Previous in Forum: Tip Velocity Limitations for Cast Materials   Next in Forum: Practical Measurement of Torque
Close
Close
Close
13 comments
Member

Join Date: Jun 2009
Posts: 5

Theoretical Measurement of Fan Flow Rates

08/11/2009 12:31 AM

I would like to know how one would measure the amount of air displaced by a normal ceiling fan running at its maximum speed, supposing we know its speed, swept length, blade angles etc.

Register to Reply
Pathfinder Tags: fan
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.
Guru
United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

Join Date: Jan 2007
Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain. Kettle's on.
Posts: 30410
Good Answers: 819
#1

Re: Theoretical Measurement of Fan Flow Rates

08/11/2009 3:09 AM

Is the distance from the ceiling and other fixed objects also known?

__________________
"Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
Register to Reply
Member

Join Date: Jun 2009
Posts: 5
#10
In reply to #1

Re: Theoretical Measurement of Fan Flow Rates

08/12/2009 2:43 AM

slack, i wanted a theoretical measurement, so you could have safely assumed the data you required! (well, except for the flow rate).

Register to Reply
Guru
Popular Science - Weaponology - New Member United Kingdom - Member - New Member

Join Date: May 2007
Location: Harlow England
Posts: 16499
Good Answers: 662
#2

Re: Theoretical Measurement of Fan Flow Rates

08/11/2009 4:59 AM

Measure the air velocity at various points.
A ceiling fan is there to provide a subjective feeling of comfort which could be measured by the distribution and velocity of the air , not necessarilly the volume displaced.
Be careful to think carefull about what exactly you should measure.

'Theoretical measurement' is a somewhat confusing juxtaposition of words.

Del

__________________
health warning: These posts may contain traces of nut.
Register to Reply
Member

Join Date: Jun 2009
Posts: 5
#11
In reply to #2

Re: Theoretical Measurement of Fan Flow Rates

08/12/2009 2:48 AM

Del, what i really want is the amount of air displaced by the fan in a minute or something like that, but definitely not the velocity for the final answer.

Sorry for using confusing words, but i just wanted to know how one would go about the calculation with out using any instruments etc.

Register to Reply
Guru
Engineering Fields - Mechanical Engineering - New Member Hobbies - CNC - New Member

Join Date: Aug 2006
Location: Western Australia
Posts: 755
Good Answers: 58
#3

Re: Theoretical Measurement of Fan Flow Rates

08/11/2009 5:09 AM

Welcome.

I assume that as you use the word theoretical, you want some sort of calculation.

This example should get you started

__________________
If you can't explain it simply, you don't understand it well enough. (A.E.)
Register to Reply
Guru
Popular Science - Weaponology - New Member United Kingdom - Member - New Member

Join Date: May 2007
Location: Harlow England
Posts: 16499
Good Answers: 662
#4
In reply to #3

Re: Theoretical Measurement of Fan Flow Rates

08/11/2009 5:13 AM

Ha, I would counter that, by saying he uses the word 'measurement' and therefore want to do something useful .
Del

__________________
health warning: These posts may contain traces of nut.
Register to Reply Off Topic (Score 5)
Guru

Join Date: Dec 2005
Posts: 1601
Good Answers: 19
#5
In reply to #4

Re: Theoretical Measurement of Fan Flow Rates

08/11/2009 6:51 AM

Theoretically he wants to design a box to catch and count units of air displaced, and is using the fan blade speed and geometry to prevent the box from impacting the fan blade and throwing the whole system out of balance!

Try to google propeller perfomance calculations, or look up some fan design books at the local engineering college library for fan design theory.

__________________
Eventually, one needs to realize that it is far less important to be the smartest person in the room than it is to sit next to that person and make friends.
Register to Reply Off Topic (Score 5)
Guru
Popular Science - Weaponology - New Member United Kingdom - Member - New Member

Join Date: May 2007
Location: Harlow England
Posts: 16499
Good Answers: 662
#6
In reply to #5

Re: Theoretical Measurement of Fan Flow Rates

08/11/2009 7:03 AM

I still reckon my answer#2 is on the money.
It's not how much air you move, but where it goes.
Del

__________________
health warning: These posts may contain traces of nut.
Register to Reply Off Topic (Score 5)
Guru

Join Date: Dec 2005
Posts: 1601
Good Answers: 19
#7
In reply to #6

Re: Theoretical Measurement of Fan Flow Rates

08/11/2009 12:47 PM

And what you do with it when it gets there!

My first reply was a weak attempt to reply to your trying to determine if he wanted a calculation to estimate air displacement or a method to try and measure the air displacement. My attempt at humor is sometimes too obscure. Sorry.

__________________
Eventually, one needs to realize that it is far less important to be the smartest person in the room than it is to sit next to that person and make friends.
Register to Reply Off Topic (Score 5)
Guru
Popular Science - Weaponology - New Member United Kingdom - Member - New Member

Join Date: May 2007
Location: Harlow England
Posts: 16499
Good Answers: 662
#8
In reply to #7

Re: Theoretical Measurement of Fan Flow Rates

08/11/2009 1:19 PM

No, indeed, sometimes I'm so busy trying to be funny I miss other peoples humour..
Ha, we can have an apologising contest now.
Del

__________________
health warning: These posts may contain traces of nut.
Register to Reply Off Topic (Score 5)
Guru

Join Date: Dec 2005
Posts: 1601
Good Answers: 19
#9
In reply to #8

Re: Theoretical Measurement of Fan Flow Rates

08/11/2009 5:05 PM

No please let me go first. I sorry you mis understood my feeble sense of humor. I'm afraid that as a wee lad I saw too many of the Monty Python shows you exported to the US!

__________________
Eventually, one needs to realize that it is far less important to be the smartest person in the room than it is to sit next to that person and make friends.
Register to Reply Off Topic (Score 5)
Guru
Popular Science - Weaponology - New Member United Kingdom - Member - New Member

Join Date: May 2007
Location: Harlow England
Posts: 16499
Good Answers: 662
#13
In reply to #9

Re: Theoretical Measurement of Fan Flow Rates

08/12/2009 2:52 AM

Au contraire, entirely my fault.
I prostrate my myself at your feet and writhe hideously in the mire of abject misery.
(Yeah that should do it, it works with Mrs Cat)
Del

__________________
health warning: These posts may contain traces of nut.
Register to Reply Off Topic (Score 5)
Member

Join Date: Jun 2009
Posts: 5
#12
In reply to #3

Re: Theoretical Measurement of Fan Flow Rates

08/12/2009 2:50 AM

Prof, thanx for the amazing info u provide, hopefully i could derive something useful for me from that. will start off by solving that problem. Thanx again!

Register to Reply
Register to Reply 13 comments
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.
Copy to Clipboard

Users who posted comments:

Del the cat (5); kenichi (3); PWSlack (1); Ried (3); The Prof (1)

Previous in Forum: Tip Velocity Limitations for Cast Materials   Next in Forum: Practical Measurement of Torque

Advertisement