Hey there,
I was wondering if anyone knows the source/theoretical basis behind the film diffusion limited rate law governing silylene decomposition (SiH2 → Si + H2) in the 3D silane pyrolysis PIC tutorial? I’ve looked through the Couderc 1995 paper, which explains the “assume heterogeneous reaction rate is infinite” assumption, but I’m having trouble finding the equations for film diffusion resistance that were used here. A quick Google Scholar search for Sherwood number diffusion rate laws has not helped, maybe there are other keywords I should be using?
Thanks!
Update: I think I finally found it! The Sherwood number concept is very common in mass transfer calculations and described in a lot of books i.e. in Chapter 11 of Fluidization Engineering, “Particle-to-Gas Mass and Heat Transfer”. From Sherwood number, you can get the mass transfer coefficient k_f = (GasDiffusivity * SherwoodNumber / ParticleDiameter) which has units of (m/s), and from there you need reactant pressure/other gas-phase data to get to film resistance and ultimately a per-particle rate. This last part is described in the CES publication “Particle-scale study of heat and mass transfer in a bubbling fluidised bed” and the documentation for the “METC Gasifier Advanced Simulation (MGAS) model”.
I hope this is helpful to someone!