流量為130t-h立式蒸汽冷凝器的設(shè)計(jì)【過(guò)程裝備與控制工程類】【說(shuō)明書(shū)+CAD】
流量為130t-h立式蒸汽冷凝器的設(shè)計(jì)【過(guò)程裝備與控制工程類】【說(shuō)明書(shū)+CAD】,過(guò)程裝備與控制工程類,說(shuō)明書(shū)+CAD,流量為130t-h立式蒸汽冷凝器的設(shè)計(jì)【過(guò)程裝備與控制工程類】【說(shuō)明書(shū)+CAD】,流量,立式,蒸汽,冷凝器,設(shè)計(jì),過(guò)程,進(jìn)程,裝備,設(shè)備,控制工程,說(shuō)明書(shū),仿單,cad
沈陽(yáng)化工大學(xué)科亞學(xué)院本科畢業(yè)論文 題 目： 流量為130t/h立式蒸汽冷凝器 專 業(yè)： 過(guò)程裝備與控制工程 班 級(jí)： 1201班 學(xué)生姓名： 王 晗 指導(dǎo)教師： 金 丹 論文提交日期：2016年05月27日 論文答辯日期：2016年06月06日畢業(yè)設(shè)計(jì)（論文）任務(wù)書(shū)過(guò)程裝備與控制工程專業(yè)1201班學(xué)生：王 晗畢業(yè)設(shè)計(jì)（論文）題目：流量為130t/h立式蒸汽冷凝器 畢業(yè)設(shè)計(jì)（論文）內(nèi)容： 1.關(guān)于換熱器綜述一篇； 2.計(jì)算書(shū)說(shuō)明書(shū)一份； 3.繪制工程圖折合A1號(hào)圖四張以上； 畢業(yè)設(shè)計(jì)（論文）專題部分： 固定管板式換熱器 起止時(shí)間： 年 月 年 月 日指導(dǎo)教師： 簽字 年 月 日摘要 冷凝器它是使用范圍很廣的一種化工設(shè)備，屬于換熱器一種。本設(shè)計(jì)任務(wù)主要是根據(jù)已知條件選擇采用固定管板式換熱器的設(shè)計(jì),固定管板式換熱器的優(yōu)點(diǎn)是鍛件使用少，造價(jià)低；傳熱面積比浮頭式換熱器大20%到30且旁路滲流小。 本臺(tái)換熱器主要完成的是水蒸氣-水之間的熱量交換,首先根據(jù)給出的設(shè)計(jì)溫度和設(shè)計(jì)壓力來(lái)確定設(shè)備的結(jié)構(gòu)形式以及殼程和管程的材料，然后根據(jù)物料性質(zhì)和傳熱面積來(lái)確定換熱管的材料，尺寸，根數(shù)。，設(shè)計(jì)壓力為管程2.31MPa，殼程0.935MPa，工作溫度管程50，殼程130，設(shè)計(jì)溫度管程80，殼程140，傳熱面積為256m2，采用252.53000的無(wú)縫鋼管換熱，則可計(jì)算出622根換熱管，D=1200mm的圓筒根據(jù)換熱管的根數(shù)確定換熱管的排列，并根據(jù)換熱管的排列和長(zhǎng)度來(lái)確定筒體直徑以及折流板的選擇。通過(guò)對(duì)容器的內(nèi)徑和內(nèi)外壓的計(jì)算來(lái)確定殼體和封頭的厚度并進(jìn)行強(qiáng)度校核。然后是對(duì)換熱器各部件的零部件的強(qiáng)度設(shè)計(jì)，有法蘭的選擇和設(shè)計(jì)計(jì)算與校核，鉤圈及浮頭法蘭的設(shè)計(jì)計(jì)算與校核和管子拉脫力的計(jì)算。還包括管板的結(jié)構(gòu)設(shè)計(jì)、防沖擋板、滑道結(jié)構(gòu)的設(shè)計(jì)以及支座設(shè)計(jì)。結(jié)構(gòu)設(shè)計(jì)中的標(biāo)準(zhǔn)件可以參照國(guó)家標(biāo)準(zhǔn)根據(jù)設(shè)計(jì)條件直接選??；非標(biāo)準(zhǔn)件，設(shè)計(jì)完結(jié)構(gòu)后必須進(jìn)行相應(yīng)的應(yīng)力校核。 管板與換熱管的連接方式為焊接，因管板上的應(yīng)力較多，且內(nèi)外溫度有一定的差值，因此，對(duì)管板強(qiáng)度的校核是一個(gè)重點(diǎn)，也是一個(gè)難點(diǎn). 關(guān)鍵詞： 換熱器； 強(qiáng)度設(shè)計(jì)； 結(jié)構(gòu)設(shè)計(jì)Abstract The condenser is a kind of chemical equipment which is widely used, and belongs to a kind of heat exchanger. The design task is mainly according to the known conditions to choose the design of fixed tube plate heat exchanger, the advantages of fixed tube plate heat exchanger is forging used less, low cost; heat transfer area ratio of floating head type for heat exchanger is 20% to 30% and a bypass flow small.The heat exchanger is mainly completed is between water vapor and water heat exchange, first of all according to the given design temperature and pressure to determine structure of equipment and the shell side and tube side material, and then according to the nature of the material and the heat transfer area to determine the heat exchange tube materials, dimensions, number of roots. And design pressure for tube side 2.31MPa, shell 0.935MPa, the working temperature of the tube process 50 DEG C, 130 DEG C shell, design temperature tube process at a temperature of 80 DEG C, shell and 140 DEG C, heat transfer area for 256m2. The phi 25 x 2.5 x 3000 seamless steel pipe heat exchanger can be calculated 622 heat exchange tube, D=1200mm cylindrical root according to determine the root number of heat exchange tube heat exchanger tube arrangement and according to the arrangement and length of heat exchange tube to determine cylinder diameter and baffle the choice. Determine the thickness of the shell and the head and carry out the intensity verification by calculating the inner diameter and the internal pressure of the container. Then the strength design of components of the various components of the heat exchanger, flange design, selection and calculation and checking, hook and loop and floating head flange design calculation and checking of the pipe and pull off force calculation. Also includes a tube plate structure design, anti scour baffle, slideway structure design and the design of support. The standard parts in the structure design can be selected directly according to the national standards; the non standard parts must be checked for the corresponding stress after the design of the structure.Tube plate and tube heat exchanger and the connection mode of welding, tube plate more stress, and the temperature inside and outside have certain difference. Therefore, on the tube sheet strength check is a key and a difficulties.Keywords: heat exchanger； strength design； structure design目 錄第一章傳統(tǒng)工藝計(jì)算11.1工藝計(jì)算11.1.1介質(zhì)原始數(shù)據(jù)11.1.2介質(zhì)定性溫度及物性參數(shù)11.2 傳熱量與水蒸汽流量計(jì)算21.3 有效平均溫差計(jì)算31.4管程換熱系數(shù)計(jì)算41.5 管程結(jié)構(gòu)初步設(shè)計(jì)51.6殼程換熱系數(shù)計(jì)算51.7總傳熱系數(shù)計(jì)算61.8管壁溫度計(jì)算71.9管程壓力降計(jì)算81.10殼程壓力降計(jì)算8第二章強(qiáng)度計(jì)算112.1結(jié)構(gòu)設(shè)計(jì)說(shuō)明書(shū)112.1.1換熱管材料及規(guī)格的選擇和根數(shù)的確定112.1.2布管方式的選擇112.1.3筒體內(nèi)徑的確定112.1.4筒體壁厚的確定122.1.5封頭形式的確定122.1.6管箱短節(jié)壁厚計(jì)算132.1.7容器法蘭的選擇132.1.8管板尺寸的確定及強(qiáng)度計(jì)算142.1.9是否安裝膨脹節(jié)的判定：262.1.10各管孔接管及其法蘭的選擇：262.1.11設(shè)備法蘭的選擇302.1.12拉桿和定距管的確定312.1.13開(kāi)孔補(bǔ)強(qiáng)計(jì)算：322.2筒體管箱耐壓試驗(yàn)的應(yīng)力校核計(jì)算342.2.1筒體核算342.2.2、支座的選擇及應(yīng)力校核352.2.3 耳座的應(yīng)力校核36參考文獻(xiàn)39致 謝40 沈陽(yáng)化工大學(xué)科亞學(xué)院學(xué)士學(xué)位論文 第一章 傳統(tǒng)工藝計(jì)算第一章傳統(tǒng)工藝計(jì)算1.1工藝計(jì)算1.1.1介質(zhì)原始數(shù)據(jù)管程水的進(jìn)口溫度t1=20管程水的出口溫度t1=90管程水的工作壓力管程水的流量G1=290t/h=290000kg/h殼程水蒸氣的入口溫度t2=170.7殼程水蒸氣的出口溫度t2=85殼程水蒸氣的入口壓力P2=0.85MPa1.1.2介質(zhì)定性溫度及物性參數(shù)管程：管程水定性溫度 =（+ ）/2=（20+90）/2=55管程水密度查物性表得=985.75 /m3管程水比熱查物性表得Cp1=4.176KJ/（KgK）管程水導(dǎo)熱系數(shù)查物性表得1=0.648W/（m）管程水粘度1=5.06410-4 Pas管程水普朗特?cái)?shù)查物性表得 殼程：殼程水蒸汽定性溫度：殼程水蒸汽冷凝點(diǎn) : ti = t2=170.7冷卻段： =（ti + t2）/2=（170.7+85）/2=127.85冷凝段：= （t2+ ti）=（170.7+170.7）/2=170.7殼程水蒸汽密度查物性表得：冷卻段：2=937.8/m3 冷凝段: 2=4.194/ m3殼程水蒸汽比熱查物性表得:冷卻段：Cp2=4.319 KJ/（KgK）冷凝段：p2=2.589 KJ/（KgK）r殼程水蒸汽導(dǎo)熱系數(shù)查物性表得：冷卻段：2 =0.6878 W/（mK）冷凝段：2= 0.03218 W/（mK） 殼程水蒸汽粘度：冷卻段：2 =217.19110-6 Pas冷凝段：2=14.61910-6 Pas殼程水蒸汽普朗特?cái)?shù)查物性表得：冷卻段：Pr2 =1.344冷凝段：r2=1.1341.2 傳熱量與水蒸汽流量計(jì)算取定換熱效率 =0.98則設(shè)計(jì)傳熱量 := G1Cp1(t1- t1)1000/3600=2900004.176(90-20)1000/3600=23.55106W由=r+ Cp2(t2- t2) 導(dǎo)出水蒸氣流量G2，r為t2時(shí)的汽化潛熱，r=2047.1KJ/Kg水蒸汽流量:G2= Q0/ /r+ Cp2(ti - t2) =23.55106/0.98/2047.11000+4.3191000(170.7-85)=6.703Kg/s冷卻段傳熱量：Q2=G2Cp2(ti- t2)=6.7034.319103(170.7-85)=2481037W冷凝段傳熱量:2= G2r=6.7032047.11000=13721711.3W設(shè)冷凝段和冷卻段分界處的溫度為根據(jù)熱量衡算 : = =2/ G1/ Cp1+ t1=13721711.30.983600/290000/4176+20=59.9741.3 有效平均溫差計(jì)算逆流冷卻段平均溫差:tn=85.843逆流冷凝段平均溫差:tn=94.923冷卻段:參數(shù):P=0.271參數(shù):R=2.854換熱器按單殼程 單管程設(shè)計(jì)則查圖 2-6(a)，得:溫差校正系數(shù) =1.0f -有效平均溫差: tm= tn=1.085.843=85.843- - -冷凝段：參數(shù):P=0.265參數(shù):R=0換熱器按單殼程 單管程設(shè)計(jì)則查圖 2-6(a)，得:溫差校正系數(shù) =1.0有效平均溫差: tm= tn=1.094.923=94.9231.4管程換熱系數(shù)計(jì)算初選冷卻段傳熱系數(shù):K0= 820 w/(mk)初選冷凝段傳熱系數(shù): K0= 1300 w/(mk)則初選冷卻段傳熱面積為:F0=Q2/( K0tm)= 24810370.98/(82085.843)=46.7688m2初選冷凝段傳熱面積為: F0=2/( K0tm)= 13721711.30.98/(130094.923)=108.973 m2選用252.5的無(wú)縫鋼管做換熱管則: 管子外徑d0=25 mm 管子內(nèi)徑di=20 mm 管子長(zhǎng)度 L=3000 mm則需要換熱管根數(shù):Nt=( F0+ F0)/( d0L)=(46.7688+108.973)/(3.140.0253)=661.3可取換熱管根數(shù)為 662根管程流通面積:a1=2= =0.207868管程流速: W1 = 290000/( 3600985.750.207868 )= 0.093m/s管程雷諾數(shù):Re1=1w1di/1=985.750.3930.02/(5.06410-4)= 15300.148則管程冷卻段的定性溫度:t11=(t3+ t1)/2=(59.97+90)/2=74.987管程冷卻段傳熱系數(shù):a1=3605(1+0.015 t11) W10.8/(100di)0.2=8077.656管程冷凝段的定性溫度: t12=(t3+t1)/2=(59.974+20)/2=39.987管程冷凝段傳熱系數(shù): a1=3605(1+0.015 t12) W10.8/(100di)0.2= 4101.3751.5 管程結(jié)構(gòu)初步設(shè)計(jì)查 GB1511999知管間距按, 取管間距為：管束中心排管數(shù)為：Nc=1.1=28.3，取30根則殼體內(nèi)徑:Di=s（Nc-1）+4 d0=1.028圓整為: 則長(zhǎng)徑比:=2.5 合理折流板選擇弓形折流板:弓形折流板的弓高:折流板間距:B=400取B=400折流板數(shù)量:Nb=-1=-1=6.5 取7塊1.6殼程換熱系數(shù)計(jì)算殼程流通面積:=0.41.2（1-0.025/0.032）=殼程流速:冷卻段:w2=6.703/（937.580.105）=0.068m/s冷凝段:2=6.703/（4.1940.105）=15.22m/s殼程當(dāng)量直徑:de=（Di2-Ntd02）/（Ntd0）=（-711）/（7110.025）=0.056m 冷凝段管外壁溫度假定值: 膜溫:tm=（w+ t2）/2=（109.6+170.7）/2=140.15膜溫下液膜的粘度:m=19510-6Pas膜溫下液膜的密度:m=926.4Kg/m3膜溫下液膜的導(dǎo)熱系數(shù)為:m=0.6842/（m）正三角形排列ns=2.080 Nt 0.495=2.080662 0.495=51.807冷凝負(fù)荷：=6.703/（351.807）=0.0431殼程冷凝段雷諾數(shù):=4/um=40.0431/19510-6=884.1殼程冷凝段傳熱系數(shù):a2=1.51（m3mg/m2）（）=9635.7 冷卻段管外壁溫假定值:冷卻段雷諾數(shù)：Re=937.80.0680.056/217.19110-6=16442.405壁溫下水粘度:w2=298.610-6 Pas粘度修正系數(shù):1=（）0.14=0.956殼程傳熱因子查圖 2-12 得: 冷卻段殼程換熱系數(shù):a2=（2/de）Pr2 1 js=（0.6878/0.056）1.3440.956100=1875.291.7總傳熱系數(shù)計(jì)算查 GB-1999 第 138 頁(yè)可知水蒸汽的側(cè)污垢熱阻:r2=8.810-5（m2/w）管程水選用地下水，污垢熱阻為: 由于管壁比較薄，所以管壁的熱阻可以忽略不計(jì)冷卻段總傳熱系數(shù):Kj=1/1/a2+r2+r1d0/di+d0/（a1di）= 731.176傳熱面積比為: Kj/ K0=1.08(合理)冷凝段總傳熱系數(shù):Kj=1/1/ a2+r2+r1d0/di+d0/（a1di）=1385.0607傳熱面積比為: Kj/ K0=1.06（合理）1.8管壁溫度計(jì)算設(shè)定冷凝段的長(zhǎng)度:冷卻段的長(zhǎng)度:冷卻段管外壁熱流密度計(jì)算:q2=Q2/(Ntd0 L)=48859.33w/（m2）冷卻段管外壁溫度:tw=t2-q2(1/a2+r2)=97.496誤差校核:e=tw2- tw=95-97.496=-2.496 誤差不大冷凝段管外壁熱流密度計(jì)算:q2=2/( Ntd0 L)=（13721711.30.98）/155473.7 w/（6623.140.0252.0424）=126696.88（m2）冷凝段管外壁溫度:tw=tm- q2(1/ a2+r2)=115.62誤差校核:= - tw=-6.02 誤差不大1.9管程壓力降計(jì)算管程水的流速:u1=290000/（3600985.750.207868）=0.393m/s管程雷諾準(zhǔn)數(shù):Re1=1w1di/1=985.750.3930.02/（5.064）=15300.148程摩擦系數(shù):=0.3164/(Re10.25)=0.02845壓降結(jié)垢校正系數(shù):沿程壓降:P1=112L di/(2di)=（0.02845985.75）/（2）=454.8Pa 取管程出入口接管內(nèi)徑:d1=250mm管程出入口流速:u1=4G/(3600d121)=（4290000）/（3600）=1.67m/s局部壓降: P3=1 u12(1+0.5)/2=（985.751.5）/2=2061.99 Pa管程總壓降: P=P1P3=454.8 2061.9=2516.7Pa管程允許壓降: P P 即壓降符合要求。1.10殼程壓力降計(jì)算殼程當(dāng)量直徑:De=（Di2-Ntd02）/（Di+Ntd0）=(1.2-662)/(1.2)=0.0443m殼程流通面積:殼程流速:冷卻段:w2=G2/（2f2）=0.068m/s冷凝段:2=2/（2f2）=15.22m/s殼程雷諾數(shù):殼程冷卻段雷諾數(shù):Re=2w2de/2=16442.4殼程冷凝段雷諾數(shù): =4/um=884.1查表殼程摩擦系數(shù): 冷卻段:冷凝段: 2=0.54殼程粘度修正系數(shù):冷卻段d1=1.0冷凝段d2=1.0管束周邊壓降:冷卻段管束周邊壓降:Pa=(2w22/2) Di(nb+1)/De(1/d1)=164.45Pa冷凝段管束周邊壓降:a=(2/2)Di(nb+1)/De(2/d2)=56844.57Pa導(dǎo)流板壓降: Pb= 0, （無(wú)導(dǎo)流板）查表取殼程壓降結(jié)垢系數(shù):冷卻段d0=1.21 冷凝段d0=1.11取殼程進(jìn)口接管內(nèi)徑:殼程出口接管內(nèi)徑:d2=100mm殼程出口流速:u2=4G2/(2d22)=0.90m/s殼程進(jìn)口流速:u2=4G2/(d22)=32.6m/s局部壓降:冷卻段Pc=2 u22(1+0.5)/2=569.7Pa冷凝段c=u22(1+0.5)/2=3342.9Pa殼程總壓降:冷卻段殼程總壓降: P=Pad0+Pb+Pc=768.7Pa冷凝段殼程總壓降: =ad0+b+c=66440.4Pa殼程允許壓降: P P 即壓降符合要求; P 即壓降符合要求. 10沈陽(yáng)化工大學(xué)科亞學(xué)院學(xué)士學(xué)位論文 第二章 強(qiáng)度計(jì)算第二章強(qiáng)度計(jì)算2.1結(jié)構(gòu)設(shè)計(jì)說(shuō)明書(shū)2.1.1換熱管材料及規(guī)格的選擇和根數(shù)的確定序號(hào)項(xiàng)目符號(hào)單位數(shù)據(jù)來(lái)源及計(jì)算公式數(shù)值1換熱管材料16Mn2換熱管規(guī)格252.530003傳熱面積Am2A=Q/Ktm155.94換熱管根數(shù)N根N=A/3.14dL6222.1.2布管方式的選擇序號(hào)項(xiàng)目符號(hào)單位數(shù)據(jù)來(lái)源和數(shù)據(jù)計(jì)算數(shù)值1轉(zhuǎn)角正三角形GB151-1999圖112換熱管中心距SmmGB151-1999表12323隔板槽兩側(cè)相鄰管中心距SnmmGB151-1999表12442.1.3筒體內(nèi)徑的確定序號(hào)項(xiàng)目符號(hào)單位數(shù)據(jù)來(lái)源和計(jì)算公式數(shù)值1換熱管中心距SmmGB151-1999表12322換熱管根數(shù)Nt根Nt=A/3.14dL6623管束中心排管根數(shù)Nc根Nc=1.1304換熱管外徑d0mm255到殼體內(nèi)壁最短距離6布管限定圓直徑mm1187.57筒體內(nèi)徑10288實(shí)取筒體公稱直徑12002.1.4筒體壁厚的確定序號(hào)項(xiàng)目符號(hào)單位數(shù)據(jù)來(lái)源和計(jì)算公式數(shù)值1計(jì)算壓力PcMPaPc=1.1P0.9352筒體內(nèi)徑dimm見(jiàn)三-812003筒體材料Q235-B4設(shè)計(jì)溫度下筒體材料的許用應(yīng)力1055焊接接頭系數(shù)0.856筒體設(shè)計(jì)厚度6.317腐蝕裕量C2mm18負(fù)偏差C1mm09設(shè)計(jì)厚度mmd=+ C27.3110名義厚度項(xiàng)目5.3.2102.1.5封頭形式的確定序號(hào)項(xiàng)目符號(hào)單位數(shù)據(jù)來(lái)源和計(jì)算公式數(shù)值1封頭內(nèi)徑Dimm12002計(jì)算壓力PcMPaPc=1.1P0.9353焊接接頭系數(shù)0.854設(shè)計(jì)溫度下許用壓力項(xiàng)目5.3.21055標(biāo)準(zhǔn)橢圓封頭計(jì)算厚度mm=PcDi/（2t-0.5Pc）5.356腐蝕裕量C2mm17負(fù)偏差C1mm08設(shè)計(jì)厚度dmmd=+C26.359名義厚度項(xiàng)目5.3.21010直邊高度hmmJB/T4737-95252.1.6管箱短節(jié)壁厚計(jì)算序號(hào)項(xiàng)目符號(hào)單位數(shù)據(jù)來(lái)源和計(jì)算公式數(shù)值1計(jì)算壓力PcMPaPc=1.1P2.312管箱內(nèi)徑dimm12003管箱材料16Mn4設(shè)計(jì)溫度下許用應(yīng)力1705管箱計(jì)算厚度9.76焊接接頭系數(shù)mm0.857腐蝕裕量C2mm18負(fù)偏差C1mm09設(shè)計(jì)厚度dmmd=+ C210.710名義厚度nGB151項(xiàng)目5.3.2122.1.7容器法蘭的選擇序號(hào)項(xiàng)目符號(hào)單位數(shù)據(jù)來(lái)源和計(jì)算公式數(shù)值1法蘭類型乙型平焊法蘭JB/T4702-2000PN=2.5MPa2法蘭外徑d0JB/T4702-200013953螺栓中心圓直徑JB/T4703-200013404法蘭公稱直徑JB/T4703-200012005法蘭材料16MnR6墊片類型JB/T4703-2000非金屬軟墊片7墊片材料GB/T3985-19958墊片公稱直徑JB/T4704-200012009墊片外徑JB/T4704-2000127710墊片內(nèi)徑JB/T4704-2000122711法蘭厚度JB/T4704-20008412墊片厚度1JB/T4704-2000313螺栓規(guī)格及數(shù)量248M272.1.8管板尺寸的確定及強(qiáng)度計(jì)算本設(shè)計(jì)為管板延長(zhǎng)部分兼作法蘭的形式，即項(xiàng)目5.7中，圖18所示e型連接方式的管板。A、確定殼程圓筒、管箱圓筒、管箱法蘭、換熱管等元件結(jié)構(gòu)尺寸及管板的布管方式；以上項(xiàng)目的確定見(jiàn)項(xiàng)目一至七。B、計(jì)算A、As、na、Kt、cr、Ac、Dt、Q、s、t、Pt；序號(hào)項(xiàng)目符號(hào)單位數(shù)據(jù)來(lái)源和計(jì)算公式數(shù)值備注1筒體內(nèi)徑di12002筒體內(nèi)徑橫截面積11304003筒體厚度s144圓筒內(nèi)殼壁金屬截面積53367.445管子金屬總截面積mm211.696換熱管根數(shù)n6627換熱管外徑dmm258換熱管壁厚tmm2.59換熱管材料的彈性模量表F519600010換熱管有效長(zhǎng)度Lmm295011沿一側(cè)的排管數(shù)n 2112布管區(qū)內(nèi)未能被管支撐的面積1459413管板布管區(qū)面積60164514管板布管區(qū)當(dāng)量直徑DtmmDt=875.515換熱管中心距Smm3216隔板槽兩側(cè)相鄰管中心距017管板布管內(nèi)開(kāi)孔后的面積A1mm2A1= At -nd2/480560618系數(shù)=A1/A0.7119殼體不帶膨脹節(jié)時(shí)換熱管束與圓筒剛度比2.5620殼程圓筒材料的彈性模量表F519000021系數(shù)=na/A10.145122系數(shù)=0.4+0.6（1+Q）/3.40823系數(shù)4.9124管板布管區(qū)當(dāng)量直徑與殼程圓筒內(nèi)徑比0.7325管子受壓失穩(wěn)當(dāng)量長(zhǎng)度mm圖3225826設(shè)計(jì)溫度下管子受屈服強(qiáng)度表F2168C、對(duì)于延長(zhǎng)部分兼作法蘭的管板，計(jì)算和序號(hào)項(xiàng)目符號(hào)單位數(shù)據(jù)來(lái)源和計(jì)算公式數(shù)值1墊片接觸寬度表9-1252墊片基本密度寬度BommBo=N/212.53墊片比壓力表9-2114墊片系數(shù)m2.05墊片有效密封寬度bmmB=2.5396墊片壓緊力作用中心圓直徑mm12097預(yù)緊狀態(tài)下需要的最小螺栓載荷N375829.748操作狀態(tài)下需要的最小螺栓載荷N29493539常溫下螺栓材料的許用應(yīng)力MPa表F425810預(yù)緊狀態(tài)下需要的最小螺栓面積mm21456.711操作狀態(tài)下需要的最小螺栓面積mm211431.612需要螺栓總截面積mm211431.613法蘭螺栓的中心圓直徑dbmm134014法蘭中心至Fc作用處的徑向距離mm65.615基本法蘭力矩Nmm1.910816筒體厚度0mm1417法蘭頸部大端有效厚度mm24.518螺栓中心至法蘭頸部與法蘭背面交的徑向距離mm45.519螺栓中心處至FT作用位置處的徑向距離mm67.7520螺栓中心距FD作用處的徑向距離mm7021作用于法蘭內(nèi)徑截面上的流體壓力引起的軸向力N105692422流體壓力引起的總軸向力與作用于法蘭內(nèi)徑截面上的流體壓力引起的軸向力差N1593615.24123操作狀態(tài)下需要的最小墊片壓力N286997.25624法蘭操作力矩Nmm1.34108D、假定管板的計(jì)算厚度為，然后按結(jié)構(gòu)要求確定殼體法蘭厚度，計(jì)算K，k、和Kf。序號(hào)項(xiàng)目符號(hào)單位數(shù)據(jù)來(lái)源和計(jì)算公式數(shù)值1布管區(qū)當(dāng)量直徑與殼程圓筒內(nèi)徑之比0.732系數(shù) (P31)表220.26143管板材料16Mn4設(shè)計(jì)溫度下管板材料許用應(yīng)力MPa（P15）1705管板剛度削弱系數(shù)GB151-19990.46殼程設(shè)計(jì)壓力PsMPa0.9357管程設(shè)計(jì)壓力PtMPa2.318管板設(shè)計(jì)壓力PdMPaMaxPt -Pt，Pt，Ps2.319管板厚度=0.82Dg 192.610換熱管加強(qiáng)系數(shù)7.811管板周邊布管區(qū)的無(wú)量綱參數(shù)kk=K（1-t）2.10612換熱管材料彈性模量MPa表F519610313管束模數(shù)KtMPaKt=Etna/（LDi）636414殼體法蘭材料彈性模量MPa表F519010315殼體圓筒材料彈性模量表F519010316殼體法蘭寬度mm97.517系數(shù)圖260.000618殼體法蘭與圓筒的選裝剛度MPa9.519旋轉(zhuǎn)剛度無(wú)量綱參數(shù)0.0012E、 由GB151-1999 P51圖27按照K和Kf查m1，并計(jì)算值，由圖29按照K和Kf查G2值序號(hào)項(xiàng)目符號(hào)單位數(shù)據(jù)來(lái)源和計(jì)算公式數(shù)值1管板第一矩系數(shù)m1GB151-1999圖270.32系數(shù)=m1/（KKf）32.53系數(shù)G2GB151-1999圖294.6F、計(jì)算M1，由圖30按照K和Q查G3，計(jì)算，M、Mf。序號(hào)項(xiàng)目符號(hào)單位數(shù)據(jù)來(lái)源和計(jì)算公式數(shù)值1管箱法蘭材料的彈性模量MPa表F51961032管箱法蘭厚度f(wàn)mmJB/T4702-2000323系數(shù)GB151-1999圖260.00064管箱圓筒與法蘭的旋轉(zhuǎn)剛度參數(shù)=10.25系數(shù)G3GB151-1999圖308.410-46系數(shù)= /（+G3）0.597管板邊緣力矩的變化系數(shù)0.6578法蘭力矩變化系數(shù)=/ Kf0.6129管板第二彎矩系數(shù)圖28（a）2.04G、按課程設(shè)計(jì)壓力，而管程設(shè)計(jì)壓力，膨脹變形差，法蘭力矩的的危險(xiǎn)組合（項(xiàng)目5.7.3.2分別討論）a、只有殼程設(shè)計(jì)壓力，而管程設(shè)計(jì)壓力，不計(jì)膨脹節(jié)變形差（即）。序號(hào)項(xiàng)目符號(hào)單位數(shù)據(jù)來(lái)源和計(jì)算公式數(shù)值備注1當(dāng)量壓力組合PcMPaPc=Ps2.312系數(shù)ss=0.4+0.6（1+Q）/0.753.0083有效壓力組合MPa28.534基本法蘭力矩系數(shù)0.00695管程壓力下的法蘭力矩系數(shù)=4Mp/0.00496法蘭力矩折減系數(shù)0.00857管板邊緣力矩系數(shù)0.01258管板邊緣剪切系數(shù)vv= 0.4069管板總彎矩系數(shù)mm=（m1+vm2）/（1+v）0.80210系數(shù)0.34111系數(shù)0.12312系數(shù)G1G1=maxGle，Gli13殼體法蘭力矩系數(shù)-0.0011314管板徑向應(yīng)力系數(shù)=0.017515管板的徑向應(yīng)力34.41.5tr16管板布管區(qū)周邊外徑向的應(yīng)力系數(shù)0.015817管板布管區(qū)周邊外徑向的應(yīng)力45.551.5tr18管板布管區(qū)周邊剪切應(yīng)力系數(shù)=（1+v）/4（Q+G2）0.065719管板布管區(qū)周邊的剪切應(yīng)力MPa Pa（/）（Dt/）15.120.5tr20法蘭的外徑與內(nèi)徑之比KK=D0/Di1.1621系數(shù)YGB150-1998表9-510.322殼體法蘭應(yīng)力MPa=/4YPa（Di/f）2443.91.5tr23換熱管的軸向應(yīng)力=Pc-Pa-91.9cr24殼程圓筒的軸向應(yīng)力=A/AsPa87.9325一根換熱管管壁金屬的橫界面積176.626換熱管與管板連接的拉托應(yīng)力MPa-0.069trb、只有殼程設(shè)計(jì)壓力，而管程設(shè)計(jì)壓力，并且計(jì)入膨脹變形差。序號(hào)項(xiàng)目符號(hào)單位數(shù)據(jù)來(lái)源和計(jì)算公式數(shù)值備注1殼程圓筒材料線膨脹系數(shù)1/11.6210-62換熱管材料線膨脹系數(shù)1/10.8810-63換熱管與殼程圓筒的膨脹變形差927.410-64沿長(zhǎng)度平均的殼程圓筒金屬溫度ts工藝給定905沿長(zhǎng)度平均的換熱管金屬溫度tt工藝給定1806制造環(huán)境溫度t0207當(dāng)量壓力組合0.9358有效壓力組合PaMPaPa=sPs-t+rEt29.19基本法蘭力矩系數(shù)=4Mm/（Di3Pa）0.006810管程壓力下的法蘭力矩系數(shù)=4Mp/（Di3Pa）0.004811管板邊緣力矩系數(shù)0.012412管板邊緣剪切系數(shù)vv= 0.40313管程總彎矩系數(shù)0.814系數(shù)15系數(shù)16系數(shù)G1G1=max，GLe0.34217殼體法蘭力矩系數(shù)=-M1-0.0011918管板徑向應(yīng)力系數(shù)=（1+v）G1/4（Q+G2）0.017519管板的徑向應(yīng)力MPar=（r）Pa（/）（Di/）235.093tr20管板布管區(qū)周邊外徑向的應(yīng)力系數(shù)=3（1+v）m/4K（Q+G2）0.015721管板布管區(qū)周邊外徑向的應(yīng)力MPa=Pa（/）（Di/）21-K/m+K2（1.414-m）/2m459.53tr22管板布管區(qū)周邊的剪切應(yīng)力系數(shù)=（1+v）/4（Q+G2）0.05123管板布管區(qū)周邊的剪切應(yīng)力MPa11.971.5tr24換熱管的軸向應(yīng)力t=Pc-Pa-91.933tr25換熱管與管板連接的拉托應(yīng)力-0.06890.5trc、只有管程設(shè)計(jì)壓力，而殼程設(shè)計(jì)壓力，不計(jì)膨脹節(jié)變形差時(shí)：序號(hào)項(xiàng)目符號(hào)單位數(shù)據(jù)來(lái)源和計(jì)算公式數(shù)值備注1當(dāng)量壓力組合PcMPaPc=Ps02有效壓力組合MPa26.373管板邊緣力矩系數(shù)0.01324管板邊緣剪切系數(shù)vv=0.4295管板總彎矩系數(shù)mm=（m1+vm2）/（1+v）0.8226系數(shù)7系數(shù)8系數(shù)G1G1= max，GLe0.2459管板的徑向應(yīng)力rMPar=（r）Pa（/）（Di/）223.251.5tr10管板布管區(qū)周邊外徑向的應(yīng)力系數(shù)0.016511管板布管區(qū)周邊外徑向的應(yīng)力MPaPa（/）1-K/m+K2（1.414-m）/2m-159.781.5tr12管板布管區(qū)周邊的剪切應(yīng)力系數(shù)0.05213管板布管區(qū)周邊的剪切應(yīng)力MPa11.060.5tr14殼體法蘭應(yīng)力fMPa-282.20.5tr15換熱管的軸向應(yīng)力tMpa=Pc-Pa-3.63cr16殼程圓筒的軸向應(yīng)力cMPa82.61cr17換熱管與管板連接的拉托應(yīng)力QMPa-0.0027tr/2d、只有管程設(shè)計(jì)壓力Pt，而殼程設(shè)計(jì)壓力Ps=0，同時(shí)計(jì)入膨脹變形差時(shí)：序號(hào)項(xiàng)目符號(hào)單位數(shù)據(jù)來(lái)源和計(jì)算公式數(shù)值備注1換熱管與殼程圓筒的膨脹變形差r927.410-62當(dāng)量壓力組合PcMPa-2.6453有效壓力組合PaMPaPa=sPs-tPt+rEt19.154基本法蘭力矩系數(shù)=4Mm/（Di3Pa）0.00265管板邊緣力矩系數(shù)= +M10.00836管板邊緣剪切系數(shù)vv= 0.277管程總彎矩系數(shù)m0.678系數(shù)G1G1=maxGLe，GLe0.2939系數(shù)0.10310系數(shù)0.29311管板布管區(qū)周邊外徑向的應(yīng)力系數(shù)=3（1+v）m/4K（Q+G2）0.0119212管板布管區(qū)周邊外徑向的應(yīng)力系數(shù)MPa=Pa（/）（Di/）21-K/m+K2（1.414-m）/2m350.73tr13管板布管區(qū)周邊的剪切應(yīng)力系數(shù)p0.04614管板布管區(qū)周邊的剪切應(yīng)力pMPap=pPa（/）（Dt/）7.111.5tr15換熱管的軸向應(yīng)力MPa=Pc-Pa11.93tr16換熱管與管板連接的拉托應(yīng)力qMPaq=ta/dl0.00890.5trH、由管板計(jì)算厚度來(lái)確定管板的實(shí)際厚度：序號(hào)項(xiàng)目符號(hào)單位數(shù)據(jù)來(lái)源和計(jì)算公式數(shù)值備注1管板計(jì)算厚度mm192.62殼程腐蝕裕量C1mm23管程腐蝕裕量C2mm24結(jié)構(gòu)開(kāi)槽深度h1mm根據(jù)結(jié)構(gòu)確定35管板的實(shí)際厚度mm200考慮圓整2.1.9是否安裝膨脹節(jié)的判定： 由八.G.a、b、c、d計(jì)算結(jié)果可以看出：四組危險(xiǎn)組合工況下，換熱管與管板的連接拉托力均沒(méi)超過(guò)設(shè)計(jì)許用應(yīng)力，并且各項(xiàng)應(yīng)力均沒(méi)超過(guò)設(shè)計(jì)許用應(yīng)力。所以，不需要安裝膨脹節(jié)。10、折流板尺寸的確定：序號(hào)項(xiàng)目符號(hào)單位數(shù)據(jù)來(lái)源和計(jì)算公式數(shù)值1折流板的厚度mmGB151-1999項(xiàng)目5.9.2-2162折流板的直徑DmmGB151-1999表4111943折流板直徑的允許偏差mmGB151-199911940-0.84折流板的材料mmQ235-A5折流板的缺口高度lmmGB151-1999 P73圖166折流板的弦高h(yuǎn)mmGB151-1999 P71圖2402.1.10各管孔接管及其法蘭的選擇：根據(jù)公式d=263.44m取d=300mm，由鋼制法蘭、墊片、緊固件選擇板式平焊法蘭，相關(guān)尺寸如下：a、 b進(jìn)出水口接管法蘭的選擇：序號(hào)項(xiàng)目符號(hào)單位數(shù)據(jù)來(lái)源和計(jì)算公式數(shù)值1接管公稱直徑DNHG20593-97表4-53002接管外徑HG20593-97表4-53253法蘭外徑HG20593-97表4-54404螺栓中心圓直徑KHG20593-97表4-53955螺栓孔直徑HG20593-97表4-5226螺栓孔數(shù)量n個(gè)HG20593-97表4-5127螺紋HG20593-97表4-5M27168法蘭厚度HG20593-97表4-5249法蘭內(nèi)徑HG20593-97表4-532810坡口寬度HG20593-97表4-51111法蘭理論重量表4-546.812法蘭密封面形式HG20593-97RF13法蘭密封面尺寸sHG20593-97表8.0.1614法蘭密封面直徑DHG20592-97324C、蒸汽入口接管法蘭的選擇，設(shè)水蒸氣的流速,則根據(jù)公式 d=m取d=350mm,由HG/T 2059220635-2009鋼制管法蘭、墊片、緊固件選擇板式平焊法蘭(PL)，相關(guān)尺寸如下：序號(hào)項(xiàng)目符號(hào)單位數(shù)據(jù)來(lái)源和計(jì)算公式數(shù)值1接管公稱直徑HG/T 20592-2009表8.2Use of Vapor Barriers to Prevent CondensationWhenever insulation is installed in a wall, roof, or slab, its resistance to the flow of heat is so much greater than that of the other elements of the construction that the dew point and resulting condensation may occur within the insulation.Since water vapor flows from regions of high temperature to regions of low temperature, a simple solution to condensation is to stop the flow of water vapor by means of some surface material impervious to moisture-provided this surface is called a vapor barrier. It must always be applied on the warm side.Because condensation is generally most severe during the heating season, all vapor barriers should be installed on the interior side of walls and roofs. From a practical standpoint, this means that the vapor barrier should be next to and part of the insulation.One of the best and most economical vapor barriers is aluminum foil. Some insulation come equipped with this foil attached to one surface. However, unless reinforced with kraft paper or some other strong material, the foil is easily ripped, torn, or punctured, and so is of little value as a barrier. Since vapor behaves as a gas, a vapor barrier, to be effective, must be airtight, or as nearly so as possible. But this is often an impractical requirement. For example, consider a roof with the insulation above the deck and between a vapor barrier and waterproof roofing. Unless the insulation is of a firm material, the insulation to expand, forming bubbles under the waterproofing. During the coolness of the night, the bubbles will contract. After a series of sunny days and cool nights, the bending back and forth of the surface may destroy the roofing. One way to prevent this is to side-vent the roof insulation so the contained air can freely expand and contract. The side vents must, however, be protected from driving rain.Vapor barriers can be made of other materials besides aluminum foil. There are aluminum paints, plastic paints, some plastic films, asphalt paints, rubber-base paints, asphalt, and foil-laminated papers. It must be remembered that water repellent surfaces are not necessarily vapor barriers, that is, airtight.To evaluate a vapor barrier, a unit known as the perm is used. It is defined as a vapor-transmission rate of 1 grain of water vapor through 1 square foot of material per hour when the vapor-pressure difference is equal to q inch of mercury (7,000 grains equal 1 pound). A material having a vapor-transmission rate of 1 perm or less is considered a good vapor barrier. The corresponding unit for permeance of 1-in. thickness is perm-inch.Resistance to vapor transmission is the reciprocal of the permeance.Since vapors flow from the warm side of a wall or roof to the cold side, the exterior surface should be as porous as possible or vented and yet offer protection against penetration of rain. This is particularly important with “blown-in” insulation as applied to frame houses, for which a vapor barrier generally cannot be installed. This type of insulation also involves another principle, which, if ignored, frequently is the cause of peeling of paint and leads to unnecessary repair of rain gutters that do not leak. “Blown-in” insulation is sprayed into the spaces between the studs of frame construction. The interior surface is generally lath and plaster, or wall-board-both porous. The exterior is generally wood sheathing, with shingles, clapboards, or stucco. The heat resistance of the insulation is such that during the winter the location of the dew point falls within the insulation. Theoretically, the resulting condensation should occur within the insulation. This, however, does not occur. Condensation, when it within the insulation, but on the inside surface of the sheathing. The principle involved is this: Whenever the dew point occurs within a material, condensation will not occur until the flow of water vapor encounters the surface of another material of greater resistance to the flow of water vapor. That is, as long as the air can keep on moving, it will carry the moisture along with it and will not deposit the moisture until it reaches a surface that resists its flow and is colder than the dew point.The problem inherent in blown-in insulation can be solved by“cold-side venting.” In applying blown-in insulation, an opening usually is drilled through the exterior wall surface between each pair of studs. These holes should never be scaled, only covered with porous water-repellent material for protection against the weather. Then, whatever water vapor flows through the inside porous finish can escape to the cold air outside without condensing. With clapboard construction,“toothpick” wedges may be driven under the lower edge of each clapboard to provide the required openings for breathing.To sum up: vapor barriers, or as much resistance as possible to vapor flow (or air) should be provided on the warm side of walls and roofs. Openings or porous materials-as little resistance as possible to vapor flow-should be provided on the cold side.If vapor barriers were perfect, cold-side venting would not be required. Unfortunately, vapor barriers are not perfect; therefore, cold-side venting is worthwhile insurance against failure of insulation in all cases.The discussions above of winter condensation seem to contradict summer requirements when the warm and cold sides of a construction are the reverse of what they are in winter. In most parts of the United States, however, cooling seldom results in maintenance of inside temperatures more than15F below outside conditions, whereas in winter, inside temperatures ate generally maintained at 60 to 75F above outside conditions. So in winter, the prevailing maximum temperature differences are from four to five times what they are in summer. Furthermore, in summer very little cooling is required during the night. Hence, as far as insulation is concerned, summer condensation is so intermittent that it can be completely disregarded for the average structure and average occupancy. It should be mentioned, however, that in low-temperature work, such as cold storage rooms and low-temperature test cells special conditions arise for which it is best to refer to a specialist.使用隔汽層防止冷凝只要在墻、屋蓋、或樓板內(nèi)放置絕熱層，由于它抵抗熱的能力比其它構(gòu)件大得多，在絕熱層內(nèi)可能形成露點(diǎn)和由此產(chǎn)生的冷凝現(xiàn)象。由于水汽從高溫區(qū)流向低溫區(qū)，解決冷凝的一個(gè)簡(jiǎn)單方法是用某種不透水的表面材料（只要它永遠(yuǎn)在露點(diǎn)以上）阻止水汽的流動(dòng)。這種表面稱為隔汽層。它應(yīng)永遠(yuǎn)裝在暖面。因?yàn)槔淠F(xiàn)象通常在采暖季節(jié)最為嚴(yán)重，因?yàn)槔淠F(xiàn)象通常在采暖季節(jié)最為嚴(yán)重，因此所有隔汽層都必須設(shè)在墻和屋頂?shù)膬?nèi)側(cè)。從實(shí)際的觀點(diǎn)出 ，這意味著隔汽層應(yīng)緊貼絕熱層并構(gòu)成絕熱層的一部分。最好最經(jīng)濟(jì)的隔汽層之一是鋁箔。有些絕熱層事先有一面裝有鋁箔。但是除非有牛皮紙或其它結(jié)實(shí)材料加固，這種鋁箔很容易被割裂、扯破、或穿孔,所以用作隔汽層沒(méi)有多大價(jià)值.因?yàn)樗男再|(zhì)和氣體一樣,隔汽層必須不透氣或盡可能不透氣才能生效.但這往往不切合實(shí)際要求。例如，一個(gè)屋蓋上的絕熱層位于隔汽層和屋面防水層之間。除非絕熱層是一種堅(jiān)固的材料，如泡沫玻璃，否則太陽(yáng)的熱力將使絕熱層中的空氣膨脹，在防水層下形成氣泡。晚上涼爽時(shí)，氣泡將收縮。在一連串出太陽(yáng)的白天和涼爽的夜晚之后，表面漲而復(fù)縮將會(huì)破壞屋頂。防止這種現(xiàn)象的一種方法是使屋頂絕熱層有側(cè)邊透氣孔，內(nèi)部的空氣能自由地膨脹和收縮。不過(guò)，側(cè)邊透氣孔必須防止雨水滲入。除了鋁箔，隔汽層還可用別的材料。有鋁涂料，塑料涂料，某些塑料薄膜，瀝青涂料，橡膠類涂料，瀝青，和金屬箔層壓紙板。必須記住，防水表面不一定是隔氣層，也就是說(shuō)，不一定是不透氣的。為估計(jì)隔汽層的優(yōu)劣，使用了一種叫做perm的單位。其定義為：當(dāng)水汽壓力差等于1英寸水銀柱時(shí)，每小時(shí)通過(guò)一平方英尺材料為一粒水汽的水汽傳輸率（7，000粒等于是磅）。水汽傳輸率為1perm或者1perm以下的材料就是優(yōu)質(zhì)隔汽層。滲透1英寸深的相應(yīng)單位為1perm-英寸?？顾麄鬏?shù)哪芰κ菨B透能力的倒數(shù)。因?yàn)樗麖膲蛭蓓數(shù)呐媪飨蚶涿?，外表面?yīng)盡可能多孔或通風(fēng)，同時(shí)又要防止雨水浸入。對(duì)于構(gòu)架房屋用的“噴吹”絕熱層，這一點(diǎn)尤為重要，這種房屋通常不能設(shè)隔汽層。這種絕熱層還涉及到另一原理，這一原理若被忽略了，常常引起油漆剝落，并導(dǎo)致不必要的修理雨水槽，其實(shí)它并不漏?！皣姶怠苯^熱層被噴入構(gòu)架結(jié)構(gòu)墻筋之間的空隙。內(nèi)表面通常是板條和灰泥，或木板都是多孔的。外表面通常是帶魚(yú)鱗板，護(hù)壁楔形板，或粉飾的木襯板。在冬天由于絕熱層的抗熱性使露點(diǎn)落在絕熱層之內(nèi)。從理論上講，由此而產(chǎn)生的冷凝也應(yīng)發(fā)生在絕熱層內(nèi)。但事實(shí)并非如此。如發(fā)生冷凝，它并非發(fā)生在絕熱層內(nèi)露點(diǎn)區(qū)內(nèi)，而是在襯板的內(nèi)表面上。所涉及到的原理是這樣的：每當(dāng)材料內(nèi)部產(chǎn)生露點(diǎn)時(shí)，要等到水汽流接觸到對(duì)水汽流阻力更大的另一種材料的表面時(shí)，才會(huì)產(chǎn)生冷凝。也就是說(shuō)，只要空氣繼續(xù)流動(dòng)。它就攜帶著水汽，直至它接觸到能抵抗其流動(dòng)而又比露點(diǎn)更冷的表面，才使水汽附著下來(lái)。噴吹絕熱層所固有的這一缺點(diǎn)可用 “冷側(cè)通風(fēng)”法來(lái)解決。在采用噴吹絕熱層時(shí)，通常在外墻表面每對(duì)墻筋之間鉆通一個(gè)孔口。這些孔口決不可封死，只能用多孔防水材料覆蓋以免雨水浸入。于是，無(wú)論什么水汽流到多孔罩面層的內(nèi)側(cè)，都可逃逸到外邊的冷空氣中而不致凝結(jié)。護(hù)壁楔形板結(jié)構(gòu)的牙簽形楔子可楔入每塊板的下端，形成足夠的孔口，供通風(fēng)之用?？傊?，隔汽層，即對(duì)水汽流（或空氣）有盡可能抵抗力的材料，應(yīng)放在墻和屋頂?shù)呐瘋?cè)，而開(kāi)孔或多孔性材料，即對(duì)水汽流有盡可能少抵抗的材料，應(yīng)放在冷側(cè)。如隔汽層優(yōu)良，冷側(cè)的通風(fēng)孔就沒(méi)有必要了。遺憾的是，隔汽層總是欠佳；因此，冷側(cè)通風(fēng)孔無(wú)論在什么情況下都是預(yù)防絕熱層失效的可靠保證。上述有關(guān)冬季結(jié)露現(xiàn)象的討論似乎與夏季的要求相互矛盾，因?yàn)樵谙牧顣r(shí)節(jié)，結(jié)構(gòu)的冷側(cè)和暖側(cè)與冬季正好相反。然而，在美國(guó)大部分地區(qū)，空調(diào)很少使室內(nèi)溫度低于室外溫度15F以上，而冬天的室內(nèi)溫度通常保持在高于室外溫度60至理名言75F之間。因此冬季的最在溫差多為夏季的四至五倍。而且，夏季的夜晚幾乎不需要空調(diào)。因此，對(duì)于一般用途的絕熱層而言，夏季這種不連續(xù)的結(jié)露現(xiàn)象，完全可以忽略不計(jì)。然而應(yīng)當(dāng)指出，對(duì)制冷工藝（如冷藏室和低溫試驗(yàn)庫(kù)）中出現(xiàn)的特殊條件，最好請(qǐng)教有關(guān)專家。熊洪權(quán) 0204003
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