Performance Characteristics of a Cooking Stove Improved with Sawdust as an Insulation Material

Abstract

In developing countries, energy demand from biomass has increased due to exponential population growth. This has translated into voluminous quantities of wood being used. The situation is exacerbated by the popular use of inefficient stoves with low thermal insulation, hence contributing to deforestation. In this study, the performance of a cooking stove improved with sawdust as an insulation material was assessed. An insulated fire stove prototype of 26 cm saucepan diameter was designed, constructed, and cast with sawdust and clay in a ratio of 1 : 1 (as the first layer) and sawdust alone as the second layer. The developed stove was tested using a water boiling test to establish its operating performance. The thermal efficiency of the stove was assessed using indigenous wood fuels used in rural Uganda (Senna spectabilis, Pinus caribaea, and Eucalyptus grandis). Computational fluid dynamics was used to simulate the temperature and velocity fields within the combustion chamber and for generating temperature contours of the stove. Obtained results indicated that S. spectabilis had the highest thermal efficiency of 35.5 ± 2.5%, followed by E. grandis (25.7 ± 1.7%) and lastly P. caribaea (19.0 ± 1.2%) in the cold start phase when compared with traditional stoves. The stove remained cold as hot air was restricted to the combustion chamber with decreasing temperature contours toward the outer wall up to the ambient temperature. The velocity flow remained constant as the chamber was colored green throughout due to the shielding of the stove with sawdust as insulation. The heat flux generated indicated that a thick layer of 6 cm or more could ensure good insulation, and this could be further reduced by introducing more sawdust. The designed stove has the potential to reduce biomass consumption and emissions when compared to traditional cookstoves. The inclusion of a chimney draught in the fire stove prototype could reduce smoke and increase thermal efficiency. Further studies should focus on minimizing the thickness of the clay-sawdust (first) layer and increasing the thickness of the sawdust layer to reduce the weight of the fire stove.