疏水性對(duì)微通道流動(dòng)與換熱的影響
發(fā)布時(shí)間：2018-08-27 19:47
【摘要】：在微納米尺度范圍內(nèi),由于通道內(nèi)顯著的表面效應(yīng)和極高的面體比使過高的流動(dòng)阻力成為微納米系統(tǒng)應(yīng)用中難以解決的瓶頸問題。因此,探求可靠有效的減阻方法無疑具有重要的工程價(jià)值。目前針對(duì)微肋片內(nèi)部流動(dòng)的研究以及超疏水表面通道減阻的研究較多,但針對(duì)微管和微柱群內(nèi)部疏水表面減阻的研究,尤其微柱群內(nèi)部表面不同接觸角與微柱內(nèi)部流動(dòng)減阻關(guān)系的研究還很少。文章首先系統(tǒng)論述了疏水性薄膜和疏水性微通道的制備方法,并對(duì)去離子水流經(jīng)疏水性微管的流動(dòng)減阻特性進(jìn)行實(shí)驗(yàn)研究。同時(shí),對(duì)去離子水橫掠微針肋陣列熱沉的流動(dòng)和換熱特性進(jìn)行了系統(tǒng)分析。概括起來,本論文主要研究?jī)?nèi)容以及結(jié)論如下：(1)開展了超疏水性微管的制備以及微通道內(nèi)減阻規(guī)律的研究。首先在改性有機(jī)硅稀溶液中加入2%全氟辛基氟硅烷以及添加劑配制超疏水液,采用滴定法在內(nèi)徑分別為0.447mm、0.728mm和0.873mm的三種微銅管內(nèi)壁涂覆微米級(jí)超疏水性涂層,可使其水滴表觀接觸角超過150。。同時(shí)建立微管內(nèi)流動(dòng)特性實(shí)驗(yàn)系統(tǒng)并對(duì)超疏水性處理的減阻規(guī)律進(jìn)行了系統(tǒng)研究,分別測(cè)量了Reynolds數(shù)在100-3000范圍內(nèi),去離子水流經(jīng)疏水處理前后微銅管的內(nèi)部摩擦阻力系數(shù)f。研究表明,對(duì)微管內(nèi)壁面的超疏水性處理顯著降低了微管內(nèi)的流動(dòng)阻力,且影響隨微管內(nèi)徑的增加而增大,實(shí)驗(yàn)范圍內(nèi)流動(dòng)阻力系數(shù)最大降幅可達(dá)29.08%；超疏水涂層使得微管內(nèi)的流動(dòng)轉(zhuǎn)捩現(xiàn)象出現(xiàn)滯后,且轉(zhuǎn)捩Re隨微管管徑增加而略有增大。(2)開展了疏水性微針肋熱沉的制備以及疏水性對(duì)微針肋熱沉流動(dòng)特性影響的研究。采用向改性有機(jī)硅稀溶液中加入2%全氟辛基氟硅烷以及微納米粒子的方法制備疏水液,并通過改變微納米粒子添加量調(diào)控疏水涂層的表觀接觸角,可分別制取接觸角為99.5。、119.5。和151.5。(水為工質(zhì))的疏水表面。并通過實(shí)驗(yàn)測(cè)試了微針肋陣列熱沉的流動(dòng)阻力和壓力降。結(jié)果表明,相同雷諾數(shù)(Re)下流道內(nèi)摩擦因子(f)比疏水處理前有明顯下降,主要是由于疏水性界面的張力作用所致；相同Re下,接觸角越大,疏水涂層雙重結(jié)構(gòu)中微納米突起間距越小,去離子水與空氣接觸面增大,使得摩擦阻力減小；隨Re增加,三種涂層實(shí)驗(yàn)段內(nèi)的減阻率均不斷降低。(3)開展了疏水性對(duì)微針肋陣列熱沉的換熱特性影響的研究。對(duì)接觸角分別為83。、99.5。、119.50和151.50的橢圓形微肋陣傳熱特性進(jìn)行實(shí)驗(yàn)研究,結(jié)果表明：加熱功率為100w時(shí),較小的流量下,流量的改變對(duì)其底板表面溫度影響較大,在較大流量時(shí),流量改變對(duì)其影響較�。浑S著接觸角的增大,相同Re下對(duì)流換熱系數(shù)減�。徊煌佑|角橢圓形微針肋熱沉的Nu均隨著Re的增大而增大；接觸角越大導(dǎo)致工質(zhì)與壁面接觸越差,換熱效果變差。三種涂層實(shí)驗(yàn)段內(nèi)的減阻率均優(yōu)于對(duì)換熱效果的影響。本文對(duì)去離子水流經(jīng)疏水性微管的流動(dòng)減阻特性進(jìn)行實(shí)驗(yàn)研究。同時(shí),對(duì)去離子水橫掠微針肋陣列熱沉的流動(dòng)和換熱特性進(jìn)行了系統(tǒng)分析。驗(yàn)證了疏水性涂層在微通道內(nèi)應(yīng)用的可行性,發(fā)展了一種微通道內(nèi)減阻新方法,相關(guān)研究成果為微通道減阻提供了理論支撐和技術(shù)支持,是對(duì)現(xiàn)有現(xiàn)有微通道內(nèi)流動(dòng)與換熱研究的有效補(bǔ)充與完善。
[Abstract]:In the micro-nano scale, because of the remarkable surface effect in the channel and the extremely high surface ratio, the excessive flow resistance becomes the bottleneck problem which is difficult to solve in the application of micro-nano systems. Therefore, it is undoubtedly of great engineering value to explore reliable and effective drag reduction methods. There are many researches on the drag reduction of surface channels, but there are few researches on the drag reduction of hydrophobic surfaces in micro-tubes and micro-columns, especially on the relationship between the different contact angles of the inner surface of micro-columns and the drag reduction of the inner flow of micro-columns. The flow and heat transfer characteristics of microneedle-fin array heat sink swept by deionized water are systematically analyzed. In summary, the main contents and conclusions of this paper are as follows: (1) The preparation of superhydrophobic microtubules and the drag reduction in microchannels are studied. The super-hydrophobic liquid was prepared by adding 2% perfluorooctyl fluorosilane and additives into the dilute solution of organosilicon. The super-hydrophobic coatings were coated on the inner walls of three kinds of micro-copper tubes with inner diameters of 0.447 mm, 0.728 mm and 0.873 mm respectively by titration method. The apparent contact angle of water droplets exceeded 150%. The drag reduction law of water treatment was systematically studied. The internal friction coefficient f of micro-copper tube was measured before and after deionized water treatment in the range of Reynolds number 100-3000. The results showed that the superhydrophobic treatment of the inner surface of micro-tube significantly reduced the flow resistance in micro-tube, and the effect increased with the diameter of micro-tube. With the increase of the diameter of the microtubule, the maximum decrease of the flow resistance coefficient was 29.08%. The superhydrophobic coating delayed the flow transition in the microtubule, and the transition Re increased slightly with the increase of the diameter of the microtubule. (2) The preparation of hydrophobic microneedle fin heat sink and the effect of hydrophobicity on the flow characteristics of microneedle fin heat sink were studied. Hydrophobic solution was prepared by adding 2% perfluorooctyl fluorosilane and micro-nano-particles into dilute organic silicon solution. The hydrophobic surfaces with contact angles of 99.5, 119.5 and 151.5. (water as working fluid) were prepared by adjusting the amount of micro-nano-particles and adjusting the apparent contact angle of hydrophobic coatings. The results show that the friction factor (f) in the runner with the same Reynolds number (Re) decreases significantly compared with that before the hydrophobic treatment, mainly due to the tension effect of the hydrophobic interface; the larger the contact angle, the smaller the nano-and micro-bulge spacing in the double structure of the hydrophobic coating, and the larger the contact surface between deionized water and air. The friction resistance decreases and the drag reduction rate decreases with the increase of Re. (3) The influence of hydrophobicity on the heat transfer characteristics of microneedle fin array heat sinks is studied. The heat transfer characteristics of elliptical microfin array with contact angles of 83., 99.5., 119.50 and 151.50 are studied experimentally. The results show that the heating power is 100w. When the contact angle increases, the convective heat transfer coefficient decreases at the same Re; when the contact angle increases, the heat sink of elliptical micro-needle fins with different contact angles increases with the increase of Re; when the contact angle increases, the heat sink of working medium and wall increases with the increase of Re; when the contact angle increases, the heat sink of the elliptical micro-needle fin increases with the increase of Re; The worse the contact, the worse the heat transfer effect. The drag reduction rate of the three coatings is better than that of the heat transfer effect. In this paper, the drag reduction characteristics of deionized water flowing through hydrophobic microtubules are studied experimentally. The feasibility of coating application in microchannels has led to the development of a new method for drag reduction in microchannels. Relevant research results provide theoretical and technical support for drag reduction in microchannels, and are an effective complement to the existing research on flow and heat transfer in microchannels.
【學(xué)位授予單位】：南京師范大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TK124
本文編號(hào)：2208275
[Abstract]:In the micro-nano scale, because of the remarkable surface effect in the channel and the extremely high surface ratio, the excessive flow resistance becomes the bottleneck problem which is difficult to solve in the application of micro-nano systems. Therefore, it is undoubtedly of great engineering value to explore reliable and effective drag reduction methods. There are many researches on the drag reduction of surface channels, but there are few researches on the drag reduction of hydrophobic surfaces in micro-tubes and micro-columns, especially on the relationship between the different contact angles of the inner surface of micro-columns and the drag reduction of the inner flow of micro-columns. The flow and heat transfer characteristics of microneedle-fin array heat sink swept by deionized water are systematically analyzed. In summary, the main contents and conclusions of this paper are as follows: (1) The preparation of superhydrophobic microtubules and the drag reduction in microchannels are studied. The super-hydrophobic liquid was prepared by adding 2% perfluorooctyl fluorosilane and additives into the dilute solution of organosilicon. The super-hydrophobic coatings were coated on the inner walls of three kinds of micro-copper tubes with inner diameters of 0.447 mm, 0.728 mm and 0.873 mm respectively by titration method. The apparent contact angle of water droplets exceeded 150%. The drag reduction law of water treatment was systematically studied. The internal friction coefficient f of micro-copper tube was measured before and after deionized water treatment in the range of Reynolds number 100-3000. The results showed that the superhydrophobic treatment of the inner surface of micro-tube significantly reduced the flow resistance in micro-tube, and the effect increased with the diameter of micro-tube. With the increase of the diameter of the microtubule, the maximum decrease of the flow resistance coefficient was 29.08%. The superhydrophobic coating delayed the flow transition in the microtubule, and the transition Re increased slightly with the increase of the diameter of the microtubule. (2) The preparation of hydrophobic microneedle fin heat sink and the effect of hydrophobicity on the flow characteristics of microneedle fin heat sink were studied. Hydrophobic solution was prepared by adding 2% perfluorooctyl fluorosilane and micro-nano-particles into dilute organic silicon solution. The hydrophobic surfaces with contact angles of 99.5, 119.5 and 151.5. (water as working fluid) were prepared by adjusting the amount of micro-nano-particles and adjusting the apparent contact angle of hydrophobic coatings. The results show that the friction factor (f) in the runner with the same Reynolds number (Re) decreases significantly compared with that before the hydrophobic treatment, mainly due to the tension effect of the hydrophobic interface; the larger the contact angle, the smaller the nano-and micro-bulge spacing in the double structure of the hydrophobic coating, and the larger the contact surface between deionized water and air. The friction resistance decreases and the drag reduction rate decreases with the increase of Re. (3) The influence of hydrophobicity on the heat transfer characteristics of microneedle fin array heat sinks is studied. The heat transfer characteristics of elliptical microfin array with contact angles of 83., 99.5., 119.50 and 151.50 are studied experimentally. The results show that the heating power is 100w. When the contact angle increases, the convective heat transfer coefficient decreases at the same Re; when the contact angle increases, the heat sink of elliptical micro-needle fins with different contact angles increases with the increase of Re; when the contact angle increases, the heat sink of working medium and wall increases with the increase of Re; when the contact angle increases, the heat sink of the elliptical micro-needle fin increases with the increase of Re; The worse the contact, the worse the heat transfer effect. The drag reduction rate of the three coatings is better than that of the heat transfer effect. In this paper, the drag reduction characteristics of deionized water flowing through hydrophobic microtubules are studied experimentally. The feasibility of coating application in microchannels has led to the development of a new method for drag reduction in microchannels. Relevant research results provide theoretical and technical support for drag reduction in microchannels, and are an effective complement to the existing research on flow and heat transfer in microchannels.
【學(xué)位授予單位】：南京師范大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TK124
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