Pressure in sheet metal ducts 1

[shmar]

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

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______________________pressure__________________

 

[BigInch]

Are the ducts square or round?

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"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/

 

[Zapster]

ashrae fundamentals handbook will help with the solution method.

This sounds like a homework problem

 

[shmar]

All Ducts are square (rectangular)

 

[vpl]

shmar

Is this the same problem that you posted about two previous times (in thread378-240710 and thread378-240565?)

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 for tips on how to make the best use of the Eng-Tips Forums.

 

[JohnBreen]

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.

 

[JohnBreen]

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.

 

[vpl]

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

Patricia Lougheed

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

 

[dvd]

You might find something you're looking for in the attached:

 

[mjpetrag]

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