Numerical model of an inflatable solar collector

The main objective of this paper is to present a mathematical model to simulate the operation of an inflatable solar air heat collector for grain dryers. The solar collector exhibits a semicylindrical shape when air is injected into the confined space between the walls of the two covers. The mathematical model of the collector is obtained by applying the law of conservation of energy on the four main parts of the collector, absorber plate, two covers, and air that flows inside the equipment. To improve the accuracy of the model, the solar collector was divided into N control volumes, with each one containing the four parts, in such a way that one system with 4N differential equations is obtained. The unknown quantities of this system are the temperatures of the absorber plate, air, and walls of both covers in each control volume. The results allow us to conclude that the collector performance strongly depends on several entrance variables of the model (the air flow and air temperature at the collector entrance) and geometric equipment parameters (the collector length, internal radiation at the inner surface of the cover, and space between both covers). Therefore, the model can be used for optimizing the solar collector.