Experimental Study of Thermal Conductivity of Catalyst Layer of Polymer Electrolyte Membrane (PEM) Fuel Cells
Bibliographic record
Abstract
Efficient operation of a typical automotive PEM fuel cell occurs at a certain range of temperature from 60˚C to 80˚C. At temperatures below 60˚C, the kinetics of the electrochemical reaction slows down, and the electrodes are more prone to being flooded by the liquid water due to the higher possibility of saturation of the produced water at lower temperatures. At temperatures above 80˚C, the membrane dries out, and consequently, ohmic losses attributed to proton transport through the membrane increase. In addition to these performance consequences, PEM fuel cells will face durability issues if they operate outside the mentioned temperature range; breaking down of membrane at high temperatures due to its glass transition at temperatures around 80˚C as well as damage to various components of the fuel cell due to ice expansion during freezing are some of the mentioned durability issues. Therefore, as is clear, water management, thermal control, and degradation minimization are highly and intricately correlated to each other, among which thermal control can be considered as the core controlling factor which directly affects the others. Performing an effective thermal management is hinged on having detailed knowledge about the temperature distribution inside various layers, and the key to finding such information is to have the thermal conductivity of various layers. The thermal conductivity of PEM fuel cell gas diffusion layers (GDL) is well understood, and some experimental data on thermal conductivity of other components have been provided in literature. However, the thermal conductivity of the catalyst layer, where most of the heat generation modes occur, is still unknown. Accordingly, this work is concerned with measurement of this property through two different approaches: the guarded heat flux method and the transient plane source method. In the guarded heat flux method which works based on steady-state measurement of temperature distribution inside the sample, the catalyst samples are placed in between two fluxmeters which introduce a constant heat flow rate through the samples, whereas in the transient plane source method which works based on a transient measurement of temperature inside the sample, two halves of catalyst sandwich the transient plane source sensor.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".