Mathematical modeling of an integrated system for regeneration of solid desiccants using a solar parabolic dish concentrator Vahid Madadi Avargani a,⇑ , Reza Karimi b , Touraj Tavakoli Gheinani c a Department of Chemical Engineering, Faculty of Engineering, Yasouj University, Yasouj, Zip Code: 75918-74831, P.O. Box 353, Iran b Department of Chemical Engineering, Faculty of Engineering, University of Isfahan, Isfahan, Iran c Department of Chemical Engineering, Faculty of Engineering, University of Isfahan, P.O. Box 81746-73441, Isfahan, Iran article info Article history: Received 22 April 2019 Received in revised form 23 July 2019 Accepted 24 July 2019 Keywords: Solar parabolic dish collector Cylindrical cavity receiver Indirect air heating system Silica gel Regeneration rate abstract In this work, an integrated system is introduced to regenerate the desiccant materials in solar air condi- tioning systems. A solar parabolic dish collector and a helically baffled cylindrical cavity receiver were coupled to two series finned-tube heat exchangers, and a fixed bed filled with silica gel. A silicone oil as heat transfer fluid absorbs the solar energy and heats the air to regenerate the silica gels in the bed. The system was studied both experimentally and theoretically. A comprehensive mathematical model was developed for the entire system, and the proposed model was validated with experimental data. The regeneration rate of the desiccant materials and the average daily thermal regeneration efficiency of the system were obtained up to 0.4 kg water/h m 2 and 30% respectively, which compared to the other solar systems, the present system has a good performance and is more efficient. Based on the weather conditions of the installed location of the system, the operational or even geometrical parameters of the system can be designed in such a way that for specified required cooling capacity, the system can pro- vide the required energy for regeneration of desiccant materials. The system performance was studied during a sample day based on real solar irradiation intensity and ambient conditions, and the influence of the effective parameters was investigated on the regeneration rate of the silica gels. Ó 2019 Elsevier Ltd. All rights reserved. 1. Introduction The air condition system controlled by temperature and humid- ity has an extensive application in building air conditioning. The whole cycle of air condition system is consisting of the adsorption process, regenerating process and cooling process whereas the regenerating process is the core of the whole cycle. That is because the regenerating process not only affects the humidity operation during the adsorption process but also influences the efficiency of the whole energy of the system [1,2]. Air humidification and dehumidification processes are important operations in different industrial projects. Also, the desiccant cooling system is the proper alternative choice for the common system in humid weather con- dition for heat convenience. The adsorbents in these systems are generally divided into two groups of solid and liquid. The solid adsorbents have some advantages such as lower regeneration tem- perature and higher operational flexibility, easier transfer, a lower rate of corrosion and higher resistance to corrosion up to elevated temperatures in comparison to the liquid adsorbents. In these sys- tems, solid adsorbents like silica gel, alumina, activated carbon, and zeolite are used. Adsorbents are applied as a rotary desiccant or fixed beds in refrigerating systems. Silica gel adsorbent is more applicable due to characteristics like high capacity in humidity adsorption, low regeneration temperature, cheaper cost and more available in comparison to other adsorbents [3,4]. These adsor- bents eliminate the humidity of the air and then after water adsorption, were released by using heat energies like electrical heat, solar heat, and waste heat. Silica gel is proper for water sep- aration in plastic and pharmaceutical industries. Pressure swing adsorption (PSA) and temperature swing adsorption (TSA) are two common adsorption cyclic processes. Pressure swing adsorp- tion (PSA) is a technology that used to separate water vapor from an adsorbent under pressure changes based on the molecular char- acteristics of species and affinity for an adsorbent material. It oper- ates at near-ambient temperatures. In TSA method, the pressure in the adsorption and desorption operation remains constant while the temperature is variable as it must be kept low in adsorption process or high in desorption process to achieve the high efficiency [5]. https://doi.org/10.1016/j.ijheatmasstransfer.2019.118479 0017-9310/Ó 2019 Elsevier Ltd. All rights reserved. ⇑ Corresponding authors. E-mail addresses: v.madadi@yu.ac.ir (V. Madadi Avargani), re.karimi@eng.ui.ac.ir (R. Karimi), ttavakoli@eng.ui.ac.ir (T. Tavakoli Gheinani). International Journal of Heat and Mass Transfer 142 (2019) 118479 Contents lists available at ScienceDirect International Journal of Heat and Mass Transfer journal homepage: www.elsevier.com/locate/ijhmt