Turbines and Compressors: Example Problems

Try to solve these problems before watching the solutions in the screencasts.

Example Problem 1

Two turbines are used to expand an ideal gas from 1.0 MPa and 650 K to produce work. Turbine A has an efficiency of 70%, and turbine B has an efficiency of 50%. Under a certain set of operating conditions, the exit temperature of turbine A is measured to be the same as the exit temperature of turbine B. Under these conditions, which turbine is producing more work? Explain.

Example Problem 2

An ideal gas at 25°C is continuously compressed adiabatically from 2.0 bar to 7.0 bar pressure. The feed flow rate is 1.0 mol/min. The heat capacity (CP) is constant and equal to 25 J mol-1 K-1. What is the temperature of the gas exiting the compressor when the compression is:
  1. Reversible?
  2. Irreversible and the work required is 20% more than required for the reversible process to the same exit pressure?