纳米流体对脉动热管最佳充液率的影响

本文通过实验着重研究了一脉动热管在不同充液率下充入体积分数为0.05%、粒径为80 nm的柱状Al₂O₃纳米流体后传热性能的变化情况。结果表明:1)该纳米流体可以明显强化本实验中的脉动热管传热性能,但随着输入功率的增加,强化作用减弱;2)在充入该纳米流体后,脉动热管的最佳充液率由40%降为30%;3)充液率影响纳米流体的强化作用,总的来说充液率越高纳米流体的强化作用越弱。     

振荡流热管自激强化传热特性实验研究

针对回路型振荡流热管,从自激强化(被动强化)传热的角度出发,通过实验对比分析,分别研究了热管采用非均匀截面结构、管内工质为Cu-H2O纳米流体以及热管采用不等径结构时的强化传热特性.实验研究结果表明:采用上述三种强化传热的方法,在特定条件下,都分别不同程度地起到了强化传热的效果,为振荡流热管强化传热的进一步研究奠定了基础.     

环路热管技术的研究热点和发展趋势

综述了环路热管技术近20年的主要理论和实验研究内容,分析了当前的研究热点,包括环路热管启动特性研究,以温度滞后和温度波动现象为代表的暂态特性研究,新型毛细芯的研制和毛细结构的优化,蒸发器内的强化传热和可视化研究,以及高级环路热管、混合冷却环路、多蒸发器混合环路热管、低温环路热管等新型环路热管技术。     

纳米流体在热管中应用的研究进展

随着纳米流体用于换热器的强化换热,纳米流体热管换热器的研究逐步扩展到各个领域,从航天到化工,从电子到能源。纳米流体热管由于表面温度低,较高的传热系数和较小的热阻,受到了广泛的关注。文中总结了纳米流体热管国内外的最新研究进展。     

纳米流体振荡热管内部流动和传热特性

本文以纳米流体和去离子水的振荡热管作为研究对象,通过实验的方法,运用可视化的加热与观测手段,对比纳米流体和去离子水振荡热管的内部工质流型和冷热端温差,发现纳米颗粒体积浓度达到一定浓度后,相对于去离子水,纳米流体可以降低振荡热管的下极限热流,提高上极限热流,而后者足利用纳米流体为工质改进振荡热管性能主要特点,内在物理实质是纳米流体具有明显不同的流型转变.     

小角度下自湿润流体重力热管传热特性

本文实验研究了工质分别为水和自湿润流体(质量分数5%正丁醇水溶液)的两种重力热管在微小倾斜角度下的传热特性,对比两种热管的传热性能以探究自湿润流体在小角度下对热管性能的影响。实验所采用的各倾角分别为0°,1°,3°,5°,7°和10°。实验结果表明:在倾角为0°时,自湿润流体重力热管相比水重力热管热阻更小、传热极限更大,因此具有更好的传热性能;在其他小的倾角下,自湿润流体同样显著提高了重力热管的传热极限,但也使热阻有所增大。     

小型平板CPL蒸发器优化设计研究

本文建立了小型平板CPL蒸发器二维的整场数学模型,并用SIMPLE程序对蒸发器进行整场耦合求解.研究表明,平板型CPL蒸发器存在着侧壁效应传热极限,减小液体补偿腔的高度,减小侧壁以及下壁的厚度以及增加毛细芯的高度可以提高CPL的传热能力.     

纳米流体脉动热管的流动与传热性能研究

建立了纳米流体脉动热管的分析模型,将相变传热项合理引入了汽塞能量微分方程;液塞动量方程中考虑了剪切力的影响;纳米流体的物性采用了当量处理方法.采用数值迭代方法进行了求解,得到了汽塞压力、温度、质量的变化波形,分析了波形的频率,进而解释了初始条件、重力等对脉动热管的流动与传热影响的机理.     

以R600A为工质的分离式热管的实验研究

对分离式热管的整体热量传递特性进行了实验研究。以蛇形翅片管作为冷凝段和蒸发段进行热管实验,探讨了蒸发器进风面风温及分离式热管蒸发器与冷凝器之间高度差、工质充注量对分离式热管的影响。实验表明,随着蒸发器进风温度的升高,蒸发器与冷凝器换热系数都是呈现先增大后减小的趋势。在冷凝端进风温度恒定为16.55℃、蒸发端进风温度低于60℃时,以R600A为工质的分离式热管的传热量曲线近似于二次曲线,蒸发端进风温度高于60℃时,其传热量曲线近似于一条直线。加大充液率及增加蒸发器与冷凝器的高度差,分离式热管的传热能力均会得到提高。     

热管辐射器在高空环境中的应用研究

本文建立了热管辐射器传热、散热过程的数学模型,通过数值模拟计算对热管辐射器肋片参数的优化进行了分析.考察了循环流体温度和空间等效热沉温度对热管辐射器散热能力的影响,所得结果对热管辐射器在高空环境中浮空器设备舱热控制应用具有参考意义.     

Transient lumped heat pipe analyses

A transient lumped heat pipe formulation for conventional heat pipes is presented and the lumped analytical solutions for different boundary conditions at the evaporator and condenser are given. For high temperature heat pipes with a radiative boundary condition at the condenser, a nonlinear ordinary differential equation is solved. In an attempt to reduce computer demands, a transient lumped conductive model has been developed for noncondensible gas-loaded heat pipes. The lumped flat-front transient model was extended by accounting for axial heat conduction across the sharp vapor-gas interface. The analytical solutions for conventional and gas-loaded heat pipes were compared with the corresponding numerical results of the full two-dimensional conservation equations and experimental data, with good agreement.     

Heat pipe heat storage performance

Heat storage offers essential thermal energy saving for heating. A ground heat store equipped with heat pipes connecting it with a heat source and user is considered in the paper. It has been shown that such a heat exchanging system along with a batch energy source meets, to a considerable extent, house heating requirements.     

Advanced industrial ceramic heat pipe recuperators

This paper summarizes the results of an investigation involving the use of ceramic heat pipe recuperators for high-temperature heat recovery from industrial furnaces. The function of the recuperator is to preheat combustion air with furnace exhaust gas. To maximize fuel savings, a very high air preheat temperature is desirable; this necessitates the use of ceramic elements in the recuperator.The heat pipe recuperator comprises a bundle of individual ceramic heat pipes acting in concert, with a partition separating the air and exhaust gas flow streams. The heat pipe fluid is a liquid metal. The ceramic heat pipe recuperator concept offers several advantages as compared to tubular type ceramic recuperators. Because each heat pipe is essentially an independent heat exchanger, the failure of a single tube does not compromise recuperator integrity and has only a minimal effect on overall heat exchanger performance. This independent element characteristic also enables easier replacement of individual heat pipes in the recuperator. In addition, the heat pipe acts as an essentially isothermal heat transfer device, leading to a high thermodynamic efficiency.Cost estimates developed for heat pipe recuperator systems indicate favorable payback periods. Laboratory studies have demonstrated the feasibility of fabricating the required ceramic tubes, coating the inside of the tubes with CVD tungsten (which functions as both a protective layer and a heat pipe fluid wick), and sealing the heat pipe with an electron-beam-welded or vacuum-brazed end cap.     

微型热管传热极限的研究

热管技术已在电子设备散热领域得到广泛应用。热管的传热能力虽然很大,但不能无限加大热负荷。文中讨论了热管的主要极限如沸腾极限、毛细极限、粘性极限、声速极限、携带极限等的理论表达式,就一种实验用微槽平板热管进行了理论计算,得出了毛细极限是实验热管主要传热极限的结论。     

Heat pipe research and development in the Americas

The purpose of this paper is to present a review of the recent heat pipe research and development efforts in the Americas. After discussing the research and development of high performance monogroove, tapered artery, trapezoidally grooved, dual-slot, double wall artery, ceramic and other specially designed heat pipes, the transient modeling and testing efforts are reviewed for a variety of heat pipes that also includes variable conductance heat pipes and thermosyphons. The application of heat pipes to terrestrial systems is discussed for the heat recovery systems, Rankine and solar systems, fusion reactor core cooling and the thermal control of electronic equipment. The application of heat pipes to space systems includes the thermal control of space station and satellites, and the radiator design of large space power systems. Although many advances have been made in the past few years in the development of high heat transfer performance heat pipes, the heat pipe modeling efforts are not in step with the technological requirements.     

组合式热管换热器在热泵系统中的试验研究

采用组合式热管换热器作为生活浊水余热热泵热水器的热管蒸发器,并在试验台上进行了不同污水进口温度和不同污水流量的可视化试验,通过分析试验结果,发现组合式热管上升管和下降管的温差很大的现象,这与热管特性相矛盾。采用理论分析和实验相结合的方法,研究了热管中产生温差的原因。它主要是由于下降管压力损失较大,使热管工质在热管蒸发器中的滞留引起。     

微型热管的研究进展

微型热管是伴随微电子技术的发展而发展起来的一门新兴技术,是有效冷却高热流密度电子器件的主要途径之一。阐述常用的微型热管即脉动热管、微槽平板热管、环路热管的研究现状和进展,总结微型热管研究所面临的困难和挑战,指出微型热管的发展趋势,认为必将广泛应用于电子器件冷却、航空航天及计算机等领域。     

地源热泵耦合地埋管换热计算若干问题的研究

针对地质构造特点,进行地下一定深度的温度场测试;对耦合地埋管的换热设计计算中的若干问题进行了研究;在简化计算换热模型的基础上,在Excel上用VBA编写宏功能,得到实用的地埋管换热的工程设计计算方法,是一种工程易用的计算软件。同时将这种计算方法应用到了一个实际工程中,并对计算结果进行了验证。     

Visual study of the microdrop component in sodium vapor-inert gas mixtures in a heat pipe

The parameters (size, density, and velocity) of the microdrop component in the cooling zone of a heat pipe in Na + He and Na + Kr mixtures have been determined by visualization. It is found that particles in helium have an average size of 14 μm and concentration of 1.6 × 10⁴ cm^?3, while the corresponding values for krypton are 42 μm and 3 × 10³ cm^?3. The effect of microdrops as causes of nonequilibrium enhanced concentration of sodium trimers is analyzed. Such a concentration of trimers can explain the high IR absorption coefficients (above 0.9 μm), which were previously observed in heat pipes.