter predicted values closer to experimental values especially at saturation and small degrees of superheat.