1. ENGR 2213 Thermodynamics F. C. Lai School of Aerospace and Mechanical Engineering University of Oklahoma

2. First Law of Thermodynamics E: total energy includes kinetic energy, potential energy and other forms of energy All other forms of energy are lumped together as the internal energy U. Internal energy U is an extensive property. Specific internal energy u = U/m is an intensive property Closed Systems

3. Energy Analysis for a Control Volume Conservation of Mass Net Change in Mass within CV Total Mass Entering CV Total Mass Leaving CV = - Steady State

4. Steady-Flow Process Conservation of mass Conservation of energy

5. Steady-Flow Process Conservation of mass Conservation of energy For single-stream steady-flow process

6. Uniform-Flow Process Conservation of Mass Conservation of Energy + (m 2 u 2 – m 1 u 1 ) CV

7. Second Law of Thermodynamics It is impossible for any device that operates on a cycle to receive heat from a single reservoir and produce an equivalent amount of work. No heat engine can have a thermal efficiency of 100% Kelvin-Planck Statement The impossibility of having 100% efficiency heat engine is not due to friction or other dissipative effects.

8. Second Law of Thermodynamics It is impossible to construct a device that operates on a cycle and produce no effect other than the transfer of heat from a low-temperature body to a high-temperature body. Clausius Statement Equivalence of the two statements A violation of one statement leads to the violation of the other statement.

9. Second Law of Thermodynamics Carnot Principles 1.The efficiency of an irreversible heat engine is always less than that of a reversible one operating between the same two reservoirs. 2.The efficiencies of all reversible heat engines operating between the same two reservoirs are the same. A violation of either statement results in the Violation of the second law of thermodynamics.

10. Entropy Change of an Ideal Gas T ds = du + p dv For an ideal gas, du = c v dT, pv = RT

11. Entropy Change of an Ideal Gas T ds = dh - v dp For an ideal gas, dh = c p dT, pv = RT

12. Isentropic Processes of Ideal Gases 1. Constant Specific Heats (a) (b)

13. Isentropic Processes of Ideal Gases 1. Constant Specific Heats R = c p – c v k = c p /c v R/c v = k – 1 (a)

14. Isentropic Processes of Ideal Gases 1. Constant Specific Heats R = c p – c v k = c p /c v R/c p = (k – 1)/k (b)

15. Isentropic Processes of Ideal Gases 1. Constant Specific Heats Polytropic Processes pV n = constant n = 0 constant pressure isobaric processes n = 1 constant temperature isothermal processes n = k constant entropy isentropic processes n = ±∞ constant volume isometric processes p 1 V 1 k = p 2 V 2 k

16. Isentropic Processes of Ideal Gases 2. Variable Specific Heats Relative Pressure p r = exp[sº(T)/R] ► is not truly a pressure ► is a function of temperature

17. Isentropic Processes of Ideal Gases 2. Variable Specific Heats Relative Volume v r = RT/p r (T) ► is not truly a volume ► is a function of temperature

18. Work reversible work in closed systems reversible work associated with an internally reversible process an steady-flow device ► The larger the specific volume, the larger the reversible work produced or consumed by the steady-flow device.

19. Ideal Rankine Cycles T S 1 2 3 4 Process 1-2: isentropic compression in a pump Process 2-3: constant-pressure heat addition in a boiler Process 3-4: isentropic expansion in a turbine Process 4-1: constant-pressure heat rejection in a condenser Turbine Boiler Condenser Pump 1 2 3 4

20. Ideal Reheat Rankine Cycles T S 1 2 3 4 Turbine Boiler Condenser Pump 1 2 3 4 Boiler Condenser Pump 1 2 3 6 4 5 T S 1 2 3 4 5 6

21. Ideal Regenerative Rankine Cycles 1 2 3 7 4 5 6 P 1 Turbine Boiler Condenser P 2 FWH T S 1 2 3 4 5 7 6 Open Feedwater Heater

22. Ideal Regenerative Rankine Cycles Closed Feedwater Heater 1 2 3 7 4 5 6 8 Trap TurbineBoiler Condenser P FWH y 1-y T S 1 2 3 4 5 7 68 y 1-y

23. Otto Cycles Nikolaus A. Otto (1876) – four-stroke engine Beau de Rochas (1862)

24. Diesel Cycles Rudolph Diesel (1890)

25. Brayton Cycles