Design and Simulation of Institutional Solar-powered Cookstove Using Thermal Storage System
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Date
2023-06
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Addis Ababa University
Abstract
The world's demand for energy is rising quickly, yet conventional energy supplies are also declining. Future energy demands must thus be supplied and increased securely and efficiently. One of the most pressing issues of the twenty-first century is the sustainable production and use of renewable energy. A dependable supply of clean, affordable energy for everybody must be addressed. Because of that, this study determined if a solar-powered institutional cook stove with thermal energy storage that uses commercial SHELL THERMIA OIL B as the heat transfer medium as well as 40% KNO3+60% NaNO3 potassium nitrate salt (Solar Salt) as PCM for institutional food preparing was feasible. A mixture of 41L HTF (bulk temperatures up to 320ºC, and film temperature up to 340ºC) and 42 sealed copper tubes (Internal diameter 62.611 mm, 2 mm thickness 300 mm height) carrying a total of 60 kg of PCM (melting point range of 210-220°C and the Latent heat fusion 108.67 KJ/Kg)is used to store heat. The HTF was filled in the storage compartment to cover the copper tubes and is assumed to fit within cylinder jackets that wrap around the tubes and also operate as a heat transfer medium. A heater having 4500 W and 220 V input power from photovoltaic system with temperature control device is immersed inside storage during the charging phase. The ANSYS software is used to simulate the proposed model's thermal storage unit's transient behavior. ANSYS Workbench was utilized in a step-by-step fashion to model the process. A pressure-based solver was employed for melting/solidification processes, and for pressure-velocity coupling, the Semi-implicit pressure-linked equation technique was used. Grid independence assessment is also performed in order to choose the ideal grid size with the best solution and the lowest computing cost. The thermal storage's performance was assessed utilizing constant heat flux. The developed model's numerical study was solved numerically using an enthalpy-porosity approach and validated against experimental data. The results demonstrated that the CFD simulation using ANSYS Fluent for the stove was appropriately validated. Based on the simulation results, a performance investigation was carried out. The thermal storage was able to store 53.5MJ of energy in 3.8889 hours of charging time. The overall cooking, charging, and discharging efficiencies were 61.46%, 71.52%, and 85.62%, respectively. In the case of a convective heat transfer coefficient of 244 W/m2 K, the phase change material and heat transfer fluid demonstrated good heat retention of 5 h. Finally, the results indicate expanding the application of solar cooking at the institutional level is visible.
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Keywords
Thermal Storage System, Solar-powered Cookstove, Simulation, Design