Influence of Macroscopic Heat Flow Constrictions on the Performance of FinlTube Heat Exchangers

Abstract

An investigation of the influences of macroscopic constrictions on the thennal performance of plate-fin heat exchangers is described in this report. Parametric studies cover parameter ranges that are typical of the evaporators used in household refrigerators. Exhaustive numerical investigations are presented that show the influences of: (i) the macroscopic contact geometry-the contact between the plate fin and the tube, (ii) the fm parameter-a dimensionless group that governs the fin efficiency, (iii) the fm geometry, (iv) the interstitial conductance, (v) the constriction alleviation caused by the shunting of a part of the heat flow through the frost buildup around the base of the fin, and (v) the effect of fins with collars--an enlarged apparent contact area at the fin/tube interface. Dimensionless parameters and the physical significance of these parameters are deduced that govern the thermal performance of fins with and without constrictions in the heat flow path.