热工基础第十章对流换热

1、1第十章 对流换热210-1 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+ yddhuptttcuvx

2、y2222ttxy2dtatd 2tat 150uvxy2222xuuupuuuvfxyxxy2222yvvvpvvuvfxyyxyptttcuvxy2222ttxy1617w, , ,qf x y zwwqtnw, , ,tf x y z18190.99uul0yuy2056c2 10 3 10cuxre5c5 10re ww0.99ttttt21prattt22tl、230uvxy2222xuuupuuuvfxyxxy2222yvvvpvvuvfxyyxyptttcuvxy2222ttxytl、yxuv240uvxy221uudpuuvxydxy ttuvxy22tayddddpuuxx

3、250uvxy22uuduuuvuxydxyttuvxy22tay212pu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,xcf

4、f,01dlxccxl1/2f,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 xre321/21/30.453xxnurepr1/21/30.332xxnureprwxxfxqhttq常数wfxtt常数ww01dlffxttttxl01dlxqxlh0dlxqxxlnuhlnu1/21/30.680nurepr1/21/

5、30.664nureprwfqltt20dlxlxxnu33221uuuuvxyrey221uvxyre 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 ,lxylcx

6、yl hhch0hlwyc 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

7、.5/2tt12ttt 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

8、.51.5tttctt0.11ffww, 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

9、 0.51000pr4/51/30.0296xxnurepr4/51/30.0308xxnurepr0.660pr575 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、

10、906970w0ythtty 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

11、ttttt*w75tragr 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