Modulating fluid rheology and confinement toward augmenting the performance of a double layered microchannel heat sink

The improvement of the cooling performance of liquid-cooled microchannel heat sinks used for densely packed electronic circuits is sorted via passive techniques like tuning substrate or coolant properties. We propose a design for enhancing heat sink performance by simulataneously modifying the channel geometry and tuning the fluid rheology. By modeling the coolant as a power law fluid, its rheological behavior is varied ranging from shear-thinning to shear-thickening, alongside Newtonian fluid. We introduced tapering to the middle wall that separates the bottom and top channels of a double layered microchannel heat sink (DL-MCHS), causing both channels to converge. This convergence not only increases the flow velocity within the downstream microchannel but also reduces the apparent viscosity of the shear-thinning fluid being subjected to shear, resulting in enhanced thermal and hydraulic performance. We analyze the results from both the first and the second law of thermodynamics context, demonstrating that a tapered DL-MCHS with shear-thinning fluid outperforms a straight partition wall DL-MCHS with Newtonian coolant. However, we also discovered that extreme tapering compromises thermodynamic viability, but by fine-tuning the extent of tapering, we inferred that a DL-MCHS with shear-thinning fluid can become viable with little compromise in the thermal performance.