×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Are you an
Engineering professional?
Join Eng-Tips Forums!
• Talk With Other Members
• Be Notified Of Responses
• Keyword Search
Favorite Forums
• Automated Signatures
• 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.

# Louvre sizing

 Forum Search FAQs Links MVPs

## Louvre sizing

(OP)
As per ASHRAE Fundamentals 2009 Chapter 21 Table 8, the design "face" velocities for determining the louvre size is 2m/s for Intake and 2.5m/s for exhaust. Can anyone clarify how to use these velocity values in sizing the louvres?

For example, if 5000 CMH (1.39 m3/s) of air has to be exhausted out, which one of the following is correct by considering, 2.5 m/s as the face velocity?

1) Face area of the louvre with 50% free area is 1.39/2.5 = 0.556 m2 (which means, free area of the louvre is 0.258 m2 and the velocity of exhaust air in this free area is 2.5 * 2 = 5 m/s)

OR

2) Face area of the lourve with 50% free area is 1.39/(2.5*50%/100%) = 1.112 m2 (which means, free area of the louvre is 0.556 m2 and the velocity of exhaust air in the free area is 2.5 m/s.

So, the ASHRAE guideline velocity is the face area velocity or free area velocity?

### RE: Louvre sizing

face velocity is useless, each louver has different % of free area.
Take manufacturer data that shows pressuredrop and rain entrance (for intake louver). you don't want to have rain and snow be drawn in.

ASHRAE books have a lot of good stuff, but also a lot of outdated garbage. they go by the least cheapest manufacturer so no one is offended.

### RE: Louvre sizing

there is no such thing as "face area velocity". air flows through effective area, that is why it's called effective area.

#### 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.

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

Click Here to join Eng-Tips and talk with other members!

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:

• Talk To Other Members
• Notification Of Responses To Questions
• Favorite Forums One Click Access
• Keyword Search Of All Posts, And More...

Register now while it's still free!