Energy Science and Technology
Hamed Khoshkam; Kazem Atashkari; Mehdi Borji
Abstract
Carbon deposition has a serious effect on the failure mechanism of solid oxide fuel cells. A comprehensive investigation based on a two-dimensional model of a solid oxide fuel cell with the detailed electrochemical model is presented to study the mechanism and effects of carbon deposition and unsteady ...
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Carbon deposition has a serious effect on the failure mechanism of solid oxide fuel cells. A comprehensive investigation based on a two-dimensional model of a solid oxide fuel cell with the detailed electrochemical model is presented to study the mechanism and effects of carbon deposition and unsteady state porosity variation. Studies of this kind can be an aid to identify the SOFC optimal working conditions and provide an approximate fuel cell lifetime. It has been revealed that, due to carbon deposition, the porosity coefficient of the fuel cell decreases. Consequently, a reduction in the amount of fuel consumption along the fuel cell and the chemical and electrochemical reaction rates are resulted which can be clearly seen in the off-gases molar ratio. The percentage of output fuel changes in the timeframe is useful information for optimizing CHP systems including fuel cells. The percentage of the output water vapor, which usually increases compared to the input, decreases by 17% at the end of the working period. Also, unreacted methane in the output of the fuel cell increased by 12%; in other words, it is wasted. The other consequence of carbon deposition reduced electrochemical and chemical reaction rates and the reduction of temperature difference along the cell. The study shows that after 145 working days, the temperature difference along the cell varies from 117 °C for the starting time to 7 °C. Also, by reducing the current density, the cell output power density decreases by 72% after 145 working days.
Computational Fluid Dynamics (CFD)
mohammad saeed sharifi; Miralam Mahdi; Karim Maghsoudi Mehraban
Abstract
The shape of the air flow in the interior is heavily influenced by the air distribution system and the way air enters and exits. By numerically simulating flow by computational fluid dynamics, one can determine the flow pattern and temperature distribution and, with the help of the results, provide an ...
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The shape of the air flow in the interior is heavily influenced by the air distribution system and the way air enters and exits. By numerically simulating flow by computational fluid dynamics, one can determine the flow pattern and temperature distribution and, with the help of the results, provide an optimal design of the air conditioning system. In this study, a chamber was first constructed and the temperature distribution inside it was measured. There was a fan installed at the back of the chamber for drainage. At the chamber entrance, three inlet for entering the flow were considered. The air from the middle inlet was heated by a heater. To prevent heat loss, the body of the enclosure was insulated. Several temperature sensors were installed at certain positions of the chamber for temperature measurement. Using Fluent software, the model of a full-sized chamber was created. Meshing is a hybrid and was used as a boundary layer Mesh. The inlet and outlet temperature of the chamber and the air output rates as boundary conditions were used in the simulation. Numerical analysis for K-ε and K-ω turbulence models was performed and different wall conditions were investigated. The numerical simulation results were in good agreement with the measurement results. Using the K-ε turbulence model with a scalable wall function had a better accuracy than other models. Changes in velocity and temperature were presented in graphs and contours at different positions of the compartment.
Fluid Mechanics
Javad Shahbazi Karami; GH. Payganeh
Abstract
In this study, hot metal gas forming process of AA6063aluminumtubeis studied with a focus on heat transfer of both fluid and solid phases numerically. An experimental study is simultaneously conducted to validate the numerical method. Some of the most important outputs of the present study, are velocity ...
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In this study, hot metal gas forming process of AA6063aluminumtubeis studied with a focus on heat transfer of both fluid and solid phases numerically. An experimental study is simultaneously conducted to validate the numerical method. Some of the most important outputs of the present study, are velocity distribution of fluid inside the tube as well as the fluid in the gap between tube and matrices. As a result of non-homogenous distribution of temperature on tube surface, circulating flows are generated inside the tube which may have considerable effects on heat transfer phenomenon. It is seen that in 600 s after start, number of the circulating flows doubles. Analysis of temperature distribution reveals thatmiddle part of the tube reaches 500 ̊C after 600 s from process start and other parts have higher temperature. By applying an efficient control method for heater elements, temperature distribution of the tube reaches a homogenous form.
Manufacturing Processes
Abstract
Laser bending is an advanced process in sheet metal forming in which a laser heat source is used to shape the metal sheet. In this paper, temperature distribution in a mild steel sheet metal is investigated numerically and experimentally. Laser heat source is applied through curved paths in square sheet ...
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Laser bending is an advanced process in sheet metal forming in which a laser heat source is used to shape the metal sheet. In this paper, temperature distribution in a mild steel sheet metal is investigated numerically and experimentally. Laser heat source is applied through curved paths in square sheet metal parts. Finite element (FE) simulation is performed with the ABAQUS/CAE standard software package. Material property of AISI 1010 is used in FE model and experiments. The aim of this study is to identify the response related to deformation and characterize the effect of laser power with respect to the bending angle for a square sheet part. An experimental setup including a Nd:YAG laser Model IQL-10 with maximum mean laser power of 500 W is used for the experiments to verify FE analysis results. It is observed that numerical results are relatively in good agreement with the experimental results. Results also show that increasing laser power increases the bending angle.
