The traditional three-stone fire is used in many households in rural areas of developing countries. These open fires are very inefficient at converting energy into heat for cooking. In order to improve energy security in developing countries modern cooking fuels and cook stove technologies are introduced and people are encouraged to switch to modern cooking technologies. Tikikil stove is one of improved cook stove which is currently used for cooking and heating needs in Ethiopia. Even though there are several factors that can be considered to improve the efficiency of these cook stove, this thesis enhance the impact or effect that geometry of the stoves has on its heat transfer efficiency.rnIn this work, SOLID WORK 2012 is used to model various geometries of the biomass cook stoves and a computational fluid dynamics (CFD) analysis has also been carried out for the different geometries of stove to analyze the flow behavior of gas, heat transfer behavior during the cooking period using Autodesk Simulation CFD 2012. For Tikikil stove the computational results were compared and validated with the experimental data. From experimental data thermal efficiency result is 27%, analytically using surface temperature measured the contributions of each mode of heat transfers are calculated also thermal efficiency is computed and value gained is 21.7%, finally using CFD analysis thermal efficiency obtained is 30.1%. Based on CFD simulation results of the different new geometry models, a cook stove geometry that gives significant improvement on performance is suggested which gives 50.1% of thermal efficiency by computing CFD output parameter.