As many readers of ElectronicsCooling are aware, there is a growing interest in the electronics cooling community in the possible use of liquid cooling. This interest is, of course, due to the trend of increased heat loads at chip, module, and system levels of packaging. The article by Mohapatra [1] in this issue of ElectronicsCooling provides a good overview of both dielectric … [Read more...]
A Simple Thermal Resistance Model – Isoflux Versus Isothermal
In most cases today thermal design for electronic products is performed with the aid of sophisticated computational fluid dynamics and heat transfer codes. Nonetheless, there may still be occasions when a thermal designer needs a quick estimate of the external thermal resistance of a package or heat sink that does not warrant the use of powerful computer codes. In such cases an … [Read more...]
Using an Equivalent Heat Transfer Coefficient to Model Fins on a Fin
Many readers of ElectronicsCooling are probably familiar with the use of fin efficiency formulas to estimate the thermal resistance of the commonly used parallel plate fin heat sink. Given the heat transfer coefficient, h, acting on a fin and the dimensions of the fin, the thermal resistance of an individual fin is given by: where Af and η are the surface area and … [Read more...]
Estimating Temperatures in an Air-cooled Closed Box Electronics Enclosure
Introduction In the majority of air-cooling applications, openings or vents are provided in the enclosure or box in which the electronic components are housed. The required cooling air is drawn in from outside the box by fans or blowers. In some applications, however, there may be airborne particulates or other substances in the air that would be injurious to the electrical … [Read more...]
Simple Formulas for Estimating Thermal Spreading Resistance
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...]
