本文選題：干燥過(guò)程 + 熱力學(xué)分析��； 參考：《蘭州理工大學(xué)》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(kāi)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(shí)的傳熱過(guò)程,以及水蒸汽離開(kāi)物料系統(tǒng)時(shí)的傳質(zhì)過(guò)程構(gòu)成了干燥過(guò)程中兩個(gè)基本的熱力學(xué)過(guò)程。通過(guò)研究干燥過(guò)程中傳熱過(guò)程與傳質(zhì)過(guò)程的基本規(guī)律及其動(dòng)力學(xué)特征,進(jìn)而揭示干燥過(guò)程中傳熱過(guò)程與傳質(zhì)過(guò)程相互作用機(jī)制,即熱濕交叉過(guò)程中蘊(yùn)含的熱力學(xué)機(jī)制,構(gòu)成了本論文的基本研究?jī)?nèi)容。首先以干燥過(guò)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(guò)程中熱量與濕分的傳遞規(guī)律,并以此為依據(jù)分析對(duì)比了不同類(lèi)型干燥設(shè)備效率的高低�；谑睾愣蛇M(jìn)行干燥過(guò)程的分析時(shí),研究對(duì)象的選取方式,要根據(jù)分析的側(cè)重點(diǎn)的不同而不同。以控制質(zhì)量的干燥系統(tǒng)為研究對(duì)象時(shí),是以干燥設(shè)備幾何尺寸的設(shè)計(jì)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(duì)象時(shí),是為了便于對(duì)干燥過(guò)程進(jìn)行實(shí)時(shí)的觀測(cè),并能夠根據(jù)變量變化情況及時(shí)調(diào)整干燥的工藝條件。其次,對(duì)干燥過(guò)程傳熱傳濕過(guò)程進(jìn)行了動(dòng)力學(xué)分析。通過(guò)對(duì)干物料中濕分的性質(zhì)進(jìn)行研究,揭示了不同干燥階段熱量傳遞與濕分傳遞的動(dòng)力學(xué)特點(diǎn)。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(guò)程中,溫度隨熵的變化規(guī)律,可以反映物料干燥時(shí)傳熱傳濕過(guò)程的熱動(dòng)力學(xué)特征。最后通過(guò)研究物料干燥系統(tǒng)的熱濕交叉作用,揭示了物料干燥時(shí)熱濕交叉作用所蘊(yùn)含的兩種熱力機(jī)制。當(dāng)傳熱過(guò)程與傳濕過(guò)程均為自發(fā)過(guò)程時(shí),熱濕交叉滿(mǎn)足場(chǎng)協(xié)同機(jī)制,這時(shí)傳熱過(guò)程與傳濕過(guò)程相互增強(qiáng),即傳熱過(guò)程的增強(qiáng)可以導(dǎo)致傳濕過(guò)程的增強(qiáng)。當(dāng)傳熱過(guò)程為自發(fā)過(guò)程,傳濕過(guò)程為非自發(fā)過(guò)程時(shí),熱濕交叉滿(mǎn)足熱力學(xué)耦合機(jī)制,傳熱過(guò)程的減弱可以強(qiáng)化傳濕過(guò)程,即傳濕過(guò)程的增強(qiáng)是以傳熱過(guò)程的減弱為前提。依據(jù)這兩種熱力學(xué)機(jī)制,可以在不同的干燥階段通過(guò)控制傳熱過(guò)程達(dá)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(xué)位授予單位】：蘭州理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類(lèi)號(hào)】：TQ028.67

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