EcoRenovator  

Go Back   EcoRenovator > Improvements > Conservation
Advanced Search
 


Blog Register 60+ Home Energy Saving Tips Recent Posts Search Today's Posts Mark Forums Read


Reply
 
Thread Tools Display Modes
Old 07-29-17, 07:54 AM   #1
SentinelAeon
Lurking Renovator
 
Join Date: Jul 2016
Location: Europe
Posts: 25
Thanks: 0
Thanked 0 Times in 0 Posts
Default big fan connected to small tube

Hi,

I have a question regarding fans and connecting them to a tube that is of a smaller diameter than the fan, a good example would be a vacuum, where you get big airflow through a very small tube.

How much airflow is lost when you connect a bigger fan to a smaller tube ? For example 12x12cm fan connected to a 10x10 or 8x8 tube. I am guessing it depends on the power of the fan, for instance vacuum "fan" being 2000W and computer fan being 1 or 2W. Is there a formula to calculate how much is lost ?

SentinelAeon is offline   Reply With Quote
Old 07-31-17, 07:48 AM   #2
Ator
Lurking Renovator
 
Join Date: Jan 2015
Location: Netherlands
Posts: 25
Thanks: 1
Thanked 7 Times in 7 Posts
Default

Quote:
Originally Posted by SentinelAeon View Post
Is there a formula to calculate how much is lost ?
Had to dig up some of that old aerodynamics theory, but I think you could try with:

Delta P = f * Rho * (L / D) * (v^2 / 2); f=64/Re

Delta P = Pressure loss
Rho = Density air
L = Length pipe
D = Diameter pipe
v = velocity air
Re = Reynolds number

The flow Q1 = Q2; v1 * A1 = v2 * A2

Which means that the flow speed will increase in the smaller tube and thus increase the drag

Disclaimer: All in metric, laminar, isotropic flow!

It's not possible to do it without knowing some basic data about the fan, but as you can see from the equations the higher the flow speed the higher the losses.
Ator is offline   Reply With Quote
Old 08-27-17, 02:46 PM   #3
Piwoslaw
Super Moderator
 
Piwoslaw's Avatar
 
Join Date: May 2009
Location: Warsaw, Poland
Posts: 916
Thanks: 166
Thanked 91 Times in 76 Posts
Default

If you must move the air through a smaller diameter tube, because of dimensional constraints, then try to keep the tube as short as possible, or at least keep the bottleneck short. For example, if you must move the air a total of 200cm, but the constraint is only 50cm, then use a larger diameter tube of the remaining 150cm.

And keep the tube smooth, without any sharp bends.

__________________
Ecorenovation - the bottomless piggy bank that tries to tame the energy hog.
Piwoslaw is offline   Reply With Quote
Reply


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -5. The time now is 03:28 PM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2019, vBulletin Solutions Inc.
Ad Management by RedTyger
Inactive Reminders By Icora Web Design