Modeling of a solar dryer for fruit preservation in developing countries

About 25,3 % of the Mozambican population is suffering from undernourishment even though a sufficient amount of food and specifically fruits are produced. Post-harvest losses are estimated to 25 % to 40 % and part of the production is not even harvested due to a short season. A solution has to be found to improve fruit preservation and allow the population to consume what is harvested later. Drying fruits is a solution to preserve them. However, juicy fruits are harder to dry than other fruits since they contain more water. One small-scale solution is drying juicy fruits in a specific membrane which allows water vapor to escape from the fruit and the fruit juice to dry. It is possible to couple these membranes with solar dryer technology to control parameters such as temperature, relative humidityand air velocit) in order to improve the drying process
Two types of solar dryers are tested and preseted in this paper: an indirect and a direct dryer. Both solar dryers are modeled using a CFD tool (COMSOL Multiphysics) and the modeling work is based on former research to elaborate a mathematical model of the dryers physics. The simulations results produced by COMSOL allow to study the influence of several parameters such as geometry of the solar dryers, ambient conditions and solar dryers materials in order to improve the design of the dryers. The results from the modeling are compared to on-site measurements, in Mozambique, in order to calibrate and validate the models. The models estimated temperatures and relative humidity with an average relative error inferior to 20 %.