Articles
A DYNAMIC MODEL FOR THE DETERMINATION OF THERMAL BOUNDARY CONDITIONS IN THE GROUND OF A GREENHOUSE
Article number
719_33
Pages
295 – 302
Language
English
Abstract
This paper deals with the description of a semi analytical model built to predict the temperature and heat flux conditions at the ground level of a greenhouse.
The objective of this work is to provide these as boundary conditions for use in a CFD model for the accurate determination of the climatic conditions in a greenhouse. The main source of energy contained in the ground comes from the solar radiation which may fluctuate considerably depending on the daytime, place, season, clearness of the sky and albedo of the surface.
In the ground, the heat transfer depends on its physical properties, compactness and moisture.
The ground is a porous environment which contains air and water at variable quantities in the interstices, which makes heat transfer analysis by conduction much more complicated than in homogeneous solid bodies.
The temperature profile resulting from the heat balance at the surface depends on the thermal diffusivity of the soil.
Many works use the average value of this physical characteristic by regrouping parameters for estimating the temperature profile. In this study, we are concerned withy the estimation of the ground response for some known transient ambient environment conditions (solar radiation, temperature, hygrometry and wind speed). Using a semi-analytical method, the ground temperature profile is determined from weather parameters and the ground characteristics.
This method helps in evaluating the heat flux exchanged between the ground surface and the ambient air; this procedure differs from other procedures which consider a steady state average value of the heat flow.
The objective of this work is to provide these as boundary conditions for use in a CFD model for the accurate determination of the climatic conditions in a greenhouse. The main source of energy contained in the ground comes from the solar radiation which may fluctuate considerably depending on the daytime, place, season, clearness of the sky and albedo of the surface.
In the ground, the heat transfer depends on its physical properties, compactness and moisture.
The ground is a porous environment which contains air and water at variable quantities in the interstices, which makes heat transfer analysis by conduction much more complicated than in homogeneous solid bodies.
The temperature profile resulting from the heat balance at the surface depends on the thermal diffusivity of the soil.
Many works use the average value of this physical characteristic by regrouping parameters for estimating the temperature profile. In this study, we are concerned withy the estimation of the ground response for some known transient ambient environment conditions (solar radiation, temperature, hygrometry and wind speed). Using a semi-analytical method, the ground temperature profile is determined from weather parameters and the ground characteristics.
This method helps in evaluating the heat flux exchanged between the ground surface and the ambient air; this procedure differs from other procedures which consider a steady state average value of the heat flow.
Publication
Authors
R. Nebbali, S. Makhlouf, T. Boulard, J.C. Roy
Keywords
greenhouse, ground, heat transfer, heat flux, Fluent, temperature
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