Thermal Performance Evaluation of Indirect Domestic and Portable Hybrid Solar Dryers Under No Load Conditions

Abstract

A compact, novel, indirect-type domestic hybrid and portable solar dryer (ITDHPSD) was developed and tested at Delhi Technological University. Dryer was tested in November under stagnant conditions, with the inlet and outlet ports closed. Temperature variations and heat losses at the solar collector were evaluated to assess the feasibility of the dryer. Maximum absorber temperature reached 98°C at 13:00 h, and the average overall heat loss coefficient was 10.25 W/m²K. Heat losses from the side panels, bottom, and top glazing have also been assessed. Maximum heat loss was from the top glazing, and the minimum was from the side panels. Furthermore, a thermal performance investigation was carried out in active mode under no-load conditions. Experiments were performed on the dryer from 09:00 to 16:00 h during November (winter season). Thermal performance of the indirect-type domestic hybrid and portable solar dryer was evaluated in terms of heat utilization factor (HUF), coefficient of performance (COP), and thermal efficiency. Mean ambient temperature and mean solar insolation during experimentation were in the range of 21.1°C–30°C and 424–660 W/m², respectively. Maximum thermal efficiency, HUF, and COP of the solar collector in the ITDHPSD were calculated as 59%, 0.68, and 0.32, respectively, at 13:00 h. ITDHPSD has been found feasible for drying crops and can be used in both domestic and small-scale industries to generate livelihoods. Its superior thermal efficiency and compact size make it a practical, cost-effective solution for drying crops with solar energy.