Analysis of Transient Conjugate Heat Transfer to a Free Impinging Jet

Transient conjugate heat transfer during the impingement of a freejet of high Prandtl number e uid on a solid disk of e nite thickness is considered. When power is turned on at t =0, a uniform heat e ux is imposed on the disk surface. The numerical model considers both solid and e uid regions. Equations for the conservation of mass, momentum,andenergy aresolvedintheliquidregion,withthetransportprocessesattheinletand exitboundaries, as well as at the solid ‐liquid and liquid ‐gas interfaces taken into account. In the solid region, only heat conduction equation is solved. The shape and location of the free surface (liquid‐gas interface ) is determined iteratively as a part of the solution process by satisfying the kinematic condition as well as the balance of normal and shear forces at this interface. Computed results include the velocity, temperature, and pressure distributions in the e uid and the local and average heat transfer coefe cients at the solid ‐e uid interface. Computations are carried out to investigate the ine uence of different operating parameters such as jet velocity, disk thickness, and disk material. Nomenclature b = thickness of the disk, m cp = specie c heat at constant pressure, kJ/kg ¢ K dn = diameter of the nozzle, m Fo = Fourier number, a ft/d 2 n g = acceleration due to gravity, m/s 2 Hn = distance of the nozzle from the disk, m h = heat transfer coefe cient, qint/(Tint i Tj), W/m 2 ¢ K hav = heat transfer coefe cient, W/m 2 ¢ K:

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