Water transport through the gas diffusion layer (GDL) of a proton exchange membrane (PEM) fuel cell is of critical importance in the operation of the fuel cell. In this study, the transport of water vapor through the GDL is investigated. A one-dimensional, single-phase heat and mass transfer model is developed to investigate the diffusivity of water vapor through the GDL of a PEMFC. An experime...

Bismuth telluride nanowires are of interest for thermoelectric applications because of the predicted enhancement in the thermoelectric figure-of-merit in nanowire structures. In this letter, we carried out temperature-dependent thermal diffusivity characterization of a 40 nm diameter Bi2Te3 nanowires/alumina nanocomposite. Measured thermal diffusivity of the composite decreases from 9.2310−7 m2...

Preasymptotic transport of a scalar quantity passively advected by a velocity field formed by a large-scale component superimposed on a small-scale fluctuation is investigated both analytically and by means of numerical simulations. Exploiting the multiple-scale expansion one arrives at a Fokker-Planck equation which describes the preasymptotic scalar dynamics. This equation is associated with ...

We investigate the relationship between the effective diffusivity and effective drift of a particle moving in a random medium. The velocity of the particle combines a white noise diffusion process with a local drift term that depends linearly on the gradient of a gaussian random field with homogeneous statistics. The theoretical analysis is confirmed by numerical simulation. For the purely isot...

We present experimental results of mass transfer of a non reactive tracer gas (neon) measured in aerobic heterotrophic biofilm developed from activated sludge. Biofilms are grown in various hydrodynamic conditions and the effective diffusivity is used to quantify the mass transfer through the biofilm. Beyond some cross-flow conditions, the effective diffusivity through the biofilm seems larger ...

the drying behavior of green peas is investigated in a pilot scaled fluidized bed dryer (fbd) with inert particles assisted by an infra red (ir) heat source. the variation of shrinkage and moisture diffusivity with temperature and moisture content were investigated. the experimental drying curves were adjusted to the diffusion model of fick’s law for spherical particles. the result was that, al...

The spreading and diffusion of two-dimensional vortices subject to weak external random strain fields is examined. The response to such a field of given angular frequency depends on the profile of the vortex and can be calculated numerically. An effective diffusivity can be determined as a function of radius and may be used to evolve the profile over a long time scale, using a diffusion equatio...