?s?cpln ?T2pp?RT2?Rln2?ln?Rln2T1p1??1T1p11.4?0.2968611.80.2ln?0.2968ln?0.20 kJ/kg?K1.4?18000.1
exu1?exu2?u1?u2?p0?v2?v1??T0?s2?s1?R?T?T??p0?v2?v1??T0?s??1120.2968 ???800?611.8??100??0.908?0.237??300?0.21.4?1 ?132.5 kJ/kg ?5-22
m?pV200?1011??13.94 kgRT10.287?500
Q?mcp?T2?T1??13.94?1.005??600?500??1400.7 kJ?s?cplnT2600?1.005?ln?0.1832 kJ/kg?KT1500
Exq?Q?T0m??s?1400.7?300?13.94?0.1832?634.6 kJAnq?T0m??s?300?13.94?0.1832?766.1 kJ
5-23
ws??R?T1?T2?1.4?0.287??500?320???180.74 kJ/kg??11.4?1
?s?cplnT2p3200.1?Rln2?1.005?ln?0.287?lnT1p15000.5 ?0.0134 kJ/kg?Kexh1?exh2?h1?h2?T0?s2?s1??cp?T1?T2??T0?s ?1.005??500?320??300?0.0134?184.92 kJ/kg
?ex?ws180.74??97.7%exh1?exh2184.92
5-24 ⑴⑵
??1?T2?300?20?1??67.3%T1?1000?20
?t?1?T0300?1??70%T11000
L?Q1??t????1000??0.7?0.673??27 kJ
⑶Q2?Q1?1????1000??1?0.673??327 kJ
?11??11??S?Q1????Q2????T1?T1??T0T2??1?1??1?1 ?1000???327?????0.09 kJ/K9801000300320????
L?T0?Siso?300?0.09?27 kJ
符合！
第六章 习题解答
6-1
???v???u???u???v????p???T?p??????????????p?T??v?T??p?T???T?v???p?T
???h???h???p???v????p???v?T?????????????T??v?T??p?T??v?T???p?????v?T
6-2 6-3
??p???v??R??R?cp?cv?T??T????????R?T?Tv?b??v??p???p?
???p??a?RT?du?cvdT??T??pdv??pdv?dv????2v?v?b????T?v?⑴
积分：
?u2?u1?T?11??a????v1v2?
?h2?h1?T??p2v2?p1v1??a?⑵
ds??11???v?1v2?
cvR??p?dT??dv?dv?T?Tv?b??v
?Rlnv2?bv1?b
2?s2?s1?T??p???v???p?cp?cv?T???T??????T?v?T?v??T?p??⑶
??v???p?????????T?v??T?p??p?????v?T??p?????v?T
RT2a??p?R??p??????23????vv??v?b???Tv?bT??v，
?Tcp?cv??R2?v?b?22RT?v?b?2a?3v?R2a?v?b?1?RTv32
6-4
ds????p???RT?du?cvdT??T??pdv?cdT??p?dvv????v?b????T?v?a ?cvdT?2dvv
cvcvR??p?dT??dv?dT?dv?T?TTv?b??v
dh?Tds?vdp
6-5
??h????T??s?p（湿蒸气区
T恒定）
6-6
??h???p??T?v??????s?T??s?T
??h???p??T?v??????s?v??s?v
??p????0??s?v
??0, ???s???v???p????0, ??????0??T?p??s?T??p?T
6-7
?q?cvdT?T?v21RT??p?dv?dv?v?b ??T?vv2?bv1?b
q?RTln?v?b?v?RTln??p???T???v???p???1????????????T?v??v?p??p?T??T?v1??v???v??T?p1??v????v??p?T???6-8
??v?????v??T?p
???p????T?du?cvdT??T??pdv?cdT??pv????dv??? ???T?v?⑴
???v??dh?cpdT??v?T???dp?cpdT??v?T?v?dp??T?p????⑵
ds?⑶6-9
cp??T?cpcv??T??cvdp?dv?dp?dv????T??p?vT??v?p?T?vT
ds?cv??p?dT???dvT??T?v
??2p???cv????T?2??0?v??T??T?v
cv与v无关，仅与T有关
6-10 Tds?cpdT?vdp Tds?cvdT?pdv
??v?T??s?T?v?v???????????p??p?Tp??p?Tp?T?
p??p?cp??T?cp?p?????????????v??v?sv??v?sv?cv?
???v???p?v?p???????????????j??p?T??v?sp?v?
q?RTlnv2?b20?0.03168?8.314?500?lnv1?b5?0.031686-11 ?5782.7 kJ/kmol?11??11??u?a????137.64?????20.6 kJ/kmol?520??v1v2?
w?q??u?5782.7?20.6?5762.1 kJ/kmol
ln6-12
p2r?11?2833.47?11?????????p1R?T1T2?0.4614?273.16258.15? ??1.3072
p2?p1e?1.3072?611.2e?1.3072?165.4
Pa
第七章 水蒸气
7-1当水的温度t=80℃，压力分别为0.01、0.05、0.1、0.5及1MPa时，各处于什么状态并求出该状态下的焓值。 解：查表知道 t=80℃时饱和压力为0.047359MPa。
因此在0.01、0.05、0.1、0.5及1MPa时状态分别为过热、未饱和、未饱和，未饱和、未饱和。焓值分别为2649.3kJ/kg，334.9 kJ/kg，335 kJ/kg，335.3 kJ/kg，335.7 kJ/kg。
7－2已知湿蒸汽的压力p=1MPa干度x=0.9。试分别用水蒸气表
和h-s图求出hx，vx，ux，sx。 解：查表得：h``＝2777kJ/kg v``＝0.1943m3/kg s``=6.5847 kJ/(kg.K)
u``= h``－pv``=2582.7 kJ/kg hx＝xh``+(1-x)h`=2575.6 kJ/kg vx＝xv``+(1-x)v`=0.1749 m3/kg ux＝xu``+(1-x)u`=2400 kJ/kg sx＝xs``+(1-x)s`=6.14 kJ/(kg.K)
7-3在V＝60L的容器中装有湿饱和蒸汽，经测定其温度t＝210℃，干饱和蒸汽的含量mv=0.57kg，试求此湿蒸汽的干度、比容及焓值。
解：t＝210℃的饱和汽和饱和水的比容分别为： v``＝0.10422m3/kg h``＝2796.4kJ/kg
mvxh`=762.6 kJ/kg
v`＝0.0011274 m3/kg u`＝h`－pv`=761.47 kJ/kg s`＝2.1382 kJ/(kg.K)
v`＝0.0011726 m3/kg
h`=897.8 kJ/kg
m?湿饱和蒸汽的质量：
V?xv``?(1?x)v`m
解之得： x=0.53
比容：vx＝xv``+(1-x)v`=0.0558 m3/kg 焓：hx＝xh``+(1-x)h`=1904kJ/kg
7－4将2kg水盛于容积为0.2m3的抽空了的密闭刚性容器中，然后加热至200℃试求容器中（1）压力；（2）焓；（3）蒸汽的质量和体积。
解：（1）查200℃的饱和参数 h``＝2791.4kJ/kg
h`=852.4 kJ/kg
v``＝0.12714m3/kg v`＝0.0011565m3/kg