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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 °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%.

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.

This work presents an experimental analysis of a novel indirect solar dryer for drying chillies in the Western Himalayas. Iron scrap assorted with gravels are kept on the absorber plate and engine oil transported through the copper tube, have been applied as sensible heat storage (SHS) medium in the solar air collector (SAC). Paraffin wax has been employed as a phase change material (PCM) in the drying compartment. The performance evaluation of the drying system has been carried out on the basis of physical, thermal and quality attributes. The moisture level of chillies is reduced to 4.85% from 86.50% (wet basis) in 21 h as compared to 96 h and 150 h by using solar drying without thermal storage and in the natural sun, respectively. Outcomes of this work conclude that the dehydrating time is reduced by 78.12% and 86.00% as against drying conducted without the use of SHS and PCM, and natural sun; respectively. Using this drying system, the colour, texture, pungency (sensory parameters) and rehydration capacity of the dehydrated chillies have been found better. From the experimental results vitamin C, capsaicin, carotene and thiamin of the chillies were found 49.25 mg, 0.52%, 341.5 µg and 0.912 mg which were 32.25 mg, 0.23%, 217.8 µg and 0.534 mg, in case of natural sun drying.