Effect of thermal shock on the grate of charcoal cook stoves from selected materials mixed in different ratios
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The purpose of this work was to determine the effect of thermal shock on the grate of charcoal cook stoves made from clay soil, Red soil and Anthill soil mixed with shell rock in different ratios. It involved testing the selected materials used in the grate of charcoal cook stoves for their thermal shock resistance. A number of SMEs in Uganda are involved in the production of energy saving charcoal cook stoves but their lifespan depends on the thermal shock resistance of the materials used in the grate of the charcoal stoves, yet limited information is available. The main objective of the study was to evaluate the effect of varying the mixing ratios of the selected materials used in the grate of charcoal cook stoves on thermal shock resistance specifically to evaluate the effect of firing on the grates and to determine the effect of thermal shock on the grates. The grates were molded from the three different soils mixed with shell rock in varying ratios, dried and then fired. They were analyzed from the laboratory using a furnace operated at 400 ̊ C where the grates were being heated for an hour, and some selected grates rapidly cooled by water quenching and others cooled at ambient conditions. The grates were then differently analyzed for crack initiation and crack propagation in the subsequent cycles. It was done for seven cycles on all the different grates. It was found out that clay soil mixed with shell rock in the ratio of 3:1 had the highest thermal shock resistance followed by Anthill soil mixed with shell rock in the ratio of 1:1. However, the 3:1 clay soil to shell rock grates were more prone to damage during firing compared to the rest of other grates. The grates respond differently to firing depending on the materials used, their mixing ratios and properties. Grates undergo crack initiation and propagation at heterogeneous rates basing on the materials used and the mixing ratios when subjected to thermal shock. The recommended material combination for making charcoal cook stoves according to the achieved test results of this project is clay and shell rock as the temper mixed in the ratio of 3:1.