大颗粒流态化特性与热量传递协同作用的研究
发布时间：2019-02-26 11:59
【摘要】：本文选用粒径在0.1mm~0.5mm范围内的玻璃微珠代替多晶硅生产中的硅晶种颗粒作为实验物料,使用热频率响应实验方法研究了颗粒与流体间的传热特性。考察了颗粒粒度、流化气速及床层空隙率对传热的影响,由测定的17组颗粒与流体间的传热系数与流化床流动特性、流体物性相结合回归出传热关联式。将实验得到的传热关联式应用于Fluent中,模拟了气固非稳态传热过程;模拟结果与Guun传热模型的模拟结果及实验结果进行了比较。考察了流化床内置垂直加热棒对流化质量及床内传热特性的影响。具体研究内容如下:1、搭建了一套用于研究气固流化床传热特性的实验装置,流化床直径0.16m,高1.3m。温度控制系统可以输出幅值5≤A≤10℃、周期T≥90s的正弦式气温变化,使用K型热电偶采集气体温度,温度采集的频率为5次/秒。Set1-Set3为窄筛分颗粒,Set4、Set5为宽筛分颗粒;局部颗粒体积分数采用抽样法测得,压力变化采用U型压差计测定。2、入口处温度脉冲参数的变化对颗粒与流体间传热系数的测量并没有影响,误差主要为热电偶在测量过程中产生的。颗粒粒径及流化气速是影响颗粒与流体间的传热主要因素,颗粒粒径越大、流化气速越高颗粒与流体间的传热系数越大。本文得出的颗粒与流体间的传热系数与文献结果相同,但比经验关联式的计算值大10倍左右,回归得到了颗粒雷诺数在1≤Rep≤11范围内的传热关联式:0.648 1/2 0.33Nu3.37 Re?Pr-(28)?,关联式的给出值与实验值的误差在15%以内,满足工程计算的精度要求。3、模拟了气固非稳态传热过程,颗粒的径向及轴向颗粒体积分数分布及床层的高度与实验测量值基本吻合;分析颗粒的瞬时速度矢量表明,流化床内存在由中心向两侧总体的颗粒循环运动及局部的涡流;颗粒与流体间的热量传递主要发生在流化床入口很小的区域内,床层其他区域内颗粒与气体的温度基本一致;User-defined传热模型的颗粒升温曲线与实验结果基本相同,Guun传热模型模拟的颗粒升温曲线略小于实验结果;分析气体瞬时气速与颗粒瞬时温度之间的关系发现,流化床入口处颗粒的温度与气体速度成正比,即与颗粒雷诺数成正比,颗粒雷诺数对气固传热过程起着重要作用。4、模拟流化床内加载垂直加热棒过程中发现,气泡主要沿着壁面产生,内构件起到破碎气泡及提高床层中心处的固含量的作用,使床层的颗粒分布更加均匀。对比添加内构件前后固定位置点气体压力变化发现,添加内购件气泡破碎频率没有明显改变,但气泡的尺寸减小,添加内构件提高了流化质量。气体与颗粒的热量交换主要发生在流化床入口很小域内,热交换区域气体与颗粒的温度与气速密切相关,气速越大传热效率越高。添加内构件后并没有改变流化床内整体的气体与颗粒的温度分布,但内置加热棒的加热形式明显降低了流化床壁面温度,在多晶硅生产中可以有效减少壁面沉积。
[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.
【学位授予单位】：青岛科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ021.3
本文编号：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.
【学位授予单位】：青岛科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ021.3
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