Development and performance evaluation of a hybrid solar dryer usingpumpkin fruit. Part 2. Analysis of the drying process and the operation of the equipment used

Abstract

This second part of our work presents the results of analyses of the process of drying pumpkin fruit slices at 50, 55, and 60 °C and slice thicknesses of 3, 5, and 7 mm. The dryer exhibited distinct heating phases under no-load and loaded conditions, with product load slowing the temperature rise. Drying temperature and slice thickness significantly affected drying rate and drying efficiency (p<0.05). The highest drying rate (12–14 kg/h) occurred within the first 2 hours, especially for 3 mm slices at 60 °C. The rate then declined to 2–3 kg/h between 2 and 5 hours and fell below 1 kg/h after 5 hours. Drying efficiency ranged from 42–58% at 50 °C, 47–72% at 55 °C, and increased markedly to 43–94% at 60 °C, with the 3 mm slices at 60 °C achieving the highest efficiency. Energy analysis showed a chamber efficiency of 32.2%. Product quality parameters, including shrinkage, rehydration ratio, proximate composition, microbial load, and colour, varied significantly with drying conditions. Economic analysis indicated a positive net benefit and a payback period of 1 year and 5 months. Overall, the hybrid dryer demonstrated high drying performance, improved energy use, acceptable product quality, and strong economic viability.