Study of drying parameters of pineapple and performance of indirect solar dryer supported with thermal energy storage: Comparing passive and active modes

Abstract

In this study, passive and active indirect solar dryers (PISD and AISD) with an energy storage system (paraffin wax) and the drying kinetics of pineapple were investigated. To form AISD, the PISD was restructured by providing solar-powered central processing unit fans. The mass variation and temperature data recorded during the experiments were used to evaluate drying characteristics and parameters. As a result, AISD showed an improvement of 0.089 kW, 4.34 kJ/mol, and 3.5 kWh/kg of actual heat supply, activation energy, and specific energy consumption, respectively, compared to PISD. Similarly, the dryer and collector efficiencies of AISD improved by 25.77 % and 16.52 %, respectively, compared to PISD. For PISD and AISD, the mean specific moisture extraction rate, moisture diffusivity, heat and mass transport coefficients were 3.10 and 3.67 kg/kWh, 5.23 and 5.97 × 10−9 m2/s, 0.00489 and 0.00576 m/s, and 5.6 and 6.47 W/m2K, respectively. After 16 h in PISD and 14 h in AISD, moisture content decreased from 7.91 to 0.417 (db) with an average drying rate of 0.408 and 0.45 kg/h, respectively. Based on the evaluated parameters, AISD performed better than PISD. Uncertainty analysis was performed to check the validity of the results.