Coupled Effects of Surface-Radiation and Buoyancy on Jet-Impingement Heat Transfer
MetadataShow full item record
This paper delineates the results of an investigation on the combined effects of buoyancy and surface-radiation on heat transfer from an isothermal surface, subjected to a confined submerged impinging air-jet issuing from a slot-nozzle. The nondimensionalized governing equations are solved using the stream function-vorticity approach and an upwind finite-difference technique, employing the radiosity-irradiation formulation for surface-radiation. The effects of jet Reynolds number, dimensionless nozzle-to-heater distance, radiation-flow interaction parameter, Richardson number, and surface-emissivity, on the convective, radiative, and total Nusselt numbers, are analyzed for 100 ≤ Re d ≤ 900, 1 ≤ H ≤ 8, 0.1 ≤ NRF,d ≤ 2, 0.01 ≤ Ri d ≤ 10, and 0.05 ≤ Ɛ 0.85. It was found that the radiation-flow interaction parameter was most influential in affecting the radiative Nusselt number and, hence, the total heat transfer from the impingement surface. In contrast to a substantial enhancement in the net radiative component of the overall heat transfer in both the stagnation region and the regions downstream for an increase in Ɛ over the range considered, the convective counterpart was found to be suppressed. The effect of increase in Rid on the heat transfer in the stagnation region was found to be negligible; however, an adverse effect on the net radiation from the heater was observed.Increase in NRF,d resulted in an increase in contribution of radiation to the total heat transfer by about 25% in the stagnation region, while over 40% in the wall-jet region for low values of H, and to about 15% in the stagnation region to over 50% in the wall-jet region for relatively larger values of H. With increase in H, both convective and radiative Nusselt numbers decreased over most of the upstream regions of the heater, while the magnitude of local radiative Nusselt numbers increased over the regions closer to the outlet. For sufficiently large values of jet Reynolds number or large values of dimensionless nozzle-to-heater distance, a small recirculation region was found to occur over the heater at a certain distance downstream of the stagnation point, where distribution of the contribution of radiation to the overall heat transfer from the heater results in a local maxima reaching about 60–80% for specific combinations of controlling parameters.
Showing items related by title, author, creator and subject.
Abishek, S.; Narayanaswamy, Ramesh; Narayanan, V. (2012)Jet impingement boiling heat transfer is a potential technique for the removal of very high heat fluxes concentrated at discrete locations, such as in power electronic components. In the present research, the effect of ...
Effect of heater size and Reynolds number on the partitioning of surface heat flux in subcooled jet impingement boilingSridhar, Abishek; Narayanaswamy, Ramesh; Narayanan, Vinod (2013)The overall heat transfer rate due to boiling of an impinging subcooled liquid jet is attributed to several simultaneous mechanisms including liquid and vapor phase convection, quenching (transient convection) and ...
Effect of standoff distance on the partitioning of surface heat flux during subcooled jet impingement boilingSridhar, Abishek; Narayanaswamy, R.; Narayanan, V. (2012)Heat transfer involving boiling of impinging jets are used for cooling components that dissipate very large heat fluxes, typically over 100 W/cm2 concentrated at discrete locations. Several industrial applications requiring ...