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AU-BCE-EE / tric-fil-mod

A trickling filter model to simulate air treatment, written in Python
GNU General Public License v3.0
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porosity-adjusted gas velocity #19

Open afeilberg opened 5 months ago

afeilberg commented 5 months ago

In relation to gas porosity, I saw that it is included in the gas residence time (line 173 in mod_funcs: L por_g / v_g) and in the gas volume (line 203 in mod_funcs: vol_gas = vol_tot por_g ), so I guess it should be okay with respect to the advection of air through the filter and concentration vs position. can you help checking this to make sure @sashahafner Not sure exactly if residence time (rt_gas) is used for anything other than as an output?

sashahafner commented 5 months ago

Residence time rt_gas is just for output, right.

I agree there doesn't seem to be anything porosity-related missing in the model function. Gas and water volume are calculated for each layer based on gas porosity por_gand specific water content or whatever we should be calling por_l. And flow rates for the rates function are superficial, i.e., per unit total cross-sectional area. That seems right.

sashahafner commented 5 months ago

But I am surprised that the Kga_onda function just uses superficial velocity. por_g is only used for characteristic packing length here (L23): 

    dp = 6 * (1 - por_g) / ssa  # characteristic packing length

And then v_g only here, without any porosity adjustment (L42):

    kg = dp_emp * (v_g * dens_g / (ssa * visc_g))**0.7 \
        * (visc_g / (dens_g * Dg))**(1 / 3) * (ssa * dp)**-2 * ssa * Dg

Is that correct?

afeilberg commented 5 months ago

I just checked a few papers and yes the Onda correlations use superficial fluid velocities as input. These are empirical correlations, so the influence of porosity must be embedded somehow, but it is not very transparent. I will check some more literature...

andreasen et al 2013.pdf