Modern Engineering Thermodynamics

2 CHAPTER 1: The Beginning
Energy is one of the most useful concepts ever developed. 1 Energy can be possessed by an object or a system,
suchasacoiledspringorachemicalfuel,anditmaybetransmitted through empty space as electromagnetic
radiation. The energy contained in a system is often only partially available for use. This, called the available
energy of the system, is treated in detail later in this book.
One of the basic laws of thermodynamics is that energy is conserved. This law is so important that it is called
the first law of thermodynamics. It states that energy can be changed from one form to another, but it cannot
be created or destroyed (that is, energy is “conserved”). Some of the more common forms of energy
are: gravitational, kinetic, thermal, elastic, chemical, electrical, magnetic, and nuclear. Our ability to efficiently
convert energy from one form into a more useful form has provided much of the technology we
have today.
1.2 WHY IS THERMODYNAMICS IMPORTANT TODAY?
The people of the world consume 1.06 cubic miles of oil each year as an energy source for a wide variety of uses
such as the engines shown in Figures 1.1 and 1.2. 2 Coal, gas, and nuclear energy provide additional energy,
equivalent to another 1.57 mi 3 of oil, making our total use of exhaustible energy sources equal to 2.63 mi 3 of oil
every year. We also use renewable energy from solar, biomass, wind (see Figure 1.3), and hydroelectric, in
amounts that are equivalent to an additional 0.37 mi 3 of oil each year. This amounts to a total worldwide
FIGURE 1.1
A cutaway of the Pratt & Whitney F-100 gas turbine engine.
FIGURE 1.2
Corvette engine.
1 The word energy is the modern form of the ancient Greek term energeia, which literally means “in work” (en = in and ergon = work).
2 One cubic mile of oil is equal to 1.1 trillion gallons and contains 160 quadrillion (160 × 10 15 ) kilojoules of energy.