非线性在小型电子设备散热中的应用与研究
发布时间：2019-04-02 02:42
【摘要】：随着时代发展,电子设备不断朝着小型化和集成化方向进展,随之,电子设备的散热问题成为影响其寿命的直接原因,是学者们关注的焦点,也是本文关注的问题。非线性科学是发展起来的新型交叉学科。非线性,是指两个变量间的数学关系,不是直线,而是曲线、曲面、或不确定的属性,是不成简单比例(即线性)关系的。它是自然界复杂性的典型性质之一,非线性更接近客观事物性质本身。因此,研究非线性现象的价值即为改变传统的认知,加深对自然界的认知。在现代的物质世界中,非线性现象无处不在,如气候的变化中会出现非线性现象,数学、物理、经济学、社会学、音乐等领域中也渗透着非线性。而在小型电子设备工作的时候,由发热单元产生的热量与周围温度形成的温差,导致设备内部空气的流动,也存在着非线性现象。本文以小型电子设备散热为应用背景,在自然对流的情况下,将电子设备模型抽象为带有不同类型热源的腔体,通过数值模拟和实验研究分析其内部存在的振荡及混沌等非线性特性及自然对流换热规律。本文首先采用FLUNT软件对底部加热无内热源的长方体腔,底部带有单热源和底部带有双热源的长方体腔内空气的自然对流换热问题进行了数值模拟。得到如下成果:随着Rayleigh数的增大,无内热源的长方体腔内的空气流动经历了稳定,单倍周期,拟周期,通过振荡最终到达混沌的流动状态;带有长度接近腔体长度单热源的腔内空气流动经历了稳定,单倍周期,拟周期,带有双热源的腔内空气流动状态始终为混沌状态,空气的流态与腔内换热强度有关;在分析热源数量对换热强度的影响中可知,腔内无内热源的腔顶平局Nusselt最高,其次是带有长热源的腔体,最后为带有双热源的腔体;腔内带有单热源时,换热强度随热源长度增加而增大,换热速率随长度增大而减慢;当腔内带有两个内热源,热源和上下壁面的温差恒定时,热源间的距离增大,换热强度先增大后减小,热源间的距离恒定时,随温差增大换热强度增大;通过数值模拟分析二维模型和三维模型腔顶平均Nusselt数大小可知,二维模型不可代替三维模型。其次,本文采用无接触激光干涉技术和烟可视化手段对上述模型进行实验分析。探讨了腔体尺寸、温差、热源间距离对涡卷初始态的影响并观察了涡卷的数量及形态,也分析了模拟中混沌出现的原因。本文从以上几个方面进行了研究,同时为小型电子设备散热提供了一定的理论参考价值。
[Abstract]:With the development of the times, electronic equipment is developing towards miniaturization and integration, and the heat dissipation of electronic equipment has become the direct cause of affecting its life, which is the focus of scholars' attention, and is also the focus of this paper. Nonlinear science is a new interdisciplinary discipline. Nonlinearity refers to the mathematical relationship between two variables, not a straight line, but a curve, surface, or uncertain attribute, which is not simply proportional (that is, linear). It is one of the typical properties of the complexity of nature, and the nonlinearity is closer to the nature of the objective thing itself. Therefore, the value of studying nonlinear phenomena is to change the traditional cognition and deepen the cognition of nature. In the modern material world, nonlinear phenomenon is everywhere, such as climate change will appear nonlinear phenomenon, mathematics, physics, economics, sociology, music and other fields are also permeated with nonlinearity. While the small electronic equipment is working, the temperature difference between the heat generated by the heating unit and the surrounding temperature leads to the flow of air in the equipment, and there is also a nonlinear phenomenon. In this paper, the model of electronic equipment is abstracted as a cavity with different types of heat source under the condition of natural convection, taking the heat dissipation of small electronic equipment as the application background. The nonlinear characteristics of oscillation and chaos and the law of natural convection heat transfer are analyzed by numerical simulation and experimental study. In this paper, the FLUNT software is used to simulate the natural convection heat transfer in a rectangular cavity with single heat source and double heat source at the bottom and in a rectangular cavity with no inner heat source at the bottom, and the natural convection heat transfer problem in the rectangular cavity with two heat sources at the bottom is numerically simulated. The results are as follows: with the increase of Rayleigh number, the air flow in a rectangular cavity without internal heat source goes through a stable, single period, quasi-period, and finally reaches the chaotic flow state by oscillation; The air flow in the cavity with the length close to the length of the cavity has experienced a stable, single period and quasi-period. The air flow state with double heat sources is always chaotic, and the air flow pattern is related to the heat transfer intensity in the cavity. In the analysis of the effect of heat source quantity on heat transfer intensity, it can be seen that the top level Nusselt of cavity without internal heat source is the highest, the cavity with long heat source is the next, and the cavity with double heat source is the last one. When there is a single heat source in the cavity, the heat transfer intensity increases with the increase of the heat source length, and the heat transfer rate decreases with the increase of the heat source length. When there are two internal heat sources in the cavity and the temperature difference between the heat source and the upper and lower wall is constant, the distance between the heat sources increases, the heat transfer intensity increases first and then decreases, and when the distance between the heat sources is constant, the heat transfer intensity increases with the increase of the temperature difference. Through numerical simulation and analysis of the average Nusselt number of two-dimensional model and three-dimensional model, it can be seen that the two-dimensional model cannot replace the three-dimensional model. Secondly, the above-mentioned models are analyzed by non-contact laser interferometry and smoke visualization. The effects of cavity size, temperature difference and the distance between heat sources on the initial state of the scroll are discussed. The number and shape of the scroll are observed, and the causes of chaos in the simulation are also analyzed. This paper has carried on the research from the above several aspects, at the same time has provided the certain theoretical reference value for the small electronic equipment heat dissipation.
【学位授予单位】：吉林建筑大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN60
[Abstract]:With the development of the times, electronic equipment is developing towards miniaturization and integration, and the heat dissipation of electronic equipment has become the direct cause of affecting its life, which is the focus of scholars' attention, and is also the focus of this paper. Nonlinear science is a new interdisciplinary discipline. Nonlinearity refers to the mathematical relationship between two variables, not a straight line, but a curve, surface, or uncertain attribute, which is not simply proportional (that is, linear). It is one of the typical properties of the complexity of nature, and the nonlinearity is closer to the nature of the objective thing itself. Therefore, the value of studying nonlinear phenomena is to change the traditional cognition and deepen the cognition of nature. In the modern material world, nonlinear phenomenon is everywhere, such as climate change will appear nonlinear phenomenon, mathematics, physics, economics, sociology, music and other fields are also permeated with nonlinearity. While the small electronic equipment is working, the temperature difference between the heat generated by the heating unit and the surrounding temperature leads to the flow of air in the equipment, and there is also a nonlinear phenomenon. In this paper, the model of electronic equipment is abstracted as a cavity with different types of heat source under the condition of natural convection, taking the heat dissipation of small electronic equipment as the application background. The nonlinear characteristics of oscillation and chaos and the law of natural convection heat transfer are analyzed by numerical simulation and experimental study. In this paper, the FLUNT software is used to simulate the natural convection heat transfer in a rectangular cavity with single heat source and double heat source at the bottom and in a rectangular cavity with no inner heat source at the bottom, and the natural convection heat transfer problem in the rectangular cavity with two heat sources at the bottom is numerically simulated. The results are as follows: with the increase of Rayleigh number, the air flow in a rectangular cavity without internal heat source goes through a stable, single period, quasi-period, and finally reaches the chaotic flow state by oscillation; The air flow in the cavity with the length close to the length of the cavity has experienced a stable, single period and quasi-period. The air flow state with double heat sources is always chaotic, and the air flow pattern is related to the heat transfer intensity in the cavity. In the analysis of the effect of heat source quantity on heat transfer intensity, it can be seen that the top level Nusselt of cavity without internal heat source is the highest, the cavity with long heat source is the next, and the cavity with double heat source is the last one. When there is a single heat source in the cavity, the heat transfer intensity increases with the increase of the heat source length, and the heat transfer rate decreases with the increase of the heat source length. When there are two internal heat sources in the cavity and the temperature difference between the heat source and the upper and lower wall is constant, the distance between the heat sources increases, the heat transfer intensity increases first and then decreases, and when the distance between the heat sources is constant, the heat transfer intensity increases with the increase of the temperature difference. Through numerical simulation and analysis of the average Nusselt number of two-dimensional model and three-dimensional model, it can be seen that the two-dimensional model cannot replace the three-dimensional model. Secondly, the above-mentioned models are analyzed by non-contact laser interferometry and smoke visualization. The effects of cavity size, temperature difference and the distance between heat sources on the initial state of the scroll are discussed. The number and shape of the scroll are observed, and the causes of chaos in the simulation are also analyzed. This paper has carried on the research from the above several aspects, at the same time has provided the certain theoretical reference value for the small electronic equipment heat dissipation.
【学位授予单位】：吉林建筑大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN60
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