Gallery, Projects and General > The Design Shop

Why does smoke go faster up a taller chimney?

<< < (3/8) > >>

awemawson:
Hooray !!!!!

vtsteam:
Alternative theory:

A long glass tube under partial vacuum oriented vertically is suddenly opened at both ends. What happens, does the less dense contained air rise through the column?

No, air is sucked in at both ends.

It isn't only a density  problem, it is a pressure problem. The flow isn't driven more strongly by density differentials than pressure differentials.

So, back to the wood stove and chimney pipe working 6 feet away from me. The chimney is pressurized.

The woodstove is at higher pressure than the chimney top. This is the principle of the jet engine, not the hot air balloon.

Question to gun builders. Does increasing the length of a barrel, all other things being equal, increase the velocity of the bullet?

vtsteam:
probably more appropriately aimed at blowgun builders than gun builders -- a shell gets a momentary charge, not a continuous pressure.

Do longer blowguns have higher velocity? Seems obvious they would.

vtsteam:
So if the wood stove is a compressor and the stovepipe is an accelerator, shouldn't it work horizontally?

No. It is the density difference that gives the system direction. It's the bias.

A jet engine compressor is directional. a woodstove is bi-directional. A ramjet depends on forward movement to make it directional. A stove depends on initial density differences to make it directional. Otherwise the chimney would have higher resistance than the grate.

I think that's puzzle put together.

vtsteam:
Sorry about multiple posts -- i just keep thinking of more things, and it's snowing outside yet again and difficult to work on anything, and I'll have to go out and plow soon.

A vector is magnitude and direction. What I'm looking at in front of me, warming this house as it snows outside, is a woodstove generating a fair amount of pressure or force, an object, the smoke, accelerating with this force up the stovepipe, and a direction initiated by the difference in density of gasses.

And this is an analogue to how a jet engine works. Force mediated by a direction.

It also seems to be the principle of a monotube steam producer. The water pump not only provides feed water, but also must enforce direction. Otherwise a monotube with water in it would steam out of both ends. And in fact the water pump must provide higher pressure than the steam gage pressure to do that. In fact a diode in the form of an additional  clack valve is often used to absolutely maintain direction in  this circuit

Does the pressure of a jet engine compressor have to exceed the pressure in the combustion chamber when the engine is not moving forward and gaining ram effect?

And does the directional force of the difference in densities of hot and cold gasses do that in a chimney? Or is it the cooling gasses at the top of a chimney creating a partial vacuum there doing it?

Probably both.

A chimney once started working increases in directional power, through several mechanisms at once.

Navigation

[0] Message Index

[#] Next page

[*] Previous page