I'm going to sream...

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Buzzard, the reality is that when designing a flue the manufacturers/ installers have to allow for it to work under the worst possible conditions. In your example that would be on a still day with no wind, so you can ignore the effect of bernoulli's principle. It can't be taken into account.
 
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EddieM

just to add a bit of chemistry in here, carbon monoxide is slightly less dense than air.

as for the bernoulli principal, well there is plenty of lively debate as to whether fluid dynamics explains gaseous dynamics, but i don't pretend to understand it all :LOL:
 
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and just to add some more physics

the initial draught in the flue is due to the difference in atmospheric pressure, even on a still day there will be some air movement upwards , poujoulat do a good guide on pdf if you can find it.
 
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just to add a bit of chemistry in here, carbon monoxide is slightly less dense than air.

I dont think that was a good idea!

The amount of carbon monoxide in the flue gases will be minimal!

Tony
 
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EddieM

just to add a bit of chemistry in here, carbon monoxide is slightly less dense than air.

I dont think that was a good idea!

The amount of carbon monoxide in the flue gases will be minimal!

Tony


hopefully, none. At the combustible temperatures, all of the flue gasses should be a lot less dense than ambient air, obviously a flues job is to exhaust these gases before they cool to ambient temperatures, when CO2 for instance is denser than air.
 
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EddieM

just to add a bit of chemistry in here, carbon monoxide is slightly less dense than air.

I dont think that was a good idea!

The amount of carbon monoxide in the flue gases will be minimal!

Tony


hopefully, none. At the combustible temperatures, all of the flue gasses should be a lot less dense than ambient air, obviously a flues job is to exhaust these gases before they cool to ambient temperatures, when CO2 for instance is denser than air.

And of course CO is only slightly less dense than air and a damned sight more toxic, resulting as we all know in the preferrential and non reversable binding to haemaglobin to form carb-oxy haemaglogin rather than the reverible formation of oxy haemaglobin, which is how all animals get the oxygen they need. Nasty stuff.
 
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Buzzard, the reality is that when designing a flue the manufacturers/ installers have to allow for it to work under the worst possible conditions. In your example that would be on a still day with no wind, so you can ignore the effect of bernoulli's principle. It can't be taken into account.

Hum, not sure. I suspect that the worst case scenario will be when there is a slight breeze as this disrupt the rising of the hot gases, but there would be much Bernoulli principle to compensate.

However this is all irrelevant to the original question, because I am sure that a minimum flue gas velocity could be required for certain fire designs and hence the possible requirement for having the flue lined.
 

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