Heterogeneous drying performance of a multi‐tier natural convection solar dryer

Abstract An innovative and cost‐effective multi‐tier cabinet solar dryer (MCSD) with an integrated stirring mechanism is presented to enhance drying efficiency under heterogeneous thermal conditions. Each cabinet functions as a flat plate solar collector, leveraging the greenhouse effect to minimize radiation and convection losses. The incorporation of an orientation mechanism optimizes solar energy intake, ensuring improved heat distribution. Developed in‐house at PDPM IIITDM Jabalpur, the MCSD is durable, space‐efficient, and portable, catering to marginal farmers and domestic users. The multi‐tier design introduces heterogeneous drying conditions across different cabinets, leading to variable temperature and airflow patterns that facilitate diverse drying kinetics. The dryer showed a maximum thermal efficiency of 15.66% (batch) and 11.53% (continuous), with effective moisture diffusivity ranging from 2.204 × 10 −10 (MCSD), 7.6549 × 10 −10 (Single cabinet dryer) and 5.4636 × 10 −10 (open sun drying) m 2 /s, a payback period of 0.68 years, and heat transfer coefficients of 15.07–17.84 W/m 2 ·K across the cabinets. The designed configuration not only increases the overall drying capacity per unit space requirement, by approximately three times compared to a single‐cabinet dryer (SCD) but also enables batch‐mode drying to accommodate varying moisture removal rates. The study revealed that despite the heterogeneity in thermal profiles, a relatively uniform drying rate was achieved across all cabinets over three drying days, ensuring effective and consistent moisture reduction in vegetables, fruits, spices, and herbs under natural convection.