本文選題：熔融硅　切入點(diǎn)：熱毛細(xì)　出處：《江蘇大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：近幾十年來,隨著世界經(jīng)濟(jì)和人口數(shù)量的迅速增長,能源短缺和環(huán)境污染問題日益嚴(yán)重,大力開發(fā)清潔能源成為各國保護(hù)生態(tài)環(huán)境、保持經(jīng)濟(jì)可持續(xù)發(fā)展的重要舉措。太陽能電池以其清潔、安全、高效率等優(yōu)點(diǎn)得到了國家大力扶持。硅帶技術(shù)(水平拉膜制備技術(shù))憑借其制備流程簡單、提拉速率高、原材料損耗少等優(yōu)點(diǎn)引發(fā)了人們的廣泛關(guān)注。水平拉膜制備過程其實(shí)就是熔融硅水平固化和水平流動的綜合過程。為了使橫向拉膜技術(shù)獲得更穩(wěn)定的生長環(huán)境,能夠制備質(zhì)量高、厚度準(zhǔn)確可控的硅帶,本論文使用數(shù)值模擬方法對熱毛細(xì)效應(yīng)下硅熔體水平固化以及水平流動過程進(jìn)行系統(tǒng)研究。首先,介紹了數(shù)值模擬基本方法、凝固過程傳熱計(jì)算理論、凝固過程流場計(jì)算理論、熱毛細(xì)對流數(shù)值模擬理論,為數(shù)值模擬提供理論基礎(chǔ)。然后,在Fluent模擬軟件里建立了熱毛細(xì)作用下熔融硅水平流動物理模型和數(shù)學(xué)模型�？紤]了熔融硅在水平溫度梯度Ma、液池底部垂直熱流密度Q和兩種情況耦合效應(yīng)下水平流動模擬分析。得到了液層內(nèi)流場和溫度場的分布云圖。深入分析了水平溫差Ma、底部熱流密度Q、及兩種情況耦合作用下各種流型的變化規(guī)律。研究結(jié)果表明,當(dāng)液池底部熱流密度Q為零時(shí),且兩側(cè)溫差Ma較小時(shí),熔體流動為穩(wěn)態(tài)流動,隨著兩側(cè)溫度差Ma的不斷增大,矩形液池內(nèi)流動逐漸由穩(wěn)態(tài)轉(zhuǎn)變?yōu)椴▌釉俅无D(zhuǎn)變?yōu)橛蓛蓚�(gè)旋轉(zhuǎn)方向相反的且大小不同非對稱雙胞流動,最后流動轉(zhuǎn)型為紊亂流動狀態(tài);當(dāng)兩側(cè)溫度差Ma較小時(shí),底部熱流密度Q對熔融硅水平流動作用明顯,隨著底部熱流密度Q的不斷增大流體由穩(wěn)態(tài)轉(zhuǎn)變?yōu)橛啥鄠�(gè)旋轉(zhuǎn)方向交替相反的漩渦流胞,并且流動構(gòu)型隨著熱流密度Q的增加沒有發(fā)生明顯變化;當(dāng)水平溫差Ma和垂直熱流密度Q耦合作用時(shí),流動構(gòu)型和僅僅施加垂直熱流密度Q接近,較小的熱流密度對熱毛細(xì)對流有抑制作用。最后在COMSOL數(shù)值分析軟件中建立了水平管道狀凝固模型,采用自適應(yīng)網(wǎng)格劃分法劃分網(wǎng)格,并且使用顯熱容法求解高度非線性方程。對熔融硅在溫度場和流場耦合作用下水平固化過程進(jìn)行數(shù)值模擬,模擬結(jié)果顯示:熔融硅在水平凝固過程中產(chǎn)生了相變。并且通過等效熱容的數(shù)學(xué)分析方法計(jì)算了在相變過程中型速度場分布、等溫線分布。結(jié)果還發(fā)現(xiàn):在靠坩堝口附近形成了流線型渦旋流。并且在凝固區(qū)和結(jié)晶區(qū)出現(xiàn)了很明顯的熱流密度變大現(xiàn)象,結(jié)晶結(jié)束后熱流密度慢慢消失。
[Abstract]:In recent decades, with the rapid growth of world economy and population, the problem of energy shortage and environmental pollution is becoming more and more serious. Solar cells have been greatly supported by the state because of their advantages of cleanness, safety and high efficiency. Silicon tape technology (horizontal film drawing technology) is characterized by its simple preparation process and high drawing rate. The advantages of low loss of raw materials have aroused widespread concern. The preparation process of horizontal film drawing is in fact a comprehensive process of horizontal solidification and horizontal flow of molten silicon. In order to obtain a more stable growth environment for transverse film drawing technology, The silicon tape with high quality and controllable thickness can be prepared. In this paper, the horizontal solidification and horizontal flow process of silicon melt under the effect of thermal capillary are studied systematically by numerical simulation method. Firstly, the basic method of numerical simulation is introduced. The theory of heat transfer calculation in solidification process, the theory of flow field calculation in solidification process, and the numerical simulation theory of thermal capillary convection provide the theoretical basis for numerical simulation. A physical model and a mathematical model for the horizontal flow of molten silicon under the action of thermal capillary are established in Fluent software. The horizontal effect of the melt silicon is considered under the horizontal temperature gradient, the vertical heat flux Q at the bottom of the liquid tank and the coupling effect between the two conditions. Flow simulation analysis. The distribution of flow field and temperature field in liquid layer is obtained. The horizontal temperature difference Ma, the bottom heat flux Q, and the variation law of various flow patterns under the coupling of the two conditions are analyzed in depth. When the heat flux Q at the bottom of the tank is 00:00, and the temperature difference between the two sides is small, the melt flow is steady flow, and with the increase of the temperature difference Ma on both sides, The flow in the rectangular liquid cell gradually changed from steady state to fluctuation and then changed from two asymmetric double cell flows with opposite rotating directions and different sizes, finally the flow changed into a turbulent flow state, when the temperature difference between two sides was small, The effect of bottom heat flux Q on the horizontal flow of molten silicon is obvious. With the increasing of bottom heat flux Q, the fluid changes from steady state to swirl cell, which is alternately opposite from several rotating directions. When the horizontal temperature difference Ma is coupled with the vertical heat flux Q, the flow configuration is close to that of only applying the vertical heat flux Q, and the flow configuration does not change obviously with the increase of the heat flux Q, and when the horizontal temperature difference Ma is coupled with the vertical heat flux Q, the flow configuration is close to the vertical heat flux. The small heat flux can restrain the convection of the heat capillary. Finally, the horizontal pipe solidification model is established in the COMSOL numerical analysis software, and the adaptive meshing method is used to mesh the convection. The highly nonlinear equation is solved by the sensible heat capacity method. The horizontal solidification process of molten silicon under the coupling of temperature field and flow field is numerically simulated. The simulation results show that the phase transition occurs during the horizontal solidification of molten silicon, and the distribution of medium velocity field in the process of phase transformation is calculated by the mathematical analysis method of equivalent heat capacity. It is also found that a streamline vortex flow is formed near the crucible entrance, and the heat flux increases obviously in the solidification and crystallization regions, and the heat flux slowly disappears after crystallization.
【學(xué)位授予單位】：江蘇大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TN304.12;TM914.4

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