Equal friction method for duct sizing

In summary, the author does not understand the deltaP/L column of the results table, and wonders where the values came from.
  • #1

Homework Statement


In the attachment.

Homework Equations


Chart of pressure loss due to friction for steel ducts : http://postimg.org/image/4iml9x761/

The Attempt at a Solution


I don't understand the deltaP/L column of the results table.
Where did the values come from? Shouldn't they all be 0.063 in.wg / 100ft or 0.5 Pa/m since the principle of the equal friction method is to have the same pressure loss per length for the entire system?
 

Attachments

  • equal friction method.docx
    2.4 MB · Views: 185
Physics news on Phys.org
  • #2
Hi pinkcashmere. I don't know if others have the same difficulty, but I can't see anything in your docx attachment. Can you grab some relevant images (perhaps with a snipping tool) and upload them so they are visible in the thread? You will get better results here at PF if helpers don't have to download files from offsite and they can see the problem without having to click through to images.
 
  • #3
gneill said:
Hi pinkcashmere. I don't know if others have the same difficulty, but I can't see anything in your docx attachment. Can you grab some relevant images (perhaps with a snipping tool) and upload them so they are visible in the thread? You will get better results here at PF if helpers don't have to download files from offsite and they can see the problem without having to click through to images.

Hi gneill,
I printed out the Word document pinkcashmere posted as an Acrobat file, which is attached below.
 

Attachments

  • EqualFriction.pdf
    170.8 KB · Views: 447
  • #4
SteamKing said:
Hi gneill,
I printed out the Word document pinkcashmere posted as an Acrobat file, which is attached below.
Thanks. Wow! 2.4 MB docx file becomes a 171 KB pdf, and it boils down to a half page of text. I have seen the end of civilization, and it is a result of bloatware :smile::smile::smile:

edit: okay, I didn't page down. A page and a half of text o_O
 
  • #5
gneill said:
Thanks. Wow! 2.4 MB docx file becomes a 171 KB pdf, and it boils down to a half page of text. I have seen the end of civilization, and it is a result of bloatware :smile::smile::smile:
The reason the .docx file was so huge, I believe, was that it consisted of several pages scanned from a textbook. Those image files are generally dumped into the .docx file with no compression.
 
  • #6
pinkcashmere said:
I don't understand the deltaP/L column of the results table.
Is not this column for straight pipe only (not equivalent length)?
 

What is the Equal Friction Method for duct sizing?

The Equal Friction Method is a commonly used method for sizing air ducts in HVAC systems. It is based on the principle that the static pressure loss per unit length of the duct remains constant throughout the system, resulting in equal air velocities at each section of the duct.

How do you calculate duct sizes using the Equal Friction Method?

To calculate duct sizes using the Equal Friction Method, you will need to determine the friction rate per 100 feet of duct based on the air velocity, duct size, and type of duct material. Then, using the friction rate, you can calculate the total equivalent length of the duct system and determine the appropriate duct size for each section.

What are the advantages of using the Equal Friction Method for duct sizing?

One of the main advantages of using the Equal Friction Method is its simplicity. It is a straightforward method that can be easily applied to most duct systems. It also ensures that the air velocity remains constant throughout the duct system, resulting in better system performance and efficiency.

Are there any limitations to using the Equal Friction Method for duct sizing?

While the Equal Friction Method is widely used, it does have some limitations. It assumes that the air velocity remains constant, which may not always be the case in complex duct systems. It also does not take into account the effects of fittings and changes in the duct system that may affect the air velocity.

Are there any alternative methods for duct sizing?

Yes, there are other methods for duct sizing, such as the Static Regain Method and the T-Method. These methods take into account the effects of fittings and changes in the duct system. They are more complex and time-consuming, but may provide more accurate results in certain cases.

Suggested for: Equal friction method for duct sizing

Replies
31
Views
1K
Replies
2
Views
2K
Replies
9
Views
1K
Replies
7
Views
1K
Replies
1
Views
609
Replies
2
Views
553
Replies
1
Views
1K
Back
Top