ABSTRACT
Uneven drying is the key drawback of a conventional multi-tray dryer. Therefore, an improved active solar dryer with and without integrated sensible heat storage (SHS) was proposed. A unique feature of this dryer is its movable walls from the sides of the dryer to transform it to an indirect or mixed-mode as and when necessary. Garcinia Pedunculata (GP) is a local seasonal medicinal fruit in Northeast India. Drying kinetics of GP, the dryer performance and economic analysis of dryer were evaluated in the indirect solar dryer without SHS (Exp. I), mixed-mode solar dryer without SHS (Exp. II), indirect solar dryer with SHS (Exp. III), mixed-mode solar dryer with SHS (Exp. IV), and open sun drying (OSD). The dryer's average efficiencies were 18.12%, 22.37%, 21.74%, and 24.46% for Exp. I, Exp. II, Exp. III, and Exp. IV, respectively. The moisture content of GP was reduced to 12.09% in wet basis (w.b.) from 87.99% (w.b.). The overall drying time for Exp. I, Exp. II, OSD, Exp. III and Exp. IV were 31, 26, 53, 28, and 10 h, respectively. From the eleven drying models, the Two-Term model was the best-fitted model for Exp. I, Exp. II, OSD and Exp. III, and Midilli and Kucuk model was for Exp. IV. The final product's fragrance and colour are better for Exp. IV. Developing this dryer for Exp. I, Exp. II, Exp. III and Exp. IV, the price required was around 25,000, 27,000, 26,000, and 28,000 INR (1 US$ = 74.57 INR), respectively, while the economic payback periods are 1.6 years, 0.9 year, 1.4 years, and 0.59 year, respectively.
Subject(s)
Garcinia , Thoracica , Animals , Hot Temperature , Desiccation , SunlightABSTRACT
An indirect-type forced convection solar dryer implementing a phase-changing material (PCM) as the energy-storing medium was designed, fabricated, and investigated in this study. The effects of changing the mass flow rate on the valuable energy and thermal efficiencies were studied. The experimental results showed that the instantaneous and daily efficiencies of the indirect solar dryer (ISD) increased with the initial increase in mass flow rate, beyond which the change is not prominent both with and without using the PCM. The system consisted of a solar energy accumulator (solar air collector with a PCM cavity), a drying compartment, and a blower. The charging and discharging characteristics of the thermal energy storage unit were evaluated experimentally. It was found that after using PCM, drying air temperature was higher than ambient air temperature by 9-12 â after sunset for 4 h. Using PCM accelerated the process by which Cymbopogon citratus was effectively dried between 42 and 59 °C of drying air. Energy and exergy analysis of the drying process was performed. The daily energy efficiency of the solar energy accumulator reached 35.8%, while the daily exergy efficiency reached 13.84%. The exergy efficiency of the drying chamber was in the range of 47-97%. A free energy source, a large reduction in drying time, a higher drying capacity, a decrease in mass losses, and improved product quality all contributed to the proposed solar dryer's high potential.
