The objective of this work is to develop a detailed numerical simulation of solar photovoltaic ce... more The objective of this work is to develop a detailed numerical simulation of solar photovoltaic cells in one, two, and three-dimensions. Such kind of numerical simulation can be used as a flexible research tool for the design and analysis of solar cells. The developed in-house simulation code has the advantage of conducting modifications of the suggested configurations to include effects not covered by the commercial simulation models. In addition, this tool is to serve as a test-bed simulator for the development of solar cells modeling and to design new material models. The photovoltaic solar cells governing equations are Poisson's equation, the hole and electron continuity equations. Poisson equation is generally used to get the voltages across the device. However, in the present work, it is used to obtain the value of the electrical charge. The governing equations along with the appropriate boundary conditions are solved numerically using a finite difference based method. The resulting system of coupled nonlinear equations is then solved using Newton method for nonlinear systems. The predicted results include illuminated current-voltage characteristic, and dark current-voltage characteristics of photovoltaic module. Comparisons between predicted results and corresponding measured values by manufacturer are conducted in order to validate the numerical simulation. A good agreement between predicted and measured results was prevailed.
Flow field design in PEM fuel cells has an important influence on both the power density and effi... more Flow field design in PEM fuel cells has an important influence on both the power density and efficiency of fuel cell systems. In order to effectively utilize the active area, flow distribution and current density should be as homogenous as possible. In addition, pressure losses should be minimized. The main objective of this work is to provide a comprehensive study of the flow field characteristics for different parallel flow channel configurations. The investigated channel configurations are parallel with various cross-sectional configurations. For each channel configuration pressure drop, species mass fraction, velocity, and current distributions are numerically predicted. In addition, performance curves are presented and discussed. The predicted performance parameters are compared with the corresponding available experimental data. Based on the computed results the optimum channel design is selected. Detailed results are presented and discussed. The present work would help PEM fu...
ABSTRACT A theoretical analysis for the onset of gas pull-through (entrainment) during discharge ... more ABSTRACT A theoretical analysis for the onset of gas pull-through (entrainment) during discharge from a stratified two-phase region through two vertically aligned side branches has been developed in this paper. Initially, a simplified point-sink model was developed; this was followed by the acquisition of a more accurate finite branch model. The predicted value of the critical height at the onset of gas entrainment was found to be a function of each branches’ corresponding Froude number (Fr1 and Fr2 ), as well as the ratio between the vertical distance connecting the centerlines of the two branches and the diameter of the branches (L/d). The predicted values of the critical heights were found to be consistent with the corresponding experimental data at different values of Fr1 , Fr2 and L/d. From the basis of the present models, it was established that when increasing the flow through the lower branch, the critical height increased for all values of Fr1 and L/d. In addition, it was found that increasing the vertical distance between the two branches, reduced the effects of the lower branch on the determination of the critical height.
ABSTRACT A new theoretical investigation has been conducted for the prediction of the critical he... more ABSTRACT A new theoretical investigation has been conducted for the prediction of the critical height at the onset of gas entrainment during single discharge from a stratified two-phase region through a branch installed on an inclined flat wall. Two models have been developed; a simplified point-sink model and a more-accurate finite-branch. The predicted critical height at the onset of gas entrainment was proven to be a function of Froude number (Fr) and density ratio of the interface fluids. The results of the predicted critical height at the onset of gas entrainment, at low values of Fr (
Volume 4: Energy Systems Analysis, Thermodynamics and Sustainability; Combustion Science and Engineering; Nanoengineering for Energy, Parts A and B, 2011
ABSTRACT A thermodynamic model for simulation the performance of a four-stroke direct-injection (... more ABSTRACT A thermodynamic model for simulation the performance of a four-stroke direct-injection (DI) diesel engine is developed. The simulation model includes detailed sub-models for fuel burning rate, combustion products, thermodynamic properties of working fluid, heat transfer, fluid flow, and both soot and NOx formation mechanisms. To validate the model, comparisons between experimental and predicted results for different engines, operating under different conditions were conducted. Comparisons show that there is a good concurrence between measured and predicted values. An optimization analysis is conducted for seeking an optimum variation of compression ratio to achieve pre-set objective target of constant minimum brake specific fuel consumption (bsfc). The optimization analysis is performed under the constrain that the maximum pressure and temperature inside the cylinder not exceed the maximum allowable pressure and temperature of the conventional engine (constant rc ). Varying compression ratio is optimized with the previous condition. Results indicated that, at the values of rc ranged between 16.4 and 17.8, the optimum bsfc is attained with an increase in brake power by about 3.8%, while the bsfc and soot emission are reduced by about 4.4% and 21%, respectively. In addition to an increase in NOx , maximum pressure (pmax ), and maximum temperature (Tmax ) by about 75%, 6% and 4.3%, respectively.
Volume 6: Fluids and Thermal Systems; Advances for Process Industries, Parts A and B, 2011
ABSTRACT Laminar flow in porous channels or tubes has received a great attention in recent years ... more ABSTRACT Laminar flow in porous channels or tubes has received a great attention in recent years due to its various applications. These applications include blood filtration in artificial kidney, blood flow in capillaries and oxygenations, transpiration, cooling of turbine blades, lubrication of ceramic machine parts, food processing, electronics cooling, gaseous diffusion, the extraction of geothermal energy, and nuclear reactor cooling systems. The present work, proposes the Galerkin method to solve the two dimensional electrically conducting flow in a semiporous channel under uniform magnetic field as governed by dimensionless: Hartman number (Ha), and Reynolds number (Re). The numerical results predict the flow field characteristics over wide ranges of Ha, and Re. These results are compared with other available analytical and numerical results at different values of Ha, and Re. Detailed results are presented and discussed.
Volume 4: Energy Systems Analysis, Thermodynamics and Sustainability; Combustion Science and Engineering; Nanoengineering for Energy, Parts A and B, 2011
ABSTRACT The objective of the present work is to develop a dynamic electro-thermal model for phot... more ABSTRACT The objective of the present work is to develop a dynamic electro-thermal model for photovoltaic cells to optimize both electrical and thermal performance of such systems. The thermal model is developed by generating the equivalent RC network (resistance-...
Volume 4: Energy Systems Analysis, Thermodynamics and Sustainability; Combustion Science and Engineering; Nanoengineering for Energy, Parts A and B, 2011
ABSTRACT The objective of this work is to develop a detailed numerical simulation of solar photov... more ABSTRACT The objective of this work is to develop a detailed numerical simulation of solar photovoltaic cells in one, two, and three-dimensions. Such kind of numerical simulation can be used as a flexible research tool for the design and analysis of solar cells. The developed in-house simulation code has the advantage of conducting modifications of the suggested configurations to include effects not covered by the commercial simulation models. In addition, this tool is to serve as a test-bed simulator for the development of solar cells modeling and to design new material models. The photovoltaic solar cells governing equations are Poisson’s equation, the hole and electron continuity equations. Poisson equation is generally used to get the voltages across the device. However, in the present work, it is used to obtain the value of the electrical charge. The governing equations along with the appropriate boundary conditions are solved numerically using a finite difference based method. The resulting system of coupled nonlinear equations is then solved using Newton method for nonlinear systems. The predicted results include illuminated current-voltage characteristic, and dark current-voltage characteristics of photovoltaic module. Comparisons between predicted results and corresponding measured values by manufacturer are conducted in order to validate the numerical simulation. A good agreement between predicted and measured results was prevailed.
Volume 5: Energy Systems Analysis, Thermodynamics and Sustainability; NanoEngineering for Energy; Engineering to Address Climate Change, Parts A and B, 2010
ABSTRACT Modeling of PV generator represents very important goal. Such modeling will allow conduc... more ABSTRACT Modeling of PV generator represents very important goal. Such modeling will allow conducting measurements without the constraints of environmental conditions. In addition it will save the use of an actual PV array, other related equipments and time. The objective of this research work is to develop an accurate and simplified photovoltaic source model. The developed model considers most of environmental variables such as: ambient temperature, solar radiation incident angle, radiation intensity, wind velocity and partial shading. Results of PV array model characteristics are easily obtained by connecting variable resistance across the PV arrays. The simulated characteristics are in good agreement with those obtained from the available experimental data; model can be used to achieve optimal choice and design of the power converter interfacing the PV generator to the utility. Further more, the model will allow choosing the suitable power converter control methods.
ABSTRACT This paper is aimed at improving the output voltage waveform of a single phase PWM inver... more ABSTRACT This paper is aimed at improving the output voltage waveform of a single phase PWM inverter. Two approaches is proposed, the first approach is based on selected harmonic elimination (SHE) of order up to 7th harmonic, for minimizing harmonic distortion and modulating amplitude of the fundamental component of the output voltage waveform. For the first time, the Levenberg–Marquardt algorithm (LMA) is used for determining the SHE switching angles of the inverter switches. The second approach is based on ripple current minimization using LMA. The high-frequency harmonic components are easily removed using additional passive filter circuits. A simulation model is developed using PSIM for the inverter to verify the proposed approaches by applying the computed switching angles to the gates of the inverter MOSFETs. An experimental system was implemented to demonstrate the effectiveness of the proposed approaches by using PIC16F877 microcontroller. Analysis of the voltage THD as influenced by the amplitude modulation index is made using MATLAB based on the computed switching angles. The voltage THD increases dramatically with decreasing the modulation index, whereas, the corresponding increase of the voltage THD is smaller on using the SHE.
A theoretical investigation has been conducted for the prediction of the critical height at the o... more A theoretical investigation has been conducted for the prediction of the critical height at the onset of gas entrainment during single discharge from a stratified, two-phase region through a side branch with a finite diameter. Two different models have been developed, a ...
The objective of this work is to develop a detailed numerical simulation of solar photovoltaic ce... more The objective of this work is to develop a detailed numerical simulation of solar photovoltaic cells in one, two, and three-dimensions. Such kind of numerical simulation can be used as a flexible research tool for the design and analysis of solar cells. The developed in-house simulation code has the advantage of conducting modifications of the suggested configurations to include effects not covered by the commercial simulation models. In addition, this tool is to serve as a test-bed simulator for the development of solar cells modeling and to design new material models. The photovoltaic solar cells governing equations are Poisson's equation, the hole and electron continuity equations. Poisson equation is generally used to get the voltages across the device. However, in the present work, it is used to obtain the value of the electrical charge. The governing equations along with the appropriate boundary conditions are solved numerically using a finite difference based method. The resulting system of coupled nonlinear equations is then solved using Newton method for nonlinear systems. The predicted results include illuminated current-voltage characteristic, and dark current-voltage characteristics of photovoltaic module. Comparisons between predicted results and corresponding measured values by manufacturer are conducted in order to validate the numerical simulation. A good agreement between predicted and measured results was prevailed.
Flow field design in PEM fuel cells has an important influence on both the power density and effi... more Flow field design in PEM fuel cells has an important influence on both the power density and efficiency of fuel cell systems. In order to effectively utilize the active area, flow distribution and current density should be as homogenous as possible. In addition, pressure losses should be minimized. The main objective of this work is to provide a comprehensive study of the flow field characteristics for different parallel flow channel configurations. The investigated channel configurations are parallel with various cross-sectional configurations. For each channel configuration pressure drop, species mass fraction, velocity, and current distributions are numerically predicted. In addition, performance curves are presented and discussed. The predicted performance parameters are compared with the corresponding available experimental data. Based on the computed results the optimum channel design is selected. Detailed results are presented and discussed. The present work would help PEM fu...
ABSTRACT A theoretical analysis for the onset of gas pull-through (entrainment) during discharge ... more ABSTRACT A theoretical analysis for the onset of gas pull-through (entrainment) during discharge from a stratified two-phase region through two vertically aligned side branches has been developed in this paper. Initially, a simplified point-sink model was developed; this was followed by the acquisition of a more accurate finite branch model. The predicted value of the critical height at the onset of gas entrainment was found to be a function of each branches’ corresponding Froude number (Fr1 and Fr2 ), as well as the ratio between the vertical distance connecting the centerlines of the two branches and the diameter of the branches (L/d). The predicted values of the critical heights were found to be consistent with the corresponding experimental data at different values of Fr1 , Fr2 and L/d. From the basis of the present models, it was established that when increasing the flow through the lower branch, the critical height increased for all values of Fr1 and L/d. In addition, it was found that increasing the vertical distance between the two branches, reduced the effects of the lower branch on the determination of the critical height.
ABSTRACT A new theoretical investigation has been conducted for the prediction of the critical he... more ABSTRACT A new theoretical investigation has been conducted for the prediction of the critical height at the onset of gas entrainment during single discharge from a stratified two-phase region through a branch installed on an inclined flat wall. Two models have been developed; a simplified point-sink model and a more-accurate finite-branch. The predicted critical height at the onset of gas entrainment was proven to be a function of Froude number (Fr) and density ratio of the interface fluids. The results of the predicted critical height at the onset of gas entrainment, at low values of Fr (
Volume 4: Energy Systems Analysis, Thermodynamics and Sustainability; Combustion Science and Engineering; Nanoengineering for Energy, Parts A and B, 2011
ABSTRACT A thermodynamic model for simulation the performance of a four-stroke direct-injection (... more ABSTRACT A thermodynamic model for simulation the performance of a four-stroke direct-injection (DI) diesel engine is developed. The simulation model includes detailed sub-models for fuel burning rate, combustion products, thermodynamic properties of working fluid, heat transfer, fluid flow, and both soot and NOx formation mechanisms. To validate the model, comparisons between experimental and predicted results for different engines, operating under different conditions were conducted. Comparisons show that there is a good concurrence between measured and predicted values. An optimization analysis is conducted for seeking an optimum variation of compression ratio to achieve pre-set objective target of constant minimum brake specific fuel consumption (bsfc). The optimization analysis is performed under the constrain that the maximum pressure and temperature inside the cylinder not exceed the maximum allowable pressure and temperature of the conventional engine (constant rc ). Varying compression ratio is optimized with the previous condition. Results indicated that, at the values of rc ranged between 16.4 and 17.8, the optimum bsfc is attained with an increase in brake power by about 3.8%, while the bsfc and soot emission are reduced by about 4.4% and 21%, respectively. In addition to an increase in NOx , maximum pressure (pmax ), and maximum temperature (Tmax ) by about 75%, 6% and 4.3%, respectively.
Volume 6: Fluids and Thermal Systems; Advances for Process Industries, Parts A and B, 2011
ABSTRACT Laminar flow in porous channels or tubes has received a great attention in recent years ... more ABSTRACT Laminar flow in porous channels or tubes has received a great attention in recent years due to its various applications. These applications include blood filtration in artificial kidney, blood flow in capillaries and oxygenations, transpiration, cooling of turbine blades, lubrication of ceramic machine parts, food processing, electronics cooling, gaseous diffusion, the extraction of geothermal energy, and nuclear reactor cooling systems. The present work, proposes the Galerkin method to solve the two dimensional electrically conducting flow in a semiporous channel under uniform magnetic field as governed by dimensionless: Hartman number (Ha), and Reynolds number (Re). The numerical results predict the flow field characteristics over wide ranges of Ha, and Re. These results are compared with other available analytical and numerical results at different values of Ha, and Re. Detailed results are presented and discussed.
Volume 4: Energy Systems Analysis, Thermodynamics and Sustainability; Combustion Science and Engineering; Nanoengineering for Energy, Parts A and B, 2011
ABSTRACT The objective of the present work is to develop a dynamic electro-thermal model for phot... more ABSTRACT The objective of the present work is to develop a dynamic electro-thermal model for photovoltaic cells to optimize both electrical and thermal performance of such systems. The thermal model is developed by generating the equivalent RC network (resistance-...
Volume 4: Energy Systems Analysis, Thermodynamics and Sustainability; Combustion Science and Engineering; Nanoengineering for Energy, Parts A and B, 2011
ABSTRACT The objective of this work is to develop a detailed numerical simulation of solar photov... more ABSTRACT The objective of this work is to develop a detailed numerical simulation of solar photovoltaic cells in one, two, and three-dimensions. Such kind of numerical simulation can be used as a flexible research tool for the design and analysis of solar cells. The developed in-house simulation code has the advantage of conducting modifications of the suggested configurations to include effects not covered by the commercial simulation models. In addition, this tool is to serve as a test-bed simulator for the development of solar cells modeling and to design new material models. The photovoltaic solar cells governing equations are Poisson’s equation, the hole and electron continuity equations. Poisson equation is generally used to get the voltages across the device. However, in the present work, it is used to obtain the value of the electrical charge. The governing equations along with the appropriate boundary conditions are solved numerically using a finite difference based method. The resulting system of coupled nonlinear equations is then solved using Newton method for nonlinear systems. The predicted results include illuminated current-voltage characteristic, and dark current-voltage characteristics of photovoltaic module. Comparisons between predicted results and corresponding measured values by manufacturer are conducted in order to validate the numerical simulation. A good agreement between predicted and measured results was prevailed.
Volume 5: Energy Systems Analysis, Thermodynamics and Sustainability; NanoEngineering for Energy; Engineering to Address Climate Change, Parts A and B, 2010
ABSTRACT Modeling of PV generator represents very important goal. Such modeling will allow conduc... more ABSTRACT Modeling of PV generator represents very important goal. Such modeling will allow conducting measurements without the constraints of environmental conditions. In addition it will save the use of an actual PV array, other related equipments and time. The objective of this research work is to develop an accurate and simplified photovoltaic source model. The developed model considers most of environmental variables such as: ambient temperature, solar radiation incident angle, radiation intensity, wind velocity and partial shading. Results of PV array model characteristics are easily obtained by connecting variable resistance across the PV arrays. The simulated characteristics are in good agreement with those obtained from the available experimental data; model can be used to achieve optimal choice and design of the power converter interfacing the PV generator to the utility. Further more, the model will allow choosing the suitable power converter control methods.
ABSTRACT This paper is aimed at improving the output voltage waveform of a single phase PWM inver... more ABSTRACT This paper is aimed at improving the output voltage waveform of a single phase PWM inverter. Two approaches is proposed, the first approach is based on selected harmonic elimination (SHE) of order up to 7th harmonic, for minimizing harmonic distortion and modulating amplitude of the fundamental component of the output voltage waveform. For the first time, the Levenberg–Marquardt algorithm (LMA) is used for determining the SHE switching angles of the inverter switches. The second approach is based on ripple current minimization using LMA. The high-frequency harmonic components are easily removed using additional passive filter circuits. A simulation model is developed using PSIM for the inverter to verify the proposed approaches by applying the computed switching angles to the gates of the inverter MOSFETs. An experimental system was implemented to demonstrate the effectiveness of the proposed approaches by using PIC16F877 microcontroller. Analysis of the voltage THD as influenced by the amplitude modulation index is made using MATLAB based on the computed switching angles. The voltage THD increases dramatically with decreasing the modulation index, whereas, the corresponding increase of the voltage THD is smaller on using the SHE.
A theoretical investigation has been conducted for the prediction of the critical height at the o... more A theoretical investigation has been conducted for the prediction of the critical height at the onset of gas entrainment during single discharge from a stratified, two-phase region through a side branch with a finite diameter. Two different models have been developed, a ...
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