【正文】
e number of processes for every 1 NTUe, then NTUE = n? NTUe (where n is the number of processes). When NTUe = NTUE = NTUp, the heat exchanger for oneway. If NTUeNTUp, the heat exchanger for many processes, it should be designed to target n. As each plate of oneway NTUe value is essentially fixed value, such as in e Table 2 for the flow of 25 m3 / h of the oneway NTUe plate heat exchanger for 17 square meters. From NTUe = A?K / MC tells us that when NTUe to be on duty, A?K is inversely proportional, still e example, when K = 500kcal /㎡?h?℃ time, A = 25000/500 = ㎡, the process of n = ≈5. When K = 2500kcal / ㎡?h? ℃ time, A = square meters, the flow of n = 1. Each process NTUe as follows: K = 500, NTUe = NTUE / n = , K = 2500 when, NTUe = . So, can be obtained under NTUe the flow of heat exchangers, heat transfer coefficient and heat transfer area. From the above we can see that if the plate heat exchanger design unreasonable and likely to heat transfer area is too large, may also be partitioned so that flow is too high, too much resistance. plate heat exchanger manufacturing and technological progress, plate type of increase, raising the plate heat exchanger of the various processes of adaptation. (1)the NTU (∽ 8), small △tm (∽1 ~ 2) the plate heat exchanger to meet the district cooling and heat pump units evaporator, condenser requirements. From the above analysis know, △tm is the driving force of heat transfer, if △tm small, means that the driver of small, to achieve the heat transfer between the two fluid, we must increase heat transfer coefficient, increasing heat transfer area, in order to Heat to make up too large, is the only increase heat transfer coefficient K. (2)small NTU (∽ ~ 2), the △tm (∽40 ~ 90 ℃) of the plate heat exchanger to meet the heat recovery process and the process heating and cooling requirements. When the process in the △tm conducted under conditions of heat transfer, that driving force, the heat and the smaller, the heat transfer coefficient demand is not high, but that this process or highpressure work, or work High temperature, or process heating and cooling process in the liquid containing fiber diameter or larger particles, the plate heat exchanger, the pressure, temperature and ability to request, the heat exchanger to the plate spacing requirements. 換熱器的優(yōu)化選型W. Lub和 . Tassoub 英國米德爾塞克斯,布魯內(nèi)爾大學(xué)機(jī)械設(shè)計(jì)工程部 [摘要]板式換熱器的優(yōu)化選型是根據(jù)換熱器的用途和工藝過程中的參數(shù)和 NTU=KA/MC=△t/△tm,即傳熱單元數(shù)NTU和溫差比(對(duì)數(shù)平均溫差—換熱的動(dòng)力)選擇板片形狀、板式換熱器的類型和結(jié)構(gòu)。 到此,換熱器結(jié)構(gòu)設(shè)計(jì)及強(qiáng)度計(jì)算已經(jīng)基本結(jié)束。(2)折流板外圓表面粗糙度值不大于,外圓面兩側(cè)的尖角應(yīng)倒鈍。(3)換熱管與管板的強(qiáng)度焊焊接接頭,接施焊前應(yīng)按GB 1511999《管殼式換熱器》中附B作焊接工藝評(píng)定。(2)焊渣及凸出于換熱管內(nèi)壁的焊瘤均應(yīng)清除。 換熱管與管板的連接換熱管與管板的連接是管殼式換熱器中最主要的問題,因?yàn)閮烧咧g的連接處通常是換熱器容易滲透的地方,若連接質(zhì)量不好,則直接影響工藝操作的正常進(jìn)行。 終鉆后應(yīng)抽查不小于管板中心角區(qū)域內(nèi)的孔橋?qū)挾?,值得合格率?yīng)不小于,允許的最小寬度的數(shù)量應(yīng)控制在之內(nèi),超過上述合格率時(shí),應(yīng)全管板檢查。(2)孔橋?qū)挾绕? 管板上有很多管孔,其孔心距尺寸偏差的大小直接影響焊管和脹管的施工質(zhì)量,所以限制鉆孔背面的孔橋?qū)挾绕睿员阌跈z查。用于焊接時(shí),管端清理長(zhǎng)度應(yīng)不小于管外徑,且不小于。組裝、焊接管箱隔板,靠近密封面區(qū)域需焊透,防應(yīng)力集中而開裂。且螺孔應(yīng)與設(shè)備主軸中心線跨中。(7)插入式接管、管接頭等,除圖樣另有規(guī)定外,不應(yīng)伸出管箱、殼體和頭蓋的內(nèi)表面。(5)殼體內(nèi)壁凡有礙管束順利裝入或抽出的焊縫均應(yīng)磨至與母材表面齊平。 在本設(shè)計(jì)中其值不大于。(2)圓筒同一斷面上,最大直徑與最小直徑之差為, 且:當(dāng)時(shí),其值不大于; 當(dāng)時(shí),其值不大于; 在本設(shè)計(jì)中其值不大于。11換熱器的制造與檢驗(yàn)要求 圓筒(1)圓筒內(nèi)直徑允許偏差① 用板材卷制時(shí),內(nèi)直徑允許偏差可通過外圓周長(zhǎng)加以控制,其外圓周長(zhǎng)允許偏差為;下偏差為零。 鞍座安裝位置(2)布置 選用兩個(gè)鞍式支座,固定式和滑動(dòng)式支座各一個(gè)。 鞍座尺寸公稱直徑DN允許載荷Q(KN)鞍座高度h底板腹板筋板墊板螺栓間距l(xiāng)2 鞍座質(zhì)量(kg)增加100mm高度增加的質(zhì)量(kg)l1b1 l3b3 弧長(zhǎng)b4e800220200720150101040012010940260665530438 (1) 原則 ① 當(dāng)時(shí),??; ② 當(dāng)時(shí),??; ③ 盡量使和相近。 III封頭的質(zhì)量是兩個(gè)封頭質(zhì)量相加:; IV附件(如接管、法蘭、浮頭蓋等)質(zhì)量取為全部質(zhì)量的20%: V圓筒的體積:; 封頭的體積:; 故總體積為:; 水壓試驗(yàn)時(shí)充液重量:; 水壓試驗(yàn)時(shí)總質(zhì)量: 水壓試驗(yàn)時(shí)支座反力: 鞍座的型號(hào)及尺寸根據(jù)支反力查JB/T471292選擇鞍座的型號(hào)為:DN800、120176。 參數(shù)如表43: 標(biāo)記:法蘭 表43 長(zhǎng)頸對(duì)焊法蘭相關(guān)參公稱直徑 連接尺寸, 900 1060 1015 976 966 936 21 18 27公稱直徑 高頸尺寸, 法蘭盤厚度質(zhì)量 螺柱 52 規(guī)格數(shù)量 9001153516 26 12 M27 3210鞍座 支反力計(jì)算(1)管板的質(zhì)量按相同體積的圓平板計(jì)算,且取固定管板和浮動(dòng)管板的體積相同。 參數(shù)如表42: 標(biāo)記:法蘭 表42 長(zhǎng)頸對(duì)焊法蘭相關(guān)參數(shù)公稱直徑 連接尺寸, 800 915 880 850 840 837 17 14 18公稱直徑 高頸尺寸, 法蘭盤厚度質(zhì)量 螺柱 36 規(guī)格數(shù)量 800115 3516 26 12 M16 36根據(jù)殼程操作條件,選纏繞式墊片: (1)材料為鍛件20MnMoⅡ,凹密封面。 管箱法蘭屬于壓力容器法蘭。9 法蘭與墊片換熱器中的法蘭包括管箱法蘭、殼體法蘭、浮頭蓋法蘭以及接管法蘭。 7 鉤圈鉤圈的型式查GB151可知選為B型鉤圈,其圖示如下:而其設(shè)計(jì)厚度可按下式計(jì)算: 其中:——鉤圈設(shè)計(jì)厚度,mm; ——浮動(dòng)管板厚度,mm; 則8分程隔板由于是多管程換熱器,故此處需要用到分程隔板。6 防沖板 防沖板是在換熱器中為了防止流體直接沖刷管子而引起管子振動(dòng)失穩(wěn)和腐蝕而設(shè)置的。 拉桿的直徑、數(shù)量及布置其具體尺寸如下所示 拉桿的參數(shù)其中拉桿的長(zhǎng)度L按需要確定。 當(dāng)管板比較薄時(shí),也可采用其他的連接結(jié)構(gòu)。查得管子材料屈服應(yīng)力[5],比值,系數(shù)為 由,由公式得為 (8)管板開孔后面積 (9)管板布管區(qū)面積 隔板槽面積 其中:——沿隔板槽一側(cè)的排管根數(shù),取30; ——隔板槽兩側(cè)相鄰管中心距,由表41取。 假設(shè)管板計(jì)算厚度。 管板與管箱的連接方式 管板材料在本設(shè)計(jì)中根據(jù)流體性質(zhì),考慮輕微腐蝕,選用Q245R。 管板與管箱的連接