POOL BOILING HEAT-TRANSFER AT FINNED TUBES - INFLUENCE OF SURFACE-ROUGHNESS AND SHAPE OF THE FINS

Pool boiling heat transfer from finned tubes with different shapes of fins (trapezoid-shaped, T-shaped, or Y-shaped) to various hydrocarbons and partly fluorinated hydrocarbons has been investigated at the Labo ratorium fur Warme- und Kaltetechnik, Universitat-GH Paderborn during the recent past. Compared to corresponding measurements on plain tubes , heat transfer on traditionally finned tubes with trapezoid-shaped fi ns is considerably improved, and even better results are achieved with T-shaped or Y-shaped fins. The influences of the macrostructure (i.e. fin geometry) or microstructure (i.e. surface roughness) on the heat transfer coefficient have been studied separately, in order to evaluat e the improvement of heat transfer by either influence. (C) 1998 Elsev ier Science Ltd and IIR.