Measurement of Water, Temperature and Current Distributions in Anode of Polymer Electrolyte Fuel Cell During Low Humidity Operation

2011 ◽  
Author(s):  
Kosuke Nishida ◽  
Yoma Yokoi ◽  
Kazumasa Umeda ◽  
Shohji Tsushima ◽  
Shuichiro Hirai
Keyword(s):  
Water Vapor ◽  
Fuel Cell ◽  
Water Distribution ◽  
Vapor Concentration ◽  
Test Paper ◽  
Counter Flow ◽  
Flow Configuration ◽  
Current Distributions ◽  
Anode Electrode ◽  
Low Humidity

In order to prevent membrane dryout in polymer electrolyte fuel cells (PEFCs) during low humidity operation, it is essential to understand the fundamental phenomena of the water transport and reaction distribution at the anode side in an operating fuel cell. In this study, the water vapor distribution along the anode flow channel of a PEFC under low humidity conditions was quantitatively evaluated by using humidity test paper (HTP), and the effects of flow configuration and inlet humidification on the water distribution in the anode were investigated. HTP is a test paper for detecting water vapor of 20–90% RH, which is coated with a blue surface. This test paper was inserted between the anode electrode and separator in the transparent fuel cell, and the discoloration of HTP was directly visualized using a digital CCD camera. Furthermore, the temperature and current distributions in the anode electrode were measured using IR thermography and segmented cell structure concept. It was found that the water vapor concentration on the anode side increases immediately after the startup because of the back diffusion of the product water from the cathode to anode. In the case of the co-flow configuration with the dry anode and cathode inlets, the water vapor concentration increases monotonically along the anode flow channel. In addition, the anode water distribution affects the temperature and current distributions in the fuel cell largely. The local temperature and current density at the dry anode inlet are lower than those in the downstream region because of the membrane dehydration and low proton conductivity. On the other hand, in the case of the counter-flow pattern, the distributions of water concentration, temperature and current density have the maximum points in the midstream region. The counter-flow configuration is effective in improving the membrane hydration and alleviating the anode dryout.

Measurement of Water Distribution in Anode of Polymer Electrolyte Fuel Cell Under Low Humidity Conditions

2009 ◽  
Author(s):  
Kosuke Nishida ◽  
Yohma Yokoi ◽  
Shohji Tsushima ◽  
Shuichiro Hirai
Keyword(s):  
Water Vapor ◽  
Fuel Cell ◽  
Flow Field ◽  
Polymer Electrolyte ◽  
Water Distribution ◽  
Back Diffusion ◽  
Anode Side ◽  
Test Paper ◽  
Anode Electrode ◽  
Low Humidity

During low humidity operation of polymer electrolyte fuel cells (PEFCs), water management in anode electrode is essential for achieving sufficient membrane hydration and high proton conductivity. In this study, the water vapor condensation in an operating PEFC under low humidity conditions was experimentally visualized by using water sensitive paper (WSP), and the water distribution on the anode side was investigated. WSP is a test paper for detecting water droplets, fog and high humidity, which is coated with a yellow surface. This test paper was inserted between the anode electrode and separator in the transparent fuel cell. Furthermore, the dew-point temperature at the anode outlet was simultaneously measured using a hygro-thermometer, and the effects of operating conditions and flow configuration on the water transports between the anode and cathode electrodes were discussed. It was found that the water vapor concentration on the anode side increases considerably after the startup because of the back diffusion of the product water, and the water condensation occurs from the downstream section of the anode channel in the co-flow arrangement. However, at high current densities, the amount of water in the anode decreases due to the water flux driven by electro-osmotic drag. The difference of the water vapor concentrations between the anode and cathode electrodes arises significantly with cell temperature, and the back diffusion flux of water toward the anode increases. The counter-flow pattern of anode and cathode gases is effective in achieving uniform water distribution in the anode flow field. The dry H2 at the anode inlet is humidified by the water diffused through the membrane from the cathode outlet, and thus sufficient water can be supplied all over the anode flow field.

scholarly journals A Coated Spherical Microresonator for Measurement of Water Vapor Concentration at PPM Levels in Very Low Humidity Environments

2018 ◽  
Vol 36 (13) ◽  
pp. 2667-2674 ◽  
Author(s):  
Arun Kumar Mallik ◽  
Gerald Farrell ◽  
Dejun Liu ◽  
Vishnu Kavungal ◽  
Qiang Wu ◽  
...  
Keyword(s):  
Water Vapor ◽  
Vapor Concentration ◽  
Water Vapor Concentration ◽  
Low Humidity

Numerical Simulation of Metal-Supported Solid Oxide Fuel Cell (mSOFC)

2009 ◽  
Author(s):  
Niwat Phoocharoen ◽  
Jarruwat Charoensuk
Keyword(s):  
Fuel Cell ◽  
Solid Oxide Fuel Cell ◽  
Solid Oxide ◽  
Maximum Power ◽  
Peak Temperature ◽  
Cathode Side ◽  
Oxide Fuel ◽  
Counter Flow ◽  
Flow Configuration ◽  
Concentration Loss

In this paper we present the numerical results of planar solid oxide fuel cell at the level of membrane electrode assembly, MEA. The study is aimed at evaluating the performance of metal-supported design versus the conventional anode-cathode support under co-flow and counter-flow conditions. We have found that the value of peak temperature is lower therefore better temperature distribution is achieved for metal supported design with counter-flow configuration. Moreover the corresponding current density at maximum power is also higher with this configuration. This later design however possesses greater concentration loss or over-potential due to fuel concentration gradient at the porous layer of supporting metal. To compensate this difference, we have proposed the modification of the current collector at the cathode side to reduce the ohmic loss, while minimizing the concentration loss at the reaction site. The result of this modification suggests an improvement of maximum power density from 0.984 W/cm2 to 1.034 W/cm2. This is slightly less than the value of an original version for only 0.132%. At this counter-flow configuration the value of peak temperature is also lower as compared with its counterpart with co-flow configuration.

scholarly journals The stability and calibration of water vapor isotope ratio measurements during long-term deployments

2015 ◽  
Vol 8 (5) ◽  
pp. 5425-5466 ◽  
Author(s):  
A. Bailey ◽  
D. Noone ◽  
M. Berkelhammer ◽  
H. C. Steen-Larsen ◽  
P. Sato
Keyword(s):  
Water Vapor ◽  
Concentration Dependence ◽  
Hydrological Cycle ◽  
Dew Point ◽  
Vapor Concentration ◽  
Mauna Loa ◽  
Laser Absorption ◽  
Low Humidity ◽  
The Stability

Abstract. With the recent advent of commercial laser absorption spectrometers, field studies measuring stable isotope ratios of hydrogen and oxygen in water vapor have proliferated. These pioneering analyses have provided invaluable feedback about best strategies for optimizing instrumental accuracy, yet questions still remain about instrument performance and calibration approaches for multi-year field deployments. With clear scientific potential for using these instruments to carry out long-term monitoring of the hydrological cycle, this study examines the long-term stability of the isotopic biases associated with three cavity-enhanced laser absorption spectrometers – calibrated with different systems and approaches – at two remote field sites: Mauna Loa Observatory, Hawaii, USA, and Greenland Environmental Observatory, Summit, Greenland. The analysis pays particular attention to the stability of measurement dependencies on water vapor concentration and also evaluates whether these so-called concentration-dependences are sensitive to statistical curve-fitting choices or measurement hysteresis. The results suggest evidence of monthly-to-seasonal concentration-dependence variability – which likely stems from low signal-to-noise at the humidity-range extremes – but no long-term directional drift. At Mauna Loa, where the isotopic analyzer is calibrated by injection of liquid water standards into a vaporizer, the largest source of inaccuracy in characterizing the concentration-dependence stems from an insufficient density of calibration points at low humidity. In comparison, at Greenland, the largest source of inaccuracy is measurement hysteresis associated with interactions between the reference vapor, generated by a custom dew point generator (DPG), and the sample tubing. Nevertheless, prediction errors associated with correcting the concentration-dependence are small compared to total measurement uncertainty. At both sites, a dominant source of uncertainty is instrumental precision at low humidity, which cannot be reduced by improving calibration strategies. Challenges in monitoring long-term isotopic drift are also discussed in light of the different calibration systems evaluated.

Comparison of Feeding Gas Strategies (Co- and Counter-Flow) in a PEM Fuel Cell Through a Pseudo 2D Diphasic Water Model

2008 ◽  
Author(s):  
Sylvain Chupin ◽  
Julien Ramousse ◽  
Kodjo Agbossou ◽  
Yves Dube´ ◽  
Sophie Didierjean ◽  
...  
Keyword(s):  
Fuel Cell ◽  
Liquid Water ◽  
Water Distribution ◽  
Pem Fuel Cell ◽  
The Other ◽  
Water Model ◽  
Counter Flow ◽  
Cell Control ◽  
Water Flows ◽  
2D Model

The purpose of this study is to establish a simple model representing diphasic water flows in a single cell PEM fuel cell in order to improve fuel cell control. The pseudo-2D model describes the water transfers from one electrode to the other, all along the feeding gas channels. Both vapor and liquid water are considered. The location of first appearance of liquid water can be noticed. The influence of the feeding gas strategies (co- and counter-flow) on the water distribution in the cell are investigated. As a consequence, with the counter-flow feeding gas strategy, water is better distributed in the whole cell, but flooding of the electrode may occur. With a co-flow feeding gas strategy flooding risks are lower, but water distribution in the cell is less homogeneous and could result in a early deterioration of the membrane by drying.

In-Situ Optical Measurements of Water Vapor Concentration and Temperature in a Proton Exchange Membrane Fuel Cell at Steady State and Under Dynamic Cycling

2009 ◽  
Author(s):  
Ritobrata Sur ◽  
Thomas J. Boucher ◽  
Michael W. Renfro ◽  
Baki M. Cetegen
Keyword(s):  
Water Vapor ◽  
Fuel Cell ◽  
Partial Pressure ◽  
Diode Laser ◽  
Pem Fuel Cell ◽  
Tunable Diode Laser ◽  
Cathode Side ◽  
Vapor Concentration ◽  
Water Vapor Concentration

A robust, accurate and fast in-situ sensor was developed for detection of water vapor partial pressure and temperature simultaneously at the anode and cathode channels of a PEM fuel cell. Tunable diode laser absorption spectroscopy (TDLAS) utilizing wavelength modulation (WMS) was employed for these measurements. This method determines the ratio of the second and first harmonics (2f/1f) of the spectroscopic absorption profile of water vapor by the aid of a software lock-in amplifier. Measurements were taken using a diode laser emitting around a wavelength of 1471 nm where the water vapor absorption exhibits significant sensitivity to partial pressure and temperature. Measurements of water vapor concentration and temperature in were taken at steady and dynamic operating conditions in the anode and cathode gas channels near the inlet and outlet ports of a serpentine channel PEM fuel cell with Nafion membrane of active area 50 cm2. Different load and inlet humidity conditions were tested to characterize the operation at different conditions. The partial pressure of water vapor increases towards the exit of both the gas channels, but the increase is found to be more significant on the cathode side. The dynamic operation of the fuel cell was also examined in this study as well as the simultaneous measurements at the anode and cathode gas channels.

scholarly journals Modeling the dynamic behavior of a droplet evaporation device for the delivery of isotopically calibrated low-humidity water vapor

2021 ◽  
Vol 14 (6) ◽  
pp. 4657-4667
Author(s):  
Erik Kerstel
Keyword(s):  
Water Vapor ◽  
Dynamic Behavior ◽  
Evaporation Rate ◽  
Quantitative Description ◽  
Droplet Surface ◽  
Vapor Concentration ◽  
Dry Air ◽  
Low Humidity ◽  
Fractionation Factors ◽  
Water Isotope

Abstract. A model is presented that gives a quantitative description of the dynamic behavior of a low-humidity water vapor generator in terms of water vapor concentration (humidity) and isotope ratios. The generator is based on the evaporation of a nanoliter-sized droplet produced at the end of a syringe needle by balancing the inlet water flow and the evaporation of water from the droplet surface into a dry-air stream. The humidity level is adjusted by changing the speed of the high-precision syringe pump and, if needed, the dry-air flow. The generator was developed specifically for use with laser-based water isotope analyzers in Antarctica, and it was recently described in Leroy-Dos Santos et al. (2021). Apart from operating parameters such as temperature, pressure, and water and dry-air flows, the model has as “free” input parameters: water isotope fractionation factors and the evaporation rate. We show that the experimental data constrain these parameters to physically realistic values that are in reasonable to good agreement with available literature values. With the advent of new ultraprecise isotope ratio spectrometers, the approach used here may permit the measurement of not only the evaporation rate but also the effective fractionation factors and isotopologue-dependent diffusivity ratios, in the evaporation of small droplets.

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