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  本文關(guān)鍵詞：三分螺旋折流板電加熱器流動和傳熱性能研究　出處：《東南大學(xué)》2016年碩士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 電加熱器 三分螺旋折流板 折耳 周向重疊 “斜日字”單元 溫度均勻性

【摘要】：三分螺旋折流板電加熱器是針對工業(yè)工程中常用的多圈環(huán)形分層布管方式弓形折流板電加熱器優(yōu)化改進(jìn)而來的新型方案,采用“斜日字”單元環(huán)形布管方案解決了多圈環(huán)形布管方案因管間距不統(tǒng)一導(dǎo)致在保持最小管間距時殼體尺寸較大,且對流動和傳熱不利的問題；以周向重疊三分螺旋折流板取代弓形折流板強(qiáng)化電加熱器流動和傳熱性能,在繼承螺旋折流板高效低阻特性的同時,避免了弓形折流板方案存在有流動死區(qū)、傳熱系數(shù)偏低、流動阻力較大,易誘導(dǎo)振動、易結(jié)垢等缺點(diǎn),極大地改善了加熱管表面溫度均勻性問題。在此基礎(chǔ)上,為改善三分螺旋折流板加工、安裝及固定不便的問題,設(shè)計(jì)了折耳三分螺旋折流板,將原有扇形三分螺旋折流板兩端靠近拉桿孔位折彎形成,折耳折流板方案進(jìn)一步改善了三角區(qū)漏流,同時取消了原三分方案中環(huán)形端板,并消除了其阻礙流體的負(fù)面影響,優(yōu)化了流場及溫度場,延長了電加熱器使用壽命,且結(jié)構(gòu)緊湊,加工方便,定位和安裝簡單,因每套拉桿套管組可緊固兩組相鄰折流板,拉桿套管組的數(shù)目亦是最少,對電加熱器的節(jié)能優(yōu)化設(shè)計(jì)具有良好的效果。本文首先針對電加熱器流動與傳熱特性,建立了“斜日字”單元環(huán)形布管的弓形折流板、三分螺旋折流板、折耳三分螺旋折流板3種折流板電加熱器的物理及數(shù)學(xué)模型,采用數(shù)值模擬軟件FLUENT和可視化分析軟件TECPLOT等手段,深入研究了上述三種電加熱器內(nèi)的流動與傳熱及表面溫度均勻性特性。其次,在數(shù)值對比研究三種電加熱器方案各項(xiàng)性能參數(shù)指標(biāo)的基礎(chǔ)上,為深入研究各方案流動換熱特性,采用可視化分析軟件結(jié)合數(shù)據(jù)分析對比考察了各方案的速度場、壓力場、溫度場,加熱管表面換熱系數(shù)及壁面溫度分布,重點(diǎn)分析了換熱系數(shù)、綜合指標(biāo)、加熱管表面平均溫度及最高溫度等指標(biāo),揭示了“斜日字”布管、周向重疊搭接方式下,折流板結(jié)構(gòu)形式對三分螺旋折流板電加熱器加熱性能的影響。綜合研究了折流板傾斜角對折耳三分螺旋折流板電加熱器流動與傳熱性能影響,設(shè)計(jì)了折流板傾斜角為20°、25°、300及300雙螺旋等方案,尋找出在此設(shè)計(jì)條件下流動與傳熱綜合指標(biāo)及電加熱管表面溫度均勻性指標(biāo)最高下最佳傾斜角為25°。第三,在此基礎(chǔ)上數(shù)值模擬研究了三分螺旋折流板電加熱器在不同結(jié)構(gòu)形式下加熱性能。為進(jìn)一步揭示所改進(jìn)的折耳方案流動特性,對比研究了等傾斜角與等螺距的無折耳與折耳三分螺旋折流板方案的流場與壓力場；為探究三分螺旋折流板方案換熱潛力,設(shè)計(jì)了2種管長縮短方案并進(jìn)行了表面溫度均勻性分析；為改善大傾斜角下?lián)Q熱性能下降的問題,進(jìn)行了雙螺旋與單螺旋方案流動換熱性能的對比研究；研究了電加熱器管束方位與入口接管的相對位置對加熱性能的影響；從強(qiáng)化傳熱的目的出發(fā),探索了允許壓降下?lián)Q熱系數(shù)最優(yōu)方案。數(shù)值結(jié)果表明,折耳三分螺旋折流板方案高效低阻特性明顯,既繼承了三分螺旋折流板優(yōu)異的流動換熱性能,又簡化了電加熱器結(jié)構(gòu),并極大改善了電加熱管表面溫度均勻性,相比于相同工況下弓形方案可將換熱系數(shù)及綜合指標(biāo)分別提升7%-20%,24%-32%,同時加熱管表面平均溫度及最高溫度分別下降15K-50K,130K-151K。折耳三分螺旋折流板方案可在保持三分方案優(yōu)異的換熱性能基礎(chǔ)上,優(yōu)化流場及溫度場,并改善三分螺旋折流板不易加工及安裝定位等問題。對管長縮短方案的研究結(jié)果表明,三分螺旋折流板方案可減小加熱面積30%以上；而允許壓降下最佳方案的研究表明相同壓降下,三分螺旋折流板對電加熱器換熱性能提升明顯,同時能大幅降低加熱管表面最高溫度,減少局部高溫區(qū),增加運(yùn)行安全性。第四,針對流體介質(zhì)為液體的導(dǎo)熱油電加熱器在變工況下的加熱性能進(jìn)行了數(shù)值模擬研究,結(jié)果表明傾斜角為15°周向重疊折耳三分螺旋折流板導(dǎo)熱油電加熱器與板間距為100mm的弓形折流板方案相比,換熱系數(shù)及綜合指標(biāo)分別提升18%、17%,同時加熱管表面平均溫度及最高溫度分別下降14K、94K,幾乎消除了弓形方案中所普遍存在的局部高溫區(qū)。
[Abstract]:Three spiral baffle plate electric heater is a new scheme for multi ring ring bow cloth tube commonly used methods in industrial engineering baffle electric heater optimization to improve, the cable on the word "unit ring cloth tube solves the multi circle pipe for pipe spacing a result in keeping the minimum shell when the tube spacing is large in size, and the flow and heat transfer problem of circumferential overlap three points; with helical baffles instead of segmental baffles to strengthen the electric heater flow and heat transfer performance of plate flow, in the succession of spiral baffle plate with high efficiency and low resistance characteristics at the same time, to avoid the baffle scheme there is a dead flow zone the heat transfer coefficient, low flow resistance, large, easily induced vibration, easy fouling and other shortcomings, greatly improving the heating tube surface temperature uniformity. On this basis, for the baffle plate processing, installation and fixation of three spiral inconvenience to improve the problem of designing three fold helical baffles, the original fan three helical baffle rod holes near the ends of bending forming, fold the baffle plan to further improve the triangle leakage current, at the same time cancel the original ring three scheme in the end plate, and to eliminate the negative influence of blocking fluid, optimization of the flow field and temperature field, prolong the service life of the electric heater, and has the advantages of compact structure, convenient processing, simple installation and positioning, because each rod casing group fastening two adjacent baffle plates, the number of rod sleeve the group is also the least, the electric heater has a good effect of energy saving optimization design. In this paper, the electric heater flow and heat transfer characteristics, established a "slant on the word" unit annular tube baffle, three helical baffles, fold three spiral baffle 3 models of physics and mathematics baffled the electric heater, using the software of FLUENT and visual analysis software TECPLOT the numerical simulation method, in-depth study of the above three kinds of electric heater in the flow and heat transfer characteristics and surface temperature uniformity. Secondly, based on the comparison of three numerical electric heater performance parameters, to further study the scheme of flow and heat transfer characteristics, using visual analysis software combined with data analysis and contrast the effects of the scheme of velocity field and pressure field and temperature field, heating tube surface heat transfer coefficient and wall temperature distribution, key analysis of the heat transfer coefficient, comprehensive index, heating surface average temperature and maximum temperature index, reveals the "slant on the word" cloth tube, circumferential overlap mode, the baffle plate structure affect the form of the three points spiral baffle plate electric heater heating performance. A comprehensive study of the baffle angle fold ear three spiral baffle plate electric heater effect of flow and heat transfer performance, design of the baffle angle is 20 degrees, 25 degrees, 300 and 300 double helix scheme, to find out the design under the condition of flow and heat transfer in comprehensive index and the electric heating tube surface temperature the uniformity of the highest index under the optimum tilt angle of 25 degrees. Third, on the basis of the numerical simulation, the heating performance of the three - point spiral baffle electric heater in different structure forms is studied. For the fold scheme further reveal the improved flow characteristics, we studied the flow field and pressure field with three fold fold helical baffle scheme etc. tilt angle and pitch; the baffle plan for heat potential of three spiral inquiry, 2 design scheme and the length of shortening analysis of surface temperature uniformity; to improve the heat transfer performance of a large tilt angle decreased, compared with the scheme of double helix single spiral flow and heat transfer performance; influence of the relative position of the electric heater tubes and take over the entrance range on the heating performance; starting from the purpose of heat transfer enhancement, explore the heat under the optimum allowable pressure drop coefficient. The numerical results show that the three fold helical baffle scheme of high efficiency and low resistance characteristics is obvious, not only inherited the three helical baffles excellent flow and heat transfer performance, but also simplifies the structure of the electric heater, and greatly improve the electric heating tube surface temperature uniformity, compared to the same condition can be changed T. the heat transfer coefficient and comprehensive index were increased 7%-20%, 24%-32%, and the surface of the heating pipe average temperature and maximum temperature decrease of 15K-50K, 130K-151K. The three fold helix baffle scheme can optimize the flow field and temperature field on the basis of keeping the excellent heat transfer performance of the three points, and improve the problem of three point spiral baffle plate's hard processing and installation location. Study on the length of shortening scheme. The results show that the three spiral baffle scheme can reduce the heating area of more than 30%; and allows the pressure drop of best scheme shows that the same pressure drop, three spiral baffle plate for electric heater heat transfer performance significantly, and can significantly reduce the heating surface of the tube maximum temperature, reduce local the high temperature zone, increase operation safety. Fourth, the fluid medium for conducting oil liquid electric heater in the heating performance condition is studied by numerical simulation. The results show that the tilt angle of 15 degrees to three week overlap fold helical baffle heat conduction oil heater and plate spacing of 100mm baffle scheme compared to heat transfer coefficient and the comprehensive index were increased by 18% and 17%, while the average surface temperature of heating pipe and the highest temperature decreased 14K and 94K respectively, virtually eliminates the local high temperature zone exists in the bow.
【學(xué)位授予單位】：東南大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2016
【分類號】：TK172

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