Abstract
The natural convection heat losses occurring from cubical open cavities are analysed in this paper. Open cubical cavities of sides 0.1 m, 0.2 m, 0.25 m, 0.5 m, and 1 m with constant temperature back wall boundary conditions and opening ratio of 1 are studied. The Fluent CFD software is used to analyse the three-dimensional (3D) cavity models. The studies are carried out for cavities with back wall temperatures between 35°C and 100°C. The effect of cavity inclination on the convective loss is analysed for angles of 0° (cavity facing sideways), 30°, 45°, 60°, and 90° (cavity facing vertically downwards). The Rayleigh numbers involved in this study range between 4.5 × 105and 1.5 × 109. The natural convection loss is found to increase with an increase in back wall temperature. The natural convection loss is observed to decrease with an increase in cavity inclination; the highest convective loss being at 0° and the lowest at 90° inclination. This is observed for all cavities analysed here. Nusselt number correlations involving the effect of Rayleigh number and the cavity inclination angle have been developed from the current studies. These correlations can be used for engineering applications such as electronic cooling, low- and medium-temperature solar thermal systems, passive architecture, and also refrigeration systems.
Highlights
Buoyancy-driven heat transfer is one of the most important heat loss mechanisms from open cavities and is widely studied due to their applications in many engineering fields such as solar thermal conversion, refrigeration, passive architecture, fire research, and electronic equipment cooling
Chakroun [17] studied the effect of different wall boundary conditions on the natural convection heat transfer from an open cavity
Nusselt number correlations have been proposed for open cavities with a constant temperature back wall boundary condition, but their use is limited to 0∘ inclination and low Rayleigh numbers
Summary
Buoyancy-driven heat transfer is one of the most important heat loss mechanisms from open cavities and is widely studied due to their applications in many engineering fields such as solar thermal conversion, refrigeration, passive architecture, fire research, and electronic equipment cooling. Mohamad [34] and Polat and Bilgen [35] have analysed upward facing cavities with constant heat flux back wall boundary condition These studies [24, 34, 35] indicate a weak effect of the inclination angle on the convective losses. Nusselt number correlations have been proposed for open cavities with a constant temperature back wall boundary condition, but their use is limited to 0∘ inclination and low Rayleigh numbers In this communication, numerical studies of natural convection heat transfer from open cubical cavities of sides 0.1 m, 0.2 m, 0.25 m, 0.5 m, and 1 m are carried out. Nusselt number correlations that involve Rayleigh numbers and the inclination effects are proposed These correlations can be used for engineering applications such as electronic cooling, low- and medium-temperature solar thermal systems, passive architecture, and refrigeration systems
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