Double-glazed solar air heater with novel integrated phase change material composites for enhanced drying applications.

Abstract

The present invention pertains to the storage of thermal energy for the efficient drying of agricultural crops. In one embodiment, a solar drying system is proposed that utilizes phase change material (PCM) as the energy storage medium. The System is based on a conventional flat-plate solar collector, which consists of a collector frame, a collector box, insulation, an absorber plate, inlet and outlet sections, a double glass cover, and a PCM heat storage layer. The absorber plate is made of 2 mm thick galvanized steel and is painted matte black. The collector body is also constructed from galvanized steel, with 5 cm thick glass wool used for insulation. Air flows between the absorber plate and the first glazing, exiting the collector as a single-pass flow. A PCM module is incorporated into the collector, where paraffin wax RT and an expanded Perlite composite mixed with plaster serve as the phase change material. The PCM composite (RT / EP) is prepared using a vacuum adsorption method, with expanded Perlite acting as the adsorbent and paraffin as the phase change material. To enhance the heat transfer coefficient, aluminum powder (AL) is added, comprising 10% of the PCM composite's weight. The gypsum powder and water are mixed together, followed by the addition of the PCM composite (RT / EP / AL). The collector is installed at a 30° angle to the horizontal, oriented to the south for optimal sun exposure.