Aspect ratio effect on natural convection flow in a greenhouse submitted to a geothermal heat source
Authors: Yassine Slatni, Brahim Mahfoud, Tarek. Messai, Mahfoud. Djezzar
Volume 11, Issue 1, Paper No. 110101
Abstract
The study of how greenhouse dimensions affect heat transfer and convection is pivotal in refining greenhouse design for optimal plant growth. In this context, this paper presents the aspect ratio effect on natural convection flow within a tunnel greenhouse is undertaken. During the winter season, the base of the greenhouse is subjected to geothermal energy to maintain a temperature Th, while the roof is exposed to a lower temperature Tc. The principal flow attributes are defined by a pair of dimensionless parameters: the aspect ratio (f=K/L) and the Rayleigh number (Ra). The effects of Rayleigh number which varies from 103≤Ra≤106 as well as the aspect ratio between 0.6≤f≤1 were investigated. A numerical approach in bipolar coordinates is suggested, utilizing an implicit finite volume formulation.
The findings are visualized through streamlines and isotherms contours. Profiles for average and local Nusselt numbers, as well as distributions of temperature and velocity, are also presented. The conclusions indicate that in scenarios featuring minor temperature disparities between the greenhouse interior and exterior, heat transfer is predominantly governed by pseudo-conduction. However, with an increase in the temperature difference, natural convection emerges as the dominant heat transfer mechanism, leading to an enhancement in heat transfer efficiency. Moreover, the aspect ratio of the greenhouse demonstrates a proportional correlation with internal heat transfer efficiency. These insights offer valuable direction for the optimization of greenhouse design and operation.
Keywords: Aspect ratio; Greenhouse; Geothermal energy; Bipolar coordinates; Nusselt number; Plant growth
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