Now That's Some Wind!

Post by **Lightning** » Fri. Dec. 21, 2012 12:29 pm

Doc Brown rocks!!!

lsayre · Post by **lsayre** » Fri. Dec. 21, 2012 2:57 pm

Apparently styrene balls work well to show wind induced chimney draft:

http://www.physics.usyd.edu.au/super/physics_tut/ ... Effect.pdf

lsayre · Post by **lsayre** » Fri. Dec. 21, 2012 3:03 pm

This goes so fast it's a bit hard to see (that plus the resolution quality is lousy), but this guy raises an egg out of a cup simply by blowing over the cup. A ping-pong ball up a tube should be easy.

Sting · Post by **Sting** » Fri. Dec. 21, 2012 3:32 pm

I would like to make one final comment on this drama:

AS I posted earlier today - my edumakation does not hold a candle to the lucid engineers that lurk here
BUT
I submit - you all need to get your HEAD OUT OF the chimney and back in the boiler room

It doesn't make any difference how good the chimney is occasionally performing when it is doing so above expectation - it is however VERY important that it does perform well enough in all climates and events.

and "well enough" is all it takes to put a draw on the smoke pipe [ connecting the appliance to the chimney] in the area of the correctly installed Barometric damper - These examples posted about balls or a satchel of man parts; have NO relationship to real world smoke. The are based on the assumption of infinite air movement on both ends and are being performed in a lab environment.

On your appliance - this is not the case at all -YOUR NOT IN A LABORATORY - your air movement potential is LIMITED by the size and condition of the smoke pipe and when the correctly installed Barometric damper is wide open - it [ the baro] will pass the CFM required to fill the smoke pipe it is attached to and drop the atmospheric pressure [at that point in the pipe] to pascal value you have it set to.

UNLESS

There ISN"T enough Volume at atmospheric pressure in the boiler room to feed it - IN THAT INSTANCE - now think :>0 -- where is the MANOMETER taking its samples from??????

IT AINT THE CHIMNEY - its the appliance vs the room

The boiler that is in a room [apparently in you example above] is under negative atmospheric pressure and the manometer is registering TOO much draw - ON THE APPLIANCE

--WHY???? because there isn't enough make up air to offset the over functioning chimney and the baro is trying to keep up but your choking it by not giving it what it wants -- AIR

- [ back to justification] ONLY a fixed amount of air or volume or CFM will pass in a specific smoke pipe because thats the size of the pipe -- just like only a specific amount of heat energy can be moved in a fault tolerant manor in a wet heating system ----> if we are moving too much water we change the pump

if the chimney is working too well ---- fix the chimney

a second hole [barometric or mechanical or transcontinental intergalactic] in the smoke pipe will not solve the issue that the appliance is operating in the wrong environment!

and with that let me just add

IT Depends!

Kind Regards
Sting

freetown fred · Post by **freetown fred** » Fri. Dec. 21, 2012 4:24 pm

you da man sting----OR, if in my personal situation with my hand fired Hitzer 50-93 you have a MPD that has worked well for 4 seasons through thick & thin--styrofoam/ ping-pong balls????--oh MY achin BALLS--like stated if things aren't working right get a mano/baro--I have neither cause the stove Gods must like me--but if I needed to do it properly, I would get what was realistically suggested, not some black magic/voo-doo from a bunch of frustrated chemist/engineer/sooth-sayor-( not directed at anyone personal)-were talking coal burning devices here--not minu'te particle physics

SteveZee · Post by **SteveZee** » Fri. Dec. 21, 2012 5:18 pm

Hey all I'll add is "keep your dampers closed"

Matter of fact the wind is howling out there as I type on the old Maine coast. Lotta wuthering going on round the Gables.

Post by **Lightning** » Fri. Dec. 21, 2012 5:54 pm

Geez, you old school fellas are a tough crowd

:surrender: I'd rather not challenge Sting's theory of the low pressure in the boiler room to keep a friendly demeanor here, so back to the wind hitting the chimney thing

..... Instead of sketching up some diagrams, I found this information about wind effect on Chimneys online -

When the wind blows horizontally, the air which is compressed at A flows up over the edge of the chimney and follows the path of the arrows a and b. This current deflects the wind somewhat, as shown by the arrows c and d, and lifts it above the leeward edge of the chimney. An opportunity is thus given for the chimney gases (which are shown by feathered arrows) to pass over the edge of the chimney into the area of low pressure at B. As the velocity of the wind increases, the pressure at B becomes less, and the chimney draft is augmented correspondingly.

.JPG | 4.6KB | Effects-Of-Wind-Upon-Chimneys-123.jpg

But, if the wind blows downwards, the escape of the chimney gases is cut off, and, unless there is sufficient pressure behind them to deflect or lift the wind at the mouth of the chimney, a back draft, or blow-down, will be produced. (Trees that canopy up over part of the roof or that are close but upwind may cause a downward airflow towards the chimney. A chimney top lower than peak of the roof would have this problem too. Where's Berlin????

)

.JPG | 4KB | Effects-Of-Wind-Upon-Chimneys-124.jpg

The beneficial effect of the ordinary horizontal winds upon the draft of a chimney may be increased by means of the circular deflector C. That part of the wind which is intercepted by the curved surface of C is deflected strongly upwards and operates to lift the main current of wind well above the top of the chimney. Thus, the chimney gases are given a good opportunity to escape over the leeward edge, as indicated by the arrows. (This example demonstrates the airfoil similarity I stated earlier.)

.JPG | 3.5KB | Effects-Of-Wind-Upon-Chimneys-125.jpg

Post by **Rob R.** » Fri. Dec. 21, 2012 10:03 pm

After reading all of this fancy talk about how draft can be affected by wind, chimney pitch, and the phase of the moon...I decided to go brush any flyash out of my baro and make sure everything is in good working order. This is the forecast for us tomorrow night:

Mostly cloudy with a chance of snow. Low of 10F with a windchill as low as 0F. Breezy. Winds from the WNW at 15 to 25 mph with gusts to 30 mph. Chance of snow 40% with accumulations up to 1 in. possible.

10 degrees with 25 MPH NW winds is a recipe for serious coal consumption.

Post by **Lightning** » Sat. Dec. 22, 2012 7:30 am

Fancy talk lol, yeah yeah - I admit I'm a nerdy science guy but other than saving $2000 on energy bills this winter, thats what makes burning coal fun and exciting for me

... To me my furnace is a science project and its fun to observe its reactions to changing conditions. I also enjoy the challenges of the problem solving that goes along with it by analyzing whats going on and why

I'll be careful not to burn the house down or blow the flue pipe off it..

Cold, snowing and heavy wind here in Olean NY this morning. I need to go after the baro door with my tooth brush too lol

Merry Christmas

Post by **Rob R.** » Sat. Dec. 22, 2012 7:35 am

It is really windy here right now, I burned about 50 lbs since 7 pm last night.

SteveZee · Post by **SteveZee** » Sat. Dec. 22, 2012 7:38 am

Rob R. wrote:After reading all of this fancy talk about how draft can be affected by wind, chimney pitch, and the phase of the moon...I decided to go brush any flyash out of my baro and make sure everything is in good working order. This is the forecast for us tomorrow night:

Mostly cloudy with a chance of snow. Low of 10F with a windchill as low as 0F. Breezy. Winds from the WNW at 15 to 25 mph with gusts to 30 mph. Chance of snow 40% with accumulations up to 1 in. possible.

10 degrees with 25 MPH NW winds is a recipe for serious coal consumption.

We had it last night. Howling winds in the 40s but relatively warm air also 40s. Prolly the back side of that front is the cold air filling in? Nearly sucked the cookstove out. I usually get up at 3-4am and add a scoop or two to the cookstove when its real cold or really windy but slept through and although it looked good, it was mostly "ecto-skel" coal pieces when I went to fill and shake it at 7am! Big stove sized coal skel's of ash.

Boots · Post by **Boots** » Sat. Dec. 22, 2012 8:29 am

Not that I want in on the "argument" but I have not seen this posted yet,

the effect of wind blowing across the top of something (be it a straw with liquid, or a chimney with smoke we will call it a "tube" because I want to call it that.) and causing a draft is called the "venturi effect" by blowing across the top of the "tube" it creates an area of low pressure inside of the tube. And this low pressure area will be filled by whatever's on the other end of the tube. If you own any piece of equipment with a small engine, think lawn mower, the carburetor more than likely operates with the venturi effect. the more CFM of air that passes through the throat of the carb, the more fuel that gets pulled from the bowl and consumed by the engine. when you set the throttle on a small engine all you are controlling is a valve, just like a MPD. and depending on the positioning of this valve to allow more or less air flow, you get higher or lower RPM' s.

Now that being said, I did not post that in an effort to appose Stings science. I understand his point, I think. You cant get blood from a turnip. if there is not enough air in the boiler room having a second barro will do nothing but make a$50 bill disappear.

freetown fred · Post by **freetown fred** » Sat. Dec. 22, 2012 8:31 am

venturi??? wasn't he the Gov out in Minn or somewhere???

KLook · Post by **KLook** » Sat. Dec. 22, 2012 8:49 am

The analogy for the MPD being the butterfly valve in an engine is good. And it points out that the engine floods out if the supply jet (fumes from burning coal) is to big for the reduced air opening to handle, Think choking and how gas flies back out of the carb. This is why some don't like MPD's as it requires a consistent pull to be in the right position or constant monitoring. Hence the Barometric. Let the arguments begin!!

Kevin

freetown fred · Post by **freetown fred** » Sat. Dec. 22, 2012 9:58 am

w I have an ideal situation Kevin, & I'm real lucky with my chimney set up. When it's warmer out, I set my MPD at 3/4 & don't touch it even for tending & when it gets to actually be winter, I close it all the way& don't touch it till spring. Like I said, my situation is ideal right here wide open on the top of this hill.