本文關(guān)鍵詞： 傾斜管 表面潤濕性 混合蒸汽 協(xié)同作用　出處：《大連理工大學(xué)》2015年碩士論文　論文類型：學(xué)位論文

【摘要】：蒸汽冷凝現(xiàn)象廣泛應(yīng)用于各種工業(yè)生產(chǎn)中,例如空調(diào)系統(tǒng)、制冷技術(shù)、汽車產(chǎn)業(yè)以及很多其他的過程工業(yè)。如何高效能利用能源、強(qiáng)化傳熱的效率,是研究者們長期關(guān)注和研究的問題。一般對(duì)于冷凝傳熱的強(qiáng)化可以從兩個(gè)角度考慮：一是增加擴(kuò)展表面,即對(duì)管的表面作出結(jié)構(gòu)上的變化,常見的有翅片管、螺旋管和波紋管等；二是改變表面潤濕性,通常可以通過處理固體表面來實(shí)現(xiàn),增大蒸汽冷凝液滴在固體壁面上的表觀接觸角,使之形成滴狀冷凝,進(jìn)而強(qiáng)化了固液間的傳熱性能。本文結(jié)合表面改性的方法改變其表面潤濕性,探究傾斜角度和不凝氣對(duì)蒸汽冷凝傳熱的影響,對(duì)不同傾斜角度的管外蒸汽冷凝強(qiáng)化提供一定的參考,為其在工程中的實(shí)際應(yīng)用給予數(shù)據(jù)支持。首先搭建了傾斜管外混合蒸汽冷凝的實(shí)驗(yàn)裝置,并驗(yàn)證實(shí)驗(yàn)系統(tǒng)的熱平衡,利用分子自組裝膜的方法在紫銅管表面制備了十八烷基硫醇疏水表面及經(jīng)過氧化刻蝕的十八烷基硫醇超疏水表面。實(shí)驗(yàn)考察了在純蒸汽和含10%不凝氣的混合蒸汽條件下,不同傾斜角度的疏水和超疏水表面的冷凝流動(dòng)及傳熱特性,實(shí)時(shí)監(jiān)測并采集測試溫度和壓力值,計(jì)算冷凝傳熱數(shù)據(jù),并通過高速攝像儀從不同拍攝位置對(duì)液滴冷凝形態(tài)和流動(dòng)特性進(jìn)行觀測和分析。實(shí)驗(yàn)數(shù)據(jù)顯示：處于銅管不同位置的液滴具有不同程度的接觸角滯后,且影響較大；在含10%不凝氣的混合蒸汽條件下,疏水表面不同位置液滴的接觸角滯后程度均小于純蒸汽條件下；對(duì)于銅管不同的傾斜角度,其接觸角滯后均在一定程度上具有隨著傾斜角度的增大而減小的變化趨勢；在疏水表面條件下,液滴的脫落直徑隨著傾斜角度的增大而減�。辉诔杷砻鏃l件下,液滴的脫落直徑隨著傾斜角度的增大而增大；冷凝液對(duì)超疏水表面的沖刷周期均大于疏水表面,當(dāng)表面潤濕性相同,混合蒸汽條件下的表面沖刷周期均大于純蒸汽條件下的沖刷周期。對(duì)于不同傾斜角度的疏水表面,在相同表面過冷度時(shí),隨著傾斜角度的增大,管外傳熱系數(shù)近似相等,稍有減小的趨勢；對(duì)于純蒸汽超疏水表面,傾斜角度為0。、30。和45。時(shí),其傳熱性能近似相等,在60。時(shí)傳熱性能出現(xiàn)較大值。
[Abstract]:Steam condensation is widely used in various industrial production, such as air conditioning system, refrigeration technology, automobile industry and many other process industries. Generally, the enhancement of condensation heat transfer can be considered from two aspects: one is to increase the expansion surface, that is, to make structural changes on the surface of the tube, and the common one is finned tube. Spiral tube and bellows, etc.; The other is to change the wettability of the surface, which can be realized by treating the solid surface, increasing the apparent contact angle of the steam condensing liquid drop on the solid wall and forming the droplet condensation. Furthermore, the heat transfer performance between solid and liquid is enhanced. In this paper, the surface wettability is changed with the method of surface modification, and the influence of inclined angle and non-condensed gas on the heat transfer of steam condensation is investigated. It provides a certain reference for the outside steam condensation strengthening of different inclined angles, and provides data support for its practical application in engineering. Firstly, an experimental device for condensing mixed steam outside the inclined tube is built. The thermal balance of the experimental system is verified. The hydrophobic surface of 18 alkyl mercaptan and the superhydrophobic surface of 18 alkyl mercaptan etched by oxidation were prepared on the surface of copper tube by molecular self-assembly film. The mixture of pure steam and uncondensed gas containing 10% was investigated experimentally. Steam. The condensing flow and heat transfer characteristics of hydrophobic and superhydrophobic surfaces with different inclined angles were monitored and measured in real time to calculate the condensation heat transfer data. The condensing morphology and flow characteristics of the droplet are observed and analyzed by high-speed camera from different shooting positions. The experimental data show that the droplets in different positions of copper tube have different contact angle lag. And the influence is great; Under the condition of mixed steam containing 10% uncondensed gas, the contact angle hysteresis of droplets at different positions on the hydrophobic surface is lower than that of pure steam. For the different inclined angles of copper tubes, the contact angle lag has the tendency of decreasing with the increase of the inclined angle to a certain extent. Under hydrophobic surface conditions, the drop diameter of droplets decreases with the increase of inclined angle. Under the condition of superhydrophobic surface, the drop diameter of droplets increases with the increase of inclined angle. The scouring period of superhydrophobic surface of condensate is longer than that of hydrophobic surface, and the wettability of superhydrophobic surface is the same. For hydrophobic surfaces with different inclined angles, the surface scour periods under mixed steam conditions are larger than those under pure steam conditions. The heat transfer coefficient outside the tube is approximately equal, with a slight decreasing trend. For the superhydrophobic surface of pure steam, the heat transfer performance of the superhydrophobic surface is approximately equal when the inclination angle is 0.30 and 45.
【學(xué)位授予單位】：大連理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TQ026.2

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