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Accueil du site → Doctorat → Allemagne → 2010 → Design, development and modeling of a solar distillation system for the processing of medicinal and aromatic plants

University of Kassel (2010)

Design, development and modeling of a solar distillation system for the processing of medicinal and aromatic plants

Munir, Anjum

Titre : Design, development and modeling of a solar distillation system for the processing of medicinal and aromatic plants

Auteur : Munir, Anjum

Université de soutenance : University of Kassel

Grade : Doktor der Agrarwissenschaften 2010

Résumé partiel
Processing of medicinal and aromatic plants by distillation method is one of the agrobased industries which lie in the medium temperature range. Essential oils extracted from these plant materials have been used throughout the world in foods, fragrances, perfumery, cosmetics and medicines and these oils are very expensive. With the introduction of innovative solar collectors, it is possible to use solar energy in the medium temperature range. The study was initiated to develop a de-centralized solar distillation system for the processing of medicinal and aromatic plants for functional, environmental and economic reasons. The system was installed at solar campus, University of Kassel, Witzenhausen, Germany to avail the fresh supply of herbs. Scheffler fixed focus concentrator (8 m2 surface area) was used for solar distillation system. The system comprises of a primary reflector, secondary reflector, distillation still, condenser unit and Florentine flasks. The primary reflector rotates along an axis parallel to the earth axis of rotation and keeps the reflected beam aligned with the fixed secondary reflector as the sun moves. The secondary reflector further reflects the beam radiation to the targeted distillation still bottom. The distillation still was fabricated of a food grade stainless steel vessel having 1210 mm column height, 400 mm diameter, and 2 mm thickness. Stainless steel condenser is connected to the distillation still via a pipe. The distillation unit has provision to operate for “water distillation” and “water and steam distillation”. The solar distillation system is equipped with thermocouples and Pyranometer to control and optimize the distillation processes. During the first phase of the research, laboratory experiments were conducted to determine the heat energy required per unit weight of different plant materials. Scheffler fixed focus concentrator was selected for the processing of medicinal and aromatic plants. A mathematical procedure has been explained to calculate the parabola equations for an 8 m2 surface area Scheffler reflector for all the days of the year in the northern and southern hemisphere. The construction, installation and tracking details of the solar distillations system are also explained in the manuscript. Two mathematical models were developed in Matlab and Microsoft Excel. First model is used to calculate the required size of the Scheffler reflector and the second model is applied to predict the energy distribution and heat losses from the solar distillation system. Under field experiments, several experiments were carried out to evaluate the performance of the system. Within the beam radiation range of 700-800 W m-2, temperature available at focus was found between 300 and 400 °C. These results show that profiles of primary reflector, tracking system, and inclinations of the axis of rotation are precise and converging the beam radiations at the targeted focal point with the changing sun position during the test period. During trials, average power and system efficiency were found to be 1.548 kW and 33.21 % respectively at an average solar radiations of 863 W m-2. These results were found approximately the same as calculated from modeling under similar conditions. During the research, a steam receiver is also evaluated to produce steam for solar-based steam distillation system. The system efficiencies for the generation of steam by using only primary reflector and by using both primary and secondary reflectors were found to be 49.8 and 40 % respectively. It was concluded that about 9-10 % efficiency is lost by using the secondary reflector

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