International Journal of Advanced Engineering Research and Science (IJAERS) [Vol-4, Issue-5, May- 2017] https://dx.doi.org/10.22161/ijaers.4.5.18 ISSN: 2349-6495(P) | 2456-1908(O) www.ijaers.com Page | 111 Numerical and Experimental Study of Natural Convection Air Flow in a Solar Tower Dryer Germain W. P. Ouedraogo 1 , Sié Kam 1 , Moussa Sougoti 1 , Ousmane Moctar 1,2 , Dieudonné Joseph Bathiebo 1 1 Physic Department, Ouaga 1 University Professor Joseph Ki-Zerbo, Ouagadougou, Burkina Faso 2 University of Agadez PO BOX 199 Niger Abstract— This work focuses on the study of the flow of air in natural convection in a solar tower of small size. The behavior of air in the tower, considered as a solar dryer, provides information on the amount of heat absorbed by the air upon entry into the collector. A theoretical approach allows us to theoretically simulate the flow by using a mathematical model characterizing the physical parameters of the system during a daily sunshine. An analysis of this phenomenon is made and results are obtained. Keywords— Flow of air, natural convection, solar tower, dryer. I. INTRODUCTION The concept of solar tower or solar power chimney was proposed first by Cabanyes [1]. Solar towers consist of a collector, a chimney and a turbine. They allow the production of electricity. A Solar tower without its turbine can have a use other than that of power generation: the drying of food products, thanks to the drying air coming out of its collector; hence its name of solar tower dryer. The drying of food products is an appropriate means to curb losses of food after harvest and expand the consumption of these products during periods of non- production. This is an operation which is much practiced in West Africa by farmers. Several studies have shown the difficulty of getting indisputable elements of validation and comparison between different solar dryer models due to its technological diversity. In our work, we study the operation of a solar tower dryer, running empty. The objective is the use of the energy gain received by the air through the collector for the drying of food products. To do so, it is essential to carry out a study of fluid flow in the system in order to know the amount of energy that the air must absorb with an average humidity of 40% in the cases of BURKINA FASO. II. DESCRIPTION OF THE SOLAR TOWER DRYER The solar tower dryer is a natural thermal power generator, which uses solar radiation to increase the internal energy of the air flowing in its collector. The useful gain of the solar collector is converted into kinetic energy flow circulating in the chimney where trays or racks are arranged. 2.1. Description of the solar tower As part of our work, the solar tower has a function other than to produce electricity. Used as solar dryer, it is small compared to that producing electricity and consists mainly of a collector and a chimney.  The collector has a radius of 1.2 meters. This is the part where the air circulates. It is heated by absorption of solar flux and subjected to phenomena of convection. The collector consists of a cover of four square shaped glass windows of a square meter and an absorber in alu-zinc painted matte black, between which the air flows.  The chimney has a diameter of 0.4 meters and a height of 3 meters; it is the drying chamber and has racks for display of products to dry. The chimney has two roles: that of drying-chamber and that of drawing of drying air. The greater its height, the more important its pull effect and it promotes the renewal of air in the [2-3] system. 2.2. Functioning of the solar dryer The products to be dried are not directly exposed to solar radiation and that makes of the tower an indirect solar dryer. The air entering the collector is heated by natural convection from the sensor and moves through the chimney effect towards the drying chamber where the drying air takes away the water molecules from the products to be dried ( Fig.1).