Computational fluid dynamic CFD model

The heat and mass transfer and fluid flow phenomena in the planar micro-SOFC is described by the CFD model. Due to the low gas velocity and small size of the SOFC, the Reynolds number in the micro-channel is usually much lower than 100 (Yuan et al., 2003). Thus, the gas flow in an SOFC is typically laminar. From a heat transfer analysis, it is found that the local thermal equilibrium assumption is valid for the porous electrodes of an SOFC (Zheng et al., 2013). The governing equations for the CFD model include mass conservation, momentum conservation, energy conservation, and species conservation (Wang, 2004)  

Bg is the pemeability [m ] measuring the capability of the porous media for fluid permeation. The use of Darcy s law as source terms allows the momentum equations to be applicable to both the gas channels and the porous media, as an infinitely large permeability can be used for the gas channel. 

The source term (Sj, W m ) in the energy equationrepresents the heat generation/consumption by chemical reactions or electrochemical reactions. In the porous anode, the heat source term comes from heat generated by a WGSR and heat consumption by a DIR reaction. The heat generatedby the electrochemical reaction, taking into accoimtthe irreversible overpotential losses, is applied evenly to the electrolyte. Therefore, the source term ST can be written as  

A5h2 ASco are the entropy changes for the electrochemical reactions associated with H2 fuel and CO fuel. and refer to the total overpotentials for H2 fuel and CO fuel. Rdir and Rwgsr are the reaction rates (molm s ) for DIR and WGSR, while //dir and Hwgsr are the corresponding reaction heat (Jmol ). F is the Faraday constant (96485 Cmol ). L is the thickness of the electrolyte (m). 7h2 and Jqo are the current densities produced from electrochemical oxidation of H2 and CO, respectively. 

CH4 fuel only participates in the steam reforming reaction, while the direct electrochemical oxidation of CH4 is not considered. Thus, the source term for CH4 (Schj ) can be written as  

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In theory it should be possible to calculate the capture efficiency without measurements. Some attempts have used computational fluid dynamics (CFD) models, but difficulty modeling air movement and source characteristics have shown that it will be a long time before it will be possible to calculate the capture efficiency in advance. ... 

Not surprisingly, the Bernardi and Verbrugge model forms the basis for many other models that came after it. most notably the computational-fluid-dynamics (CFD) models, as discussed in the next section. In terms of direct descendants of this model, the model of Chan et al. " takes the Bernard and Verbrugge model and incorporates carbon monoxide effects at the anode as per the Springer et al. ° description. The models of Li and co-workers - " " ... 

The most commonly used computer fire models simulate the consequences of a fire in an enclosure. Zone models, as well as computational fluid dynamics (CFD) models, are used for this purpose. While they are in wide use, enclosure models have limited application in assessing hazards in the petrochemical industry. They are briefly described in this Appendix for general reference purposes. 

In practical combustion systems, such as CO boilers, the flue gas experiences spatial and temporal variations. Constituent concentration, streamline residence time, and temperature are critical to determining an efficient process design. Computational fluid dynamics (CFD) modeling and chemical kinetic modeling are used to achieve accurate design assessments and NO, reduction predictions based on these parameters. The critical parameters affecting SNCR and eSNCR design are listed in Table 17.4. 

As computers become faster, the complexity of problem that can be usefully simulated increases. Areas of interest include combining computational fluid dynamics (CFD) modelling with chemical kinetics to investigate (and hence reduce) the effect of flow maldistributions on aftertreatment system efficiency, and simulating catalyst deactivation over the lifetime of the catalyst. 

Some other studies were performed relating human exposure in urban areas based on ambient PM air concentrations determined with computational fluid dynamics (CFD) modelling applications. The three-dimensional CFD model MISKAM has been successfully implemented to provide better assessment of exposure to traffic-related air pollutants in urban areas [33]. 

Bridging the gap between micro- and macro-scale is the central theme of the first contribution. The authors show how a so-called Energy-Minimization Multi-Scale (EMMS) model allows to do this for circulating fluid beds. This variational type of Computational Fluid Dynamics (CFD) modeling allows for the resolution of meso-scale structures, that is, those accounting for the particle interactions, and enables almost grid-independent solution of the gas-solids two-phase flow. 

A comparison of the predicted results from a calibrated computational fluid dynamics (CFD) model with experimentally measured hydrogen data was made to verify the calibrated CFD model. The experimental data showed the method predicted the spatial and temporal hydrogen distribution in the garage very well. A comparison was then made of the risks incurred from a leaking hydrogen-fueled vehicle and a leaking liquefied petroleum gas (LPG)-fueled vehicle. 

Recently, computational fluid dynamics (CFD) models have been developed to guide the development of new BO designs [62-67]. Baker et al. developed a two-dimensional finite-difference model to solve the Navier-Stokes equation and to predict... 

Care is needed when modeling compressible gas flows, flows of vapor-liquid mixtures, slurry flows, and flows of non-Newtonian liquids. Some simulators use different pipe models for compressible flow. The prediction of pressure drop in multiphase flow is inexact at best and can be subject to very large errors if the extent of vaporization is unknown. In most of these cases, the simulation model should be replaced by a computational fluid dynamics (CFD) model of the important parts of the plant. 

In recent years, there has been considerable effort to develop computational fluid dynamic (CFD) models to predict the hydrodynamics and performance of fluidized beds. While this approach will no doubt yield valuable tools in the future, CFD models are not yet at the point where they can be used with confidence for design and scale-up of fluidized bed processes. 

A three-dimensional computational fluid dynamics (CFD) model was also created to model... 

Computational fluid dynamics (CFD) models of airflow in the nasal passages of rats, monkeys, and humans have been developed to determine the degree to which interspecies and interregional differences in uptake patterns along airway passages may account for differing distributions of formaldehyde-induced upper respiratory tract lesions in rats and primates. These models enable extrapolation of exposures associated with upper respiratory tract tissue damage in rats or monkeys to human exposures... 

Any notable accumulation of gas was unlikely since the two fans inside the chassis create a flow rate of approximately 180 CFM of air through the system. This corresponded to more than 95 complete air changes or turnovers every minute (Heck and Manning, 2000). The most likely zone of gas escape would be above the microreactor due to a membrane failure. If this occurs, the control system should have interlocked and shutoff the flow of combustible gas to that reaction channel. The flammable gas that does escape would have been immediately diluted by air flowing over the microreactor at an estimated rate of 120 ft min (Heck and Manning, 2000). To provide a more detailed analysis of gas mixing in the immediate vicinity of a microreactor die, a computational fluid dynamics (CFD) model was constructed to simulate the gas flow hydrodynamics. This simulation quantifies that there is a recirculation zone above the reactor with an airflow rate... 

Utilize computational fluid dynamics (CFD) models to rmderstand and address heat and mass transfer issues and reactor performance for steady-state and transient analysis. 

Papadakis and King (1988a,b) used this PSI-Cell model to simulate a spray dryer and compare their predicted results with limited experimental results associated with a lab-scale spray dryer. They have shown that the measured air temperatures at various levels below the roof of the spray drying chamber were well predicted by the computational fluid dynamics (CFD) model. Negiz et al. (1995) developed a program to simulate a cocurrent spray dryer based on the PSI-Cell model. Straatsma et al. (1999) developed a drying model, named NIZO-DrySim, to simulate aspects of... 

Hjertager, B. H. Solberg,T. (1999), A review of computational fluid dynamics (CFD) modeling of gas explosions . Prevention of Hazardous Fires and Explosions, 77-91, Kluwer Academic Publishers. 

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