An experimental investigation of mixed convection heat transfer in a rectangular enclosure
Fisher, Daniel Edward
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https://hdl.handle.net/2142/22513
Description
Title
An experimental investigation of mixed convection heat transfer in a rectangular enclosure
Author(s)
Fisher, Daniel Edward
Issue Date
1995
Doctoral Committee Chair(s)
Pedersen, Curtis O.
Department of Study
Mechanical Engineering
Discipline
Mechanical Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Civil
Engineering, Mechanical
Language
eng
Abstract
Mixed convection heat transfer was studied in a well instrumented, office size, rectangular enclosure. Surface and air temperatures were measured, convective heat fluxes were calculated, significant parameters were identified, and Nusselt number correlations were developed for various flow field and surface temperature configurations. Buoyant, mechanically driven wall and free jets were investigated over a range of room inlet conditions. The experiments were performed in both isothermal and non-isothermal room configurations.
The mixed convection experiments were bounded by forced convection experiments in an isothermal room and natural convection experiments in a non-isothermal room. At the isothermal, forced convection limit, the dimensionless heat transfer coefficient is correlated to the turbulent enclosure Reynolds number: Nu $\sim$ Re$\sp{0.8}$. The enclosure Reynolds number, based on the volumetric flow rate of the jet, successfully predicts the Nusselt number for both the wall jet and the free jet in the isothermal room over a wide range of ventilative flow rates. At the natural convection limit, the Nusselt number correlates to the Rayleigh number as expected, with Nu $\sim$ Ra$\sp{0.25}$.
The mixed convection heat transfer model is based on the enclosure Reynolds number, the Rayleigh number, the Archimedes number and a characteristic jet temperature. The model successfully predicts the mixed convection Nusselt number for a ceiling diffuser over the entire range of volumetric flow rates, inlet air temperatures and surface temperatures tested.
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