Combined Two-phase Co-flow and Counter-flow in a Gas Channel/Porous Transport Layer Assembly

2020 ◽  
Vol 98 (9) ◽  
pp. 305-315
Author(s):  
Steven B. Beale ◽  
Martin Andersson ◽  
Norbert Weber ◽  
Holger Marschall ◽  
Werner Lehnert
Keyword(s):  
Transport Layer ◽  
Counter Flow ◽  
Two Phase ◽  
Gas Channel ◽  
Layer Assembly

Combined Two-phase Co-flow and Counter-flow in a Gas Channel/Porous Transport Layer Assembly

2020 ◽  
Vol MA2020-02 (34) ◽  
pp. 2213-2213
Author(s):  
Steven B. Beale ◽  
Martin Andersson ◽  
Norbert Weber ◽  
Holger Marschall ◽  
Werner Lehnert
Keyword(s):  
Transport Layer ◽  
Counter Flow ◽  
Two Phase ◽  
Gas Channel ◽  
Layer Assembly

Two-Phase Flow Characteristics in a Co-Flow Induced Microchannel With Microbubbles Generation

2007 ◽  
Author(s):  
Sujin Yeom ◽  
Seung S. Lee ◽  
Sang Yong Lee
Keyword(s):  
Two Phase Flow ◽  
Flow Characteristics ◽  
Flow Patterns ◽  
Gas Pressure ◽  
Superficial Velocity ◽  
Working Fluid ◽  
Phase Flow ◽  
Two Phase ◽  
Gas Channel ◽  
Micro Bubble

This paper presents a micro-fluidic device which generates micro-bubbles, ranging from 70μm to 160μm in diameter, and two-phase flow characteristics in the device were tested. The device is composed of three sub-channels: a centered gas channel (10μm×50μm) and two liquid channels (both with 85μm×50μm) on each side of the gas channel. Micro-bubbles are generated by co-flow of gas and liquid at the exit of the gas channel when the drag force becomes larger than the surface tension force as bubbles grow. Methanol and a gas mixture of CO2 and N2 were used as the working fluid. Since the flow rate of gas was very small, the gas momentum effect was considered negligible. Thus, in the present case, the controlling parameters were the liquid superficial velocity and the inlet pressure of the gas. A high speed camera was used to record two-phase flow patterns and micro-bubbles of the device. To confine the ranges of the micro-bubbles generation, two-phase flow patterns in the device is observed at first. Four different flow patterns were observed: annular, annular-slug, slug, and bubbly flow. In bubbly flows, uniform-sized micro-bubbles were generated, and the operating ranges of the liquid superficial velocity and the gas pressure were below 0.132 m/s and 0.7 bar, respectively. Diameters of the micro-bubbles appeared smaller with the higher superficial liquid velocity and/or with a lower gas pressure. Experimental results showed that, with the gas pressure lower than a certain level, the sizes of micro-bubbles were almost insensitive to the gas pressure. In such a ranges, the micro-bubble diameters could be estimated from a drag coefficient correlation, CDw = 31330/Re3, which is different from the correlations for macro-channels due to a larger wall effect with the micro-channels. In the latter part of the paper, as a potential of application of the micro-bubble generator to gas analysis, dissolution behavior of the gas components into the liquid flow was examined. The result shows that the micro-bubble generator can be adopted as a component of miniaturized gas analyzers if a proper improvement could be made in controlling the bubble sizes effectively.

(Invited) Two Phase Flow in Porous Transport Layer Structures in Polymer Electrolyte Water Electrolysis

2020 ◽  
Vol MA2020-01 (42) ◽  
pp. 1836-1836
Author(s):  
Salvatore De Angelis ◽  
Tobias Schuler ◽  
Thomas J. Schmidt ◽  
Felix N. Büchi
Keyword(s):  
Polymer Electrolyte ◽  
Two Phase Flow ◽  
Water Electrolysis ◽  
Transport Layer ◽  
Phase Flow ◽  
Two Phase ◽  
Layer Structures

Effect of Porosity and Thermal Conductivity of a Porous Transport Layer on Saturation and Thermal Transport in a Low-Temperature Fuel Cell

2013 ◽  
Author(s):  
Vinaykumar Konduru ◽  
Ezequiel Medici ◽  
Jeffrey S. Allen
Keyword(s):  
Thermal Conductivity ◽  
Fuel Cell ◽  
Solid Phase ◽  
Polymer Electrolyte Membrane ◽  
Operating Conditions ◽  
Transport Layer ◽  
Reliable Operation ◽  
Two Phase ◽  
Efficient Operation ◽  
Electrolyte Membrane

Water transport in the Porous Transport Layer (PTL) plays an important role in the efficient operation of polymer electrolyte membrane fuel cells (PEMFC). Excessive water content as well as dry operating conditions are unfavorable for efficient and reliable operation of the fuel cell. The effect of thermal conductivity and porosity on water management are investigated by simulating two-phase flow in the PTL of the fuel cell using a network model. In the model, the PTL consists of a pore-phase and a solid-phase. Different models of the PTLs are generated using independent Weibull distributions for the pore-phase and the solid-phase. The specific arrangement of the pores and solid elements is varied to obtain different PTL realizations for the same Weibull parameters. The properties of PTL are varied by changing the porosity and thermal conductivity. The parameters affecting operating conditions include the temperature, relative humidity in the flow channel and voltage and current density. A parametric study of different solid-phase distributions of the PTL and its effect on thermal, vapor and liquid transport in the PTL under different operating conditions are discussed.

Modeling the Effects of Gas Channel Flooding on the Voltage-Current Characteristics of PEM Fuel Cell

2010 ◽  
Author(s):  
K. H. Wong ◽  
K. H. Loo ◽  
Y. M. Lai ◽  
Siew-Chong Tan ◽  
Chi K. Tse
Keyword(s):  
Fuel Cell ◽  
Water Distribution ◽  
Pem Fuel Cell ◽  
Cell Performance ◽  
Water Flooding ◽  
Two Phase ◽  
Fuel Cell Performance ◽  
Gas Channel ◽  
Current Characteristics ◽  
Inlet Conditions

It has been reported recently that water flooding in the gas channel (GC) has significant effects on the voltage-current characteristics of a proton exchange membrane (PEM) fuel cell. However, the theoretical treatment of these effects on the fuel cell performance is still preliminary. A one-dimensional fuel cell model including the effects of two-phase flow in the GC is proposed to investigate the influences of inlet conditions on the water distribution in fuel cell and its performance by means of coupling the GC and membrane electrode assembly (MEA) modeling domains. The model predicts that the GC conditions, which are closely correlated to the inlet conditions, significantly affect the liquid water saturation level in the MEA. An increase in the inlet air pressure or humidification level leads to more severe water flooding, while an increase in the inlet air flow rate helps mitigating the water flooding. The simulated voltage-current characteristics under various inlet conditions are verified against experimental data and simulation results of a published computational fluids dynamics (CFD) model. They indicate that the relative humidity and stoichiometry of inlet air are crucial to the fuel cell performance, particularly at high current densities, due to their influences on the liquid water distribution in the fuel cell. The correlations between the inlet conditions and the fuel cell performance are addressed in the proposed model through a more accurate treatment of two-phase water transport in the cathodic MEA and GC. These are important for appropriate water management in fuel cells.

scholarly journals Influence of Stoichiometry on the Two-Phase Flow Behavior of Proton Exchange Membrane Electrolyzers

Energies ◽  
2019 ◽  
Vol 12 (3) ◽  
pp. 350 ◽  
Author(s):  
Olha Panchenko ◽  
Lennard Giesenberg ◽  
Elena Borgardt ◽  
Walter Zwaygardt ◽  
Nikolay Kardjilov ◽  
...  
Keyword(s):  
Mass Transport ◽  
Two Phase Flow ◽  
Current Collector ◽  
Optimal Operation ◽  
Transport Layer ◽  
Ex Situ ◽  
Water Volume ◽  
Membrane Electrode ◽  
Phase Flow ◽  
Two Phase

In order for electrolysis cells to operate optimally, mass transport must be improved. The key initial component for optimal operation is the current collector, which is also essential for mass transport. Water as an educt of the reaction must be evenly distributed by the current collector to the membrane electrode assembly. As products of the reaction, hydrogen and oxygen must also be directed quickly and efficiently through the current collector into the channel and removed from the cell. The second key component is the stoichiometry, which includes the current density and water volume flow rate and represents the ratio between the water supplied and water consumed. This study presents the correlation of the stoichiometry, two-phase flow in the channel and gas fraction in the porous transport layer for the first time. The gas-water ratio in the channel and porous transport layer during cell operation with various stoichiometries was investigated by means of a model in the form of an ex situ cell without electrochemical processes. Bubble formation in the channel was observed using a transparent cell. The gas-water exchange in the porous transport layer was then investigated using neutron radiography.

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