Investigations on desiccant assisted packed bed solar dryers

Abstract

The fast depletion of conventional energy resources and its negative impacts on environment have accelerated the research and developments on making use of renewable energy sources in post harvesting applications. The thermal drying of agricultural products is an energy intensive post harvesting technology. The solar energy is identified as an energy efficient and environment-friendly option for the processing of agricultural materials when compared to other renewable energy options. Hence, an attempt has been made in this research work to explore the newlinepossibili ty of using desiccant assisted packed bed solar air collectors for drying of agricultural materials. An experimental test facility of desiccant assisted packed bed (packed with paraffin wax) solar dryer with necessary instrumentation has been developed to investigate its feasibility for drying of agricultural materials. The technical feasibility was evaluated in terms of energy analysis. The performance was evaluated under the meteorological conditions of Coimbatore in India (latitude and longitude) during the year 2015. The economical feasibility was evaluated in terms of payback period. The dryer unit consists of a packed bed solar air collector of 2 m2 collecting area with a provision of holding latent heat storage materials (paraffin wax) and desiccant bed made up of perforated mild steel sheet for holding the desiccant materials at the collector entry (to control the moisture in drying chamber), drying chamber made up of mild steel of 1.2 mm thick with dimensions 1 m × 1 m × 1 m. A turbo ventilator has been provided at the top of the drying chamber to venting the humid air. newline newline