QUANTIFICATION OF TEMPERATURE DRIVEN FLOW IN A POLYMER ELECTROLYTE FUEL CELL USING HIGH-RESOLUTION NEUTRON RADIOGRAPHY

Open Access
Author:
Hatzell, Marta Catherine
Graduate Program:
Mechanical Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
None
Committee Members:
  • Clinton Matthew Mench, Thesis Advisor
  • Matthew M Mench, Thesis Advisor
Keywords:
  • Water Managment
  • Temperature Driven Flow
  • PEM Fuel Cell
Abstract:
A temperature gradient is known to exist within the fuel cell components during operation and for sometime after shutdown. In this study, a controlled temperature gradient across a single fuel cell was quantitatively investigated using high-resolution neutron imaging. The direction of liquid water transport under isothermal and non-isothermal conditions was observed in both hydrophilic and hydrophobic diffusion media (DM). The change in distribution of liquid saturation with time revealed two different mechanisms of water transport within the DM acting in opposite directions, and the balance between these two mechanisms was investigated. A maximum liquid saturation plateau of ca. 30% was shown for all conditions tested, suggesting the critical transition between pendular and funicular modes of liquid water storage was captured. Both average cell temperature and the magnitude of temperature gradient were shown to significantly affect the rate of condensation within the DM. Reducing the temperature gradient by 50% decreased the condensation rate by 220%, while halving the average cell temperature reduced the condensation rate by 560%. Experimental results were compared with water saturation distribution model predictions from literature and show reasonable qualitative agreement. Finally it was concluded that current available models significantly over predict vapor phase transport in saturated fuel cell media.