×
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

checking cfm for electric heat

checking cfm for electric heat

checking cfm for electric heat

(OP)
What is correct formula for checking cfm on electric heat residential.I have been using. Cfm=BTU ÷  (1.08×delta t)

RE: checking cfm for electric heat

Heating elements will have different surface temperatures under varying air velocities.  The maximum allowable surface temperature of the heating elements will be under still air conditions. As air velocities increase around H.E.'s, their surface temperatures will decrease.  Your best bet is to contact manufacturers of these H.E.'s and ask for a temperature profile vs. air velocity.  The results will based on a lineal measurement.  Then you'll need to determine the smallest  design surface temperature which these heaters are set to operate so that you can determine the CFM based on the total number of H.E.'s and their total length.
Two problems with your formula.  One is the delta and the next is the BTU/HR or in your case BTU.  Both these values are used by the manufacturer and you have now idea what number they are using.  
BTU/HR is determined by the allowable surface temperature as mentioned above.  The delta T is based on recomendation by HVAC design guidelines.   

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