Evaluating Liquid-Cooled Heat Sink Resistance Data for Electronic Applications Available to Purchase

A number of experimental studies have been published for single-phase liquid cooling for electronic heat sources. These include flow though various sized channels and configurations. Results are expressed using a thermal resistance as a function of liquid volumetric (or mass) flow rate. This paper discusses the regression of experimental data. Two simple thermal resistance models are evaluated, each having a combination of conduction and convection components. The models are applicable to a wide set of data. A preferred model is identified having three parameters: (1) overall resistance at a nominal flow, (2) percentage of resistance due to conduction at the nominal flow, and (3) convective exponent for the liquid flow rate. The preferred model has lower correlation between its parameters and reproduces the trends in experimental data. The model is used to quantify the relative contribution of the convective and conductive sources of thermal resistance. It is also useful in design to evaluate the effectiveness of increasing the liquid flow rate which can be accomplished with increased pressure drop and pumping costs. The best-fit estimates and their approximate 95% confidence intervals are calculated using experimental data. A few experimental results yield discrepant values for the model parameters. In some cases the rate of reduction of the thermal resistance with increasing flow rate appears beyond what can be reasonably expected. Sources of discrepant results are discussed. The results of the paper are helpful in evaluating experimental data and guiding the design of liquid-cooled heat sinks.