Chapter 16 Lecture

Chapter 16: The Second Law of Thermodynamics

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Goals for Chapter 16

•  To examine the directions of thermodynamic processes.

•  To study heat engines. •  To overview internal combustion engines and

refrigerators. •  To learn and apply the second law of

thermodynamics •  To study the Carnot engine: the most efficient

heat engine.

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The Direction of a Thermodynamic Process

•  Heat flows spontaneously from a "hot" object to a "cold" object.

•  A process can be

•  Spontaneous

•  Non-spontaneous

•  Reversible

•  Irreversible

•  In equilibrium

•  Overall, there can be an increase or decrease in order.

•  Devices can interconvert order/disorder/energy. © 2016 Pearson Education, Inc.

The Heat Engine – Figure 16.1

•  At right, you're looking at a generic heat engine.

•  In this case, the user is "tapping" the natural flow of hot to cold to remove some of the energy flow to do work.

•  Example 16.1 works an example problem of this process and also calculates the efficiency of the engine.

•  Refer to pages 500 and 501 in your text.

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Internal Combustion – Figure 16.4

•  The internal combustion engine is an excellent example of a heat engine using a fuel to generate a hot/cold differential and do pV work during the process.

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Internal Combustion – Figures 16.5 and 16.6

•  The Otto cycle and the Diesel cycle are working examples the heat engine applied to a manufactured device.

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Heat Engines Run "Backward" – Figure 16.6

•  If we consider what we have seen so far from the opposite direction, we can imagine doing work in order to "force" the non-spontaneous flow of energy from a cold reservoir to a hot one.

•  The efficiency of this process is like the heat engine. See pages 503 and 504 in your text.

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Heat Engines Run "Backward" – Figure 16.7 and 16.8 •  The refrigerator and the air conditioner are our

most familiar examples.

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The Second Law – Figure 16.9

•  It is impossible to transfer heat from a cold reservoir to a hot one without doing work.

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Sadi Carnot and an Ideal Heat Engine –Figure 16.11 •  The Carnot Cycle is an ideal model of the heat engine. •  Refer to Examples 16.2 and 16.3 on pages 509 and 510.

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