DEVELOPMENT OF AN EFFICIENT LOW COST EMERGENCY TOBACCO CURING BARN FOR SMALL SCALE TOBACCO GROWERS IN ZIMBABWE
NGONI C. CHIRINDO *
Department of Agricultural Engineering, Chinhoyi University of Technology, P. Bag 7724, Chinhoyi, Zimbabwe.
DANIEL JAMBWA
Department of Agricultural Engineering, Chinhoyi University of Technology, P. Bag 7724, Chinhoyi, Zimbabwe.
PETER RWAKATIWANA
Department of Agricultural Engineering, Chinhoyi University of Technology, P. Bag 7724, Chinhoyi, Zimbabwe
ZVIREVO CHISADZA
Pan African University Institute of Water and Energy Sciences (Including Climate Change) [PAUWES], Cite Universitaire, Rocade 4, Tlemcen, Algeria.
COURAGE BANGIRA
Department of Irrigation Engineering, Chinhoyi University of Technology, P. Bag 7724, Chinhoyi, Zimbabwe.
*Author to whom correspondence should be addressed.
Abstract
Zimbabwe is the largest producer of flue-cured tobacco in Africa and fifth in the world. Of the 106 127 registered tobacco growers in 2014 in Zimbabwe, 84% of the farmers belonged to the smallholder category that relies heavily on inefficient and expensive wood powered curing facilities. These farmers are losing thousands of dollars as a result of decaying of over ripened tobacco leaf in the field due to barn space shortage. The cause being the high cost involved in permanent barn construction and the long turnaround time by inefficient traditional barns to complete a curing cycle. The main objectives were to develop a barn of low cost, efficient, easy to construct and that can be constructed in the shortest possible time. Material selection was done based on cost, durability and ease of installation. A 250 µm gauge black polythene plastic was chosen as a covering material due to its thermal properties and resistance to moisture and sun’s ultra violet rays. The barn was designed to use buoyancy principle of natural draft for its air circulation and natural fanning of the furnace. It was designed to trap air in between the plastic right round the barn which will be used as heat insulator. Design calculations were done and drawings were made with AUTOCAD software. The barn was fabricated at Chinhoyi University Research Section at a total cost of USD 592.70 in 5 days. With this low cost and less construction time, farmers can be able to construct the efficient emergency structure and maximize on tobacco quality. Heat transfer measurements were done after fire was set and the temperature was raised to 70°C which is the required maximum temperature for curing tobacco. From the results, it was seen that the barn is efficient as the heat transferred for curing was sufficient enough to cure tobacco with 62.6% wood fuel saving. Land degradation due to tobacco curing barn constructions is also reduced. After the estimated 3 year life span of the emergency structure, it can be developed into a permanent rocket barn.
Keywords: Efficient, low cost, emergency, barn, heat transfer, natural draft.