Numerical Investigation of Radiation Effects in Catalytic Combustion

2007 ◽  
Author(s):  
Sandip Mazumder ◽  
Michael Grimm
Keyword(s):  
Carbon Monoxide ◽  
Thermal Radiation ◽  
Catalytic Combustion ◽  
Radiation Effects ◽  
Single Channel ◽  
Radiation Transport ◽  
Catalytic Converter ◽  
Discrete Ordinates ◽  
Flammability Limits ◽  
Carbon Monoxide Combustion

In modeling catalytic combustion in a monolithic catalytic converter, it is generally assumed that the gas within the individual monolith channels does not interfere with thermal radiation. To date, no quantitative study has been undertaken to validate this assumption. Past studies for carbon monoxide combustion also appear to indicate that the emissivity of the washcoat has little effect on the thermal radiation field. In order to investigate these two issues, methane-air combustion on platinum is modeled inside a single channel of a monolith using a detailed surface reaction mechanism comprised of 24 reactions between 19 species. Radiation transport is modeled using the Discrete Ordinates Method and a gray formulation. Planck-mean absorption coefficients of the gases, calculated from the HITEMP and HITRAN databases, are used to investigate participating medium effects. All calculations were performed using the commercial CFD code, CFD-ACE+™, supplemented by user-subroutines for calculating the absorption coefficient of the gas mixture. Results show that the conversion percentages and temperature distributions are unaltered by the inclusion of participating medium radiation effects, verifying the commonly held belief, stated earlier. However, in strong contrast with carbon monoxide combustion, the emissivity of the washcoat was found to significantly affect flammability limits in the case of methane combustion—the flame being hotter and more stable for smaller values of emissivity.

Numerical Investigation of Radiation Effects in Monolithic Catalytic Combustion Reactors

2011 ◽  
Vol 9 (1) ◽  
Author(s):  
Sandip Mazumder ◽  
Michael Grimm
Keyword(s):  
Carbon Monoxide ◽  
Thermal Radiation ◽  
Catalytic Combustion ◽  
Radiation Effects ◽  
Single Channel ◽  
Radiation Transport ◽  
Catalytic Converter ◽  
Radiative Properties ◽  
Discrete Ordinates ◽  
Carbon Monoxide Combustion

In modeling catalytic combustion in a monolithic catalytic converter, it is generally assumed that the gas within the individual monolith channels does not interfere with thermal radiation. To date, no quantitative study has been undertaken to validate this assumption. Past studies for carbon monoxide combustion also appear to indicate that the emissivity of the washcoat has little effect on the thermal radiation field. In order to investigate these two issues, methane-air combustion on platinum is modeled inside a single channel of a monolith using a detailed surface reaction mechanism comprised of 24 reactions between 19 species. Radiation transport is modeled using the Discrete Ordinates Method and a gray formulation. Planck-mean absorption coefficients of the gases, calculated from the HITEMP and HITRAN databases, are used to investigate participating medium effects. All calculations were performed using the commercial CFD code, CFD-ACE+™, supplemented by user-subroutines for calculating the radiative properties of the gas mixture. Results show that the conversion percentages and temperature distributions are unaltered by the inclusion of participating medium radiation effects, verifying the commonly held belief, stated earlier. However, in strong contrast with carbon monoxide combustion, the emissivity of the washcoat was found to significantly affect flammability limits in the case of methane combustion—the flame being hotter and more stable for smaller values of emissivity.

Radiation Heat Transfer Analysis of the Monolith-Type Solid Oxide Fuel Cell

2003 ◽  
Author(s):  
Sunil Murthy ◽  
Andrei Fedorov
Keyword(s):  
Heat Transfer ◽  
Thermal Radiation ◽  
Radiation Effects ◽  
Radiation Transport ◽  
Radiation Heat Transfer ◽  
Heat Transfer Analysis ◽  
Radiation Heat ◽  
Modeling Framework ◽  
Flux Approximation ◽  
Ysz Electrolyte

In this study, a modeling framework for heat and mass transport is investigated for a unit cell of the monolith type SOFC, with emphasis on quantifying the radiation heat transfer effects. The Schuster-Schwartzchild two-flux approximation is used for treating thermal radiation transport in the optically thin YSZ electrolyte, and the Rosseland radiative thermal conductivity is used to account for radiation effects in the optically thick Ni-YSZ and LSM electrodes. The thermal radiation heat transfer is coupled to the overall energy conservation equations through the divergence of the local radiative flux. A commercially available CFD software was used as a platform for the global thermal-fluid modeling of the SOFC and the radiation models were implemented through the user-defined functions. Results from sample calculations show significant changes in the operating temperatures and parameters of the SOFC with the inclusion of radiation effects.

scholarly journals The M-1 Radiation Model: Evaluation for Predicting Thermal Radiation From Fires

2012 ◽  
Author(s):  
Alexander L. Brown ◽  
Flint Pierce
Keyword(s):  
Thermal Radiation ◽  
Transport Model ◽  
Hyperbolic Equations ◽  
Radiation Transport ◽  
Diffuse Radiation ◽  
Radiative Energy ◽  
Discrete Ordinates ◽  
Radiation Model ◽  
Radiation Transport Model ◽  
The Cost

The M-1 radiation model is a thermal radiation transport model that is derived from a maximum entropy approximation to the radiative transport equation. It involves the solution of four hyperbolic equations for conservation of radiative energy. The M-1 model has similarities to the classical diffusion approximations (like P-1), but is able to better predict directed flux. Consequently, shadowing and long-range transport can be well resolved for a fraction of the cost of methods with exponentially increasing accuracy costs like the method of discrete ordinates and Monte Carlo ray-tracing. The M-1 method is mostly used historically in astronomical radiation transport, but has recently been shown to work for combustion applications of smaller scale. Past work has shown it to give good comparisons to fire problems with length scales of interest. Because of the potential for the model to predict radiation transport more cost-effectively, it is being examined for implementation as an option in our fire codes. We present the theory behind the model. The Eddington factor is used to partition directed and diffuse radiation. It is normally modeled since it is derived from a transcendental functional relationship. We analyze Eddington factor models presented in previous work, and present a new model that we show to be superior in most ways to all the previously presented models. Some 1-dimensional calculations are also shown that illustrate the potential accuracy and challenges with implementing the M-1 model. Such challenges include the specification of boundary conditions and the development of robust solver methods.

An Investigation on the Performance of an Oxidation Catalyst Using Two-dimensional Simulation with Detailed Reaction Mechanism

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Sreeharsh Nair ◽  
Mayank Mittal
Keyword(s):  
Single Channel ◽  
Catalytic Converter ◽  
Oxidation Catalyst ◽  
Low Temperature Combustion ◽  
Wide Range ◽  
Detailed Reaction Mechanism ◽  
Temperature Combustion ◽  
High Concentrations ◽  
Dimensional Simulation ◽  
Surface Reaction Kinetics

AbstractThe advent of stricter emission standards has increased the importance of aftertreatment devices and the role of numerical simulations in the evolution of better catalytic converters in order to satisfy these emission regulations. In this paper, a 2-D numerical simulation of a single channel of the monolith catalytic converter is presented by using detailed surface reaction kinetics aiming to investigate the chemical behaviour inside the converter. The model has been developed to study the conversion of carbon monoxide (CO) in the presence of propene (C3H6) for low-temperature combustion (LTC) engine application. The inhibition effect of C3H6 over a wide range of CO inlet concentrations is investigated. Considering both low and high levels of CO concentration at the inlet, the 2-D model predicted better results than their corresponding 1-D counterparts when compared with the experimental data from literature. It was also observed that C3H6 inhibition at high temperatures was significant, particularly for high concentrations of CO compared to low concentrations of CO at the inlet.

Chemical reaction and thermal radiation effects on magnetohydrodynamics flow of Casson–Williamson nanofluid over a porous stretching surface

2021 ◽  
pp. 095440892110253
Author(s):  
Pooja P Humane ◽  
Vishwambhar S Patil ◽  
Amar B Patil
Keyword(s):  
Differential Equation ◽  
Thermal Radiation ◽  
Chemical Reaction ◽  
Radiation Effects ◽  
Physical Mechanism ◽  
Reaction Parameter ◽  
Stretching Surface ◽  
Injection Parameter ◽  
Chemical Reaction Parameter ◽  
Porous Stretching Surface

The flow of Casson–Williamson fluid on a stretching surface is considered for the study. The movement of fluid is examined under the effect of external magnetic field, thermal radiation and chemical consequences. The model is formed by considering all the physical aspects responsible for the physical mechanism. The formed mathematical model (partial differential equation) is numerically solved after transforming it into an ordinary one (ordinary differential equation) via similarity invariants. The physical mechanism for velocity, temperature, and concentration is examined through the associated parameters like radiation index, Williamson and Casson parameter, suction/injection parameter, porosity index, and chemical reaction parameter.

scholarly journals Effects of radiative heat transfer on the structure of turbulent supersonic channel flow

2011 ◽  
Vol 677 ◽  
pp. 417-444 ◽  
Author(s):  
S. GHOSH ◽  
R. FRIEDRICH ◽  
M. PFITZNER ◽  
CHR. STEMMER ◽  
B. CUENOT ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Radiation ◽  
Radiative Heat Transfer ◽  
Radiation Effects ◽  
Radiative Heat ◽  
Pure Water ◽  
Molecular Transport ◽  
Working Fluid ◽  
Mean Flow ◽  
Total Energy Balance

The interaction between turbulence in a minimal supersonic channel and radiative heat transfer is studied using large-eddy simulation. The working fluid is pure water vapour with temperature-dependent specific heats and molecular transport coefficients. Its line spectra properties are represented with a statistical narrow-band correlated-k model. A grey gas model is also tested. The parallel no-slip channel walls are treated as black surfaces concerning thermal radiation and are kept at a constant temperature of 1000 K. Simulations have been performed for different optical thicknesses (based on the Planck mean absorption coefficient) and different Mach numbers. Results for the mean flow variables, Reynolds stresses and certain terms of their transport equations indicate that thermal radiation effects counteract compressibility (Mach number) effects. An analysis of the total energy balance reveals the importance of radiative heat transfer, compared to the turbulent and mean molecular heat transport.

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