Enhancing Efficiency of Small-Scale Solar Food Dryers under Omani Climatic Conditions: A Study on Natural Convection and Thermal Collector Performance

Abstract

This study evaluates the performance of five small-scale solar food dryers operated under natural convection to dry potato slices, focusing on the influence of different thermal collector materials on drying efficiency under Omani climatic conditions. The dryers, identical in size and design, differed only in the collector materials used: white marble (WM), black-painted marble (BM), gray rock (GR), granular carbon (GC), and a control black absorber floor (BAF). Results showed that darker collectors (BM and GC) achieved higher surface temperatures (50–52 °C) compared to lighter collectors (≈45 °C for WM), due to improved solar absorption and reduced reflectivity. Consequently, the highest initial drying rates were obtained using GC and BM (0.12 g/min and 0.11 g/min, respectively), while WM exhibited the slowest rate (0.035 g/min). The moisture content of the potato slices was reduced by approximately 90–93% within 4–5 hours for GC and BM, while WM required more than 7 h to achieve similar results. The findings demonstrate that both collector color and material significantly affect thermal performance and drying kinetics. However, during the later drying stage, internal moisture diffusion limited the drying rate, indicating that forced air convection could further enhance performance. This study provides a foundation for developing cost-effective, small-scale solar dryers suitable for rural food processing applications in arid regions like Oman.