Numerical study of the influence of the geometrical aspect ratio and nanoparticles diameter on forced convection in a micro-channel heat sink of a nanofluid water/CuO based on a Brownian diffusion model

Abstract

In order to cool electronic equipment with a high efficiency we can use the flow of a nanofluid in a rectangular micro-channel heat sink. The paper reports the results of the study of a hydrodynamically fully developed laminar forced convective heat transfer flow in two different geometries G1and G2. The study is numerical and was achieved using as nanofluid with and a single-phase approach. Calculations were first made with constant thermo-physical properties at and then made using temperature and nanoparticles diameter dependent thermo-physical properties based on a Brownian diffusion model. A three-dimensional conjugate heat transfer model was used and numerical simulations were based on a finite volume method. The simulations were made for a range of Reynolds numbers , for nanoparticle diameter in the range of and for a heat flux through the bottom surface of the heat sinks .The results of thermal and hydrodynamic fields show that nanofluids can provoke an increase in the local and average Nusselt numbers, a decrease of bottom surface local temperature and a slight decrease of the shear stress on the wall, particularly in the case of geometry G2. At the end of the study, the best geometry, volume fraction of nanofluid and nanoparticle diameter to be recommended for cooling were found based on minimum total thermal resistance of the micro-channel heat sink.