×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

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!
  • Students Click Here

*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

Jobs

Pressure in sheet metal ducts

Pressure in sheet metal ducts

Pressure in sheet metal ducts

(OP)
Hi, in a system for air conditioning if i have a fan supplying air through a duct system, how can i find the pressure in the duct in any given location up to the grill outlet. we can assume the system provides 1,000 l/s to a 1 grill and the fan has a head to resist the duct and the grill outlet. this is real world problem

________________________________________________

______________________pressure__________________

RE: Pressure in sheet metal ducts

Are the ducts square or round?

**********************
"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/

RE: Pressure in sheet metal ducts

ashrae fundamentals handbook will help with the solution method.  

This sounds like a homework problem

RE: Pressure in sheet metal ducts

(OP)
All Ducts are square (rectangular)

RE: Pressure in sheet metal ducts

shmar

Is this the same problem that you posted about two previous times (in thread378-240710: pressure loss of air passing through a small slot and thread378-240565: Air Pass Through a wall passage?)

Unfortunately no one on this site is a mind-reader (and poorly described posts come across as student homework rather than real life projects).  Instead of continuing to start new threads, pick one, post a detailed description of what you're trying to do and give people something to work with.

Otherwise it's doubtful you will ever get any useful response.

Patricia Lougheed

Please see FAQ731-376: Eng-Tips.com Forum Policies: Eng-Tips.com Forum Policies for tips on how to make the best use of the Eng-Tips Forums.

RE: Pressure in sheet metal ducts

From "shmar
All Ducts are square (rectangular)"

NOT True.

Probably most of the HVAC ducts in the commercial building world are square (rectangular) but ducts come in all sizes and shapes and are found in many applications.  Perhaps one of the best books on the STRUCTURAL design of industrial ductwork is "The Structural Design of Air and Gas Ducts for Power Stations and Industrial Boiler Applications", ISBN 0-7844-0112-8, American Society of Civil Engineers.  Library of Congress catalog card number 95-24709.  The edition that I use is the 1995 edition.  It is NOT just for Power Plants.

Regards, John.

RE: Pressure in sheet metal ducts

OK, Sorry.  You meant that all your particular ducts are square (rectangular).  I hope I didn't offend as that is never my intention,

John.

RE: Pressure in sheet metal ducts

John When I first read shmar's response I had the same reaction.

Patricia Lougheed

Please see FAQ731-376: Eng-Tips.com Forum Policies: Eng-Tips.com Forum Policies for tips on how to make the best use of the Eng-Tips Forums.

RE: Pressure in sheet metal ducts

the easiest way is just going out and sticking a pitot tube in various parts of the duct.  plot those results in excel against their location.

if you cant get access to the duct, you can calculate it by adding up the frictional losses along the length of the pipe from an ashrae friction loss per length graph, along with any bends, and then add the back pressure created by the obstruction of the grill.

 

-Mike

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!


Resources