chimney flow rate calculator

[brokencookie]

Re: chimney flow rate calculator

Ok,
Here is the calculator again, but this time with units that match.

[brokencookie]

Re: chimney flow rate calculator

, my flow rate is 1285.7.
Neill

Wow I think that's the highest flow rate we have seen. Is it fast enough to suck the toppings off your pizzas ? (might as well see if we can establish a maximum draw as well)

Bruce

[nissanneill]

Re: chimney flow rate calculator

My 40" Pompeii has an 8" steel flue 3metres high and again using the diameter dimensions in cm rather than the shown mm with the height in metres, my flow rate is 1285.7. My chimney also draws well with no smoke exiting the front arch.

Neill

[Frances]

Re: chimney flow rate calculator

Thats right! Chimney hight and diameter aren't the only factors.

My outer oven archway is higher than the inner one, and I think this causes air turbulence on the way out. Which means that the smoke comes out of the front of the oven as well as the chimney and probably also that the draw isn't as good as it could be.

But it makes it easier to get into the oven for cooking, so I'm not grumbling...

[wlively]

Re: chimney flow rate calculator

I have an 8 inch duravent 18 inches high above my custom poured vent transiton, which approx 8 inches high. Just using those numbers I get 684 if I read the comments about using cm istead of mm correctly.

My chimney draws well.

Although this baseline number does not include the effect a good transition has for increasing the velocity of the air flow.

[brokencookie]

Re: chimney flow rate calculator

Great, we have our first baseline number. 923 draws well. Anyone have a chimney with a lower numer that draws well ?

[christo]

Re: chimney flow rate calculator

I'm using 8x8 tile with a 8x14 inch transistion also made from tile
(design stolen with pride from DMUN)

I get a 923 - when I include the height of the transision plus the length of one tile.

My oven draws well. I have not had to clean any soot off of the front facing bricks ... knock wood.

Christo

[jengineer]

Re: chimney flow rate calculator

Ok I will take the bait but drop it off on a smoke and mirrors expert.

[gjbingham]

Re: chimney flow rate calculator

Scary stuff Bruce! Someone who really (really) understands music is as wierd as finding someone who understands cosmology (no, not cosmetology!). I don't even want to hear about the math. I get lost every time.

Somehow, I knew you were goofin' at work! I'm calling big oil!

[brokencookie]

Re: chimney flow rate calculator

Don't bait the engineer - he might get hooked

Sorry, I have a bunch of engineers where I work. I have the task of providing data to them and then listening to them tell me the data "must be wrong" since it did not match their models. I did not mean to step on toes.
I am serious about improving the spreadsheet though. If we can get good data that will help other builders then its all good. Besides, even engineers have to have a hobby. They must be the builders with 10 thermocouples built in. ( baiting intentional this time )


Bruce

[jengineer]

Re: chimney flow rate calculator

Don't bait the engineer - he might get hooked

[brokencookie]

Re: chimney flow rate calculator

Bruce,
I thought your degree was in music theory? My god man, what the heck is all this?? Are you goofing off at work??

George
Music theory is the science of music. Compostion is the art. My degree is music theory and compostion. I am the scientific artist That also makes me smarter than most musicians so I went out and got a job I could make a living at.
Yes, I am goofing off at work. I have my crew so well trained that they only need me for unusual things and some paperwork. I amuse myself by creating automated programing that further reduces my work load. Since I am management, I am not allowed to do real work, the union would have a tizzy.
So my job is to watch other people work, Find ways to reduce my own work, and stay out of trouble (like that's really going to work)

Bruce

[brokencookie]

Re: chimney flow rate calculator

mm = millimeters
cm = centimeters
conversion from C to K is C +273.15

You sure coefficient is correct? most chimney are more like the photo...The effective coefficient of discharge for flow nozzles in pipelines varies from 0.96 to 1.2 for turbulent flow and increases as the throat-to-pipe-diameter ratio increases. C in our systems will vary due to some folks using angle brackets and others making a smoother trend.

I knew I could find an engineer on the forum. I am just the guy who bubble gums these things together. Kind of a close enough approach for our purposes. I used 273 as the conversion to K and built it into the worksheet as most of the builders work in degrees C . I used 0.7 as the coefficient based on the information I had on hand. I figured that even if the modeling was not exact it could prove to be a useful preditive tool for oven builders. For example, I found that the difference between a 6 inch and an 8 inch round flue pipe is that an 8 inch has almost double the draw for the same height.
Please feel free to correct and repost. The worksheet was intended as a starting point, not a finished product.

Engineers !!!!

ON YOUR MARK

GET SET


CALCULATE !!!

[gjbingham]

Re: chimney flow rate calculator

Bruce,
I thought your degree was in music theory? My god man, what the heck is all this?? Are you goofing off at work??

[jengineer]

Re: chimney flow rate calculator

mm = millimeters
cm = centimeters
conversion from C to K is C +273.15

You sure coefficient is correct? most chimney are more like the photo...The effective coefficient of discharge for flow nozzles in pipelines varies from 0.96 to 1.2 for turbulent flow and increases as the throat-to-pipe-diameter ratio increases. C in our systems will vary due to some folks using angle brackets and others making a smoother trend.