管线绝热层厚度计算方法集粹.pdf

管线绝热层厚度计算方法集粹张礼贵(中国石化金陵石化工程有限公司,江苏南京,210033)摘要:介绍了确定管道绝热层厚度的基本方法,分析了每种方法的适用条件,对常用的管线用计算机程序进行了计算,并列表给出了计算结果。关键词:管道 绝热 厚度 温度 为了满足工艺要求,减少散热损失,一般热力管道需采取绝热措施(保温或保冷)。正确地计算绝热层厚度,可以在合理的投资范围内减少设备、管道及其组成件在工作过程中的热量或冷量损失以节约能源。笔者在此对工程中常用的几种绝热层厚度计算方法进行分析,并用PASCAL语言编制了计算程序,对常用的管线进行了计算,并列表给出计算结果,供同行们选用时参考。1 根据介质允许温降确定绝热层厚度在某些工艺过程中,对管道未端的介质温度有一定的限制要求,这时管内介质的温降往往是限定的,其管道允许的散热损失也随之被确定。这类管道一般采用稳定传热的热平衡方法计算绝热层厚度,其计算顺序如下。1.1 确定介质温降t一般情况下,t()是已知的。例如,金陵公司热电厂向炼油厂供汽工程中有一段中压蒸汽线,管径为 27314,流量40t/h,长度约1200m,起点温度为415。炼厂用汽设备为背压透平,其供汽母管温度要求 400。此例中t=15。1.2 允许单位散热损失q根据介质的流量G(t/h)、比热C(kJ/kgK)、允许温降t()、管线长度l(m),可以计算出q(W/m),公式为:q=CG t)1000/(3.6l)对于上例,q=2.074000015/(3.61200)=287.5(W/m)。1.3 确定隔热材料导热系数1上例中保温材料选用的是轻质镁铝管壳,其导热系数方程为=0.0534+0.000114tm,式中,tm为保温材料内外表面的平均温度。在计算tm时,保温材料内表面温度可近似取介质的平均温度,外表面平均温度应先假定后复核,第一次假定时可取比环境温度高10。上例中,ta取-3,则tm=(407.5+7)/2=207.25,=0.0534+0.000114207.25=0.077W/mK。114 计算隔热层厚度根据圆筒壁的导热方程可知,管线经过隔热材料的热流量为t0-ta)/(1/(2)ln(D0/Di)+1/(D0s)这一热流量应不大于1.2节中计算的允许单位散热损失q,因此可得如下方程:收稿日期:2002-10-09。修回日期:2004-01-08。作者简介:张礼贵,男,高级工程师。1990年毕业于上海同济大学供热通风专业,现从事热工设计工作。设计技术石油化工设计PetrochemicalDesign2004,21(1)3034Kq=(t0-ta)/(1/(2)ln(D0/Di)+1/(D0s)式中,K 修正系数,一般取0.80.9(热损失控制较严的管道取下限值);t0 管道外表面壁温,可近似取介质平均温度/;ta 环境温度/;D0 绝热层外径/m;Di 管道外径(绝热层内径)/m;s 绝热层外表面向周围环境的放热系数/W(m)-1。对于防烫伤、防结露及冷损失的厚度计算时可取8.414,其他取 s=1.163(10+6W1/2),W为风速/ms-1。解以上方程(手工解此方程需借助相应图表),便可求得D0,从而求出 =(D0-Di)/2。上例中,解得=0.14m。2 根据表面温度确定绝热层厚度本方法按给定的绝热层外表面温度ts计算绝热层厚度。主要用于防烫伤、防结露或某些有特殊要求需给定隔热层表面温度的隔热层厚度计算。根据热平衡机理,管线单层保温时有:(t0-ts)/(1/(2)ln(D0/Di)=(ts-ta)/1/(D0s)解此方程,便可求得D0,从而求出。3 根据经济性确定绝热层厚度管线绝热工程的投资和效益有着密切的关系。一般来说,当管线外径大于临界绝缘直径dc时(dc=2/s),随着绝热层厚度的增加,散热损失逐步减少4,但投资会加大。设隔热材料投资的年分摊费用为p,隔热后的年散热损失费用为fn,两者之和为年总费用c。如图1所示,p值随着保温层厚度的增加而增大(曲线A),fn值则随的增加而减少(曲线B),总费用c(曲线C)则在保温层厚度为0时具有最小值cmin,这个0值即为保温层的经济厚度2。图1 投资与保温层厚度的关系 根据热平衡及热能价格、绝热结构价格等参数可推得下列等式:D0ln(D0/Di)=0.003795 PEt|t0-ta|/(PTS)1/2-2/s式中,PE 能量价格/元(106kJ)-1;PT 绝热结构单位造价/元m-3;t 年运行时数/h;S 绝热工程投资年摊销率,%;其余符号同前。解此方程,便可求得D0,从而求出。4 其他确定绝热层厚度的方法4.1 按最大允许热损失计算绝热层厚度隔热管线的最大允许热损失Q(W/m2)在国家标准 设备及管道保温技术通则 有明确规定,其值随管道外表面的温度而变化,Q值的范围为58375W/m2(对应管线外表面温度为50850)。若按Q计算,应按下列等式计算:Q=(t0-ta)/D0/(2)ln(D0/Di)+1/s)4.2 多层保温(冷)时绝热层厚度的确定以上公式给出的是单层绝热层厚度计算式,对于多层绝热,若绝热材质相同,则仍然可用单层公式计算;若绝热材质不同,则绝热材料热阻应为(1/(2)ln(D0/Di),即每一绝热层热阻之和,然后再代入前述公式进行计算。这里D0应理解为选定绝热材料的外径,Di为该绝热层的内径。4.3 绝热层厚度选用原则由于确定绝热层厚度的计算方法不同,计算出的绝热层厚度也不同(有时差别很大)。具体选用时首先要考虑满足工艺要求。若无特殊要求,13第21卷张礼贵 1 管线绝热层厚度计算方法集粹可按经济厚度选取;若投资受限制,可按最大允许热损失方法计算。若热量无需回收,可按ts为60防烫伤温度计算。5 绝热层厚度的计算机算法不同的管线绝热层厚度的计算方程最终可化简为x(lnx+A)=B(A、B为常数)的形式。笔者在多年设计计算的实践中,根据积累的经验,用PASCAL程序设计语言5编制了“管线绝热层厚度计算程序”,解决了精确求解问题。现把常用管线绝热层厚度计算结果列于表1表4,供同行选用时参考(计算程序附后)。表1 按经济厚度计算公称直径450 蒸汽250 蒸汽90 热水7 冷水DN501201056040DN1001401207045DN2001651408050DN3001801508555备注PE取40、PT取2000、t取8000、S取30%、ta取-3PE取35、PT取1000、t取8000、S取30%、ta取-3PE取30、PT取1000、t取8000、S取30%、ta取-3PE取160、PT取1500、t取3000、S取30%、ta取-3表2 按最大允许热损失计算公称直径450 蒸汽250 蒸汽90 热水7 冷水DN50805030DN100905530DN2001006032DN3001106535备注Q取244Q取163Q取93表3 按表面温度计算公称直径450 蒸汽250 蒸汽90 热水7 冷水DN503012520DN1003413520DN2003713520DN3003814520备注ts取60ts取60ts取60ts取30表4 按允许温降计算公称直径450 蒸汽250 蒸汽90 热水7 冷水DN5080(G取2、t取0.15/m)80(G取0.8、t取0.15/m)45(G取10、t取0.2/100m)45(G取10、t取0.1/100m)DN10080(G取9、t取0.05/m)80(G取4、t取0.05/m)45(G取40、t取0.08/100m)45(G取40、t取0.04/100m)DN20090(G取35、t取0.02/m)85(G取14、t取0.02/m)45(G取170、t取0.04/100m)45(G取170、t取0.02/100m)DN300100(G取85、t取0.01/m)95(G取35、t取0.01/m)50(G取380、t取0.02/100m)50(G取380、t取0.01/100m)备注6 管线绝热层厚度计算程序program thethickness;constpi=3.1415926;varas,cp,l,t1,dw,di,d0,w,g,q,dt,lm,lmo,lm1,tm,ta,qq,bb,dd,pf,qf,nb,gu,k:real;varq1,a2,ts,t0,tmo,gd,gd1,gd2,gd3,gum,gun,pe,t,pt,s,c1,c2,e,pc,bb1,ph;real;beginwriteln(t1=);read(t1);writeln(ta=);read(ta);writeln(dw=);read(dw)writeln(bb);read(bb);writeln(bb1);read(bb1);writeln(1=);read(1);writeln(g);read(g);writeln(dt);read(dt);writeln(k);read(k);writeln(w);read(w);writeln(ts);read(ts);writeln(q);read(q);23石 油 化 工 设 计第21卷writeln(qq);read(qq);if t1 tathen as:=8.414else as:=1.1633(10+63sqrt(w);t0:=(t1+t1-dt)/2;if bb=1then beginif t0 100)and(t0 200)and(t0 300)and(t0 400)and(t0 500)and(t0 600)then cp:=2.1319+(2.2014-2.1319)3(t0-500)30.01else beginwriteln(cp);read(cp);end;end;if bb=2then cp:=4.2;if bb=3then beginwriteln(cp);read(cp);end;tm:=(t0+ta+10)/2;if bb1=1then lm:=0.043+0.00173(tm-70)else if bb1=2then 1m:=0.0534+0.0001143tmelse if bb1=3then 1m:=0.041+0.0000933(tm-20)else beginwriteln(lmo);read(lmo);writeln(lm1);read(lm1);writeln(tmo);read(tmo);1m:=1m0+1m13(tm-tmo);end;if(dt 0)or(q 0)then beginif dt 0then q:=cp310003g3dt/(3.63l);di:=dw;gum:=dw+dw320;gun:=dw;repeatdd:=(gum+gun)/2;d0:=dd;gd1:=(t0-ta)/k/(1/(23pi3lm)3ln(d0/di)+1/(pi3d030.0013as);if(gd1 q)and(t1 ta)then gun:=dd;if(gd1 ta)then gum:=dd;if(gd1 q)and(t1 q)and(t1 ta)then gum:=dd;until(abs(gd1-q)0.01)or(gum-gun)0.001);dd:=(gum-dw)/2;writeln(q=,q);end;if ts 0then begindi:=dw;gum:=dw+203dw;gun:=dw;repeatdd:=(gum+gun)/2;d0:=dd;gd1:=(as3d030.001)/(231m)3ln(d0/di);gd2:=(t0+gd13ta)/(1+gd1);if(gd2 ts)and(t1 ta);then gun;=dd;if(gd2 ta);then gum;=dd;33第21卷张礼贵 1 管线绝热层厚度计算方法集粹if(gd2 ta);then gun;=dd;if(gd2 ts)and(t1 ta);until(abs(gd2-ts)0.01)or(abs(gum-gun)0.001);dd:=(gum-dw)/2;end;if gg 0then beginif qq=1tnen qq:=58+(t0-500)30.39;di:=dw;gum;=dw+203dwgun;=dw;repeatdd:=(gum+gun)/2;d0:=dd;gd1:=(t0-ta)/(d030.001/(231m)3ln(d0/di)+1/as);if(gd1 qq)and(t1 ta)then gun:=dd;if(gd1 ta)then gum:=dd;if(gd1 qq)and(t1 ta)then gum:=dd;if(gd1 qq)and(t1 ta)then gun:=dd;until(abs(gd1-qq)0.01)or(abs(gum-gun)guthen gum:=dd;if gd1 guthen gun:=dd;until(abs(gd1-gu)0.0000001)or(abs(gum-gun)0.0001);dd:=(gum-dw)/2;writeln(dd=,dd,gu=,gu,gd1=,gd1,gum=,gum,gun=,gun,lm=,lm,d0=,d0)writeln(di=,di,pe=,pe,t=,t,t0=,t0,ta=,ta,pt=,pt,s=,s,as=,as);end;q:=(t0-ta)/(1/(23Pi3lm)3ln(d0/di)+1/(as3pi3d030.001);qq:=q/pi/(d030.001);ts:=qq/as+ta;if(cp 0)and(g 0)then dt:=q33.63l/(cp310003g);writeln(t1=,t1,ta=,ta,dw=,dw,bb=,bb,bb1=,bb1,q=,q);writeln(1=,1,g=,g,dt=,dt,w=,w,ts=,ts,qq=,qq,1m=,1m);writeln(cp=,cp,pt=,pt,s=,s,pe=,pe,t=,t);writeln(dd=,dd,mm);writeln(ts=,ts,.C);writeln(qq=,qq,W/m2);writeln(q=,q,.W/m);writeln(dt=,dt,.C);writeln(1m=,1m,W/m.C);end.参考文献1 工业设备及管道绝热工程设计规范(G B5026497).北京:中国计划出版社,1997:9272 张德姜,王怀义,刘绍叶主编.石油化工装置工艺管道安装设计手册.北京:中国石化出版社,1992:8619263 路延魁主编.空气调节设计手册.北京:中国建筑工业出版社,1995:1731764 章熙民等编.传热学.北京:中国建筑工业出版社,1987:21485郑启华编著.PASCAL程序设计.北京:清华大学出版社,1995:158743石 油 化 工 设 计第21卷Matrix project management model of EPC contractorZhang Xiudong,etc.,SINOPEC Engineering Incorporation,P.C.100101Abstract:Combining with the characteristics of EPC project,some ideals about project management are shown suchas matrix organization structure,main function of engineering,contract management,material control.Keywords:EPCMatrix organization structureEngineeringIntroduction of project management of engineering companies from U.S.A and CanadaWang Ning,etc.,Ministry of construction P.R.C.,P.C.100835Abstract:The basic condition of engineering companiesfrom U.S.A and Canada in project management is introducedin the paper,providing some ideals for domestic engineering companies.Keywords:Engineering companyProject managementIntroductionNecessity of general design in Sino-foreign joint venture large-sized petrochemical plantZhu Xianjie,SINOPEC Engineering Incorporation,P.C.100101Abstract:The paper introduces the main function and necessity of general design in Sino-foreign joint venture large-sized petrochemical plant.Keywords:Sino-foreign joint ventureLarge-sized petrochemical plantGeneral designApplication model of cost control in project managementYu Xiaohua,SINOPEC Engineering Incorporation,P.C.100101Abstract:Combined with the specific cost control practice of EPCproject of Y ARACO,the paper studies the charac2teristics of EPC contract and application model of cost control in project management to find a reasonable and practicalcost control program to satisfy the interests of the client and the contractor during contract execution.Keywords:Cost controlEPC projectPracticeDifference between of basic engineering design and preliminary designXiao Xuejun,SINOPEC Engineering Incorporation,P.C.100101Abstract:The paper introduces the basic requirements of basic engineering design and difference between of it andpreliminary design.Keywords:DifferenceBasic engineering designPreliminary designProcess technology of 200kt/a polypropylene plant in ShanghaiLiu Jian,SINOPEC Engineering Incorporation,P.C.100101Abstract:The general project information,main technology scheme,operating information of the 200kt/a polypropy2lene plant in Shanghai Petrochemical Company Ltd.are introduced in this article.Keywords:PolypropyleneEngineeringCopolymerProduction and supply-demand of propyleneSun Kehua,Beijing Research Institute of Chemical Industry,SINOPEC,P.C.100013Abstract:The trend of increasing propylene yield is expected to come from steam crackers to from refineries.The de2velopment of demand of polypropylene,acrylic nitrile and propylene oxide for propylene is analyzed.The supply ofpropylene worldwide will not be shortfall in future.Keywords:PropyleneCrackersRefineriesDemandPolypropyleneAcrylic nitrilePropylene oxideCalculation methods of thermal insulation layer thicknessZhang Ligui,Jinling Petrochemical Design Institute,P.C.210033Abstract:Several basic calculation methods of thermal insulation layer thickness are introduced in the paper,relatedconditions are presented as well.The author have compiled calculation program by using PASCAL program andshowed results in tables.Keywords:PipelineThickness of thermal insulation layerAllowable temperature dropABSTRACTS