【摘要】：淡水資源的匱乏和能源的緊缺導(dǎo)致利用可再生能源的淡化水技術(shù)越來越受到重視。內(nèi)蒙古地區(qū)水資源天然緊缺,地下水是主要的供水水源,但地下水普遍是含鹽、含氟量較高的苦咸水。因此結(jié)合該地區(qū)太陽能資源豐富的特點(diǎn),設(shè)計(jì)了將太陽能蒸餾系統(tǒng)和水平管降膜蒸發(fā)系統(tǒng)相結(jié)合的新系統(tǒng),為該地區(qū)的淡水供應(yīng)提供一種新的水淡化途徑。水平管降膜蒸發(fā)技術(shù)因存在相變過程具有傳熱溫差小、傳熱系數(shù)高且能夠利用低品位能源的優(yōu)點(diǎn),成為一種節(jié)能型蒸餾淡化技術(shù)。本文通過搭建水平管降膜蒸發(fā)傳熱試驗(yàn)平臺重點(diǎn)研究降膜蒸發(fā)過程。利用搭建的試驗(yàn)平臺,研究噴淋密度、蒸發(fā)溫度、熱流密度等因素對蒸發(fā)量及降膜蒸發(fā)傳熱系數(shù)的影響規(guī)律。研究結(jié)果表明:(1)蒸發(fā)量:在實(shí)驗(yàn)參數(shù)范圍內(nèi),隨著蒸發(fā)溫度的提高、熱流密度的增大,螺旋翅片管束和普通光管管束的單位時間蒸發(fā)量均增加;對于前者,蒸發(fā)溫度為40℃和50℃時,噴淋密度0.060kg/(m·s)時對應(yīng)的單位時間蒸發(fā)量大;蒸發(fā)溫度為60℃和70℃,噴淋密度0.072kg/(m·s)時單位時間蒸發(fā)量大;對于后者,熱流密度在3.91kw/m2~7.69 kw/m2之間時,噴淋密度0.072kg/(m·s)時單位時間蒸發(fā)量大;熱流密度在10.11kw/m2~16.05kw/m2之間時,噴淋密度0.060kg/(m·s)時對應(yīng)的單位時間蒸發(fā)量大。(2)降膜蒸發(fā)傳熱系數(shù):在實(shí)驗(yàn)參數(shù)范圍內(nèi),隨蒸發(fā)溫度的提高,螺旋翅片管和普通光滑圓管的降膜蒸發(fā)傳熱系數(shù)都增大;對于螺旋翅片管,隨著熱流密度的增大,降膜蒸發(fā)傳熱系數(shù)增大,但降膜蒸發(fā)傳熱系數(shù)幾乎不受噴淋密度的影響;對于普通光滑管,熱流密度變化對降膜蒸發(fā)傳熱系數(shù)產(chǎn)生的影響很小;蒸發(fā)溫度為40℃時,降膜蒸發(fā)傳熱系數(shù)隨噴淋密度的變大先變大,后減小;蒸發(fā)溫度為70℃時,降膜蒸發(fā)傳熱系數(shù)隨噴淋密度的變大而略微減小。當(dāng)噴淋密度0.064kg/(m·s)、蒸發(fā)溫度50℃、熱流量193.2W~394W時,螺旋翅片管的降膜蒸發(fā)傳熱系數(shù)大約為普通光滑管的2倍。本文利用Fluent軟件對管外液膜的分布情況進(jìn)行了三維數(shù)值模擬,發(fā)現(xiàn)布液孔的縱向開孔間距影響管外液膜的分布情況。布液孔縱向開孔間距s=8mm時,管外液膜最均勻;s=10mm時,管子中間位置處形成的液膜較均勻,兩端位置處形成的液膜不均勻。在實(shí)際應(yīng)用中,應(yīng)適當(dāng)減小兩端的布液孔縱向間距。研究軸向中間位置處管外的液膜厚度,得到該處的液膜厚度值沿管壁周向角呈先變小后變大的趨勢,但總的變化幅度不大,大約在120°附近,液膜厚度達(dá)到最小值。換熱管上下部分的X方向速度分布和Y方向速度分布基本一致,在管子壁面存在粘性底層。
[Abstract]:The shortage of fresh water and energy makes desalination of renewable energy more and more important. There is a natural shortage of water resources in Inner Mongolia, and groundwater is the main source of water supply, but the groundwater is generally brackish water containing salt and high fluorine content. Therefore, a new system combining solar distillation system and horizontal tube falling film evaporation system is designed to provide a new way for freshwater supply in this area. The horizontal tube falling film evaporation technology is a kind of energy saving distillation desalination technology because of the advantages of small heat transfer temperature difference, high heat transfer coefficient and the ability to make use of low grade energy in the process of phase change. In this paper, the process of falling film evaporation is studied by setting up the experimental platform of falling film evaporation heat transfer in horizontal tube. The effects of spray density, evaporation temperature and heat flux on evaporation rate and heat transfer coefficient of falling film were studied by using the test platform. The results show that: (1) evaporation: in the range of experimental parameters, with the increase of evaporation temperature and heat flux, the evaporation of spiral fin tube bundle and ordinary light tube bundle increase in unit time; For the former, when the evaporation temperature is 40 鈩，

本文編號：2375362