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目录一、方案简介································································1二、方案设计································································21、确定设计方案·····························································22、确定物性数据·····························································23、计算总传热系数···························································34、计算传热面积·····························································35、工艺结构尺寸·····························································46、换热器核算·······························································5三、设计结果一览表··························································8四、附图(主体设备设计条件图)(详情参见图纸)································8五、参考文献································································9六、主要符号说明····························································9七、心得体会·································································10附图··········································································1一、方案简介本设计任务是利用冷流体(水)给硝基苯降温。利用热传递过程中对流传热原则,制成换热器,以供生产需要。下图(图1)是工业生产中用到的列管式换热器.选择换热器时,要遵循经济,传热效果优,方便清洗,复合实际需要等原则。换热器分为几大类:夹套式换热器,沉浸式蛇管换热器,喷淋式换热器,套管式换热器,螺旋板式换热器,板翅式换热器,热管式换热器,列管式换热器等。不同的换热器适用于不同的场合。而列管式换热器在生产中被广泛利用。它的结构简单、坚固、制造较容易、处理能力大、适应性大、操作弹性较大。尤其在高压、高温和大型装置中使用更为普遍。所以首选列管式换热器作为设计基础。2二、方案设计某厂在生产过程中,需将硝基苯液体从100℃冷却到45℃。处理能力为1.5×105吨/年。冷却介质采用自来水,入口温度30℃,出口温度40℃。要求换热器的管程和壳程的压降不大于10kPa。试设计能完成上述任务的列管式换热器。(每年按330天,每天24小时连续运行)1.确定设计方案(1)选择换热器的类型两流体温度变化情况:热流体进口温度100℃,出口温度45℃冷流体。冷流体进口温度30℃,出口温度40℃。从两流体温度来看,估计换热器的管壁温度和壳体壁温之差不会很大,因此初步确定选用固定管板式换热器。(2)流动空间及流速的确定由于硝基苯的粘度比水的大,因此冷却水走管程,硝基苯走壳程。另外,这样的选择可以使硝基苯通过壳体壁面向空气中散热,提高冷却效果。同时,在此选择逆流。选用ф25×2.5的碳钢管,管内流速取ui=0.5m/s。2、确定物性数据定性温度:可取流体进口温度的平均值。壳程硝基苯的定性温度为:℃=+=5.72245100T管程流体的定性温度为:℃=+=3524030t根据定性温度,分别查取壳程和管程流体的有关物性数据。硝基苯在72.5℃下的有关物性数据如下:密度ρo=1153kg/m3定压比热容cpo=1.559kJ/(kg·℃)导热系数λo=0.129W/(m·℃)粘度μo=0.000979Pa·s冷却水在35℃下的物性数据:密度ρi=994.3kg/m3定压比热容cpi=4.24kJ/(kg·℃)导热系数λi=0.618W/(m·℃)粘度μi=0.000818Pa·s3.计算总传热系数(1)热流量热流体的流量Wo=1.5×105×1000÷330÷24≈18939kg/h热流量Qo=WocpoΔto=18939×1.559×(100-45)=1623925kJ/h=451kW(2)平均传热温差3逆流操作硝基苯:100℃→45℃水:40℃←30℃℃5.32304540100ln)3040()45-100(ln't2121ttttm(3)冷却水用量hgQWO/k38300304024.41623925tcipii)((4)总传热系数K管程传热系数12155000818.03.9945.002.0pudiiiieR4.0iipi8.0iiiiiiicpudd023.0)()(4.038.0618.0000818.0104.241215502.0618.0023.0)(℃)(m/1.2625W4、计算传热面积壳程传热系数假设壳程的传热系数αo=398W/(m2·℃);23m''87.345.320.39810451tmKQS考虑15%的面积裕度,S=1.15×S''=1.15×34.87=40.1m25、工艺结构尺寸(1)管径和管内流速及管长选用ф25×2.5传热管(碳钢),取管内流速ui=0.5m/s,选用管长为3m(2)管程数和传热管数依据传热管内径和流速确定单程传热管数根实1703025.014.31.40ldosAN按单程管计算其流速为4smW/2.0417002.014.3)3.9943600/(383004nd3.9943600/u2s2ii)(按单管程设计,流速过小,宜采用多管程结构。则该换热器管程数为22.05.0uuipN(管程)传热管总根数N=340(根)(3)平均传热温差校正及壳程数平均传热温差校正系数5.5304045100R14.0301003040P按单壳程,双管程结构,温差校正系数应查有关图表。可得95.0t平均传热温差℃9.305.3295.0t'tmmt(4)传热管排列和分程方法采用组合排列法,即每程内均按正三角形排列,隔板两侧采用正方形排列。取管心距t=1.25d0,则t=1.25×25=31.25≈32(mm)横过管束中心线的管数根213.203401.1CN(5)壳体内径采用多管程结构,取管板利用率η=0.7,则壳体内径为mm5.7407.03403205.1t05.1ND圆整可取D=740mm(6)折流板采用弓形折流板,取弓形折流板圆缺高度为壳体内径的25%,则切去的圆缺高度为h=0.25×740=185mm,故可取h=185mm。取折流板间距B=0.3D,则B=0.3×740=222mm,可取B为222。折流板数NB=传热管长/折流板间距-1=3000/222-1=12块折流板圆缺面水平装配。(7)接管壳程流体进出口接管:取接管内硝基苯流速为u=1.0m/s,则接管内径为m076.00.114.311533600/189394u4d1)(V5取标准管径为76mm×2.5mm。管程流体进出口接管:取接管内冷却水流速u=1.5m/s,则接管内径为m095.05.114.33.9943600/383004d2)(取ф108mm×5mm无缝钢管。6.换热器核算(1)热量核算①壳程对流传热系数对圆缺形折流板,可采用凯恩公式14.0w3/155.0oeored36.0)(PR当量直径,由正三角形排列得m020.0025.014.3)025.04032.023(4)423(42222ooeddtd壳程流通截面积m0359.0032.0025.01740.0222.0td1oo)()(BDS壳程流体流速及其雷诺数分别为2991000979.01153127.002.0e/m127.00359.011533600/18939uooRs)(普兰特准数8.11129.0000979.010559.1r3P粘度校正114.0w)(℃)(23/155.0om/43118.11299102.0129.036.0W②管程对流传热系数4.08.0iiired023.0PR管程流通截面积22im0543.02/34002.0)4/14.3(S管程流体流速61.4862000818.03.9942.002.0Res/m2.00543.03.9943600/38300uii)(普兰特准数℃)24.08.0i3/(1.12606.51.486202.0618.0023.06.5618.0000818.01024.4rmWP③传热系数K污垢热阻Rsi=0.000344m2·℃/W,Rso=0.000172m2·℃/W管壁的导热系数λ=45W/(m·℃)℃)(++++++++2osomoioiiiom/5.2514311000172.00225.045025.00025.0020.0025.0000344.0020.01.1260025.011dbddddd1WRRK④传热面积S23m''2.555.3225110451tmKQS该换热器的实际传热面积Sp2opm5.78340)06.03(025.014.3ldNS该换热器的面积裕度为%422.552.555.78%100''pSSSH传热面积裕度合适,该换热器能够完成生产任务。(2)换热器内流体的压力降①管程流动阻力∑ΔPi=(ΔP1+ΔP2)FtNsNpNs=1,Np=2,Ft=1.52u2udl222i1PP,由Re=4862.1,传热管相对粗糙度0.01/20=0.005,查莫狄图得λi=0.0317W/m·℃,流速ui=0.2m/s,ρ=994.3kg/m3,所以ak10a6.45625.17.595.92a7.5922.03.9943a5.9222.03.99402.03031.0i2221PPPPPPP<)(管程压力降在允许范围之内。②壳程压力降15.1s,1s'2'1oFNsNsFPPP)(流体流经管束的阻力PaPuNnfFuNnFfPoBcooBco4.10232127.01153)112(218063.05.0127.0,12,218063.0299155.02)1(2'1228.02'1流体流过折流板缺口的阻力ak101.154915.116.3234.1023a6.3232127.01153)740.0222.025.3(122)25.3(740.0,222.02)25.3(o22'22'2PPaPPuDBNPmDmBuDBNPoBoB<)(总压力降壳程压力降也比较适宜。8三、设计结果一览表换热器形式:固定管板式换热面积(m2):78.5工艺参数名称管程壳程物料名称冷却水硝基苯操作压力,Pa未知未知操作温度,℃30/40100/45流量,kg/h3830018939流体密度,kg/m3
本文标题:列管式换热器的设计讲解
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