Abstract:
Biomass cookstove is a device used to convert the energy contained in the fuel into heat through
the combustion process. Cookstove smoke outlet cover is necessary to control over flow of air up
the chimney and forces the air to be retained in the combustion chamber in order to improve the
efficiency of the stove. This study was performed to determine the influence of cookstove smoke
outlet cover closing times on the cooking process. For the study, five identical cookstoves and
pots were prepared and four smoke outlet closing times (15, 20, 25, and 30 minutes) were used
as treatments, and for the control, the smoke outlet was left open throughout the cooking process
in one of the stoves. The study was done in five replications. Comparisons were made
(graphically and using one–way ANOVA) in terms of times of onset of cooking and effective
cooking time. In addition, stove body and smoke outlet temperature, and ash fuel wood ratios
were also determined. As far as statistical comparisons were concerned, there were no
significant differences among the treatments and the control in terms of onset of cooking time
and effective cooking times. However, graphical analysis showed the benefit of smoke outlet
closing over the control. For the effective cooking time, the graphical method revealed better
result than the statistical method since it showed the smoke outlet closing time of 15 minutes S1
showed faster onset of cooking time of 10 minutes and to be superior since it gave effective
cooking time(80 min) that exceeded ,that of Birhanu’s by 22 minutes. In fact, the results obtained
from S2 –S4 in this study exceeded the maximum result of air inlet closing times in Birhanu’s
work Besides, smoke outlet covering has not adversely affected the combustion process as
determined from the ash wood ratios. In general, early smoke outlet closing time showed
superior impact in retaining heat for extended time compared to late closing times. As seen in
the result the percent of unburned wood to the initial wood fuel (percent ratio) is very small
(less than 1%) for all the treatments and the control. The result has a benefit of saving fuel wood
for cooking that requires longer time. The study needs to be done for different sizes of pots
