Volumetric flow rate of a pipe

[Anon_Miner]

TL;DR Summary

How much air (maximum) can pass through a 10 cm diameter pipe which is 15 meters long vertically? m3/h scale

Hello kind people of PF

I am looking to mount a fan on one end of a pipe but I'm not sure how much air can the pipe transfer. (Volumetric flow rate)

The pipe is vertical and 15 meters long.It has a diameter of 10 cm. I'm looking to push air from top to bottom using a fan.

Need to know the maximum volumetric flow rate of the pipe on a m3/h scale.

Thank you!

Edit: I got the answers I was looking for and posted a statement in my last comment.Don't try this at home. Lol

 

[russ_watters]

Welcome to PF!

I am looking to mount a fan on one end of a pipe but I'm not sure how much air can the pipe transfer. (Volumetric flow rate)

The pipe is vertical and 15 meters long.It has a diameter of 10 cm. I'm looking to push air from top to bottom using a fan.

Need to know the maximum volumetric flow rate of the pipe on a m3/h scale.

It depends strongly on how powerful your fan is.

 

[Anon_Miner]

Welcome to PF!

It depends strongly on how powerful your fan is.

Thanks for your reply!

Yes I know that but I wanted to know the maximum capacity of the pipe itself so I don't buy a fan too powerful and waste my money on extra power that will be of no use.

 

[Chestermiller]

What kind of flow rates and pressures are you looking for?

 

[Anon_Miner]

What kind of flow rates and pressures are you looking for?

I really would like to install a fan that can move 11000 m3/h of air through the pipe but I'm not sure if the pipe can in fact transfer that amount of air.

If 11000 is not a possibility, how about 5500 m3/h of air? Can the pipe support this much air flow?

Pressure is of no consequence.

I only need to know how much air I can move through the pipe.

 

[Chestermiller]

11000 m^3/hr is the same as 3.06 m^3/s. The cross sectional area of the pipe is 0.00785 m^2. What kind of flow velocity does this represent, and how does it compare with the speed of sound?

 

[Lnewqban]

I really would like to install a fan that can move 11000 m3/h of air through the pipe but I'm not sure if the pipe can in fact transfer that amount of air.

If 11000 is not a possibility, how about 5500 m3/h of air? Can the pipe support this much air flow?

Pressure is of no consequence.

I only need to know how much air I can move through the pipe.

That volume is impossible to achieve for a duct of that diameter.
Is there any way to increase the sectional area of that duct or the number of ducts.

 

[russ_watters]

Yes I know that but I wanted to know the maximum capacity of the pipe itself so I don't buy a fan too powerful and waste my money on extra power that will be of no use.

I really would like to install a fan that can move 11000 m3/h of air through the pipe but I'm not sure if the pipe can in fact transfer that amount of air.

If 11000 is not a possibility, how about 5500 m3/h of air? Can the pipe support this much air flow?

I'll let you do the math as @Chestermiller suggests, but will add to his point that the speed of sound is the limiting factor on flow through a duct.

Pressure is of no consequence.

I only need to know how much air I can move through the pipe.

Well you need to know pressure in order to size/select the fan. It'll also help you pick the car engine you'll need to run it.

 

[Anon_Miner]

That volume is impossible to achieve for a duct of that diameter.
Is there any way to increase the sectional area of that duct or the number of ducts.

There are 2 pipes. They have the same diameter (10 cm).
So if 11000 m3/h is impossible for one pipe, then how about 5500 m3/h per pipe? will that work?

 

[Anon_Miner]

11000 m^3/hr is the same as 3.06 m^3/s. The cross sectional area of the pipe is 0.00785 m^2. What kind of flow velocity does this represent, and how does it compare with the speed of sound?

I'll let you do the math as @Chestermiller suggests, but will add to his point that the speed of sound is the limiting factor on flow through a duct.

Well you need to know pressure in order to size/select the fan. It'll also help you pick the car engine you'll need to run it.

Let me explain my exact situation

There is a room which has some devices in it. The air intake of these devices is 10880 m^3/h. The room has no other air intake except for 2 pipes that are both 10 cm in diameter.

I'm looking to put forward fans on one end of the pipes to supply the air demanded by these devices.

I was looking to put a fan with 11000 m3/h capacity on one pipe to reduce my expenses. but now that it seems one pipe can not support that much of air flow; I'll be looking to put 2 fans with 5500 m3/h capacity on both pipes.

the devices exhaust the air they intake out of the room, which is why I thought since the amount of air intake and air output are very close, there will be no change in the pressure of the room.

 

[Chestermiller]

I'm a little confused by this. It seems like the intake and output velocities of these pipes will be extremely high. We're talking higher than severe hurricane and tornado velocities. Does this system already exist? What about the intakes to the room? What are these like?

 

[Lnewqban]

There are 2 pipes. They have the same diameter (10 cm).
So if 11000 m3/h is impossible for one pipe, then how about 5500 m3/h per pipe? will that work?

A regular blower can normally push between 70 and 90 cubic meters per hour through one 10 cm diameter duct.
Any flow forced to go beyond the speed of 20 meters per second creates much noise and requires high pressure fans.

For the amount of ventilation you need, we are talking about one round duct of 80 centimeters of diameter or of a wall louver of 1 meter x 1 meter.

Sorry, Anon, you will need to find an alternate solution to satisfy the air intake requirements of those devices.
Are you sure all of those will be running simultaneously?

 

[russ_watters]

Let me explain my exact situation

Thank you!

There is a room which has some devices in it. The air intake of these devices is 10880 m^3/h. The room has no other air intake except for 2 pipes that are both 10 cm in diameter.
[snip]
the devices exhaust the air they intake out of the room, which is why I thought since the amount of air intake and air output are very close, there will be no change in the pressure of the room.

I'm looking to put forward fans on one end of the pipes to supply the air demanded by these devices.

So they take air from inside the room and exhaust it out of the room? Is this a new room or is there currently something providing make-up air at the same airflow?

Unless the pressure difference were huge (enough to collapse the room), the airflow into and out of a room will always be equal.

I was looking to put a fan with 11000 m3/h capacity on one pipe to reduce my expenses. but now that it seems one pipe can not support that much of air flow; I'll be looking to put 2 fans with 5500 m3/h capacity on both pipes.

I suspect you don't know how to select such a fan, and I implore you to keep going with the analysis so you don't make a mistake that costs you thousands of dollars.

Why can't you bring more and/or larger ducts into the room?

 

[Anon_Miner]

A regular blower can normally push between 70 and 90 cubic meters per hour through one 10 cm diameter duct.
Any flow forced to go beyond the speed of 20 meters per second creates much noise and requires high pressure fans.

For the amount of ventilation you need, we are talking about one round duct of 80 centimeters of diameter or of a wall louver of 1 meter x 1 meter.

Sorry, Anon, you will need to find an alternate solution to satisfy the air intake requirements of those devices.
Are you sure all of those will be running simultaneously?

I was already planning on using high pressure fans so that is not a problem.

But how much noise are we talking about for moving 5500 m3/h of air through a 10 cm pipe? because the pipes are within walls of a building that has people living inside. will the noise be overwhelming or just a minor nuisance?

unfortunately building/enlarging additional pipes is not possible.

Thanks for taking the time to help me!

 

[Anon_Miner]

Thank you!

So they take air from inside the room and exhaust it out of the room? Is this a new room or is there currently something providing make-up air at the same airflow?

Unless the pressure difference were huge (enough to collapse the room), the airflow into and out of a room will always be equal.

I suspect you don't know how to select such a fan, and I implore you to keep going with the analysis so you don't make a mistake that costs you thousands of dollars.

Why can't you bring more and/or larger ducts into the room?

Unfortunately making additional customization is not a possibility.

The room has always been there but was never used in such manner I'm planning to use it.

This was the kind of fan I was planning to use but apparently the noise of the air traveling through the pipe will make the people living above hell. (The pipes have passed within the walls from the roof to the room).

And the reason I can't bring larger ducts to the room is because this room is kinda in the basement and 3 floors are above it. So there is no way of bringing additional ducts without making drastic changes to the building.

Nevertheless I appreciate your time and efforts!

 

[Anon_Miner]

I'm a little confused by this. It seems like the intake and output velocities of these pipes will be extremely high. We're talking higher than severe hurricane and tornado velocities. Does this system already exist? What about the intakes to the room? What are these like?

It doesn't exist but I was planning to make it work. However I hadn't accounted for the speed of the air traveling through the pipes and the noise it will make. Such a stupid mistake by me.
The room has no other intakes except for these two pipes.
Anyway thanks for your time!

 

[anorlunda]

Nevertheless I appreciate your time and efforts!

Wait a minute. Is it possible that you placed a decimal wrong and thus overestimated the air needed by 10x or 100x?

What are the devices in that room that take the air in? Where does the air go?

 

[Anon_Miner]

Wait a minute. Is it possible that you placed a decimal wrong and thus overestimated the air needed by 10x or 100x?

What are the devices in that room that take the air in? Where does the air go?

Hi
There are 16 devices. Each device has 2 fans. Each fan has an air intake of 340 m3/h.
340*2*16 was my calculation that got me to 10880 m3/h.
The devices are ASIC miners.
As for the air output, I have built an exhaust per device that takes their air output, out of the room.
But since supplying the air needed by the devices seem improbable, everything goes down the drain.

 

[Anon_Miner]

So basically if i try to move 5500 m3/h of air through a 10 cm diameter pipe, it will reach a speed of 194.52 m/s which is like 700 km/h!

I feel really stupid right now
Would delete this post if I knew how.

Sorry guys for wasting your time with my negligence before posting here.
And thank you for your replies and efforts. I really appreciate it. You guys are the best. PF is the best.

 

[Lnewqban]

...I feel really stupid right now
Would delete this post if I knew how.
...

Don't feel bad.
The incorrect approach is to try to ventilate all these devices that only need to be cooled.

The function of those built-in fans of the devices is to move cool air over the internal electronic components, which temperature should be kept low.
To remove the generated heat away from the electronic components is all is needed.
Those fans were designed to recirculate the air of the room, not outdoors dusty air.
The gradual heating of that room air makes the fan move excessive air over the electronic parts, just to play on the safe side.

The proper way to achieve that cooling is by installation of air conditioning equipment that keeps carrying the heat from the air of the room to the outdoors.
In other words, rather than moving that generated heat out using huge volumes of air, liquid, which can reach higher temperature differential, is doing the work.
You can calculate the capacity of the air conditioning equipment by computing the power consumption of all the devices.

Please, read this related thread:
https://www.physicsforums.com/threads/where-do-i-put-this-server-rooms-air-exhaust.984172/

You are welcome