Study on Freezing Phenomena in Pem Fuel Cell Blow Freezing

Tabe, Yutaka; Nakamiya, H.; Kikuta, Kazushige; Chikahisa, Takemi; Kagami, Fumio; Yoshizawa, Koudai

doi:10.1615/ihtc13.p3.80

Cited by 9 publications

(11 citation statements)

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“…The cell resistance and the voltage at -10 °C are nearly constant from 300 to 400 seconds, and the operation shuts down around 580 seconds. This can be explained with previous research by the authors showing that the water produced by the cathode reaction is at a supercooled liquid state in the cell at -10 °C relatively-near to zero [10]. Thus, the cold start -5 -characteristics at -20 °C and -10 °C are governed by different phenomena, and a longer operation at -10 °C is possible before the shutdown with a same initial wet condition.…”

Section: Cold Start Characteristics and The Effect Of Start-up Tempersupporting

confidence: 73%

“…The produced water at the -10 °C cold start reaches the interface between the catalyst layer and the MPL where it remains as a supercooled liquid water film for some time before it freezes, (Fig. 9(b)), this is a reason why the released heat of solidification due to the freezing can be detected by infrared thermography [10][11][12]. The freezing at the interface triggers the operation shutdown, and in total the freezing mechanism and cold start characteristics differ, depending on whether supercooled water can exist in a cell.…”

Section: Observation Of Ice Distribution and Evaluation Of The Freezimentioning

confidence: 99%

“…Recently, cryo-SEM observations were conducted to elucidate further details of the ice distribution in the catalyst layer at -25 °C or -20 °C; these observations were carried out with the examined components kept at very low temperature and in vacuum conditions to avoid thawing and covering by frost deposits [6][7][8][9]. At temperatures closer to zero, like -10 °C, it was reported that the produced water is present in a supercooled state, and that the freezing behavior in a PEFC can be visualized by infrared thermography and it was possible to capture the 2-dimensional propagation in the high temperature region caused by the release of heat due to freezing [10][11][12]. Thus, the characteristics of the cold start using specific cells and start-up temperatures, and the effects of the water freezing in the cell on the performance deterioration have been reported.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Cold start characteristics and freezing mechanism dependence on start-up temperature in a polymer electrolyte membrane fuel cell

Tabe

Saito

Fukui

et al. 2012

Journal of Power Sources

131

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Cold start characteristics of a polymer electrolyte membrane fuel cell are investigated experimentally, and microscopic observations are conducted to clarify the freezing mechanism in the cell. The results show that the freezing mechanism can be classified into two types: freezing in the cathode catalyst layer at very low temperature like −20 °C, and freezing due to supercooled water at the interface between the catalyst layer and the gas diffusion layer near 0 °C like −10 °C. The amount of water produced during the cold start is related to the initial wetness condition of the polymer electrolyte membrane, because water absorption by the membrane due to back diffusion plays an important role to prevent the water from freezing. It is also shown that after the shutdown of the cold start the cell performance of a subsequent operation at 30 °C is temporarily deteriorated after the freezing at −10 °C, but not after the freezing at −20 °C. The ice formed at the interface between the catalyst layer and the gas diffusion layer is estimated to cause the temporary deterioration, and the function of a micro porous layer coating the gas diffusion layer for the ice formation is also discussed. Highlights• Two freezing types at cold start in and on the surface of a cathode catalyst layer • Direct observation of the ice formed on the catalyst layer surface • Temporary performance deterioration at 30 °C caused by ice on the surface

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Section: Cold Start Characteristics and The Effect Of Start-up Tempersupporting

confidence: 73%

Section: Observation Of Ice Distribution and Evaluation Of The Freezimentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Cold start characteristics and freezing mechanism dependence on start-up temperature in a polymer electrolyte membrane fuel cell

Tabe

Saito

Fukui

et al. 2012

Journal of Power Sources

131

View full text Add to dashboard Cite

show abstract

“…With regard to freezing at temperatures closer to zero, like −10 • C, it was reported that the produced water is present in a supercooled state, and that the freezing behavior in a PEFC can be visualized by infrared thermography. 8 The freezing was captured as a 2-dimensional propagation in the higher temperature region (≤0 • C) caused by the release of heat due to the freezing. Ice or frost formation on the catalyst layer (CL) surface above −3 • C was observed directly thorough a silver mesh used as the cathode gas diffusion layer (GDL).…”

mentioning

confidence: 99%

Ice Formation Processes in PEM Fuel Cell Catalyst Layers during Cold Startup Analyzed by Cryo-SEM

Tabe

Yamada

Ichikawa

et al. 2016

J. Electrochem. Soc.

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For further improvements in the startup ability below freezing and the durability of polymer electrolyte fuel cells, understanding the ice formation mechanism during cold startup is particularly significant. This study observes cross-sectional ice distributions in a catalyst layer (CL) during isothermal galvanostatic operation at −20 • C using a cryo-scanning electron microscope. The effects of current density, cathode gas conditions, initial water content of the membrane, and cell temperature on the cold start characteristics and the ice formation process in the CL are evaluated. The observational results show that at higher current densities, the region with active ice formation moves from the membrane to the gas diffusion layer sides during the freezing period and vacant pores remain near the membrane even after cell shutdown, while the pores are completely filled with nearly-uniformly growing ice at lower current density operation. This is consistent with the experimental finding from the cold start characteristics that the estimated amount of ice accumulated in the cell until the shutdown decreases as the current density increases. Contrary to expectations, these changes are largely independent of cathode gas conditions, even with pure oxygen. Additional factors controlling the ice formation process are discussed based on the experimental results. The polymer electrolyte fuel cell (PEFC) is a potential candidate for automotive power sources and portable electricity generators because of its characteristics of high efficiency, high power density, low operating temperature, and other advantageous characteristics. In cold climates, however, ensuring startup and durability of PEFCs at subfreezing conditions is a critical issue for the practical use of PEFC. It has been reported that freezing of water produced by the cathode reaction induces shutdown (voltage failure) during startup at subfreezing temperatures, and this freezing causes various kinds of degradation of the cell performance.1-3 Therefore, a number of practicable strategies based on thermal management and control of the residual water present in the cell before cooling and starting have been developed. However, a basic understanding of details of the ice formation process at cold startup, which is particularly-significant for further improvements in the cold startup ability and durability, remains insufficiently addressed in the literature.Some modeling studies have been conducted to describe the heat and mass transfer, and ice formation during cold startup. [4][5][6][7] The research group of the authors has investigated the performance of a PEFC at temperatures below the freezing point by both simulation and experiments.4 That study identified the initial temperature at which self-starting becomes possible, and this is determined by the balance of the produced heat and water generated due to the reaction. With regard to freezing at temperatures closer to zero, like −10• C, it was reported that the produced water is present in a supercooled state, a...

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“…The thermographs showed the 2-dimentional propagation in the higher temperature region to be caused by the released solidification heat [3]. Ishikawa et al…”

Section: Introductionmentioning

confidence: 99%