What are the unknown variables in the flowrate equation?

[Scott Vidicik]

Hello friends!

I got this flowrate equation I wish to translate, into metric system, but somehow I find it hard to do.

It is as follows:

M (lb/s) = A x C x P / √(R)

A: Area (inches)
C: Flow coefficient
P: Pressure (psi)
R: Temperature (Rankine)

So, to get this into SCFM I modify the equation with gas density of air
0.7494 lb/ft³ and 60s/min so I get

V (SCFM) = A x P x C x 60 / [√(R) x 0.7494]
this gives me SCFM. I could ofcourse just go from SCFM to m³/min, but that wouldn't be as awesome as having a formula where you could put in your data in metric.

Any help would be really really helpful.
Feel free to ask if there's anything unclear. Thanks a lot!

 

[Scott Vidicik]

I find it hard to believe that neither the American nor European members can help me out here :)

 

[Scott Vidicik]

Bumping it for the last time.

If no one are able to help me, do you have any suggestions for where I could find some?

Thanks in advance! :)

 

[Scott Vidicik]

I found the answer. Feel free to ask if interested.

Now I got another probem!

I found this equation, but I don't understand it.

P/0.1 x Flow x Hours x 0.35 x 0.007 x cost.

P is in bar, so by dividing by 0.1 we get MPa.
Flow is in L/sec
Hours means operating hours for a compressor.
0.35 is some unknown variable, so is 0.007.
Cost is cost per kwh.

So I get

MPa x L/sec x Hours x 0.35 x 0.007 x € = total cost of a pressure drop.

What the heck is 0.35 and 0.007 values for? I haven't given any other input than what I've said.

Thanks a lot in advance!

EDIT:
There also seems to be a rule-of-thumb which claims that for every 1 psig reduction in compressor output pressure, compressor power consumption will be reduced by approximately 0.5%. How did they find this number?

 

[PJC01]

The unknown variables in the flowrate equation are the area (A), flow coefficient (C), pressure (P), and temperature (R). These variables must be known in order to accurately calculate the flowrate (M). Additionally, the gas density of air (0.7494 lb/ft3) and the conversion factor for minutes to seconds (60s/min) are also necessary for the equation to be applicable to SCFM. It is important to correctly identify and measure these variables in order to obtain accurate results from the equation.