本文選題：蒸發(fā)器 + 反向循環(huán)��； 參考：《湘潭大學(xué)》2015年碩士論文

【摘要】：蒸發(fā)工藝廣泛用于物料的濃縮、提純等生產(chǎn)過程,是必不可少的高能耗生產(chǎn)工序;在蒸發(fā)濃縮過程中,蒸發(fā)器加熱管非常容易附著大量的結(jié)晶顆粒以及由雜質(zhì)產(chǎn)生的污垢,造成換熱系數(shù)和生產(chǎn)效率降低,嚴(yán)重影響蒸發(fā)設(shè)備的長周期穩(wěn)定進(jìn)行。因此蒸發(fā)設(shè)備的防垢除垢技術(shù)研究具有重要的學(xué)術(shù)價(jià)值和工程應(yīng)用意義�；谡舭l(fā)循環(huán)管內(nèi)汽液兩相流不穩(wěn)定流動(dòng)原理,建立了反向循環(huán)蒸發(fā)條件下的工作螺旋與柔性彈簧組合的往復(fù)螺旋清洗機(jī)構(gòu),通過理論研究、數(shù)值模擬以及實(shí)驗(yàn)研究相結(jié)合方法,研究了往復(fù)螺旋清洗機(jī)構(gòu)對蒸發(fā)過程的影響,主要內(nèi)容如下:(1)為了減小工作螺旋對管內(nèi)流體的阻力,在單管冷模試驗(yàn)臺上對工作螺旋的鋼絲直徑d和螺距P等結(jié)構(gòu)參數(shù)對流動(dòng)阻力進(jìn)行了優(yōu)化試驗(yàn)。試驗(yàn)結(jié)果表明,管內(nèi)工作螺旋的鋼絲直徑d取1.8mm、螺距P大于35mm時(shí)的阻力較小。(2)為了更好地利用循環(huán)管內(nèi)流體不穩(wěn)定性能推動(dòng)工作螺旋往復(fù)運(yùn)動(dòng),建立了單管蒸發(fā)試驗(yàn),并對往復(fù)螺旋清洗機(jī)構(gòu)的柔性彈簧的彈性系數(shù)進(jìn)行了優(yōu)化。單管熱模試驗(yàn)驗(yàn)證了循環(huán)管內(nèi)流體的周期性波動(dòng)推動(dòng)工作螺旋往復(fù)運(yùn)動(dòng)的可行性;在???3000238 mm加熱管中,柔性彈簧彈性系數(shù)為13~16 mN時(shí),工作螺旋可以實(shí)現(xiàn)較好的往復(fù)運(yùn)動(dòng)效果。(3)探索了流體在循環(huán)管內(nèi)形成不穩(wěn)定性流動(dòng)的機(jī)理,進(jìn)一步模擬了流體在循環(huán)內(nèi)的蒸發(fā)過程和氣泡的聚合過程,模擬結(jié)果表明:流體在循環(huán)管內(nèi)的蒸發(fā)過程呈現(xiàn)不均勻性,間歇性產(chǎn)生密集的小氣泡,不同時(shí)間段內(nèi)的氣泡直徑直方圖表明氣泡在循環(huán)管內(nèi)上升的過程中逐漸聚合形成大氣泡,造成管中局部流體壓力的波動(dòng)變化,由此形成不穩(wěn)定的汽液兩相流。(4)為了更加真實(shí)驗(yàn)證柔性彈簧在波動(dòng)流體的作用下的往復(fù)性能,建立了14根換熱管組成的反向循環(huán)蒸發(fā)器的中試試驗(yàn)臺,中試結(jié)果表明:當(dāng)加熱蒸汽溫度為122℃時(shí),工作螺旋的往復(fù)行程達(dá)到了1.2倍螺距以上,滿足反向循環(huán)蒸發(fā)器內(nèi)的均勻清洗要求。并探索加熱蒸汽的溫度、反向循環(huán)管的直徑、上管箱的靜液面高度以及在循環(huán)管內(nèi)插入碎泡器等四個(gè)因素對往復(fù)行程距離的影響,其中加熱蒸汽的溫度和循環(huán)管內(nèi)插入碎泡器兩個(gè)因素起主要作用。(5)以硫酸錳為試驗(yàn)介質(zhì),分別進(jìn)行了工作螺旋外徑以及空管與內(nèi)插螺旋的對比影響試驗(yàn),驗(yàn)證波動(dòng)流體與往復(fù)螺旋相結(jié)合的在線清洗技術(shù)方案在反向循環(huán)蒸發(fā)器內(nèi)的除垢及強(qiáng)化傳熱效果。試驗(yàn)結(jié)果表明:???3000238 mm的加熱管中采用?29mm的工作螺旋除垢效果較好;內(nèi)插往復(fù)螺旋具有較強(qiáng)的除垢和強(qiáng)化傳熱效果,其換熱系數(shù)比空管高出76%。
[Abstract]:Evaporation process is widely used in material concentration, purification and other production processes, it is an essential high energy production process, in the evaporation and concentration process, evaporator heating tube is very easy to adhere to a large number of crystalline particles and dirt produced by impurities. The heat transfer coefficient and production efficiency are reduced, and the long period stability of evaporation equipment is seriously affected. Therefore, the research of scale prevention and scale removal technology of evaporation equipment has important academic value and engineering application significance. Based on the principle of unstable flow of vapor-liquid two-phase flow in evaporative circulation pipe, a reciprocating spiral cleaning mechanism combined with working helix and flexible spring under the condition of reverse circulation evaporation is established. The effects of reciprocating screw cleaning mechanism on the evaporation process are studied by numerical simulation and experimental study. The main contents are as follows: (1) in order to reduce the resistance of the working screw to the fluid in the pipe, The flow resistance of steel wire diameter d and pitch P of working screw was optimized on a single tube cold die test rig. The test results show that the diameter of steel wire in the pipe is 1.8mm, and the resistance is smaller when the pitch P is larger than 35mm.) in order to make better use of the fluid instability in the circulating pipe to promote the reciprocating movement of the working screw, a single pipe evaporation test was established. The elastic coefficient of flexible spring of reciprocating spiral cleaning mechanism is optimized. The experimental results of single tube thermo-model show that the periodic fluctuation of the fluid in the circulating tube can promote the working spiral reciprocating motion, and in the heating pipe of 3000238mm, the elastic coefficient of the flexible spring is 1316mN. The mechanism of the fluid forming instability flow in the circulating tube is explored, and the evaporation process and the bubble polymerization process of the fluid in the circulation are further simulated. The simulation results show that the evaporation process of the fluid in the circulation tube presents inhomogeneity, and the dense small bubbles are produced intermittently. The bubble diameter histogram in different time periods shows that the bubbles gradually converge to form large bubbles in the process of rising in the circulation tube. In order to verify the reciprocating performance of the flexible spring under the action of the fluctuating fluid, the fluctuating pressure of the local fluid in the tube is changed, and the unstable vapor-liquid two-phase flow is formed in order to verify the reciprocation performance of the flexible spring under the action of the fluctuating fluid. A pilot test bench of 14 reverse circulation evaporators composed of heat transfer pipes has been established. The results show that the reciprocating stroke of the working screw is more than 1.2 times when the heating steam temperature is 122 鈩，

本文編號：1827426