Effect of Offset Ratio and Plate Motion on Conjugate Heat Transfer in a Turbulent Offset Jet Flow Over the Heated Plate

Abstract

The present investigation focuses on studying the conjugate heat transfer behavior for a turbulent offset jet flow over a heated plate moving uniformly in a positive axial direction. Heat transfer from heated walls to flowing fluids is a subject of great scientific interest and practical importance due to many industrial applications like cooling hot rolling sheets and slabs, cooling continuous casting, etc. The conjugate technique adopted in the present investigation requires consideration of conduction in the solid and the convection from the solid surface to the fluid. For the simulation, a low-Re modified k−ε model developed by Yang and Shih (YS model) is adopted. The YS turbulence model uses the integration-to-wall (ITW) technique which enables it to interpret the variations in fluid and thermal parameters in the near-wall regions without adopting the wall functions. The simulation involves a turbulent offset jet ejecting out of a nozzle at a Reynolds number of 15000, submerged into a stationary environment of Prandtl number 7. The plate at its bottom is heated by constant flux. The various parameters taken into account for observing the thermal behavior are offset ratios (OR=3, 7, and 11), plate velocity ratios (Up=0, 0.5, 1.0, 1.5, and 2), plate thickness ratios (S=0.5, 1.0, and 1.5), and conductivity ratios (K=500, 1000, 1500, and 2000). The temperature distribution diagrams reveal the effect of the parameters mentioned above. The interface temperatures and the Nusselt number suggest better cooling can be achieved at lower offset ratio cases for low-velocity ratios. The contour diagrams and variation of average and local Nusselt numbers suggest the dominating effect of plate motion. A more effective cooling rate is achieved at higher plate velocity, irrespective of the offset ratios.