Conventional and Alternative Power Generation

1Thermodynamic Systems

1.1 Overview

Thermodynamics is the science relating heat and work transfers and the associated changes in the properties of the working substance within a predefined working system. A thermodynamic system is one that is concerned with the generation of heat and/or work using a working fluid. In this chapter, thermodynamic system behaviour will be described and the changes in properties will be calculated during the different processes encountered in typical engineering applications.

Learning Outcomes

• To understand the basic units and properties of thermodynamic systems.
• To be able to apply the laws of thermodynamics to closed and open systems.
• To be able to apply the first law of thermodynamics and calculate the changes in properties during a process and a cycle.
• To be able to solve problems related to compression and expansion of steam and gases.

1.2 Thermodynamic System Definitions

A thermodynamic system comprises an amount of matter enclosed within a boundary separating it from the outside surroundings.

There are two types of thermodynamic system:

• A closed system has a fixed mass and a flexible boundary.
• An open system has a variable mass (or mass flow) and a fixed boundary.

1.3 Thermodynamic Properties

A thermodynamic property of a substance refers to any quantity whose changes are defined only by the end states and by the process. Examples are the pressure, volume and temperature of the working fluid in the system in Figure 1.1. In addition to these three properties, ...