發(fā)布時間：2018-04-11 14:54

  本文選題：干燥過程 + 熱力學分析��； 參考：《蘭州理工大學》2017年碩士論文

【摘要】：干燥是指物料中的水分受熱后以水蒸汽的形式溢出,隨后被流經(jīng)的干燥空氣所攜帶而離開物料系統(tǒng),從而起到了降低物料系統(tǒng)水分的目的。物料受熱時的傳熱過程,以及水蒸汽離開物料系統(tǒng)時的傳質(zhì)過程構(gòu)成了干燥過程中兩個基本的熱力學過程。通過研究干燥過程中傳熱過程與傳質(zhì)過程的基本規(guī)律及其動力學特征,進而揭示干燥過程中傳熱過程與傳質(zhì)過程相互作用機制,即熱濕交叉過程中蘊含的熱力學機制,構(gòu)成了本論文的基本研究內(nèi)容。首先以干燥過程中的熱量守恒定律與質(zhì)量守恒定律為基礎(chǔ),分析了干燥過程中熱量與濕分的傳遞規(guī)律,并以此為依據(jù)分析對比了不同類型干燥設(shè)備效率的高低。基于守恒定律進行干燥過程的分析時,研究對象的選取方式,要根據(jù)分析的側(cè)重點的不同而不同。以控制質(zhì)量的干燥系統(tǒng)為研究對象時,是以干燥設(shè)備幾何尺寸的設(shè)計和干燥工藝條件選定為目的,而以控制容積的干燥系統(tǒng)為研究對象時,是為了便于對干燥過程進行實時的觀測,并能夠根據(jù)變量變化情況及時調(diào)整干燥的工藝條件。其次,對干燥過程傳熱傳濕過程進行了動力學分析。通過對干物料中濕分的性質(zhì)進行研究,揭示了不同干燥階段熱量傳遞與濕分傳遞的動力學特點。研究表明,由于干燥的本質(zhì)是濕分的相變蒸發(fā),因此,濕空氣的受熱相變過程中,溫度隨熵的變化規(guī)律,可以反映物料干燥時傳熱傳濕過程的熱動力學特征。最后通過研究物料干燥系統(tǒng)的熱濕交叉作用,揭示了物料干燥時熱濕交叉作用所蘊含的兩種熱力機制。當傳熱過程與傳濕過程均為自發(fā)過程時,熱濕交叉滿足場協(xié)同機制,這時傳熱過程與傳濕過程相互增強,即傳熱過程的增強可以導致傳濕過程的增強。當傳熱過程為自發(fā)過程,傳濕過程為非自發(fā)過程時,熱濕交叉滿足熱力學耦合機制,傳熱過程的減弱可以強化傳濕過程,即傳濕過程的增強是以傳熱過程的減弱為前提。依據(jù)這兩種熱力學機制,可以在不同的干燥階段通過控制傳熱過程達到最佳的傳濕效果。
[Abstract]:Drying means that the moisture in the material overflows in the form of water vapor after being heated, and then carried by the dry air flowing through it and then leaves the material system, which plays the purpose of reducing the moisture content of the material system.The heat transfer process when the material is heated and the mass transfer process when the water vapor leaves the material system constitute two basic thermodynamic processes in the drying process.By studying the basic laws and dynamic characteristics of heat and mass transfer in drying process, the interaction mechanism of heat and mass transfer in drying process is revealed, that is, the thermodynamic mechanism in the process of heat and moisture intersecting.Constitute the basic research content of this paper.On the basis of heat conservation law and mass conservation law in drying process, the transfer law of heat and moisture content in drying process is analyzed and the efficiency of different drying equipment is analyzed and compared.In the analysis of drying process based on conservation law, the selection method of the research object should be different according to the emphasis of the analysis.When the drying system with controlled quality is taken as the research object, the design of the geometric dimension of the drying equipment and the selection of drying process conditions are taken as the purpose, while the drying system with controlled volume is taken as the research object.It is convenient to observe the drying process in real time and to adjust the drying conditions according to the variation of variables.Secondly, the kinetics of heat and moisture transfer in drying process is analyzed.The dynamic characteristics of heat transfer and wet fraction transfer in dry materials were revealed by studying the properties of moisture content in dry materials.The results show that since the essence of drying is vaporization of wet fraction, the change of temperature with entropy can reflect the thermodynamics of heat and moisture transfer process in drying process of wet air.Finally, by studying the heat and moisture crossover of material drying system, two kinds of thermal mechanism are revealed.When the heat transfer process is a spontaneous process and the moisture transfer process is a non-spontaneous process, the thermodynamics coupling mechanism is satisfied. The weakening of the heat transfer process can strengthen the moisture transfer process, that is, the enhancement of the moisture transfer process is based on the weakening of the heat transfer process.According to these two thermodynamic mechanisms, the optimal moisture transfer effect can be achieved by controlling the heat transfer process in different drying stages.
【學位授予單位】：蘭州理工大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TQ028.67

【參考文獻】

相關(guān)期刊論文 前10條

1 盧小平;俞樹榮;郭丹丹;;從場協(xié)同到熱力學耦合:流動換熱強化的熱力學機制[J];機械工程學報;2015年10期

2 趙延齡;;新型干燥技術(shù)的應(yīng)用及發(fā)展[J];科技資訊;2013年04期

3 史勇春;李捷;李選友;吳茂剛;趙改菊;尹鳳交;;過熱蒸汽干燥技術(shù)的研究進展[J];干燥技術(shù)與設(shè)備;2012年01期

4 盧小平;俞樹榮;;對流換熱場協(xié)同的散度效應(yīng)[J];化工學報;2011年09期

5 王施平;張緒坤;張進疆;;基于LabVIEW的熱泵干燥數(shù)據(jù)采集系統(tǒng)設(shè)計與試驗[J];儀表技術(shù)與傳感器;2011年08期

6 趙芳;陳振乾;施明恒;;胡蘿卜超聲波預(yù)干燥熱濕耦合遷移過程的數(shù)值模擬[J];農(nóng)業(yè)工程學報;2010年11期

7 王施平;張緒坤;張進疆;胡光華;;干燥設(shè)備控制系統(tǒng)現(xiàn)狀與研究進展[J];糧油加工;2010年08期

8 孫京丹;王正順;;紙張干燥系統(tǒng)發(fā)展現(xiàn)狀[J];紙和造紙;2009年04期

9 謝英柏;蘇杭;劉春濤;趙成;;干燥過程的變質(zhì)量熱力學分析[J];農(nóng)機化研究;2009年01期

10 韓光澤;別祥;郭平生;;交叉現(xiàn)象的熱力學機制與傳遞公理[J];廣西師范大學學報(自然科學版);2008年04期

相關(guān)博士學位論文 前1條

1 張緒坤;熱泵干燥熱力學分析及典型物料干燥性能研究[D];中國農(nóng)業(yè)大學;2005年

相關(guān)碩士學位論文 前3條

1 王歡;熱風干燥工藝的特性及節(jié)能研究[D];石家莊鐵道大學;2013年

2 宋蕾娜;熱泵干燥系統(tǒng)的熱力學分析及干燥過程傳熱傳質(zhì)研究[D];華北電力大學（河北）;2007年

3 陶斌斌;多孔介質(zhì)對流干燥傳熱傳質(zhì)機理的研究及其數(shù)值模擬[D];河北工業(yè)大學;2004年

，

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