Experimental investigation of the performance of a novel solar dryer for drying medicinal plants in Western Himalayan region

This paper presents the experimental investigation of indirect forced convection solar dryer integrated with sensible heat storage material (SHSM) and phase change material (PCM) in meteorological environment of Himalayas (latitude 30.91 degrees N). The iron scrap mixed with gravel is placed on absorber plate and copper tubes comprising of engine oil have been used as SHSM in the solar collector. The Paraffin RT-42 as a PCM has been used in the drying chamber. Experimentations of Valeriana Jatamansi (a medicinal herb) drying have been conducted and its moisture content reduced from initial value of 89% to 9%. Using SHSM and PCM simultaneously the overall drying rate observed 0.051 kg/hr which was almost double as compared to 0.028 kg/hr and 0.018 kg/hr with no use of thermal storage medium and traditional shade drying, respectively. The drying time to reach the saturation level of 9% was recorded as 120 h in comparison to 216 and 336 h, respectively and the dried rhizomes of good quality in terms of essential oil and bio-medical compounds are obtained. From the experimental results rehydration capacity and total Valepotriates were found 7.11 and 3.47% as compared to 6.18 and 3.31%, respectively in case of traditional shade drying. The solar collector without SHSM possess an average energy and exergy efficiency 9.8% and 0.14%, respectively. The respective energy and exergy efficiency achieved with SHSM are 26.10 and 0.81%.