Mixed convection heat transfer from discrete heat sources mounted in a rectangular duct

Howard Victor Mahaney, Purdue University

Abstract

Experiments and supporting 3-D numerical computations have been performed for water and FC-77 to investigate mixed convection heat transfer from a four-row, in-line array of twelve, square heat sources which are flush mounted to the lower wall of a horizontal, rectangular channel. The experimental data encompass heat transfer regimes characterized by natural convection, mixed convection, laminar forced convection, and the initiation of transition to turbulence. The variation of the row-average Nusselt number with Reynolds number exhibits a minimum, suggesting that, due to buoyancy-induced flow, heat transfer may be enhanced and pumping power requirements may be reduced by reducing the flow rate. Experiments and supporting 3-D numerical computations have also been performed for FC-77 and a heat source array whose surface area is augmented by the use of longitudinal fins. The experimental data indicate that the first heater row is forced convection dominated, while data for rows 2-4 encompass heat transfer regimes characterized by natural convection (row 4 only), mixed convection, and transition to turbulence. Although the variation of the row-average Nusselt number with Reynolds number for the flush mounted results exhibits a minimum, the row-average Nusselt number for the finned results decreases monotonically with decreasing Reynolds number for rows 1-3, and becomes nearly independent of Reynolds number for row 4. Increasing the Rayleigh number, for the unfinned and finned arrays, enhances heat transfer and increases the Reynolds number range for which enhancement occurs. Appropriate scaling parameters are introduced for both geometric configurations to characterize mixed convection heat transfer from an array of discrete sources.

Degree

Ph.D.

Advisors

Ramadhyani, Purdue University.

Subject Area

Mechanical engineering

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