化学工程基础习题答案（武汉大学 第二版）(3)

Re?du???7460.58 ，此时，2000

6?105??0.023?38.85?1.965?7460.58?(1?)1.87460.580.8

?1638Wm2??Cex7解：甲烷的定性温度：T?120?30?75?C 20℃条件下：??0.717Kg/m3 ??0.03W?m?1?K?1

??1.03?10?5Pa?s Cp?1.7KJ?Kg?1?K?1

由于甲烷是在非圆形管内流动，定性尺寸取de

de?4流体截面积润湿周边

??4?4?0.192?37??4?0.0192?0.0255??0.19?37???0.019

Re?du??Cp??0.0255?10?0.717?17728.7

1.03?10?5Pr??1.?103?1.03?10?5??0.584

0.03由于甲烷被冷却，n?0.3

??0.023?de(Re)0.8(Pr)0.3?0.023?0.03?(17728.7)0.8?(0.584)0.30.0255

?0.023?1.176?2505.77?0.851?57.1W?m?2?K?1若甲烷在管内流动：

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Re?du???0.015?10?0.717?10441.75 ?51.03?10??64.2W?m?2?K?1

Ex8 ?T1?40?15?25?C ，

?T2?130?33?97?C

?Tm??T2??T197?25??53.1?C（逆流） ?T297lnln25?T1在按照折流校正

33?15?0.16130?15

130?40R??533?15P?φ＝0.97

?Tm?0.97?53.1?51.5?C

ex9

(1)

??qmcp?T1?T2??1.25?1.9?10??80?30?3

?118750J?s?1(2) ?T1?30?20?10?C ，

?T2?80?40?40?C ?Tm??T2??T140?10??21.64?C ?T2ln4ln?T1(3)

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R??11d?d??0?0?Rsi?Rs0K?0?油di?dm10.0250.0025?0.025?3?3 ???0.21?10?0.176?10330.025?0.021.7?100.85?10?0.0245?0.025ln0.02?0.00251m2?K?W?1K?1?398.91W?m?2?K?1 R(4)

A??K?tm?118750395.91?21.64

?13.74m2若近似按平面壁计算，则

R??111????0?Rsi?Rs0K?0?油i?m110.0025?3?3 ???0.21?10?0.176?101.7?1030.85?10345K?453.26A?12.11m2

ex10

(1) d0?16?10?3m ，di?13?10?3m ，

??1.5?10?3m

?d0?d01??K?1?????d?d?0?m?ii??161.5?10?3?161??1??13?1000?40?14.5?90???? ?11.231?10?3?0.0414?10?3?0.011?81.5W?m?2?K?1??(2)

13

?d0?d01??K0?1?????d?d??m0??ii?161.5?10?3?161??1??13?1000?40?14.5?180?? ???146.6W?m?2?K?1(3)

?d0?d01??Ki?1?????d?d?0?m?ii??161.5?10?3?161??1??13?2000?40?14.5?90?????10.616?10?3?0.0414?10?3?0.011?85.78W?m?2?K?1??

ex11解：

(1)

''Cp ?1?qmcp?T1?T2??qm?T1'?T2'?

'' 50qmCp?25qmCp''qmCp?2qmCp .?Tm?135?60?92.5 135ln60A1??1k1?Tm?50qmCpk1?Tm

(2)

''?2?qmcp?t1?t2??qmCp?t1'?t2'?

''' 70qmCp?qmCpt1'?t2?? 14

''t1'?t2?35 ，t2?50

70qmCp?1135?30?tm??69.81 ，A2? ?135k?tk?t2m2mln30又流量及物性不变，k1?k2

k2?tm70?92.56475A2????1.855 50qCA150?69.83490.7mpk1?Tm70qmCpL2A2??1.855 ，L2?1.855m L1A1ex12解：(1)

?1?qmdcpd?T1?T2??KA?tm?1930?2.88?103?(90?50)?230?6??tm3600

?61.76?103?230?6??tm?tm?44.75?C

90?t?32?44.7590?t ln32t?29.5?C?Tm?.A1??1k1?Tm?50qmCpk1?Tm

?1?qmdcpd?T1?T2??qmhcph?t1?t2?61.76?103?qmh?4.2??29.5?18? qmh?1.279?103?4.6kg/h

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