第三章 蒸气制冷循环 1 (3.1.1)_浙江大学制冷与低温研究所

1. An isentropic compression 2. No temperature diffidence 3. Add a recuperative process 4. No pressure loss
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3.1.1 Ideal cycles using pure refrigerants 一、纯工质理论循环 3.1.1.4 Recuperative cycles （四）回热循环
Assumptions
1. An isentropic compression 2. No temperature diffidence 3. Saturated liquid and vapor 4. No pressure loss
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3.1.1 Systems using pure refrigerants 一、纯工质理论循环 3.1.1.1 Saturated cycles （一）饱和循环
第一节 单级蒸气压缩制冷循环 一、纯工质理论循环 二、纯工质实际循环 三、混合工质循环 四、循环特性分析
3.1 One-stage vapor compression systems 3.1.1 Ideal cycles using pure refrigerants
3.1.1.1 Saturated cycles 3.1.1.2 Subcooled cycles 3.1.1.3 Superheated cycles 3.1.1.4 Recuperative cycles
3.1 One-stage vapor compression systems 第一节 单级蒸气压缩制冷循环 3.1.1 Systems using pure refrigerants 一、纯工质理论循环
Overheated corner
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3.1.1 Systems using pure refrigerants 一、纯工质理论循环 3.1.1.1 Saturated cycles （一）饱和循环
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η0’‘’ η0’’’＝ε0’’‘ /εc ~ η0 ？ R600a、R134a
Harmful： 3 q v’’’ q v’’‘＝q0’’‘ ’/v1’ ~ qv ？ R22、R717
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3.1.1 Ideal cycles using pure refrigerants 一、纯工质理论循环 3.1.1.5 Summary （五）小结
cycles
Gas refrigeration
cycles
Vapor compression
cycles
Vapor absorption
cycles
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3 Vapor refrigeration cycles
第三章 蒸汽制冷循环
Refrigeration cycles
( Component )
Index R134a R22
R717
Influence
1
q0
128.5 147.0 1043.1 Gains
2
w0
42.6
46.59 319.9 Energy cost
3
ε0
3.016 3.155 3.261
ε0＝q0/w0
4
qv
872.9 1595.9 1673.9 Material cost
5
qk
Energy balances
Δh = q + w
Parts Features Relations
Compressor
q＝0 w0＝h2-h1
Condenser
w＝0 qk＝h2-h4
Expansion
q＝0,w＝0 h4＝h5
Evaporator
w＝0 q0＝h1-h5
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3.1.1 Systems using pure refrigerants 一、纯工质理论循环 3.1.1.1 Saturated cycles （一）饱和循环
5 q’v q’v＝q’0 /v1’> qv ↑
Beneficial
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3.1.1 Ideal cycles using pure refrigerants 一、纯工质理论循环 3.1.1.3 Superheated cycles （三）过热循环
Assumptions
1. An isentropic compression 2. No temperature diffidence 3. Superheated vapor 4. No pressure loss
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3.1.1 Ideal cycles using pure refrigerants 一、纯工质理论循环 3.1.1.3 Superheated cycles （三）过热循环
Index
Expressions
1 q0’’ q0’’＝q0 2 w0’’ w0’’＞ w 0 3 ε0’’ ε0’’＝q0’’ /w0’’＜ε0 ↓ 4 η0’’ η0’’＝ε0’’ /εc＜η0 ↓ 5 q v’’ q v’’＝q0’’ /v1’＜qv ↓
11
t2
48.4
67.6
135.2
Material cost
12
PR 7.66
13
k
1.1
6.26 1.2
8.18 1.3
t2＝t1(PR)(k-1)/k
14 Mol 102.03 86.48 17.03
k
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3.1.1 Ideal cycles using pure refrigerants 一、纯工质理论循环 3.1.1.2 Subcooled cycles （二）过冷循环
3 Vapor refrigeration cycles
3.1 One-stage vapor compression systems 3.2 Two-stage vapor compression systems 3.3 Cascade vapor compression systems 3.4 Vapor absorption systems
Influence to cycle ∆q 0=0 ∆w 0 > 0
Harmful
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3.1.1 Ideal cycles using pure refrigerants 一、纯工质理论循环 3.1.1.4 Recuperative cycles （四）回热循环
Assumptions
Index
Expressions
Influence to cycle
1 q 0’’’ q0’’’ = h1 – h4’ = q0’ ∆q0 > 0
2 w0’’ w0’’’’＞ w 0
∆w 0 > 0
4
ε0’’’
ε0’’’＝q0’’’ /w0’’’ ~ ε0
？ Beneficial： R502、R290、
Inde
Expression
x
Influence to cycle
1 q0’ q0 ’ = h1 – h4’ = h1’ – h4 ↑ ∆q0 > 0
2 w0’ w0’ ＝ w 0
∆w0 = 0
3 ε0’ ε0’＝q0 ’ /w0’ > ε0 ↑ 4 η0’ η0’＝ε0’ /εc > η0 ↑
Beneficial
qv＝q0/v1
Material cost
7 pk
pk＝ps(Tk)
Material cost
8 p0
p0＝ps(T0)
Material cost
9
t2
t2＝f(PR,k)
Material cost
10 PR
PR＝pk/p0
Material cost
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3.1.1 Systems using pure refrigerants 一、纯工质理论循环 3.1.1.1 Saturated cycles （一）饱和循环
第一节 单级蒸气压缩制冷循环 一、纯工质理论循环
（一）饱和循环 （二）过冷循环 （三）过热循环 （四）回热循环
Compresso r
Joule-Thomson effect and J. Perkins ( 1844, American )
Condenser
Ether
Evaporator
Expansion valves
第三章 蒸汽制冷循环
第一节 单级蒸气压缩制冷循环 第二节 两级蒸气压缩制冷循环 第三节 复叠式制冷循环 第四节 蒸气吸收制冷循环
Refrigeration cycles
( Phase change )
3 Vapor refrigeration cycles
第三章 蒸汽制冷循环
பைடு நூலகம்
Vapor refrigeration
Assumptions
1. An isentropic compression 2. No temperature diffidence 3. Subcooled liquid 4. No pressure loss
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3.1.1 Ideal cycles using pure refrigerants 一、纯工质理论循环 3.1.1.2 Subcooled cycles （二）过冷循环
过
饱
热
和
循
循
环
环
过
回
冷
热
循
循
环
环
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Homework_10
10.目前R22 、R134a和R717分别主要 用在什么制冷装置中？为什么不同的
制冷装置要采用不同的制冷剂？
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Refrigeration cycles using pure refrigerant
Refrigeration cycles using mixed refrigerant
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3.1 One-stage vapor compression systems 3.1.1 Ideal cycles using pure refrigerants 3.1.2 Practical cycles using pure refrigerants 3.1.3 Practical cycles using mixed refrigerants 3.1.4 Analysis of cycles
r0
213
219.5 1329
qv＝q0/v1
qk
6
pk
1016.4 1533.6 1555.5 Material cost
7
p0
132.7 244.9 190.1
8
tc
101.1℃ 96℃
133℃
9
tf
-96.6℃ -160℃ -77.9℃
p0、pk
10
tb
-26.1℃ -40.76℃ -33.3℃
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3.1 One-stage vapor compression systems 第一节 单级蒸气压缩制冷循环 3.1.1 Systems using pure refrigerants 一、纯工质理论循环
T
TH
3
2
TL
4
1
s
Overheated corner
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Inde x
Expression
Influence to cycle
1 q0
q0＝h1-h5
Gains
2 w0
w0＝h2-h1
Energy cost
3 ε0
ε0＝q0/w0
Energy cost
4 η0
η0＝ε0/εc
Energy cost
qk
5 qk
qk＝h2-h4
Material cost
6 qv