Analysis of Evaporative Heat Transfer of Micro Heat Pipes for Cooling Electronic Components

Analysis of Evaporation Heat Transfer of Micro Heat Pipes for Cooling Electronic Devices FAN Chunli 1 QU Wei 2 YANG Li 1 HUA Shunfang 1 MA Tongze 2 “l. Department of Power Engineering, Naval University of Engineering, Wuhan 430033, China; 2. Research Institute of Engineering Thermophysics, Chinese Academy of Sciences Institute, Beijing 100080 research shows that: thin liquid film heat pipe evaporation heat transfer effect is much greater than the thick liquid film; solid-liquid contact angle gradually decreases in the evaporation section along the axial direction; heat transfer calculation of the heat pipe with rounded corners At the time, the relationship between the minimum meniscus radius and the processing radius is restricted, and it cannot be simply replaced by the machining fillet.

Micro heat pipe is an emerging technology developed with the development of microelectronics technology. With the increase of the number of circuits in a computer chip, the dissipation of heat generated by it becomes more and more difficult. For example, the heat flow generated by chips of a host computer and a main computer has reached 60 W/cm2, and in 2000, it has exceeded 100 W/cm2. In addition to the requirement of the highest temperature on the chip, there is a higher requirement for the uniformity of the temperature. Therefore, the heat dissipation of electronic devices has become an increasingly important technology in the development and research of electronic products. The heat dissipation performance directly influences the final electronics. Product cost, reliability and performance. Microheaters are a promising technology that can be used in electronic devices to achieve high heat removal rates and temperature homogenization.

Since Cotter proposed the concept of miniature heat pipes in 1984, a large number of theories have been performed on miniature heat pipes, which consist of an evaporation section, an adiabatic section, and a condensation section. The liquid film distribution is as shown. For the evaporating section, it is assumed that: 1 the steam temperature is at the saturated temperature of the working fluid and there is no gradient along the axial direction.

2 The heat pipe is in a stable working condition. 3 In any axial section, the radius of the meniscus of each corner area is a constant value and only changes in the axial direction.

4 Any section of the heat pipe has uniform wall temperature and only changes in the axial direction.

Temperature and steam temperature, T is the average value of steam temperature, liquid temperature, and vapor-liquid interface temperature, surface tension, K is meniscus curvature, and p (i is the disengagement pressure).

In the equilibrium film area, the detachment pressure plays a dominant role. Take T. as the saturation temperature Tsat of the working fluid, and qm(.=0) can obtain the liquid film thickness in the boundary line area where A is the Hamakei constant and Tw is the heat pipe wall. temperature.

The second-order differential equation 141 for thin film thickness is solved by analyzing the flow and heat transfer: Pi is the viscosity of the liquid. Since the liquid film thickness in the evaporating thin liquid film area is very small, the heat conduction heat flux of the liquid film is (surface thermal resistance Ri): the distribution pattern of the liquid film on the wall It can be imagined that when the heat pipe reaches the maximum heat transfer capacity, the processing fillet at the end of the evaporation section is reached. On the upper end of the layer of evaporating liquid film is exactly the transitional position of the balance film area and the evaporation film area.

If the microscopic liquid film area includes two parts, and one part is the equilibrium film area, the liquid film thickness in this part is very small. Due to the influence of the detachment pressure, evaporation of the liquid film is suppressed, and the evaporation amount is almost the thermal conductivity coefficient in which ki is a liquid.

Equation (2) can be solved by the fourth-order Runge-Kutta method.

The value of T* in each step can be obtained by iteratively coupled equations (1) and (3), so that the circumferential distribution of T* and heat flux in the thin liquid film can be obtained.

2 Meniscus area in the meniscus of the meniscus at any point in the circumferential direction

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Rooted in the northeast, it radiates across the country.Sihuan Pipeline Company, integrating R&D, design, production, experiment and testing, has been specialized in producing nylon gas transmission pipeline, fuel pipeline and high-pressure pipeline products for 20 years.At present, the enterprise has nearly 40000 square meters of modern production workshops and business office buildings, more than 200 senior employees, and an annual output of 56 million automobile


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Sihuan Pipeline Co., Ltd. takes technological innovation as its eternal pursuit, and has accumulated profound technical information through 20 years of scientific research, providing the most advanced technical support for each product project.The company has been recognized by the municipal technology center and participated in the revision of several national standards and industrial standards.The scientific research team has reached cooperation with Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun University of Technology and other scientific research institutes, jointly developed a number of provincial science and technology department projects, and achieved a number of technical achievements.The testing laboratory has passed the ISO17025 laboratory management system certification. It has more than 40 sets of tube performance testing equipment and raw material testing instruments, and the testing means are


internationally leading.



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Sihuan Pipeline Company, based on the industry trend, formulates equipment procurement plans every year and continues to introduce world-class production equipment. Now, it has several automatic extrusion production lines in Merafil, Switzerland, as well as international top equipment such as Clarke bellows molding machine in France, Opel shrink pipe machine in Italy, which are stable, efficient, highly accurate, meet the diversified needs of the main engine factory, and achieve the brand charm of Sihuan.

Scientific management, safeguard quality.The production department implements a quality control system higher than the national standard, adopts 6S management on the site, regularly carries out personnel training, and constantly improves the process procedures.The quality inspection department must inspect every product and every process, resolutely put an end to the delivery of substandard products, and strive to promote product quality to the highest standards in the industry.



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The products produced by Sihuan Pipeline Company are related to brake systems (including vacuum brake pipes, air brake pipes, spiral pipes, rear axle brake pipes);Fuel system (cover to atmospheric ash filter pipe, fuel pipe, crankcase vent pipe, vacuum pipe);New energy thermal management system and industrial energy storage water inlet and return pipeline assembly integrate safety functions such as check valve, flow regulating valve and exhaust valve, which directly affect vehicle performance and are prerequisites for safe driving;SCR system (including electric heating urea pipe, cooling water pipe and gas pipeline);High pressure pipeline products are used in clutch power assist system and hydraulic lifting pipeline. Excellent performance, stable physical performance, excellent chemical resistance, good processing performance and long service life.All products have passed the CQC certification, and all parameters tested in the laboratory are far higher than the national standards and industry standards.

After 20 years of hard work, Sihuan Pipeline Company has won recognition from all walks of life. It has successively won honorary titles such as "Jilin Province Small Giant Enterprise in Science and Technology", "High tech Enterprise Certificate", Changchun "Specialized, Special and New" SMEs. Its products are


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In the future, Sihuan Pipeline Co., Ltd. will cater to the national carbon peak strategy, research and develop low emission pipeline manufacturing technology in a forward-looking manner, provide customers with high-quality products and services with innovation and quality, and create a better future for the automotive industry!


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