O'Reilly logo

PEM Fuel Cells by Ken S. Chen, Yun Wang

Stay ahead with the world's most comprehensive technology and business learning platform.

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, tutorials, and more.

Start Free Trial

No credit card required

3.3 Constitutive Equations

The basic constitutive equations relate the fluxes of heat, species, and momentum to the field variables and material properties. A simple molecular model is presented below to provide a qualitative estimate (on the order of magnitude) of the transport coefficients.

3.3.1 A Lattice Model

Diffusion stems from the random molecular walks of constituent particles. Figure 3-3 shows a simple Lattice model with an assumption that the movement of a molecule occurs only along any of the six directions. For a particle, the probability of moving in one direction is 1/6, assuming that the chance for movement in each direction is the same. The flux in the x direction, denoted as fx (which can be heat, species or momentum flux), ...

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, interactive tutorials, and more.

Start Free Trial

No credit card required