Question

Steam leaves the boiler of a simple steam power cycle at 4000 kPa and 600°C. It exits the turbine at 20 kPa as saturated steam. It then exits the condenser as saturated water. What type of process is occurring in the turbine?

a) Isothermal expansion
b) Isentropic expansion
c) Adiabatic expansion
d) Constant volume expansion

Answer 1

The process occurring in the turbine is likely isentropic expansion, where no heat is exchanged with the surroundings and no entropy is generated within the system. Option B is correct.

Step-by-step explanation:

The process occurring in the turbine as described, where steam exits the turbine at 20 kPa as saturated steam after leaving the boiler, is likely to be isentropic expansion. An isentropic process is one that is both adiabatic and reversible, meaning no heat is exchanged with the surroundings and no entropy is generated within the system.

This kind of process is a good approximation for the ideal behavior of steam turbines where the aim is to achieve maximum efficiency by not losing heat to the surroundings while expanding the steam.

The type of process occurring in the turbine can be determined by analyzing the steam properties at different stages. The steam leaves the boiler at high pressure and high temperature, and then exits the turbine at a lower pressure as saturated steam.

Since the steam is expanding and losing pressure while maintaining constant entropy, the process in the turbine is an isentropic expansion. This means that the steam is expanding in the turbine without any external heat transfer or energy loss.