An experimental IR thermographic method for the evaluation of the heat transfer coefficient of liquid-cooled short pin fins arranged in line

Abstract

The last developments in the electronic fields bring to high specific thermal fluxes to dissipate. These high thermal fluxes, localized on small exchange surface areas, often require cooling systems based on liquid in forced convection; a typical one is the cold plate. This normally has short fins on the liquid side and its heat exchange performance is strongly influenced by the fin efficiency that is related to the fins shape and arrangement. In the most part of the case the fins on the liquid side have a small aspect ratio and so the tri-dimensional fluid dynamic effects on the fin tips are not negligible in relation to the thermal exchange capabilities. This research work is aimed to evaluate the convective heat transfer coefficient, i.e. the Nusselt number, of short pin fins cooled by means of water in forced convection. In particular the work is focused on the geometry (circular, square, triangular, rhomboidal) shape effect for three pins in line assembled and the thermal analysis is performed by using a quantitative infrared method developed in a previous work. The thermal analysis is related to ink flow visualizations in order to better understand the effects of the main flow field on the thermal exchange capacities of every pin inside the line. The results show a dependence for the Nusselt trends on the pin position; this is due to the shadow effect of the pin upstream with respect to the one downstream. This behavior is strongly influenced on the pin geometry and particularly there is a better behavior for the triangular and rhomboidal pins.