Chapter 10

VAPOR AND COMBINED POWER CYCLES

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n Chap. 9 we discussed gas power cycles for which the
working fluid remains a gas throughout the entire cycle. In
this chapter, we consider vapor power cyclesin which the
working fluid is alternatively vaporized and condensed. We
also consider power generation coupled with process heating
called cogeneration.
The continued quest for higher thermal efficiencies has
resulted in some innovative modifications to the basic vapor
power cycle. Among these, we discuss the reheatand regen-
erative cycles,as well as combined gas–vapor power cycles.
Steam is the most common working fluid used in vapor
power cycles because of its many desirable characteristics,
such as low cost, availability, and high enthalpy of vaporiza-
tion. Therefore, this chapter is mostly devoted to the discus-
sion of steam power plants. Steam power plants are commonly
referred to as coal plants, nuclear plants,or natural gas
plants,depending on the type of fuel used to supply heat to
the steam. However, the steam goes through the same basic
cycle in all of them. Therefore, all can be analyzed in the
same manner.

Objectives

The objectives of Chapter 10 are to:

• Analyze vapor power cycles in which the working fluid is
  alternately vaporized and condensed.


• Analyze power generation coupled with process heating
  called cogeneration.


• Investigate ways to modify the basic Rankine vapor power
  cycle to increase the cycle thermal efficiency.


• Analyze the reheat and regenerative vapor power cycles.


• Analyze power cycles that consist of two separate cycles
  known as combined cycles and binary cycles.