1. Dr. Owen Clarkin School of Mechanical & Manufacturing Engineering Summary of Energy Topics Chapter 1: Thermodynamics / Energy Introduction Chapter 2: Systems & Processes Chapter 3: Work, Energy, Temperature & Heat Chapter 4: Work Processes of Closed Systems Chapter 5: Thermodynamic Properties Chapter 6: Steam Tables Chapter 7: Ideal Gases Chapter 8: Conservation of Mass & Energy Chapter 9: 1 st Law of Thermodynamics Chapter 10: Steady Flow Energy Equation Chapter 11: Heat Engines and Reversibility Chapter 12: 2 nd Law of Thermodynamics Chapter 13: Entropy Chapter 14: General Energy

2. 2 nd Law of Thermodynamics Dr. Owen Clarkin School of Mechanical & Manufacturing Engineering

3. 2 nd Law of Thermodynamics The 1 st law is an expression involving the general principle of Conservation of Energy. The 2 nd law cannot be stated as concisely as that of the first. The 2 nd law of thermodynamics is an expression of the tendency that over time, differences in temperature, pressure, and chemical potential equilibrate in an isolated physical system. The 2 nd law of thermodynamics states that the entropy of an isolated system never decreases Dr. Owen Clarkin School of Mechanical & Manufacturing Engineering Arrow of time

4. 2 nd Law of Thermodynamics Dr. Owen Clarkin School of Mechanical & Manufacturing Engineering

5. 2 nd Law of Thermodynamics The 2 nd law deduces the principle of the increase of entropy and explains the phenomenon of irreversibility in nature, hence the 1 st law led to the definition of energy E, and now the 2 nd law defines the property Entropy S. Entropy is a thermodynamic property that can be used to determine the energy not available for useful work in a thermodynamic process, such as in energy conversion. 2 nd law prohibits a perpetual motion machine of the second type (gains energy from environment). Dr. Owen Clarkin School of Mechanical & Manufacturing Engineering

6. 2 nd Law of Thermodynamics 2 nd Law: Directional Law Ice melting in a warm room is a common example of increasing entropy Kettle continuing to cool below surrounding temperature Dr. Owen Clarkin School of Mechanical & Manufacturing Engineering

7. 2 nd Law of Thermodynamics STATEMENTS The second law of thermodynamics may be expressed in many specific ways, the most prominent classical statements Variation of Clausius’ Statement: Spontaneously, heat cannot flow from cold regions to hot regions without external work being performed on the system, which is evident of refrigeration, by an external agent, a compressor. Dr. Owen Clarkin School of Mechanical & Manufacturing Engineering

8. 2 nd Law of Thermodynamics STATEMENTS Kelvin Statement: No process is possible in which the sole result is the absorption of heat from a reservoir and its complete conversion into work. –This means it is impossible to extract energy by heat from a high- temperature energy source and then convert all of the energy into work. –Thus, a heat engine with 100% efficiency is thermodynamically impossible. –Note that it is possible to convert heat completely into work, such as the isothermal expansion of ideal gas, but the volume of the gas increases and never goes back without outside interference. Dr. Owen Clarkin School of Mechanical & Manufacturing Engineering