Solar convective drying kinetics and sorption isotherms of Citrus aurantium flowers

[EN] Citrus aurantium flowers are high value aromatic and medicinal plants. The storage conditions and quality of dried Citrus aurantium flowers depends on their hygroscopic stability. The equilibrium moisture content was determined at temperatures (from 30 to 60 °C), and the sorption phenomenon is well described by Peleg model. The optimal water activity for the storage of the product was estimated at awop=0.373. Afterwards, the net isosteric heat was evaluated in the range of 88 kJ.mol−1 for small values of the moisture content (Xeq=0.14kg water/kg d.b), and it decreased along with the increase of Xeq. The experimental drying curves showed only a falling rate period. Finally, Midilli-Kucuk model was found to be the more suitable to describe the drying kinetic of Citrus aurantium flowers.This work was supported by the research institute IRESEN and all of the authors are grateful to the IRESEN for its cooperation.El Ferouali, H.; Zoukit, A.; Doubabi, S.; Abdenouri, N. (2018). Solar convective drying kinetics and sorption isotherms of Citrus aurantium flowers. En IDS 2018. 21st International Drying Symposium Proceedings. Editorial Universitat Politècnica de València. 965-972. https://doi.org/10.4995/IDS2018.2018.7656OCS96597

Multivariable modeling of an innovative hybrid solar-gas dryer

[EN] The main goal of this paper, is to propose a multivariable control model (MM) issued from CFD study of an innovative hybrid solar-gas dryer to simulate the drying chamber temperature in three modes of operation: Solar mode, Gas mode and hybrid mode. There is an indirect heating of drying air instead of direct heating inside the drying chamber. The air temperature obtained by CFD is still closed to one obtained by multivariable model (MM) with an RMSE under 2.31. the proposed multivariable model leads to a quick output parameters estimation related to each clilmate conditions and so, to an easy control of a hybrid solar dryer.This work was supported by the research institute for solar energy and new energies (IRESEN) as part of the project SSH and all of the authors are grateful to the IRESEN institute for its cooperation.Zoukit, A.; Elferouali, H.; Salhi, I.; Doubabi, S.; Abdenouri, N. (2018). Multivariable modeling of an innovative hybrid solar-gas dryer. En IDS 2018. 21st International Drying Symposium Proceedings. Editorial Universitat Politècnica de València. 371-378. https://doi.org/10.4995/IDS2018.2018.7523OCS37137

Hybrid solar-gas-electric dryer optimization with genetic algorithms

[EN] To promote the hybrid solar dryers for use even under unfavorable weather and to overcome the intermittance state issue, the energy consumption should be optimized and the response time should be reduced. This work concerns a drying chamber connected to a solar absorber where the air can be heated also by combustion of gas and by electric resistance. To optimize the control parameters, an evolutionary optimization algorithm simulating natural selection was used. It was combined with a predictive model based on the artificial neural networks (ANN) technique and used as a fitness function for the genetic algorithm (GA). The ANN is a learning algorithm that needs training through a large dataset, which was collected using CFD simulation and experimental data. Then a GA was executed in order to optimize two objectives: The energy consumption and the t95% response time in which the drying chamber temperature reaches its set point (60°C). After optimization, a 30% decrease of the t95% response time, and 20% decrease of the energy consumption were obtained.This work was supported by the research institute IRESEN and all of the authors are grateful to the IRESEN for its cooperationEl Ferouali, H.; Gharafi, M.; Zoukit, A.; Doubabi, S.; Abdenouri, N. (2018). Hybrid solar-gas-electric dryer optimization with genetic algorithms. En IDS 2018. 21st International Drying Symposium Proceedings. Editorial Universitat Politècnica de València. 363-370. https://doi.org/10.4995/IDS2018.2018.7521OCS36337

Solar drying, hygroscopic equilibrium and biochemical quality of Punica granatum legrelliae’s flowers

Punica granatum Legrelliae is a valuable medicinal plant that is widely planted in Morocco. The equilibrium moisture content was investigated. Peleg model was found the most suitable to describe the sorption phenomenon. The drying kinetic of Punica granatum Legrelliae’s flowers was investigated by using a convection solar dryer. Midilli-Kucuk model described well the drying curves’ trend. The effective moisture diffusivity values were obtained. The Arrhenius relation, with an activation energy value of 92.91 kJ.mol-1 expressed the temperature effect on the diffusion coefficient. Finally, the effect of drying these flowers at different temperatures on their quality was investigated. To assess the quality of the product after solar drying; the color, polyphenols content, antioxidant activity, and polyphenoloxydase and peroxydase activities were considered. 40 °C was the best drying temperature for the preservation of color and bioactive molecules with antioxidant property

Extraction par voie thermique du soufre present dans les minerais de type pyrrhotite Fe_1_-_xS

SIGLEAvailable from INIST (FR), Document Supply Service, under shelf-number : T 78762 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Advanced cascade control strategy applied to an indirect hybrid solar-gas dryer: Numerical and experimental investigations

International audienceIn this paper, a cascade control strategy is applied to control the temperature inside a hybrid solar-gas dryer. In order to use the dryer even at night and in unfavorable weather conditions, the drying chamber is heated by two systems. The first one is the solar air heater and the second one is the gas heater. The solar collector heater is relatively slow compared to the gas heating system. Static and dynamic studies were established and haverevealed the nonlinear behavior of each dryer subsystem. The cascade control approach was developed to control the drying temperature at different setpoints in a temperature range of [50 °C, 90 °C] by managing the gas flow delivered to burners according to received solar energy. Simulation tests followed by experimental investigations have revealed that the proposed control strategy has been able to fulfill the desired dryer performances at different temperatures level, with apropitious steady-state error, reduced overshoot, and a fast transient settling time. Hence, for controlled temperatures at 60 °C, 70 °C, and 80 °C temperatures, the following performances were respectively obtained: a steady-state error of 0.5%, 0.28%, and 1.28%, an overshoot of 2.6%, 4.1%, and 2.5%, and a settling time of 20 min, 18 min, and 30 min. The developed control approach has shown also an effective perturbance rejection during the dryer operation. The proposed controltechnique and the manufactured kit can be easily integrated into hybrid dryers and it’s an adequate and compatible solution with solar dryers for a drying operation of wide agro-food products. This solution also makes it possible to optimize the energy consumption of the secondary source

Model identification and fuzzy control of the temperature inside an active hybrid solar indirect dryer

International audienceIn this paper, an indirect hybrid solar-electric dryer was used to be able to dry a wide range of agriproducts and to ensure a continuous drying operation. The hybrid dryer is a multivariable system made up of a solar collector, a drying chamber, a fan in the outlet duct, and electrical resistance heaters. To preserve the product quality, the temperature should be kept within a restricted temperature range during the drying process. Temperature control is also required to optimize the conventional energy demand and to achieve better use of the available solar energy. This paper presents the thermal behavior study and the control of the temperature inside a hybrid solar dryer. To predict the temperature evolution in a fairly short time, a state-space model based on the nonlinear least square method was developed. Based on the temperature prediction model, Fuzzy Logic Controller (FLC) was developed and its performances were compared with a Proportional Integral (PI) temperature controller. The experimental tests were carried out under an air mass flow rate of 0.025 kg/s and the temperature was controlled at 60 • C and 80 • C. By using this combination, the static temperature inside the drying chamber remains under 0.8 • C and the relative error remains under 1.04%. The developed fuzzy controller could almost recover the dryer performances in less than 8 min after temperature disturbance. Moreover, for continuous use covering day and night, the temperature controller allows reducing the conventional energy consumption by 11.3%

Thermal management of an unloaded hybrid dryer by generalized predictive control

International audienceThe temperature control inside a hybrid dryer has always remainedthe main concern in drying applications. At present, the majorityof the drying community researchers use classical controllers tocommand the thermal environment inside the drying chamber. Such acontrol strategy leads to diminish the dryer efficiency and altersthe quality of the dried products. In this regard, the objective ofthis work is to develop an advanced temperature control system forthe thermal management of a hybrid solar-electrical dryer. Inaddition, the proposed system must be convenient, efficient, andaffordable in developing countries. A Generalized PredictiveController (GPC) is designed and validated for temperature controlcovering a wide range of 40 °C–75 °C. Mathematical and identifiedmodels are developed to represent the thermal behavior of thedryer. The identified linear model is used to design the GPCcontroller. This controller has proven great feasibility andeffectiveness by maintaining the chamber temperature with asettling time that remained under 22 min, with a static error of0.5 °C and no overshoot or dips. Moreover, the GPC algorithm isimplemented with an Arduino board which represents an easy, andlow-cost solution for temperature control in drying applications

Effect of burner’s configuration on the temperature profile inside an innovative solar-gas dryer: Numerical and experimental investigations

International audienceThe main purpose of this work is the optimization of a novel hybrid solar gas dryer. The hybrid dryer was made up of a drying chamber and an innovative solar-gas collector. The gas system consisted of three gas burners incorporated below the absorber as follows: in the bottom, the middle, and the top sides. Each burner is independently controlled for activation and deactivation. Given this distribution, seven configurations of the burners were possible (Top burner (T b), Middle burner (M b), Bottom burner (B b), Top-middle burners (T-M bs), Top-Bottom burners (T-B bs), Middle-Bottom (M-B bs), Top-Middle-Bottom (T-M-B bs)). This work aims to figure out the suitable configuration of the burners and to optimize their placements inside the solar-gas collector. Numerical simulations followed by experimental investigations were conducted in a transitory and steady-state. It was concluded that for the same consumed gas power, the highest temperature (95.6 • C) was achieved by activating the middle burner (M b) while the lowest temperature (74.1 • C) was obtained by activating the top-bottom burners (T-B bs). Further, it turned out that the highest temperature could be obtained by concentrating the burners in the middle side of the solar-gas collector. The obtained results have helped to enhance the efficiency of the proposed hybrid solar-gas dryer