Methodology for the design of a thermal energy storage module for asolar tunnel dryer using phase change materials (PCM)

Abstract

The increasing interest in renewable energy has opened an opportunity to apply this technology in the industry anddomestic sector. However, in solar-based systems, limitations associated with the intermittent energy delivery can cause unstable performance and unreliable designs. Weather fluctuations, such as wind speed and appearance of clouds, are considered the principal factors that contribute to the instability in the amount of energy available. In the agriculture, for instance, the use of thermal solar energy applied to dryer systems is highly desirable since the processis energetically very intensive. Therefore, it is feasible to design dryer devices for agricultural products, with important economic returns due to energy savings and the value added to the materials processed. Thus, the energy performance of systems that operate with solar thermal energy can be improved by introducing an energy accumulation system based on the use of phase change materials (PCM). The detailed methodology forthe design of a thermal energy accumulation system for a tunnel dryer type Hohenheim for agricultural products is presented. As PCM, paraffin is chosen because its melting temperature is near 60 °C, which is an appropriate value forthe drying temperature of this kind of products. The theoretical calculations show that the value of the surface temperature has an important influence on phase change calculations and the total mass of PCM required in the system. On the other hand, the heat transfer is dominated by the external heat transfer in the air. Additionally,the tube diameter significantly affects the phase change time. The results obtained are important and make a significant contribution to the knowledge required for implementations of similar systems, since little has been explored in this field in regionswhere the weather conditions are suitable to unexpected changes. The design should be implemented in an experimental prototype of Hohenheim dryer and its performance is to be determined based on measurement of the energy change of the drying air.