Numerical investigation of heat transfer enhancement from a protruded surface by cross-flow jet using Al2O3–water nanofluid

Abstract

In the present paper, the heat transfer performances of a nanofluid jet impinged normal to a protruded surface have been studied numerically in a three-dimensional computational domain. The water soluble Al2O3 nanofluid has been employed as the working fluid both for the nozzle and the duct. A finite volume technique has been used to solve the conservation equations for mass, momentum, and turbulence (SST k–ω turbulence). The duct and the nozzle Reynolds numbers based on the hydraulic diameters are varied in the range of 6000–20,000. The nanofluid volume fraction has been varied in the range of 0%⩽ϕ⩽5%. For a particular volume fraction of nanofluid, it has been observed that the heat transfer augmentation is increased with the duct (ReDh,duct) as well as the nozzle (ReDh,nz) Reynolds number. For a particular volume fraction (ϕ=5), when the duct and the nozzle Reynolds numbers have been increased from 6000 to 20,000, the area-weighted average Nusselt numbers (Nu‾Dh,duct) increases by 72.7% and 68.57%, respectively. Moreover, the addition of the solid nanoparticles to the base fluid enhances the heat transfer rate significantly. However, the pumping power requirement has also been increased with the volume fraction of nanofluid. The effects of the conductive/non-conductive protrusions and the temperature dependent properties on the heat transfer enhancement have also been discussed. The flow recirculation in inter-protrusion gaps in the context of heat transfer augmentation has also been discussed.