A numerical investigation of the heat transfer in an annular jet impinging on an isothermal surface

Abstract

Annular impinging jets are commonly used in heating and cooling applications such as heat exchangers and water-cooled combustor. A numerical study of heat transfer in a laminar confined annular jet is investigated. The working fluids are air and water, with Prandtl numbers equal to 0.731 and 7.01 respectively. Two types of velocity profiles are used at the jet axis, uniform and parabolic, with Reynolds number ranging between 100 and 500 with an increment of 100. The considered nozzle to plate dimensionless distances are 3, 5 and 7. Seven cases aspect ratios varying between 0.5 and 10 are also studied. The numerical simulations showed that the maximum local Nusselt number is enhanced at large Reynolds number. As the nozzle to plate dimensionless distance and the aspect ratio decrease, the local maximum Nusselt number improves. The results show that, for Re=500, the maximum local Nusselt number for the case corresponding to a parabolic velocity profile is approximately 24% larger than the one for a uniform velocity profile at H/w=3 and Di/w=0.5. As H/w increases, the maxima corresponding to the two velocity profiles get closer to each other to each other. The minor secondary peaks are not influenced by the types of velocity profiles.