Energy and exergy analyses of drying medicinal herb in a novel forced convection solar dryer integrated with SHSM and PCM

Abstract This article examined the performance of a low cost, economically viable and a novel forced convection solar drying system. To control the thermal fluctuations during the day-night drying process, solar air collector (SAC) was equipped with sensible heat storage medium (SHSM) while, drying unit contained paraffin RT-42 as a thermal energy storage (TES) medium. The experiment was conducted considering a sample size of 9.0 kg of Valerian rhizomes. The rhizomes were dehydrated to saturation value of 9% from preliminary moisture content of 89% on wet basis and took 120 (216) hours with (without) use of TES. The performance evaluation of each element of the dehydrating system was carried out on the basis of energy and exergy analyses. The mean values of energy and exergy efficiencies of SAC without (with) TES were computed to be 9.8(26.10) % and 0.14(0.81) % respectively. The overall drying rate without (with) applying TES was 0.028(0.051) kg/hour. The exergy efficiency of the drying unit was assessed to vary from 3.7% to 75.15% with a mean value of 30.28%. The specific energy consumption (SEC) of the rhizomes and the overall efficiency of the drying system were 11.33 kWh/ kg of moisture and 10.53%, respectively.