大顆粒流態(tài)化特性與熱量傳遞協(xié)同作用的研究
發(fā)布時間：2019-02-26 11:59
【摘要】：本文選用粒徑在0.1mm~0.5mm范圍內(nèi)的玻璃微珠代替多晶硅生產(chǎn)中的硅晶種顆粒作為實驗物料,使用熱頻率響應實驗方法研究了顆粒與流體間的傳熱特性�？疾炝祟w粒粒度、流化氣速及床層空隙率對傳熱的影響,由測定的17組顆粒與流體間的傳熱系數(shù)與流化床流動特性、流體物性相結(jié)合回歸出傳熱關(guān)聯(lián)式。將實驗得到的傳熱關(guān)聯(lián)式應用于Fluent中,模擬了氣固非穩(wěn)態(tài)傳熱過程;模擬結(jié)果與Guun傳熱模型的模擬結(jié)果及實驗結(jié)果進行了比較。考察了流化床內(nèi)置垂直加熱棒對流化質(zhì)量及床內(nèi)傳熱特性的影響。具體研究內(nèi)容如下:1、搭建了一套用于研究氣固流化床傳熱特性的實驗裝置,流化床直徑0.16m,高1.3m。溫度控制系統(tǒng)可以輸出幅值5≤A≤10℃、周期T≥90s的正弦式氣溫變化,使用K型熱電偶采集氣體溫度,溫度采集的頻率為5次/秒。Set1-Set3為窄篩分顆粒,Set4、Set5為寬篩分顆粒;局部顆粒體積分數(shù)采用抽樣法測得,壓力變化采用U型壓差計測定。2、入口處溫度脈沖參數(shù)的變化對顆粒與流體間傳熱系數(shù)的測量并沒有影響,誤差主要為熱電偶在測量過程中產(chǎn)生的。顆粒粒徑及流化氣速是影響顆粒與流體間的傳熱主要因素,顆粒粒徑越大、流化氣速越高顆粒與流體間的傳熱系數(shù)越大。本文得出的顆粒與流體間的傳熱系數(shù)與文獻結(jié)果相同,但比經(jīng)驗關(guān)聯(lián)式的計算值大10倍左右,回歸得到了顆粒雷諾數(shù)在1≤Rep≤11范圍內(nèi)的傳熱關(guān)聯(lián)式:0.648 1/2 0.33Nu3.37 Re?Pr-(28)?,關(guān)聯(lián)式的給出值與實驗值的誤差在15%以內(nèi),滿足工程計算的精度要求。3、模擬了氣固非穩(wěn)態(tài)傳熱過程,顆粒的徑向及軸向顆粒體積分數(shù)分布及床層的高度與實驗測量值基本吻合;分析顆粒的瞬時速度矢量表明,流化床內(nèi)存在由中心向兩側(cè)總體的顆粒循環(huán)運動及局部的渦流;顆粒與流體間的熱量傳遞主要發(fā)生在流化床入口很小的區(qū)域內(nèi),床層其他區(qū)域內(nèi)顆粒與氣體的溫度基本一致;User-defined傳熱模型的顆粒升溫曲線與實驗結(jié)果基本相同,Guun傳熱模型模擬的顆粒升溫曲線略小于實驗結(jié)果;分析氣體瞬時氣速與顆粒瞬時溫度之間的關(guān)系發(fā)現(xiàn),流化床入口處顆粒的溫度與氣體速度成正比,即與顆粒雷諾數(shù)成正比,顆粒雷諾數(shù)對氣固傳熱過程起著重要作用。4、模擬流化床內(nèi)加載垂直加熱棒過程中發(fā)現(xiàn),氣泡主要沿著壁面產(chǎn)生,內(nèi)構(gòu)件起到破碎氣泡及提高床層中心處的固含量的作用,使床層的顆粒分布更加均勻。對比添加內(nèi)構(gòu)件前后固定位置點氣體壓力變化發(fā)現(xiàn),添加內(nèi)購件氣泡破碎頻率沒有明顯改變,但氣泡的尺寸減小,添加內(nèi)構(gòu)件提高了流化質(zhì)量。氣體與顆粒的熱量交換主要發(fā)生在流化床入口很小域內(nèi),熱交換區(qū)域氣體與顆粒的溫度與氣速密切相關(guān),氣速越大傳熱效率越高。添加內(nèi)構(gòu)件后并沒有改變流化床內(nèi)整體的氣體與顆粒的溫度分布,但內(nèi)置加熱棒的加熱形式明顯降低了流化床壁面溫度,在多晶硅生產(chǎn)中可以有效減少壁面沉積。
[Abstract]:In this paper, the heat transfer characteristics between the particles and the fluid were studied by using the method of thermal frequency response in the use of glass beads in the range of 0. 1 mm to 0. 5 mm instead of the silicon seed particles in the polycrystalline silicon production as experimental materials. The effect of the particle size, the fluidizing gas velocity and the void ratio of the bed layer on the heat transfer was investigated. The heat transfer coefficient between the 17 particles and the fluid and the flow characteristics of the fluidized bed and the physical properties of the fluid were combined to get the heat transfer correlation. The heat transfer associated with the experiment is applied to Fluent, and the process of gas-solid unsteady heat transfer is simulated. The simulation results are compared with the simulation results of the Gujun heat transfer model and the experimental results. The convection quality of the built-in vertical heating rod in the fluidized bed and the effect of the heat transfer in the bed were investigated. The specific research contents are as follows: 1. A set of experimental equipment for studying the heat transfer characteristics of the gas-solid fluidized bed is set up. The diameter of the fluidized bed is 0.16m and the height is 1.3m. The temperature control system can output a sinusoidal temperature change of 5, A-10 & deg; C and a period of T-90s, and use the K-type thermocouple to collect the gas temperature, and the frequency of the temperature collection is 5 times/ s. Set1-Set3 is a narrow-screen particle, Set4, Set5 is a wide-screen particle, the local particle volume fraction is measured by a sampling method, the pressure change is determined by a U-type pressure difference meter, and the change of the temperature pulse parameter at the inlet does not affect the measurement of the heat transfer coefficient between the particles and the fluid, The error is mainly generated by the thermocouple during the measurement process. The particle size and the fluidizing gas velocity are the main factors affecting the heat transfer between the particles and the fluid, the larger the particle size, the higher the fluidization gas velocity, and the greater the heat transfer coefficient between the particles and the fluid. The heat transfer coefficient between the particles and the fluid is the same as that of the literature, but is about 10 times larger than that of the empirical correlation formula. The regression results in the heat transfer correlation of the particle Reynolds number in the range of 1 to Rep-11: 0.648 1/ 2 0.33Nu3.37Re? Pr-(28)? and the distribution of the volume fraction of the radial and axial particles of the particles and the height of the bed layer are basically in agreement with the experimental measurement value; The instantaneous velocity vector of the particles in the fluidized bed shows that the circulating movement of the particles and the local vortex are present in the fluidized bed, and the heat transfer between the particles and the fluid mainly occurs in the small area of the fluidized bed inlet, and the temperature of the particles in the other areas of the bed layer is basically consistent with the temperature of the gas; The particle temperature rise curve of the User-defined heat transfer model is basically the same as the experimental result, and the particle temperature rise curve of the Gujun heat transfer model is slightly less than the experimental result, and the relationship between the instantaneous gas velocity of the gas and the instantaneous temperature of the particles is found, and the temperature of the particles at the inlet of the fluidized bed is directly proportional to the gas velocity, in that proces of loading the vertical heating rod in the fluidized bed, the bubble is mainly generated along the wall surface, and the inner member plays a role of breaking the air bubble and improving the solid content at the center of the bed layer, so that the particle distribution of the bed layer is more uniform. According to the change of gas pressure in the fixed position before and after the addition of the inner component, the bubble breaking frequency of the add-in component is not obviously changed, but the size of the air bubble is reduced, and the internal component is added to improve the fluidization quality. The heat exchange between the gas and the particles mainly occurs in the small area of the fluidized bed inlet, and the temperature of the gas and the particles in the heat exchange area is closely related to the gas speed, and the higher the gas speed and the heat transfer efficiency. after the inner component is added, the temperature distribution of the whole gas and the particles in the fluidized bed is not changed, but the heating form of the built-in heating rod obviously reduces the temperature of the wall surface of the fluidized bed, and the wall deposition can be effectively reduced in the production of the polycrystalline silicon.
【學位授予單位】：青島科技大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TQ021.3
本文編號：2430749
[Abstract]:In this paper, the heat transfer characteristics between the particles and the fluid were studied by using the method of thermal frequency response in the use of glass beads in the range of 0. 1 mm to 0. 5 mm instead of the silicon seed particles in the polycrystalline silicon production as experimental materials. The effect of the particle size, the fluidizing gas velocity and the void ratio of the bed layer on the heat transfer was investigated. The heat transfer coefficient between the 17 particles and the fluid and the flow characteristics of the fluidized bed and the physical properties of the fluid were combined to get the heat transfer correlation. The heat transfer associated with the experiment is applied to Fluent, and the process of gas-solid unsteady heat transfer is simulated. The simulation results are compared with the simulation results of the Gujun heat transfer model and the experimental results. The convection quality of the built-in vertical heating rod in the fluidized bed and the effect of the heat transfer in the bed were investigated. The specific research contents are as follows: 1. A set of experimental equipment for studying the heat transfer characteristics of the gas-solid fluidized bed is set up. The diameter of the fluidized bed is 0.16m and the height is 1.3m. The temperature control system can output a sinusoidal temperature change of 5, A-10 & deg; C and a period of T-90s, and use the K-type thermocouple to collect the gas temperature, and the frequency of the temperature collection is 5 times/ s. Set1-Set3 is a narrow-screen particle, Set4, Set5 is a wide-screen particle, the local particle volume fraction is measured by a sampling method, the pressure change is determined by a U-type pressure difference meter, and the change of the temperature pulse parameter at the inlet does not affect the measurement of the heat transfer coefficient between the particles and the fluid, The error is mainly generated by the thermocouple during the measurement process. The particle size and the fluidizing gas velocity are the main factors affecting the heat transfer between the particles and the fluid, the larger the particle size, the higher the fluidization gas velocity, and the greater the heat transfer coefficient between the particles and the fluid. The heat transfer coefficient between the particles and the fluid is the same as that of the literature, but is about 10 times larger than that of the empirical correlation formula. The regression results in the heat transfer correlation of the particle Reynolds number in the range of 1 to Rep-11: 0.648 1/ 2 0.33Nu3.37Re? Pr-(28)? and the distribution of the volume fraction of the radial and axial particles of the particles and the height of the bed layer are basically in agreement with the experimental measurement value; The instantaneous velocity vector of the particles in the fluidized bed shows that the circulating movement of the particles and the local vortex are present in the fluidized bed, and the heat transfer between the particles and the fluid mainly occurs in the small area of the fluidized bed inlet, and the temperature of the particles in the other areas of the bed layer is basically consistent with the temperature of the gas; The particle temperature rise curve of the User-defined heat transfer model is basically the same as the experimental result, and the particle temperature rise curve of the Gujun heat transfer model is slightly less than the experimental result, and the relationship between the instantaneous gas velocity of the gas and the instantaneous temperature of the particles is found, and the temperature of the particles at the inlet of the fluidized bed is directly proportional to the gas velocity, in that proces of loading the vertical heating rod in the fluidized bed, the bubble is mainly generated along the wall surface, and the inner member plays a role of breaking the air bubble and improving the solid content at the center of the bed layer, so that the particle distribution of the bed layer is more uniform. According to the change of gas pressure in the fixed position before and after the addition of the inner component, the bubble breaking frequency of the add-in component is not obviously changed, but the size of the air bubble is reduced, and the internal component is added to improve the fluidization quality. The heat exchange between the gas and the particles mainly occurs in the small area of the fluidized bed inlet, and the temperature of the gas and the particles in the heat exchange area is closely related to the gas speed, and the higher the gas speed and the heat transfer efficiency. after the inner component is added, the temperature distribution of the whole gas and the particles in the fluidized bed is not changed, but the heating form of the built-in heating rod obviously reduces the temperature of the wall surface of the fluidized bed, and the wall deposition can be effectively reduced in the production of the polycrystalline silicon.
【學位授予單位】：青島科技大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TQ021.3
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