Sintering technology for micro heat pipe with sintered wick

In order to study reasonable sintering technological parameters and appropriate copper powder size range of micro heat pipe (MHP) with the sintered wick, the forming principle of copper powders in wicks and MHP’s heat transfer capabilities were first analyzed, then copper powders with different cell sizes and dispersions were sintered in RXL-12-11 resistance furnace under the protection of the hydrogen at different sintering temperatures for different durations of sintering time, and finally the sintered wicks’ scanning electron microscope (SEM) images and their heat transfer capabilities were analyzed. The results indicate that the wick sintered with copper powders of larger cell size or smaller size range has better sintering properties and larger heat transfer capabilities; and that the increase of either sintering temperatures or sintering time also helps to improve the wick’s sintering properties and heat transfer capabilities, and the former affects more obviously than the latter. Considering both its manufacturing cost and performance requirements, it is recommended that copper powders with the size range of 140–170 μm are sintered at 900–950°C for 30–60 min in practical manufacturing. In addition, two approaches to improve wick’s porosity are also proposed through theoretical analysis, which suggests that the larger the wick’s porosity, the better the heat transfer capabilities of the MHP.     

Development of sintered Ni-Cu wicks for loop heat pipes

The present study fabricated a series of capillary wicks for loop heat pipes (LHPs), using two different methods, the cold-pressing sintering and direct loose sintering, and experimentally investigated the effect of different methods, compositions and sintering parameters on their properties in terms of porosity, permeability and pore radius. Porosity and pore radius were measured by the Archimedes method and Scanning Electron Microscope (SEM), respectively. Permeability of the wicks was compared by calculation using empirical equation. Results show that capillary wicks were successfully fabricated by using two different methods; the optimal capillary wick was found to be sintered at 650°C for 30 min, using direct loose sintering technique, with 90% nickel and 10% copper. The wicks could reach the porosity of 70.07% and the permeability of 10⁻¹³ m² order, with mean pore radius of 0.54 μm. Supported by Shandong Provincial Program of Science and Technology Development (Grant No. 2007GG1HZ06004)     

Fabrication and thermal performance of grooved-sintered wick heat pipe简

Some novel grooved-sintered composite wick heat pipes（GSHP） were developed for the electronic device cooling.The grooved-sintered wicks of GSHP were fabricated by the processes of oil-filled high-speed spin forming and solid state sintering.The wick could be divided into two parts for liquid capillary pumping flow：groove sintered zone and uniform sintered zone.Both of the thermal resistance network model and the maximum heat transfer capability model of GSHP were built.Compared with the theoretical values,the heat transfer limit and thermal resistance of GSHP were measured from three aspects：copper powder size,wick thickness and number of micro grooves.The results show that the wick thickness has the greatest effect on the thermal resistance of GSHP while the copper powder size has the most important influence on the heat transfer limit.Given certain copper powder size and wick thickness,the thermal resistance of GSHP can be the lowest when micro-groove number is about 55.     

非规则截面散热板内嵌热管的传热能力分析

对一种空间实验装置中电子箱热控制系统的关键热控元件——散热板内嵌热管的传热能力进行了热分析计算.采用热容热阻网络法,建立了非规则截面槽道热管的传热模型,在传热网络分析的基础上,以热管No.21和热管No.22为例,选取空间实验装置在最热工况下稳定运行和最冷工况下从启动到稳定运行两种实验边界条件,计算了热管的传热能力,并与西班牙IberEspacio热管公司提供的传热极限数据进行了比较.结果表明,全部内嵌热管都能在传热极限范围内可靠运行,其中最热工况和最冷工况下热管的最大传热能力分别为工作温度41.7℃时的74.9W·m和-9.3℃时的69.6W·m.     

Experimental study on start-up characteristics of loop heat pipes

Loop heat pipes (LHPs) are two-phase heat transfer devices which utilize theevaporation and condensation of the working fluid to transfer heat. It consists of anevaporator, a condenser, a compensation chamber (CC) and vapor and liquid lines. Fig. 1 shows the detailed structure of the evaporator, CC and condenser of a LHP.The basic principles of LHP were introduced in ref. [1]. When LHPs start to work, liquidis vaporized in the vapor grooves, the menisci formed in the wick develop c…     

微槽群散热器换热性能实验研究

对微槽群相变散热器的散热性能进行了实验研究,实验采用了混合工质2-Methylpentane和甲醇来强化系统的换热性能,当混合工质中x₁(2-Methylpentane)的摩尔分数为10%,x₂(甲醇)的摩尔分数为90%时,微槽群散热器的换热性能最优;将该种配比的混合工质分别应用于不同尺寸的微槽群相变散热器中,得出了优化的微槽群深宽尺寸比.实验结果表明,在同一散热热流密度下,与前人的工作相比,能使芯片表面温度降低10~20℃.其散热性能满足大功率高性能电子芯片的散热需求.     

Thermal performance of heat pipe with different micro-groove structures

Four kinds of micro heat pipe of trapezoidal groove wick structure with different numbers of grooves or aspect ratios were studied and compared about thermal transfer performances in order to optimize the manufacture of micro heat pipe with groove wick structure. The results show that these micro heat pipes have excellent performance in heat transfer; the equivalent thermal conductivity coefficient is two orders of magnitude compared with that of copper; the number and aspect ratio of grooves have a prominent effect on the performance of such thermal transfer. The optimum number of grooves is lower than 60 and the best aspect ratio is near to 1.5. The temperature and thermal transport rate are almost directly proportional relationship, but this relationship will be broken up suddenly when the critical heat flux is reached.     

可伸长弹性软薄膜的毛细黏附

软薄膜的毛细黏附问题在微机电系统(MEMS)、生物系统中大量存在,同时在薄膜的生产工艺中也至关重要。研究了任意形状的软薄膜在毛细力作用下的黏附,建立了相应的能量泛函,推导出了薄膜的挠度曲线以及相应的横截条件。并针对圆形软薄膜的毛细黏附,求解其挠曲线、横截条件,从而得到其临界黏附半径。计算中引入了表征黏附半径以及表面张力、薄膜张力组合的无量纲参数,得到了薄膜能够发生毛细黏附的参数临界值。这些分析对于工程设计,以及MEMS、生物系统的毛细黏附等有一定的参考价值。     

水平埋管周围土壤温度场数值模拟研究

建立了应用于地源热泵系统的水平埋管的传热数学模型,并采用 ANSYS 软件模拟了埋深为 3 m 的水平埋管在冬夏运行工况下周围土壤的温度场变化。根据选取的特定时间比较了单管和双管水平埋管在相同工况下周围土壤温度场,得出各自的影响半径,为水平埋管换热器的埋设提供了参考。     

热管用于半导体致冷器的实验研究

本文作者为半导休致冷器设计了一种低温铝氨热管，并对其处于自然对流和强迫顺掠散热工况下的传热特性作了研究。半导体致冷器利用热管散热具有无可比拟的优点，目前的半导体致冷器的制造工艺条件，为其广泛应用带来光明的前景；本文指出：热管用于半导体致冷器的关键在于热管同电堆的耦合关系和结构设计。     

永磁微加速度开关设计与仿真

基于永磁铁磁力随位移的非线性变化特性,提出了一种新型磁力微加速度开关设计方案．建立了含有永磁力、气膜阻尼力、表面接触力、惯性力的开关系统动力学分析模型,给出了质量块在开关多种工作状态下的运动微分方程．对开关工作过程中质量块位置、永磁力、空气阻尼力、质量块与触点接触力等参数的变化规律进行了仿真,结果表明：该设计可以受控于加速度门限完成闭合-断开功能;微开关系统阻尼由质量块与封装外壳间隙厚度决定,为一变阻尼系统;开关闭合时电接触可靠性取决于质量块对触点的压力;开关闭合和截止所需的激励加速度门限值受永磁铁磁力和支撑梁刚度参数的控制．     

微操作力提升系统控制策略实验研究

为了改进微操作力提升系统的性能,设计了一种新型的末端操作器,分析了末端操作器的工作原理,提出了适应操作者操作特性的速度和位移增量2种控制策略,并基于dSPACE实验平台对微操作力提升系统进行了实验研究.实验结果表明:速度控制策略和位移增量控制策略均可行,操作者施加较小的操作力,提升系统就能顺应人的操作升降负载,能够满足操作者提升操作的柔顺行要求.     

一种新型含萘环结构高耐热型环氧树脂的合成

以1-萘酚和二环戊二烯（DCPD）为主要原料合成了一种新型含萘环和二环戊二烯环结构的环氧树脂.其结构通过傅里叶变换红外光谱(FTIR)、核磁共振波谱(NMR)、质谱(MS)和凝胶渗透色谱(GPC)表征确定，环氧值经盐酸 丙酮法测定为0.351.同4,4-二氨基二苯基砜（DDS）固化后所得固化产物的物理性能用动态热机械分析(DMTA)和热重分析(TGA)进行了表征.研究结果表明，固化产物具有高的玻璃化转变温度（tg=236.2 ℃）和热稳定性.由于憎水性的萘环结构和环戊二烯环的引入，固化产物也表现出良好的耐水性.     

大功率LED冷却用平板热管散热器的实验研究

对一种新型平板热管散热器冷却大功率LED芯片阵列进行实验研究。在自然对流冷却条件下,分析了平板热管散热器的启动特性、均温特性以及通电电流、倾角对其传热性能的影响。利用热电转换方法得到LED芯片的结温变化。实验结果表明:平板热管散热器的总热阻在0.3053～0.3425℃/W间,且散热器整体温度分布均匀合理,具有很强的散热能力;LED结温在47.9～59.0℃间,远低于110℃。     

直膨式地源热泵单U埋地换热器传热数值模拟

针对直接膨胀式地源热泵单U埋地换热器的传热特性,建立换热器及周围土壤温度场的数学物理模型.模拟计算分析制冷剂进口温度、钻孔几何尺寸与回填材料等因素对单U埋地换热器周围土壤温度的影响.研究结果为合理设计直接膨胀式地源热泵提供了理论参考.     

周期式作业热处理电炉的节能设计

分析了现有周期式作业热处理电炉的能耗组成并提出了一种节能的结构设计。     

基于电热模拟法的热管散热器传热研究与仿真

运用电热模拟法对一种热管式芯片散热器的各项传热热阻进行分析,建立了该热管散热器在强制风冷条件下的电网络传热模型,导出了总传热能力的理论计算公式;运用CFD软件ICEPAK对某一设计计算实例进行仿真,模拟结果与理论值基本吻合,验证了所建电网络模型的基本合理性。     

一种新型铝塑复合管卷绕机的工作原理

本文改进设计了铝塑复合管生产线卷绕机的卷绕装置,研制了一台卷管筒能够自动伸缩的新疆卷绕机。     

同井回灌地下水源热泵热力特性分析

同井回灌地下水源热泵抽水和回灌在含水层同一径向位置不同深度处同时发生,增加了热贯通的可能性,其热力特性分析尤为重要.文章首次建立了单一介质承压含水层中定流量同井回灌地下水源热泵冬季运行地下水换热数学模型,并针对典型的细沙含水层进行了数值求解.经过一个冬季的制热运行,抽水平均温度降低了3.6℃.由于对流和热弥散的存在,同井回灌地下水源热泵热影响范围达到了74 m.因此对于地下水初始温度在13℃以上的地区,同井回灌地下水源热泵是适宜的,较大的热影响范围也使得单口抽灌同井具有承担大负荷的能力.     

A novel experimental setup with sand trunk for heat extraction of geothermal heat exchanger

A novel experimental setup was developed to study the heat extraction of geothermal heat exchanger （GHE） in different operational modes under adiabatic and isothermal boundaries. The experimental setup consists of a sand trunk, a tailored water chiller, a natural cold source unit, two water boxes containing hot water and cool water, and a data acquisition system. The experimental results indicate that the volume flow rate of the entering water is a main factor affecting the heat extraction; furthermore, the heat extraction value per meter pipe decreases gradually along the heat extraction pipe and increases with the increase of the incoming water volume flow rate. Therefore, this novel experimental setup may be helpful to further study the operation performance of GHE in different types of soil.