Heat transfer enhancement in turbulent dual jet and its thermal characterizations using large eddy simulation

Abstract

Heat transmission is the prime aim of any thermal device that requires effective cooling. This requirement becomes significantly more vital for a turbulent jet, which is encountered quite often in industrial and engineering purposes. The present study investigates thermal and turbulence characteristics of a turbulent dual jet using Large Eddy Simulation (LES). The bottom surface is maintained at isothermal and isoflux boundary conditions and the flow Re is 7500. The profiles of Reynolds shear-stress, turbulence kinetic energy, wall friction coefficient, r.m.s. temperature, mean Nusselt number, bottom wall temperature, and turbulent heat fluxes are investigated and scaled using outer, thermal and inner parameters. Variations in Nusselt number and bottom wall temperature are also studied. A significant rise in Nusselt number is observed nearer to the jet exit which enriches the cooling rate. Overall, the finding shows that compared to the wall jet and parallel flowing offset jet, the inflection point in the mean temperature profile of the present dual jet scaled with the thermal variable and outer variable is higher. Further, it is also observed that the thermal transmission spreading out of the wall is quite efficient in the low-pressure area of the dual jet. Near-wall eddies and the development of roller-like structures are seen. The interaction occurring through the inner and outer layers increases the momentum transfer along with turbulent heat-flux and a large amount of heat is lost due to turbulent flow.