A numerical and experimental investigation of heat transfer and fluid flow characteristics of an air-cooled oblique-finned heat sink

Abstract

The thermal and hydraulic performances of an air-cooled, planar, oblique-finned heat sink (OF HS) were investigated for two oblique angles: 30° and 45°. The conjugate heat transfer between the heat sink and the air flow were computed numerically in ANSYS Fluent for a range of air flow rates for the smallest periodically repeating portion of the heat sink. The RNG k-ε turbulence model with enhanced wall treatment was used to solve the fluid flow and heat transfer. Followed by the experimental validation, the numerical results were scrutinized further to understand the effects of the flow field on the measured heat transfer performances. Apart from boundary layer disruption, vortices generated within the secondary channels due to flow separation particularly improved the advection component of the convective heat transfer, resulting in a heat transfer enhancement, exceeding the pressure drop penalty. The strong flow mixing, showing chaotic behavior, enabled a more uniform increase in the air temperature in the streamwise direction, utilizing the cooling potential of the air flow more effectively. 30° oblique-finned heat sink was observed to induce higher rates of secondary flow rates and improve the heat transfer performance more than its 45° counterpart. Due to the migration of the flow in the direction of the secondary channels, the heat transfer enhancement was compromised at high Reynolds numbers, the pressure drop penalty exceeded the heat transfer enhancement, causing a reduction in the thermal-hydraulic performance factor. The effects of flow migration on the flow and temperature fields were investigated with full domain numerical simulations. Experimental investigations showed significant improvements in the junction temperatures.