Contact US

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Closed Loop Air Circulation Wind Tunnel, Pressure Differential Measurement

Closed Loop Air Circulation Wind Tunnel, Pressure Differential Measurement

Closed Loop Air Circulation Wind Tunnel, Pressure Differential Measurement

Hello everyone,
I am new here. I am hopping to get some replies to clarify and help with my task at hand.
I have a 6" x 12" sheet metal duct, about 24 feet long, with a fan inside it to circulate the air. For my application, I need to measure the air speed at the center of the duct at about 8 feet away from the fan outlet, on its pressure side. I am using a pitot tube and manometer to measure the pressure differential, I can calculate speed of air from there (the ranges of differential pressure that I am expecting is from 0.1 to 7 Pascals (.03 inch w.c.). Well, both plastic tubes coming from the pitot tube and going to the manometer are reading negative pressure (vacuum). There is a difference between the two line vacuums. Air is blowing by the pitot tube, but I do not see pressure. Could I still use these vacuum measurement to calculate my air speed? I would appreciate any comments. thanks.

RE: Closed Loop Air Circulation Wind Tunnel, Pressure Differential Measurement

The dynamic pressure in a fluid flow can be expressed as

Quote (https://www.engineeringtoolbox.com/velocity-head-d...)

pd = 1/2 ρf v^2
pd = dynamic pressure in fluid (Pa, psf (lb/ft^2))
ρf = density of fluid (kg/m3, lb/ft^3)
v = fluid velocity (m/s, ft/s)
The dynamic pressure is measured between the two ports on the pitot tube.

Measuring pressure differentials this small with a manometer with any repeatability is really hard. Getting an appropriate Digital Manometer will make the job much easier. Link to one of many sources

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close