Performance investigation of drying Ashwagandha roots in a forced convection-evacuated tube indirect solar dryer

Abstract

In this research work, experiments are conducted on drying Ashwagandha using an evacuated tube solar collector (ETSC) in India. The drying process performance parameters are evaluated. Experiment results obtained in drying of Ashwagandha using ETSC are compared with results obtained in open sun drying (OSD). ETSC dryer consumes 16 hours to reduce initial moisture content of 61.2% (db) to final moisture content of 8% while OSD consumes 24 hours of drying time to reach the final and safe moisture content. The average drying rate in ETSC and OSD processes are 0.004 and 0.0023% d.b min−1, respectively. Average efficiencies of the air heater and drying cabinet are 52% and 35%, respectively. From thin-layer mathematical modelling, Page and Two-Term models are the best fit for ETSC and OSD, respectively. After drying, OSD samples have the highest colour change than OSD. Total phenolic contents are 32.35 ± 1.4 and 21 ± 2.1 of the solar and OSD samples, respectively.