Help with mass flow rate of turbine?

[nate9519]

Homework Statement

An turbine expands air at 1300 kPa and 500oC to 100 kPa and 127oC. Air enters the turbine through a 0.2-m2 opening with an average velocity of 50 m/s, and exhausts through a 1-m2 opening. Determine (a) the mass flow rate of air through the turbine

Homework Equations

PV=RT
m dot = (1/v)(V)(A)

The Attempt at a Solution

[/B]
I use PV=RT to get specific volume. (.287 * 773)/1300 = .17065 m^3/kg
I then plug it into the formula for mass flow rate which is (1/.17065)(50)(.2) = 58.6 kg/s
the problem is that the answer is suppose to be 46.9 kg/s but I can see anything I've done wrong. can someone help??

 

[SteamKing]

Homework Statement

An turbine expands air at 1300 kPa and 500oC to 100 kPa and 127oC. Air enters the turbine through a 0.2-m2 opening with an average velocity of 50 m/s, and exhausts through a 1-m2 opening. Determine (a) the mass flow rate of air through the turbine

Homework Equations

PV=RT
m dot = (1/v)(V)(A)

The Attempt at a Solution

[/B]
I use PV=RT to get specific volume. (.287 * 773)/1300 = .17065 m^3/kg
I then plug it into the formula for mass flow rate which is (1/.17065)(50)(.2) = 58.6 kg/s
the problem is that the answer is suppose to be 46.9 kg/s but I can see anything I've done wrong. can someone help??

Did you check what happens at the exhaust end? The air has expanded after going thru the turbine.