The draining solar drying is considered as an innovative solution in the field of sanitation. The objective of this work is to investigate the feasibility and model the kinetics of the sludge solar drying in a lab‐scale draining greenhouse by varying the air flow rate during winter and summer. The first experiment was conducted without ventilation. Then, a series of experiences was carried out with increasing the air flow. The drying period varied between 3 and 6 days in summer and between 9 and 14 days in winter. By increasing the air velocity, the drying time decreased. For the drying rate curves, in summer, only the falling rate period existed. However, in winter, the curves did not follow any regular shape of drying kinetics. Nine mathematical equations existing in the literature were tested to identify the thin‐layer drying kinetics of sewage sludge inside the draining greenhouse. The Midilli‐Kucuk model was the most reliable for describing the evolution of reduced moisture content versus drying time in hot and cold periods. However, for different drying conditions, the Wang and Singh model was the least suitable. The results revealed also that the effective diffusivity increased when the air flow rate and the ambient temperature increased.

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International audienceNumerical simulations in a gas turbine Swirl stabilized combustor were conducted to investigate the effectiveness of a cooling system in the protection of combustor walls. The studied combustion chamber has a high degree of geometrical complexity related to the injection system as well as the cooling system based on a big distribution of small holes (about 3,390 holes) bored on the flame tube walls. Two cases were considered respectively the flame tube without and with its cooling system. The calculations were carried out using the industrial CFD code FLUENT 6.2. The various simulations made it possible to highlight the role of cooling holes in the protection of the flame tube walls against the high temperatures of the combustion products. In fact, the comparison between the results of the two studied cases demonstrated that the walls temperature can be reduced by about 800A degrees C by the mean of cooling holes technique

The aim of this work is to investigate and model the sewage sludge drying kinetics in a lab‐scale drying bed by varying the sludge layer thickness during winter and summer. During each season, five experiments were carried out with increasing the sludge thickness by 0.5 cm each time. To achieve moisture content on a dry basis of 12%, the sludge drying period varied between 120 and 312 h in winter and between 72 and 168 h in summer. Thus, by increasing the sludge thickness, the drying time increased. The different curves of the moisture content evolution and the drying rates were analyzed. The drying curves show that the warm‐up phase (phase 0) and the constant rate phase (phase 1) are absent during the winter and summer seasons. Regardless of the sludge thickness, only the falling rate period was observed. In addition, the moisture content dropped quickly throughout the first 24 h because of the elimination of interstitial water. The drying characteristic curve has been represented by a 3rd degree polynomial. Mathematical equations were used to describe the experimental curves of drying kinetics. The logarithmic model was the most reliable for simulating the changes of reduced moisture content versus drying time in winter and summer.