Gas flow with low gas pressure in porous media: quasi-statics and acoustics

An aluminium alloy was sintered using a conventional press and sinter process, at various gas pressures, to observe the effect of sintering gas pressure on the densification rate. Compacts of aluminium alloy 2712 (Al-3.8Cu-1Mg-0.7Si-0.1Sn) were prepared from elemental powders and sintered in a horizontal tube furnace under nitrogen or argon at 590°C for up to 60 minutes, and air cooled. The gas flow was adjusted to achieve specific gas pressures in the furnace. It has been found that increasing the nitrogen pressure at the start of the isothermal holding stage to 160kPa increased the densification rate compared to standard atmospheric pressure sintering. Increasing the nitrogen pressure further, up to 600kPa, had no additional benefit. The densification rate was increased significantly by increasing the gas pressure to 600kPa during both heating and isothermal holding. Under argon the elevated pressure did not increase the densification rate. Results seem to suggest that the beneficial effect of the elevated pressure on the rate of densification is related to nitride formation.

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Modeling and Calculation of Initial Ignition Gas Pressure Flow through the Rigid Porous Media in 100 mm Ignition Simulator

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.560-561.1103 ◽

2012 ◽

Vol 560-561 ◽

pp. 1103-1113

Author(s):

Zheng Gang Xiao ◽

Wei Dong He ◽

San Jiu Ying ◽

Fu Ming Xu

Keyword(s):

Porous Media ◽

Gas Flow ◽

Ceramic Composite ◽

Peak Position ◽

Chamber Pressure ◽

Lateral Side ◽

Physical Processes ◽

Local Permeability ◽

Pressure Peak ◽

Flow Through

To acquire better understanding of the early ignition phenomena in 100mm ignition simulator loaded with packed propellant bed, a theoretical model of ignition gas flow through rigid porous media is developed. Three pressure gauges are installed in the lateral side of ignition simulator for chamber pressure measurements after ignition. The pseupropellant loaded in the chamber is similar to the standard 13/19 single-base cylindrical propellant in size. It is composed of rigid ceramic composite with low thermo conductivity. It is assumed that the pseupropellant bed is rigid in contrast to the previous elastic porous media assumption. The calculated pressure values can be verified by the experimental data well at the low loading density of pseupropellant bed of 0.18 g/cm3. However, there is still error between the experimental and calculated results in the early pressure peak position close to the ignition primer when the loading density of pseupropellant bed increases to 0.73 and 1.06g/cm3, due to the change of local permeability of pseupropellant bed at high loading density, which is assumed a constant in the model for the modeling easily. The calculations can enable better understanding of physical processes of ignition gas flow in the ignition simulator loaded with the pseupropellant bed.

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A method for measuring the local gas pressure within a gas-flow stage in situ in the transmission electron microscope

Ultramicroscopy ◽

10.1016/j.ultramic.2015.01.002 ◽

2015 ◽

Vol 153 ◽

pp. 55-60 ◽

Cited By ~ 5

Author(s):

R. Colby ◽

D.H. Alsem ◽

A. Liyu ◽

B. Kabius

Keyword(s):

Electron Microscope ◽

Transmission Electron Microscope ◽

Gas Flow ◽

Gas Pressure ◽

Transmission Electron ◽

Flow Stage

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Understanding Carbon Dioxide Transfer in Direct Methanol Fuel Cells Using a Pore-Scale Model

Journal of Electrochemical Energy Conversion and Storage ◽

10.1115/1.4050369 ◽

2021 ◽

Vol 19 (1) ◽

Author(s):

Nathaniel Metzger ◽

Archana Sekar ◽

Jun Li ◽

Xianglin Li

Keyword(s):

Carbon Dioxide ◽

Pressure Drop ◽

Gas Flow ◽

Direct Methanol Fuel Cells ◽

Gas Pressure ◽

Mass Transfer Resistance ◽

Transfer Resistance ◽

Cell Components ◽

Direct Methanol ◽

Methanol Fuel Cells

Abstract The gas flow of carbon dioxide from the catalyst layer (CL) through the microporous layer (MPL) and gas diffusion layer (GDL) has great impacts on the water and fuel management in direct methanol fuel cells (DMFCs). This work has developed a liquid–vapor two-phase model considering the counter flow of carbon dioxide gas, methanol, and water liquid solution in porous electrodes of DMFC. The model simulation includes the capillary pressure as well as the pressure drop due to flow resistance through the fuel cell components. The pressure drop of carbon dioxide flow is found to be about two to three orders of magnitude higher than the pressure drop of the liquid flow. The big difference between liquid and gas pressure drops can be explained by two reasons: volume flowrate of gas is three orders of magnitude higher than that of liquid; only a small fraction of pores (<5%) in hydrophilic fuel cell components are available for gas flow. Model results indicate that the gas pressure and the mass transfer resistance of liquid and gas are more sensitive to the pore size distribution than the thickness of porous components. To buildup high gas pressure and high mass transfer resistance of liquid, the MPL and CL should avoid micro-cracks during manufacture. Distributions of pore size and wettability of the GDL and MPL have been designed to reduce the methanol crossover and improve fuel efficiency. The model results provide design guidance to obtain superior DMFC performance using highly concentrated methanol solutions or even pure methanol.

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