# 04.09 Turbine calculations

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### General Procedure of Solving for Turbine Efficiency

General procedure to solve for steam turbine efficiency. (LearnChemE.com, 5min) This video outlines the procedure without actually solving any specific problem. It shows how inefficiency affects the T-S diagram and how to compute the actual temperature at the turbine outlet.
Comprehension Questions:
1. In this video, the entropy at the outlet of the actual turbine is to the right of the entropy for the reversible turbine. Suppose we were interested in the T-S diagram for a 75% efficient compressor. Would the outlet entropy of the actual compressor be to the right of the entropy for the reversible turbine, to the left, or about the same? Explain.
2. In the video, Prof. Falconer states that the outlet entropy must be the same as the inlet entropy because the process is reversible and one other property. What is the other requirement for the turbine to be isentropic? Explain.
3. Will inefficiency in the turbine always cause the temperature at the outlet to be higher than the inlet? Explain.

### Sample Calculation of Solving for Turbine Efficiency

Entropy Balances: Solving for Turbine Efficiency Sample Calculation. (uakron.edu, 10min) Steam turbines are very common in power generation cycles. Knowing how to compute the actual work, reversible work, and compare them is an elementary part of any engineering thermodynamics course.

Comprehension Questions:

1. An adiabatic turbine is supplied with steam at 2.0 MPa and 600°C and it exhausts at 98% quality and 24°C. (a) Compute the work output per kg of steam.(b) Compute the efficiency of the turbine.

2. A Rankine cycle operates on steam exiting the boiler at 7 MPa and 550°C and expanding to 60°C and 98% quality. Compute the efficiency of the turbine.