Question

it is argued that hydraulic turbine cannot have an efficiency of 100 percent even in the absence of irreversible losses due to limitation by the second law of thermodynamics. Do you agree? explain.

Answer 1

2nd law says that total entropy of isolated system can never decrease over time.

efficiency are defined as desired o/p by input.

In case of turbine it is work output/ work input.

Gas expands into turbine to give work output. But from the 2nd law we can say that dS >= 0.

dQ/T >= 0.

dQ >= 0.

Until and unless dQ is not zero the efficiency cannot be 100 percent. This heat transfer do not depend upon any irreversiblity. Therefore 100% efficiency is not possible.