化工热力学(第三版)答案陈钟秀
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2-1.使用下述方法计算1kmol甲烷贮存在体积为0.1246m3、温度为50℃的容器中产生的压力:(1)理想气体方程;(2)R-K方程;(3)普遍化关系式。
解:甲烷的摩尔体积V=0.1246 m3/1kmol=124.6 cm3/mol
查附录二得甲烷的临界参数:Tc=190.6K Pc=4.600MPa Vc=99 cm3/mol ω=0.008
(1) 理想气体方程
P=RT/V=8.314×323.15/124.6×10-6=21.56MPa
(2) R-K方程
22.522.560.5268.314190.60.427480.427483.2224.610ccRTaPamKmolP
53168.314190.60.086640.086642.985104.610ccRTbmmolP
∴0.5RTaPVbTVVb
50.5558.314323.153.22212.462.98510323.1512.461012.462.98510
=19.04MPa
(3) 普遍化关系式
323.15190.61.695rcTTT 124.6991.259rcVVV<2
∴利用普压法计算,01ZZZ
∵ crZRTPPPV
∴ crPVZPRT
654.61012.46100.21338.314323.15crrrPVZPPPRT
迭代:令Z0=1→Pr0=4.687 又Tr=1.695,查附录三得:Z0=0.8938 Z1=0.4623
01ZZZ=0.8938+0.008×0.4623=0.8975
此时,P=PcPr=4.6×4.687=21.56MPa
同理,取Z1=0.8975 依上述过程计算,直至计算出的相邻的两个Z值相差很小,迭代结束,得Z和P的值。
∴ P=19.22MPa
2-2.分别使用理想气体方程和Pitzer普遍化关系式计算510K、2.5MPa正丁烷的摩尔体积。已知实验值为1480.7cm3/mol。
解:查附录二得正丁烷的临界参数:Tc=425.2K Pc=3.800MPa Vc=99 cm3/mol ω=0.193 (1)理想气体方程
V=RT/P=8.314×510/2.5×106=1.696×10-3m3/mol
误差:1.6961.4807100%14.54%1.4807
(2)Pitzer普遍化关系式
对比参数:510425.21.199rcTTT 2.53.80.6579rcPPP—普维法
∴ 01.61.60.4220.4220.0830.0830.23261.199rBT
14.24.20.1720.1720.1390.1390.058741.199rBT
01ccBPBBRT=-0.2326+0.193×0.05874=-0.2213
11crcrBPBPPZRTRTT=1-0.2213×0.6579/1.199=0.8786
∴ PV=ZRT→V= ZRT/P=0.8786×8.314×510/2.5×106=1.49×10-3 m3/mol
误差:1.491.4807100%0.63%1.4807
2-3.生产半水煤气时,煤气发生炉在吹风阶段的某种情况下,76%(摩尔分数)的碳生成二氧化碳,其余的生成一氧化碳。试计算:(1)含碳量为81.38%的100kg的焦炭能生成1.1013MPa、303K的吹风气若干立方米?(2)所得吹风气的组成和各气体分压。
解:查附录二得混合气中各组分的临界参数:
一氧化碳(1):Tc=132.9K Pc=3.496MPa Vc=93.1 cm3/mol ω=0.049 Zc=0.295
二氧化碳(2):Tc=304.2K Pc=7.376MPa Vc=94.0 cm3/mol ω=0.225 Zc=0.274
又y1=0.24,y2=0.76
∴(1)由Kay规则计算得:
0.24132.90.76304.2263.1cmiciiTyTK
0.243.4960.767.3766.445cmiciiPyPMPa
303263.11.15rmcmTTT 0.1011.4450.0157rmcmPPP—普维法
利用真实气体混合物的第二维里系数法进行计算
011.61.610.4220.4220.0830.0830.02989303132.9rBT
114.24.210.1720.1720.1390.1390.1336303132.9rBT 016111111618.314132.90.029890.0490.13367.378103.49610ccRTBBBP
021.61.620.4220.4220.0830.0830.3417303304.2rBT
124.24.220.1720.1720.1390.1390.03588303304.2rBT
016222222628.314304.20.34170.2250.03588119.93107.37610ccRTBBBP
又0.50.5132.9304.2201.068cijcicjTTTK
331313131331293.194.093.55/22cccijVVVcmmol
120.2950.2740.284522cccijZZZ
120.2950.2250.13722cij
6/0.28458.314201.068/93.55105.0838cijcijcijcijPZRTVMPa
∴ 303201.0681.507rijcijTTT 0.10135.08380.0199rijcijPPP
0121.61.6120.4220.4220.0830.0830.1361.507rBT
1124.24.2120.1720.1720.1390.1390.10831.507rBT
∴01612121212126128.314201.0680.1360.1370.108339.84105.083810ccRTBBBP
2211112122222mByByyByB
26626630.247.3781020.240.7639.84100.76119.931084.2710/cmmol∴1mmBPPVZRTRT→V=0.02486m3/mol
∴V总=n V=100×103×81.38%/12×0.02486=168.58m3
(2) 1110.2950.240.10130.0250.2845cmZPyPMPaZ 2220.2740.760.10130.0740.2845cmZPyPMPaZ
2-4.将压力为2.03MPa、温度为477K条件下的2.83m3NH3压缩到0.142 m3,若压缩后温度448.6K,则其压力为若干?分别用下述方法计算:(1)Vander Waals方程;(2)Redlich-Kwang方程;(3)Peng-Robinson方程;(4)普遍化关系式。
解:查附录二得NH3的临界参数:Tc=405.6K Pc=11.28MPa Vc=72.5 cm3/mol ω=0.250
(1) 求取气体的摩尔体积
对于状态Ⅰ:P=2.03 MPa、T=447K、V=2.83 m3
477405.61.176rcTTT 2.0311.280.18rcPPP—普维法
∴01.61.60.4220.4220.0830.0830.24261.176rBT
14.24.20.1720.1720.1390.1390.051941.176rBT
010.24260.250.051940.2296ccBPBBRT
11crcrBPPVBPPZRTRTRTT→V=1.885×10-3m3/mol
∴n=2.83m3/1.885×10-3m3/mol=1501mol
对于状态Ⅱ:摩尔体积V=0.142 m3/1501mol=9.458×10-5m3/mol T=448.6K
(2) Vander Waals方程
222262627278.314405.60.4253646411.2810ccRTaPammolP
53168.314405.63.737108811.2810ccRTbmmolP
22558.314448.60.425317.659.4583.737103.73710RTaPMPaVbV
(3) Redlich-Kwang方程
22.522.560.5268.314405.60.427480.427488.67911.2810ccRTaPamKmolP
53168.314405.60.086640.086642.591011.2810ccRTbmmolP
0.550.5558.314448.68.67918.349.4582.5910448.69.458109.4582.5910RTaPMPaVbTVVb (4) Peng-Robinson方程
∵448.6405.61.106rcTTT
∴220.37461.542260.269920.37461.542260.250.269920.250.7433k
220.50.51110.743311.1060.9247rTkT
22226268.314405.60.457240.457240.92470.426211.2810cccRTaTaTTPammolP
53168.314405.60.077800.077802.3261011.2810ccRTbmmolP
∴aTRTPVbVVbbVb
510108.314448.60.42629.4582.326109.4589.4582.326102.3269.4582.32610 19.00MPa
(5) 普遍化关系式
∵ 559.458107.25101.305rcVVV<2 适用普压法,迭代进行计算,方法同1-1(3)