On the cooling effect of an air jet along the surface of a cylinder

Heat transfer of slot jets of air impinging on the surface of a circular cylinder by forced convection has been investigated. The cylinder has a diameter of D=10 mm and the slot jet has a height of S=5 mm. The thermocouples, located along the surface of the cylinder, at various angles from the impinging point, allow the evaluation of the local convective heat transfer coefficients. The experiments have been performed for a Reynolds number of the impinging air ranging from Re=4000 to Re=20000. The influence of the distance H, between the exit of the slot jet and the cylinder, has been investigated in the range of H/S, H/S=2–10. The local Nusselt number is a function of the H/S ratio and of the angle from the front impinging point. It is also dependent on the Reynolds number.