[TheForge] hot air does not rise

[info@reciprodyne.com]

on 1/3/04 12:39 PM,
> Subject: Re: [TheForge] vent hood

> The hot gasses rise, the are heavier than air when cold or at room
> temp.  But when as hot as they are when they exit the forge they rise until
> they cool down to room temp.
> 
> Dave Brown
> Heritage Smithing
> Green Bay, WI


Dear Dave,

I hate to start WW-3 but: hot gasses do not rise, they must be displaced
(via gravity) by cooler gasses in order for convection to take place. Hot
air does not have anti-gravity properties, but is can be displaced "upwards"
by cooler air which is denser, and therefore "heavier".

Hot-air balloons, blimps, etc, are all powered by gravity acting upon the
cooler or denser gasses (outside the envelope) upon which these hotter or
less dense gasses (inside the envelope) float, like a ship on water.

A closed room with a chimney must have a fresh air inlet (preferably low) in
order for the chimney to work properly. The greater the differential in
temp. (or density) between the flue gasses and the makeup air, the greater
the potential draft, but with no makeup, no draft.

Tom Troszak