本文選題：水平管降膜蒸發(fā)器　切入點(diǎn)：鋁管　出處：《大連理工大學(xué)》2014年碩士論文

【摘要】：由于低溫多效蒸發(fā)海水淡化技術(shù)有著產(chǎn)品水的水質(zhì)好、可靠性高、傳熱溫差小等諸多優(yōu)點(diǎn),現(xiàn)已得到非常廣泛的應(yīng)用。但此方法的一次投資成本較高,嚴(yán)重制約了其進(jìn)一步發(fā)展。采用鋁管來代替蒸發(fā)器中的銅管可以有效地降低成本,但鋁管在海水環(huán)境中的腐蝕問題一直以來都在困擾著它在實(shí)際工程中的應(yīng)用,對(duì)其腐蝕機(jī)理進(jìn)行深入研究是解決鋁管在海水中腐蝕問題的首要條件。 本論文設(shè)計(jì)和搭建了水平管降膜蒸發(fā)實(shí)驗(yàn)臺(tái),首先使用天然海水作為腐蝕介質(zhì),在水平管降膜蒸發(fā)器中對(duì)鋁管進(jìn)行了腐蝕實(shí)驗(yàn),總結(jié)了鋁管表面腐蝕形貌變化規(guī)律并確定了對(duì)鋁管的腐蝕影響較大的因素；為了探究鹽度對(duì)鋁管在水平管降膜蒸發(fā)器中腐蝕的影響,使用蒸發(fā)濃縮后的海水作為腐蝕介質(zhì),在水平管降膜蒸發(fā)器中對(duì)鋁管進(jìn)行了腐蝕實(shí)驗(yàn),總結(jié)了鋁管表面腐蝕形貌變化規(guī)律并與之前的海水腐蝕實(shí)驗(yàn)進(jìn)行了對(duì)比。 實(shí)驗(yàn)結(jié)果表明,在水平管降膜蒸發(fā)器中,由于其特殊的溫度和壓力環(huán)境,使得鋁管容易遭受空泡腐蝕。鋁管在蒸發(fā)器中使用一段時(shí)間后會(huì)被腐蝕,腐蝕的主要形態(tài)為孔蝕。在本實(shí)驗(yàn)工況下,選用鹽度為2.9%的天然海水作為腐蝕介質(zhì)時(shí),鋁管開始發(fā)生孔蝕的時(shí)間為腐蝕實(shí)驗(yàn)進(jìn)行的第38個(gè)小時(shí)左右,鋁管在水平管降膜蒸發(fā)器中開始發(fā)生孔蝕時(shí),其初期的腐蝕速率較大,隨著腐蝕的進(jìn)行和腐蝕產(chǎn)物的積累,其腐蝕速率逐漸減小,腐蝕產(chǎn)物在初期對(duì)鋁管的腐蝕起到了促進(jìn)作用,在后期對(duì)腐蝕的發(fā)展起到了抑制作用；當(dāng)選用蒸發(fā)濃縮后的海水作為腐蝕介質(zhì),海水的鹽度為6%,鋁管開始發(fā)生孔蝕的時(shí)間為實(shí)驗(yàn)進(jìn)行的第6個(gè)小時(shí)左右,鋁管發(fā)生孔蝕時(shí),相對(duì)于天然海水沖刷腐蝕作用下的鋁管來說,其表面的腐蝕孔直徑更大,腐蝕孔直徑增大使得腐蝕產(chǎn)物難以完全覆蓋整個(gè)腐蝕孔,故腐蝕產(chǎn)物對(duì)鋁管的保護(hù)作用被削弱,這就使蒸發(fā)濃縮后的海水對(duì)鋁管表面有著持續(xù)的破壞能力。 將鋁管應(yīng)用于水平管降膜蒸發(fā)器中時(shí),應(yīng)盡量通過減少蒸發(fā)器中氣泡的產(chǎn)生、降低海水鹽度等方法來抑制鋁管表面的腐蝕,根據(jù)鋁管發(fā)生孔蝕的具體時(shí)間做好相應(yīng)的準(zhǔn)備工作。
[Abstract]:Due to the advantages of low temperature and multi-effect evaporation desalination, such as good water quality, high reliability, low heat transfer temperature difference and so on, it has been widely used.However, the primary investment cost of this method is high, which seriously restricts its further development.Using aluminum tube instead of copper tube in evaporator can reduce the cost effectively, but the corrosion problem of aluminum tube in seawater environment has been puzzling its application in practical engineering.It is the most important condition to study the corrosion mechanism of aluminum pipe in seawater.In this paper, a horizontal tube falling film evaporator is designed and built. Firstly, using natural seawater as corrosion medium, the corrosion experiment of aluminum tube is carried out in the horizontal tube falling film evaporator.In order to explore the effect of salinity on corrosion of aluminum tube in horizontal tube falling film evaporator, the evaporated concentrated seawater is used as corrosion medium.The corrosion experiments of aluminum tubes were carried out in a horizontal tube falling film evaporator. The surface corrosion morphology of aluminum tubes was summarized and compared with the previous seawater corrosion experiments.The experimental results show that aluminum tubes are vulnerable to cavitation corrosion due to their special temperature and pressure environment in the horizontal tube falling film evaporator.Aluminum tubes will be corroded after being used in evaporator for a period of time, the main form of corrosion is pitting.Under the experimental condition, when the natural seawater with a salinity of 2.9% is selected as the corrosion medium, the time when the pitting corrosion of the aluminum tube begins is about 38 hours of the corrosion experiment, and the pitting corrosion of the aluminum tube begins in the horizontal tube falling film evaporator.The corrosion rate decreases gradually with the development of corrosion and the accumulation of corrosion products. The corrosion products promote the corrosion of aluminum tubes in the initial stage and inhibit the development of corrosion in the later stage.When the evaporated and concentrated seawater is used as the corrosion medium, the salinity of seawater is 6 and the time when the pitting corrosion of the aluminum tube begins is about 6 hours after the experiment, when the pitting corrosion of the aluminum tube occurs,Compared with the aluminum tube subjected to natural seawater erosion, the diameter of corrosion hole on the surface of aluminum pipe is larger, and the corrosion product is difficult to cover the whole corrosion hole completely, so the protective effect of corrosion product on aluminum tube is weakened.This makes evaporated and concentrated seawater to the surface of the aluminum tube has continued damage.When the aluminum tube is applied to the horizontal tube falling film evaporator, the corrosion of the aluminum tube surface should be restrained by reducing the bubble in the evaporator and reducing the salinity of the seawater, and the corresponding preparation work should be made according to the specific time of the pitting corrosion of the aluminum tube.
【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】：2014
【分類號(hào)】：P747

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