Computational framework development for heat transfer studies in liquid metal-cooled small-scale heat sinks with non-circular cross-sections

The present work provides a reliable computational framework to investigate the laminar and turbulent forced convection of sodium and sodium-potassium (Na, NaK) in miniature heat sinks with hydraulic diameters between 1 and 5 mm. Na and NaK flow and heat transfer are studied numerically for a wide range of Reynolds numbers from 600 to 9,000 in three sharp-cornered miniature heat sinks with rectangular, pentagonal, and hexagonal cross-sections. For a fixed surface area to volume ratio in all three heat sinks and for both Na and NaK, it is observed that the rectangular minichannel heat sink provides the highest heat transfer rates. The rectangular miniature heat sink is shown to have a 280% higher convective heat transfer rate in comparison with the pentagonal heat sink. Moreover, the obtained convective heat transfer coefficients for NaK are almost 20% higher than the ones for Na in the investigated pentagonal heat sink in both laminar and turbulent flow regimes. At the same flow Peclet number in the studied rectangular and hexagonal heat sinks, both Na and NaK provide nearly identical average Nusselt numbers while NaK shows higher local and average Nusselt numbers compared to Na at the same Reynolds number.