Computational Fluid Dynamics Modeling of Ugastove Charcoal Cookstove

Abstract

About half of the world’s population cook over an open biomass fire. These traditional stoves are characterized by very low efficiencies and harmful gas emissions. Over the last three decades there have been efforts to improve the design of traditional stoves. These stoves are expensive to manufacture because the design requires extensive experimentation under controlled conditions which are expensive, time consuming and difficult to control. Ugastove is one of improved cook stoves which is commonly used for cooking and heating in Uganda. It has a thermal efficiency of up to 35 %. Though there are numerous aspects that can be utilized to improve the efficiency of these stoves, this thesis develops the effect of the stove geometry on its heat transfer efficiency using computational fluid dynamics (CFD). The CFD modeling of locally manufactured improved stoves in Uganda is not extensive for charcoal stoves and there is still little scientific knowledge used to improve consequent designs. In this study, Solid Edge V16 was used to model different geometries of Ugastoves and CFD analysis was carried out for the dissimilar geometries of the stove to evaluate the behavior of heat transfer and flow during cooking using ANSYS FLUENT 2019R1 while utilizing Fluid Flow codes. The efficiency of the Ugastove, predicted from the CFD simulations was 33.8 %, closely approximating experimental data. The original geometry of the stove was altered to determine the effect on the stove efficiency. Efficiency of 42.7 % was achieved when the size of the holes in the combustion chamber reduced from 30 mm to 2.5 mm, and their number increased from nine (9) to twelve (12) and with the thickness of the clay lining increased from 35 mm to 45 mm, the thermal efficiency increased up to 46.7 %. The Ugastove’s efficiency can therefore be increased by these design changes that can be easily adapted in the current design on the market. However, in order to achieve efficiency more than 50 %; different parameters and radiation models can be used to simulate the stove, a different fuel for example briquettes can be used to check if the efficiency is affected by type of fuel. The Stoves are sometimes used in closed kitchen environment, therefore study using close-kitchen environments can be studied