相变微胶囊悬浮液在微矩形通道中的流动换热性能模拟分析

发布时间：2018-01-13 12:03

本文关键词：相变微胶囊悬浮液在微矩形通道中的流动换热性能模拟分析　出处：《西南科技大学》2016年硕士论文　论文类型：学位论文

【摘要】：随着现代科学与技术的发展,特别是在微电子技术方面,随着系统的微型化,单位面积晶体管数量不断增加,运算速度不断提升,每单位面积上产生的热量也相应增加,热流密度不断升高,从而导致这些设备发生故障,甚至是失效。因此需要高效散热,本文提出采用相变微胶囊悬浮液作为冷却工质,利用其大比热容、流动性好等优点,并对其在微矩形通道内的换热特性进行数值模拟研究。首先提出阶梯形状等效比热模型,建立微矩形通道的三维模型,并比较不同阶梯数量下得到的吸热量与实验所得的真实吸热量及壁面温度差与实验所得的壁面温度差的关系,发现阶梯形状比热容模型阶梯数量存在最优值;对于质量浓度为5%的相变微胶囊悬浮液,其3阶梯比热容模型与实验值最接近,为最优的阶梯型等效比热模型;对于质量浓度为10%的相变微胶囊悬浮液,在小质量流量的情况下,3个阶梯时与实验值接近,但是随着质量流量增加,由于质量流量增加,部分相变微胶囊未发生相变,导致和实验数据存在偏差。之后为了对比不同形状的等效比热模型的优缺点,对比阶梯型、矩形、等腰三角形、等腰梯形等模型,发现对于质量浓度为5%相变微胶囊悬浮液,等腰梯形总是表现出了最好的冷却性能,其次是等腰三角形、矩形和阶梯型,其中阶梯型等效比热模型的结果总是和实验结果最接近。最后考虑相变微胶囊颗粒的运动,利用颗粒轨道模型对二维微矩形通道内层流流动进行模拟,并基于等效比热模型进行计算,对比不同壁面加热热流密度和入口速度下的五种工况可以发现:含有相变微胶囊颗粒的悬浮液都比单质水的冷却效果要好一些,其中质量浓度为10%的相变微胶囊悬浮液比5%的冷却效果还要好;随着相变微胶囊质量浓度的增加,模拟相变融化区长度不断增加,表现了更好的冷却效果;在等效比热模型中考虑相变微胶囊颗粒壁材热阻,发现换热强度略慢于相变微胶囊颗粒本身。
[Abstract]:With the development of modern science and technology, especially in the field of microelectronics, with the miniaturization of the system, the number of transistors per unit area is increasing and the computing speed is increasing. The heat generated per unit area also increases accordingly, the heat flux density increases unceasingly, thus causes these equipment to have the breakdown, even is invalid, therefore needs the high efficiency heat dissipation. In this paper, phase change microcapsule suspensions are used as coolant, which has the advantages of large specific heat capacity and good fluidity. The numerical simulation of the heat transfer characteristics in the micro-rectangular channel is carried out. Firstly, the equivalent specific heat model of the stepped shape is proposed, and the three-dimensional model of the micro-rectangular channel is established. The relationship between the heat absorption and the real heat absorption and the wall temperature difference obtained from the experiment is compared, and it is found that there is an optimum number of the steps in the specific heat capacity model of the ladder shape. For the phase change microcapsule suspensions with mass concentration of 5%, the three-step specific heat capacity model is the best step equivalent specific heat model, which is the closest to the experimental value. For the phase change microcapsule suspensions with mass concentration of 10%, under the condition of small mass flow rate, the three steps are close to the experimental values, but with the increase of mass flow rate, the mass flow rate increases. In order to compare the advantages and disadvantages of the equivalent specific heat model with different shapes, the ladder model, rectangle model, isosceles triangle model, isosceles trapezoid model and so on were compared. It was found that the isosceles trapezoid always showed the best cooling performance for the 5% phase change microcapsule suspension, followed by isosceles triangle, rectangle and ladder. The results of the stepped equivalent specific heat model are always the closest to the experimental results. Finally, considering the movement of phase change microcapsules, the laminar flow in two-dimensional microrectangular channels is simulated by the particle orbit model. Based on the equivalent specific heat model, compared with the five conditions of different wall heating heat flux and inlet velocity, it can be found that the suspension containing phase change microcapsule particles is better than the cooling effect of simple water. The cooling effect of phase change microcapsule suspension with mass concentration of 10% is better than that of 5%. With the increase of the mass concentration of phase change microcapsules, the length of phase change melting zone increases continuously, which shows better cooling effect. In the equivalent specific heat model, the heat transfer strength of phase change microcapsules is slightly slower than that of phase change microcapsules.
【学位授予单位】：西南科技大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TK124

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