Go Back   Physics Help Forum > High School and Pre-University Physics Help > Thermodynamics and Fluid Mechanics

Thermodynamics and Fluid Mechanics Thermodynamics and Fluid Mechanics Physics Help Forum

Like Tree1Likes
  • 1 Post By oz93666
Reply
 
LinkBack Thread Tools Display Modes
Old Aug 9th 2019, 12:48 PM   #1
Junior Member
 
Join Date: Aug 2019
Posts: 4
Determining length of a tube with applied pressure

Hi folks,

I have a question.

Imagine i'm blowing air through a duct that is capped in one side.

The tube is made of plastic and has a 14mm external radius and an internal readius of 10mm.

If I apply a constant pressure of 16 bar, and it takes 30 seconds for the air to come out on the origin, what is the lenght of the tube?

Thank you in advance.
Regards
Attached Thumbnails
Determining length of a tube with applied pressure-img_6274.jpg  
joaoortinsbrito is offline   Reply With Quote
Old Aug 11th 2019, 03:46 AM   #2
Senior Member
 
Join Date: Apr 2017
Posts: 513
There are many errors , just in the question!

For a start the blowing machine ... You cannot say this applies a constant pressure of 16 bar .... It maybe able to achieve a max pressure of 16 bar , this will be with no air flow . Once connected to your tube the pressure will dramatically drop ... We need to know the flow rate of air (liters per sec) your pump can deliver at different back pressure ...

Is this a practical problem ?? Give more information.
topsquark likes this.
oz93666 is online now   Reply With Quote
Old Aug 11th 2019, 04:37 AM   #3
Junior Member
 
Join Date: Aug 2019
Posts: 4
Yes, it is a pratical problem. We want to blow a cable from point A to point B. Before blowing the cable we blow air to see if it's all good, but in this case we have a blockage somewhere. I was trying to find a way to determine the blockage, since we already know that takes 30seconds for the air to come out.
joaoortinsbrito is offline   Reply With Quote
Old Aug 11th 2019, 04:41 AM   #4
Junior Member
 
Join Date: Aug 2019
Posts: 4
I'll try to know the air flow rate...
joaoortinsbrito is offline   Reply With Quote
Old Aug 11th 2019, 01:34 PM   #5
Senior Member
 
Join Date: Apr 2017
Posts: 513
Originally Posted by joaoortinsbrito View Post
Yes, it is a pratical problem. We want to blow a cable from point A to point B. Before blowing the cable we blow air to see if it's all good, but in this case we have a blockage somewhere. I was trying to find a way to determine the blockage, since we already know that takes 30seconds for the air to come out.
Ah ... I see .. In that case I would just take off the end cap and connect the blower , 16bar is considerable pressure it should clear any blockage .
oz93666 is online now   Reply With Quote
Old Aug 12th 2019, 01:15 AM   #6
Junior Member
 
Join Date: Aug 2019
Posts: 4
That's the problem. The cap is underground. We'll need to dig to find it...
joaoortinsbrito is offline   Reply With Quote
Old Aug 12th 2019, 02:49 AM   #7
Senior Member
 
Join Date: Apr 2017
Posts: 513
Phew this is hard work ...

So the pipe is buried underground , it has a cap on the end , but you don't know where the end is ???

But you want to blow a cable from one end of the pipe to the other ???

It seems the first job is to find where the end is and dig it up

If you have a rigid piece of wire or rod you could push it down one end of the pipe till it hits the end cap (or the obstruction) . Then take this length of wire out ,lay it on the ground roughly above the pipe and this will tell you where to dig.
oz93666 is online now   Reply With Quote
Old Aug 12th 2019, 03:13 AM   #8
Senior Member
 
Join Date: Oct 2017
Location: Glasgow
Posts: 474
Water utilities usually use water pressure sensors to determine where leaks/blockages occur. Without access to the whole pipe, it's going to be difficult to figure out where the blockage is.

If it's a straight pipe, maybe echolocation might work? Pass a sound pulse-wave along the air column and then record the time taken for the reflected wave to return?
benit13 is offline   Reply With Quote
Reply

  Physics Help Forum > High School and Pre-University Physics Help > Thermodynamics and Fluid Mechanics

Tags
applied, determining, length, pressure, tube



Thread Tools
Display Modes


Similar Physics Forum Discussions
Thread Thread Starter Forum Replies Last Post
determine pressure applied by truck driving into wall at different speeds DeltBoy Kinematics and Dynamics 8 Dec 22nd 2015 08:15 AM
Force applied to a Hair p75213 Kinematics and Dynamics 2 Aug 2nd 2010 05:53 PM
Stuck!! Determining an unstretched length jddery Kinematics and Dynamics 0 Jan 31st 2010 07:42 PM
The First Law of Thermodynamics applied to a Cycle Auto Engineer Thermodynamics and Fluid Mechanics 8 Aug 12th 2009 11:18 AM
Determining absolute pressure Auto Engineer Advanced Thermodynamics 2 Jul 31st 2009 01:45 PM


Facebook Twitter Google+ RSS Feed