NUMERICAL PREDICTION OF FLOW AND HEAT-TRANSFER IN AN IMPINGEMENT HEATSINK

Forced flow of air overextended surfaces offers a simple, reliable, an d effective heat removal mechanism and is often employed in electronic equipment. The IBM 4381 heat sink, used in production IBM computers, utilizes this cooling technique. This hear sink consists of a ceramic substrate on which fins made of an aluminum-copper alloy are arranged in a regular army. Cooling air enters the fin array from a nozzle. Ext ensive experiments have been carried out to characterize the performan ce of this heat sink at the Advanced Thermal Engineering Laboratory at IBM Endicott. This paper presents computational analysis of the three -dimensional flow and heat transfer in this device for two different a ir flow rates through the nozzle. The heat dissipated by the electroni c components is conducted into the fins through the ceramic base. Irt the present study the ceramic base is assumed to be subjected to a uni form heat flux at the bottom. The computational method incorporates a special block-correction procedure to enable iterative solution of con jugate heat transfer in the presence of large differences in thermal c onductivities of the air and the fin material. The results of computat ions reproduce the flow pattern in the fin array that is observed expe rimentally. The part of the ceramic base directly below the nozzle is well cooled with the temperatures gradually increasing from the center towards the corner. The predicted pressure drop and most of the local temperatures at the base and the tip of the fins agree well with the experimental observations. This study illustrates the utility of compu tational flow analysis in the analysis and design of electronic coolin g techniques.