Visualization and Predictive Modeling of Two-Phase Flow Regime Transition With Application Towards Water Management in the Gas-Flow Channels of PEM Fuel Cells

2005 ◽  
Author(s):  
Sang Young Son ◽  
Jeffrey S. Allen
Keyword(s):  
Fuel Cell ◽  
Flow Regime ◽  
Gas Flow ◽  
Two Phase Flow ◽  
Phase Distribution ◽  
Pem Fuel Cells ◽  
Bond Number ◽  
Phase Flow ◽  
Two Phase ◽  
Flow Channels

Understanding the behavior of gas and water vapor flow through the microchannel gas flow passages of a proton-exchange membrane (PEM) fuel cells is critical to reliable fuel cell operation. Recent research efforts have illustrated the importance of capillarity on the behavior of two-phase flow (gas-liquid) in low Bond number systems; that is, systems where capillary forces are important relative to gravitational forces. Such systems include capillary tubes and microchannels as well as the gas flow channels of a PEM fuel cell. The key characteristic scaling factors for two-phase flow in capillaries have been determined. The choice of length scales and velocity scales in dimensionless groups used to characterize two-phase flow is critical to correctly delineating phase distribution. Traditional scaling for these types of flows have considered the interaction between gas and liquid phases to be primarily inertial in nature. The role of liquid film stability where the phase interaction is a combination of viscous and capillary effects is shown to be a more appropriate scaling for low-Bond number, low-Suratman number two-phase flows. Microscopic visualization at high frame rates has been used to identify the flow regime under various gas-liquid mass ratios, channel geometries and surface energies. The observations collected via high speed microscopy and corresponding pressure measurements are reported for square and circular cross-sectional microchannels with contact angles of 20 degrees (hydrophilic) and 70 degrees (hydrophobic). The effect of geometry and contact angle on the phase distribution and the pressure drop are dramatic.

Flow Regime Evolution in Long, Serpentine Microchannels With a Porous Carbon Paper Wall

2008 ◽  
Author(s):  
Julie E. Steinbrenner ◽  
Eon Soo Lee ◽  
Fu-Min Wang ◽  
Chen Fang ◽  
Carlos H. Hidrovo ◽  
...  
Keyword(s):  
Fuel Cell ◽  
Flow Regime ◽  
Liquid Flow ◽  
Liquid Water ◽  
Two Phase Flow ◽  
Pem Fuel Cells ◽  
Carbon Paper ◽  
Phase Flow ◽  
Two Phase ◽  
Flow Rates

An important function of the gas delivery channels in Proton Exchange Membrane (PEM) fuel cells is the evacuation of liquid water created at the cathode. The resulting two-phase flow can become an obstacle to reactant transport and a source of parasitic losses. The present work examines the behavior of two-phase flow in 500 μm × 500 μm × 60 cm channels with distributed water injection through a porous carbon paper wall to gain understanding of the physics of flows relevant to fuel cell water management challenges. Flow regime maps based on local gas and liquid flow rates are constructed for experimental conditions corresponding to current densities between 0.5 and 1 A/cm2 and stoichiometric coefficients from 1 to 4. Flow structures are analyzed along the entire length of the channel. It is observed that slug flow is favored to plug flow at high air flow rates and low liquid flow rates. Stratified flow dominates at high liquid flow rates. Along the axial flow direction, the flow regime consistently transitions from intermittent to wavy to stable stratified flow. This progression is quantified using a parameter of flow progression which characterizes the degree of development of the two-phase flow toward the stable stratified condition. This parameter is discussed in relation to fuel cell operating conditions. It provides a metric for analyzing liquid water removal mechanisms in the cathode channels of PEM fuel cells.

Low Bond Number Two-Phase Flow Regime Transition from Slug to Annular Wavy Flow in a Microchannel

2003 ◽  
Vol 125 (4) ◽  
pp. 544-544 ◽  
Author(s):  
Sang Young Son ◽  
Jeffrey S. Allen ◽  
Kenneth O. Kihm
Keyword(s):  
Flow Regime ◽  
Two Phase Flow ◽  
Bond Number ◽  
Phase Flow ◽  
Regime Transition ◽  
Two Phase ◽  
Flow Regime Transition

Impedance-Based Void Fraction Measurement and Flow Regime Identification in Microchannel Flows

2011 ◽  
Author(s):  
Sidharth Paranjape ◽  
Susan N. Ritchey ◽  
Suresh V. Garimella
Keyword(s):  
Flow Regime ◽  
Void Fraction ◽  
High Speed ◽  
Electrical Impedance ◽  
Two Phase Flow ◽  
Phase Distribution ◽  
Electrical Conductance ◽  
Statistical Characteristics ◽  
Phase Flow ◽  
Two Phase

Electrical impedance of a two-phase mixture is a function of void fraction and phase distribution. The difference in the electrical conductance and permittivity of the two phases can be exploited to measure electrical impedance for obtaining void fraction and flow regime characteristics. An electrical impedance meter is constructed for the measurement of void fraction in microchannel two-phase flow. The experiments are conducted in air-water two-phase flow under adiabatic conditions. A transparent acrylic test section of hydraulic diameter 780 micrometer is used in the experimental investigation. The impedance void meter is calibrated against the void fraction measured using analysis of images obtained with a high-speed camera. Based on these measurements, a methodology utilizing the statistical characteristics of the void fraction signals is employed for identification of microchannel flow regimes.

Two-Phase Flow Pressure Drop Measurement in PEM Fuel Cell Flow Channels

2014 ◽  
Author(s):  
Mehdi Mortazavi ◽  
Kazuya Tajiri
Keyword(s):  
Fuel Cell ◽  
Pressure Drop ◽  
Two Phase Flow ◽  
Pem Fuel Cell ◽  
Phase Flow ◽  
Two Phase ◽  
Pressure Drops ◽  
Flow Channels ◽  
Mass Fluxes ◽  
Flow Pressure

Proton exchange membrane (PEM) fuel cells produce power with water and heat as inevitable byproducts. Accumulated liquid water within gas channel blocks the reactant flow and cause pressure drop along the gas channel. It is of extreme importance to accurately predict the liquid and gas two-phase flow pressure drop in PEM fuel cell flow channels. This pressure drop can be considered as an in-situ diagnostic tool that reveals information about the amount of liquid water accumulated within the flow channels. In this paper, the two-phase flow pressure drops are measured in ex-situ PEM fuel cell parallel flow channels. The pressure drops were measured for air mass fluxes of 2.4–6.3kg/m2s and water mass fluxes of 0.0071–1.28kg/m2s. These mass fluxes correspond to 2–5.33m/s and 7.14 × 10−6 – 0.0012m/s air and water superficial velocities, respectively. The measured two-phase flow pressure drops are then compared with different two-phase flow pressure drop models. Qualitative and quantitative comparison between the experimental results and existing models is provided in this work.

Visualization Study of Gas-Liquid Two-Phase Flow in a Hydrophobic Pipe

2007 ◽  
Author(s):  
Takayoshi Kikuchi ◽  
Tatsuya Hazuku ◽  
Yutaka Fukuhara ◽  
Tomoji Takamasa ◽  
Takashi Hibiki
Keyword(s):  
Flow Regime ◽  
Void Fraction ◽  
Gas Flow ◽  
Two Phase Flow ◽  
Flow Characteristics ◽  
Phase Flow ◽  
Two Phase ◽  
Experimental Conditions ◽  
Churn Flow ◽  
Effect Of Surface

To evaluate the effect of pipe wall surface wettability on flow characteristics in a vertical upward gas-liquid two-phase flow, a visualization study was performed using an acrylic pipe and a hydrophobic pipe. Such basic flow characteristics as flow patterns, pressure drop and void fraction were investigated in these pipes. In the hydrophobic pipe, an inverted-churn flow regime was observed in a region where the churn flow regime was observed in the acrylic pipe, while a droplet flow regime was observed in the region where an annular flow regime was observed in the acrylic pipe. At a high gas flow rate, the average void fraction in the hydrophobic pipe was higher than in the acrylic pipe. The effect of surface wall wettability on frictional pressure loss was confirmed to be insignificant under the present experimental conditions.

Two-phase flow distributors for fuel cell flow channels

Particuology ◽  
2010 ◽  
Vol 8 (6) ◽  
pp. 582-587 ◽  
Author(s):  
Hsiaotao T. Bi ◽  
Pierre Sauriol ◽  
Jürgen Stumper
Keyword(s):  
Fuel Cell ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Flow Channels

A critical review of two-phase flow in gas flow channels of proton exchange membrane fuel cells

2010 ◽  
Vol 195 (15) ◽  
pp. 4531-4553 ◽  
Author(s):  
Ryan Anderson ◽  
Lifeng Zhang ◽  
Yulong Ding ◽  
Mauricio Blanco ◽  
Xiaotao Bi ◽  
...  
Keyword(s):  
Fuel Cells ◽  
Critical Review ◽  
Gas Flow ◽  
Proton Exchange Membrane ◽  
Two Phase Flow ◽  
Proton Exchange ◽  
Phase Flow ◽  
Two Phase ◽  
Flow Channels ◽  
Exchange Membrane
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