A STUDY ON INDUSTRIAL HEAT SINKS FOR POWER ELECTRONICS Giampietro Fabbri, Marco Lorenzini, Sandro Salvigni Dipartimento di Ingegneria Energetica, Nucleare e del Controllo Ambientale, Facoltà di Ingegneria, Università degli Studi di Bologna, Viale Risorgimento 2, 40136 Bologna. ABSTRACT The paper deals with an application of research over wavy fin channels to industrial devices for the cooling of high power-dissipating electronic component. An industrial heat sink for forced air cooling of power electronics is tested to assess its performance under different working conditions: these include the layout of the power-dissipating sources, number of spacers between fan and heat sink, amount of power dissipated. The velocity profiles at the exit of the channels are determined with a hot wire anemometer for two different number s of spac- ers. The temperature distribution is measured for the case of uniform heat flux through the component, when this is placed close to the edge where the fan is located or in the middle of the heat sink. The power dissipated is varied from 125 W to 500 W and the tests are performed for both one and five spacers between fan and heat sink. Thermal resistance is also calculated for all configura- tions which have been tested. It is concluded that for the studied configuration the most profitable is the one having the heat sink placed in the middle and only one spacer. INTRODUCTION Finned heat sinks are largely employed in many engineering fields. The industry demands heat exchangers of ever increasing compactness and equivalent or improved performance, which spurs the researchers into devising and testing new geometries for the heat sinks. The use by the electronic industry of compo- nents dissipating more and more power has produced a large amount of studies on new models of heat exchangers, which must be able to accommodate large heat fluxes while keeping the same spatial dimensions. Both trends led the researchers to develop new profiles for the fins so as to optimise performance while decreasing the dimensions. [1-3]. The problem of profile optimisation for a heat sink in order to transfer the maximum amount of heat under the constraint of the least possible volume hasn’t been completely resolved yet. The first to suggest an op- timisation criterion was Schmidt (1926), who adopted a para- bolic profile [4]. Many authors later opposed Schmidt’s conclu- sions, as they hardly reproduced the physical occurrence of the phenomenon. Since then, many profiles for the heat sinks have been suggested, mainly parabolic or triangular in shape, but without an ultimately satisfying answer to the issue of optimisa- tion [5]. Wavy profiles are of more recent origin [6], and it has been demonstrated that the superposition of a wavy profile to a parabolic one can increase the heat exchanger’s efficiency re- markably. Studies on the performance of heat sinks with wavy profile have been presented [7,8]; these employed one- and two- dimensional models and demonstrated that substantial increase in effectiveness of the heat exchanger can be obtained by vary- ing some form factors. Since a few years fins with wavy profile have had a break- through in industrial application, and heat sinks with wavy fins are now available on the market for cooling electronic compo- nents both for computer hardware and power electronic applica- tions. This study aims at a preliminary assessment of the per- formance of a commercial heat sink (manufactured by LDS System) with wavy channel walls under different operating conditions. HEAT SINK DESCRIPTION AND EXPERIMENTAL SET-UP The heat sinks studied consist of a series of corrugated alu- minium plates produced through cold extrusion. The plates are assembled by packing the single elements (A in Fig. 1) and then pressing them together by means of a mechanical vice. The 121 128 A B C Figure 1 - Drawing of the Heat Sink’s Front 1