Thermal Engineering

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http://etd.aau.edu.et/handle/12345678/143

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Browsing Thermal Engineering by Author "Abdulkadir Aman (PhD)"

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    Design and Simulation of Institutional Solar-powered Cookstove Using Thermal Storage System
    (Addis Ababa University, 2023-06) Tihun Birhanu; Abdulkadir Aman (PhD); Kamil Dino, (PhD)
    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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    Numerical Investigation on Charging Discharging of a PCM Using PV and Thermal Oil for Injera Baking Application.
    (Addis Ababa University, 2023-06) Meseret Alemu; Abdulkadir Aman (PhD); Gashaw Getent (Mr.) Co Advisor
    Millions of Ethiopians rely on bio mass, charcoal, and animal dung to supply their energy demands. All of this energy is used to bake injera, more than 50%. This traditional biomass based baking has an impact on women's and children's he alth, energy, and ability to attend school. Due to its abundant and readily accessible renewable energy source, solar energy had been considered to be a good alternative for cooking. However, because of its intermittent nature, there is a mismatch between the load and the solar energy that is available for the baking purpose, so a thermal storage system that provides the necessary energy has been integrated. T his study investigates th e thermal characteristic of the charging and discharge processes and main heat transfer processes in the injera baking system with PV which was integrated with the thermal storage system T his study was conducted beginning with review ing related papers, system design, data collection and data analysis in addition, performed m athematical and numerical model s and numerical simulation was conducted using a finite difference computational model for the thermal storages that was PCM and thermal oil The thermal oil was used to store energy and to transfer heat, furthermore, the dev eloped computational models are analyzed using MA TLAB programming software. F rom the numerical simulation result by using solar radiation data of Addis Ababa showed that the thermal storage has the capacity to store about 3 3 MJ during charging using const ant heat flux which was from the PV The amount of energy discharged from the PCM was 13.1 MJ and from the thermia oil was 3 .5 0 MJ by using natural convection heat transfer and the discharging and overall efficiency of the system w ere about 50.2 and 46.67 respectively. Also, the baking pan surface temperature stayed between 220 o c and 1 46.4 o c for about three hours . T his result was compared with different papers and it can be concluded that the numerical ly investigated solar powered Injera baking integrated with thermal storage showed a promising result.