Development and Performance Evaluation of Thermostat Controlled Rotary Dryer for Agricultural Produce

Drying is ubiquitously used operation that improves on storage life of agricultural produce, either solid, liquid or slurry. Most dryers with relatively advanced technologies are expensive while the cheaper ones are manually regulated. This paper aimed at development of a direct and con-current rotary dryer that uses rolling action with hot air to effectively remove moisture from materials. The machine consists of a hopper as passage into dryer, dryer shell, heater housing, product discharge unit, shell flight, air blower for hot air distribution, thermostat for temperature regulation, temperature probe to sense the temperature from the heater as well as variable speed electric motor for power transmission. The novelty of the design is the integration of temperature regulator to the heating unit to make it thermostat-controlled. The materials for the design were selected based on strength, availability and economic value. The design calculations were done using existing machine design theories to obtain relevant design parameters. The performance evaluation showed that the machine is capable of drying various agricultural produce, say rice and yam from their initial moisture content levels of 85 and 75 % to 10 and 7 % final moisture content level respectively, at the rate of 1.2 kg/hr with the inlet air temperatures of 120° C for yam and 135 ° C for rice with humidity of 0.015. The use of machine would help to regulate drying temperature and reduce the need to manually monitor the drying process thus relieving mostly rural uses some effort in labour.