自然循环流量

一、题目：计算下面回路的自然循环流量。已知：闭合回路，水平边长2m,竖直边长6m,回路管道为不锈钢管，钢管Φ20×2。回路中充满单相水，系统压力为常压（绝对压强：1atm）。加热段为Φ10×1的不锈钢管，2m长，均匀加热。冷却器总损失系数假设为3（水头损失中速度按回路管内流速计算）。冷却器总长2m。设冷却器冷却功率恰好等于加热段加热功率，忽略回路对外界的散热损失。求：该回路自然循环时的流量。说明：可以使用换热中心假设。编程计算，程序语言不定，可以使用excel。加热段入口温度由同学自己设定，可以从20℃-50℃中任意选一个。加热功率2kW,5kW,8kW,10kW,任意选择两个。使用强制循环时相应公式，需要的公式和系数从有关书里查。解：1、基本说明1.符号：入口焓值：ih，入口密度：i，出口焓值：oh，出口密度：o，流量：mq，输入功率：q，驱动压头：dp，阻力压降：zp，雷诺数：AqVdmRe，6m4m2m2mheatercooler动压头：22222AqVm，平均密度：2_oi管径：3231108,1016dd面积：522242111003.541001.24dAdA,2.基本参数误差密度值：参考《分析化学用水密度表》，标准值。比焓值：参考《水和水蒸气热力性质图表》，插值数据最大误差0.2%。粘性系数：参考工程用推荐公式CTBA10，其中sPa10414.25A；K8.247B；K140C；T：热力学温度，K；为T对应密度值，㎏/m3。插值最大误差1.5%。2、阻力确定1.局部阻力确定弯头4个：冷段3个，热段1个，取ξ=0.88.024.222122121AqAqpomim突扩：16916811222212dd，参考速度为上游流速突缩：5.0，参考速度为下游流速5.0216922222222AqAqpimom冷凝器：ξ=3.03221_23Aqpm2.沿程阻力确定冷管段：管长8m，取入口密度，截面积1A，特征长度1diimimtAdqfAqp1132124101682热管段：管长4m，取出口密度，截面积1AoomomtAdqfAqp1132125101642加热段：管长2m，取平均密度，截面积2A，特征长度2d2108222_2322_26oimmttAdqfAqp3.沿程阻力系数计算：Re2320：Re64f2320Re4000：81.0Relg21ff4000Re1×105：25.0Re3164.0fRe1×105：237.0Re221.00032.0f4.阻力压降61iizpp3、驱动压头gLpoid)(4、迭代方式5、程序代码Publicm(0To50),e(0To50),n(0To50)AsSingle‘子块公用变量定义PrivateSubCommand2_Click()Text1.Text=Text2.Text=Picture1.ClsEndSubPrivateSubCommand3_Click()EndEndSubPrivateSubCommand1_Click()Picture1.Clsa1=2.01061929829747E-04'大管截面积m2a2=5.02654824574367E-05'小管截面积m2q=Val(Text1)tin=Val(Text2)hi=ttoh(tin)pi=ttom(tin)qm=q/(ttoh(100)-hi)l=qm/10000pd=2pz=1i=1re:If(pdpz)Thenqm=qm+lho=hi+q/qmtout=htot(ho)po=ttom(tout)p1=0.5*qm^2/a1^2*(2.4/pi+0.8/po)p2=0.5*qm^2/a2^2*(9/(16*pi)+1/(2*po))p3=0.5*qm^2/a1^2*(1.5/(pi+po))re=qm*0.016/(pi*a1*ttou(tin))p4=0.5*qm^2*500*f(re)/(pi*a1^2)re=qm*0.016/(po*a1*ttou(tout))p5=0.5*qm^2*250*f(re)/(po*a1^2)re=qm*0.008/((pi+po)*a2*ttou((tin+tout)/2)/2)p6=0.5*qm^2*250*f(re)/((pi+po)*a2^2/2)pz=p1+p2+p3+p4+p5+p6pd=(pi-po)*49.05/2i=i+1GoToreElseIf(i=2)ThenPicture1.PrintvbCrLfPicture1.Print不能建立单相自然循环EndIfIf(Abs(pd-pz)*100/pd=5Andi2)ThenPicture1.PrintvbCrLfPicture1.Print压力误差:;Spc(1);Format((pd-pz)*100/pd,0.000);%Picture1.Print循环次数:;Spc(1);Format(i,0);次Picture1.Print出口温度:;Spc(1);Format(tout,0.00);℃Picture1.Print出口焓值:;Spc(1);Format(ho,0.00);kJ/kgPicture1.Print出口密度:;Spc(1);Format(po,0.000);kg/m^3Picture1.Print循环流量:;Spc(1);Format(qm*1000,0.00);g/sPicture1.Print入口焓值:;Spc(1);Format(hi,0.00);kJ/kgPicture1.Print阻力压降:;Spc(1);Format(pz,0.00);PaPicture1.Print驱动压力:;Spc(1);Format(pd,0.00);PaPicture1.Print误差过大，请修正参数ElsePicture1.PrintvbCrLfPicture1.Print出口温度:;Spc(1);Format(tout,0.00);℃Picture1.Print出口焓值:;Spc(1);Format(ho,0.00);kJ/kgPicture1.Print出口密度:;Spc(1);Format(po,0.000);kg/m^3Picture1.Print循环流量:;Spc(1);Format(qm*1000,0.00);g/sPicture1.Print入口焓值:;Spc(1);Format(hi,0.00);kJ/kgPicture1.Print阻力压降:;Spc(1);Format(pz,0.00);PaPicture1.Print驱动压力:;Spc(1);Format(pd,0.00);PaPicture1.Print压力误差:;Spc(1);Format((pd-pz)*1000/pd,0.00);‰Picture1.Print循环次数:;Spc(1);Format(i,0);次EndIfEndSubPrivateSubForm_Load()Dimtin,tout,pi,po,hi,ho,re,q,qmAsSingle'入口温度，出口温度，入口密度，出口密度，入口焓值，出口焓值，雷诺数，功率，流量Dimp1,p2,p3,p4,p5,p6,pz,pdAsSingle'各项阻力Dimi,j,k,l,teAsSingleDima1,a2AsSingleOpenf:\密度值.txtForInputAs#1'密度数值表输入，2度一值，共51Forj=0To50LineInput#1,inputdatam(j)=Val(inputdata)NextjClose#1Openf:\比焓值.txtForInputAs#2'比焓值值表输入，2度一值，共51Forj=0To50LineInput#2,inputdatae(j)=Val(inputdata)NextjClose#2Openf:\粘性系数.txtForInputAs#3'粘性系数表输入，2度一值，共51Forj=0To50LineInput#3,inputdatan(j)=Val(inputdata)NextjClose#3EndSubFunctionhtot(h)j=0'由焓值求温度re:If(h=e(j)Andh=e(j+1))Thenhtot=2*j+2*(h-e(j))/(e(j+1)-e(j))Else:j=j+1GoToreEndIfEndFunctionFunctionttoh(t)k=Int(t/2)If(t=2*k)Thenttoh=e(k)Elsettoh=e(k)+(t/2-k)*(e(k+1)-e(k))/2'由温度求焓值EndIfEndFunctionFunctionmtot(p)j=0re:If(p=m(j)Andp=m(j+1))Thenmtot=2*j+2*(p-m(j))/(m(j+1)-m(j))Else:j=j+1GoToreEndIfEndFunctionFunctionttom(t)k=Int(t/2)If(t=2*k)Thenttom=m(k)Elsettom=m(k)+(t/2-k)*(m(k+1)-m(k))/2'由温度求密度EndIfEndFunctionFunctionttou(t)k=Int(t/2)If(t=2*k)Thenttou=n(k)Elsettou=n(k)+(t/2-k)*(n(k+1)-n(k))/2'由温度求粘性系数EndIfEndFunctionFunctionf(re)'沿程阻力系数计算If(re2320)Thenf=64/reElseIf(re2320Andre5000)Thente=15k=1re:If(Abs(k)0.000001)Thente=te-(te-2*Log(re*te)/Log(10)+0.8)/(1+1/(te*2.30258509299405))k=te-2*Log(re*te)/Log(10)+0.8GoToreEndIff=te^(-2)ElseIf(re5000Andre100000#)Thenf=0.3164/((re)^0.25)ElseIf(re100000#)Thenf=0.0032+0.221/(re^0.237)EndIfEndFunction6、计算结果20253035404550217.9018.7519.6516.0616.7817.2217.85521.9922.7823.4523.9324.5625.0325.57827.1328.0728.79--------1030.41------------注：功率：kW；温度：入口温度，℃；流量：g/s；“--”：单相循环不能建立；压力误差控制：5%。温度功率Pressure-droposcillationsaretriggeredbyastaticinstabilityphenomenon.Theyoccurinsystemsthathaveacompressiblevolumeupstreamof,orwithin,theheatedsection.MaulbetschandGriffith(1965,1967),intheirstudyofinstabilitiesinsubcooledboilingwater,foundthattheinstabilitywasassociatedwithoperationonthenegative-slopingportionofthepressuredrop-versus-flow