1. 3
CHAPTER
The First Law of Thermodynamics: Closed Systems

2. 3-1
Heat Transfer
(Fig. 3-3)

3. 3-2
Adiabatic Process
(Fig. 3-4)

4. Convection: Heat Transfer
3-3
Convection: Heat Transfer
(Fig. 3-8)

5. 3-4
Convection: Cooling
(Fig. 3-9)

6. 3-5
Radiation
(Fig. 3-10)

7. 3-6
Heat and Work
(Fig. 3-15)

8. 3-7
Path Functions
(Fig. 3-16)

9. 3-8
Boundary Work
(Fig. 3-27)

10. 3-9
Net Work per Cycle
(Fig. 3-29)

11. Schematic/Diagram for Ex. 3-8
3-10
Schematic/Diagram for Ex. 3-8
(Fig. 3-31)

12. Schematic/Diagram for Ex. 3-9
3-11
Schematic/Diagram for Ex. 3-9
(Fig. 3-32)

13. Schematic/Diagram for the Polytropic Process
3-12
Schematic/Diagram for the Polytropic Process
(Fig. 3-33)

14. Schematic/Diagram for Ex. 3-13
(Fig. 3-43)

15. Stretching a Liquid Film
3-14
Stretching a Liquid Film
(Fig. 3-45)

16. 3-15
System Energy Change
(Fig. 3-52)

17. Energy Change for a Cycle
3-16
Energy Change for a Cycle
(Fig. 3-54)

18. Closed-Systems, First-Law
3-17
Closed-Systems, First-Law
(Fig. 3-55)

19. Formal Definitions of Cv and Cp
3-18
Formal Definitions of Cv and Cp
(Fig. 3-72)

20. Specific Heats for Some Gases
3-19
Specific Heats for Some Gases
(Fig. 3-76)

21. Three Ways to Calculate ²u
3-20
Three Ways to Calculate ²u
(Fig. 3-80)

22. Typical Freezing Curve (food)
3-21
Typical Freezing Curve (food)
(Fig. 3-91)

23. 3-22
Chapter Summary
The first law of thermodynamics is essentially an expression of the conservation of energy principle. Energy can cross the boundaries of a closed system in the form of heat or work.
If the energy transfer across the boundaries of a closed system is due to a temperature difference, it is heat; otherwise, it is work.

24. 3-23
Chapter Summary
Heat is transferred in three ways: conduction, convection, and radiation.
Conduction is the transfer of energy from the more energetic particles of a substance to the adjacent less energetic ones as a result of interactions between the particles.
Convection is the mode of energy transfer between a solid surface and the adjacent liquid or gas that is in motion, and it involves the combined effects of conduction and fluid motion.
Radiation is the energy emitted by matter in the form of electromagnetic waves (or photons) as a result of the changes in the electronic configurations of the atoms or molecules.

25. Chapter Summary The three modes of heat transfer are expressed as:
3-24
Chapter Summary
The three modes of heat transfer are expressed as:

26. Chapter Summary Various forms of work are expressed as follows:
3-25
Chapter Summary
Various forms of work are expressed as follows:
Electrical work: (kJ)
Boundary work: (kJ)
Gravitational work (=DPE): (kJ)
Acceleration work (=DKE): (kJ)
Shaft work: (kJ)
Spring work: (kJ)

27. 3-26
Chapter Summary
For the ploytropic process (Pvn = constant) of real gases, the boundary work can be expressed as:

28. 3-27
Chapter Summary
The energy balance for any system undergoing any process can be expressed as:

29. 3-28
Chapter Summary
The energy balances for any system undergoing any process can be expressed in the rate form as:

30. 3-29
Chapter Summary
Taking heat transfer to the system and work done by the system to be positive quantities, the energy balance for a closed system can also be expressed as: where:

31. 3-30
Chapter Summary
For a constant-pressure process, Thus

32. 3-31
Chapter Summary
The amount of energy needed to raise the temperature of a unit of mass of a substance by one degree is called the specific heat at constant volume Cv for a constant-volume process and the specific heat at constant pressure Cp for a constant pressure process. They are defined as:

33. 3-32
Chapter Summary
For ideal gases u, h, Cv, and Cp are functions of temperature alone. The u and h of ideal gases can be expressed as:

34. 3-33
Chapter Summary
For ideal gases Cv, and Cp are related by:

35. 3-34
Chapter Summary
The specific heat ratio k is defined as:

36. 3-35
Chapter Summary
For incompressible substances (liquids and solids), both the constant-pressure and constant-volume specific heats are identical and denoted by C:

37. Chapter Summary The u and h of incompressible substances are given by
3-36
Chapter Summary
The u and h of incompressible substances are given by

38. 3-37
Chapter Summary
The refrigeration and freezing of foods is a major application area of thermodynamics.