小型平板热管的研究
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摘要
热管是依靠自身内部工作液体相变来实现传热的传热元件，具有结构紧凑、高导热性、优良的等温性、热流密度可变性、热流方向可逆性、恒温特性、环境的适应性等基本特性，在电子电器工程中取得许多应用成果。
随着近年电子技术的迅速发展，电子器件高频、高速及集成电路的密集和小型化，单位容积电子器件的发热量迅速增大。电子技术的发展需要良好的散热手段来保证。因此，研究开发小型电子冷却用热管已成为国内外热管界及热管厂家的一个热点领域，而国内在这方面的研究尚未开展起来。另外，对于很多应用场合，如芯片、集成电路板、CPU等是平面形状，如采用管状热管传热，需增加冷、热板，这就增加了传热热阻，并且均温性不好。在这些场合，小型平板热管具有优势。因此，本文开发了电子冷却用小型平板热管，并对其换热性能进行了理论分析和实验研究。
设计制造
热管设计基本包括三部分：管壳材料的选择、吸液芯结构的设计和工质的选择。由于铜的高传导性、抗氧化性和重量轻特点，同时考虑实验热管的应用场合（电子器件冷却），选择铜为壳体材料。热管工作的基础是工质的蒸发和冷凝，因此选择合适的工质是设计和制造的一个重要方面。影响工质选择的因素包括：合适的工作温度范围；适当的饱和蒸汽压；良好的导热性；工质与壳体材料的相容性，以及好的热稳定性。考虑到上述因素，选择丙酮、乙醇和水为工质。根据CPU热管散热器的需要，热管的尺寸为80mm*65mm，厚度为4mm。吸液芯结构形式采用的是五层磷铜丝网。平板型热管的制造方法决定着热管质量。热管的制造包括：管材的清洗、端口的封焊、检漏、抽真空、充液以及封口6个步骤。本热管的制造过程中平板两端的焊接以及热管的封口技术是最关键的，直接决定着热管的传热性能。
热管性能测试系统的开发设计
CPU热管散热器性能测试系统采用LabVIEW6.1图形化编程平台设计。基于虚拟仪器的CPU热管散热器性能试验系统具有数据的采集、存储、分析处理等特点。它可以对试验整个过程进行实时监控，只需进行适当的参数设
置后就可以完成各种散热器的性能试验。本系统主要由:参数设置、控制面板、数据采集、数据处理、系统帮助五部分组成。测量模拟参数时，需要进行模拟输入设置，包括输入模式（单端输入或差分输入）、分辨率、输入范围、采样范围、采样频率、精度和噪声等。
为了提高测量精度试验采用了以下措施：
热电偶冷端补偿；
热电偶非线性补偿；
粗大误差剔除；
温度信号的数字滤波。
理论分析和实验研究
一个热管换热性能的好坏，需要理论上的分析和实验的证实。本文先从理论上分析了小型平板热管的传热机理，求解了各种传热极限，用于与实验结果进行对比和分析。随后在理论分析的基础上做了大量的实验研究。
首先建立了小型平板热管实验装置。利用此装置可进行小型平板热管的加热、冷却，数据采集等工作。试验装置主要由加热部分、冷却部分和温度测量部分组成。加热部分主要包括：电阻加热器、功率表、调压器、绝缘材料和电源。由于电加热功率测量简单、精确，故采用加热器模拟热源放热，并用绝缘材料对蒸发段和绝热段保温，使辐射和对流的热损失减少到最小。本试验分别由调压器和功率表来控制和测量加热功率的大小。本实验装置采用空气冷却方式。数据采集分析系统连接k型镍铬-镍硅热电偶，来测量整个热管表面的温度分布。
通过实验测定了热管在不同加热功率、冷却强度、工质种类、充液率下的热管蒸发端和冷凝端表面温度。从而确定了热管的传热量以及热管的传热系数。根据实验结果进一步分析了热管的温度分布性能，冷却强度、加热功率、工质种类、充液率等因素对热管性能的影响。拟合出较准确的实验关联式，用于指导相似结构热管的设计和实验。
结 论
通过实验，分析总结出以下结论：
本试验所制造的平板型热管的热阻大约在0.26 — 0.37 oC/W，达到降低
热阻的目的，平板型热管均温性好，基本可以满足CPU散热器的要求。
平板型热管传热性能试验台可以完成各种散热器的空气冷却试验。整个试验台的风速V在0～12m/s的范围内可控，还可以根据试验条件的具体要求更换风机来提供更大的风速。主要试验测试段容易拆卸，便于更换各种尺寸规格的散热器，例如：微机电源的散热器、显卡芯片组散热器等。
基于虚拟仪器的CPU热管散热器性能试验系统具有数据的采集、存储、分析处理等特点。它可以对试验整个过程进行实时监控，只需进行适当的参数设置后就可以完成各种散热器的性能试验。
丙酮、乙醇和水这三种工质表现出不同的传热特性。通过对工质不同的热管试验数据的分析处理，可以发现：试验热管的工质乙醇的换热性能最好，丙酮最差。
在本文的实验条件下，以丙酮为工质的平板型热管最佳充液率大约为20%；以水为工质的平板型热管最佳充液率大约为50%；以乙醇为工质的平板型热管最佳充液率大约为50%。
实验参数风速V和加热功率Qe对热管传热系数的影响较大。随着V的增加，热管传热系数呈上升趋势；随着Qe的增加在达到热管的毛细传热极限之前，热管传热系数呈增加趋势；而当热管达到毛细传热极限之后，热管的传热系数下降、热阻上升
The heat pipe is a heat transfer device that utilizes the phase change of working liquid in it. It has many essential characteristics that make it useful in a wide variety of applications in electronic engineering: the compact structure, the high heat thermal conductivity, the excellent isothermal property, the variability of the heat flux density, the ability to make the heat flux direction reverse, the ability to maintain constant evaporator temperature under different heat flux level, the ability to adapt the environment etc.
With the rapid development of electronic technology, the high calculation speed of the electronic component and the denseness, the heat transfer increases rapidly of electronic component per unit volume in recent years. The development of electronic technology needs the excellent heat transfer measures. Therefore, the manufactories of heat pipe have focused their attentions on the investigation and development of mini heat pipe for electronics cooling. However, the internal investigation has not been conducted. In addition, the CMOS chip, the circuit board and CPU are all flat shape. If we used tubular shape heat pipes in those applications, we would add ‘cold board’ and ‘hot board’ to them. At the same time, the heat resistance and the temperature gradient would increase. Because the mini flat plate heat pipe has many advantages, this paper designs and manufactures a mini flat plate heat pipe for electronics cooling. What’s more, the theoretical analysis and experimental investigation on the heat transfer performance are conducted.
DESIGNATION and MANUFACTURE
Basically, the heat pipe design consists of three major components: selection of case material and working fluid, and the design of wicking structure. Because of the high thermal conductivity, resisted oxidation and less density, phosphor copper is selected as the case material. Because the vaporization and condensation of the working fluid are the basic process for operation of a heat pipe，the selection of a suitable working fluid is perhaps the most important aspect of the designation and manufacture process. Factors that affect the selection of an appropriate working fluid include the operating temperature range, the vapor pressure, the thermal conductivity, the compatibility with the wick, the case materials, stability and so on. With consideration of these factors, distilled water, acetone and ethanol are selected as the working fluid. According to the actual requirement of the heat pipe/heat sink , the length and width of the heat pipe are 80㎜and 65mm. And the thickness is
4mm. The configuration of wicks is 5 layers of phosphor copper filter.
The quality of the flat plate heat pipe was largely depended on the manufacture technology, which includes the cleaning of the case, the envelopment of the terminals, the leak checking process, the vacuum process, filling up and sealing. In the thesis, the envelopment of the terminals and sealing is the key process by which the performance of the flat plate heat pipe was decided.
Thermal Performance Measuring System for Heat Pipe/Heat Sink
The Thermal Performance Measuring System for Heat Pipe/Heat Sink Applied on CPU is developed by the LabVIEW6.1, which is the program platform of graphic programming. With the abilities of data collection、storage、analysis, the measuring system can real-timely monitor the entire experiment and adapt other applications by easily altering some parameters. The system was composed by setting panel、 control panel、 data acquisition 、data processing、 help. Applied on the simulation acquisition, the system must carefully take many factors into account such as the input model、resolution、input scales、sampling frequency 、precision、noise and so forth.
In order to improve the precision, many measures are applied in this system such as follows：
1、thermocouple cold end compensate;
2、nonlinear compensate for thermocouple;
3、eliminating big errors;
4、digital filtering of signals.
THEORETICAL ANALYSIS
and EXPERIMENTAL INV
随着近年电子技术的迅速发展，电子器件高频、高速及集成电路的密集和小型化，单位容积电子器件的发热量迅速增大。电子技术的发展需要良好的散热手段来保证。因此，研究开发小型电子冷却用热管已成为国内外热管界及热管厂家的一个热点领域，而国内在这方面的研究尚未开展起来。另外，对于很多应用场合，如芯片、集成电路板、CPU等是平面形状，如采用管状热管传热，需增加冷、热板，这就增加了传热热阻，并且均温性不好。在这些场合，小型平板热管具有优势。因此，本文开发了电子冷却用小型平板热管，并对其换热性能进行了理论分析和实验研究。
设计制造
热管设计基本包括三部分：管壳材料的选择、吸液芯结构的设计和工质的选择。由于铜的高传导性、抗氧化性和重量轻特点，同时考虑实验热管的应用场合（电子器件冷却），选择铜为壳体材料。热管工作的基础是工质的蒸发和冷凝，因此选择合适的工质是设计和制造的一个重要方面。影响工质选择的因素包括：合适的工作温度范围；适当的饱和蒸汽压；良好的导热性；工质与壳体材料的相容性，以及好的热稳定性。考虑到上述因素，选择丙酮、乙醇和水为工质。根据CPU热管散热器的需要，热管的尺寸为80mm*65mm，厚度为4mm。吸液芯结构形式采用的是五层磷铜丝网。平板型热管的制造方法决定着热管质量。热管的制造包括：管材的清洗、端口的封焊、检漏、抽真空、充液以及封口6个步骤。本热管的制造过程中平板两端的焊接以及热管的封口技术是最关键的，直接决定着热管的传热性能。
热管性能测试系统的开发设计
CPU热管散热器性能测试系统采用LabVIEW6.1图形化编程平台设计。基于虚拟仪器的CPU热管散热器性能试验系统具有数据的采集、存储、分析处理等特点。它可以对试验整个过程进行实时监控，只需进行适当的参数设
置后就可以完成各种散热器的性能试验。本系统主要由:参数设置、控制面板、数据采集、数据处理、系统帮助五部分组成。测量模拟参数时，需要进行模拟输入设置，包括输入模式（单端输入或差分输入）、分辨率、输入范围、采样范围、采样频率、精度和噪声等。
为了提高测量精度试验采用了以下措施：
热电偶冷端补偿；
热电偶非线性补偿；
粗大误差剔除；
温度信号的数字滤波。
理论分析和实验研究
一个热管换热性能的好坏，需要理论上的分析和实验的证实。本文先从理论上分析了小型平板热管的传热机理，求解了各种传热极限，用于与实验结果进行对比和分析。随后在理论分析的基础上做了大量的实验研究。
首先建立了小型平板热管实验装置。利用此装置可进行小型平板热管的加热、冷却，数据采集等工作。试验装置主要由加热部分、冷却部分和温度测量部分组成。加热部分主要包括：电阻加热器、功率表、调压器、绝缘材料和电源。由于电加热功率测量简单、精确，故采用加热器模拟热源放热，并用绝缘材料对蒸发段和绝热段保温，使辐射和对流的热损失减少到最小。本试验分别由调压器和功率表来控制和测量加热功率的大小。本实验装置采用空气冷却方式。数据采集分析系统连接k型镍铬-镍硅热电偶，来测量整个热管表面的温度分布。
通过实验测定了热管在不同加热功率、冷却强度、工质种类、充液率下的热管蒸发端和冷凝端表面温度。从而确定了热管的传热量以及热管的传热系数。根据实验结果进一步分析了热管的温度分布性能，冷却强度、加热功率、工质种类、充液率等因素对热管性能的影响。拟合出较准确的实验关联式，用于指导相似结构热管的设计和实验。
结 论
通过实验，分析总结出以下结论：
本试验所制造的平板型热管的热阻大约在0.26 — 0.37 oC/W，达到降低
热阻的目的，平板型热管均温性好，基本可以满足CPU散热器的要求。
平板型热管传热性能试验台可以完成各种散热器的空气冷却试验。整个试验台的风速V在0～12m/s的范围内可控，还可以根据试验条件的具体要求更换风机来提供更大的风速。主要试验测试段容易拆卸，便于更换各种尺寸规格的散热器，例如：微机电源的散热器、显卡芯片组散热器等。
基于虚拟仪器的CPU热管散热器性能试验系统具有数据的采集、存储、分析处理等特点。它可以对试验整个过程进行实时监控，只需进行适当的参数设置后就可以完成各种散热器的性能试验。
丙酮、乙醇和水这三种工质表现出不同的传热特性。通过对工质不同的热管试验数据的分析处理，可以发现：试验热管的工质乙醇的换热性能最好，丙酮最差。
在本文的实验条件下，以丙酮为工质的平板型热管最佳充液率大约为20%；以水为工质的平板型热管最佳充液率大约为50%；以乙醇为工质的平板型热管最佳充液率大约为50%。
实验参数风速V和加热功率Qe对热管传热系数的影响较大。随着V的增加，热管传热系数呈上升趋势；随着Qe的增加在达到热管的毛细传热极限之前，热管传热系数呈增加趋势；而当热管达到毛细传热极限之后，热管的传热系数下降、热阻上升
The heat pipe is a heat transfer device that utilizes the phase change of working liquid in it. It has many essential characteristics that make it useful in a wide variety of applications in electronic engineering: the compact structure, the high heat thermal conductivity, the excellent isothermal property, the variability of the heat flux density, the ability to make the heat flux direction reverse, the ability to maintain constant evaporator temperature under different heat flux level, the ability to adapt the environment etc.
With the rapid development of electronic technology, the high calculation speed of the electronic component and the denseness, the heat transfer increases rapidly of electronic component per unit volume in recent years. The development of electronic technology needs the excellent heat transfer measures. Therefore, the manufactories of heat pipe have focused their attentions on the investigation and development of mini heat pipe for electronics cooling. However, the internal investigation has not been conducted. In addition, the CMOS chip, the circuit board and CPU are all flat shape. If we used tubular shape heat pipes in those applications, we would add ‘cold board’ and ‘hot board’ to them. At the same time, the heat resistance and the temperature gradient would increase. Because the mini flat plate heat pipe has many advantages, this paper designs and manufactures a mini flat plate heat pipe for electronics cooling. What’s more, the theoretical analysis and experimental investigation on the heat transfer performance are conducted.
DESIGNATION and MANUFACTURE
Basically, the heat pipe design consists of three major components: selection of case material and working fluid, and the design of wicking structure. Because of the high thermal conductivity, resisted oxidation and less density, phosphor copper is selected as the case material. Because the vaporization and condensation of the working fluid are the basic process for operation of a heat pipe，the selection of a suitable working fluid is perhaps the most important aspect of the designation and manufacture process. Factors that affect the selection of an appropriate working fluid include the operating temperature range, the vapor pressure, the thermal conductivity, the compatibility with the wick, the case materials, stability and so on. With consideration of these factors, distilled water, acetone and ethanol are selected as the working fluid. According to the actual requirement of the heat pipe/heat sink , the length and width of the heat pipe are 80㎜and 65mm. And the thickness is
4mm. The configuration of wicks is 5 layers of phosphor copper filter.
The quality of the flat plate heat pipe was largely depended on the manufacture technology, which includes the cleaning of the case, the envelopment of the terminals, the leak checking process, the vacuum process, filling up and sealing. In the thesis, the envelopment of the terminals and sealing is the key process by which the performance of the flat plate heat pipe was decided.
Thermal Performance Measuring System for Heat Pipe/Heat Sink
The Thermal Performance Measuring System for Heat Pipe/Heat Sink Applied on CPU is developed by the LabVIEW6.1, which is the program platform of graphic programming. With the abilities of data collection、storage、analysis, the measuring system can real-timely monitor the entire experiment and adapt other applications by easily altering some parameters. The system was composed by setting panel、 control panel、 data acquisition 、data processing、 help. Applied on the simulation acquisition, the system must carefully take many factors into account such as the input model、resolution、input scales、sampling frequency 、precision、noise and so forth.
In order to improve the precision, many measures are applied in this system such as follows：
1、thermocouple cold end compensate;
2、nonlinear compensate for thermocouple;
3、eliminating big errors;
4、digital filtering of signals.
THEORETICAL ANALYSIS
and EXPERIMENTAL INV
引文
张红、庄骏，《热管技术及其工程应用》，化学工业出版社，2000年6月,第一版，1～2
G. P. Peterson, 《An Introduction to Heat Pipes Modeling, Testing and Applications》, JOHN WILEY&SONS, INC. 1994，2～3
staio Y, Mochizuki M, goto K, Nanyen T et al. The application for personal computer using heat pipe technology. 10thIHPC Preprints of Session e6 Stuttgart Sep. 1997,2～3
Kevin Grubb, CFD Modeling of Therma-BaseTM Heat Sink, Thermacore, Inc. ,3～4
M.Schneider+, M. Yoshida+, M. Groll+, Investigation of Interconnected Mini Heat Pipe Array for Micro Electronics Cooling, +Institute for Nuclear Technology and Energy Systems(IKE), Pfaffenwaldring 31,70550 Stuttgart, Germany,3～4
李亭寒、华诚生，《热管设计与应用》，化学工业出版社，1987.8，第一版，6～8
Ochterbeck, J. M., and Peterson, G. P., freeze/Thaw Characteristics of a Copper-Water Heat Pipe: Effects of Noncondensible Gas Charge , AIAA Journal of Thermophysics and Heat Transfer, Vol. 7, No. 1, pp. 7～9
Chi, S. W., Heat Theory and Practice, McGraw-Hill, New York,1976,9～10
Cotter T. P. Theory of heat pipes. Los Alamos Scientific Lab. Report No. LA-3246-MS. 1965,12～14
Wageman W E, Guevara F. A. Fluid flow through a porous channel. Phys. Fluids. 1960,3（6）,13～14
Ivanovskii, M. N., Sorokin, V. P., and Yagodkin, I. V., The Physical Principles of Heat Pipes, Clarendon Oxford 1982, ,14～15
Chisholm, D., The Heat Pipe, Mills anf Boon, London, England, 1971,16～17
Chi, S. W., Heat Pipe Theory and Practice, McGraw-Hill, New York, 1976,21～22
Levy E K. Chou S F. The sonic limit in sodium heat pipes. ASME J. Heat Transfer, 1973, 23～24
Busse, C.A., and Kemme, Theory of the Ultimate Heat Transfer of Cylindrical Heat Pipes, International Journal of Heat Mass Transfer, Vol. 16, pp. 169,23～24
Cotter, T. P., Heat Pipe Startup Dynamics, Proc. SAE Thermionic Conversion Specialist Conference, Palo Alto, CA. 1967,24～25
Dunn, P. D., and Reay, D. A., Heat Pipe, 3rd ed., Pergamon, Oxford, 1982,26～27
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施明恒，《热工实验的原理和技术》，东南大学出版社，1992，第一版，28～29
徐大中、糜振虎，《热工测量与实验数据处理》，上海交通大学出版社，1991年12月，第一版，36～37
石振东、刘国庆，《实验数据处理和曲线拟合技术》，哈尔滨船舶学院出版社，1991年12月，第一版，37～38
曹尔第，《实验误差与数据处理》，科学技术出版社，第一版，1988年1月，37～38
王骏、辛明道、谢欢德，小倾角萘热管传热性能的实验，中国工程热物理协会热管专业组编，1994年8月，40～41
柯玲、陈远国、谢欢德，水热管的低温特性研究，中国工程热物理协会热管专业组编，1994年8月，43～44
方开泰、全辉、陈庆云，《实用回归分析》，科学出版社，1988年10月，第一版，44～46
汪敏生，《LABVIEW基础教程》，电子工业出版社，2001年1月，53～54
Gary W.Johnson Richard Jennings 著，武嘉澎 陆劲昆译，《LABVIEW 图形编程》，北京大学出版社，2002年1月，55～56
杨乐平，李海涛，赵勇，杨磊，《LABVIEW高级程序设计》，清华大学出版社，2002年9月，56～57