Integration of a desiccant unit in crops solar drying installation: optimization by numerical simulation

An adsorption unit of silica gel is designed and integrated in a crops solar drying installation. The installation consists of a direct flat plate forced convective solar dryer connected with a similar solar collector. The daily sorption cycle of the desiccant unit is first investigated and a suitable coupling of the collector, the dryer and the adsorption unit has been selected. The coupling is numerically simulated and applied to the drying of apricots in Morocco under real climatic conditions. The mathematical model assumes non-isothermal processes and employs the basic balances of heat and mass transfer. The developed non-linear partial differential equations were solved by finite difference methods and the physical and operational parameters of the installation were numerically optimized. The integration of the adsorption unit allowed improving the quality of the dried product and permitted a cyclic operation of drying over two days by reducing the drying period from 52 to 44 h.