Zijie Lu

Fundamental Research Needs in Combined Water and Thermal Management Within a Proton Exchange Membrane Fuel Cell Stack Under Normal and Cold-Start Conditions

Each fuel cell component of a proton exchange membrane fuel cell (PEMFC) used in automotive application operates most effectively (from performance and durability standpoints) within specific ranges of water content and temperature. The water and heat transport processes are coupled and present a challenge in providing the right balance over the entire range of operating conditions. Another important related aspect is CO poisoning of the electrocatalyst, which adversely affects the fuel cell performance. Freezing and cold-start present additional challenges for automotive PEMFCs. A critical review of the recent developments on these topics is presented in this paper. The study covers both the microscopic and macroscopic aspects of the transport within membrane, catalyst layers, gas diffusion layers, and gas channels, and an overview of the current PEMFC cooling technology. After discussing the current status, suggestions for future work on the above topics are presented.

Through-Plane Water Transport Visualization in a PEMFC by Visible and Infrared Imaging

In this study, water transport and thermal profile in the through-plane direction of a proton exchange membrane fuel cell (PEMFC) gas diffusion layer (GDL) are reported. Direct optical and infrared access to both cathode and anode GDLs are provided in a typical 50 cm test section. Dynamic visualization (pixel resolution of 0.6 lm at 28 Hz) of liquid water transport and emergence in the gas distribution channels and diffusion layers are reported and the underlying transport processes are discussed. The temperature distributions across the anode and cathode GDL are also measured with a high resolution infrared camera with a pixel resolution of 5 lm at 30 Hz. VC 2011 The Electrochemical Society. [DOI: 10.1149/1.3560163] All rights reserved.

Effective Thermal Conductivity of Gas Diffusion Layers Used in PEMFC: Measured with Guarded-Hot-Plate Method and Predicted by a Fractal Model

An experimental setup to determine thermal conductivity and thickness of a gas diffusion layer (GDL) as a function of compression was developed and calibrated. The actual thermal conductivities, based on compressed thickness, of plain Toray TGP-H gas diffusion layer (GDL) at compression pressures of 0.04 to 1.5 MPa and over temperature range of 25 C to 75 C are reported in this paper. The thermal conductivity of TGP-H GDL was found to decrease with temperature and to increase with compression. An effort was made to numerically account for the effective thermal conductivity by using theoretical models. Krischer model was found to be able to match with the experimental data, but this model relied on a priori knowledge of the thermal properties of the solid matrix. A new analytical model based on fractal analysis of GDL microstructure is proposed to account for GDL thermal conductivity as well as its variation with compression without using any empirical parameter.

Investigation of Water Transport in an Ex-Situ Experimental Facility Modelled on an Actual DOE Automotive Target Complient Fuel Cell

This work utilizes the channel design of a real fuel cell to study cathode side water transport in the gas channels of a proton exchange membrane fuel cell (PEMFC). All experimentation was performed under controlled water and air flow conditions aimed to meet the DOE targets [1] for the automotive fuel cells. The experimental facility provides independent control for water flow along the length of the channels to reduce the effects of channel pressure drop on the water flow. Details of channel design and instrumentation are described, as well as some initial results.Copyright

Through-Plane Water Transport Visualization in an Operating PEM Fuel Cell by Visible and Infrared Imaging

In this study, the liquid water emergence and transport within anode and cathode gas diffusion layers in an operating fuel cell was observed from the cross-section with a digital microscope and a high resolution infrared camera. In the cathode, water droplets were found to be formed on the channel side of the GDL cross-section, while little water was detected in the vicinity of the microporous layer. This finding suggested that water was condensing inside the GDL and may imply the existence of a condensation front, which has been predicted by numerical simulation but previously has not been verified experimentally. The anode results indicate that water was transported through anode GDL dominantly in the vapor form. The temperature distributions across the anode and cathode GDL were also measured with a high resolution infrared camera. These visualizations provided critical information on the water transport across a fuel cell.