W0??t,cQ1?0.6?1000?600 kJ < 700 kJQ??t?2,cQ1?0.3?5?10000?15000 kJ/h
该循环发动机不能实现 5-3
5-8
Q2?Q1?1??t??10000??1?0.3??7000 kJ/h q1?cp?T2?T1??1.01??1000?300??707 kJ/kgQ总?Q?Q2?15000?7000?22000 kJ/h
? ??1?T?ppT2q2?RT3ln3?RT3ln3?RT3ln?3?5-9 可逆绝热压缩终态温度 p1p2?T2??300? ?0.287?300?ln???1000?
1.41.4?1?p2??0.3?T?T?300??410.6??362.8 kJ/kg21?????0.1??p1?K
w?q1?q2?707?362.8?344.2 kJ/kg可逆过程Q??U?W?0，不可逆过程
w344.2Q??U??W??0 ????48.68%q1707 且W??1.1W，则?U??1.1?U
T?T1000?300?t,c?12??70%mcv?T2??T1??1.1mcv?T2?T1? T100015-4
T2??T1?1.1?T2?T1??300?1.1??410.6?300??421.7w??t,cq1?0.7?707?495 kJ/kg K
5-5 ⑴?T2?p2?421.70??S?mcln?Rln?0.1?1.01ln?0.287ln?p??T263T1p1?3000?Q2?2Q1??100000?89765 kJ/h?T1293
T293=0.00286 kJ/kg.K ?2,c?1??9.77T1?T2293?2635-10 理论制冷系数：⑵
P?Q1??1?1.4?11.4?2,c100000??2.84 kW9.77?3600?1,c?
制
P?T2258??7.37T1?T2293?258
⑶
冷
Q2机
?理论功率：
100000P?100000 kJ/h??27.78 kW3600 T293?2,c?1??14.65T1?T2293?2735-6 ⑴
P?Q1?1,c125700?4.74 kW7.37?3600
：
散热量
?2,c?20?1000?0.455 kW9.77?3600Q1?Q2?P?125700?4.74?3600?142756 kJ/h
冷却水量：
?T?T??1200TP2?12t2?203600由T1?T2℃
得
T1?313 K?40m?Q1142756??4867.2 kg/hcH2O?t4.19?7 ⑴
5-11
W1?Q1??U1?100?30?70 kJ℃
5-7
11
热源在完成不可逆循环后熵增
0.026kJ/kg.K
则第二个过程热源吸热：
5-15 ⑴
T1??1940 K，
T2??660 K
T2?660?1??66%?Q1??1940Q2?T??0.026??100?600?0.026?115.6 kJT1
?T?W?Q1??1000?66%?660 kJ⑵0
??1?工质向热源放热：
?T?600??W0,max?Q1?1?2??1000??1???700 kJT2000W?Q2??U2??115.6???30???85.6 kJ???1?
?W?W0,max?W0?700?660 kJ?40 kJ5-12 可逆定温压缩过程熵变：
p15-16
?s??Rln2??0.287?ln??0.66 kJ/kg?Kp10.1pV400?0.1m1?11??0.445 kg RT10.287?313 可逆过程耗功： pV200?0.1m2?22??0.238 kgp10.1w?RT1ln?0.287?400?ln??264 kJ/kgRT20.287?293
p21?U?m1cv?T?T1??m2cv?T?T2??0
mT?m2T20.445?313?0.238?293实际耗功：T?11??306 Km1?m20.445?0.238w??1.25w?1.25???264???330 kJ/kg
因不可逆性引起的耗散损失： ?m?m2?RT??0.445?0.238??0.287?306?0.3 MPap?1q??w??w??330???264???66 kJ/kgV1?V20.1?0.1
总熵变：
?S?m1?s1?m2?s2q?66?s???s???0.66???0.44 kJ/kg?K??Tp?Tp?T0300 ?m1?cpln?Rln??m2?cpln?Rln?T1p1?T2p2? ??3060.3?? ?0.445?1.01?ln?0.287?ln?3130.4??c?T?T?TT?1v3v1?1qw3060.3?????1?2?1?p31?1??31 ?1???0.2381.01ln?0.287?ln??0.0093 kJ/Kq1q1cv?T2?T1?T2T1?1p2?p1?12930.2??
pp2q1?RT1ln1T?T?400?2.5?1000 K21p2p5-14 ，15-17 ⑴
5-13
q1?cv?T2?T1?，
q2?cp?T3?T1?
q1?cv?T2?T1??0.723??1000?400??433.8 kJ/kg
pT1?T2p4v11cv?T1?T2??RT2ln4?Tln2lnq?RT?0.287?400ln??264.3 kJ/kg213p3??p3q2v103??1??1??1?ppq1 T1ln1RT1ln1p2p2⑵
w?q1?q2?433.8?264.3?169.5 kJ/kgq2?cv?T1?T2??RT2ln
12
p4p3
q264.3??1?2?1??39.0%q1433.8
5-18 ⑴
Ws?m?w?m?R?T1?T2???20??1
?p?T2?T1?2??p1?
w???1??0.2??800????1?1.4?11.4?505.1 K 20???1?20?1.4?1?T2??T1??298??258.2 Km?R0.5?1.4?0.287exu1?exu2?u1?u2?p0?v2?v1??T0?s2?s1?
?RT2RT1? ?cT?T?p??⑵v?12?0?pp?21???11.4?1?505.1800??p2?? ?218.8?100?0.2968???T2?T1???298?0.41.4?229.4 K??167.6 kJ/kg?2001000??p1?
R?T1?T2?0.2968??800?505.1???218.8 kJ/kg??11.4?1排开环境所作的功为作功能力损失R?T1?T2?0.287??298?229.4?Ws?m?w?m??0.5?1.4?（51.2kJ/kg） ??11.4?15-21 ?34.5 kW n?11.2?1n?p??0.2?1.25-19 T2?T1?2??800???611.8 K?n?1?1?1.3?1?p1?n?p2??1?1.3T2?T1???303???515.5 K ??0.1??p1?R?T1?T2?0.2968??800?611.8?w???279.3 kJ/kg
n?11.2?1n??1.3?1.40.287 q?cv?T2?T1?????515.5?303?n?11.3?11.4?1RT10.2968?8003v???0.237 m/kg1 ??50.8 kJ/kgp11000
RT20.2968?611.83v???0.908 m/kg2环境熵变：p2200q50.8 ?s1???0.175 kJ/kg?KT0290Tpp?RT2
?s?cpln2?Rln2?ln?Rln2TpT1p1??1T1p1?s2?cpln2?Rln2T1p1 1.4?0.2968611.80.2空气熵变： ?ln?0.2968ln?0.20 kJ/kg?K1.4?18000.1515.51?1.005?ln?0.287ln??0.127 kJ/kg ?K3030.1exu1?exu2?u1?u2?p0?v2?v1??T0?s2?s1?
R孤立系统熵变： ??T1?T2??p0?v2?v1??T0?s??1?siso??s1??s2?0.175?0.127?0.048 kJ/kg?K0.2968 ???800?611.8??100??0.908?0.237??300?0.21.4?15-20
?132.5 kJ/kg
13
?11??11??S?Q1????Q2???5-22 ?T1?T1??T0T2??1?1??1?1Q?mcp?T2?T1??13.94?1.005??600?500??1400.7 kJ ?1000???327?????0.09 kJ/K?9801000??300320?
T2600?s?cpln?1.005?ln?0.1832 kJ/kg?KL?T0?Siso?300?0.09?27 kJT1500 符
合！
Exq?Q?T0m??s?1400.7?300?13.94?0.1832?634.6 kJ
m?Anq?T0m??s?300?13.94?0.1832?766.1 kJ6-1
p1V1200?10??13.94 kgRT10.287?500
第六章 习题解答
5-23
???v???u???u???v????p???T?p????????????R?T1?T2?1.4?0.287??500?320???p?T??v?T??p?T???T?v????p?Tws???180.74 kJ/kg??11.4?1
???h???h???p???v????p????????v?T?Tp3200.1??????v?T??p?T??v?T??T?s?cpln2?Rln2?1.005?ln?0.287???ln??p???v?T??T1p15000.5
?0.0134 kJ/kg?K6-2
??p???v??R??R?exh1?exh2?h1?h2?T0?s2?s1??cp?T1?T2???scT?c?T?Tp0v?????????R??T?v??T?p?v?b??p? ?1.005??500?320??300?0.0134?184.92 kJ/kg
6-3 ⑴
ws180.74?ex???97.7%???p??a?RT?exh1?exh2184.92du?cdT?T?pdv??pdv?dvv?????? 2v?v?b????T?v?5-24 ⑴
T?300?20??1?2?1??67.3%?11??T11000?20u?u?a?????21T
?v1v2? 积分：T300?t?1?0?1??70%T11000?11?⑵ ?h2?h1?T??p2v2?p1v1??a???v1v2?? L?Q??????1000??0.7?0.673??27 kJ1t ⑶
⑵
ds?cvR??p?dT??dv?dv?T?Tv?b??v
v2?bv1?bQ2?Q1?1????1000??1?0.673??327 kJ
?s2?s1?T?Rln⑶
2??p???v???p?cp?cv?T???T???????T?v??T?v??T?p
14
??p?????v?T
??v???p?????????T?v??T?pR??p??????T?vv?b??p?????v?T
，
6-8
RT2a??p??????2??v?T?v?b?v3?Tcp?cv??R21??v???v??T?p???p???T???v???p???1????????????1??v???T?v??v?p??p?T??T?v???v??p?T
R1?2a?v?b?RTv32?v?b?22??v?????v?T??p ⑴
RT?v?b??2av3? 6-4
???p????T?du?cvdT??T??pdv?cdT??pv????dv?T??v????? ⑵
???p???RT?du?cvdT??T??pdv?cdT??p?dv??v??v?????v?bdh??cpdT??v?T????T?v???dp?cpdT??v?T?v?dp?T??p????a ?cvdT?2dv
v⑶
cp??T?cpcv??T??cvccvR??p?ds?dp?dv?dp?dvds?vdT??dv?dT?dv?????T?pT?v?T?vTT?TTv?b??p??v??v
c??p?6-5 dh?Tds?vdp ds?vdT???dvT?T??v 6-9 ??h????T??s?p??2p???cv?（湿蒸气区T恒定）
???T?2??0cv??v?T??T?v??h???p? 与v无
???T?v???s??s?T 关，仅与T有关 6-6 ??TTds?cpdT?vdp??h???p?6-10 ???T?v????s?v??s?v T d s ?vcd?Tpdv
?p????v?T??s?T?v?v???0???????s?v?????? ?ppp??T??p?Tp?T?
??s???v???p???0, ???????0, ???0p??p?cp??T?cp?p??T?p?s????????p??T??T???????v?sv??v?sv?cv?v?
???v???p?v?p?RT??p???????q?cvdT?T??dv?dv?????????j??p?T??v?sp?v?v?b??T?v 6-7
6-11 v2v2?bq?RTln?v?b?v?RTln1v1?b
15
工程热力学(第五版 - )课后习题答案（含题目）
