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Research Papers

# Design and Validation of a Water Transfer Factor Measurement Apparatus for Proton Exchange Membrane Fuel Cells

[+] Author and Article Information
Pierre Sauriol, X. Tony Bi

Department of Chemical and Biological Engineering, University of British Columbia, 2360 East Mall, Vancouver, BC, V6T 1Z3, Canada

David S. Nobes

Department of Mechanical Engineering, University of Alberta, 4-9 Mechanical Engineering Building, Edmonton, AB, T6G 2G8, Canada

Jürgen Stumper1

Ballard Power Systems, 9000 Glenlyon Parkway, Burnaby, BC, V5J 5J8, Canadajurgen.stumper@ballard.com

Dustin Jones, Darwin Kiel

Coanda Research & Development Corporation, Suite 110A, 3430 Brighton Avenue, Burnaby, BC, V5A 3H4, Canada

1

Corresponding author.

J. Fuel Cell Sci. Technol 6(4), 041014 (Aug 17, 2009) (13 pages) doi:10.1115/1.3007900 History: Received June 20, 2007; Revised March 12, 2008; Published August 17, 2009

## Abstract

The investigation of water management within proton exchange membrane fuel cells (PEMFCs) has led to the definition of a water transfer factor to describe the net transfer of water across the membrane. In most fuel cells, the total amount of water transferred across the membrane is a small fraction of the total water passing through the fuel cell, and therefore experimental measurements of the water transfer factor have been very difficult to achieve in practice. This paper presents a four-step systematic approach to design and validate a measurement concept that will enable the measurement of the water transfer factor with the desired accuracy. These steps are: (1) several key equations are obtained from mass balance; (2) potential measurands are screened by sensitivity analysis; (3) the performance of interesting measurement concepts is simulated by a Monte Carlo approach to account for the variability of the instrument performance and other operational considerations; and (4) validation tests are achieved in a simulated fuel cell configuration to determine measurement accuracy of the selected measurement concept. Four key equations were derived from mass balance considerations allowing for the determination of the water transfer factor. The sensitivity analysis showed that measurement concepts that relied on the differential mass flow rate and the differential water content would yield the best accuracy. However, these measurement concepts were found to involve a great risk associated with the development or adaptation of key measurement instruments. A more conventional measurement concept, which utilizes precision liquid injection by syringe pumps and water content measurement by infrared absorption, was therefore selected. The measurement concept was further improved by implementing a reference injection, which, based on the virtual experiments using Monte Carlo calculations, allowed for an order of magnitude improvement in the accuracy. From the validation tests it was determined that combining anode and cathode side measurements, the measurement concept has an accuracy better than $±0.01$ on the water transfer factor.

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## Figures

Figure 1

Illustration of the subcell approach to mimic a full-sized PEMFC

Figure 2

Range of expected water transfer accuracy calculated from the sensitivity analysis. The different measurands assumed are indicated by the equation number; the number of subcells was varied to show the trade-off between accuracy and spatial resolution.

Figure 3

Measurements concepts with syringe pump and infrared sensor: (a) measurement concept 1, two mass flow meters and infrared sensor and (b) measurement concept 2, two mass flow meters and infrared sensor with reference injection. Dashed lines indicate streams and instruments that are used during the reference injection.

Figure 4

Expected accuracy in the water transfer factor calculated from the Monte Carlo virtual experiments; full symbols: full system simulation (see Fig. 3) and hollow symbols: simulated fuel cell configuration (see Fig. 5)

Figure 5

Configuration used for the concept validation experiments

Figure 6

Typical results from a concept validation experiment: (a) raw water molar fraction at the infrared sensor for a given injection sequence and (b) corresponding water transfer factor for two different averaging times

Figure 7

Influence of the gas composition on the infrared sensor response

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