自然循环热水锅炉水动力计算

1、自然循环热水锅炉水动力计算例题A1锅炉规范额定供热量Qsup：7.0MW额定工作压力P:1.0MPa回水温度tbac.w :70 C供水温度thot.w :115 C锅炉为双锅筒、横置式链条炉，回水进入锅筒后分别进入前墙、后墙、两侧墙和对 流管束回路中，两侧水冷壁对称布置，前墙和后墙水冷壁在3.2m标高下覆盖有耐火涂料层，如图A -1所示。图A-1锅炉简图A2锅炉结构特性计算A2.1前墙回路上升管划分为三个区段，第I区段为覆盖有耐火涂料层的水冷壁管， 第皿区段为未覆盖有耐火涂料层的水冷壁管，第用区段为炉顶水冷壁（图A-2）A2.2后墙回路上升管划分为二个区段，第I区段为覆盖有耐火涂料层的水冷壁

2、管，剩下的受热面作为第II区段（图A-3）A2.3侧墙水冷壁回路上升管不分段（图A-4）A2.4对流管束回路不分段，循环高度取为对流管束回路的平均循环高度，并设对流管束高温区为上升区域（共7排），低温区为下降区（共6排）。对流管束共 有347根，相应的上升管区域根数为191根，下降管区域根数为156根（图A-5）。对流管束总的流通截面积 Ao为:Ao=347 X 0.785 X 0.0442 = 0.5274 m 2下降管区域流通截面积 Adc为：Adc =156 X 0.785 X 0.0442 = 0.2371 m 2下降管区域流通截面积与对流管束总的流通截面积比Adc / Ao为:Adc

3、Ao_ 0.2371=0.5274=0.450其值在推荐值（0.44 0.48）的范围内图A-2前墙水冷壁回路图A-3后墙水冷壁回路图A4侧墙水冷壁图A5对流管束回路A2.5结构特性数据如表A-1所示表A-1结构特性数据截面积各区段长度各区段高度各区段弯头度数及个 数回路名称回路元件管径X壁厚管子根数单根管子整个回路与上升管截面积比Inm总长 度Inm总高度InmD x §nAAo/1112131h1h2h3hoena-na-nmm x mm/2 m2 m/mmmmmmmm(o )(o )(o )前墙水上升管51 x 3.5180.001520.02741.52.564.18.161

4、.022.461.214.6955 o -275o-1冷壁下降管108 X 420.007850.01570.579.124.6965 o -150 o -125 o -1后墙水上升管51 X 3.5180.001520.02746.142.999.133.012.425.43128 o-150 o 160 o -1冷壁下降管108 X 420.007850.01570.578.165.43o30130 o -1侧墙水上升管51 X 3.5140.001520.02135.005.00冷壁下降管108 X 420.007850.01570.748.345.00o751对流上升管51 X 3.5

5、1910.001520.29034.103.70o _30 e管束下降管51 X 3.51560.001520.23710.824.103.70o _30 eA3各循环回路局部阻力系数计算各循环回路局部阻力系数计算结果如表A-2所示表A-2各循环回路局部阻力系数计算序号名称符号单位计算公式及数据来源前墙水冷壁后墙水冷壁侧墙水冷壁对流管束JmIn上升管1入口阻力系 数匕in表 2-4、表 2-60.70.70.70.52出口阻力系 数-out表2-71.01.01.11.03弯头阻力系 数tb=KMo0.340.20.410.180.244总局部阻力 系数#rs.lcX- rs.lc = - i

6、n+ - out + ' b1.041.21.111.181.81.74下降管1入口阻力系 数表2-40.50.50.50.52出口阻力系 数-out表2-71.11.11.11.03弯头阻力系 数芦 -bb=K%o0.480.250.210.244总局部阻力 系数*dc.lcX- dc.lc = - in+ - out + ' b2.081.851.811.74A4各受热面吸热量分配由热力计算得，炉膛水冷壁平均热流密度 qav为107.67kW/m2,炉膛出口温 度为%ut.f = 893.6 C ,对流管束烟气出口温度6°ut.conv = 220 C ,对流管束

7、总的受热 面积为Ao=250.9m2,(其中上升管区域受热面积为 Ars=138.1m2),对流管束总吸 热量为3109.46kW(其中吸收来自炉膛的辐射吸热量为 Qfr =320.5kW)。设来自炉 膛的辐射热被对流管束高温区(即上升管区域)均匀吸收。设对流管束高温区与低温区分界处的烟气温度为9( C),贝爬为：(A-1)lgEt.f -t)-lg(%ut .convjAolg(Lut.f -t)-lg(U-t) 一 Ars式中：t 一对流管束内工质平均温度，C。t 可取为：t=0.5(thot.w + tbac.w )= 0.5 X (115+70) = 92.5 ( C ) 则由式(A-

8、1)得：lg( 893.6-92.5 )-lg( 220 -92.5) _ 250 .9lg( 893.6-92.5 )-lg( u-92.5) = 138.1求得： 6 = 383.8 ( C)则对流管束下降管区域所吸收的热量 Qcd为:Qd =Q H-"out.conv =(3109.46-320.5) x383.8-220 = 678.19(kW%d Uout.Lout.conv893.6-220(kW)上升管区域总吸热量Qcr：Qcr = Q - Q cd=3109.46-678.19=2431.27 (kW)表A-3给出了各受热面热量分配结果。表A-3各受热面热量分配结果名

9、 称符号单位前墙水冷壁后墙水冷 壁侧墙水冷壁对流管束下降管吸热QdckW000678.19上升管吸热量第I区QikW37.24227.21每侧862.11第II区Q2kW444.89912.71两侧1724.222431.27第m区Q3kW521.27A5.3各回路水循环计算A5.1各回路下降管入口水温的假设tin.dc= 0.5(thot.w + tbac.w ) = (115+70)/2 = 92.5 ( C)A5.2各回路中循环流量的假设假设四个回路中循环流量 Gi、G2、G3所对应的上升管中的流速约为：Gi -对应上升管水速 Wrs.1约为0.15 (m/s)G2 -对应上升管水速 W

10、rs.2约为0.20 (m/s)G3 一对应上升管水速约 Wrs.3为0.35 (m/s)贝U:Gi = 3600f PWrs.i (i=1 , 2, 3) (kg/h)Ars上升管流通截面积，m2；Wrs.i -假设的上升管水速，m/s ;P水的密度，kg/m3;Gi -与Wrs.i相对应的流量，kg/h。计算P时，对应的温度t可取为：t= (thot.w + tbac.w)/2 = (115+70)/2 = 92.5( C )P=1008.6263-0.2811t-0.0021921t 2 =1008.6263-0.2811 X 92.5-0.0021921 X92.52=963.87各回

11、路中的循环流量取值如表 A-4所示：表A-4各回路中的循环流量循环流量前墙回路后墙回路侧墙回路对流管束Gi (kg/h)150001500020000150000G2 (kg/h)200002500025000200000G3 (kg/h)250003000030000250000A5.3.1各回路水循环计算结果如表 A-5至A-8表A-5前墙水冷壁回路水循环计算结果名 称符号单位计算公式及来源计算结果tin.dc92.592.592.5回路循环流量Gkg/h假设值150002000025000下降管出口水温tout.dcCtout.dc =tin.dc +860 Qdc/G92.592.59

12、2.5下降管平均水温tav .dcCtav .dc =0.5( tin.dc + tout.dc )92.592.592.5下降管中水的平均伤ckg/Ac =1008.6263-0.2811963.87963.87963.87密度3 mtav .dc-0.002192 t2av.dc下降管中水速Wdcm/sWdc = G/(3600A dc 井c)0.2750.3670.459下降管沿程摩擦阻?udc0.02180.02110.0207力系数下降管总阻力系数Idcdc =7dc l/din+ZEdc.lc4.074.0043.97下降管流动阻力APfi.dcPa_"T二2APfl.d

13、c =岌 dc 用c W dc /2148.6260.1402.7下降管重位压降APst.dPaAPst .dc =h % g44346.644346.644346.6上升管各段出口水 温Ttout .1tout .1 = tout.dc + 860Q 1 /G=tout.dc +860 37.24 Gt out .2= tout .1+860Q 2/G94.6120.1494.1113.2393.8109.1it out .2C=tout .1+860 Xnt out .3444.89/G150.02135.64127.02mt out .3 = t out .2 +860Q 3/G=t o

14、ut .2+860 X521.27/G上升管各段平均水温t1Ct1 = 0.5(t out.dc + tout .1 )93.5693.393.14It2t2 = 0.5(t out .1 + t out .2 )107.4103.66101.4nmt3t3= 0.5(t out .2 + t out .3)135.08124.43118.05上升管各段水的平prs.1963.13963.3963.4均密度P r=1008.6263-0.2811 t 1I ns.1P rkg/3 m2 -0.002192 t i2prs.2953.16955.93957.56s.2=1008.6263-0.2

15、811 t 2930.65939.7944.9m2-0.002192 t 2 2P rs.3Prs.3=1008.6263-0.2811 t3-0.002192 t 3 2上升管中平均水温tav.rsctav.rs =0.5(t out.dc + t out .3 )120.26114.07109.76上升管中水的平均密度Pskg/3 mPs= 1008.6263-0.2811 tav.rs 2 -0.002192 t av.r s2942.3948.04951.36上升管中水的平均流速Wrsm/sWrs = G/(3600A rs FTs )0.16140.21380.2664上升管沿程摩擦

16、阻 力系数Zrs0.02780.0270.0264上升管总阻力系数MrsYrs =九 rsl/din + Ers.lc7.3957.2477.136上升管流动阻力 Pfl.r sPaPfl.rs = M rs 弁s Wrs / 290.74157.14240.9上升管各段重位压 降In mPst1 APst.2 Pst.3PaP st .1 = h 1 p rs.1 gAP st. 2 = h2 P rs.2 gP st. 3 = h3 p rs.3 g9637.323002.24 11046.969639.1523069.0511154.379640.323108.411216.0上升管侧总

17、压差PrsPaPrs =APfl.rs+APst1+ APst. 2+ AP st. 343777.2644019.744205.6下降管侧总压差P dcPaPdc = APst.dc- APfl. dc44197.9344086.4743943.87G (kg/h)laD(女 p.:'SR.:图A-6前墙水冷壁回路水循环特性曲线表A-7后墙水冷壁回路水循环计算结果名 称符号单位计算公式及来源计算结果tin.dc92.592.592.5回路循环流量GKg/h假设值150002500030000下降管出口水温tout.dcCtout.dc = tin.dc + 860 Qdc /G92.

18、592.592.5下降管平均水温tav .dcctav .dc =0.5( t in.dc + tout.dc )92.592.592.5下降管中水的平 均密度侣ckg/m3何c =1008.6263-0.2811tav .dc 2-0.002192 tav.dc963.87963.87963.87下降管中水速WdcM/s :Wdc = G/(3600A dc % )0.2750.4590.551下降管沿程摩擦阻力系数Adc0.02180.02070.0204下降管总阻力系 数戎dcdc =Mc l/d in+Wdc.lc3.633.543.51下降管流动阻力APfl.dcPaPfl.dc =

19、戊 dc 侑c W dc/2132.60359.18513.65下降管重位压降APst .dcPaPst .dc =h Rc g51343.751343.751343.7上升管各段出口 水温Intout .1t out .2Ctout .1 = tout.dc+ 860Q i/G227 21=tout.dc +860 G21t out .2= tout .1+860Q2/G,ccc 912.71=tout .1 +860-G105.53157.85100.316131.7199.01125.18上升管各段平均 水温Intl t2Ct1 = 0.5(t out.dc + tout .1 ) t2

20、 = 0.5(t out .1 + t out .2 )99.01131.6996.41 116.0195.75112.1上升管各段水的平均密度InP rs.1P rs.2kg/m3Prs.1=1008.6263-0.2811 t 12-0.002192 t i2Prs.2=1008.6263-0.2811 t 22-0.002192 t 2959.3933.6961.15946.5961.6949.57上升管中平均水 温tav.rs厂tav.rs =0.5(t out.dc + t out .2 )125.18112.10108.8上升管中水的平Rskg/mRs= 1008.6263-0.2

21、811939.09949.56952.06均密度3tav.rs 2-0.002192 t av.r s上升管中水的平 均流速Wrsm/sWrs = G/(3600A rs 9s)0.1620.2670.3194上升管沿程摩擦 阻力系数兀rs0.02760.02630.0259上升管总阻力系 数京rsSrs = krsl/din+Srs.lc8.0177.7477.66上升管流动阻力APfl.r sPaAPfl.rs = rs Ps Wrs / 298.71262.0372.3上升管各段重位 压降InAPst 1 APst.2Pa Pst .1 = hl P rs.1 gAP st. 2 = h

22、2 P rs.2 g28326.4 3 22163.6 928381.022470.428394.522543.0上升管侧总压差APrsPa Prs ="fl. rs+APst1+ APst. 250588.8451113.451309.86下降管侧总压差APdcPaAPdc = APst.dc- APfl. dc51211.150984.550830.0laD( lx p."ps._图A-7后墙水冷壁回路水循环特性曲线表A-8侧墙水冷壁回路水循环计算结果名 称符号单位计算公式及来源计算结果tin.dc92.592.592.5回路循环流量Gkg/h假设值2000025000

23、30000下降管出口水温tout.dcCtout.dc = t in.dc +860 Qdc /G92.592.592.5下降管平均水温tav .dcctav .dc =0.5( t in.dc + tout.dc )92.592.592.5下降管中水的平 均密度Qckg/m3化c =1008.6263-0.2811 tav .dc2 -0.002192 tav.dc2963.87963.87963.87下降管中水速Wdcm/sWdc = G/(3600A dc % )0.3670.4590.551下降管沿程摩擦 阻力系数Zjdc0.02110.02070.0204下降管总阻力系 数京dc#d

24、c=Zdc l/dinZ- dc.lc3.573.5363.51下降管流动阻力APfl.dcPa_u2 一APfl.dc = SSdc 色c W dc /2231.87358.90513.20下降管重位压降Pst .dcPaAPst .dc =h Fdc g47277.847277.847277.8上升管出口水温toutCtout = tout.dc + 860Q/G=tout.dc +860 862.11 G129.6122.2117.2上升管中平均水 温tav.rsCtav.rs =0.5(t out.dc + t out )111.0107.3104.85上升管中水的平 均密度kg/m3

25、Rs= 1008.6263-0.2811 tav.rs 2-0.002192 t av.r s950.4953.2955.05上升管中水的平 均流速Wrsm/sWrs= G/(3600A rs Rs )0.2740.3420.410上升管沿程摩擦 阻力系数孔rs0.02630.02580.0254上升管总阻力系 数五rsi s-rs = Arsl/din -rs.lc4.794.734.68上升管流动阻力Pfl.rsPaPfl.rs = - rs Rs Wrs / 2171.38263.88375.52上升管重位压降APstPaPst = h p rs g46616.646754.754684

26、5.2上升管侧总压差APrsPaAPrs =APfl. rs + APst46787.9847018.5947220.72下降管侧总压差PdcPaPdc = APst.dc- APfl. dc47045.946918.846764.68表A-8对流管束水循环计算结果名 称符号单位计算公式及来源计算结果:tin.dc92.592.592.5回路循环流量Gkg/h假设0250000下降管出口水温tout.dcCtout.dc =tin.dc +860 Qdc /G96.495.494.83下降管平均水温tav .dcCtav.dc =0.5( tin.dc + tout.

27、dc )94.493.9693.66下降管中水的平均密度fdc3 kg/mftc =1008.6263-0.2811 t av .dc2 -0.002192 tav.dc2962.50962.86963.06下降管中水速Wdcm/sWdc = G/(3600A dc Pdc)0.1830.2430.304下降管沿程摩擦阻 力系数Zdc0.02830.02720.0265下降管总阻力系数低dcydcdc l/din+Mdc.lc4.384.274.21下降管流动阻力APfi.dcPaAPfl.dc = Z- dc fdc W dc /270.20121.86187.50下降管重位压降Pst .d

28、cPaPst .dc =h 住c g34936.834949. 034956.4上升管出口水温toutCtout = tout.dc + 860Q/G=tout.dc +860 2431.27 G110.3105.87103.2上升管中平均水温tav.rsCtav.rs =0.5(t out.dc + t out )103.4100.699.0上升管中水的平均密度Rskg/m3Rs= 1008.6263-0.2811 tav.rs 2 -0.002192 t av.r s956.2958.1959.3上升管中水的平均流速Wrsm/sWrs = G/(3600A rs £s )0.15

29、0.200.25上升管沿程摩擦阻 力系数Xrs0.02870.02770.0269上升管总阻力系数此-rs = 7-rsl/din+E-rs.lc4.414.324.24上升管流动阻力Pfl.rsPaAPfl.rs = - rs Rs Wrs/ 247.5582.6126.6上升管重位压降 PstPaAPst = h p rs g34705.634777.334819.8上升管侧总压差PrsPaAPrs =APfl. rs+Pst34753.1434859.934946.5下降管侧总压差PdcPa Pdc = APst.dc- APfl. dc34866.634827.234768.94680

30、046700rd SI,p图A-8侧墙水冷壁图A-9对流管束水循环特性曲线A5.4计算结果由各回路水循环特性曲线，可以得到在假设的下降管入口水温下，回路工作点及工作点的流量，结果如表 A-9所示表A-9工质流量汇总表假设的下降管入口水温C前墙Gkg/h后墙 GKg/h侧墙 G (kg/h)对流管束G kg/h总和ZGkg/h一侧两侧92.521000231502360047200187550278900计算全炉循环倍率: 锅炉总的回水量 Gbac (kg/h)为:Q7000G bac = 860 = 860 X= 133778(kg/ h)bac t(115 -70)K=E G/G bac =

31、278900/133778=2.085由式 (4-18)得， 当 K>1.0, tin.dc =thot.w-(thot.w -tbac.w)/k=115-(115-70)/2.085=93.4 C,与假设的 tin.dc=92.5 C相差在 15C 以内。 因此，计算有效。A6循环回路中最低、最高水速的计算以前墙循环回路为例A6.1回路中受热最弱、最强管各段吸热量计算回路中受热最弱、最强管各段吸热量计算结果如表 A-11所示表A -11回路中受热最弱、最强管各段吸热量计算结果序号名称符号单位公式计算及数据 来源第I区第U区第m 区1平均工况下回路各段吸热 量QikW37.24444.8

32、9521.272回路中管子根数n1818r 18 i3受热最弱管最小吸热不均 匀系数min0.50.50.54受热最强管最大吸热不均 匀系数max1.31.31.35结构不均系数魅1.01.01.06受热最弱管吸热量QminikW岑in ?气 n1.03412.35814.48 07受热最强管吸热量Qmax,ikW£i?n. max c n2.69032.13137.647A6.2平均工况下管组两端压差确定由图A-6可知，平均工况下管组两端压差AP=44060 PaA6.3受热最弱管中两端压差计算管内流量(单根管，截面积为 A=0.00152 m2)假设Gi =500(kg/h) ,

33、 G2 = 800(kg/h) , G3 = 1200(kg/h)，两端压差计算结果见表 A-12。A6.4受热最强管中两端压差计算管内流量(单根管，截面积为A=0.00152 m 2)假设Gi =1000(kg/h) , G2 = 1400(kg/h) , G3 = 1800(kg/h)，两端压差计算结果见表 A-13。表A-12受热最弱管中两端压差计算结果名 称符号单位计算公式及来源假设流量kg/h假设流量 1Gkg/h5008001200下降管入口水温，tin.dcC93.493.493.4下降管出口水温tout.dcCtout.dc = tin.dc +860 Qdc/G93.493.

34、493.4上升管各段出口水，温tout .1ctout.1 =tout.dc+95.1894.5194.14Itout .2860Qmin,1/G116.43107.80103.0ntout .3t out .2 =tout.1141.34123.36113.37m+860Qmin,2/Gt out .3= t out .2+860Qmin,3/G上升管各段平均水温It1t1 = 0.5(t out.dc + tout .1 )94.2993.9693.77nt2ct2 = 0.5(t out .1 + t out .2)105.81101.1598.57mt3t3= 0.5(t out .2

35、+ t out .3)128.89115.58108.19上升管各段水的平均密度Inmp r s.1p r s.2p r s.3kg/m3Prs.1=1008.6263-0.2811 t 12-0.002192 t 12 prs.2=1008.6263-0.2811 t 22-0.002192 t 2 2962.63954.34935.98962.87957.76946.85962.99959.62952.56Prs.3=1008.6263-0.2811 t3 2 -0.002192 t 3 2上升管中平均水温tav.rsctav.rs =0.5(t out.dc + t out .3 )11

36、7.37108.38103.39上升管中水的平均密度Pskg/m3Ps= 1008.6263-0.2811tav.rs 2-0.002192 t av.r s945.44952.41956.13上升管中水的平均流速Wrsm/sWrs = G/(3600A o Rs)0.09660.15350.2294上升管沿程摩擦阻 力系数Xrs0.03020.02840.0271上升管总阻力系数Mrsrs = 7sl/din+WE rs.lc7.847.517.26上升管流动阻力Pfl.rsPa Pfl.rs = rs Ps Wrs / 234.6284.24182.73上升管各段重位压降InmAPst 1

37、 P st. 2 Pst. 3PaAPst .1 = h1 P rs.1 g P st. 2 = h2 P rs.2 g AP st. 3 = h3P rs.3 g9632.323030.811110.29634.623113.311239.39635.923158.211307. 0上升管两端总压差APrsPaAPrs =APfl.rs +APst 1+APst. 2 +APst. 343807.944071.444283.8表A-13受热最强管中两端压差计算结果名 称符号单位计算公式及来源假设流量kg/h100014001800下降管入口水温tin.dc°C93.493.493.

38、4下降管出口水温tout.dcctout.dc =tin.dc +860 Qdc /G93.493.493.4上升管各段出口水温Itout .1ctout.1=tout.dc+95.7195.0594.69ntout .2860Q max,1/G123.35114.79110.04mtout .3tout.2=tout.1+860Q max,2/G tout.3=tout .2 +860Q max,3 /G155.72137.92128.02上升管各段平均水温It1t1 = 0.5(t out.dc + tout .1 )94.5694.2394.04nt2ct2 = 0.5(t out .1

39、 + t out .2 )109.53104.92102.36mt3t3= 0.5(t out .2 + t out .3)139.53126.35119.03上升管各段水的平 均密度Inmp r s.1p r s.2p r s.33 kg/mprs.1=1008.6263-0.2811 t 12-0.002192 t 1prs.2=1008.6263-0.2811 t 22-0.002192 t 2Prs.3=1008.6263-0.2811t32-0.002192 t 3962.45951.54926.73962.68955.0938.11962.80956.88944.11上升管中平均水

40、温1tav.rsCtav.rs =0.5(t out.dc + t out .3 )124.56115.66110.71上升管中水的平均密度Rskg/m3Rs= 1008.6263-0.2811 tav.rs 2 -0.002192 t av.r s939.60946.79950.64上升管中水的平均流速Wrsm/sWrs = G/(3600A o Rs)0.19450.27020.3460上升管沿程摩擦阻 力系数Ars0.02700.02620.0257上升管总阻力系数西sWtrs = Arsl/din+lt rs.lc7.257.17.0上升管流动阻力Pfl.rsPaAPfl.rs = -

41、 rs Rs Wrs/ 2128.80245.40398.74上升管各段重位压降In mAPst 1 Pst. 2 Pst. 3PaAPst .1 = h1 p rs.1 gAP st. 2 = h2 p rs.2 gAP st. 3 = h3 P rs.3 g9630.4522963.1511000.329632.7423046.6911135.59634.0 2 23092.1 11206.7上升管侧总压差PrsPaAPrs=APfl.rs+APst.1 +APst.2+APst. 343722.744060.344331.6A6.5受热最弱管中工作点时水速Wrs, min的确定如图 A-

42、10a 所示,得到 Wrs, min 为 0.1497 (m/s)A6.6受热最强管中工作点时水速Wrs, max的确定如图 A-10b 所示,得到 Wrs, max 为 0.2702 (m/s)44400n m PS A44300442004410044000439004380043700W(m/s)(a)W (m/s)(b)图A-10受热最弱（a）、最强管（b）中水速的确定A7过冷沸腾的校验以前墙回路为例工作绝对压力：1.1(MPa)前墙水冷壁管内径:din= 0.044(m),管长l = 8.16 (m)上升管出口处倾角为：=75 0A7.1管内壁热流密度qn计算A7.1.1平均工况管管

43、子吸热量Qp=55.74 kWq'n=Qp/(兀 dn l ) = 55.74 / (3.14 X 0.044 X 8.16) = 49.44 (kW/m 2)贝U qn = J x C px q，n按第三章3.5.5节，取J= 0.9。由第三章式(3-30)计算可得：C宙1.2252、qn = 0.9 X 1.225 X 49.44 = 54.50(kW/m 2)A7.1.2受热最弱管管子吸热量Qmin = 27.87 kW2 qn,min=J C pQmin/(兀 dn l ) = 0.9 X 1.225 X 27.87/(3.14 X 0.044 X 8.16)=27.25 (kW/m 2)A7.1.3受热最强管管子吸热量Qmax=72.47kWqn,max =J C