# Air Volume for HVAC and Mathematicians



## tapehoser (Sep 10, 2007)

OK....this is for both HVAC folks and mathematicians.

Let's say I have a cylinder...like your furnace/AC vent pipe. Said pipe has a specific volume of air that will pass through it, right? To figure the volume of a cylinder I use this: 

Volume = length x (pie) 3.14 x radius squared. If it's a 6" length of pipe with a 2" radius, you get 75.36 inches cubed as the answer.

Let's say I squish the cylinder a little so that it makes itself into more of an oval shape? I haven't changed the surface area of the cylinder...just the shape.

Has the volume of air that the pipe can hold changed at all?

Discuss.


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## DallanC (Jan 13, 2009)

tapehoser said:


> OK....this is for both HVAC folks and mathematicians.
> 
> Let's say I have a cylinder...like your furnace/AC vent pipe. Said pipe has a specific volume of air that will pass through it, right? To figure the volume of a cylinder I use this:
> 
> ...


Of course... if you keep squishing it until its flat it will hold 0 air. Maximum volume = perfect circle, flattening along an axis will reduce the volume.

Lets all remember calculus... slice, approximate, integrate.

-DallanC


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## Huge29 (Sep 17, 2007)

I couldn't prove it mathematically, but that seems logical to me.


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## KineKilla (Jan 28, 2011)

I'm thinking no. 

What would happen though is that you would likely increase velocity (LFM) but the CFM (Volume) would remain fairly unchanged. Up to a point of course...once you deform it enough you would definitely begin to lose the efficiency of the circle shape, and create turbulence which would in turn affect CFM and Velocity.


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## Huntoholic (Sep 17, 2008)

Yes it has changed.


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## wyogoob (Sep 7, 2007)

tapehoser said:


> OK....this is for both HVAC folks and mathematicians.
> 
> Let's say I have a cylinder...like your furnace/AC vent pipe. Said pipe has a specific volume of air that will pass through it, right? To figure the volume of a cylinder I use this:
> 
> ...


That depends how you look at it. My guess is you have some argument going on. Can you be more specific?

I understand what you are getting at but to answer your question: Has the volume of air that the pipe can hold changed at all? answer is "no", in a closed system.

Generally if you squish a closed cylinder it doesn't change the volume. It will hold the same volume when I squish it with both hands, but the soda is at a higher pressure. If you are talking about flow it's a little different.

Take a 12 oz can of pop for example. I have one in my hand. I can squish it quite a bit, and it still holds 12 oz (volume) but at a greater pressure. Open the squished pop can (be careful) and pour out the contents. Now you can't put 12 oz back in the can. So it depends what your argument is; open or closed system.


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## Huntoholic (Sep 17, 2008)

wyogoob said:


> ......Take a 12 oz can of pop for example. I have one in my hand. I can squish it quite a bit, and it still holds 12 oz (volume) but at a greater pressure. Open the squished pop can (be careful) and pour out the contents. Now you can't put 12 oz back in the can. So it depends what your argument is; open or closed system.


Can I stand back and watch you squish it quite a bit?


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## wyogoob (Sep 7, 2007)

Huntoholic said:


> Can I stand back and watch you squish it quite a bit?


ah, ha, ha, ho, ho, hee, hee

Get a rain suit on man. I drink Kroger sparkling seltzer water; no sugar, doesn't make a mess.

Hey, don't make me get a video camera out. 

.


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## DallanC (Jan 13, 2009)

wyogoob said:


> Generally if you squish a closed cylinder it doesn't change the volume. It will hold the same volume when I squish it with both hands, but the soda is at a higher pressure. If you are talking about flow it's a little different.


I understand what you are saying here, but volume is defined and measured in squared units of length. Specifically:

volume = (PI * major_axis_height * minor_axis_width * length) / 4

If I completely flatten a cylinder, I can reduce its internal volume to 0. You are mixing Boyles law into this which states as as volume decreases pressure increases. It is a valid point, but moot in the case of the OP because in Boyles law, the key point is volume is DECREASING as pressure rises.

Decreasing volume is what he asked about.

And back to the OP: play around with this:

http://www.onlineconversion.com/object_volume_elliptical_tank.htm

-DallanC


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## wyogoob (Sep 7, 2007)

DallanC said:


> I understand what you are saying here, but volume is defined and measured in squared units of length. Specifically:
> 
> volume = (PI * major_axis_height * minor_axis_width * length) / 4
> 
> ...


I was waiting for you. If you "completely" flatten a closed cylinder without the air escaping the same volume of air still is in the cylinder but at very high pressure. You can't completely flatten it. It will have a void for the air, or what ever was in it.

When my Scott Air Pact breathing air cylinder goes flat I put more volume in it, more cu ft of air in it, and the pressure goes up. But that is looking at the volume of the product not the volume of the cylinder. We're kinda comparing two different things. Boyles is like when a piston goes down a clylinder and changes the volume of the cylinder. The volume of the product in the cylinder is the same if the cylinder is closed.

OK then, let's un-moot. I don't think the OP is talking about completely flattening the pipe. Lets take air flow thru a ductwork. I think it's what the OP is talking about.

A fan puts out 80 CFM (volume) of air thru 20 foot of 8" duct. Change the duct to 4" and the duct still puts out 80 CFM (volume) of air.

http://www.calculatoredge.com/optical%20engg/air%20flow.htm

I've been through this air-flow discusion at work often and I'm sure sooner or later we will argumentively flatten the duct so much that the operating parameters of the fan will change, and we will be at moot point again. :?

.


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## brookieguy1 (Oct 14, 2008)

wyogoob said:


> That depends how you look at it. My guess is you have some argument going on. Can you be more specific?
> 
> I understand what you are getting at but to answer your question: Has the volume of air that the pipe can hold changed at all? answer is "no", in a closed system.
> 
> ...


Maybe. It's kind of confusing. That is why hydraulics is such a strong system. If there were zero airspace in the can, you could not collapse it much at all without stretching the metal or blowing the seams.
As far as air in ductwork goes, the flatter you get beyound square or round the higher the static pressure. In other words, you may get the same amount of air down the flatter duct but it will be going faster and need a stronger fan to push it. That's where you get into duct sizing, fan curves and cooeffecients.


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## wyogoob (Sep 7, 2007)

brookieguy1 said:


> Maybe. It's kind of confusing. That is why hydraulics is such a strong system. If there were zero airspace in the can, you could not collapse it much at all without stretching the metal or blowing the seams.
> As far as air in ductwork goes, the flatter you get beyound square or round the higher the static pressure. In other words, you may get the same amount of air down the flatter duct but it will be going faster and need a stronger fan to push it. That's where you get into duct sizing, fan curves and cooeffecients.


In my example I was assuming the cylinder would not yeild. Smash the duct diameter by 50% and the flow will be basically the same, the velocity will change. Now there is a point when constricting the flow that the fan, or pump or whatever driver loses effeciency and won't put out the volume anymore because there's little pressure differential and/or flow differential accross the fan. *Like I said before* this argument always ends up at whatever is supplying the product; pump, fan, flow controller or pressure regulator, whatever.

Another flow example:
A 5500 hp natural gas compressor at a plant above Evanston pumps 90 mmcf of gas The discharge line is 24" for 200 feet. The gas goes thru a 20" orifice at a meter. There's still 90 mmcf/day going thru the 20" hole, its just going faster and there's a pressure drop across the orifice. The pipe is still 24" pipe is for another 5 miles and there's still the same volume of gas, 90 mmcf going thru the line 5 miles later. Then the 24" pipe changes to 36" and goes 80 miles to Green River Wyoming. At that point there's still 90 mmcf/day of volume going thru the pipeline.


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## brookieguy1 (Oct 14, 2008)

tapehoser said:


> OK....this is for both HVAC folks and mathematicians.
> 
> Let's say I have a cylinder...like your furnace/AC vent pipe. Said pipe has a specific volume of air that will pass through it, right? To figure the volume of a cylinder I use this:
> 
> ...


It definately changes.
Let's make it square to simplify. A 10" x 10 " square duct is 100 square inches. Flatten it down to 1"deep. You would need a 100" x 1" duct to equal the same volume. 200"X.5", and so on infinately. Quite a bit more surface area!
It doesn't matter how little you "squish" it, it lessens the volume. Say you squish it 2". Now widen it 2". That's 12 x 8. Now it's only 96 square inches. The further you flatten it, the more you need to widen it, thus increasing surface area. It works the same with round or square.


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## wyogoob (Sep 7, 2007)

This is the OP's question:

_Has the volume of air that the pipe can hold changed at all?_

Yes, the capacity of the pipe is smaller if you squish it. That's not the question.


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## brookieguy1 (Oct 14, 2008)

wyogoob said:


> This is the OP's question:
> 
> _Has the volume of air that the pipe can hold changed at all?_
> 
> Yes, the capacity of the pipe is smaller if you squish it. That's not the question.


Oh, I guess I understand. But the only way the volume can stay the same after squishing it is for the pressure to increase. The OP needs to clarify exactly what he meant, but I feel he meant at no increased pressure.
Or, he was trying to trick us with the "surface area" idea.
OP: Please clarify. Don't leave us danglin'.


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## brookieguy1 (Oct 14, 2008)

I still feel I'm right. (Naturally). Since the pressure has to go up for the flattened cylinder to hold the same volume, the round cylinder would still hold more at the same pressure as the flattened cylinder. 
It's undisputable.8)


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## wyogoob (Sep 7, 2007)

brookieguy1 said:


> I still feel I'm right. (Naturally). Since the pressure has to go up for the flattened cylinder to hold the same volume, the round cylinder would still hold more at the same pressure as the flattened cylinder.
> It's undisputable.8)


No

You have pipe mixed up with the space between your ears.

Thank God you don't work at a compressor station; they would make you pee in a cup. :?

.


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## wyogoob (Sep 7, 2007)

Geeze I hate going Google but see Boyle's Law:
http://en.wikipedia.org/wiki/Boyle's_law

In the piston animation the volume of the cylinder (blue) gets smaller but the amount of the gas (yellow) in the cylinder stays the same, just like my original post where I gave the example of squeezing a can of soda.

.


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## sawsman (Sep 13, 2007)

wyogoob said:


> No
> 
> You have pipe mixed up with the space between your ears.
> 
> ...


:lol:

Sounds like I'm at work&#8230; The Engineer vs the Union guy.

This will be a good topic of discussion when goob takes us on that trip to the Wind River range.

I'll bring the full cans of soda for demonstration purposes.


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## wyogoob (Sep 7, 2007)

sawsman said:


> :lol:
> 
> Sounds like I'm at work&#8230; The Engineer vs the Union guy.
> 
> ...


 I have a new lightweight sleeping bag and a fancy-dancy compression bag thingie that squeezes the bag down to nothing. So, the more I squeeze it down the lighter it weighs. Can you carry it for me?

Uh...I have had lots of pressure-related discussions with Engineers where you work.

.


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## sawsman (Sep 13, 2007)

I'll carry the poles and soda and Brookieguy can carry your bag so he understands what your talking about..;-)

Uh, some of those guys at work have a lot of air between their ears. Dont let them fool you.


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## brookieguy1 (Oct 14, 2008)

wyogoob said:


> Geeze I hate going Google but see Boyle's Law:
> http://en.wikipedia.org/wiki/Boyle's_law
> 
> In the piston animation the volume of the cylinder (blue) gets smaller but the amount of the gas (yellow) in the cylinder stays the same, just like my original post where I gave the example of squeezing a can of soda.
> ...


Ok you've proven that point, and perhaps this is mute,but how much more energy does it take to push said piston under higher pressures with less volume? Is the energy allowed under this theory infinate? 
P.S., do the Ford engines have oval cylinders kind of like their blue logo?:grin:


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## brookieguy1 (Oct 14, 2008)

sawsman said:


> :lol:
> 
> Sounds like I'm at work&#8230; The Engineer vs the Union guy.
> 
> ...


I know. We Union engineers are a stubborn bunch;-)


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## brookieguy1 (Oct 14, 2008)

Wow. A bell just rang in my feeble little brain.
It doesn't matter what shape the cylinder is. The piston changes the size either way! Took me a while, but I see your point.
BUT.....it still depends on the OP's intent. Did he mean what volume the pipe will hold under normal (atmospheric) or mechanically enhanced pressures. I realize these things were probably brought up earlier, I just catch on at my own pace, which is a tad slow....:|


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## wyogoob (Sep 7, 2007)

brookieguy1 said:


> Ok you've proven that point, and perhaps this is mute,but how much more energy does it take to push said piston under higher pressures with less volume? Is the energy allowed under this theory infinate?
> *Single stage, multi-stage, reciprocal, or direct displacement pumps? With or without unloaders?*
> 
> P.S., do the Ford engines have oval cylinders kind of like their blue logo?
> ...


.....................................


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## wyogoob (Sep 7, 2007)

sawsman said:


> :lol:
> 
> Sounds like I'm at work&#8230; The Engineer vs the Union guy.
> 
> ...


You better hurry, backpacking is not as appealing to me as it was awhile ago.

If we do the Golden Trout thingie you have to do the Neuralizer when we come out:



.


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## sawsman (Sep 13, 2007)

So now you have me wondering….. maybe we've already been there and I dont remember. :sad:


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## tapehoser (Sep 10, 2007)

tapehoser said:


> Let's say I have a cylinder...like your furnace/AC vent pipe. Said pipe has a specific volume of air that will pass through it, right? To figure the volume of a cylinder I use this:
> 
> Volume = length x (pie) 3.14 x radius squared. If it's a 6" length of pipe with a 2" radius, you get 75.36 inches cubed as the answer.
> 
> ...


I am not sure how much clearer I can state my case. This is in relation to a cold air supply for a utility room in my home. Years back, the inspector tried to ding me on an inspection. The pipe was very large and over-filled the entire area between two floor joists. The builder placed metal supports between joists at certain intervals. When the HVAC guy was installing the cold air supply, that big metal tube didn't fit perfectly into the area between the joists because of that metal bar, so he bent the tube slightly so it would fit. My argument was that even if it did restrict the flow of air, however slight, it was not enough to be concerned with.

I won the argument that day because I told him unless he could prove to me that it reduced the flow of air to unacceptable levels, he'd have to pass me on the inspection. :grin:

Need more info?


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## wyogoob (Sep 7, 2007)

tapehoser said:


> I am not sure how much clearer I can state my case. This is in relation to a cold air supply for a utility room in my home. Years back, the inspector tried to ding me on an inspection. The pipe was very large and over-filled the entire area between two floor joists. The builder placed metal supports between joists at certain intervals. When the HVAC guy was installing the cold air supply, that big metal tube didn't fit perfectly into the area between the joists because of that metal bar, so he bent the tube slightly so it would fit. My argument was that even if it did restrict the flow of air, however slight, it was not enough to be concerned with.
> 
> I won the argument that day because I told him unless he could prove to me that it reduced the flow of air to unacceptable levels, he'd have to pass me on the inspection. :grin:
> 
> Need more info?


I don't need more info now. To answer your original question (again) the volume of the air did not change. It just went thru the bent part faster.

.


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## Huntoholic (Sep 17, 2008)

I think it depends on whether you are talking cold air return duct or outside cold combustion air. If he is talking about combustion air, he may not have the pressure to give up if there is a bunch of the necked down areas and the pipe is long to the room.


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## wyogoob (Sep 7, 2007)

Huntoholic said:


> I think it depends on whether you are talking cold air return duct or outside cold combustion air. If he is talking about combustion air, he may not have the pressure to give up if there is a bunch of the necked down areas and the pipe is long to the room.


I see what you're getting at but I would say it doesn't make any difference. Combustion needs a minimum volume, pressure can fluctuate a lot. Combustion air can run at a vacuum or be pressured up. Ducts can have flow controllers, venturis, and orifices that purposely constrict, or even enlarge, the duct size to purposely change the flow.

I've intentionally left this out of the conversation but there are some rules of thumb for constrictions for pipes, tubes, hoses, and all manner of ducts. And there's something in the Unified Building Code (UBC) covering his, and your, examples. I have parts of the UBC, but not all of it. I just finished a job as a mechanical inspector and I was over all ductwork from huge 15-footers to small 6" ducts that fell under the UBC.

.


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## brookieguy1 (Oct 14, 2008)

True stuff Goob. There are certain rules we use when constricting ducts. We call them duct-slices, or beam-dodgers. In the OP's case, it was the joist braces. Generally, you can reduce the heigth of the duct WITHOUT widening it for a short distance as long as you regain that heigth in a short distance. (Right after clearing the beam or obstruction.) The angles on the sides of the duct to create the heigth reduction should not be greater than 15 degrees, on both the upstream and downstream sides.
Clear as mud?
When the OP originally posted his question, I assumed he meant the entire duct was being constricted, not just certain short distances.


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## Huntoholic (Sep 17, 2008)

So you are telling me if I have an inlet pipe that goes into an enclosed room, except for a burner and vent pipe, that if I plug the vent pipe the volume of air going down the inlet pipe is the same whether the vent pipe is plugged or not?


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## Joefox (Jan 29, 2014)

Interesting stuff. Just replaced my condenser but my knowledge is limited on HVAC.. and math. =P


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## wyogoob (Sep 7, 2007)

Huntoholic said:


> So you are telling me if I have an inlet pipe that goes into an enclosed room, except for a burner and vent pipe, that if I plug the vent pipe the volume of air going down the inlet pipe is the same whether the vent pipe is plugged or not?


No, that's not what I'm saying....and define "plug" and "inlet" pipe. What side of the burner is the inlet pipe on?

Take a normal household furnace. It has a filter in the inlet duct. Take the filter out and everything works OK. Put the filter in and it stops some of the flow but all is OK. The filter gets all plugged up like no body's business and it's still OK.

Hey, a camper is different though.

more later


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## wyogoob (Sep 7, 2007)

brookieguy1 said:


> True stuff Goob. There are certain rules we use when constricting ducts. We call them duct-slices, or beam-dodgers. In the OP's case, it was the joist braces. Generally, you can reduce the heigth of the duct WITHOUT widening it for a short distance as long as you regain that heigth in a short distance. (Right after clearing the beam or obstruction.) The angles on the sides of the duct to create the heigth reduction should not be greater than 15 degrees, on both the upstream and downstream sides.
> Clear as mud?
> When the OP originally posted his question, I assumed he meant the entire duct was being constricted, not just certain short distances.


yep
yes
I concur
it's clear


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## Huntoholic (Sep 17, 2008)

wyogoob said:


> No, that's not what I'm saying....and define "plug" and "inlet" pipe. What side of the burner is the inlet pipe on?
> 
> Take a normal household furnace. It has a filter in the inlet duct. Take the filter out and everything works OK. Put the filter in and it stops some of the flow but all is OK. The filter gets all plugged up like no body's business and it's still OK.
> 
> ...


The filter on a household furnace is in the cold air return duct. This air is being moved by the blower in the furnace. Hence it has enough suction (mechanically moved air) pressure in the pipe to over come any plugged line or restrictions as you have described. Combustion air comes into the room through an outside duct or pipe into an open room. The burner uses the required O2 and vents the combustion gas out the vent pipe. This relies on draft air (convection) for air movement. Very low pressure drop across the room (air not mechanical moved). In the case of combustion air for a home furnace, in a tightly seal utility room, pressure drop is more important. In theory if the inlet pipe where long enough, there was to many restrictions (i.e. line losses), if the vent duct was way undersized, or if you plugged off the vent from the burner you would have very low air movement or no air movement into the room through the outside inlet duct. Different air volume moving into the room.


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## brookieguy1 (Oct 14, 2008)

Huntoholic said:


> The filter on a household furnace is in the cold air return duct. This air is being moved by the blower in the furnace. Hence it has enough suction (mechanically moved air) pressure in the pipe to over come any plugged line or restrictions as you have described. Combustion air comes into the room through an outside duct or pipe into an open room. The burner uses the required O2 and vents the combustion gas out the vent pipe. This relies on draft air (convection) for air movement. Very low pressure drop across the room (air not mechanical moved). In the case of combustion air for a home furnace, in a tightly seal utility room, pressure drop is more important. In theory if the inlet pipe where long enough, there was to many restrictions (i.e. line losses), if the vent duct was way undersized, or if you plugged off the vent from the burner you would have very low air movement or no air movement into the room through the outside inlet duct. Different air volume moving into the room.


Hey Huntoholic, you're obviously a residential HVAC guy. I need a side job or 6. Can you help me? I need tackle money! My sheetmetal work is impeccable.


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## wyogoob (Sep 7, 2007)

Huntoholic said:


> The filter on a household furnace is in the cold air return duct. Yes, on the suction side of the furnace. This air is being moved by the blower in the furnace. Hence it has enough suction (mechanically moved air) pressure in the pipe to over come any plugged line or restrictions as you have described. Combustion air comes into the room through an outside duct or pipe into an open room. The burner uses the required O2 and vents the combustion gas out the vent pipe. This relies on draft air (convection) for air movement. Very low pressure drop across the room (air not mechanical moved). In the case of combustion air for a home furnace, in a tightly seal utility room, pressure drop is more important. I can't thank you enough for the tutorial. In theory if the inlet pipe where long enough, there was to many restrictions (i.e. line losses), if the vent duct was way undersized, or if you plugged off the vent from the burner you would have very low air movement or no air movement into the room through the outside inlet duct. I didn't know we went from from talking about the air ducts to talking about the furnace exhaust. Different air volume moving into the room.


This is going to end up at the burner, just like I said back on page 1.


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## brookieguy1 (Oct 14, 2008)

Goob, you're a book of knowledge. And soooo patronizing. And I love ya!


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## wyogoob (Sep 7, 2007)

brookieguy1 said:


> Goob, you're a book of knowledge. And soooo patronizing. And I love ya!


I'll patronize ya...

Anyway, geeze I coulda got you on our project over in Rock Springs.

You probably wouldn't have liked working over here though; there are *NO* fish in Wyoming.

.


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## brookieguy1 (Oct 14, 2008)

wyogoob said:


> I'll patronize ya...
> 
> Anyway, geeze I coulda got you on our project over in Rock Springs.
> 
> ...


But, Goob, even though there are no fish in Wyo, I would love to work on a project around you! PLEASE don't forget about me. I'm always looking for new opportunities, whether Union or Company. You know me. Flexxiibblle.


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## wyogoob (Sep 7, 2007)

brookieguy1 said:


> But, Goob, even though there are no fish in Wyo, I would love to work on a project around you! PLEASE don't forget about me. I'm always looking for new opportunities, whether Union or Company. You know me. Flexxiibblle.


Cool. I work for the owners normally, 3rd party. We're open shop in Wyoming; jobs can be both union and non-union. I love everybody. 

OK, OK, say there's 1 cubic mile of hot dirty air in Salt Lake between I80 and Mill Creek Canyon and Emigration Canyon. Then it all goes up Parleys Cany......never mind. :smile:

.


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## Huntoholic (Sep 17, 2008)

Well then let's go back to the original question.

"Has the volume of air that the pipe can hold changed at all?"

Yes it has.

This is verified by "Goob's" example of the soda can. When I push in the sides of the can the area of the can changes. This is validated, because area of the gas is greater then the area of the can, so the pressure goes up.

Or another way, you are putting 10 lbs of crap in a 5 lbs bucket.


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## wyogoob (Sep 7, 2007)

That doesn't make any sense given they way the question was presented.

OK, I squished the can and made it smaller. Doing so I raised the pressure. There was 12 oz of pop in the can before I made it smaller and 12 oz of pop after I made it smaller. Same volume, smaller area.

Check the animation here: http://en.wikipedia.org/wiki/Boyle's_law They squish the cylinder but the volumn doesn't change.

Yer killin' me. Lets have lunch. You bring brookieguy1, I'll bring a 6-pack of soda.

.


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## Huntoholic (Sep 17, 2008)

I wish I would have saw your comment before I went to lunch.....

Volume is 3 dimensional and Area is 2 dimensional.

Volume of a cylinder (assuming flat ends) = (pi)(r(sq))(h)

Change the height (h) = volume change of the cylinder.

Also look at the link that you provided and you will see on the right side, the cylinder volume goes from 4 to 2.


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## wyogoob (Sep 7, 2007)

Huntoholic said:


> I wish I would have saw your comment before I went to lunch.....
> 
> Volume is 3 dimensional and Area is 2 dimensional.
> 
> ...


Yeah, I said this before. We are talking about 2 different things. The question the OP asked specifically concerned volumn.

.


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## Huntoholic (Sep 17, 2008)

How was your lunch?


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## wyogoob (Sep 7, 2007)

Huntoholic said:


> How was your lunch?


Good, 4 cups of strong coffee and a Snickers candy bar. :grin:

.


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## brookieguy1 (Oct 14, 2008)

Huntoholic, got me a sidejob yet?


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## Huntoholic (Sep 17, 2008)

brookieguy1 said:


> Huntoholic, got me a sidejob yet?


Sorry nope.........


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## wyogoob (Sep 7, 2007)

Hey, I worked on some ductwork and a fan this week:


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## brookieguy1 (Oct 14, 2008)

Wow! Looks like some heavy duty stuff. Whose house?:grin: Just kidding. Are those some kind of sprayers inside the squirrel cage?


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## wyogoob (Sep 7, 2007)

brookieguy1 said:


> Wow! Looks like some heavy duty stuff. Whose house?:grin: Just kidding. Are those some kind of sprayers inside the squirrel cage?


The fan experiences severe vibration problems caused by soda ash-impregnated coal fly ash fusing to the airfoils. The header thingie will spray sand on the blades in an attempt to keep the blades clean.

Incidently the vent on the ductwork is 84" in diameter. The ductwork itself is a variety of sizes and configurations; has venturis and orifices, gets smaller, gets bigger, changes from square to round to rectangle, then bifurcates, then thru a preheater with screens, tubular air heaters, then back to one duct, blah, blah, blah. Duct temps run from 900° to 400°.


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