Numerical investigation of nanoparticles dispersion on forced / mixed convective flows and heat transfer in a lid-driven stepped cavity configurations

Abstract

With the recent trends in the manufacturing techniques of semiconductor chips, the compactness of electronic devices is getting improved. Though the computational speed is improved extensively, overcoming the heat dissipation remained the most challenging task. Buoyancy based convection in the heat sink alone is not sufficient to extract this huge amount of heat. Therefore, better heat transfer enhancement methods are essential to designing thermal efficient electronic devices. One of these techniques is the induction of forced convection by driving one of the lids of the sink. In this work, a 2-Dimensional steady-state thermal analysis of a moving lid enclosure provided with water/ (water + CuO) nanofluid for different Grashof numbers (5000, 13000, and 20000), Reynolds numbers (100, 200, 300, 400, and 500), and volume fractions (1%, 3%, and 5%) is carried out. The impact of Gr, Re, and volume concentrations on Nusselt number is studied. The design of the solid zone is studied by considering three different orientations (Frontward step, Zero step, and Rearward step). The maximum amount of heat transfer is achieved with the Frontward step for Gr = 20000, Re = 500, and 5% CuO volume concentration in pure water. For Re = 100 and Gr = 20000, Nu_avg is improved by 5.49% for mixed mode of heat convection as compared to forced mode of heat convection. A heat transfer enhancement of 42.75% more than pure water is attained with a 5% CuO volume fraction of nanofluid at Re = 500 for frontward stepped geometry. However, there is a reduction in the rate of increment of (12.98% vs 16.54%) upon further addition of nanoparticles from 3 to 5% as compared to 1 to 3%.