Mathematical modelling and numerical simulation of the drying chamber of an indirect solar dryer

Drying is one of the oldest methods employed by farmers to avoid spoiling agricultural products and allowing for longer storage times. Farmers at ASPROBO (Organic Banana Producers Association), an association in the district of Buenos Aires in the province of Morropon, Piura, Peru, use the traditional open sun drying of cocoa beans. Open sun drying has several drawbacks (slowness, uneven drying, inability to control the temperature, unprotected from bad weather on rainy days). In order to overcome these disadvantages, a change from traditional sun drying to indirect, direct, or mixed solar drying is proposed. As an initial stage of the study, a review of the literature was carried out on the theory of drying food and on different types of solar dryers for cocoa beans built around the world. The advantages and disadvantages of the different types of solar dryers for cocoa beans were studied and it was concluded that indirect solar dryers are a viable solution to overcome the disadvantages of traditional drying. The mathematical model of the indirect solar dryer consists of a system of partial differential equations obtained as a result of energy and mass balances. The software, MATLAB, was used for the numerical simulation. The temperature and humidity of the air, as well as the temperature and moisture content, on a dry base of cocoa beans, were obtained as a result of the numerical simulation, which are the critical variables in the study of an indirect solar dryer.