THE EFFECT OF SMOKE OUTLET CLOSING TIME ON THE COOKING DURATION AND TEMPERATURE OF COOKSTOVE

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