[TheForge] a lot of unimpressive BS

Sat Jan 3 22:04:09 2004

Tom,
I just have to reply to this. Can't help my self. The hot air rises!!! If it
don't, the cold air could never get under it. A hot air balloon is a perfect
example. It is the hot air IN the balloon that causes it to go up. It goes
up because the heated air is less dense and the cold air can't get under it
until the hot air goes up. Even if there is no return air supply for a
chimney, there will still be some hot air that will escape out the top even
if some cold air has to come back down the chimney. It just won't work good
enough to make any difference.
If all the air in a given space is the same temperature, only heat or some
other mechanical means will cause air to move.
Darrell

http://www.machinemaster.com
----- Original Message ----- 
From: <[email protected]>
To: <[email protected]>
Sent: Saturday, January 03, 2004 6:29 PM
Subject: [TheForge] a lot of unimpressive BS

> on 1/3/04 7:10 PM,
> > From: Chris Worsley <[email protected]>
> > To: [email protected]
> > Subject: Re: [TheForge] hot air does not rise
> > Reply-To: [email protected]
> > The truth comes in simple words! Well said Dave, without a lot of
> > unimpressive BS ;-) .  Thanks.
> > Chris
>
> >> Details, details, details.  It still boils down to warm/hot air rises,
> >> cool air sinks.  Exhaust from a gas forge is warm/hot and will move
> >> upwards, not towards the floor.  The mechanism of the action is moot.
> >> It happens.  The CO and CO2 and the H2O and other byproducts of the
> >> propane forge combustion will rise.
> >>
> >> Dave Brown
> >> Heritage Smithing
> >> Green Bay, WI
>
>
> Dear Chris and Dave,
>
> My attempt at an explanation of the physics of gases was not meant to be a
> criticism of Dave, or his shop, only a simple clarification of a very
> commonly misunderstood phenomenon. Several times a year I have the
> opportunity to demonstrate physics to elementary school students, and they
> understand the difference right away. They go home and explain it to their
> parents.
>
> The reason that I bothered to comment in the first place was not merely to
> pontificate "a lot of unimpressive BS" but in the hope that the
information
> could be understood and utilized, apparently I was mistaken.
>
> I have visited many metalworking shops where a 6 foot diameter sheet metal
> hood was placed directly over a gas or coal forge, and vented straight up
> through a 10" dia pipe; and even though the forge directly below provided
an
> endless supply of "hot air", the hood failed to draw. The owners simply
> couldn't understand why the shop was still smoky. The same goes for
> fireplaces in modern houses.
>
> The inverse of this is the "side-draft" flue, where smoke and flames from
> the forge turn 90 degrees sideways before they go up the stack. I
sincerely
> hope that you never stumble upon one of these in action, it might confuse
> you.
>
> I almost always regret my postings to this list, and this is case is no
> exception. "Pearls before swine", and all that. I shall pester you no
more,
> and please accept my sincere apologies for my rude intrusion into your
> contented ignorance, 'twon't happen again.
>
> Tom Troszak
>
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