Thermal and thermodynamic optimization of a porous double layered microchannel heat sink

Abstract

A double-layered microchannel heat sink (DL-MCHS) is designed and modelled to investigate thermal and thermodynamic optimization for improved performance. The present design employs a combination of varying vertical porous and horizontal solid fins. A three-dimensional solid-fluid conjugate model is used with Al2O3-water as nanofluid. The volume fraction of Al2O3 nanoparticle is varied between 0.5 and 4%, and the porosity level of the vertical porous fins were changed between 0.2 and 0.8. The trend in pumping power, temperature distribution, Nusselt number, entropy generation and overall performances are characterized using performance evaluation criteria (PEC). Increasing volume fraction reduces the hydraulic performance of the system; however, the enhanced overall performance of 41.3% is achieved when measured with PEC. Reduction in pressure drop up to 41.96% is achieved with porous vertical fins. Rectangular solid ribs inserted in both lower and upper layers of the DL-MCHS, arranged in four different configurations enhanced the performance up to 19.3% compared to un-ribbed DL-MCHS. Based on the second law of thermodynamics, most ribbed configurations are thermodynamically viable because their entropy generation number is less than unity.