John Borrelli

Abstract

Water management is one of the most important challenges in polymer electrolyte membrane fuel cell (PEMFC) development. Water is a product of the fuel cell reaction, and it can accumulate in the gas diffusion medium (GDM) adjacent to the air distribution channels of a cathode flow field plate. While some water retention is necessary for membrane hydration, the majority must be removed from the cathode flow field channels for optimal stack performance.

The experiments of the present work utilize high-speed digital images to analyze water as it flows through a GDM sample and into a 1.08 mm hydraulic diameter rectangular channel of flowing air. The 25-cm-long air channel is held horizontal with the GDM acting as the top wall of the channel.

Three GDM samples are tested under the same water and air flow rates, and high speed videos are used to measure departure droplet diameter, advancing and receding contact angles, and to report general flow patterns that are observed.

Results show a general agreement between GDM Samples A and B with respect to departure droplet behavior, contact angle data, and general two-phase flow behavior across the test matrix, but the GDM Sample B data show greater spread than the GDM Sample A data for departure droplet diameter. GDM Sample C data show some droplet formation, but the departure droplet diameters are markedly larger than those of GDM Samples A and B. Furthermore, as the GDM Sample C testing progressed through the test matrix (from highest air flow rate to lowest), all droplet activity ceased. In general, the flow patterns for GDM Sample C were identical to the typical two-phase flow patterns observed in conventional minichannel flow visualization experiments. Experimental two-phase pressure drop measurements were found to be much higher for the GDM Sample B data than for the Sample C data, but existing theoretical two-phase pressure drop correlations were found to closely predict the experimental pressure drop data depending on the different flow conditions for Samples B and C.

Library of Congress Subject Headings

Two-phase flow; Flow visualization; Fluid-structure interaction; Fuel cells--Analysis; Polyelectrolytes

Publication Date

6-2005

Document Type

Thesis

Student Type

Graduate

Degree Name

Mechanical Engineering (MS)

Department, Program, or Center

Mechanical Engineering (KGCOE)

Advisor

Satish G. Kandlikar

Advisor/Committee Member

Abhijit Mukherjee

Advisor/Committee Member

Thomas A. Trabold

Comments

Physical copy available from RIT's Wallace Library at TA357.5.M84 B67 2005

Campus

RIT – Main Campus

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