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Modern Engineering Thermodynamics

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2 CHAPTER 1: The Beginning<br />

Energy is one of the most useful concepts ever developed. 1 Energy can be possessed by an object or a system,<br />

suchasacoiledspringorachemicalfuel,anditmaybetransmitted through empty space as electromagnetic<br />

radiation. The energy contained in a system is often only partially available for use. This, called the available<br />

energy of the system, is treated in detail later in this book.<br />

One of the basic laws of thermodynamics is that energy is conserved. This law is so important that it is called<br />

the first law of thermodynamics. It states that energy can be changed from one form to another, but it cannot<br />

be created or destroyed (that is, energy is “conserved”). Some of the more common forms of energy<br />

are: gravitational, kinetic, thermal, elastic, chemical, electrical, magnetic, and nuclear. Our ability to efficiently<br />

convert energy from one form into a more useful form has provided much of the technology we<br />

have today.<br />

1.2 WHY IS THERMODYNAMICS IMPORTANT TODAY?<br />

The people of the world consume 1.06 cubic miles of oil each year as an energy source for a wide variety of uses<br />

such as the engines shown in Figures 1.1 and 1.2. 2 Coal, gas, and nuclear energy provide additional energy,<br />

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<br />

every year. We also use renewable energy from solar, biomass, wind (see Figure 1.3), and hydroelectric, in<br />

amounts that are equivalent to an additional 0.37 mi 3 of oil each year. This amounts to a total worldwide<br />

FIGURE 1.1<br />

A cutaway of the Pratt & Whitney F-100 gas turbine engine.<br />

FIGURE 1.2<br />

Corvette engine.<br />

1 The word energy is the modern form of the ancient Greek term energeia, which literally means “in work” (en = in and ergon = work).<br />

2 One cubic mile of oil is equal to 1.1 trillion gallons and contains 160 quadrillion (160 × 10 15 ) kilojoules of energy.

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