# Air in turbine tunnel

1. Aug 13, 2010

### albertwinnie

Newbie here;I have a project where I need to know the formula to find the speed of a known quantity of air in cubic feet per minute going though an orfice.So I can calculate
psf.at.00252v2

2. Aug 13, 2010

### minger

Firstly, $$ft^3/min$$ is not a unit of speed, rather of volumetric flow, typically denoted by the variable, Q. Dividing Q by the cross-sectional area will give you the velocity.

However, aside from that, you've given us nothing. You are posting zero knows in this problem and expect an answer for something. Do you have upstream pressure? Mass flow? What?

3. Aug 14, 2010

### albertwinnie

Thank you for that Minger,,,,,I,m off to the hospital for a scat scan and will post more details when I return.

4. Aug 14, 2010

### albertwinnie

Hi Minger,,,,OK,Back in home,,

air volume=375,000 cfm3

orfice=18,900 ft2

air pressure=20 inches water column

velocity of air = ?

5. Aug 14, 2010

### Integral

Staff Emeritus
Look at the units.

You have flow in
$$\frac {ft^3} {min}$$

and an area in
$$ft^2$$

can you look at that and figure out the operation needed to arrive at a number in

$$\frac {ft} {min}$$ ?

6. Aug 14, 2010

### albertwinnie

What am I missing ?

7. Aug 14, 2010

### Staff: Mentor

Those numbers look odd...