3 CHAPTER The First Law of Thermodynamics: Closed Systems

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

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

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

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

3-5 Radiation (Fig. 3-10)

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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.

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.

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

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)

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

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

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

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:

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

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:

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:

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

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

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:

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

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