Static pressure in Air Handling Unit

Click For Summary

Discussion Overview

The discussion revolves around the static pressure differences in an Air Handling Unit (AHU), specifically comparing the static pressure of supply air and return air. Participants explore the implications of these pressure differences within the context of HVAC systems.

Discussion Character

  • Technical explanation, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant questions the implications of having higher static pressure in the supply duct compared to the fan compartment, seeking clarification on the relationship between these pressures.
  • Another participant asserts that the static pressure in the supply duct cannot exceed that in the discharge plenum, referencing Bernoulli's principle to support this claim.
  • A further clarification is provided regarding the specific pressures being discussed, namely the static pressure of hot return air versus cold supply air, with a request for the effects of their comparative pressures.
  • One participant states that the two pressures are not related and suggests that typically, the return static pressure is lower than the supply static pressure due to downstream control mechanisms.

Areas of Agreement / Disagreement

The discussion contains competing views regarding the relationship between the static pressures in the supply and return ducts, with no consensus reached on the implications of these differences.

Contextual Notes

Participants have not fully defined terms such as "fan compartment" and "discharge plenum," which may affect the clarity of the discussion. Additionally, assumptions regarding the operation of HVAC systems and the role of control devices in pressure differences remain unexamined.

cktan22
Messages
5
Reaction score
0
what will happen if static pressure in supply duct is higher than the fan compartment in AHU?? or vice-versa
thanks
 
Physics news on Phys.org
I'm not very clear on what you are asking. What exactly do you mean by "fan compartment"? Do you mean a discharge plenum? (Note: not all fans have a discharge plenum.) The static pressure in the supply duct cannot be higher than in a discharge plenum. It isn't physically possible as per Bernoulli's principle. The static pressure in the discharge plenum will always be higher than in the supply duct.
 
what i mean is, the static pressure for hot return air ( red colour arrow) and the static pressure for cold supply air ( blue colour) in the AHU as shown in the picture. What is the effect if the static pressure for blue colour arrow is greater than red colour arrow and vice-versa?
thank for reply.
 

Attachments

  • AHU_499w.jpg
    AHU_499w.jpg
    15.2 KB · Views: 755
The two are not related to each other, so there is no effect. But it is typical for the return static to be lower (in absolute value) than the supply static because of downstream control and distribution devices in the supply duct.
 
  • Like
Likes   Reactions: 1 person

Similar threads

Undergrad How dynamic and static pressures are related
  • · Replies 55 ·
2
Replies
55
Views
21K
Hospital Air Handler, Discharge Airflow vs. Static Pressure
  • · Replies 6 ·
Replies
6
Views
2K
Graduate Does Fluid Dynamics Explain Pressure Gradients in a Frictionless Tube?
  • · Replies 48 ·
2
Replies
48
Views
6K
Graduate Non-quasi-static Air Compression Calculation
  • · Replies 6 ·
Replies
6
Views
2K
Undergrad Air pressure question for two different water columns
  • · Replies 2 ·
Replies
2
Views
1K
Static pressure tubes vs pitot tubes
  • · Replies 2 ·
Replies
2
Views
2K
High School Pitot Tubes and Static Pressure
  • · Replies 1 ·
Replies
1
Views
2K
Undergrad Ceiling fan pressure increase or decrease
  • · Replies 4 ·
Replies
4
Views
2K
Undergrad Why does a Pressure Washer clean better than a Garden Hose?
  • · Replies 4 ·
Replies
4
Views
1K
High School Water doesn’t fall in inverted half cup
  • · Replies 1 ·
Replies
1
Views
2K