Displacement volume

The heat engine cycle performance analysis is carried out from the information available at certain convenient state points in the cycle. The parameters needed at the state points are pressure, temperature, volume, and entropy. If two parameters are known at two state points, then the unknown parameters are usually obtained from the process that the working fluid undergoes between the two state points (such as constant pressure, isentropic, etc.) and the laws of thermodynamics. Discussions of the laws of thermodynamics and efficiency analysis of heat engine cycles are beyond the scope of this book. Only a general introduction to the heat engine cycles of interest will be given.

Prior to continuing the discussion on ICEs, a few words about entropy are in order. Entropy is a property that is specified for every equilibrium state of a substance. Like energy, entropy is an abstract concept that is extensively used in thermodynamic analysis. Entropy represents the microscopic disorder or uncertainty of a system. Because entropy is a property, the change in entropy in going from one state to another is the same for all processes. The SI unit for specific entropy is J/K.

The reciprocating engines are considered first in the following section to be followed by a discussion on gas turbines.

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