ERROR IN LUMPED-PARAMETER ANALYSIS OF HEAT-FLOW RATE THROUGH EXTENDEDSURFACES ACCOUNTING FOR THERMAL CONTACT RESISTANCE

order to predict the heat flow rate through extended surfaces, the the rmal problem is frequently schematized by lumped parameter models base d on the thermal resistance concept or one-dimensional analysis. Howev er, some error is inherent in this idealization because it neglects th e heat flux between the finned and the unfinned portions of the wall, In this paper the results given by two lumped parameter models, the se ries model and the parallel model, are compared with an analytical sol ution obtained by applying the series truncation method to the true tw o-dimensional problem. The results show that the parallel model is com pletely unsatisfactory while the series model gives an acceptable over estimate of the heat flow rate. The last conclusion is particularly tr ue for inhomogeneous wall and fin because a thermal contact resistance between the fin base and the wall reduces the relative error of the l umped parameter model.