×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

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

Sizing of ceiling exhaust fan for storm shelters

Sizing of ceiling exhaust fan for storm shelters

Sizing of ceiling exhaust fan for storm shelters

(OP)
Hi everyone!

I'm new here at Eng-tips.

A ventilation system will be put up on a storm shelter. (please see attahced)

Can I apply the formula P1V1/T1=P2V2/T2 in sizing the ceiling exhaust fan?

RE: Sizing of ceiling exhaust fan for storm shelters

(OP)
Can I apply the formula P1V1/T1=P2V2/T2 in sizing the ceiling exhaust fan? ----> What I mean here is that can I get the required static pressure of the fan using the formula P1V1/T1=P2V2/T2?

RE: Sizing of ceiling exhaust fan for storm shelters

No!
First get the manufacturer's fan curve; then calcuate your system curve which will be a parabolic curve; plot both of them on same graph paper(pressure vs. cfm); whre both of the curves intersect will be the fan requirement.
Better yet get an engineering handbook which will show you how to do it.

RE: Sizing of ceiling exhaust fan for storm shelters

Im confused.

Wouldnt the static pressure, be the minimal ductwork, back draft damper, and SP of the roof vent?

Then the cfm would be whatever the cfm required for internal loads or a rule of thumb air change.  (I would guess between 6 and 10).

Im embarrassed to say I dont know how to draw a system curve, but if I plug in the SP and cfm into a manufacturer software program like Greenheck, it will do it for me.

Are we saying the same thing chicopee, your way being the "correct" way but considered old school?

RE: Sizing of ceiling exhaust fan for storm shelters

The old school( the fundamentals) is what you need to understand the results that you want. The static pressure that you seek is actually calculated (via Bernoulli's equation) or measured; in many cases, the initial static pressure will be atmospheric,ie,at the intake of the exhaust fan and ducting system.

The equation that you originally presented is not really applicable for an exhaust system because it is more applicable to static condition where there is no gas flow but just expanding boudaries, pressure and temperature changes. However, having said that, you will find derivations involving Bernoulli's equation( modified first law of thermo)and equation of state (PV=mRT). Bernoulli's equation would be the right choice but must include a term for energy lost along the system length.

My first post is the way to go however you must have an idea on the CFM that you want to exhaust. If you search the web sites you will probably get an illustration on how to proceed with system curves and fan curves.
 

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


Resources

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