Storage of thermal energy has become a growing area of interest amongst researchers over the past few decades. This is so because of the wide variety of applications that can benefit from this technology. When perfected, waste heat from industrial plants and the sun can be stored for reuse at a later point in time, thus improving the energy efficiency of the system. Heat loss is a significant challenge that affects the efficiency of a thermal storage system especially at the high temperature range. In minimizing heat loss rate of thermal insulation layer, this work aims to use simulation models to determine and minimize rate of heat loss of a simulated cylindrical kaolin thermal insulator within the working temperature range of 800 -1000 o C. Two direction were used which are radial and axial. They were simulated and analyzed one after the other. Two simulation software were employed to validate the results from each of them. Length of thermal insulation, temperature of inner surface and ambient temperature were the independent variables accounted for this work while the rate of heat loss at the outer surface was the dependent variable. In the axial direction, the dependent variable was more sensitive to changes in the independent variables compared to the radial direction. The change in the length of the thermal insulation layer had the highest impact on the dependent variable followed by the temperature of the internal surface and then lastly by the combined effect of these two factors. The effect of ambient temperature was insignificant. From the results of the work, suggestion was made from the simulation results, that the length of 0.22 m will be used to construct a portable thermal storage unit within the operating temperature range of 700 -900 o C. In conclusion, results will also serve as framework for the simulation at higher working temperatures.
Abstract. The study explored the production of biogas from a composite of Lemon grass and Poultry droppings by studying the total gas pressure exerted on a sealed near-cylindrical plastic container used as a digester. The composite pre-fermented substrates were mixed with water and the formed slurry was digested for a month. The temperature was kept relatively constant by lagging the digester with fiberglass wool. The exerted stress on the digester by the produced biogas was determined using a tri-axial quarter-bridge strain gage rectangular rosette, carefully fixed to the external surface of the plastic digester. Subsequently, the total pressure exerted on the wall of the digester container was determined. The daily gas production potential in form of computed pressure is presented. Results showed a maximum gas pressure of 31,200 pascal above atmosphere produced from the composite over the period of four weeks. The research demonstrated that pressure changes at relatively constant volume can be used to monitor gas production.
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