第六章_224105500

1、12第一节第一节 管管内受迫对流换热内受迫对流换热m2300u dRe4230010Re410Re mcVquA32m0( )2 1u rrur0m( )2u ru464fRe2m2lupfd /0.05l dRe1 51/440.3162 10ddfReRe260.790ln1.6430005 10ddfReRe 1 6wmtt、xh wwm( )( , )0( )( )txt x rxtxtxwwmwm( )( , )(/)( )( )r Rr Rtxt x rtrrtxtxtt 常数wm(/)xr Rhtrtt 780.05tlRePrd0.05lRed0.07tlRePrd9ccm20

2、m( , )( , )2( , )pRApAc u x rt x r dAtturdrR uc u x r dAwm( )( )xxxxqhtxtxhtwfm()A httA ht 10 xxxqht,xxht m12ttt 11m lnttttt 0.5/2tt12ttt 1213R1 1.77dR 3R1 10.3dR 140.8fff0.023nNuRePrwfwf0.40.3ttntt4f10 , /10Rel df0.7160 ,Pr150.140.81/3ffffw0.027NuRePr4ff0.716700 ,10,/60PrRel d0.250.80.43ffffw0.021P

3、rNuRePrPr46ff0.6700, 101.75 10 ,/60PrRel d162/3fff1/22/3f8100011 12.781tfRePrdNuclfPr56ff0.610, 230010PrRe2f1.82ln1.64fRe0.45ffww, 0.51.5tTTcTT0.11ffww, 0.0520tPrPrcPrPr170.452/30.80.4ffffw0.02141001dTNuRePrlT6fffw0.61.5, 0.51.5, 230010TPrReT0.112/30.870.4ffffw0.0122801dPrNuRePrlPr6fffw1.5500 , 0.05

4、20 ,230010PrPrRePr182/3ff8fStPrffffmpNuhStRe PrC u2wm8fu64fRe22lg1.74sRfk2m2lupfd 常用工业管道的摩擦系数常用工业管道的摩擦系数2021ce4AdPd2d12221e212144ddddddd220.141/3ffffw1.86dNuRe Prlf0.4816700Pr0.141/3fffw2dRe Prlfw0.00449.752324u dRe25w0uy551.5 10Re808551.5 10Re 14026h dNu1/3nhdNuCRePrwm2tttu dRe270.25ffffwmnPrNuCRe

5、PrPr60.7500, 110PrReff10:0.37;10:0.36PrnPrnRef284/55/81/21/31/42/30.620.3128200010.4/RePrReNuPr0.2dRePrwm2ttt1/21/301.15NuRePr299030 9021 0.54cos 0.25ffffwmnPrNuCRe PrPr30S1S2S1S2310.25p0.36f1fffzw2PrRe PrPrnSNuCS( Z20 )329033wfttwftt34xFg fdpgdx 22taywf0ythtty 0uvxy22xuudpuuvFxydxyttuvxy352f2uuuuvg

6、xyyfg11ppvvtt ff1tt fftt22uuuuvgxyy 36f00wf,xyuvttXYUVlluutt22uuuuvgxyy 2wf2201gttlUUUUVXYuRe Y23wfwf0220gttlgttlu lGru2GrRe370UVXY221UVXYRe PrY2212UUGrUUVXYReReY0YNuY2/Gr Re2/1Gr Re (,)Nuf Re Gr Pr2/1Gr Re (,)Nuf Re Pr2/1Gr Re (,)Nuf Gr Pr3839twtf40tRaGr Pr41()nnNuC Gr PrcRamwf2ttt自模化自模化hlNu3wf2gtt

7、lGr4221/6HH8/279/160.3870.82510.492RaNuPr112H1010Ra1/4HH4/99/160.6700.6810.492/RaNuPr9H10Ra 4343w22xxxxh xg q xgtxGrGrNu 1/50.60 xxNuGrPr5111010 xGrPr1/40.17xxNuGrPr13162 1010 xGrPrm,xw,xf12ttt441/435dHGrhh圆柱竖壁454621/6dd8/279/160.3870.6010.559/RaNuPr12d10Ra 1/61/3ddd0.360.3630.0914NuGrGrwfm2ttt613d1

8、01.3 10Gr1/61.076(*)NuGr Pr586.37 10*1.12 10Gr1/60.747(*)NuGr Pr586.37 10*1.12 10Gr481/4dd4/99/160.589210.469/RaNuPr11d10,0.7RaPr49夹层厚度夹层厚度 与高度与高度 H 之之比比 /H 0.3 , ,自然对流边界层自然对流边界层不会互相干扰不会互相干扰, , 按无限空间按无限空间自然对流换热计算。自然对流换热计算。 /H 2000，夹层内冷、热壁上两边界层相夹层内冷、热壁上两边界层相互影响，行成若干个环流。互影响，行成若干个环流。Gr 2000，夹层内没有自然对流，按导热夹层内没有自然对流，按导热计算，相当于计算，相当于Nu = 1。50Gr 1700，Gr 105，Gr Pr 1700/cos 时，时，也会出现也会出现51ew1w2()qh ttw1w2()Nuttew1w2()tteNu()mnHNuC