Part I: Thermodynamics

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????? Part I Thermodynamics ??????? ?? 97?9?
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CHAPTER
Introduction and Overview
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I. Introduction and Overview

• Introduction to Thermal-Fluid Sciences
• Thermodynamics
• Heat Transfer
• Fluid Mechanics
• A Note on Dimensions and Units
• Closed and Open System
• Properties of a System
• Solving Engineering Problems
• Problem Solving Technique
• Conservation of Mass Principle

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1. Introduction to Thermal-Fluid Sciences

• The physical sciences that deal with energy and
  the transfer, transport, and conversion of energy
  are usually referred to as thermal-fluid sciences
  or thermal sciences.
• Thermal-fluid sciences
• Thermodynamics
• Fluid mechanics
• Heat transfer

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1. Introduction to Thermal-Fluid Sciences

• Application Areas of Thermal-Fluid Sciences

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1. Introduction to Thermal-Fluid Sciences
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1. Introduction to Thermal-Fluid Sciences
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2. Thermodynamics

• Thermodynamics can be defined as the science of
  energy.
• First law of thermodynamics
• Second law of thermodynamics

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2. Thermodynamics
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2. Thermodynamics
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2. Thermodynamics
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3. Heat Transfer

• Energy exists in various forms. Heat is the form
  of energy that can be transferred from on system
  to another as a result of temperature difference.
• The science that deals with the determination of
  the rates of such energy transfer is heat
  transfer.
• Heat is transferred by three mechanisms
• Conduction
• Convection
• Radiation

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3. Heat Transfer
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3. Heat Transfer
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3. Heat Transfer
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3. Heat Transfer
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4. Fluid Mechanics

• Fluid mechanics is defined as the science that
  deals with the behavior of fluids at rest (fluid
  statics) or in motion (fluid dynamics).

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4. Fluid Mechanics
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4. Fluid Mechanics
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4. Fluid Mechanics
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4. Fluid Mechanics
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5. A Note on Dimensions and Units
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5. A Note on Dimensions and Units
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5. A Note on Dimensions and Units
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5. A Note on Dimensions and Units
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5. A Note on Dimensions and Units
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5. A Note on Dimensions and Units
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5. A Note on Dimensions and Units
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5. A Note on Dimensions and Units
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5. A Note on Dimensions and Units
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5. A Note on Dimensions and Units

• Dimensional Homogeneity

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5. A Note on Dimensions and Units
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5. A Note on Dimensions and Units
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6. Closed and Open System
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6. Closed and Open System
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6. Closed and Open System
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6. Closed and Open System
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6. Closed and Open System
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6. Closed and Open System
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7. Properties of a System
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7. Properties of a System
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7. Properties of a System
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7. Properties of a System
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8. Solving Engineering Problems
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9. Problem Solving Technique

• Step1 Problem Statement
• Step2 Schematic
• Step3 Assumptions
• Step4 Physical Laws
• Step5 Properties
• Step6 Calculations
• Step7 Reasoning,Verification,and Discussion

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9. Problem Solving Technique
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9. Problem Solving Technique
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9. Problem Solving Technique

• A Remark on Significant Digits

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10. Conservation of Mass Principle
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10. Conservation of Mass Principle
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10. Conservation of Mass Principle

• Mass and Volume Flow Rates

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10. Conservation of Mass Principle
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10. Conservation of Mass Principle
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10. Conservation of Mass Principle

• Conservation of Mass Principle

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10. Conservation of Mass Principle
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10. Conservation of Mass Principle
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10. Conservation of Mass Principle
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10. Conservation of Mass Principle
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10. Conservation of Mass Principle

• Mass Balance for Steady-Flow Processes

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10. Conservation of Mass Principle
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10. Conservation of Mass Principle
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10. Conservation of Mass Principle

• Special CaseIncompressible Flow ( constant)

Steady Incompressibe Flow (single stream)
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10. Conservation of Mass Principle
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2
CHAPTER
Basic Concepts of Thermodynamics
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I. Basic Concepts of Thermodynamics

1. Introduction ??.
2. Dimensions and Units ?????
3. Closed and Open Systems ?????????
4. Forms of Energy ?????
5. Properties of a system ??
6. State and Equilibrium ?????
7. Processes and Cycles ?????
8. State Postulate ????
9. Pressure and Temperature ?????

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1. Introduction

• Thermodynamics is the science of energy and
  entropy.
• The first law of thermodynamics is simply an
  expression of the conservation of energy
  principle, and it asserts that energy is a
  thermodynamic property.
• The second law of thermodynamics asserts that
  energy has quality as well as quantity, and
  actual processes occur in the direction of
  decreasing quality of energy.

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2. Dimensions and Units

• Dimension
• Primary dimensions --mass m, length L, time t,
  temperature T.
• Secondary dimensions -- energy E, volume V
• Units
• English system
• International system (SI)

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2. Dimensions and Units
Dimension SI Unit IP Unit
Length, L m ft
Time, t sec sec
Mass, m kg lbm
Energy, E Joule Btu
Power, W Waltt Btu/hr
Dimension SI Unit IP Unit
density, r kg/m3 lbm/ft3
velocity, v m/sec ft/sec
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2. Dimensions and Units
Multiple Prefix
1012 tera, T
109 giga, G
106 mega, M
103 kilo, k
10-2 centi, c
10-3 milli, m
10-6 micro, m
10-9 nano, n
10-12 pico, p
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3. Closed and Open Systems

• A thermodynamic system, or simply a system, is
  defined as a quantity of matter or a region in
  space chosen for study.
• The mass or region outside the system is called
  the surroundings.
• The real or imaginary surface that separates the
  system from its surrounding is called the
  boundary.

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3. Closed and Open Systems

• A system of fixed mass is called a closed system,
  or control mass. -- Energy, not mass, crosses
  closed-system boundaries.

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3. Closed and Open Systems

• A system that involves mass transfer across its
  boundaries is called an open system, or control
  volume. Mass and energy cross control volume
  boundaries.

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3. Closed and Open Systems

• An isolated system is a general system of fixed
  mass where no heat or work may cross the
  boundaries.
• The thermodynamic relations that are applicable
  to closed and open systems are different.
  Therefore, it is extremely important that we
  recognize the type of system we have before we
  start analyzing it.

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4. Forms of Energy

• Energy Stored energy and Transient energy
• Stored energy (??)
• Internal energy (??)
• Potential energy (??)
• Kinetic energy (??)
• Chemical energy (???)
• Nuclear (atomic) energy (??????)
• Transient energy (???????)
• Heat (?)
• Work (?)

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5. Properties of a System

• Any macroscopic characteristic of a system is
  called a property.
• Pressure, P
• Temperature, T
• Volume, V
• Mass, m
• Density, r
• Energy, E Enthalpy, H Entropy, S

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5. Properties of a System

• The mass-dependent properties of a system are
  called extensive properties (uppercase letters)
  and the others, intensive properties (lowercase
  letters) .

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5. Properties of a System

• Extensive properties per unit mass are called
  specific properties.
• Specific volume, vV/m
• Specific total energy, eE/m
• Specific internal energy, uU/m
• Specific enthalpy, hH/m
• Specific entropy, sS/m

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6. State and Equilibrium
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6. State and Equilibrium

• A system is said to be in thermodynamic
  equilibrium if it maintains thermal, mechanical,
  phase and chemical equilibrium.
• Thermal equilibrium the temperature is the same
  throughout the entire system.
• Mechanical equilibrium there is no change in
  pressure at any point of the system with time.
• Phase equilibrium the mass of each phase
  reaches an equilibrium level and stays there.
• Chemical equilibrium the chemical composition
  does not change with time.

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6. State and Equilibrium
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State Postulate

• The state of a simple compressible system is
  completely specified by two independent,
  intensive properties.

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7. Processes and Cycles

• Any change that a system undergoes from one
  equilibrium state to another is called a process.
  (Fig.1-26)
• When a process proceeds in such a manner that the
  system remains infinitesimally close to an
  equilibrium state at all times, it is called a
  quasi-static, or quasi-equilibrium, process.
  (Fig. 1-29)

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Quasi-equilibrium
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7. Processes and Cycles
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7. Processes and Cycles

• Process Property held constant
• isobaric pressure
• isothermal temperature
• isochoric volume
• isentropic entropy (see Chapter 6)

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7. Processes and Cycles

• A process with identical end states is called a
  cycle. (Fig.1-30)

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9. Pressure and Temperature
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9. Pressure and Temperature
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9. Pressure and Temperature
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9. Pressure and Temperature

• Two bodies are in thermal equilibrium when they
  have reached the same temperature.
• Zeroth law of thermodynamics (???????)
• If two bodies are in thermal equilibrium with a
  third body, they are also in thermal equilibrium
  with each other.

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3
CHAPTER
Properties of Pure Substances
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II. Properties of Pure Substances

1. Pure substance ???
2. Phase of a pure substance ?????
3. Phase change processes of pure substances ???????
4. Property diagrams for phase change processes
   ????????
5. Vapor Pressure and Phase Equilibrium ???????
6. Property Tables ?????

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II. Properties of Pure Substances

• The ideal-gas equation of state ?????????
• Compressibility factor a measure of deviation
  from ideal-gas behavior ????
• Other Equations of State ?????????
• 10. Internal Energy, Enthalpy, and Specific Heats
  of Ideal Gases
• ???????

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1. Pure Substance

• A pure substance has a homogeneous and invariable
  chemical composition and may exist in more than
  one phase. -- Water, nitrogen, helium, and carbon
  dioxide.
• A pure substance does not have to be of a single
  chemical element or compound. A mixture of
  various chemical elements or compounds also
  qualifies as a pure substance as long as the
  mixture is homogeneous. -- Air
• A mixture of two or more phases of a pure
  substance is still a pure substance. a mixture
  of ice and liquid water.

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2. Phase of a Pure Substance

• Pure substance have three principal phases
  solid, liquid, and gas.

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3. Phase Change Processes of Pure Substances

• Compressed liquid and saturated liquid.
• Saturated vapor and superheated vapor.
• Saturation temperature and saturation pressure.

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3. Phase Change Processes of Pure Substances
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4. Property Diagrams for Phase Change Processes

• The T-v diagram

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4. Property Diagrams for Phase Change Processes

• The T-v diagram

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4. Property Diagrams for Phase Change Processes

• The P-v diagram

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4. Property Diagrams for Phase Change Processes

• The P-T diagram

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• P-v-T Surface of a substance that contracts on
  freezing

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• P-v-T Surface of a substance that expands on
  freezing

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5. Vapor Pressure and Phase Equilibrium
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5. Vapor Pressure and Phase Equilibrium
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6. Property Tables

• Enthalpy a combination property

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6. Property Tables
1a. Saturated Liquid and Saturated Vapor States
vf specific volume of saturated liquid vg
specific volume of saturated vapor vfg
difference between vg and vf, vfg vg - vf
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6. Property Tables
Example 2-1 A rigid tank contains 50 kg of
saturated liquid water at 90?. Determine the
pressure in the tank and the volume of the
tank. Example 2-2 A mass of 200 g of saturated
liquid water is completely vaporized at a
constant pressure of 100kPa. Determine (a) the
volume change and (b) the amount of energy added
to the water.
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6. Property Tables
1b. Saturated Liquid-Vapor Mixture

• Quality x is defined as

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6. Property Tables
1b. Saturated Liquid-Vapor Mixture
y may be replaced by any of the variables v, u,
h, or s.
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6. Property Tables
2. Superheated Vapor
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6. Property Tables
3. Compressed Liquid
y may be replaced by any of the variables v, u,
h, or s.
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7. Ideal-Gas Equation of State
Specific volume m3/kg
Temperature ?, K
Pressure kPa
Gas constant kJ/(kg K) or kPa.m3/(kg K)
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7. Ideal-Gas Equation of State
Universal gas constant ?, K
Molar mass g/(gmol) or kg/(kmol)
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7. Ideal-Gas Equation of State
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7. Ideal-Gas Equation of State
Example 2-3 Determine the mass of the air in a
room whose dimensions are 4mx5mx6m at 100kPa and
25 C.
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Is Water Vapor an Ideal Gas ?
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• Z is called compressibility factor (?????)
• For ideal gas Z 1

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Tr reduced temperature Pr reduced pressure
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8. Other Equations of State

• Van der Waals Equation of State
• Beattie-Bridgeman Equation of State
• Benedict-Webb-Rubin Equation of State

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8. Other Equations of State
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9. Specific Heats

• The specific heat is defined as the energy
  required to raise the temperature of a unit mass
  of a substance by one degree.
• Specific heat at constant volume Cv
• Specific heat at constant pressure Cp

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10. Internal Energy, Enthalpy, and Specific Heats
of Ideal Gases

• For an ideal gas

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10. Internal Energy, Enthalpy, and Specific Heats
of Ideal Gases

• Fig. 3-56
• Ideal-gas Cp for
• some gases.
• Table A-2 (p.845)

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10. Internal Energy, Enthalpy, and Specific Heats
of Ideal Gases

• For small temperature intervals, specific heat
  may be assumed to vary linearly with temperature.
  

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10. Internal Energy, Enthalpy, and Specific Heats
of Ideal Gases

• Specific-heat relations of ideal gases.
• specific heat ratio,

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10. Internal Energy, Enthalpy, and Specific Heats
of Ideal Gases

• Example 3-16
• A piston-cylinder device initially contains air
  at 150kPa and 27C. At this state, the piston is
  resting on a pair of stops, and the enclosed
  volume is 400L. The mass of the piston is such
  that a 350 kPa pressure is required to move it.
  The air is now heated until its volume has
  doubled. Determine (a)the final temperature,
  (b)the work done by the air, and (c)the total
  heat added.

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10. Internal Energy, Enthalpy, and Specific Heats
of Solids and Liquids

• For incompressible substances (liquids and
  solids), both the constant-pressure and
  constant-volume specific heats are identical and
  denoted by C

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10. Internal Energy, Enthalpy, and Specific Heats
of Solids and Liquids
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4
CHAPTER
Energy Transfer by Heat, Work, and Mass
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Energy Transfer by Heat, Work, and Mass

1. Heat Transfer
2. Energy Transfer by Work
3. Mechanical Forms of Work
4. Nonmechanical Forms of Work
5. Flow Work and the Energy of a Flowing Fluid

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1. Heat Transfer

• Energy can cross the boundary of a closed system
  in two distinct forms heat and work.

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• Heat is defined as the form of energy that is
  transferred between two systems (or a system and
  its surroundings) by virtue of a temperature
  difference.

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• Several phrases which are in common use today
  such as heat flow, heat addition, heat
  rejection, heat removal , heat gain, heat loss,
  heat storage, heat generation, electrical
  heating, resistance heating, heat of reaction,
  specific heat, sensible heat, latent heat, waste
  heat, body heat, are not consistent with the
  strict thermodynamic meaning of the term heat,
  which limits its use to the transfer of thermal
  energy during a process.
• In thermodynamics the term heat simply means heat
  transfer.

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• A process during which there is no heat transfer
  is called an adiabatic process.

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• Heat has energy units, kJ or Btu.
• The amount of heat transferred during the process
  between two states is denoted by Q12 or just Q.
• Heat transfer per unit mass of a system is
  denoted q and is determined from

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• The heat transfer rate (the amount of heat
  transferred per unit time) is denoted
• The amount of heat transfer during a process is
  determined by
• When heat transfer rate remains constant during a
  process, then.

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• The sign for heat is as follows heat transfer to
  a system is positive, and heat transfer from a
  system is negative.
• Modes of heat transfer
• Heat can be transferred in three different ways
  conduction (??), convection (??), and radiation
  (??).

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2. Energy Transfer by Work

• Work, like heat, is an energy interaction between
  a system and its surroundings.
• If the energy crossing the boundary of a closed
  system is not heat, it must be work.
• Work is the energy transfer associated with a
  force acting through a distance.

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• Work is also a form of energy and has energy
  units such as kJ.
• The work done during a process between states 1
  and 2 is denoted W12, or simply W.
• The work done per unit mass of a system is
  defined as
• The work done per unit time is called power

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• Work and heat are interactions between a system
  and its surroundings, and there are many
  similarities between the two
• Both are recognized at the boundaries of the
  system as they cross them. Both heat and work
  are boundary phenomena.
• Systems possess energy, but not heat transfer or
  work. Heat and work are transient phenomena.
• Both are associated with a process, not a state.
  Unlike properties, heat or work has no meaning at
  a state.
• Both are path functions (I.e., their magnitudes
  depend on the path followed during a process as
  well as the end states.)

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• path functions inexact differentials (d)
• point functions exact differentials (d)

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Example 4-1
Burning of a Candle in an Insulated Room A
candle is burning in a well-insulated room.
Taking the room (the air plus the candle) as the
system, determine (a) if there is any heat
transfer during this burning process and (b) if
there is any change in the internal energy of the
system.
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Example 4-2
Heating of a Potato in an Oven A potato that is
initially at room temperature (25C) is being
baked in an oven which is maintained at 200C. Is
there any heat transfer during this baking
process?
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Example 4-3
Heating of an Oven by Work Transfer A
well-insulated electric oven is being heated
through its heating element. If the entire oven,
including the heating element, is taken to be the
system, determine whether this is a heat or work
interaction?
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Example 4-4
Heating of an Oven by Heat Transfer Answer the
question in Example 3-4 if the system is taken as
only the air in the oven without the heating
element?
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3. Mechanical Forms of Work

• Moving boundary work (kJ)
• Shaft work (kJ)
• Spring work (kJ)

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• Moving Boundary Work

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• Moving Boundary Work

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Example 3-7

• Boundary Work during a Constant-Volume
  Process
• A rigid tank contains air at 500 kPa and 150C.
  As a result of heat transfer to the surroundings,
  the temperature and pressure inside the tank drop
  to 65C and 400 kPa, respectively. Determine the
  boundary work done during this process.

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Example 4-7

• Boundary Work during an Isothermal Process
• A piston-cylinder device initially contains 0.4
  m3 of air at 100kPa and 80C. The air is now
  compressed to 0.1 m3 in such a way that the
  temperature inside the cylinder remains constant.
  Determine the work done during this process.

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• Polytropic process (????) (Pvn constant)

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• Spring Work

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4. Nonmechanical Forms of Work

• Electrical work (kJ)

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5. Flow Work and the Energy of a Flowing Fluid

• Flow work

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• Total Energy of a Flowing Fluid

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• Energy Transport by Mass

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5
CHAPTER
The First Law of Thermodynamics
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The First Law of Thermodynamics

1. The First Law of Thermodynamics
2. Energy Balance for Closed Systems
3. Energy Balance for Steady-Flow Systems
4. Some Steady-Flow Engineering Devices
5. Energy Balance for Unsteady-Flow Processes

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1. The First Law of Thermodynamics

• Energy can be neither created nor destroyed.
• First law of thermodynamics, or the conservation
  of energy principle, is based on experimental
  observations.
• During an interaction between a system and its
  surroundings, the amount of energy gained by the
  system must be exactly equal to the amount of
  energy lost by the surroundings.

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Energy Balance
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Energy Balance
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Energy Balance
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2. Energy Balance for Closed Systems

• The first law of thermodynamics, or the
  conservation of energy principle for a closed
  system or a fixed mass, may be expressed as
  follows
• or

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• For a stationary closed systems

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• For a cyclic process

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• Various forms of the first-law relation for
  closed systems.

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Examples

• Example 5-1 Cooling of a Hot Fluid in a Tank
• Example 5-2 Electric Heating of a Gas at
  Constant Pressure
• Example 5-3 Unrestrained Expansion of Water into
  an Evacuated Tank
• Example 5-4 Heating of a Gas in a Tank by
  Stirring
• Example 5-5 Heating of a Gas by a Resistance
  Heater
• Example 5-6 Heating of a Gas at Constant
  Pressure
• Example 5-7 Cooling of an Iron Block by Water

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3. Energy Balance for Steady-Flow Systems

• Mass balance for steady-flow systems

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• Energy balance for steady-flow systems

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4. Some Steady-Flow Engineering Devices

• Nozzles and Diffusers
• Turbines and Compressors
• Throttling Valves
• Mixture Chambers
• Heat Exchangers
• Pipe and Duct Flow

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• (Fig. 4-25)

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Nozzle and Diffuser
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Example 5-11
Deceleration of Air in a Diffuser Air at 10C and
80kPa enters the diffuser of a jet engine
steadily with a velocity of 200m/s. The inlet
area of the diffuser is 0.4 m2. The air leaves
the diffuser with a velocity that is very small
compared with the inlet velocity. Determine (a)
the mass flow rate of the air and (b) the
temperature of the air leaving the diffuser.
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Turbines and Compressors
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Example 5-13
Compressing Air by a Compressor Air at 100kPa and
280K is compressed steadily to 600kPa and 400K.
The mass-flow rate of the air is 0.02 kg/s, and a
heat loss of 16kJ/kg occurs during the process.
Assuming the changes in kinetic and potential
energies are negligible, determine the necessary
power input to the compressor.
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Example 5-14

• Power Generation by a Steam Turbine
• The power output of an adiabatic gas turbine is
  5MW, and the inlet and the exit conditions of the
  hot gases are as indicated in Fig.4-30. The gases
  can be treated as air.
• Compare the magnitudes of Dh, Dke, and Dpe.
• Determine the work done per unit mass of hot
  gases.
• Calculate the mass flow rate of the steam.

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Throttling Valves
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The temperature of an ideal gas does not change
during a throttling(h constant) process since h
h (T)
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Joule-Thomson Coefficient
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Example 5-15
Expansion of R-134a in a Refrigerator R-134a
enters the capillary tube of a refrigerator as
saturated liquid at 0.8MPa and is throttled to a
pressure of 0.12MPa. Part of the refrigerant
evaporates during this process and the
refrigerant exists as a saturated liquid-vapor
mixture at the final state. Determine the
temperature drop of the refrigerant during this
process.
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Mixing Chamber
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Heat Exchanger
The heat transfer associated with a heat
exchanger may be zero or nonzero depending on how
the system is selected
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Pipe and Duct Flow