4 replies to this topic

[kinetic123]

Hi all, 

I want to understand little bit more on extraction fans.

I am aware that

 

total pressure = static pressure + velocity pressure 

 

I understand that using Darcy's equation, based on selected flow rate and pipe layout, I can calculate velocity pressure but I can't visualise and understand the term 'STATIC PRESSURE'

 

I have two types of arrangements [please see attached sketches] 

Case#1 fan is located 5m from ground floor
Case#2 fan is located on the ground floor

 

Based on recommended velocities and required flowrate, I have already specified ducting size but little bit confused with static pressure and total pressure.

 

Any help please?

 

Thanks

Attached Files

•  sketch.docx   21.51KB   17 downloads

[AlertO]

hi

 

see the definition for total, static and velocity pressures in the attachment. it may help you more clear about them.

Attached Files

•  Fan Terminology and Definitions.pdf   122.25KB   28 downloads

[kinetic123]

AlertO

 

Thanks for your link but it's not easy to follow the term, STATIC PRESSURE.

 

I can see, it's extremely straight forward for liquid [e.g. for pump] static pressure but not for fan.

 

Is there anybody who can explain the term, Static Pressure for fan? and how this will be different for those two cases, Case#1 and Case#2 please?

 

Thanks....

[PingPong]

It is not different for a liquid or a gas.

STATIC pressure at a point in the system is the actual pressure of a fluid, minus the atmospheric pressure.

It is the pressure that a pressure gauge located at that point would indicate. One can also call it: gauge pressure.

[fallah]

Hi,

 

Total pressure of a flowing fluid, either gas or liquid, as the stagnation pressure is the pressure that would be measured by a pitot tube pointing toward the flow direction. In the pitot tube the flow is brought to a rest (i.e. made stagnant) and the velocity head is converted to pressure head. The stagnation pressure is therefore the sum of the static pressure and the velocity head.

 

Then the static pressure is the pressure that would be measured by a pressure gauge where the connection to the flow passage is perpendicular to the flow direction.

Edited by fallah, 25 March 2014 - 06:25 AM.