Measurements of heat transfer coefficients between turbulent liquid jets and a radially finned heated disk placed at the bottom of an open vertical circular cavity

Experiments have been performed to assess the impact of an extended surface on the heat transfer enhancement for axisymmetric, turbulent liquid jet impingement on a heated round disk. The disk, with an array of integral radial fins mounted on its surface, is placed at the bottom of an open vertical circular cavity. Hydrodynamic and heat transfer data were obtained for a dielectric fluorocarbon liquid FC-77. For a fixed circular heater of diameter D =22.23 mm, several geometric parameters were tested: the nozzle diameter (4.42≤ d ≤9.27 mm), the confining wall diameter of the vertical cavity (22.23≤ D c ≤30.16 mm), and the nozzle-to-heater spacing (0.5≤ S / d ≤5.0). The FC-77 flow rates varied from =0.2 to 11.0 l/min producing Reynolds numbers in the wide interval 700≤Re d ≤44,000. For d =4.42 mm, the heat transfer response to the separation distance S / d was small but increased gradually with increasing nozzle diameter up to d =9.27 mm. The thermal resistance R th increased with the confining wall diameter D c and also with the nozzle diameter d . A minimum value of the thermal resistance of R th,min =0.4 cm 2 K/W was attained for a combination of d =4.42 mm, D c =22.23 mm, S / d =1, and =7.5 l/min. Based on a simplified heat transfer model, reasonable agreement was obtained between measured values of the thermal resistance and the R th -predictions. The total fin effectiveness ɛ f was shown to increase with increasing nozzle diameter, but was invariant with the flow rate (or the jet exit velocity). More than a three-fold heat transfer enhancement was realized through the addition of the array of integral radial fins on the heated round disk.