Laminar Heat Transfer of Gas-Liquid Segmented Flows in Circular Ducts With Constant Wall Temperature

Abstract

Laminar heat transfer of gas-liquid Taylor flow in circular tubes is considered. Previous studies have found that introducing a gas phase into a flow stream of a liquid phase significantly increases the heat transfer rate. Other studies considered the effect of slug length on heat transfer rates. The present study’s aim is to demonstrate heat transfer enhancement due to the shortening of liquid slug lengths in a segmented flow and to further validate a model previously developed by the second author. An experimental setup was assembled using mini scale horizontal tube in which the two phase fluid flow is heated under constant wall temperature. New experimental data for gas-liquid Taylor flow in mini scale were carefully obtained using 1 cSt silicone oil which was segmented by air. The experiments were performed with a liquid fraction maintained constant at 0.5 and Reynolds numbers from 50 to 320. In the present work, it is shown that for constant wall temperature, the dimensionless mean wall flux and Nusselt number have been increased by a factor of two at the upper limit of laminar flow which was considered with ReD = 320, when the slug aspect ratio LS/D equal to 10. On other hand the enhancement becomes three times at the same limit of flow when slug aspect ratio has reduced to 1.25 which almost approaches the tube diameter.