ABSTRACT

Drying is one of the most important processes involved in the post-harvest handling and processing of agricultural and food products. In this study, a charcoal-fired three-shelf dryer was designed, fabricated and tested for cart fish drying in order to make these commodity available all the year round in reasonable quantity, good quality and afftrchtble costs. The criteria considered in the design computation and selection of construction materials included: technical simplicity, ease of operation, maintainability, and storahihity of the product after drying. Other considerations focused on portability, durability, ease of operation and utilization, and techno-economic status of the small scale farmers and food processors who are the intended users of the dryer. The dryer consists of combustion chamber, heat exchanger, suction unit, and drying chamber. In operation, charcoal is fired in the combusdon chamber, the heated air then passes through the heat exci'inger/conserver which filterS the hot air with the aid of the suction unit before being conveyed to the drying chamber. In the drying chamber, hot air absorbs and conveys moisture from the product by heat and mass transfer and diffusion process while the residual air is disoharged through the ch'nne' on top of the chamber. Design calculation parameters included: weight of moisture to ha rerooved from the product, quantity of air required to remove the moisture, amount of heat eneFey required by drying air, and quantity of charcoal required to produce the heat energ for drying. A preliminary test carried out on the dryer showed that it was ah to reduce the moisture content ofcomniodities to a safe level for storage, with a moisture removal rate of6%. mdicating that the dryer performed satisfactorily when compared with the old kiln with 1.7% moisture removal rate. The dryer has a production cost of(N) 2O,OCO including labour.