1. Part I: Thermodynamics
低溫熱流學
Part I: Thermodynamics
授課教師：施陽正　博士
97年9月

2. 1
CHAPTER
Introduction and Overview

3. 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

4. 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

5. 1. Introduction to Thermal-Fluid Sciences
Application Areas of Thermal-Fluid Sciences

6. 1. Introduction to Thermal-Fluid Sciences

7. 1. Introduction to Thermal-Fluid Sciences

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

9. 2. Thermodynamics

10. 2. Thermodynamics

11. 2. Thermodynamics

12. 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

13. 3. Heat Transfer

14. 3. Heat Transfer

15. 3. Heat Transfer

16. 3. Heat Transfer

17. 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).

18. 4. Fluid Mechanics

19. 4. Fluid Mechanics

20. 4. Fluid Mechanics

21. 4. Fluid Mechanics

22. 5. A Note on Dimensions and Units

23. 5. A Note on Dimensions and Units

24. 5. A Note on Dimensions and Units

25. 5. A Note on Dimensions and Units

26. 5. A Note on Dimensions and Units

27. 5. A Note on Dimensions and Units

28. 5. A Note on Dimensions and Units

29. 5. A Note on Dimensions and Units

30. 5. A Note on Dimensions and Units

31. 5. A Note on Dimensions and Units
Dimensional Homogeneity

32. 5. A Note on Dimensions and Units

33. 5. A Note on Dimensions and Units

34. 6. Closed and Open System

35. 6. Closed and Open System

36. 6. Closed and Open System

37. 6. Closed and Open System

38. 6. Closed and Open System

39. 6. Closed and Open System

40. 7. Properties of a System

41. 7. Properties of a System

42. 7. Properties of a System

43. 7. Properties of a System

44. 8. Solving Engineering Problems

45. 9. Problem Solving Technique
Step1: Problem Statement
Step2: Schematic
Step3: Assumptions
Step4: Physical Laws
Step5: Properties
Step6: Calculations
Step7: Reasoning,Verification,and Discussion

46. 9. Problem Solving Technique

47. 9. Problem Solving Technique

48. 9. Problem Solving Technique
A Remark on Significant Digits

49. 10. Conservation of Mass Principle

50. 10. Conservation of Mass Principle

51. 10. Conservation of Mass Principle
Mass and Volume Flow Rates

52. 10. Conservation of Mass Principle

53. 10. Conservation of Mass Principle

54. 10. Conservation of Mass Principle

55. 10. Conservation of Mass Principle

56. 10. Conservation of Mass Principle

57. 10. Conservation of Mass Principle

58. 10. Conservation of Mass Principle

59. 10. Conservation of Mass Principle
Mass Balance for Steady-Flow Processes

60. 10. Conservation of Mass Principle

61. 10. Conservation of Mass Principle

62. 10. Conservation of Mass Principle
Special Case:Incompressible Flow ( =constant)
Steady Incompressibe Flow
(single stream):

63. 10. Conservation of Mass Principle

64. 2
CHAPTER
Basic Concepts of Thermodynamics

65. I. Basic Concepts of Thermodynamics
Introduction 前言.
Dimensions and Units 單位與因次
Closed and Open Systems 密閉系統或開放系統
Forms of Energy 能量的形式
Properties of a system 性質
State and Equilibrium 狀態與平衡
Processes and Cycles 過程與循環
State Postulate 狀態假說
Pressure and Temperature 壓力與溫度

66. 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.

67. 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)

68. 2. Dimensions and Units Dimension SI Unit IP Unit Length, L m ft
Time, t
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

69. 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

70. 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.

71. 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.

72. 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.

73. 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.

74. 4. Forms of Energy Energy – Stored energy and Transient energy
Internal energy (內能)
Potential energy (位能)
Kinetic energy (動能)
Chemical energy (化學能)
Nuclear (atomic) energy (核能或原子能)
Transient energy (轉移能或暫態能)
Heat (熱)
Work (功)

75. 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

76. 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) .

77. 5. Properties of a System
Extensive properties per unit mass are called specific properties.
Specific volume, v=V/m
Specific total energy, e=E/m
Specific internal energy, u=U/m
Specific enthalpy, h=H/m
Specific entropy, s=S/m

78. 6. State and Equilibrium

79. 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.

80. 6. State and Equilibrium

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

82. 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)

83. Quasi-equilibrium

84. 7. Processes and Cycles

85. 7. Processes and Cycles Process Property held constant
isobaric pressure
isothermal temperature
isochoric volume
isentropic entropy (see Chapter 6)
Constant Pressure Process
Water F
System
Boundary

86. 7. Processes and Cycles
A process with identical end states is called a cycle (Fig.1-30)
Process B A 1 2 P V

87. 9. Pressure and Temperature

88. 9. Pressure and Temperature

89. 9. Pressure and Temperature

90. 9. Pressure and Temperature
Two bodies are in thermal equilibrium when they have reached the same temperature.
Zeroth law of thermodynamics (熱力學第零定律)
If two bodies are in thermal equilibrium with a third body, they are also in thermal equilibrium with each other.

91. 3
CHAPTER
Properties of Pure Substances

92. II. Properties of Pure Substances
Phase of a pure substance 純物質之相
Phase change processes of pure substances 純物質之相變化
Property diagrams for phase change processes 相變過程之性質圖
Vapor Pressure and Phase Equilibrium 蒸氣壓與相平衡
Property Tables 熱力性質表

93. II. Properties of Pure Substances
The ideal-gas equation of state 理想氣體狀態方程式
Compressibility factor – a measure of deviation from ideal-gas behavior 壓縮因子
Other Equations of State 其他氣體狀態方程式
10. Internal Energy, Enthalpy, and Specific Heats of Ideal Gases
內能、焓與比熱

94. 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.

95. 2. Phase of a Pure Substance
Pure substance have three principal phases – solid, liquid, and gas.

96. 3. Phase Change Processes of Pure Substances
Compressed liquid and saturated liquid.
Saturated vapor and superheated vapor.
Saturation temperature and saturation pressure.

97. 3. Phase Change Processes of Pure Substances

98. 4. Property Diagrams for Phase Change Processes
The T-v diagram

99. 4. Property Diagrams for Phase Change Processes
The T-v diagram

100. 4. Property Diagrams for Phase Change Processes
The P-v diagram

101. 4. Property Diagrams for Phase Change Processes
The P-T diagram

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

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

104. 5. Vapor Pressure and Phase Equilibrium

105. 5. Vapor Pressure and Phase Equilibrium

106. 6. Property Tables
Enthalpy – a combination property

107. 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

108. 6. Property Tables Example 2-1 Example 2-2
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.

109. 6. Property Tables 1b. Saturated Liquid-Vapor Mixture
Quality x is defined as

110. 6. Property Tables 1b. Saturated Liquid-Vapor Mixture
y may be replaced by any of the variables v, u, h, or s.

111. 6. Property Tables
2. Superheated Vapor

112. 6. Property Tables 3. Compressed Liquid
y may be replaced by any of the variables v, u, h, or s.

113. 7. Ideal-Gas Equation of State
Specific volume
[m3/kg]
Temperature
[℃, K]
Pressure
[kPa]
Gas constant
[kJ/(kg K)]
or kPa.m3/(kg K)

114. 7. Ideal-Gas Equation of State
Universal gas constant
[℃, K]
Molar mass
[g/(gmol)]
or [kg/(kmol)]

115. 7. Ideal-Gas Equation of State

116. 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.

117. Is Water Vapor an Ideal Gas ?

118. Z is called compressibility factor (壓縮性因子)
For ideal gas: Z = 1

120. Tr: reduced temperature
Pr: reduced pressure

121. 8. Other Equations of State
Van der Waals Equation of State
Beattie-Bridgeman Equation of State
Benedict-Webb-Rubin Equation of State

122. 8. Other Equations of State

123. 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

124. 10. Internal Energy, Enthalpy, and Specific Heats of Ideal Gases
For an ideal gas

125. 10. Internal Energy, Enthalpy, and Specific Heats of Ideal Gases
Fig. 3-56
Ideal-gas Cp for
some gases.
Table A-2 (p.845)

126. 10. Internal Energy, Enthalpy, and Specific Heats of Ideal Gases
For small temperature intervals, specific heat may be assumed to vary linearly with temperature.

127. 10. Internal Energy, Enthalpy, and Specific Heats of Ideal Gases
Specific-heat relations of ideal gases.
specific heat ratio,

128. 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.

129. 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:

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

131. 4
CHAPTER
Energy Transfer by Heat, Work, and Mass

132. Energy Transfer by Heat, Work, and Mass
Heat Transfer
Energy Transfer by Work
Mechanical Forms of Work
Nonmechanical Forms of Work
Flow Work and the Energy of a Flowing Fluid

133. 1. Heat Transfer
Energy can cross the boundary of a closed system in two distinct forms: heat and work.

134. 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.

135. 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.

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

137. 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

138. 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.

139. 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 (傳導), convection (對流), and radiation (輻射).

140. 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.

141. 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

142. (+)
(–)

143. 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.)

144. path functions – inexact differentials (d)
point functions – exact differentials (d)

145. 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.

146. 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?

147. 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?

148. 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?

149. 3. Mechanical Forms of Work
Moving boundary work: (kJ)
Shaft work: (kJ)
Spring work: (kJ)

150. Moving Boundary Work

151. Moving Boundary Work

152. 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.

153. 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.

154. Polytropic process (多變過程) (Pvn = constant)

155. Spring Work

156. 4. Nonmechanical Forms of Work
Electrical work: (kJ)

157. 5. Flow Work and the Energy of a Flowing Fluid

158. Total Energy of a Flowing Fluid

159. Energy Transport by Mass

161. 5
CHAPTER
The First Law of Thermodynamics

162. The First Law of Thermodynamics
Energy Balance for Closed Systems
Energy Balance for Steady-Flow Systems
Some Steady-Flow Engineering Devices
Energy Balance for Unsteady-Flow Processes

163. 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.

164. Energy Balance

165. Energy Balance

166. Energy Balance

167. 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

168. Net work done in all form
Net change in total energy of system
Net heat transfer across system boundaries

169. For a stationary closed systems

170. For a cyclic process

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

172. 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

173. 3. Energy Balance for Steady-Flow Systems
Mass balance for steady-flow systems:

174. Energy balance for steady-flow systems:

175. 4. Some Steady-Flow Engineering Devices
Nozzles and Diffusers
Turbines and Compressors
Throttling Valves
Mixture Chambers
Heat Exchangers
Pipe and Duct Flow

176. (Fig. 4-25)

177. Nozzle and Diffuser

178. 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.

179. Turbines and Compressors

180. 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.

181. 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 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.

182. Throttling Valves

183. The temperature of an ideal gas does not change during
a throttling(h =constant) process since h = h (T)

184. Joule-Thomson Coefficient

186. 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.

187. Mixing Chamber

188. Heat Exchanger
The heat transfer associated with a heat exchanger may be zero or nonzero depending on how the system is selected

189. Pipe and Duct Flow .