Heat Transfer Characteristics of Small-Sized Plate-Fin Heat Sink Array in Supercomputer

The heat transfer characteristics of 128 plate-fin heat sinks in a supercomputer chassis are simulated by CFD method. The fin-pitch and fin-thickness of the heat sink are optimized and a crucible-shaped profile of the maximum temperature of the ASIC chips vs. fin-pitch and fin-thickness is derived. A thermal resistance model was set up to explore the profile and it demonstrated that the profile is arise from the joint action of the thermal conduction and convection in a small-sized heat sink, and that this phenomenon can be attributed to the fact that the dependencies of thermal resistances on either fin pitch or thickness is non-monotonic. The criterion regarding the fin-pitch and fin-thickness optimization as well as the Biot number is developed. Biot criterion is applicable to estimate the Biot number of heat sink and act as the application criterion of heat sink, but not applicable for small-sized heat sink in which convective coefficient is a function of fin-pitch. The empirical formula of heat transfer and the design rule of such a heat sink are given: the optimized range of fin-pitch is between 0.5mm ~ 2mm and that for fin-thickness is between 0.1~1mm