Static pressure in Air Handling Unit

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SUMMARY

The discussion centers on the relationship between static pressure in the supply duct and the fan compartment of an Air Handling Unit (AHU). It is established that the static pressure in the supply duct cannot exceed that in the discharge plenum, as dictated by Bernoulli's principle. The conversation clarifies that the static pressures for hot return air and cold supply air are not directly related, although it is typical for the return static pressure to be lower than the supply static due to downstream control and distribution devices.

PREREQUISITES
  • Understanding of Bernoulli's principle
  • Familiarity with Air Handling Units (AHUs)
  • Knowledge of static pressure concepts in HVAC systems
  • Awareness of downstream control and distribution devices
NEXT STEPS
  • Research the principles of static pressure in HVAC systems
  • Learn about the design and function of Air Handling Units (AHUs)
  • Explore the effects of downstream control devices on air distribution
  • Study Bernoulli's principle and its applications in fluid dynamics
USEFUL FOR

HVAC engineers, building maintenance professionals, and anyone involved in the design or operation of air handling systems will benefit from this discussion.

cktan22
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what will happen if static pressure in supply duct is higher than the fan compartment in AHU?? or vice-versa
thanks
 
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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.
 

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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.
 
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