Repeat Prob. 9-20 for helium gas.

PROBLEM: Air expands isentropically from 1.5 MPa and 60°C to 0.4 MPa. Calculate the ratio of the initial to final speed of sound.

Solution to 63P

Step 1</p>

We need to find the ratio of initial speed to final speed of sound if helium expands from 1.5MPa at 600C to 0.4MPa isentropically.

To calculate we need to use the equation for isentropic flow applied to ideal gases.

P=pressure

V=volume

𝝲=specific heat of the gas

T =temperature

Step 2</p>

𝝲 for helium gas =1.66

Step 2</p>

Thus

Thus

T2=196.25 K