Design and development of solar assisted fluidized bed dryer integrated with liquid desiccant dehumidifier: Theoretical analysis and experimental investigation

Abstract

Higher energy demand for ventilating higher mass flux of hot air in fluidized bed drying (FBD) and SDG-7 of the UN has been actuated the researchers towards solar energy intervention in FBD. However, the thumb rules and systematic design calculation of the solar system for FBD have not been reported in the literature. In view of that, a novel solar thermal system was designed and developed by thermo-hydrodynamic analysis, considering the variable physical properties of bioproducts and fluctuating weather. The key design parameters were fresh and desired dried product's moisture content, physical properties of products, dryer capacity, desired drying temperature, ambient conditions, etc. In order to enhance the drying effectiveness, state-of-the-art technology for air dehumidification was integrated by using an aqueous blend of LiCl (35 %) + CaCl (5 %) desiccant. A solar photovoltaic system was also estimated for recirculating the moisture-saturated desiccant over an unglazed solar absorber to regenerate it. From the experiment of ginger drying, it was explicitly found that the developed solar FBD could supply sufficient heat energy (173.06–604.12 W/hr.) compared to the required heat load (124.65 W/hr.), which justifies the operational flexibility. The obtained solar heat fraction (∼1) and solar fraction (0.52–0.64) imply that the solar energy could fulfill the heat energy demand by 100 % and total energy demand (heat + electrical) up to 64 %. The energy efficiency, exergy efficiency, and sustainability index of the solar thermal system were obtained up to 48 %, 2.96 %, and 1.03, respectively. Aiming for effective energy utilization, an intermittent heat supply strategy was associated. Compared to continuous drying, intermittent drying reduced the active drying time (2–2.5 hrs.) and specific energy consumption (33.47–43.83 %) and fortified the dried ginger by reducing shrinkage (11–12 %) and increasing the rehydratability (up to 22.15 %).