This paper describes a new means of analyzing the thermal response of air-cooled and liquid-cooled electronics that overcomes limitations in available tools and current design methods. It also shows how these new tools and methods can extend the reach of such thermal/fluid analyses by helping to size and locate components as well as dealing with both pre-test uncertainties and post-deployment variations in manufacturing, environment, and usage.

As the time lag from design to market diminishes, the pressure to abandon “build and test” approaches to electronics thermal cooling has created a wide variety of design analysis methods ranging from simple hand calculations of energy balances to detailed three-dimensional CFD (Computational Fluid Dynamics) approaches. Surprisingly few options are available between these two extremes, leaving most designers feeling that they face an “all or nothing” choice. Hand calculations and other simple software approaches, while contributing to an engineer’s intuition, cannot be relied upon for the entire design cycle, especially with the reduced emphasis on hardware prototyping that is necessary to speed up product development time. Fluid network modeling (FNM) approaches offer more analytic power but lack strong connectivity to geometric thermal models, and are therefore cumbersome to use. CFD approaches include limited geometric thermal modeling, but are relatively inflexible because they focus on detailed point design evaluations, and therefore contribute little to design knowledge.

This paper will describe a new approach using multidimensional heat transfer modeling in combination with ducted or quasi-multidimensional flow solutions for fast and easily modifiable models of electronics packaging that lends itself to high-level operations such as sizing and reliability estimation.

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David A. Johnson, Mark J. Welch, Brent A. Cullimore