Crop cultivation in greenhouses under semi-arid climatic conditions is subject to various stresses, in particular during the winter season at night, when the interior air is poorly controlled, leading to prolonged periods of low temperature. The aim is then to evaluate and control the heat exchanges of the enclosure in order to prevent low indoor air temperatures and reduce the thermal load of the greenhouse. The objectives of this study are to investigate the convective and radiative heat exchanges at the cover in order to establish new correlations for the convective heat transfer coefficients in semi arid regions. The climatic parameters were measured inside and outside a closed empty glasshouse without crop, for three different nights during the winter season in the semi-arid land of Algeria. A physical model for analysing the convective heat transfers was implemented, and new correlations were established, parameterised, calibrated and validated thoroughly. A significant difference was observed between the correlations obtained by this study and the models obtained for other greenhouse designs under different climatic conditions. Results show that the convection mode along the inside wall of the cover is free turbulent. Conversely, the convection mode along the outside greenhouse cover remains forced turbulent. A consistent performance of the correlations was observed, both in the calibration and validation stages.

Heat transfer by convection occurs in various domains such as atmospheric flows, exchangers, passive air conditioning, etc.…For example, in passiveair conditioning, theheat transfer rateat alateral wallof an enclosure can be enhanced if the surface is not flat. Indeed, it is well known that a rough surface allows increasing the heat transfer. Such rough surface can be obtained with the use of protuberances on walls. The purpose of this study is to investigate, numerically in 2D, the effect of rough surfaces at the vertical walls on heat and mass transfers in an enclosure. As boundary conditions, the vertical walls of this enclosure are subject to a uniform heat flux and horizontal walls are supposed to be adiabatic. The numerical modeling, used by us, is briefly described below. The rough surfaces are described as sinusoidal profiles which are transformed, using a homotopic transformation, into a flat plate. Governing equations are discredited using the finite volume method and the resolution is obtained by the THOMAS algorithm. The coupling of the velocity and pressure fields is achieved using the SIMPLE algorithm. The effect ofthe formofprotuberances, and the imposed heat flux at a vertical wall, on streamlines and temperature fields has been considered. The first obtained results are in agreement with previous experimental and numerical results, showing thus that our modeling is accurate. The first results are a validation of code are in agreement with previous experimental, numerical, and software Fluent showingthat our model is accurate