换热器的设计1基本原理课件.ppt

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1、Dept. of Thermal Power Engineering NCEPUDept. of Thermal Power Engineering NCEPU参考书参考书1.1.换热器原理与设计换热器原理与设计，余建祖，余建祖 编著，北京航空编著，北京航空航天大学出版社，航天大学出版社，200520052.2.换热器换热器，秦叔经，秦叔经， 叶文邦等编叶文邦等编，北京，北京- -化学化学业出版社业出版社 2003 2003 3.3.电站锅炉空气预热器电站锅炉空气预热器，国家电力公司电力机，国家电力公司电力机械局械局编编，中国电力出版社中国电力出版社，2002 2002 4.4.换热器设计换热

2、器设计，毛希澜主编毛希澜主编，上海科学技术出上海科学技术出版社版社 19881988 5. 发电厂空冷技术发电厂空冷技术，丁尔谋主编，水利电力出，丁尔谋主编，水利电力出版社，版社，198819886.6.传热学传热学第四版，杨世铭、陶文铨第四版，杨世铭、陶文铨 编著，高等编著，高等教育出版社，教育出版社，20062006年年Dept. of Thermal Power Engineering NCEPUDept. of Thermal Power Engineering NCEPU换热器不仅是保证某些工艺流程和条件而广泛采用换热器不仅是保证某些工艺流程和条件而广泛采用的设备，也是开发利用工业二

3、次能源，实现余热回的设备，也是开发利用工业二次能源，实现余热回收和节能利用的主要设备。收和节能利用的主要设备。 Dept. of Thermal Power Engineering NCEPUDept. of Thermal Power Engineering NCEPUDept. of Thermal Power Engineering NCEPUDept. of Thermal Power Engineering NCEPUDept. of Thermal Power Engineering NCEPU优点：结构紧凑，以单位传热面积计优点：结构紧凑，以单位传热面积计算，价格比较便宜。不存在

4、永久性的算，价格比较便宜。不存在永久性的流动停止区域，因此表面具有自清扫流动停止区域，因此表面具有自清扫功能；缺点：主要是泄漏和携带，还功能；缺点：主要是泄漏和携带，还存在密封困难等问题。存在密封困难等问题。 Dept. of Thermal Power Engineering NCEPUDept. of Thermal Power Engineering NCEPUDept. of Thermal Power Engineering NCEPUDept. of Thermal Power Engineering NCEPUDept. of Thermal Power Engineering

5、NCEPUDept. of Thermal Power Engineering NCEPUDept. of Thermal Power Engineering NCEPUDept. of Thermal Power Engineering NCEPUDept. of Thermal Power Engineering NCEPUDept. of Thermal Power Engineering NCEPUDept. of Thermal Power Engineering NCEPUDept. of Thermal Power Engineering NCEPU在给定的工作条件（流体流量，进

6、口温度等）在给定的工作条件（流体流量，进口温度等）下，达到要求的传热量和流体出口温度。下，达到要求的传热量和流体出口温度。流体压降要小，以减少运行中的能量消耗；流体压降要小，以减少运行中的能量消耗；满足外形尺寸和重量的要求；满足外形尺寸和重量的要求；安全可靠，满足最高工作压力、工作温度以及安全可靠，满足最高工作压力、工作温度以及防腐、防漏、工作寿命等方面的要求；防腐、防漏、工作寿命等方面的要求；制造工艺切实可行，选材合理且来源有保证，制造工艺切实可行，选材合理且来源有保证，以减少初投资；以减少初投资；安装、运输以及维护方便等安装、运输以及维护方便等Dept. of Thermal Power

7、Engineering NCEPU换热器换热器设计指标设计指标总体布置：总体布置：选定类型、结构及材料选定类型、结构及材料流动形式流动形式传热表面传热表面热设计热设计传热计算传热计算流阻计算流阻计算优化分析优化分析传热表面的传热表面的工作特性工作特性几何参数几何参数流体及材料流体及材料的热物理的热物理性质性质结构设计：结构设计：构造、强度、振动、构造、强度、振动、密封、工艺、维修等密封、工艺、维修等可供选择的方案可供选择的方案评价和抉择评价和抉择评价依据评价依据择优条件择优条件最佳设计最佳设计Dept. of Thermal Power Engineering NCEPUDept. of Th

8、ermal Power Engineering NCEPU流体流体1 1的放热热流量的放热热流量 1 111111mq c ttW tt换热器的传热热流量换热器的传热热流量 m12m1fftkA ttkA tkA流体流体2 2的吸热热流量的吸热热流量 2222222mq cttWttDept. of Thermal Power Engineering NCEPUmmm1kttAk tRAkmmm1kttqk trk kkrA RK WkR2mK Wkr2f011mK/WrkkDept. of Thermal Power Engineering NCEPUif1f 2iwohhottRRRRRi

9、f1f 2iw11ohhoiottrrRrrAAf1f 2iwi1111oiooottrRrAhAhf1f 2ooA kttf1f 2iwi111ooooioottkArA RrAhhDept. of Thermal Power Engineering NCEPUDept. of Thermal Power Engineering NCEPUDept. of Thermal Power Engineering NCEPU0ln(/)2iwddRL间壁式换热器的总传热热阻间壁式换热器的总传热热阻 111wRh A热流体侧对流换热热阻热流体侧对流换热热阻wRA间壁的导热热阻间壁的导热热阻污垢热阻污

10、垢热阻ddddrRAA冷流体侧对流换热热阻冷流体侧对流换热热阻221wRh A流体与洁净肋片间的对流换热热阻流体与洁净肋片间的对流换热热阻01wRh ADept. of Thermal Power Engineering NCEPU典型间壁的传热热阻典型间壁的传热热阻 121111()() ddwrrkAAhh平壁平壁 0120ln(/)11111()() 2iddiddrrkAd LhLd L h圆管壁圆管壁 0120ln(/)11111()()2iddiddrrkAd L hLhA圆管壁外侧带肋片圆管壁外侧带肋片120011111()()ddwrrkAhAAhA平壁两侧带肋片平壁两侧带肋片

11、Dept. of Thermal Power Engineering NCEPU几种常见扩展表面的肋片效率：几种常见扩展表面的肋片效率： f实际散热量假想整个肋表面的温度处于肋根温度下的散热量0tanh()mHmHc2hPhmA对于等截面直肋：对于等截面直肋： fffh肋片效率的影响因素：肋片效率的影响因素：Dept. of Thermal Power Engineering NCEPU0tanh()mHmH-=(1+0.35ln)2fbfbdddHd等厚度环肋：（工程上常用的，简化的）等厚度环肋：（工程上常用的，简化的）管束外整体肋（制冷装置的蒸发器，空冷凝汽器）管束外整体肋（制冷装置的蒸发

12、器，空冷凝汽器） =bar=1.28-0.2ab顺排（矩形肋片）：顺排（矩形肋片）： =( -1)(1+0.35ln)2bdH叉排，三角形（六边形肋）：叉排，三角形（六边形肋）：=1.27-0.3ba Dept. of Thermal Power Engineering NCEPUrbabrbabDept. of Thermal Power Engineering NCEPU三、对数平均温差三、对数平均温差 Dept. of Thermal Power Engineering NCEPUDept. of Thermal Power Engineering NCEPUmmctfttmctft22

13、12ttPtt1122 ttRtt,f P RDept. of Thermal Power Engineering NCEPUDept. of Thermal Power Engineering NCEPUDept. of Thermal Power Engineering NCEPUDept. of Thermal Power Engineering NCEPUDept. of Thermal Power Engineering NCEPU2212ttPtt1122 ttRttDept. of Thermal Power Engineering NCEPU12121212(a):; (b):

14、ttttttttDept. of Thermal Power Engineering NCEPUDept. of Thermal Power Engineering NCEPU12mmqq、mkA t1111mpq ctt2222mpqcttDept. of Thermal Power Engineering NCEPU12hh、1111mpq ctt2222mpqcttmtmkA tDept. of Thermal Power Engineering NCEPU12,mmqq12,t t 12,t t mkA t1111mpq ctt2222mpqcttmt12,h hmkA tDept.

15、of Thermal Power Engineering NCEPU1 12500mq c 1360t 1300t 230t 2200t 1 1mq c22mq c1t2t2162t Dept. of Thermal Power Engineering NCEPU1 1112 222mmq c ttq ctt525003603001.5 10W22882 W/Kmqc 2222mq ctt5882162301.164 10WDept. of Thermal Power Engineering NCEPUmaxminmaxmin270 160210 K270lnln160mttttt 51 11

16、11.164 10Wmq ctt 2313t 31330360 162238 K31330ln360 162mtDept. of Thermal Power Engineering NCEPUmAk tmAkt5251.164 10800 210548 W/mK1.5 10238mmk tkt 42d11115.75 10mK/W548800rkkd5511238210-1.164 101.5 10mmttRAkAk-4= 6.45 10K/WDept. of Thermal Power Engineering NCEPUminmax12minmmq cttq cttmax12tttt12mi

17、nmq ctt12minmq cttDept. of Thermal Power Engineering NCEPUmminminmNTU()()mmkAkA tq cq ct1 12 2mmq cq c1112tttt1112ttttDept. of Thermal Power Engineering NCEPU1 1112222mmq c ttq ctt1 1221122()mmq cttttqc1112tttt1 112121222()()1()mmq cttttttqc12m1 112m22()11()ttq cttqc exp()ttkADept. of Thermal Power

18、Engineering NCEPUm1 1m221exp()1q ckAqcm1 1m221 exp()1kAq cqcm1 1m1m22m1 1m221111q cq cqcq cqcm1 1m1 1m22m1 1m221 exp11kAq cq cqcq cqcNTUDept. of Thermal Power Engineering NCEPUm1 1m22m1 1m221 expNTU 11q c qcq c qcm1 1m22m1 1m22m1 1m221 expNTU( 1/1/expNTU( 1/)q cqcq cqcq cqc1 exp( NTU) Dept. of Therm

19、al Power Engineering NCEPUm1 1m22m1 1m221 expNTU 11q c qcq c qc m1 1m22m1 1m22m1 1m221 expNTU( 1/1/expNTU( 1/)q cqcq cqcq cqc1 exp2NTU2NTU1NTUDept. of Thermal Power Engineering NCEPUm1 1m22m1 1m22ln11NTU1q c qcq c qc m1 1m22m1 1m2211NTUln11q c qcq c qcm1 1m22NTU,q cfqcDept. of Thermal Power Engineer

20、ing NCEPUDept. of Thermal Power Engineering NCEPUDept. of Thermal Power Engineering NCEPUDept. of Thermal Power Engineering NCEPUDept. of Thermal Power Engineering NCEPUDept. of Thermal Power Engineering NCEPUDept. of Thermal Power Engineering NCEPUDept. of Thermal Power Engineering NCEPU12mmqq、12hh

21、、1111mpq ctt2222mpqcttDept. of Thermal Power Engineering NCEPUmax12ttttminmaxmmq cq cminmaxNTU,mmq cfq cminNTU()mpkAq cDept. of Thermal Power Engineering NCEPUDept. of Thermal Power Engineering NCEPU12,mmqq12,t t 12,t t Dept. of Thermal Power Engineering NCEPU12,h hminNTU()mpkAq cminmaxNTU,mmq cfq c

22、max12ttttDept. of Thermal Power Engineering NCEPU1 111mq c tt2222mqcttDept. of Thermal Power Engineering NCEPUDept. of Thermal Power Engineering NCEPUDept. of Thermal Power Engineering NCEPUDept. of Thermal Power Engineering NCEPU60Dept. of Thermal Power Engineering NCEPU2 211221 1()43.13Cmmq cttttq

23、 cDept. of Thermal Power Engineering NCEPU311321s32 10 kg / 3 600 s987.3 kg/m15 0.001 344 mmqunA0.446 6 m/s1e1210.446 6 m/s 0.009 6 m78880.544 m /su dRe0.610.311ffe0.31hRePrd0.610.30.65 W/(m K)0.31 7 8883.4520.009 6 m27252W/(mK)Dept. of Thermal Power Engineering NCEPU322322s27 10 kg / 3 600 s994 kg/

24、m15 0.001 344 mmqunA0.374 m/s2e2220.374 m/s 0.009 6 m49080.732 m /su dReDept. of Thermal Power Engineering NCEPU0.610.422ffe0.31hRePrd0.610.40.6265 W/(m K)0.31 49084.8650.0096 m26707 W/(mK)Dept. of Thermal Power Engineering NCEPU112pf( 1/1/)khhRR14211(0.491 0.7) 107 252 6 7972 475 W/(mK)1212m112()()

25、ln()/()ttttttttt(43.1325) C(6045) C16.51 Cln(43.1325) C (6045) CDept. of Thermal Power Engineering NCEPUDept. of Thermal Power Engineering NCEPU2e224242u dRe0.610.4222ffe0.316513 W/(mK)hRePrd22112211()54.9Cmpmpq cttttq cDept. of Thermal Power Engineering NCEPU1e1210.446 8 m/s 0.009 6 m86220.497 5 m

26、/su dRe0.610.3211ffe0.317448 W/(mK)hRePrd1212pf( 1/1/)2458 W/(mK)khhRRDept. of Thermal Power Engineering NCEPUDept. of Thermal Power Engineering NCEPU21 111e2Lupfd320.8 m986.8 kg/m(0.4468 m/s)1.21615.643 kPa0.009 6 m222222e8.305 kPa2LupfdDept. of Thermal Power Engineering NCEPU112pf( 1/1/)khhRR22 47

27、5 W/(mK)223222 474.5 W/(mK) 5.597 mNTU0.4427.5 kg/s 4.174 10 J/(kg K) mkAq cm2 2m1 17.5 kg/s 4 174 J/(kg K) 8.89 kg/s 4 174 J/(kg K) 0.8438qcq cDept. of Thermal Power Engineering NCEPUm22m1 1m22m1 1m22m1 11 exp NTU(1)0.3141 ()exp NTU(1)qcq cqcq cqcq c2221225 0.31460 25 tttttDept. of Thermal Power En

28、gineering NCEPUDept. of Thermal Power Engineering NCEPU（1 1）判断流体流过所设计的换热器的总阻力是否）判断流体流过所设计的换热器的总阻力是否在允许范围内，或据此确定泵送流体流过换热器在允许范围内，或据此确定泵送流体流过换热器所需的压头，以便对输送流体的机械作出选择。所需的压头，以便对输送流体的机械作出选择。（2 2）对于有相变的情况，流阻造成的流体压力的）对于有相变的情况，流阻造成的流体压力的改变，将明显影响其工作的饱和温度，从而改变改变，将明显影响其工作的饱和温度，从而改变冷热流体之间的温差。传热计算中要考虑这一变冷热流体之间的温差。

29、传热计算中要考虑这一变化对传热的影响。化对传热的影响。Dept. of Thermal Power Engineering NCEPUmqpP流体流经换热器所克服的两类阻力：流体流经换热器所克服的两类阻力： 沿程摩擦阻力沿程摩擦阻力 进口、转弯、截面突变等局部阻力进口、转弯、截面突变等局部阻力Dept. of Thermal Power Engineering NCEPU2(,)42ceaeepudRLudd ( , , ,)ceapu dRL 表面粗糙度表面粗糙度022(Re,/)422caeepffRdLuudDept. of Thermal Power Engineering NCEPU

30、22aapu242ceuLpfd22aaupDept. of Thermal Power Engineering NCEPUcappp 3322333323234224 ReRe22mmmcaaecaaeeeqpggfLPAAdfLAAddd密度越大功耗越小（气体的泵送功耗比液体大得多）密度越大功耗越小（气体的泵送功耗比液体大得多）正比于质量流速和雷诺数的正比于质量流速和雷诺数的3 3次方次方各部分流阻的相对大小对换热面芯体流速分布的均匀各部分流阻的相对大小对换热面芯体流速分布的均匀性产生很大影响。性产生很大影响。Dept. of Thermal Power Engineering NCEPUmkA t1111mpq ctt2222mpqctt