Investigation into simulation of phase-change jet impingement for electronics cooling

Abstract

It is now widely accepted that conventional electronics cooling methods are no longer sufficient to keep modern-day electronic components below their maximum operating temperatures. As a result, thermal considerations have become the limiting factor in the improvement of semiconductors. To meet the cooling requirements of these devices, new cooling methods are needed. To keep up with the heat removal requirements of electronic components, researchers have investigated multiphase cooling methods extensively. They have identified jet impingement boiling as one of the most promising thermal management techniques for high heat flux applications.

Jet impingement boiling has been studied extensively in the literature, and researchers have identified the key jet parameters and their influence on heat transfer. Unfortunately, only a few numerical studies have been reported in the literature and they are limited to single jets. The numerical studies on jet impingement boiling available in the literature do not provide all the sub-models used in the numerical study, leaving much uncertainty. With the limited application of single jets and the limited information resulting from experimental studies, numerical studies on multijet arrays are essential for the advancement of jet impingement boiling and widespread use thereof in the electronics cooling industry.

In this study, both submerged single round jets and confined multijet arrays were investigated numerically, using the Eulerian multiphase framework with the Rensselaer Polytechnic Institute (RPI) boiling model to predict heat transfer, as implemented in ANSYS Fluent. The numerical results of the single-jet case correlated well with reported experimental data and with previously reported numerical results. The numerical results of the multijet array correlated well with experimental data reported in the literature, proving that the RPI boiling model could successfully predict the heat transfer of jet array boiling. The effect of conjugate heat transfer in jet impingement boiling heat transfer was also investigated for single- and multijet cases. The single-jet results agreed with previously reported numerical studies. To improve numerical convergence, especially for higher heat fluxes, a hydrostatic pressure gradient was used at the outlet. This allowed for significant improvement in the convergence of the continuity equation.

Finally, parametric analyses were conducted for both single- and multijet arrays in the fully developed nucleate-boiling regimes. Parameters included jet-to-surface spacing and jet Reynolds number for single submerged jets. Parameters for confined multijet arrays included jet to surface spacing, jet to jet spacing and jet Reynolds number. The results of single submerged jets correlated well with experiments reported in the literature. The results of the multijet array cases showed less sensitivity to changes in jet velocity and jet to surface spacing than for the single-jet case. The multijet array cases showed much higher sensitivity to the jet to jet spacing than to the jet to surface spacing and jet Reynolds number, indicating that both jet to jet interaction and cross-flow played significant roles in the heat transfer of multijet arrays, confirming the observations of experiments reported in the literature.

The study concluded that the RPI boiling model could successfully predict the heat transfer of jet impingement boiling and could be used to conduct parametric investigations that align well with the experimental findings. The study further concluded that more experimental studies of multijet arrays in the nucleate-boiling regime with low degrees of subcooling were required to further validate the numerical models. It was found that a bubble departure frequency model applicable to flow boiling with high degrees of subcooling was essential to model boiling jets with high degrees of subcooling. Finally, the influence of the jet parameters on pressure drop and the influence of the heat transfer fluid on heat transfer as well as the operating pressure were identified as two major challenges that must be met before jet impingement boiling can be widely implemented.