Deformation of a Droplet in a Channel Flow

2008 ◽  
Vol 5 (4) ◽  
Author(s):  
Ebrahim Shirani ◽  
Shila Masoomi
Keyword(s):  
Surface Tension ◽  
Channel Flow ◽  
Polymer Electrolyte Membrane ◽  
Droplet Deformation ◽  
Navier Stokes Equation ◽  
Droplet Shape ◽  
Viscous Forces ◽  
Electrolyte Membrane ◽  
Wide Range ◽  
Surrounding Fluid

Formation of droplets especially in microchannels, micro-electro-mechanical systems (MEMS) and polymer electrolyte membrane fuel cells and their effects on the performance of these devises, as well as scientific aspect of the droplet behavior in the fluid flow motion, makes the subject of the droplet deformation and motion an attractive problem. In this work, we numerically simulate the deformation of a drop of water attached to the wall of a channel flow using full two-dimensional Navier–Stokes equation and the volume-of-fluid method for capturing the interface. The effects of channel inlet velocity, the density and viscosity of the surrounding fluid, and the surface tension coefficient on the flow structures both inside and outside of the droplet as well as the deformation of the droplets are examined. Several test cases, which cover rather wide range of the Reynolds and capillary numbers, based on the surrounding fluid properties and the diameter of the droplet are performed. The Reynolds number, Re, range is from 24 to 1800 and the capillary number, Ca, is from 0.014 to 0.219. It is found that the droplet shape changes and depending on the capillary and Reynolds numbers, it eventually reaches an equilibrium state when there is balance between the surface tension, inertia, and the viscous forces. It is also found that the deformation of the droplet does not depend on the capillary numbers, when Ca is small, but it is a strong function of Ca, when it is large.

Current Distribution in a Polymer Electrolyte Membrane Fuel Cell Under Flooding Conditions

2009 ◽  
Author(s):  
A. Jamekhorshid ◽  
G. Karimi ◽  
X. Li
Keyword(s):  
Fuel Cell ◽  
Polymer Electrolyte ◽  
Current Distribution ◽  
Current Density ◽  
Polymer Electrolyte Membrane ◽  
Operating Conditions ◽  
Average Current Density ◽  
Electrolyte Membrane ◽  
Wide Range ◽  
Average Current

Non-uniform current distribution in polymer electrolyte membrane fuel cells results in local over-heating, accelerated ageing, and lower power output than expected. This issue is very critical when fuel cell experiences water flooding. In this work, the performance of a PEM fuel cell is investigated under cathode flooding conditions. A partially flooded GDL model is proposed to study local current density distributions along flow fields over a wide range of cell operating conditions. The model results show as cathode inlet humidity and/or cell pressure increase the average current density for the unflooded portions of the cell increases but the system becomes more sensitive to flooding. Operating the cell at higher temperatures would lead to higher average current densities and the chance of system being flooded is reduced. In addition, higher cathode stoichiometries prevent system flooding but the average current density remains almost constant.

On the Law of Spontaneous Spreading of Liquid Droplets on Solid Substrates

2002 ◽  
Author(s):  
Abdullatif M. Alteraifi ◽  
Dalia Sherif ◽  
Abdelsamie Moet
Keyword(s):  
Surface Tension ◽  
Spherical Shape ◽  
Soda Lime ◽  
Solid Substrate ◽  
Contact Radius ◽  
Soda Lime Glass ◽  
Image Analysis System ◽  
Liquid Droplets ◽  
Viscous Forces ◽  
Wide Range

Several theories deal with the spreading kinetics of liquids on solid substrate, notable amongst which is de Gennes’ law, which relates the contact radius, R, to the droplet volume, V, the surface tension, σ, and the viscosity, µ, by the equation R3m+1 = (σ/µ) t Vm and ascertains that m = 3 is “indeed expected theoretically for all cases of dry spreading”. Validity of the proposed models is examined by measurements of the spreading of a number of liquids exhibiting a wide range of surface tension and viscosity on dry soda-lime glass. The measurements used a small droplet of constant volume to minimize gravitational effects. The droplet was released near the glass surface from automatic micro syring, supported on micromanipulator. The contact radius was acquired as a function of time by an image analysis system. Analyzed in terms of de Gennes law, it was noted that the m values for silicone oils fall within the suggested variance i.e., m = 3.0±0.5. However, significant disagreements were noted in the case of other liquids, where m ranged from 5.2 to 15.0 with no correlation with the parameters included. Mechanistic considerations suggest that whereas the surface tension acts to retain the spherical shape of the droplet, interfacial tension acts to maximize the contact area whereas the viscous forces determine the kinetics. The magnitude of the difference between the interfacial and surface energies likely determines whether spreading is complete or incomplete.

Tolerance to carbon corrosion of various carbon structures as catalyst supports for polymer electrolyte membrane fuel cells

2019 ◽  
Vol 7 (43) ◽  
pp. 25056-25065 ◽  
Author(s):  
Sung Won Lee ◽  
Sung Ryul Choi ◽  
Jeongyun Jang ◽  
Gu-Gon Park ◽  
Seung Ho Yu ◽  
...  
Keyword(s):  
High Performance ◽  
Polymer Electrolyte Membrane ◽  
Mitigation Strategy ◽  
Catalyst Supports ◽  
Carbon Supports ◽  
Carbon Corrosion ◽  
Electrolyte Membrane ◽  
Spherical Carbon ◽  
Carbon Structures ◽  
Wide Range

We introduce a material-based mitigation strategy to improve the toughness of the carbon supports of high performance PEMFC through the hybridization of active spherical carbon and mechanochemically durable PCNF featuring a wide range of fiber stems.

scholarly journals Mass Spectrometry of Polymer Electrolyte Membrane Fuel Cells

2016 ◽  
Vol 2016 ◽  
pp. 1-9 ◽  
Author(s):  
Viktor Johánek ◽  
Anna Ostroverkh ◽  
Roman Fiala ◽  
Andrii Rednyk ◽  
Vladimír Matolín
Keyword(s):  
Mass Spectrometry ◽  
Fuel Cells ◽  
Fuel Cell ◽  
Polymer Electrolyte ◽  
Polymer Electrolyte Membrane ◽  
Operating Conditions ◽  
Cell Potential ◽  
Electrolyte Membrane ◽  
Power Load ◽  
Wide Range

The chemical analysis of processes inside fuel cells under operating conditions in either direct or inverted (electrolysis) mode and their correlation with potentiostatic measurements is a crucial part of understanding fuel cell electrochemistry. We present a relatively simple yet powerful experimental setup for online monitoring of the fuel cell exhaust (of either cathode or anode side) downstream by mass spectrometry. The influence of a variety of parameters (composition of the catalyst, fuel type or its concentration, cell temperature, level of humidification, mass flow rate, power load, cell potential, etc.) on the fuel cell operation can be easily investigated separately or in a combined fashion. We demonstrate the application of this technique on a few examples of low-temperature (70°C herein) polymer electrolyte membrane fuel cells (both alcohol- and hydrogen-fed) subjected to a wide range of conditions.

scholarly journals Powering the Future through Hydrogen and Polymer Electrolyte Membrane Fuel Cells

2020 ◽  
Author(s):  
Bo Ki Hong ◽  
Sae Hoon Kim ◽  
Chi Myung Kim
Keyword(s):  
Fuel Cells ◽  
Fuel Cell ◽  
Polymer Electrolyte ◽  
Polymer Electrolyte Membrane ◽  
Heavy Duty ◽  
Electrolyte Membrane ◽  
Passenger Vehicles ◽  
Wide Range ◽  
The Future ◽  
Heavy Duty Vehicles

To date, the world has been making a massive shift away from fossil fuels towards cleaner energy sources. For the past decade, polymer electrolyte membrane fuel cells (PEMFCs) powered by hydrogen have attracted much attention as a promising candidate for eco-friendly vehicles, i.e. fuel cell electric vehicles (FCEVs), owing to their high power density, high efficiency and zero emission features. Since the world’s first mass production of Tucson ix35 FCEV by Hyundai in 2013, global automotive original equipment manufacturers (OEMs) have focused on commercialising FCEVs. In 2018, Hyundai also unveiled the second generation of the mass-produced FCEV (i.e. Nexo) with improved performances and durability compared with its predecessor. Since then, the global market for PEMFCs for a variety of FCEV applications has been growing very rapidly in terms of both passenger vehicles and medium- and heavy-duty vehicles such as buses and trucks, which require much higher durability than passenger vehicles, i.e. 5000 h for passenger vehicles vs. 25,000 h for heavy-duty vehicles. In addition, PEMFCs are also in demand for other applications including fuel cell electric trains, trams, forklifts, power generators and vessels. We herein present recent advances in how hydrogen and PEMFCs will power the future in a wide range of applications and address key challenges to be resolved in the future.

scholarly journals Preparation and performance study of a PVDF–LATP ceramic composite polymer electrolyte membrane for solid-state batteries

RSC Advances ◽  
2018 ◽  
Vol 8 (71) ◽  
pp. 40498-40504 ◽  
Author(s):  
Xinghua Liang ◽  
Di Han ◽  
Yunting Wang ◽  
Lingxiao Lan ◽  
Jie Mao
Keyword(s):  
Ceramic Composite ◽  
Organic Liquid ◽  
Polymer Electrolyte Membrane ◽  
Composite Polymer Electrolyte ◽  
Performance Study ◽  
Safety Issues ◽  
Electrolyte Membrane ◽  
Wide Range ◽  
Solid State Batteries ◽  
And Performance

Recently, safety issues in conventional organic liquid electrolytes and the interface resistance between the electrode and electrolyte have been the most challenging barriers for the expansion of lithium batteries to a wide range of applications.

Effect of gas composition on Ru dissolution and crossover in polymer-electrolyte membrane fuel cells

2010 ◽  
Vol 195 (15) ◽  
pp. 4622-4627 ◽  
Author(s):  
Tommy T.H. Cheng ◽  
Nengyou Jia ◽  
Vesna Colbow ◽  
Silvia Wessel ◽  
Monica Dutta
Keyword(s):  
Fuel Cells ◽  
Polymer Electrolyte ◽  
Polymer Electrolyte Membrane ◽  
Gas Composition ◽  
Electrolyte Membrane
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