Performance analysis and drying kinetics of beetroot slices dried in an innovative solar dryer without and with thermal storage unit

Abstract

ABSTRACT An active indirect solar dryer (AISD) has been used to conduct drying experiments of beetroot slices without a thermal storage unit (TSU) (mode-I) and with TSU (mode-II) using paraffin wax as a phase change material. The performance analysis and drying curves of beetroot slices were assessed in both modes and compared. The average drying efficiency and drying rate were enhanced by 48.63% and 41.72% in mode-II compared to mode-I. Two-term exponential and modified Page models were the best models for beetroot slices in mode-I and mode-II, respectively. The specific energy consumption was estimated to be 1.706 and 0.96 kWh/kg, the average moisture diffusivity was 7.11 × 10−9 and 7.22 × 10−9 m2/s, and the mean mass transfer coefficients were 3.56 × 10−3 and 3.64 × 10−3 m/s, respectively. The specific moisture extraction rate was 0.586 and 1.041 kg/kWh and the mean heat transfer coefficient was 4.103 and 4.2 W/m2K, in mode-I and mode-II, respectively. The collector outlet temperature is increased by 2.5 to 10.7°C when the heat is discharged from TSU. In comparison to mode-I, the performance of AISD is superior in mode-II, exhibiting better drying performance due to TSU in the drying section in mode-II.