Abstract:
The traditional three-stone fire is used in many households in rural areas of developing countries. These open fires are very inefficient at converting stored chemical energy into heat from biomass fuel needed each year for basic cooking. Currently, different types improved biomass cooking stoves are being introduced and distributed in Ethiopia. The key to maintaining an improved stove is careful control of the air supply. This study was conducted on stoves with different number of air inlets to evaluate and compare their burning efficiencies. In this study, five types of wood burning stoves with different numbers of air inlets were designed, fabricated and their performances were tested. Equal weights of woods were used for cooking rice of equal weights in each of the pots. All the pots were placed at the same distance from fire. The tests were repeated five times. Comparisons were made by taking food, stove body and stove smoke outlet temperatures. Three parameters were selected for the comparison. These were time to reach initial cooking temperature of 75oC, maximum temperature reached during cooking and effective cooking times. Parameter tests were made by one-way ANOVA followed by pair comparisons whenever significant differences were obtained. Stove body and smoke outlet temperatures were first plotted and areas under the curves were calculated. The treatments showed significant differences on time to initiate cooking at p = 0.05 level. Pair comparisons showed stoves with 3 and 4 air inlets different (around 10.5 minutes) from the one air inlet (15 minutes). No such significant differences were observed for the maximum temperature and effective times of cooking. The stove with one air inlet exhibited the highest relative heat energy loss through the body while the three air inlet showed the least (18% less).The stove with four inlets had the highest relative heat loss through the smoke outlet and again the one with three air inlets showed the lowest loss (17% less). All in all, in this test the three air inlet stove showed better combined performance over all the rest onset of cooking than 2 air inlet stove. Over all the results, the stove with 3 air inlets is slightly shows a better performance than the other stoves.
