本文關鍵詞： 降膜蒸發(fā) 縱槽管 布膜器 強化傳熱 改進Wilson圖解法　出處：《華東理工大學》2017年碩士論文　論文類型：學位論文

【摘要】：豎管式降膜蒸發(fā)器相比于其他類型的換熱設備具有傳熱系數(shù)高、傳熱溫差損失小、可處理熱敏性物料、易于實現(xiàn)多效操作、結(jié)構(gòu)簡單等優(yōu)點,因此廣泛應用于各類行業(yè)。本文針對腈綸溶劑回收多效蒸發(fā)裝置存在因液體不易成膜且小傳熱溫差下傳熱效率低,并基于節(jié)能減排的目的,旨在開發(fā)出新型高效降膜蒸發(fā)裝置。論文主要工作及成果如下:1.本文開發(fā)出矩形、橢圓形和圓形開口三種類型布膜器,對其最小降液流率進行測量,結(jié)合Hartley所提出的理論公式,優(yōu)選出橢圓形開口布膜器,并利用Nusselt模型和Wilke模型對液膜平均厚度進行計算,最后驗算布液盤液位高度,為降膜流動實驗結(jié)果提供保證。2.對新開發(fā)的縱槽管進行降膜蒸發(fā)傳熱實驗,在熱通量q=13.2-56.52kW/m2,液體周邊進料流量T=0.419-1.112kg/m·s,傳熱溫差△T=2.02-9.87℃時以濃度為19.4%的NaSCN溶液為實驗介質(zhì)進行研究,結(jié)果表明:縱槽管強化傳熱效果在一定范圍內(nèi)隨著管內(nèi)雷諾數(shù)增大而增大;在熱通量相同時,縱槽管的傳熱溫差僅為光管的51%;縱槽管管外冷凝傳熱系數(shù)為光管的約2.07倍,總傳熱系數(shù)為光管的約1.73倍,強化效果顯著。3.根據(jù)改進Wilson圖解法,結(jié)合實驗所測數(shù)據(jù)對縱槽管和普通光管計算結(jié)果進行線性回歸,得到管外冷凝傳熱系數(shù),結(jié)果表明威爾遜圖解法線性回歸關系很好,回歸結(jié)果與實驗所測結(jié)果吻合,說明了實驗數(shù)據(jù)的可靠性。結(jié)合相關傳熱學原理,建立了不銹鋼縱槽管降膜蒸發(fā)傳熱時管外冷凝傳熱的特征關聯(lián)式,為工程應用提供一定的參考。
[Abstract]:The vertical tube falling film evaporator has the advantages of high heat transfer coefficient, small loss of heat transfer temperature difference, easy to realize multi-effect operation, simple structure and so on. Therefore, it is widely used in various industries. In this paper, there is a low heat transfer efficiency due to the liquid is not easy to form film and small heat transfer temperature difference, and based on the purpose of energy saving and emission reduction, the multi-effect evaporator for polyacrylonitrile solvent recovery. The main work and results of this paper are as follows: 1. In this paper, three types of film dispensers, rectangular, elliptical and circular, are developed, and the minimum downflow rate is measured. According to the theoretical formula proposed by Hartley, the elliptical open film distributor is selected, and the average thickness of liquid film is calculated by Nusselt model and Wilke model. Finally, the liquid level height of the liquid plate is checked to guarantee the results of the falling film flow experiment. 2. The heat transfer experiment of falling film evaporation of the newly developed longitudinal groove tube is carried out at the heat flux qn 13.2-56.52 kW / m ~ 2. The liquid circumferential feed flow rate is 0.419-1.112 kg / m 路s. The heat transfer temperature difference between 2. 02 and 9. 87 鈩，

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