Design of a Multipurpose Dryer

Abstract

Drying is one of the most important processes involved in the post-harvest handling and processing of agricultural product. A multipurpose dryer is designed to handle a variety of product ranging from grains, fruits vegetable to animal products like meat, fish etc. The criteria considered in the design computation and selection of materials includes; technical simplicity and ease of operation, profitability, durability. The dryer consists of a heating chamber incorporated with a heat exchanger, suction unit and drying chamber with a rotary shaft to induce rotation of the tray. In operation, the heating chamber is filled with water and incorporated with a heater and coiled copper tubing that are directly linked with the suction unit. The suction unit draws air into the copper tubing, the air passing through this chamber gains heat through the heated water via the copper tubing as a result of conduction. The air is then conveyed directly to the drying chamber. In the drying chamber, hot air absorbs and conveys moisture from the substances needed to be dried by heat and mass transfer as well as diffusion process, while the residual air is discharged through the vent on top of the chamber. Variable parameters needed for design include; weight/mass of moisture to be removed, quality of air required to remove the moisture, amount of heat needed by drying air, maximum amount of heat that can be gained by water from the heater and, the amount of heat which air can absorb from heated water.