| Summary: In this study, two-dimensional steady-state laminar natural convection in rectangular enclosures with differentially heated sidewalls has been studied numerically and theoretically where the enclosure is considered to be completely filled with non-Newtonian fluids obeying the Bingham and power-law models. Yield stress effects on heat and momentum transport are investigated for nominal values of Rayleigh number (Ra) in the range 103-106, Prandtl number (Pr) in the range of 0.1-100 and aspect ratio range 1/8 to 8 for Bingham fluid. The effects of power-law index in the range 0.6 ≤ n ≤ 1.8 on heat and momentum transport are also investigated for nominal values of Prandtl number (Pr) range of 10-105, Rayleigh number (Ra) in the range 103-106 and aspect ratio range 1/8 to 8 in the case of power-law fluids. Scaling analysis are performed to elucidate the anticipated effects of aspect ratio, Rayleigh number, Prandtl number, Bingham number and power-law index on the Nusselt number for both Bingham and power-law fluids. New correlations are proposed for the mean Nusselt number for Newtonian, Bingham and power-law fluids. Finally, an application study on thermal control of concentred photovoltaic (CPV) systems has been established to indicate the importance of natural convection of non-Newtonian fluids in rectangular enclosures in term of the engineering practises.
Key Words: Natural Convection, Heat Transfer, Laminer Flow, Bingham Model, Power-Law Model
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