An Investigation Into the Effects of Steam Condensation on Fluid Distribution When Occurring on the Tube Side of a Miniature Shell and Tube Heat Exchanger

Abstract

A hypothesis is evaluated for a miniature shell and tube heat exchanger that the distribution of flow through the tubes is non-uniform when steam condenses inside the tubes. It is believed that due to the small tubing size, surface tension effects, generally negligible in larger exchangers, will have a noticeable effect on distribution of condensate through the tube bundle. This hypothesis was tested using a custom-built miniature shell and tube heat exchanger. The unit consisted of nineteen 0.094” OD tubes (0.010” wall thickness) in a 3/4” OD shell. The effect of both angle of inclination (0°, 45° and 90°) and steam flow regime (loosely defined as low, medium and high) on fluid distribution were investigated. Initial results proved that the flow distribution during condensation on the tube side was non-uniform; within a given trial, each tube produced a significantly different amount of condensate. Furthermore, while at a horizontal angle this non-uniformity was observed to be sporadic with respect to tube location. A tube that produced little condensate in one trial might produce a substantial amount of condensate in a subsequent trial. With increasing angle of inclination, the amount of fluid condensed became more consistent with respect to tube location within the bundle. The experiments were meant to be a preliminary investigation to either prove or disprove the hypothesis. As experimental results did not disprove the hypothesis, future study is recommended. More research into the effects of angle and flow rate on distribution should be conducted. Additionally, the effect of tube size should also be studied. If surface tension is the true explanation for the observed phenomena, it is expected that as the tube size increases, the amount of mal-distribution will be minimized.