Analysis and comparison of the performance parameters of passive and active indirect solar dryers with heat storage...

The performance of passive and active convection indirect solar drying systems provisioned with paraffin wax as heat storage was examined while drying carrot slices. The passive indirect solar dryer (type-I) was made initially, and it was upgraded with solar-powered fans to promote mass flow rate. The new assembly was considered an active setup (type-II). Data collected during experiments were analyzed to determine performance parameters and drying kinetics. There were average improvements of 11.8%, 12.2%, and 20.7% in actual heat supply, activation energy, and specific energy consumption in type-II compared to type-I. The averaged values of collector efficiency of type-I and type-II were 59.7 and 67.8%, and the drying efficiency was 11.1 and 14.2%, respectively, while their respective improvements were 13.6 and 27.93%. It was found that the coefficients of moisture diffusion (D_e), heat transfer (h), mass transfer (h_m), and the rate of specific moisture extraction were increased by 20.83%, 16.9%, 14.52%, and 27.8%, respectively in type-II compared to type-I. A logarithmic correlation was observed for D_e, h, and h_m demonstrating a decrease in moisture content (MC) increased the variables. The MC was diminished from 9.13 to 0.478 kg/kg of db in 15 h in type-I and 12 h in type-II with a 3 h saving in drying time with a better drying rate in type-II. The reliability of the results was assessed with uncertainty analysis.