Does filter housing size have an effect on CO2 scrubber efficiency?

[Sierra_Bravo]

I am currently using a 2.5" x 10" filter housing for my CO2 scrubber. I noticed the new single and dual "jumbo" CO2 scrubbers by BRS and they offer them with 4.5" x 10" housings. I was wondering if it makes any type of difference to use a 2.5" x 20" housing instead?

I understand that a 4.5x10 has 2/3 more soda lime capacity than the 2.5 x 20, but I am wondering if there would be extra contact time in a 20" chamber and if so, would it then pull more CO2 out of the same volume of air passing through it?

 

[Larry L]

I think the taller housing would let you go longer between replacing the media, but I'm not sure it will cause any more CO2 to be removed. I use the standard 10" housing and it turns purple pretty slowly from the bottom up, with a distinctly purple area at the bottom, fairly white just above it, and very little transition band in between, which makes me think the CO2 is removed within a short time of making contact with active media. If the contact time needed to be longer, I'd expect to see a more stretched-out gradient of purple at the bottom to white higher up.

 

[jccaclimber]

In short your larger cross sectional area results in more contact time despite the shorter distance. This is apparent without any math because the same flow rate is passing through a larger volume chamber, but to put some numbers to it take the case of a skimmer consuming 800 LPH air:

800 LPH = 0.8 m^3/hr = 0.8/3600 m^3/s.
Your 2.5" (0.0635 m) diameter circle has an area of 0.00317 m^2 (pi*(2.5/2*0.0254)^2).
Assuming uniform flow rate (close enough for this), this gives you a flow rate of 0.07 m/s and a contact time through your 20" (0.508 m) distance of 7.2 seconds.

Run this instead through a 4.5" (0.1143 m) diameter circle with an area of 0.01026 m^2 gives a velocity of 0.02 m/s which across 10" (0.254 m) takes a time of 11.7 seconds, or 62% more contact time.

 

[Sierra_Bravo]

In short your larger cross sectional area results in more contact time despite the shorter distance. This is apparent without any math because the same flow rate is passing through a larger volume chamber, but to put some numbers to it take the case of a skimmer consuming 800 LPH air:

800 LPH = 0.8 m^3/hr = 0.8/3600 m^3/s.
Your 2.5" (0.0635 m) diameter circle has an area of 0.00317 m^2 (pi*(2.5/2*0.0254)^2).
Assuming uniform flow rate (close enough for this), this gives you a flow rate of 0.07 m/s and a contact time through your 20" (0.508 m) distance of 7.2 seconds.

Run this instead through a 4.5" (0.1143 m) diameter circle with an area of 0.01026 m^2 gives a velocity of 0.02 m/s which across 10" (0.254 m) takes a time of 11.7 seconds, or 62% more contact time.

Thanks for that detailed breakdown.