On conjugate heat transfer in microchannel heat sinks

This work aims to study the anisotropic thermal impacts of employing liquid metal fluids including Na and NaK as coolants in two metallic microchannel heat sinks. The two studied microchannel heat sinks have aspect ratios of 1 and 2 while their hydraulic diameters are 267 µm and 400 μm. In the first stage, the accuracy and reliability of the developed numerical model are verified against benchmark problems and experimental data. In the second stage, the utilized verified and validated numerical model is extended to forced convection of Na and NaK in metallic microchannel heat sinks. The investigated metallic microchannel heat sinks are assumed to be out of stainless steel and Nickel with thermal conductivities of 17 W/mK and 90 W/mK, respectively. Obtained results revealed that NaK provides higher Nusselt numbers than Na regardless of the microchannel aspect ratio and hydraulic diameter. The effect of the microchannel heat sink solid substrate thermal conductivity on the temperature and heat flux distributions over the microchannel walls are also investigated comprehensively. For the investigated steady state Na and NaK flow within metallic microchannel heat sinks, the thermal conductivity of the heat sink solid substrate is observed to have a significant effect on the local temperature and heat flux distributions over microchannel walls.