The influence of thermal contact resistance on the relative performance of heat pipe-fin array systems

Abstract

Externally-finned heat pipes (HPs) using individual fins (a HP-fin configuration) or a finned heat sink (HP-heat sink) are subject to thermal contact resistances at the HP-fin or HP-heat sink interfaces. A detailed HP model is used to quantify the influence of the contact resistances on the heat transfer and fluid flow within the HP, as well as on the overall heat transfer rate. For similar area-averaged contact resistance values, the HP-heat sink typically provides a lower overall thermal resistance than the HP-fin configuration. Under off-design operating conditions, however, the HP-heat sink option can underperform the HP-fin geometry. A thermal resistance model is also developed and its predictions compare qualitatively to those of the HP model. It is shown that the overall resistance of the HP-fin configuration is proportional to the number of fins in the array that are subject to a contact resistance. Using the detailed model it is also demonstrated that the order in which the fins (fins without versus fins with contact resistances) are placed within the array has little effect on the overall thermal resistance of the HP system.