Design, Development and Evaluation of Folding Type Pyramid Shape Solar Dryer for Bitter Guard Drying

Abstract

Bitter gourd (Momordica charantia L.) is a perishable cucurbit crop used for culinary and medicinal purposes, but surplus production can contribute to post-harvest losses when preservation options are limited. This study focused on the design, development and evaluation of a folding-type, pyramid-shaped solar dryer for drying bitter gourd slices under natural convection. The dryer was designed with a 5 kg loading capacity, four drying trays and a total tray area of 2.4 m². Its dimensions were 1.50 × 1.50 × 1.40 m, and the main components included a drying chamber, drying trays, a loading door and an exhaust chimney. The foldable arrangement enabled assembly and disassembly by bolting and unbolting the main frame and removing the side frames. Performance was assessed under no-load and full-load conditions and compared with traditional open sun drying. The dryer achieved a maximum drying temperature of 65 °C. During winter testing, bitter gourd slices were dried to a final moisture content of approximately 5% on a wet basis in 13 hours, compared with 16 hours under open sun drying. The average drying rate in the solar dryer was 0.40 g/100 g bdm min. The overall drying efficiency was 28.48% during winter laboratory testing. Economic analysis indicated a benefit-cost ratio of 1.04, net present worth of Rs. 9080.85 and a payback period of 2 months and 8 days.