Optimal design and thermal performance improvement of a double-layered microchannel heat sink by introducing Al2O3 nano-particles into the water

In this paper, Al2O3 nano-particles are introduced in liquid water for improvement of a double-layered microchannel heat sink. A three-dimensional conjugate two-phase model is numerically coupled with exhaustive search method to optimize the design of a double-layered microchannel heat sink (DL-MCHS) cooled with Al2O3 - water nanofluid. The geometrical and physical parameters of the DL-MCHS are assumed as the optimization variables, while the minimization of the DL-MCHS thermal resistance is selected as the optimization objective. The design parameters include thicknesses of the DL-MCHS ribs, the number of channels, height and width of the channels, and the inlet coolant velocities in each layer. The optimization is subjected to the space and the fixed pumping power rate, or the fixed volumetric flow rate. The numerical optimization is conducted step by step, to provide a big picture of how the DL-MCHS evolves to improve, by computing the temperature field in a wide variety of DL-MCHS configurations while seeking for the best situation. The results indicated that the optimization of the DL-MCHS geometrical and physical parameters in conjunction with the use of nanofluids as the working coolant, deliver an excellent design for the DL-MCHS. For example, the thermal resistance of the optimized DL-MCHS with nanofluid in the present work was found about 10% lower compared with the similar previous works.