Solar Energy Assisted Fluidized-Bed Dryer

Abstract

Natural sun drying is a wide-spread technology practised since the early times of mankind. However this process presents several problems such as infestation by insects and long periods of drying. To avoid such problems, different artificial drying methods have been developed. These methods generally still use solar energy directly or indirectly and rely upon packed bed principles. Although fluidized-beds offer a much more improved media for heat and mass exchanging processes when compared with packed beds, the apparent complexity and the need for external energy have hindered them to find a broad application in drying. This paper shows the possibility of using fluidized bed principle simply and economically when a proper design is made. With the aid of computer aided design methods, and using phenomena of local fluidization, an optimum packed bed and a fluidized-bed combination was achieved in a single bed. This bed itself also works as a solar air heater. The paper describes a novel design for drying locally grown Sultana grapes. It also compares the design with other competitive and comparable systems.