Effect of Slot Jet Temperature on Impingement Heat Transfer Over a Heated Circular Cylinder

In this paper, heat transfer and effectiveness of a turbulent slot jet impinging over a heated circular cylinder have been investigated numerically by varying the ratio of jet temperature to the ambient temperature, Theta(j) = T-j/T-amp, from 0.7 to 1.2. In all cases, the ambient temperature (T-amb) is assumed to be constant (300 K). The Reynolds number defined based on the average nozzle exit velocity, the diameter of the cylindrical target (D), and properties at the nozzle exit temperature, Re-D = rho VD/mu is varied from 6000 to 20,000. The ratio of cylinder diameter to the slot width, D/S = 5.5, 8.5, and 17 are considered and the nondimensional distance from the nozzle exit to the cylinder, H/S is varied in the range of 2 <= H/S <= 12. The v'(2) - f turbulence model was used for numerical simulations. Numerical results reveal that the local Nusselt number is found to be higher at the stagnation point in the case of cold jet impingement at Theta(j) = 0.7. The local heat transfer at the rear side of the cylinder is 8-18% less as compared to that of Theta(j) = 1.0 for Re-D = 6000. The local effectiveness calculated over a circular cylinder strongly depends on H/S and D/S. Based on the parametric study, a correlation has been provided for the local effectiveness at the stagnation point.