Air bubbles
- Thread starter badfish
- Start date
x2 
Miguel;787474; said:
Surface tension has nothing to do with gas exchange, gas exchange takes place across any gas liquid interface, specifically the surface of the water and the surface of the bubbles, the smaller the bubbles the more surface area there will be for a given air pump.
IITUFFTOBEATII;787512; said:
You are certainly more technically minded than I, but if i have bubbles and water movement and circulation on the surface, I am (i) breaking the surface tension and (2) also promoting gas exchange, across, as you put it, the gas/liquid interface..did i say anything terribly wrong?
Miguel;787586; said:You are certainly more technically minded than I, but if i have bubbles and water movement and circulation on the surface, I am (i) breaking the surface tension and (2) also promoting gas exchange, across, as you put it, the gas/liquid interface..did i say anything terribly wrong?
no you didnt, except that surface tension does not have any effect on gas transfer. If you have a film (pond scum) on your surface that will effect gas transfer, but the actual surface tension of the water will not.
The term "interface" comes from Lewis and Whitman (1924) who first introduced the idea if a two-film boundary layer to describe the mass transfer of gases. In most fields that deal with gas exchange this is the accepted term for the boundary where the gas and liquid interact
DeLgAdO;788242; said:i like the way you think
thanks. I do what I can. I mostly lurk on here, but I try to chime in from time to time with some helpful things I have picked up. And I have a grip of textbooks laying around here, never sold any of them back. It helps that I went to a school whose engineering program puts a lot of emphasis on environmental issues and water quality (Ca school), they also have a hydraulics lab that is larger (sf) than the house I live in
Most oxygen transfer happends at the waters surface, this is due to the rippling effect caused when the bubbles hit the surface.
A powerhead pointed towards the surface is a better option the an airstoneas the actual bubbles from an airstone do little in the way of adding oxygen whilst in the water column. Instead, as stated, it is the extra surface area due to the rippling water which adds the bulk of oxygen.
So if you have a powerhead pointed upwards, the wave effect caused by the powerhead at the waters surface is more benifical then an airstone.
A powerhead pointed towards the surface is a better option the an airstoneas the actual bubbles from an airstone do little in the way of adding oxygen whilst in the water column. Instead, as stated, it is the extra surface area due to the rippling water which adds the bulk of oxygen.
So if you have a powerhead pointed upwards, the wave effect caused by the powerhead at the waters surface is more benifical then an airstone.
