Coupling of Pore-Phase and Solid-Phase Networks for Simulating Heat and Mass Transport in Porous Transport Layers

Sunday, 1 October 2017: 14:40
Maryland A (Gaylord National Resort and Convention Center)
V. Konduru and J. S. Allen (Michigan Technological University)
Reactant, water, and heat transport through Porous Transport Layers (PTL), also known as Gas Diffusion Layers (GDL), can be simulated using a variety of computational architectures and transport models. A common approach is to create detailed reconstruction of geometry from tomographic data and use a Lattice-Boltzmann model for computing transport within the material. Another common approach is to simulate the material using a network of transport resistance elements and then use continuum, phenomenological, or Lattice Boltzmann models for computing transport through the network.

For either approach the computational domain should be representative of the morphology and structure of the PTL being simulated. Geometric reconstructions of tomographic data naturally capture the morphology and structure, but at great computational expense when simulating heat and mass transport. A computationally efficient method is to create an abstraction of the PTL in a simple, regularized domain known as a pore-network model (PNM). This latter approach resolves the issue of computational expense, but lacks a clear relationship to the original structure and morphology of the PTL that is generally stochastic.

The stochastic morphology of a PTL can be characterized using a probability distribution of void volume size, known as a pore size distribution, which is invariant with respect to sample size. Pore size distribution data can be obtained using porosimetry or tomography and is almost universally based on spherical pore volumes.

This presentation discusses a methodology for transforming a spherical pore size distribution data into a pore-network model domain. This methodology maintains the appropriate stochastic distribution, physical size and bulk porosity of the original PTL. The resulting PNM domain is unique to the original PTL sample; meaning that the pore-network is material or manufacturer specific. Thus, simulation of reactant and water transport is also material or manufacturer specific.

The methodology developed transforms a spherical-pore size distribution into a regularly-spaced network of pore cylinders; referred to as the pore-phase network. In order to simulate thermal transport in a PTL using the PNM architecture, the solid portion of the original material must also be transformed into a complimentary solid-phase network. The solid-phase network should also preserve the original stochastic morphology and bulk porosity of the PTL. In this methodology, the two networks (pore-phase and solid-phase) are generated independent of one another, connected only through the distribution of unit cell porosities. In this manner thermal transport through the solid-phase network can be validated independently of liquid water transport through the pore-phase network and vice-versa. When combined, the dual PNM networks capture the coupled thermal and mass transport through the PTL.