第一章_制冷与低温原理
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2
Question Answering
• Email your questions to: liwang@me.ustb.edu.cn with your name, class and phone number • I’ll answer you by email or by phone
P.S. Register classes’ email boxes
•Throttling expansion process (节流膨胀过程)
• “节流过程是一降温而不制冷的过程”。节流时有摩擦损失， 是一个不可逆过程，其结果将导致熵的增加。 • 理想气体的内能和焓仅是温度的函数。理想气体节流时
，，
Δu = 0
Δh = 0
ΔT = 0
• 实 际 气 体 节 流 膨 胀 时 的 微 分 节 流 效 应 (Joule-Thomson effect)
7
Applications of R&C Tech.
• Air conditioning (building, domestic, vehicles & industries) • Environment simulation • Food refrigeration, freeze & delivery • Medical and biological applications • Nature gas, hydrogen … liquefaction • Aviation & Spaceflight • ……
R ⎛ ∂v ⎞ ⎜ ⎟ = ⎝ ∂T ⎠ p p
as ,id
κ −1 T = κ p
•Integral isentropic expansion effect(积分等熵效应):
ΔT = ∫ as dp
p1
21
p2
§1.2 Refrigeration of gas adiabatic expansion
•Integral isentropic effect(积分等熵效应):
ΔT = ∫ as dp
p1 p2
for an ideal gas
⎡ Δ T = T1 − T 2 = T1 ⎢1 − ⎢ ⎢ ⎣ ⎛ P2 ⎞ ⎜ ⎜ P ⎟ ⎟ ⎝ 1 ⎠
κ −1 κ
κ −1 κ
⎤ ⎥ ⎥ ⎥ ⎦
T2 ⎛ p2 ⎞ =⎜ ⎟ T1 ⎜ p1 ⎟ ⎝ ⎠
Qo + W = Qh
பைடு நூலகம்
Q0: Heat absorbed from low temp. reservoir W: Work from outside Qh: Heat released (rejected) to high temp. reservoir The equation obeys the 1st and the 2nd laws of thermodynamics simultaneously
Principles of Refrigeration & Cryogenics
制冷与低温原理
王 立 Phone：62334425 Email：Liwang@me.ustb.edu.cn
1
Text and Reference Books
Text book
• 陈光明,陈国邦，制冷与低温技术原理（第二版）， 机械工业出版社，北京，2004
6
Exordium（绪论） • Refrigeration & cryogenic technology The tech. to get temperature artificially below the temperature of circumstances and to keep it. • Temperature range of refrigeration >120k/-153℃ • Temperature range of cryogenics <120k/-153℃
19
§1.2 Refrigeration of gas adiabatic expansion
• Isentropic (等熵) expansion = reversible adiabatic expansion 可逆绝热膨胀 • Gas expansion through an expander(膨胀机)
hdm = dU
式中，U为容器内气体总内能。
dU = d (mu ) = mdu + udm
经推导变换
T2 ⎛ p2 ⎞ =⎜ ⎟ T1 ⎜ p1 ⎟ ⎝ ⎠
κ −1 κ
结果与有外功输出的可逆绝热(等熵)膨胀过程相同。
24
§1.2 Refrigeration of gas adiabatic expansion
Reference books
• 吴业正，制冷与低温技术原理，高等教育出版社， 北京，2004 • 吴业正，制冷原理与设备，西安交通大学出版社， 西安，1987 • Thomas M. Flynn, Cryogenic engineering (Second edition), Marcel Dekker, Inc. , New York, NY, 2005
5
Content
• Chapter 4: Gas refrigeration & liquefaction (液化) cycles 气体制冷与液化循环 • Chapter 5: Principles air/gas separation 气体分离原理 • Chapter 6: Entropy & exergy analysis 熵与“火用”分析
20
§1.2 Refrigeration of gas adiabatic expansion
•Differential isentropic expansion effect:
⎛ ∂T ⎞ T ⎛ ∂v ⎞ as = ⎜ ⎜ ∂p ⎟ = c ⎜ ∂T ⎟ ⎟ ⎠p ⎝ ⎠s p ⎝
for an ideal gas
3
Homework - 0
• Read the textbook, before/after the classes, word by word carefully and thoughtfully.
4
Content
• Exordium（绪论） • Chapter 1: Thermodynamic foundations of refrigeration(制冷) & cryogenics(低温) 制冷与低温的热力学基础 • Chapter 2: Refrigerants 制冷工质 • Chapter 3: Vapor refrigeration cycles 蒸汽制冷循环
with work down to the surroundings（例：布雷
顿循环、布雷顿制冷机）
• Differential isentropic expansion effect (微分等
熵效应):
⎛ ∂T ⎞ T ⎛ ∂v ⎞ as = ⎜ ⎟ = ⎜ ⎜ ∂p ⎟ c ∂T ⎟ ⎠p ⎝ ⎠s p ⎝
10
HW-1
Due Wednesday 3/2 in class
A piston-cylinder device initially contains 0.15-kg steam at 3.5 MPa, superheated by 5℃. Now the steam loses heat to the surroundings and the piston moves down, hitting a set of stops at which point the cylinder contains saturated liquid water. The cooling continues until the cylinder contains water at 200℃. Determine (a) the final pressure and the quality, (b) the boundary work, (c) the amount of the heat transfer when the piston first hits the stops, (d) and the total heat transfer.
17
§1.1 Phase Transformation Refrigeration
18
§1.1 Phase Transformation Refrigeration
•p-h diagram （压焓图）
• Isobar (等压线） • Isenthalpic (等焓线） • Isentropic (等熵线） • Isochore (等容线) • Critical point (临界点）
式中，m为多变指数 (polytropic index)
23
§1.2 Refrigeration of gas adiabatic expansion
•Adiabatic gas discharge process (绝热放气过程)
（例：Simon expansion) 对容器内的气体运用热力学第一定律
13
§1.1 Phase Transformation Refrigeration
• Liquid evaporation
r = h"− h' = T ( s"− s' )
r: Latent heat(潜热) h: Enthalpy (焓) s: Entropy(熵)
The higher the boiling point the smaller the LH • R717-NH3；R744-CO2；R22-CHF2Cl (二氟一氯甲烷)
8
Applications of R&C Tech.
9
Refrigerants（制冷剂/工质）
• Halocarbon compounds (卤化碳制冷剂：甲、 乙、丙烷的衍生物) • Hydrocarbons (碳氢化合物:甲、乙、丙烷等) • Inorganic compounds (无机化合物：水、氨、 CO2等) • Mixed refrigerant (混合制冷剂) • Cryogenic working fluids (低温工质：CH4, air, fluorin (氟), argon, nitrogen, neon (氖)等)
• Thaw(融化) & sublimation(升华) of solid substances
表1-1冰的升华压力和对应的升华温度
温度／℃ 升华压力／kPa 0 0.61 -25 63×10-3 -50 3.87×10-3 -75 0.116×10-3
16
§1.1 Phase Transformation Refrigeration
14
§1.1 Phase Transformation Refrigeration
• Throttling evaporation（闪发、节流气化） • Refrigeration effect （制冷量、制冷效应）
q0 = r (1 − χ )
χ — quality
15
§1.1 Phase Transformation Refrigeration
⎛ ∂T ⎞ ah = ⎜ ⎟ ⎜ ∂p ⎟ ⎠h ⎝
25
§1.2 Refrigeration of gas adiabatic expansion
•Throttling expansion process (节流膨胀过程)
• 实际气体节流膨胀时的微分节流效应 (Joule-Thomson effect)
11
HW-2
Due Wednesday 3/16 in class
Textbook p46: Exercises 1-1, 1-2, 1-4 ~ 1-24
12
Chapter 1. Thermodynamic Foundations of R&C
• For a refrigeration cycle
22
§1.2 Refrigeration of gas adiabatic expansion
在实际膨胀过程中，由于过程的不可逆，理想 气体的积分等熵效应由下式确定
m −1 ⎤ ⎡ m ⎢1 − ⎛ p2 ⎞ ⎥ ⎜ ⎟ ΔT = T1 − T2 = T1 ⎢ ⎜ p1 ⎟ ⎥ ⎢ ⎝ ⎠ ⎥ ⎦ ⎣
Question Answering
• Email your questions to: liwang@me.ustb.edu.cn with your name, class and phone number • I’ll answer you by email or by phone
P.S. Register classes’ email boxes
•Throttling expansion process (节流膨胀过程)
• “节流过程是一降温而不制冷的过程”。节流时有摩擦损失， 是一个不可逆过程，其结果将导致熵的增加。 • 理想气体的内能和焓仅是温度的函数。理想气体节流时
，，
Δu = 0
Δh = 0
ΔT = 0
• 实 际 气 体 节 流 膨 胀 时 的 微 分 节 流 效 应 (Joule-Thomson effect)
7
Applications of R&C Tech.
• Air conditioning (building, domestic, vehicles & industries) • Environment simulation • Food refrigeration, freeze & delivery • Medical and biological applications • Nature gas, hydrogen … liquefaction • Aviation & Spaceflight • ……
R ⎛ ∂v ⎞ ⎜ ⎟ = ⎝ ∂T ⎠ p p
as ,id
κ −1 T = κ p
•Integral isentropic expansion effect(积分等熵效应):
ΔT = ∫ as dp
p1
21
p2
§1.2 Refrigeration of gas adiabatic expansion
•Integral isentropic effect(积分等熵效应):
ΔT = ∫ as dp
p1 p2
for an ideal gas
⎡ Δ T = T1 − T 2 = T1 ⎢1 − ⎢ ⎢ ⎣ ⎛ P2 ⎞ ⎜ ⎜ P ⎟ ⎟ ⎝ 1 ⎠
κ −1 κ
κ −1 κ
⎤ ⎥ ⎥ ⎥ ⎦
T2 ⎛ p2 ⎞ =⎜ ⎟ T1 ⎜ p1 ⎟ ⎝ ⎠
Qo + W = Qh
பைடு நூலகம்
Q0: Heat absorbed from low temp. reservoir W: Work from outside Qh: Heat released (rejected) to high temp. reservoir The equation obeys the 1st and the 2nd laws of thermodynamics simultaneously
Principles of Refrigeration & Cryogenics
制冷与低温原理
王 立 Phone：62334425 Email：Liwang@me.ustb.edu.cn
1
Text and Reference Books
Text book
• 陈光明,陈国邦，制冷与低温技术原理（第二版）， 机械工业出版社，北京，2004
6
Exordium（绪论） • Refrigeration & cryogenic technology The tech. to get temperature artificially below the temperature of circumstances and to keep it. • Temperature range of refrigeration >120k/-153℃ • Temperature range of cryogenics <120k/-153℃
19
§1.2 Refrigeration of gas adiabatic expansion
• Isentropic (等熵) expansion = reversible adiabatic expansion 可逆绝热膨胀 • Gas expansion through an expander(膨胀机)
hdm = dU
式中，U为容器内气体总内能。
dU = d (mu ) = mdu + udm
经推导变换
T2 ⎛ p2 ⎞ =⎜ ⎟ T1 ⎜ p1 ⎟ ⎝ ⎠
κ −1 κ
结果与有外功输出的可逆绝热(等熵)膨胀过程相同。
24
§1.2 Refrigeration of gas adiabatic expansion
Reference books
• 吴业正，制冷与低温技术原理，高等教育出版社， 北京，2004 • 吴业正，制冷原理与设备，西安交通大学出版社， 西安，1987 • Thomas M. Flynn, Cryogenic engineering (Second edition), Marcel Dekker, Inc. , New York, NY, 2005
5
Content
• Chapter 4: Gas refrigeration & liquefaction (液化) cycles 气体制冷与液化循环 • Chapter 5: Principles air/gas separation 气体分离原理 • Chapter 6: Entropy & exergy analysis 熵与“火用”分析
20
§1.2 Refrigeration of gas adiabatic expansion
•Differential isentropic expansion effect:
⎛ ∂T ⎞ T ⎛ ∂v ⎞ as = ⎜ ⎜ ∂p ⎟ = c ⎜ ∂T ⎟ ⎟ ⎠p ⎝ ⎠s p ⎝
for an ideal gas
3
Homework - 0
• Read the textbook, before/after the classes, word by word carefully and thoughtfully.
4
Content
• Exordium（绪论） • Chapter 1: Thermodynamic foundations of refrigeration(制冷) & cryogenics(低温) 制冷与低温的热力学基础 • Chapter 2: Refrigerants 制冷工质 • Chapter 3: Vapor refrigeration cycles 蒸汽制冷循环
with work down to the surroundings（例：布雷
顿循环、布雷顿制冷机）
• Differential isentropic expansion effect (微分等
熵效应):
⎛ ∂T ⎞ T ⎛ ∂v ⎞ as = ⎜ ⎟ = ⎜ ⎜ ∂p ⎟ c ∂T ⎟ ⎠p ⎝ ⎠s p ⎝
10
HW-1
Due Wednesday 3/2 in class
A piston-cylinder device initially contains 0.15-kg steam at 3.5 MPa, superheated by 5℃. Now the steam loses heat to the surroundings and the piston moves down, hitting a set of stops at which point the cylinder contains saturated liquid water. The cooling continues until the cylinder contains water at 200℃. Determine (a) the final pressure and the quality, (b) the boundary work, (c) the amount of the heat transfer when the piston first hits the stops, (d) and the total heat transfer.
17
§1.1 Phase Transformation Refrigeration
18
§1.1 Phase Transformation Refrigeration
•p-h diagram （压焓图）
• Isobar (等压线） • Isenthalpic (等焓线） • Isentropic (等熵线） • Isochore (等容线) • Critical point (临界点）
式中，m为多变指数 (polytropic index)
23
§1.2 Refrigeration of gas adiabatic expansion
•Adiabatic gas discharge process (绝热放气过程)
（例：Simon expansion) 对容器内的气体运用热力学第一定律
13
§1.1 Phase Transformation Refrigeration
• Liquid evaporation
r = h"− h' = T ( s"− s' )
r: Latent heat(潜热) h: Enthalpy (焓) s: Entropy(熵)
The higher the boiling point the smaller the LH • R717-NH3；R744-CO2；R22-CHF2Cl (二氟一氯甲烷)
8
Applications of R&C Tech.
9
Refrigerants（制冷剂/工质）
• Halocarbon compounds (卤化碳制冷剂：甲、 乙、丙烷的衍生物) • Hydrocarbons (碳氢化合物:甲、乙、丙烷等) • Inorganic compounds (无机化合物：水、氨、 CO2等) • Mixed refrigerant (混合制冷剂) • Cryogenic working fluids (低温工质：CH4, air, fluorin (氟), argon, nitrogen, neon (氖)等)
• Thaw(融化) & sublimation(升华) of solid substances
表1-1冰的升华压力和对应的升华温度
温度／℃ 升华压力／kPa 0 0.61 -25 63×10-3 -50 3.87×10-3 -75 0.116×10-3
16
§1.1 Phase Transformation Refrigeration
14
§1.1 Phase Transformation Refrigeration
• Throttling evaporation（闪发、节流气化） • Refrigeration effect （制冷量、制冷效应）
q0 = r (1 − χ )
χ — quality
15
§1.1 Phase Transformation Refrigeration
⎛ ∂T ⎞ ah = ⎜ ⎟ ⎜ ∂p ⎟ ⎠h ⎝
25
§1.2 Refrigeration of gas adiabatic expansion
•Throttling expansion process (节流膨胀过程)
• 实际气体节流膨胀时的微分节流效应 (Joule-Thomson effect)
11
HW-2
Due Wednesday 3/16 in class
Textbook p46: Exercises 1-1, 1-2, 1-4 ~ 1-24
12
Chapter 1. Thermodynamic Foundations of R&C
• For a refrigeration cycle
22
§1.2 Refrigeration of gas adiabatic expansion
在实际膨胀过程中，由于过程的不可逆，理想 气体的积分等熵效应由下式确定
m −1 ⎤ ⎡ m ⎢1 − ⎛ p2 ⎞ ⎥ ⎜ ⎟ ΔT = T1 − T2 = T1 ⎢ ⎜ p1 ⎟ ⎥ ⎢ ⎝ ⎠ ⎥ ⎦ ⎣