A Simple One-Dimensional Model of a Passive Hydrogen Recombiner

2014 ◽  
Author(s):  
Antoni Rożeń
Keyword(s):  
Gas Flow ◽  
Catalyst Surface ◽  
Transport Processes ◽  
Heat Radiation ◽  
Temperature Profiles ◽  
Gas Composition ◽  
Dimensional Model ◽  
One Dimensional ◽  
Hydrogen Recombination ◽  
Catalyst Temperature

A simple one-dimensional model allowing fast predictions of: a gas composition and temperature profiles, a catalyst temperature profile and an overall hydrogen recombination degree has been developed for a passive catalytic recombiner. The model assumes that heat and mass transport processes, taking place in vertical channels between catalyst plates, occur in a highly non-isothermal, developing laminar gas flow and in conditions of mixed convection. A kinetic model of heterogeneous catalysis was implemented into the model and the heat radiation from the catalyst surface was accounted for. The model with no adjustable parameters was verified against experimental results available in literature and results of numerical simulations obtained by CFD methods.

One-dimensional model on fuel penetration in diesel sprays with gas flow

2016 ◽  
Vol 17 (1) ◽  
pp. 109-118 ◽  
Author(s):  
M. Xu ◽  
Y. C. Sun ◽  
Y. Cui ◽  
K. Y. Deng ◽  
L. Shi
Keyword(s):  
Gas Flow ◽  
Dimensional Model ◽  
Diesel Sprays ◽  
One Dimensional

Integrated modelling of internal combustion engine intake and exhaust systems

2001 ◽  
Vol 215 (4) ◽  
pp. 495-506 ◽  
Author(s):  
O Chiavola
Keyword(s):  
Internal Combustion Engines ◽  
Gas Flow ◽  
Complex Geometry ◽  
Combustion Engine ◽  
Internal Combustion ◽  
Integrated Modelling ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
One Dimensional ◽  
Exhaust Systems

This paper presents a new method to analyse the unsteady gas flow in both intake and exhaust systems of internal combustion engines. Such a method is based on the simultaneous use of a one-dimensional model applied to describe the phenomena in ducts, together with a lumped parameter scheme to investigate the cylinder or other volume behaviour, coupled with a three-dimensional model, able to guarantee detailed information on flow behaviour in complex geometry, retaining the advantages of all methods, accuracy as well as fast processing and high flow pattern resolution. The description of the one-dimensional model developed with an example of its application is presented. The integrated approach with the coupling procedure is then described. Finally the results of a multicylinder exhaust system simulation are illustrated.

scholarly journals Comparison of a One-Dimensional Model of a High-Temperature Solid-Oxide Electrolysis Stack With CFD and Experimental Results

2005 ◽  
Author(s):  
J. E. O’Brien ◽  
C. M. Stoots ◽  
J. Stephen Herring ◽  
G. L. Hawkes
Keyword(s):  
High Temperature ◽  
Gas Flow ◽  
Operating Conditions ◽  
Operating Voltage ◽  
Dimensional Model ◽  
One Dimensional ◽  
Constant Flow Rate ◽  
High Temperature Steam ◽  
The One ◽  
Increasing Temperature

A one-dimensional model has been developed to predict the thermal and electrochemical behavior of a high-temperature steam electrolysis stack. This electrolyzer model allows for the determination of the average Nernst potential, cell operating voltage, gas outlet temperatures, and electrolyzer efficiency for any specified inlet gas flow rates, current density, cell active area, and external heat loss or gain. The model includes a temperature-dependent area-specific resistance (ASR) that accounts for the significant increase in electrolyte ionic conductivity that occurs with increasing temperature. Model predictions are shown to compare favorably with results obtained from a fully 3-D computational fluid dynamics model. The one-dimensional model was also employed to demonstrate the expected trends in electrolyzer performance over a range of operating conditions including isothermal, adiabatic, constant steam utilization, constant flow rate, and the effects of operating temperature.

A One-Dimensional Model for Cooling of Optical Fibers

2003 ◽  
Author(s):  
M. Usman Ghani ◽  
Ovidiu Marin ◽  
Martin Theriault
Keyword(s):  
Heat Transfer ◽  
Flow Regime ◽  
Forced Convection ◽  
Optical Fibers ◽  
Gas Flow ◽  
Gas Temperature ◽  
Dimensional Model ◽  
Operational Parameters ◽  
One Dimensional ◽  
Improved Design

This paper presents a one-dimensional model for the cooling of optical fibers. Heat transfer between the fiber, gas and wall, by conduction, convection, and radiation, are taken into account. The model offers advanced features such as multiple inlets and outlets. Six different pure gases or their mixtures may be used to study the effect of gas composition. The forced convection heat transfer coefficient is computed using the correlation for the forced convection in tubes and conduits. This correlation is then corrected to account for the enhanced heat transfer due to the motion of the fiber. This factor is determined from the limited experimental data available in the literature. The mathematical model consists of a system of ordinary differential equations and is solved using the LSODE solver. The model was used to study the effect of various operational parameters. The results show that at the typical conditions used in a commercial draw tower, Helium is the most effective cooling medium. A smaller diameter exchanger is more effective in cooling the fiber. More cooling is achieved if the incoming gas temperature is lower as well as if the cooler wall is kept at a lower temperature. The most critical factor is the fiber draw speed. At higher draw speeds, the residence time is low, which leads to shorter contact time for the fiber and gas to exchange heat. The effect of gas flow rate is not very significant, provided the flow regime is laminar. The turbulence flow regime is, in general, not desirable as it may cause vibrations, which is detrimental to fiber properties such as diameter and strength. Comparisons of the one-dimensional model results with the results of a two-dimensional model as well as simulations using Fluent, a commercial CFD package, are also presented. The results of these simulations may be used for an improved design of an exchanger, providing more efficient cooling of optical fiber. An improved design of exchanger will be the focus of future work in this area.

scholarly journals A Mechanistic Model of a Passive Autocatalytic Hydrogen Recombiner

2015 ◽  
Vol 36 (1) ◽  
pp. 3-19 ◽  
Author(s):  
Antoni Rożeń
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Gas Flow ◽  
Nuclear Reactor ◽  
Catalyst Surface ◽  
Mechanistic Model ◽  
Power Input ◽  
Heat Radiation ◽  
Recombination Reaction ◽  
Gas Temperature

Abstract : A passive autocatalytic hydrogen recombiner (PAR) is a self-starting device, without operator action or external power input, installed in nuclear power plants to remove hydrogen from the containment building of a nuclear reactor. A new mechanistic model of PAR has been presented and validated by experimental data and results of Computational Fluid Dynamics (CFD) simulations. The model allows to quickly and accurately predict gas temperature and composition, catalyst temperature and hydrogen recombination rate. It is assumed in the model that an exothermic recombination reaction of hydrogen and oxygen proceeds at the catalyst surface only, while processes of heat and mass transport occur by assisted natural and forced convection in non-isothermal and laminar gas flow conditions in vertical channels between catalyst plates. The model accounts for heat radiation from a hot catalyst surface and has no adjustable parameters. It can be combined with an equation of chimney draft and become a useful engineering tool for selection and optimisation of catalytic recombiner geometry.

scholarly journals Impacts of the January 2005 solar particle event on noctilucent clouds and water at the polar summer mesopause

2012 ◽  
Vol 12 (12) ◽  
pp. 5633-5646 ◽  
Author(s):  
H. Winkler ◽  
C. von Savigny ◽  
J. P. Burrows ◽  
J. M. Wissing ◽  
M. J. Schwartz ◽  
...  
Keyword(s):  
Transport Processes ◽  
Occurrence Rate ◽  
Noctilucent Clouds ◽  
Dimensional Model ◽  
Model Calculations ◽  
One Dimensional ◽  
Particle Event ◽  
Solar Particle ◽  
Solar Particle Event ◽  
Satellite Instruments

Abstract. The response of noctilucent clouds to the solar particle event in January 2005 is investigated by means of icy particle and ion chemistry simulations. It is shown that the decreasing occurrence rate of noctilucent clouds derived from measurements of the SCIAMACHY/Envisat instrument can be reproduced by one-dimensional model simulations if temperature data from the MLS/Aura instrument are used. The model calculations indicate that the sublimation of noctilucent clouds leads to significant changes of the water distribution in the mesopause region. These model results are compared with H2O measurements from the MLS and the MIPAS/Envisat satellite instruments. The pronounced modelled water enhancement below the icy particle layer and its decrease during the SPE are not observed by the satellite instruments. At altitudes >85 km the satellite measurements show an increase of H2O during the SPE in qualitative agreement with the model predictions. The discrepancies between model H2O and observations at lower altitudes might be attributed to the one-dimensional model approach which in particular neglects inhomogeneities and horizontal transport processes. Additionally, it is revealed that the water depletion due to reactions of proton hydrates during the considered solar particle event has only a minor impact on the icy particles.

Spectral Emission Measurements From Planar Mixtures of Gas and Particulates

1987 ◽  
Vol 109 (1) ◽  
pp. 151-158 ◽  
Author(s):  
R. D. Skocypec ◽  
D. V. Walters ◽  
R. O. Buckius
Keyword(s):  
Carbon Dioxide ◽  
Test Section ◽  
Gas Flow ◽  
Experimental System ◽  
Solid Particles ◽  
Spectral Energy ◽  
Gas Composition ◽  
Particle Loading ◽  
Spectral Emission ◽  
One Dimensional

An experimental system is developed that forms a hot layer of gas and particulates flowing through a test section with cooled walls. The test section forms a one-dimensional planar layer, allows intrusive probes to characterize the medium in terms of particle loading and temperature, and allows radiometric measurements of the normally directed spectral energy emitted from the medium. Gas flow, gas composition, and particle flow are controlled. An experimental investigation is undertaken yielding spectral normally directed emittance data obtained from a well-characterized layer containing gaseous constituents of carbon dioxide and nitrogen, and solid particles of BNi-2, a boron nickel alloy. Emittance data are presented and exhibit the effects of particulate scattering, including the extension of the 4.3 μm carbon dioxide band wings. Emittance data are compared to analytical predictions.

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