A problem commonly encountered in the thermal analysis of electronic packages is that of thermal spreading resistance. Thermal spreading resistance occurs as heat flows by conduction between a source and a sink with different cross-sectional areas. Examples of two situations involving spreading heat flow are shown in Figure 1. One example is that of a chip mounted on the bottom … [Read more...]
Surface Flatness
Surface flatness is an important issue for thermal designers as it is directly related to thermal contact resistance between surfaces. In this column, the definitions of surface flatness related parameters are discussed. These definitions are presented here as in the ASME B46.1-1995 standard [1]. Surfaces are characterized by three main parameters: roughness, waviness, and … [Read more...]
Air Cooled Compact Heat Exchanger Design For Electronics Cooling
Introduction This article will discuss air-cooled compact heat exchanger design using published data. Kays & London's Compact Heat Exchangers [1] contains measured heat transfer and pressure drop data on a variety of circular and rectangular passages including circular tubes, tube banks, straight fins, louvered fins, strip or lanced offset fins, wavy fins and pin fins. … [Read more...]
Estimating The Effect Of Flow Bypass On Parallel Plate-Fin Heat Sink Performance
In past issues of Electronics Cooling, methodologies were presented for estimating parallel plate-fin heat sink thermal resistance [1] and pressure drop [2]. The underlying assumption for both articles was that all the flow delivered by the fan is forced to go through the channels formed between the fins. As noted in the second article this is often not the case and much of the … [Read more...]
The Benefits Of Using Hadiabatic In Thinking About Electronics Cooling
The heat transfer coefficient is used to describe convective heat transfer between a solid and a fluid, as in Equation (1). The heat transfer coefficient is a defined parameter, not a physical property like thermal conductivity, and different definitions are used for different situations. The preferred definition for use in the electronics-cooling situation is … [Read more...]
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