化工热力学第三版答案
《化工热力学》(第三版)习题参考答案
58页第2章
2-1 求温度673.15K、压力4.053MPa的甲烷气体摩尔体积。 解:(a)理想气体方程
pVRTV
(b)用R-K方程
RT8.314673.15331
1.38110mmol6
p4.05310
① 查表求Tc、pc;② 计算a、b;③ 利用迭代法计算V。
RTa
VbVVbaVibRT
Vi1b
pViVibp
V01.381103m3mol1
Vi11.3896103m3mol1
(c)用PR方程
步骤同(b),计算结果:Vi11.3893103m3mol1。 (d)利用维里截断式
Z
BpppppVBp
11cr1B0rB1rRTRTRTcTrTrTr
0.172
B10.1394.2
Tr
1
0.422
B00.0831.6
Tr
查表可计算pr、Tr、B、B和Z 由Z
pVZRT
V1.391103m3mol1 RTp
2-4 V=1.213 m3,乙醇45.40 kg,T=500.15K,求压力。 解:(a)理想气体状态方程
p
nRTmRT45.408.314500.15
3.383MPa VMV461.213
(b)用R-K方程
a
0.42748RTC
PC0.08664RTC
PC
22.5
28.039
b0.058
p
RTaVmbVmVmbVm
V1.213
1.229m3kmol1 n45.40/46p2.759MPa
(c)用SRK
方程计算
(d)用PR
方程计算
(e)用三参数普遍化关联
m45.40.987kmolM46V1.213Vm1.229m3kmol1
n0.987pVmBpRTZ1p
RTRTVmBn
Bpc1B0B1BB0B1RTcpc RTc
B00.361,B10.057,0.635B0.267p
RT
2.779MPa
VmB
2-7 计算T=523.15K,p=2 MPa 的水蒸气的Z和V 解:(a)用维里截断式
Z
pVBCRTBRTCRT
12V采用迭代法计算V=2.006 2RTVVppVpV
之后求得Z=0.923
(d)利用维里截断式
Z
BpppppVBp
11cr1B0rB1rRTRTRTcTrTrTr
0.172
B10.1394.2
Tr
1
0.422
B00.0831.6
Tr
查表可计算pr、Tr、B、B可得到Z=0.932;
由Z
pVZRT
V2.025103m3mol1 RTp
(c)水蒸气表
V0.11144m3kg10.11144182.00592m3kmol1pV20002.00592Z0.9223
RT8.314523.15
92页第三章 3-4
丁二烯13
R8.314
T1127273.15P12.5310PaTc4250.181
6
T2227273.15P212.6710Pc4.32610
Cp(T)22.738222.79610
6
PaPa
62
6
3
T73.87910T
利用三参数压缩因子计算方法,查图表,得到压缩因子:
Tr1
Tc
T1
Tr2
Tc
T2
Tr10.942
Tr21.177
Pr1
P1Pc
Pr2
P2Pc
Pr10.585Pr22.929
Z10.677
Z2RT2Z1RT1V
P2P1
Z20.535
4
3
1
V7.14610mmol
1.64.2
RTcP2T2T2H2R0.0830.1391.0970.894PcTcTc
H2R8.47510
3
1.64.2
RTcP1TT11H1R0.0830.1391.0970.894Pc
TcTc
T
H1R2.70410
3
2
HCp(T)dTH2RH1R
T
1
H5.02810
3
Jmol
1
S2R12.128
2.65.2
RP2T2T2S2R0.6750.722PcTcTc
2.65.2
RP1T1T1S1R0.6750.722PcTcTc
S1R4.708
S
T
T2
Cp(T)T
1
P2
dTRlnS2RS1R
P1
S3.212JmolK
11
3-7: 解:
1VSV
,, VTppTpT
p2S33
pVSp1Vdp2.095101.551102000381 T
m3kPa
5.261105.261Jkg1K1
kgK
3
注意:mkPa10J
33
1.5511031.6191061.091kJkg1 HTSVp2705.261
或者
H
p2
12.0951032701.55110321063.81105
1090.6Jkg1
p1
1TVLdp
3-9
解:乙腈的Antonie方程为
lnps14.7258
3271.24t/c241.85
kPa
(1)60℃时,乙腈的蒸气压
3271.24
3.888
60241.85
ps48.813kPalnps14.7258
(2)乙腈的标准沸点
ln10014.7258t81.375c
3271.24
4.605
t/c241.85
(3)20℃、40℃和标准沸点时的汽化焓
dlnpsH3271.24H
dTRT2t241.852RT23271.248.314T2H
t241.852
H20c34.09kJ/mol;H40c33.57kJ/mol;H81.375c32.72kJ/mol
117页第四章 4-1
31
h
12
ugz
42
qwz3mh(23003230)10
4
3J10kg
kg3600s
q0
kg
msh2.58310
10kg
kg
3600ss
6J
u12050
kg
22
109
kg
u109
s
4J
12
mu1.6510
2
s
J
gzms
6J
h
12
mugzm2.56710
2
s
w
6J62.567102.56710Ws
wc
2.5832.567
100%
2.567
wc0.623%
4-2
方法一:
h
1212
ugz
22
qw
u130.0750.25
22
R8.314
huw
u2u1u20.27
T2353.15H
T1593.15
CpmhT2T1HR2HR1
Pr0B0B100HRTrdB00.344dB1dPr1R647.30T0T0rr000
HR1576.771
Pr1B0B1dB010.344dB11dPHRR647.3T2r1r
1Tr1Tr110
HR256.91
经计算得
Cpmh35.03Jmol1K1
0.07531
体积流速为:Vu1d/23.1430.0132ms
2
2
2
摩尔流速为:n
VV0.01324.015mols1 VmRT/p8.314593.15/1500000
根据热力学第一定律,绝热时Ws = -△H,所以
方法二:
根据过热蒸汽表,内插法应用可查得
35kPa、80℃的乏汽处在过热蒸汽区,其焓值h2=2645.6 kJ·kg-1; 1500 kPa、320℃的水蒸汽在过热蒸汽区,其焓值h1=3081.5 kJ·kg-1;
w
h
122u2u12
2645.63081.54.46410
3
435.904kJkg
1
按理想气体体积计算的体积V
RTP
8.314593.153
3.28810
1500000
0.0132ms
31
mmol
31
mol
Ns
mol
331s
3.28810mmol
w435.90418N3.1510W
4
4-6 解:
二氧化碳T1303.15P11.510Tc304.20.225
6
R8.314
Pa
P20.1013310Pc7.35710
Cp(T)45.3698.68810
3
66
PaPa
52
T9.61910T
RTcP1TT11
H1R0.0830.1391.0970.894P
TTRTcP2T2T2
H2RT20.0830.1391.0970.894PcTcTc
T2
Cp(T)
H1RdT通过T2T1迭代计算温度,T2=287.75 K
TCpmhT
1
T2ln
T1
RP1TT
11
S1R0.6750.722PTTRP2T2T2
S2R0.6750.722PTT4-7
解:
T1473.15P12.510Tc305.40.098
6
R8.314
Pa
P20.2010Pc4.8810
Cp(T)9.403159.83710
6
PaPa
62
6
3
T46.23410T
RP1TT11
S1R0.6750.722PTTRP2T2T2
S2RT20.6750.722PcTcTc
经迭代计算(参考101页例题4-3)得到T=340.71K。
RTcP1TT11
H1R0.0830.1391.0970.894PcTcTc
RTcP2TT22
H2RT20.0830.1391.0970.894PcTcTc
H
2Cp(T)dTH2RT2H1R
8.3272510Jmol
31
T1
。
146页第五章
5-1:b 5-2: c 5-4: a 5-5: a
5-1:
解:可逆过程熵产为零,即SgSsysSfSsys5-2:
解:不可逆过程熵产大于零,即SgSsysSfSsys系统熵变可小于零也可大于零。
5-4:
解:不可逆绝热过程熵产大于零,即SgSsysSfSsys0。所以流体熵变大于零。 5-5:
解:不可逆过程熵产大于零,即SgSsysSfSsys
5
0Ssys0。 T0
55
。即0Ssys
T0T0
10100Ssys。 T0T0
5-3:
解:电阻器作为系统,温度维持100℃,即373.15K,属于放热;环境温度298.15K,属于吸热,根据孤立体系的熵变为系统熵变加环境熵变,可计算如下:
50(20A)23600s1.4410J1.4410J1.4410J41
9.70710J
373.15K298.15KK
8
8
2
8
5-6: 解:理想气体节流过程即是等焓变化,温度不变,而且过程绝热,所以系统的熵变等于熵产,计算如下:
所以过程不可逆。
5-7: 解: 页4-7
绝热稳流过程所以
MMh320kgs
1
m1m2Hm1h1m2h2
T3
(90273.15)K30kgs
50kgs
1
1
(50273.15)K
T3339.15KSg339.15273.1566
j
mjSj
i
miSi
T3T3
m1Cpmslnm2Cpmsln
T1T2
12
4.19kJkg
CpmsCpmh
9050
K
不同温度的S值也可以直接用饱和水表查得。计算结果是0.336。 5-12
解:(1)循环的热效率
WNWS,TurW41
T
QHH2H1
(2) 水泵功与透平功之比
H2=3562.38 kJ·kg-1,H3=2409.3 kJ·kg-1,H4=162.60 kJ·kg-1,H5=2572.14 kJ·kg-1,
H4VpH1162.60140.0071030.001176.6
kJkg1
41S,Tur
Vp0.001(140.007)1030.012 H2H33562.382409.3
T
H2H3H1H4
0.345
H2H1
(3) 提供1 kw电功的蒸气循环量
m
10001000
0.857gs1 WN1167.08
5-15题:
415
T0TH
WQH
QLW
TLT0TL
C
1
TQLQH
C60%T
20%
1TL
TT0.60.20.555TH
0L
T0
T0QL
irirc60%20%1QHTHTL
TT0.60.20L
21273.156273.1510.120.555118273.15216
194页第六章
WidH(374.114)T0S(374.1140.1049)3.60710Js
(b)
292.98376.92
83.94
6-3
HSsurSg
h2h1H
T0
SsysSsur
0.95491.192583.94
298
热损失为
1
0.044kJkg
1
K
1
根据热力学第一定律
Q功损失为WL
T0SgH
83.94kJkg或Q1.51110Jmol
31
13.1kJkg
1
或
WL
235.8Jmol
1
6-6:
解:理想气体经一锐孔降压过程为节流过程,H0,且Q0,故WS0,过程恒温。
WL
Wid
T0Sg
2988.314ln7.4210Jmol1.96
6-12: 解:
查表得HfS
H20
H2O285.84
NH346.19
O20
CH3OH238.64
CO2393.51
N20
130.5969.94192.51205.03126.8213.64
191.49
H2
1
H2O2H2O(l)
2H
285.84kJmol
1
S
69.94130.590.5205.038.314ln
0.0206105
0.10133
169.785JmolK
11
12
NH3N2
32
H2NH3
3117.6110.335116.63
336.535kJmol
1
EXC(NH3)
CH3OH
EXC(CH3OH)
4117.6111.966410.54166.31716.636kJmol
1
6-13 解:
H
Q1Q2
Q1
m1h3h1
Q2m2h3h2
720001
m1kgs
3600h1376.92kJkg
1080001m2kgs
3600
1
1
1
S11.1925kJkg
K
1
h2209.3k3Jkg
1
S20.7038kJkg
K
1
使用内插法可求得66.03℃时的熵值,
S30.893566.0365
0.95490.8935
7065
S3
0.906
kJkg
1
K
1
(1)利用熵分析法计算损耗功,
(2)利用火用分析法:
h0104.89
S00.3674
Mm1m2
EX1m1h0h1m1T0S0S1EX3Mh0h3MT0S0S3WL
100.178kJs
1
EX2m2h0h2m2T0S0S2WLEX1EX2EX3
或者