Negative duct fitting coeffecient

  • Thread starter Thread starter Great Smoky
  • Start date Start date
  • Tags Tags
    Fitting Negative
Click For Summary
SUMMARY

The discussion centers on the presence of negative duct fitting coefficients in the ASHRAE fitting database, indicating potential pressure regain in duct systems. The user questions whether this regain is static, given the formula P(total) = C * P(velocity), which suggests that pressure only decreases downstream of the fan. The confusion arises from the contradiction between negative coefficients and expected pressure loss, particularly concerning the sizes of inlet and outlet fittings.

PREREQUISITES
  • Understanding of ASHRAE fitting database
  • Knowledge of ductwork pressure dynamics
  • Familiarity with the formula P(total) = C * P(velocity)
  • Experience with duct fitting sizes and configurations
NEXT STEPS
  • Research the implications of negative duct fitting coefficients in HVAC systems
  • Explore ASHRAE guidelines on pressure regain and fitting design
  • Learn about pressure loss calculations in duct systems
  • Investigate the effects of inlet and outlet size variations on duct performance
USEFUL FOR

HVAC engineers, ductwork designers, and professionals involved in airflow optimization will benefit from this discussion.

Great Smoky
Messages
8
Reaction score
0
In the ASHRAE fitting database, there are negative duct fitting coefficients. I assume this means that that particular fitting will produce a pressure regain. However, I am unsure that it would be a static regain because:

the formula is P(total)=C*P(velocity), and P(total) only can only drop as it travels thru a duct (downstream of the fan). Is this a contradition?

So I am confused of what the negative means because of this contradiction. Anybody know?
 
Engineering news on Phys.org
I have tried a range on inlet and outlet sizes. Some with the same and some with different sizes and a negative coefficient result.
 

Similar threads

Ducted Fan Pressure Differential: Questions Answered
  • · Replies 15 ·
Replies
15
Views
7K
Fan total pressure enough or not?
  • · Replies 1 ·
Replies
1
Views
3K
Modeling Air Compression Cylinder
  • · Replies 45 ·
2
Replies
45
Views
6K
Calculating changes in Fan Power
  • · Replies 6 ·
Replies
6
Views
17K
Undergrad Questions about Negative Pressure and Vacuum Energy
  • · Replies 5 ·
Replies
5
Views
3K
Huge pressure drop after changing pipe length (Don't think it's loss)
  • · Replies 13 ·
Replies
13
Views
4K
What is the Gauge Pressure Just Downstream of a Fan in a Duct System?
  • · Replies 1 ·
Replies
1
Views
2K
Undergrad Negative Mass and Hawking Radiation
  • · Replies 6 ·
Replies
6
Views
3K
Automotive Understanding Tire Forces in Bicycle Simulation: Physics and Code Explained
  • · Replies 2 ·
Replies
2
Views
2K
Pressure drop analysis on water pipe system w/pump
  • · Replies 29 ·
Replies
29
Views
9K