Modeling of Various Transport Processes in a Natural Gas Reformer

2005 ◽  
Author(s):  
Jinliang Yuan ◽  
Fuan Ren ◽  
Bengt Sunde´n ◽  
Peiting Sun
Keyword(s):  
Natural Gas ◽  
Three Dimensional ◽  
Catalyst Layer ◽  
Gas Permeation ◽  
Transport Processes ◽  
Fuel Gas ◽  
Porous Catalyst ◽  
Thermal Boundary Conditions ◽  
Parametric Studies ◽  
Solid Walls

In this study, a three-dimensional calculation method has been developed to simulate and analyze steam reforming of natural gas, and the effects on various transport processes in a duct from a compact steam reformer. The reformer conditions such as the combined thermal boundary conditions on solid walls, mass balances associated with the reforming reactions and gas permeation to/from the porous catalyst layer are applied in the analysis. Momentum and heat transport together with fuel gas species equations have been solved by coupled source terms and variable thermo-physical properties (such as density, viscosity, specific heat, etc.) of the fuel gas mixture. The predicted results are presented and discussed for a composite duct consisting of a porous catalyst reaction area, the flow duct and solid layers. Parametric studies are conducted and the results show that the variables, such as fuel reformer temperatures and duct configuration, have significant effects on the transport processes and reformer performance.

Analysis of Transport Processes and Chemical Reaction in Combustion Duct of Compact Methane Reformer

2010 ◽  
Author(s):  
Guogang Yang ◽  
Wei Wei ◽  
Jinliang Yuan ◽  
Danting Yue ◽  
Xinrong Lv
Keyword(s):  
Heat Transfer ◽  
Chemical Reaction ◽  
Porous Layer ◽  
Catalytic Combustion ◽  
Gas Flow ◽  
Three Dimensional ◽  
Gas Permeation ◽  
Transport Processes ◽  
Fuel Gas ◽  
Porous Catalyst

A composite combustion duct in compact methane reformers consists of a gas flow channel, porous layer and solid plates. There are various transport processes appeared, such as gas flow in the channel, multi-component species convection/diffusion in the porous layer, and heat transfer. They are further coupled by methane catalytic combustion in the porous layer, which affects the reformer overall performance and reliability. By three dimensional CFD approach, the reacting gas flow and heat transfer processes were numerically studied. The reformer conditions such as mass balances associated with the chemical reaction and gas permeation to/from the porous layer are implemented in the calculation. The results reveal that the catalytic combustion reaction is confined in a thin porous catalyst area close to fuel gas flow duct. Transport processes of the fuel gas species and temperature distribution are significantly affected by the reactions.

Effects of Various Reactions on the Gas Flow and Heat Transfer in an Anode Duct of ITSOFCs

2005 ◽  
Author(s):  
Jinliang Yuan ◽  
Bengt Sunde´n
Keyword(s):  
Heat Transfer ◽  
Gas Flow ◽  
Porous Electrode ◽  
Gas Permeation ◽  
Transport Processes ◽  
Operating Conditions ◽  
Electrochemical Reactions ◽  
Fuel Gas ◽  
Internal Reforming ◽  
Porous Anode

Recently, there has been considerable interest in the internal reforming reactions of solid oxide fuel cells (SOFCs) using methane or natural gas via. The internal reforming and electrochemical reactions appear in the porous anode layer, and may lead to inhomogeneous temperature and gas species distributions according to the reaction kinetics. A three-dimensional calculation method has been further developed to simulate and analyze the internal reforming and the electrochemical reactions, and the effects on various transport processes in a thick anode duct. In this study, the composite duct consists of a porous anode, fuel flow duct and solid current connector. Momentum, heat transport and gas species equations have been solved by coupled source terms and variable physical properties (density, viscosity, specific heat, etc.) of the fuel gas mixture. The combined thermal boundary conditions on solid walls, mass balances (generation and consumption) associated with the various reactions and gas permeation to/from the porous electrode are applied in the analysis. Simulation results show that the internal reforming and the electrochemical reactions, and operating conditions are significant for fuel gas transport and heat transfer in the anode.

scholarly journals Topographically Controlled Marangoni-Rayleigh-Bénard Convection in Liquid Metals

Fluids ◽  
2021 ◽  
Vol 6 (12) ◽  
pp. 447
Author(s):  
Marcello Lappa ◽  
Aydin Sayar ◽  
Wasim Waris
Keyword(s):  
Liquid Metals ◽  
Three Dimensional ◽  
Viscous Effects ◽  
Thermal Boundary Conditions ◽  
Vertical Extension ◽  
Bénard Convection ◽  
Benard Convection ◽  
Rayleigh Benard Convection ◽  
Rayleigh Benard ◽  
Solid Walls

Convection induced in a layer of liquid with a top free surface by a distribution of heating elements at the bottom can be seen as a variant of standard Marangoni–Rayleigh–Bénard Convection where in place of a flat boundary at constant temperature delimiting the system from below, the underlying thermal inhomogeneity reflects the existence of a topography. In the present work, this problem is investigated numerically through solution of the governing equations for mass, momentum and energy in their complete, three-dimensional time-dependent and non-linear form. Emphasis is given to a class of liquids for which thermal diffusion is expected to dominate over viscous effects (liquid metals). Fixing the Rayleigh and Marangoni number to 104 and 5 × 103, respectively, the sensitivity of the problem to the geometrical, kinematic and thermal boundary conditions is investigated parametrically by changing: the number and spacing of heating elements, their vertical extension, the nature of the lateral boundary (solid walls or periodic boundary) and the thermal behavior of the portions of bottom wall between adjoining elements (assumed to be either adiabatic or at the same temperature of the hot blocks). It is shown that, like the parent phenomena, this type of thermal flow is extremely sensitive to the specific conditions considered. The topography can be used to exert a control on the emerging flow in terms of temporal response and patterning behavior.

Mathematical Model Investigation of Far-Field Transport of Ocean-Dumped Sewage Sludge Related to Remote Sensing

1982 ◽  
Vol 14 (3) ◽  
pp. 33-39
Author(s):  
C Y Kuo
Keyword(s):  
New York ◽  
Sewage Sludge ◽  
Laboratory Data ◽  
Three Dimensional ◽  
Approximate Model ◽  
Transport Processes ◽  
Far Field ◽  
New York Bight ◽  
Mean Current

An existing, three-dimensional, Eulerian-Lagrangian finite-difference model was modified and used to examine the far-field transport processes of dumped sewage sludge in the New York Bight. Both in situ and laboratory data were utilized in an attempt to approximate model inputs such as mean current speed, vertical and horizontal diffusion coefficients, particle size distributions, and specific gravities. Concentrations of the sludge near the sea surface predicted from the computer model were compared qualitatively with those remotely sensed.

scholarly journals CFD Modelling of a Hydrogen/Air PEM Fuel Cell with a Serpentine Gas Distributor

Processes ◽  
2021 ◽  
Vol 9 (3) ◽  
pp. 564
Author(s):  
Alessandro d’Adamo ◽  
Matteo Riccardi ◽  
Massimo Borghi ◽  
Stefano Fontanesi
Keyword(s):  
Fuel Cells ◽  
Proton Exchange Membrane ◽  
Catalyst Layer ◽  
Active Surface ◽  
Reaction Rates ◽  
Transport Processes ◽  
Proton Exchange ◽  
Sustainable Mobility ◽  
Cfd Modelling ◽  
Gas Distributor

Hydrogen-fueled fuel cells are considered one of the key strategies to tackle the achievement of fully-sustainable mobility. The transportation sector is paying significant attention to the development and industrialization of proton exchange membrane fuel cells (PEMFC) to be introduced alongside batteries, reaching the goal of complete de-carbonization. In this paper a multi-phase, multi-component, and non-isothermal 3D-CFD model is presented to simulate the fluid, heat, and charge transport processes developing inside a hydrogen/air PEMFC with a serpentine-type gas distributor. Model results are compared against experimental data in terms of polarization and power density curves, including an improved formulation of exchange current density at the cathode catalyst layer, improving the simulation results’ accuracy in the activation-dominated region. Then, 3D-CFD fields of reactants’ delivery to the active electrochemical surface, reaction rates, temperature distributions, and liquid water formation are analyzed, and critical aspects of the current design are commented, i.e., the inhomogeneous use of the active surface for reactions, limiting the produced current and inducing gradients in thermal and reaction rate distribution. The study shows how a complete multi-dimensional framework for physical and chemical processes of PEMFC can be used to understand limiting processes and to guide future development.

Comparison Between Two-Shaft Simple and Single-Shaft Recuperated Brayton Cycles Using Different Types of Gaseous Fuels

2010 ◽  
Author(s):  
A. K. Malkogianni ◽  
A. Tourlidakis ◽  
A. L. Polyzakis
Keyword(s):  
Natural Gas ◽  
Gas Turbines ◽  
Alternative Fuels ◽  
High Efficiency ◽  
Heating Value ◽  
Gaseous Fuels ◽  
Oil And Natural Gas ◽  
Parametric Studies ◽  
The Impact ◽  
Lower Heating

Geopolitical issues give rise to problems in the smooth and continuous flow of oil and natural gas from the production countries to the consumers’ development countries. In addition, severe environmental issues such as greenhouse gas emissions, eventually guide the consumers to fuels more suitable to the present situation. Alternative fuels such as biogas and coal gas have recently become more attractive because of their benefits, especially for electricity generation. On the other hand, the use of relatively low heating value fuels has a significant effect to the performance parameters of gas turbines. In this paper, the impact of using four fuels with different heating value in the gas turbine performance is simulated. Based on the high efficiency and commercialization criteria, two types of engines are chosen to be simulated: two-shaft simple and single-shaft recuperated cycle gas turbines. The heating values of the four gases investigated, correspond to natural gas and to a series of three gases with gradually lower heating values than that of natural gas. The main conclusions drawn from this design point (DP) and off-design (OD) analysis is that, for a given TET, efficiency increases for both engines when gases with low heating value are used. On the contrary, when power output is kept constant, the use of gases with low heating value will result in a decrease of thermal efficiency. A number of parametric studies are carried out and the effect of operating parameters on performance is assessed. The analysis is performed with customized software, which has been developed for this purpose.

Error Assessment and Error Reduction in Production-Level RANS-Based Drag Predictions

2003 ◽  
Author(s):  
Donald W. Davis ◽  
Scot A. Slimon
Keyword(s):  
Fourth Order ◽  
Grid Cell ◽  
Stretch Ratio ◽  
Error Assessment ◽  
Artificial Dissipation ◽  
Grid Approach ◽  
Parametric Studies ◽  
Drag Prediction ◽  
Richardson’S Extrapolation ◽  
Solid Walls

Assessments of the effects of several numerical parameters on RANS-based drag prediction accuracy are presented. The parameters include grid cell size adjacent to solid walls, grid stretch ratio, grid stretch transition, artificial dissipation scheme, and artificial dissipation coefficient. Results from extensive parametric studies on a two-dimensional flat plate are reported. Based on the results of these studies, guidelines for high-accuracy drag predictions using both second- and fourth-order accurate, finite-difference-based solvers are proposed. In addition, error assessments obtained with a single grid using second- and fourth-order accurate solutions are compared to multiple-grid Richardson’s extrapolation approaches. The single-grid approach is shown to provide a significant improvement in both accuracy and error assessment relative to the multiple-grid approach.

Gas Turbine Combined Cycle With CO2-Capture Using Auto-Thermal Reforming of Natural Gas

2000 ◽  
Author(s):  
Thormod Andersen ◽  
Hanne M. Kvamsdal ◽  
Olav Bolland
Keyword(s):  
Natural Gas ◽  
Gas Turbine ◽  
Process Integration ◽  
Combined Cycle ◽  
Co2 Removal ◽  
Gas Turbine Combustor ◽  
Chemical Absorption ◽  
Fuel Gas ◽  
The Impact ◽  
Water Gas

A concept for capturing and sequestering CO2 from a natural gas fired combined cycle power plant is presented. The present approach is to decarbonise the fuel prior to combustion by reforming natural gas, producing a hydrogen-rich fuel. The reforming process consists of an air-blown pressurised auto-thermal reformer that produces a gas containing H2, CO and a small fraction of CH4 as combustible components. The gas is then led through a water gas shift reactor, where the equilibrium of CO and H2O is shifted towards CO2 and H2. The CO2 is then captured from the resulting gas by chemical absorption. The gas turbine of this system is then fed with a fuel gas containing approximately 50% H2. In order to achieve acceptable level of fuel-to-electricity conversion efficiency, this kind of process is attractive because of the possibility of process integration between the combined cycle and the reforming process. A comparison is made between a “standard” combined cycle and the current process with CO2-removal. This study also comprise an investigation of using a lower pressure level in the reforming section than in the gas turbine combustor and the impact of reduced steam/carbon ratio in the main reformer. The impact on gas turbine operation because of massive air bleed and the use of a hydrogen rich fuel is discussed.

Three-Dimensional Natural Convection From Vertical Heated Plates With Adjoining Cool Surfaces

1992 ◽  
Vol 114 (1) ◽  
pp. 115-120 ◽  
Author(s):  
B. W. Webb ◽  
T. L. Bergman
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Control Volume ◽  
Three Dimensional ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Uniform Heat Flux ◽  
Infrared Thermal Imaging ◽  
Transfer Rates ◽  
Thermal Boundary Conditions

Natural convection in an enclosure with a uniform heat flux on two vertical surfaces and constant temperature at the adjoining walls has been investigated both experimentally and theoretically. The thermal boundary conditions and enclosure geometry render the buoyancy-induced flow and heat transfer inherently three dimensional. The experimental measurements include temperature distributions of the isoflux walls obtained using an infrared thermal imaging technique, while the three-dimensional equations governing conservation of mass, momentum, and energy were solved using a control volume-based finite difference scheme. Measurements and predictions are in good agreement and the model predictions reveal strongly three-dimensional flow in the enclosure, as well as high local heat transfer rates at the edges of the isoflux wall. Predicted average heat transfer rates were correlated over a range of the relevant dimensionless parameters.

Coupled Heat and Mass Transfer CFD Model for Methane Hydrate

2015 ◽  
Author(s):  
Eugenio Turco Neto ◽  
M. A. Rahman ◽  
Syed Imtiaz ◽  
Thiago dos Santos Pereira ◽  
Fernanda Soares de Sousa
Keyword(s):  
Natural Gas ◽  
Multiphase Flow ◽  
Gas Hydrate ◽  
Gas Flow ◽  
Three Dimensional ◽  
Hydrate Formation ◽  
Cfd Model ◽  
Flow Metering ◽  
Ansys Cfx ◽  
Gas Hydrate Formation

The gas hydrates problem has been growing in offshore deep water condition where due to low temperature and high pressure hydrate formation becomes more favorable. Several studies have been done to predict the influence of gas hydrate formation in natural gas flow pipeline. However, the effects of multiphase hydrodynamic properties on hydrate formation are missing in these studies. The use of CFD to simulate gas hydrate formation can overcome this gap. In this study a computational fluid dynamics (CFD) model has been developed for mass, heat and momentum transfer for better understanding natural gas hydrate formation and its migration into the pipelines using ANSYS CFX-14. The problem considered in this study is a three-dimensional multiphase-flow model based on Simon Lo (2003) study, which considered the oil-dominant flow in a pipeline with hydrate formation around water droplets dispersed into the oil phase. The results obtained in this study will be useful in designing a multiphase flow metering and a pump to overcome the pressure drop caused by hydrate formation in multiphase petroleum production.

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