Influence of exit angle on radial jet reattachment and heat transfer

Abstract

Flowfield and heat transfer have been computed for impinging laminar, semienclosed axial, and vectored radial jets. A finite volume computational scheme based on SIMPLEC has been developed to solve the NavierStokes and energy equations. The present scheme can handle backflow at the exit of the computational domain. The results show that the axial jets produce larger heat transfer on a small area, and the radial jets produce moderately large transfer on larger areas. Through the vectoring of the radial jets, the area of high transfer can be selected as wanted. Axial jets always give larger peak heat transfer on the point of impingement than the radial jet on the impingement circle. This peak value for radial jet increases with the increasing angle of the jet inclination. At some critical value of the jet inclination (60 deg for the present geometry and the Reynolds number) the total heat transfer on the impingement surface can be larger for the radial jet than for the axial jet. Radial jets with an angle of inclination of 0 deg or less can produce a suction force on the impingement surface. Such jets can be used for transport of the product surfaces and heat or mass transfer on the surface at the same time. Nomenclature a = temperature diffusivity H = height of the confining wall h = height of the jet from the impingement surface L = radius of the impingement surface Nu = Nusselt number Pr = Prandtl number p = pressure R = radius of the feed tube Re = Reynolds number r = radial coordinate T = temperature t = time u = axial velocity v = radial velocity x = axial coordinate A = thermal conductivity of the fluid JJL = kinematic viscosity v = dynamic viscosity p = density Subscripts av = average value in = inlet w = impinging surface