(11)第十章对流换热

1、1210-1 3xAq dAwfxxAhttdAwfwfxtttt常数wfxAtth dA1xAhh dAAwfxxxqhtt4 56711ppvvtt 8wf,hfuttcl910l310Knl l11uy0,xyxtqy 流体导热系数流体导热系数12wxxxqhtt0,yxty w0,xyxxthtty w0ythtty qx13dxxdyy02xDupFudx 2yDvpFvdy 2222xuuupuuuvFxyxxy2222yvvvpvvuvFxyyxy0uvxy14dxxdyy0 xh xdh x+ xdx+ xyh ydy+ ydh y+ yddhUptttcuvxy2222ttx

2、y2Dtatd 2tat 150uvxy2222xuuupuuuvFxyxxy2222yvvvpvvuvFxyyxyptttcuvxy2222ttxy1617w, , ,qf x y zwwqtnw, , ,tf x y z18190.99uul0yuy2056c2 10 3 10cuxRe5c5 10Re ww0.99ttttt21Prattt22tl、230uvxy2222xuuupuuuvFxyxxy2222yvvvpvvuvFxyyxyptttcuvxy2222ttxytl、yxuv240uvxy221uudpuuvxydxy ttuvxy22tayddddpuuxx 250uvxy2

3、2uuduuuvuxydxyttuvxy22tay212pu常常数数dpduudxdx 2627w0ythtty 0YlY w0YwtthttlY 0YhlY0YNuYww,ttxyuvXYUVlluutthlNu280uvxy22uuuuvxyyttuvxy22tay0UVXY221UUUUVXYReY221UVXYRe PrYu lRe(, ,)Uf X Y Re(, ,)Vf X Y Re(, ,)f X Y Re,Pr0YNuY,Nuf Re Pr29,Nuf Re Prwf,hfuttcl1/25.0 xRexxu xRe30w,0,xyxuy2f,2xucf,xcff,01dlxc

4、cxl1/2f,22lClc1/201dlCxxlu lRe1/2f,0.664xxcRe1/2f1.328cRe1/3tPrxu xRe311/21/30.332xxxh xNuRePr01dlxhhxl1/201 dlC xxl1/22 2x lC lh22lx lhlhlNuNu1/21/30.664NuRePrmw12tttxu xRe321/21/30.453xxNuRePr1/21/30.332xxNuRePrwxxfxqh ttq常数wfxtt常数ww01dlffxttttxl01dlxqxlh0dlxqxxlNuhlNu1/21/30.680NuRePr1/21/30.664N

5、uRePrwfqltt20dlxlxxNu33221UUUUVXYReY221UVXYRe PrY34pNuhStRePrC u1/21/30.664NuRePr2/31/20.664St PrRe1/2f1.328cRe2/3f2cSt Prf2cSt 3536,ABC ,AAAC ,BBBC ,CCCC,ABCCCC37312123 TCTC/,/TT38312123lrrrRdlCrrrRdllC/,/rR rR 39 30121230uuuuuCuuuuuC0/u u331122000000,uuuuuuuuuuuu40w0 ythtty 0wythtty ,lxylCxyl hhCh

6、0hlwyC CthCtty ww ,ttttCCttt1hlC CC h lh l NuNu41Re = Re ,Pr = Pr42434445nmNuf Re , PrCRe PrnNuf RecRelglglgNucnRehlulNuRe、wfhA tt46nmNuCRe Pr4748 m2300u dRe4230010Re410Re 4964fRe2m2lupfd 50wwf0ttx ttwftt、wwfwfr Rr Rtttrrttttwfwfwfxxxhttqhttttxh 510.05tlRePrd0.05lRed52xxxqht,xxht 53 lnttttt 0.5/2tt1

7、2ttt 545556ce4AdP570.141/3ffffw1.86dNuRe Prlf0.4816700Pr0.141/3fffw2dRe Prlfw0.00449.75580.8fff0.023nNuRePrwfwf0.40.3ttntt4f10 , /60Rel df0.7160 ,Pr0.140.81/3ffffw0.027NuRePr4ff0.716700 ,10,/60PrRel d592/3ff1/22/38100011 12.781tfRePrdNuclfPr6ff0.52000 , 23005 10PrRe 2f0.79ln1.64fRe0.45ffww, 0.51.5tT

8、TcTT0.11ffww, 0.0520tPrPrcPrPr600.452/30.80.4ffffw0.02141001dTNuRePrlT6fffw0.61.5, 0.51.5, 230010TPrReT0.112/30.870.4ffffw0.0122801dPrNuRePrlPr6fffw1.5500 , 0.0520 ,230010PrPrRePr612/3ff8fStPrffffpNuhStRe PrC u621/21/30.332xxNuRePr1/21/30.664NuRePr1/21/30.453xxNuRePr1/21/30.680NuRePr55 10 xRe 0.5100

9、0Pr4/51/30.0296xxNuRePr4/51/30.0308xxNuRePr0.660Pr575 1010 xRe63,l,t01ccxlxxxhh dxh dxl4/51/30.037871NuRePr0.660Pr575 1010 xRemw12ttt64u dRe65551.2 10Re80 8551.2 10Re 14066h dNuwnmNuCRe PrPr Pr60.7500, 110PrRe67wnmNuCRe PrPr Pr9030 9021 0.54cos 680.250.36ffffwmnPrNuCRe PrPr6ff12 100.6500RePr、906970w

10、0ythtty 0uvxy22xuudpuuvFxydxyttuvxy22tayxFg dpgdx 7122uuuuvgxyyg11ppvvtt 1tt tt22uuuuvgxyy 72w00w,ttxyuvXYUVlluutt22uuuuvgxyy 2212UUGrUUVXYReReY32gtlGr730UVXY221UVXYRe PrY2212UUGrUUVXYReReY0YNuY2/Gr Re2/Gr Re(,)Nuf Re Gr Pr2/1Gr Re (,)Nuf Re Pr2/1Gr Re (,)Nuf Gr Pr74f f TT1/44xGryx1/22xuxfGr ttttT*w

11、75tRaGr Pr76()nnNuC GrPrcRamw12ttt壁面形状与位置 流动情况 特征长度 Cn适用范围GrPr 垂直平壁或圆柱 壁面高度 0.59 0.101/4 1/3 水平圆柱 圆柱外径d0.850.480.1250.1881/41/3 4910 1091310 102410 104710 1071210 10774710 1071110 1051110 10水平热壁上面或水平冷壁下面平壁面积与周长之比A/U圆盘取0.9d0.54 0.15 1/4 1/3 水平热壁下面或水平冷壁上面平壁面积与周长之比A/U圆盘取0.9d 0.27 1/4 1/435dHGr7843w22xxxxh xg q xgtx