experimental analysis of drying performance in etc-assisted solar dryers: influence of collector count and soil particle size

Solar drying provides a sustainable substitute for traditional fuel-based preservation techniques by harnessing renewable thermal energy. this study investigates the impact of the number of evacuated tube collectors (etc), ranging from 1 to 3, and the size of sand particles—fine-grained (fgs), medium-grained (mgs), and coarse-grained (cgs)—on the efficacy of a solar dryer that incorporates sand-based thermal storage. experiments were performed under three etc configurations utilizing grated carrot samples, with drying performance assessed based on drying rate (0.57–0.93 g/min) and drying efficiency (up to 70.7%). the findings indicated that augmenting the quantity of etcs improved the drying rate, achieving a peak of 0.93 g/min with fgs in the three-etc configuration, succeeded by mgs and cgs. fine sand exhibited enhanced heat conductivity, facilitating expedited moisture removal, whereas medium and coarse grains provided more consistent drying in subsequent phases. nonetheless, drying efficiency diminished with increased etc counts, declining from 70.7% (fgs–1 etc) to approximately 20.7% (fgs–3 etc). the results highlight the compromise between attaining increased drying rates and preserving thermal efficiency, offering guidance for the optimization of solar dryer designs that integrate thermal energy storage materials.