Experimental investigation on the thermal appraisal and sustainability indicator of heat pipe-based indirect solar dryer during Giloy (Tinospora cardifolia) drying

Tinospora cordifolia (Giloy) is an anti-periodic, anti-inflammatory, anti-arthritic and anti-diabetic agent in folk medicine. As per ayurveda giloy boosts the immune system. Current work investigates an evacuated tubes solar dryer with heat pipes (ETSD_HP) to develop a sustainable drying method for medicinal plants, i.e., Giloy stem. Experiments are conducted at different air mass flow rates viz. 0.010 kg/s (Ṁ1), 0.0125 kg/s (Ṁ2), and 0.015 kg/s (Ṁ3). Thermal profiling, drying characteristics, mass transfer parameter, energy and exergy analysis were conducted. The initial moisture content of stem was 81.68±0.37 % (wb) and reduced to 8.75 % in the minimum time of 12 h at 0.0125 kg/s. Existing models for drying kinetics are evaluated, and a new model was developed for predicting the moisture ratio. The highest energy efficiency was 42 % for drying under Ṁ3. The exergy efficiency of the drying process increases as the hot air flow rate increases from Ṁ1 to Ṁ3. The improvement potential (IP), as a sustainability indicator, was in the range of 10.76 to 43.75 W, 17.09 to 59.44 W, and 16.79 to 77.15 W for Ṁ1, Ṁ2, and Ṁ3, respectively. The highest moisture diffusivity was found for Ṁ2, around 1.17 times more than Ṁ1.