Large duct design reference?

[sb3]

Does anyone have a good reference book on large duct design specifically with regard to expected pressure drops in fittings and design and benefits of turning vanes? I am looking at large (20' square)power plant exhaust duct and would like to know if I could reduce pressure drop significantly by adding turning vanes in fittings. An inexpensive software simulation could also be helpful.

Thanks for your help.

 

[krb]

You can check with a duct design manual to get accurate information on the pressure loss for this type of fitting, however, a square heel and throat elbow is about the equivalent of 30 feet of straight duct, and adding turning vanes drops this to 15 feet. A radius heel and throat elbow is about the equivalent of 10 feet of straight duct.

To get an exact value for this, you will need to consult a duct design manual and determine the loss coefficient for you type of elbow and plug those numbers into the equation hl=C*(V/4005)^2 where C is the loss coefficient and V is the velocity. As always, there may be other factors to consider based on the variables for your particular application.

 

[sb3]

KRB, Thanks for your reply. You say to consult a duct design manual. Can you give me a reference? I have the ASHRAE fundamentals handbook but was looking for something more specific and preferably something that speaks to design of turning vanes in large ducts. Are they just arbitrarily drawn in?

mechatonics, Thanks for your help, I looked at the referenced web site and it looks like it may have some promise.

 

[krb]

I believe the SMACNA duct design manual has this information, but I can't find my copy at the moment. Try

http://www.smacna.org

to find a copy of their manual.

 

[sb3]

KRB, Thanks. That was what I was looking for.

 

[briand2]

If you can get to look at the HVCA manual DW144 (in the UK), it should answer your questions!

Regards,

Brian

 

[condenseddave]

http://www.accaconference.com/Merchant2/merchant.mv?Screen=CTGY&Store_Code=ACCOA&Category_Code=SDC

Manual "Q", I believe, is just what you're searching for. Manual "T" is also an excellent reference, if you're not super experienced in dust design.

 

[condenseddave]

I meant "DUCT DESIGN".