A Pitot-static tube is used to measure the velocity of helium in a pipe. The temperature and pressure are 44oF and 24 psia. A water manometer connected to the Pitot-static tube indicates a reading of 3.0 in. (a) Determine the helium velocity. (b) Is it reasonable to consider the flow as incompressible?

Part A:

Part B:

Ma=0.0737

Since Ma<0.3, it means the flow is in compressible.

Explanation:

Part A:

According to Bernoulli equation:

Velocity will become:

.........Eq (1)

Now, can be calculated from the specific weight of water and helium

Since the specific weight of helium is much smaller than specific weight of water we can neglect the specific weight of helium.

=

For water,

h=3.0 in

Density of helium:

T=460+44=504 degree R

R=

From Eq (1):

Part B:

Checking Ma:

c is speed of sound:

k=1.66 for helium, In ideal gases:

Since Ma<0.3, it means the flow is in compressible.

e) none of the above answers are correct

explanation:

newton's third law, for every action there is an equal and opposite reaction.