

Articles
by
A. Belghith 
Total Records (
6 ) for
A. Belghith 





M. Lazaar
,
S. Kooli
,
M. Hazami
,
A. Farhat
and
A. Belghith


The problem of temperature inversion is one of solar origin principal problems about which the cultures under shelters complain. Indeed, for the winter period, the temperature under greenhouse is very low at night and it is rather high during the day in summer. Consequently, the heating of the greenhouses is essential. In this work, we studied the advisability of using two exchangers coupled between them to manage thermal energy in a greenhouse. The first system is a battery of plaits with capillary tubes buried under ground with a depth of 70 cm. The second is an air exchanger based on plastic tubes black known as agrotherms suspended with two meters and half height. The hot water, which circulates in the exchangers, is provided by the hotwater tank of the electrosolar power station of the Center of Energy Researches and Technologies (CRTEn) from Tunisia. 




M. Lazaar
,
S. Kooli
,
M. Hazami
,
A. Farhat
and
A. Belghith


The problem of temperature inversion is one of solar origin principal problems about which the cultures under shelters complain. Indeed, for the winter period, the temperature under greenhouse is very low at night and it is rather high during the day in summer. Consequently, the heating of the greenhouses is essential. In this work, we studied the advisability of using two exchangers coupled between them to manage thermal energy in a greenhouse. The first system is a battery of plaits with capillary tubes buried under ground with a depth of 70 cm. The second is an air exchanger based on plastic tubes black known as agrotherms suspended with two meters and half height. The hot water, which circulates in the exchangers, is provided by the hotwater tank of the electrosolar power station of the Center of Energy Researches and Technologies (CRTEn) from Tunisia. 




Y. Jellouli
,
R. Chouikh
,
A. Guizani
and
A. Belghith


We present an analysis of the melting process in Phase Change Materials (PCM) in a horizontal cavity heated from below, driven by the coupling of transient heat conduction in the solid phase and steady state laminar natural convection in the liquid phase with one of the boundaries of the solution domain that moves. We state the problem in the Cartesian coordinate system; involve the use of a control volume method to solve the full vorticity equation together with the stream function and energy equation. The moving boundary was linearized by a coordinate transformation and immobilized in step time calculation. The results show that the melting front was stabilized at a well defined position when the steady state was reached and the higher solid phase was preserved. 





J. Sghaier
,
S. Messai
,
D. Lecomte
and
A. Belghith


Problem statement: Drying a packed bed of porous particle at high temperature with varying humidity of hot air is an attractive process. Many researches on experimental and simulation on a fixed bed drying at low and average temperature are proposed. Few studies showed drying at high temperature with humid air or using superheated steam. The latest is compared to dry air. Approach: In this study, we present an experimental and numerical study of humid air drying of a fixed bed of moist porous alumina particles. The air velocity, the air temperature and the vapor pressure were varied from 1.72.3 m sec^{1}, 120160°C and 0.10.6 bar, respectively and the experiments were performed at atmospheric pressure. Then a mathematical model describing heat and mass transfer during drying is developed. This model is based on the averaging volume approach using two scale changes. Results: From the experimental works, the solid temperature and the bed moisture content have been presented at different drying conditions. The previous results show that an increase in humidity leads to an increase of the wet bulb temperature and a decrease in the drying time. At the same drying temperature, the variation in the gas velocity affects also the drying time. In addition, we note that the drying time increases if the bed depth increases. The predicted results deduced from the developed model were compared with the experiment. Conclusion: The experimental and predicted results obtained from this study describing drying of a packed bed illustrate clearly the effect of the air humidity on the drying kinetics. 





A. O. M. Mahmoud
,
J. Zinoubi
,
R. Ben Maad
and
A. Belghith


The dispersion of pollutants, resulting from industrial chimneys, in the surrounding atmosphere made the interest in realizing emitting conditions appears. It also encourages the vertical dispersion of these pollutants. At a given wind velocity, the height of this dispersion is essentially a function of the thermal power and the flow rate at the chimney exit. To improve these qualities, we propose a system that could be integrated to the industrial chimney exit. An openended vertical cylinder of larger diameter essentially constitutes this system. In order to determine the characteristics of the resulting flow, we simulated the problem in the laboratory while studying the evolution of a free thermal plume generated by a disk heated uniformly by the Joule effect at a constant temperature. The thermal plume expands in a quiet environment of isotherm temperature. To study the thermosiphon effect, we surrounded the plume source by a vertical cylinder opened at the extremities. Thermal radiation emitted by the hot disk heats the cylinder wall. The pressure drop due to the acceleration of the flow at the cylinder inlet causes the appearance of thermosiphon effect around the thermal plume. The analysis of the average fields of velocity and temperature shows that the thermosiphon effect entails a good homogenization of the flow at the system exit. Furthermore, the comparison of the results obtained at the exit of the two studied systems shows a relative increase of the flow rate and the thermal power absorbed by the air of the order of 50% under the thermosiphon effect. This result is expressed by a gain in the plume rise of the order of 40%. 





M.M. Ould Dah
,
M. Ouni
,
A. Guizani
and
A. Belghith


The performance and stability of a 0.64 m^{2} mini solar pond were experimentally and numerically studied. The experimental results showed that the daily average temperatures of the mini pond increased quickly to reach 54 °C in the lower convective zone after only 20 days. A 1 D numerical model to predict the temperature and the salinity in the mini pond was developed. The results obtained from the numerical calculation were compared with our experimental results and good agreement was found. Therefore a new method of heat extraction from the non convective zone was numerically investigated in order to enhance the mini pond performance. Using this new method of heat extraction, the numerical results showed that the mini pond efficiency could be considerably improved. However, the method was found to reduce the stability of the lower interface. 





