Static Pressure

[patibar]

I would request somebody to help me in understanding the concept of using static pressure in Fans and blowers performance curves. Normally for centrifugal pumps there will be a characteristic curve of differential head vs Flow. Why we use statis pressure rather than the total pressure for blowers?
Where Total Pressure = Static Pressure + Velocity Pressure.

Thanks

 

[Latexman]

It is easier, less intrusive, and less expensive to measure static pressure; no need to measure the velocity/velocity pressure. Also, if the inlet and outlet diameter of the fan or blower is about the same, there really is no need to measure velocity pressure; it cancels out when calculating the required head.

Good luck,
Latexman

 

[25362]

The following link will give you a thorough explanation. See point 4. and following sections:

https://www.captiveaire.com/MANUALS/AIRSYSTEMDESIGN/DESIGNAIRSYSTEMS.HTM#Fan_Laws

 

[25362]

As Latexman explained:

Fan curves are given in terms of total pressure vs.volumetric flow rate.
Total pressure loss = static pressure loss + dynamic pressure loss:

ΔP_total = (P_in,static − P_out,static) + ½ ρ (V_in² − V_out²)

If exit and inlet area of a duct are about the same the dynamic pressure loss (or gain) may by small and disregarded.