發(fā)布時(shí)間：2018-04-16 02:27

  本文選題：纏繞管式換熱器 + 數(shù)值模擬　； 參考：《青島科技大學(xué)》2017年碩士論文

【摘要】：纏繞管式換熱器是一種高效的管殼式換熱器,具有結(jié)構(gòu)緊湊、雜質(zhì)沉積率小、管內(nèi)操作壓力高、換熱效率高的優(yōu)點(diǎn)。本文采用三維建模軟件SolidWorks建立了纏繞管式換熱器的物理模型,利用Fluent流場(chǎng)模擬軟件,對(duì)換熱器內(nèi)部流場(chǎng)進(jìn)行了數(shù)值模擬,研究了纏繞管式換熱器內(nèi)部流場(chǎng)及傳熱特性。針對(duì)纏繞管式換熱器殼程壓降大的缺點(diǎn),提出了新型水滴型截面換熱管并進(jìn)行了數(shù)值模擬。研究工作可對(duì)纏繞管式換熱器的設(shè)計(jì)開(kāi)發(fā)提供指導(dǎo)。(1)考察了不同入口流速不同截面處的纏繞管式換熱器殼內(nèi)流體的流動(dòng)特性,結(jié)果表明:管程流體中,由于纏繞半徑小,內(nèi)層管相比外層管的PEC指數(shù)高11.7%,具有更好的換熱效果;殼程內(nèi),在纏繞管間存在著由外側(cè)高速區(qū)向內(nèi)層纏繞管運(yùn)動(dòng)的徑向流,徑向流有助于促進(jìn)外層冷流體與換熱管管壁間的熱量交換,且隨著入口流速的增大,徑向流也逐漸增大,當(dāng)入口流速為0.7m/s時(shí),徑向流速可達(dá)1.2m/s。隨著入口流速的增加,殼程的湍動(dòng)強(qiáng)度更高,入口流速為0.5m/s時(shí),湍動(dòng)能最大為0.03m2/s2,提高了殼程的傳熱效果。(2)建立了平行排列、交叉排列和錯(cuò)位排列三種不同的纏繞管排布方式,考察了纏繞管式換熱器內(nèi)管排列方式及入口流速對(duì)殼側(cè)流動(dòng)、傳熱性能的影響。模擬結(jié)果表明:交叉排列具有更高的阻力系數(shù),大約比其它兩種排列高出10%;與平行排列方式相比,采用錯(cuò)位排列方式時(shí)由于纏繞管的導(dǎo)流作用,管間存在較大的徑向速度,促進(jìn)纏繞管外側(cè)流體與纏繞管周圍流體的混合,管后低速區(qū)面積亦大大減少,強(qiáng)化了流體傳熱,PEC指數(shù)大約高出25%;溫度分布也更加均勻。(3)對(duì)新型水滴形截面換熱管的換熱器,通過(guò)數(shù)值模擬,結(jié)果表明:與普通圓管的換熱器的對(duì)比,水滴形換熱管的管內(nèi)流體分布更均勻;高速流體和高溫流體分布更均勻,有利于熱量的傳遞。殼程內(nèi),雖然水滴形管的換熱器的努塞爾數(shù)Nu有一定的降低,但其阻力系數(shù)f和壓降有大幅度減小,當(dāng)入口流速為0.4m/s時(shí),水滴形管的努塞爾數(shù)Nu是圓管的94.2%,而其阻力系數(shù)f只有圓管的75%,PEC指數(shù)提高了5%,大大減小了由于殼程阻力帶來(lái)的壓力損失。
[Abstract]:Winding tube heat exchanger is an efficient tube and shell heat exchanger with the advantages of compact structure, low impurity deposition rate, high operating pressure and high heat transfer efficiency.In this paper, the physical model of the winding tube heat exchanger is established by using the three-dimensional modeling software SolidWorks, and the flow field and heat transfer characteristics of the winding tube heat exchanger are numerically simulated by using the Fluent flow field simulation software.Aiming at the disadvantage of large pressure drop in the shell side of the winding tube heat exchanger, a new type of water droplet cross section heat transfer tube is proposed and numerically simulated.The research work can provide guidance for the design and development of the winding tube heat exchanger. (1) the flow characteristics of the fluid in the shell of the winding tube heat exchanger with different inlet velocity and different cross section are investigated. The results show that the winding radius is small in the pipe side fluid.The inner tube has a better heat transfer effect than the outer tube with a PEC index of 11.70.There is a radial flow from the outer high speed region to the inner winding tube in the shell side.The radial flow can promote the heat exchange between the outer cold fluid and the tube wall, and the radial flow increases gradually with the increase of the inlet velocity. When the inlet velocity is 0.7m/s, the radial velocity can reach 1.2 m / s.With the increase of inlet velocity, the turbulent intensity of shell side is higher. When the inlet velocity is 0.5m/s, the maximum turbulent kinetic energy is 0.03m2 / s ~ 2, which improves the heat transfer effect of shell side.The effects of inner tube arrangement and inlet velocity on shell flow and heat transfer performance were investigated.The simulation results show that the cross arrangement has a higher resistance coefficient, which is about 10% higher than that of the other two kinds of arrangement. Compared with the parallel arrangement, there is a larger radial velocity between the two tubes due to the flow conduction of the winding tube when the misaligned arrangement is adopted.By promoting the mixing of the fluid outside the winding tube and the fluid around the winding tube, the area of the low speed zone behind the tube is greatly reduced, and the PEC index of the enhanced fluid heat transfer is about 25% higher than that of the tube, and the temperature distribution is also more uniform. 3) for the heat exchanger of the new type of water droplet section heat exchanger,Through numerical simulation, the results show that the fluid distribution in the tube is more uniform than that in the conventional round tube, and the distribution of high speed fluid and high temperature fluid is more uniform, which is beneficial to the heat transfer.In the shell side, although the Nusselle number Nu of the water droplet tube heat exchanger decreases to a certain extent, the resistance coefficient f and the pressure drop of the heat exchanger decrease greatly. When the inlet velocity is 0.4m/s,The Nusselle number Nu of the water droplet tube is 94.2g of the circular tube, and its resistance coefficient f only increases the 75 PEC index of the circular tube, which greatly reduces the pressure loss caused by the shell resistance.
【學(xué)位授予單位】：青島科技大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TQ051.5

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