Heat Transfer and Temperature Distributions in the Fluid and Cooled Cylindrical Solid during Radial Slot Jet Impingement Cooling

A conjugate heat transfer investigation was conducted to better understand the effects of an impinging radial slot jet cooling device on both the heat transfer rates and temperature fields in the fluid, and especially in the cylindrical solid cooled by this device. Such temperature nonuniformities in the solid are of practical interest as they may result in phenomena such as nonuniform material properties, residual thermal stresses, and distortion of the target shape, and several metrics for this nonuniformity were defined and evaluated. The study used numerical methods to model a configuration in which a set of four radially-positioned slot jets cooled a cylindrical steel target using air with a jet Reynolds number of 20,000. The steady-state vf RANS model was used with a representative two-dimensional section of the axisymmetric target and flow domain. The conjugate heat transfer/CFD model was run for three cases: (1) constant inner surface temperature, (2) constant inner surface heat flux, and (3) constant volumetric heat generation. The target wall thickness and thermal conductivity were varied to study lateral conduction in the solid. Heat source intensity was also varied to assess its influence. Results showed that for Biot (Bi) numbers between 0.0025 and 0.073 the temperature levels in the solid were clearly affected by lateral conduction, and that the temperature variation within the solid was an order of magnitude smaller than the variation in the surface heat transfer coefficient. Despite the relatively large temperature difference of up to 400K between the cooling fluid and the solid surface, the conduction in the solid was found to have a negligible effect on the flow and heat transfer in the fluid, and on the convective heat transfer coefficient on the solid interface. For the constant heat flux case, the area-weighted standard deviation in the solid temperature was found to correlate well with the dimensionless parameter