Abdelghani Boubekri

Softening of Overdried ‘Deglet Nour’ Dates to Obtain High-Standard Fruits: Impact of Rehydration and Drying Processes on Quality Criteria

The postharvest hydrothermal treatment of date palm fruit was studied in order to enhance the quality and consumer acceptance of ‘Deglet Nour’ hard dates, because these dates are unfit for direct consumption. Hot water hydration was performed by soaking at 25, 45, and 65°C and convective hot air drying at 35, 45, 60, 75, and 85°C at various levels of air humidity. Numerous quality parameters—i.e., texture, color, moisture and sugar contents—were investigated. Artificial maturation due to the softening of texture and the equilibration of sugars was achieved using the hydration pretreatment. A 6-h soaking at 45°C could be the best option to obtain a product of highest quality, but the moisture content would exceed that required for safe storage. Drying and quality tests led to the selection of a pretreatment step of soaking at 30°C for 8 h, followed by drying at an intermediate temperature (60°C) as the optimum condition to obtain a final product of high quality with the standard moisture content of 0.35 kg/kg d.b.

Étude du traitement thermique à l’eau chaude en vue d’amélioration de la qualité des dattes sèches

Une etude experimentale de la rehydratation, par impregnation a l’eau chaude, de la datte Deglet-Nour a ete faite en vue d’ameliorer la qualite des dattes seches. A cet effet plusieurs parametres de qualite ont ete testes simultanement : humidite, sucres, texture et couleur afin de permettre une bonne appreciation du produit fini. Differents echantillons ont ete rehydrates a 25, 45 et 65°C dans des solutions d’eau pure sucrees a 0°, 10° et 20° Brix. Les resultats obtenus ont mis en evidence une maturation complementaire par prise en eau et inversion de sucres. Le phenomene de diffusion eau-datte a ete accelere par l’augmentation de la temperature de trempage mais celui-ci a ete freine par l’augmentation de concentration des solutions sucrees et les pertes de sucres dans la solution de trempage etaient negligeables. Parmi plusieurs conditions operatoires investies, le trempage a 30°C, pendant environs huit heures, a ete choisi comme traitement optimal pour un produit fini de meilleure qualite. Afin de restituer au produit sa teneur en eau normale pour un stockage sain, une operation complementaire de sechage peut etre proposee.

Thermal behavior modeling of a cabinet direct solar dryer as influenced by sensible heat storage in a fractured porous medium

Numerical simulation method has been employed to improve the thermal performance of cabinet direct solar dryer. The present study focused on the numerical simulation of a direct solar dryer with integration of a flat layer of fractured porous medium above the absorber plate in the aim to store thermal energy by sensible heat. Several calculations were conducted, using the finite volume method with a two-dimensional unsteady model implemented in the Fluent CFD software. The porous medium has been integrated with different thickness to show the influence of the medium thickness on the thermal performance of solar dryer. Different kinds of materials have been tested and studied. The effect of porosity of porous medium has been studied. The obtained results showed that the temperature of drying air is increased by 4°C with integration of porous medium. The increasing in the thickness of the porous medium by 1cm leads to increase the temperature of drying air by 2°C. The increasing of the medium porosity by 10% leads to decrease the temperature of drying air by 1°C. The best material is the one that has a highest specific heat and thermal conductivity.Numerical simulation method has been employed to improve the thermal performance of cabinet direct solar dryer. The present study focused on the numerical simulation of a direct solar dryer with integration of a flat layer of fractured porous medium above the absorber plate in the aim to store thermal energy by sensible heat. Several calculations were conducted, using the finite volume method with a two-dimensional unsteady model implemented in the Fluent CFD software. The porous medium has been integrated with different thickness to show the influence of the medium thickness on the thermal performance of solar dryer. Different kinds of materials have been tested and studied. The effect of porosity of porous medium has been studied. The obtained results showed that the temperature of drying air is increased by 4°C with integration of porous medium. The increasing in the thickness of the porous medium by 1cm leads to increase the temperature of drying air by 2°C. The increasing of the medium porosity by 10...

A simulation study of a solar collector using phase change materials for air heating application needs

Numerical simulation method has been employed to improve thermal performance of plan solar collectors, and to increase their daily operation length. The present study focused on the numerical simulation of a solar collector with integration of a flat layer of phase change material in the aim to store thermal energy by latent heat. Several calculations were conducted, using the finite volume method with a two-dimensional unsteady model implemented in the Fluent CFD software. It was found that the integration of 1cm of PCM layer below the absorber plate increases the collector daily operating length with 2 hours and improves the outlet temperature with a value of 10°C after sunset. The PCM with melting temperature of 345K gave the best temperature at the collector outlet.Numerical simulation method has been employed to improve thermal performance of plan solar collectors, and to increase their daily operation length. The present study focused on the numerical simulation of a solar collector with integration of a flat layer of phase change material in the aim to store thermal energy by latent heat. Several calculations were conducted, using the finite volume method with a two-dimensional unsteady model implemented in the Fluent CFD software. It was found that the integration of 1cm of PCM layer below the absorber plate increases the collector daily operating length with 2 hours and improves the outlet temperature with a value of 10°C after sunset. The PCM with melting temperature of 345K gave the best temperature at the collector outlet.

An Experimental Study on the Drying of Peanuts Using Indirect Solar Dryer

An indirect type natural convection solar dryer is designed, constructed, and investigated experimentally to study the drying of peanut (Arachis hypogaea L.) under the weather conditions of Ouargla, Algeria.