The Carnot cycle is not practical because of:
• The isentropic expansion in a turbine as in the line segment from 3 to 4. A major concern is related to quality of the steam inside the turbine because a high moisture content results in blade erosion.
• The isentropic compression process in a pump from 1 to 2. It is very difficult to design a condenser and transmission line system that precisely control the quality of the vapor to achieve an isentropic compression.
• The two-phase pump-compressor that is required.
A possible cycle to solve some of these problems could be proposed as depicted in Figure 2.7. However, this cycle requires compression (1-2) of the liquid at a very
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high pressure (exceeding 22 MPa for steam), which is not practical. In addition, maintaining a constant temperature above the critical temperature is also difficult since the pressure will have to change continuously. A practical problem is a maximum temperature limitation for the cycle and constraints on metallurgical limitations imposed by materials used within the boiler and turbine.
