一种振荡热管换热器热性能的研究

设计了一种振荡热管换热器,将其内插于太阳能集热器中,应用于蓄能型内插热管式太阳能热水系统,根据太阳辐射强度切换工作模型,可实现对太阳能的分季节最大化利用。搭建了蓄能型振荡热管换热器性能试验台,对充灌工质分别为R134a、乙醇/水、丙酮/水的振荡热管换热器在不同加热功率下启动时间、水侧温升和热阻等性能进行研究。结果表明:无论振荡热管换热器内充灌哪种工质,热管的启动时间都随着加热功率的增大而减小;相似环境温度下,充灌不同工质的振荡热管换热器的热阻都随着加热功率的增大而减小;在相同的环境温度下,充灌不同工质的振荡热管换热器的循环水温都会随着加热功率的增大而升高,充灌R134a的振荡热管换热器的循环水温增幅最大。     

振荡热管传热性能的试验设计与多因素分析

振荡热管的传热受许多因素的影响,其传热性能与因素间的关系是复杂和非线性的。采用统计方法分析铜一水闭合回路振荡热管传热性能与充液率、倾角、热量输入间关系。首先应用中心复合设计对试验进行安排,然后采用最小二乘法拟合试验变量与响应间关系,最后采用方差分析研究3个因素及其交互影响的程度。结果显示：二阶方程模型较好地反映了传热功率与影响因素间的关系;3个因素对传热功率的影响都是显著的,其中倾角的影响最为显著,但它们的交互影响不明显;在研究的范围内,最佳充液率和最佳倾角随加热水流量的增大均有所增加。     

热管喷射制冷循环工质的研究

文章研究了水、甲醇等6种工质在热管喷射式制冷循环中的工作特性。计算结果表明，工质的冷凝温度对系统COP的影响比较大，在发生温度一定的情况下，较低的冷凝温度和较高的蒸发温度能有效提高系统的COP，在各种运行条件下，甲醇、R11、R123等工质有较高的COP。     

氨工质平板式环路热管的传热性能研究

为了解决平板式蒸发器环路热管面对高集成电子元器件在较长传热距离下的散热能力不足等问题,本文采用更大面积的毛细芯和蒸发器,研制了一个传热距离达到1.6m的氨-不锈钢环路热管系统并进行了大量实验.实验过程中,加热壁面温度控制在70℃以下.实验结果表明,在热沉温度为-10℃的情况下,该环路热管可以在2.5W到180 W的热负...     

以R32和R245fa为工质的重力热管传热特性

对以R32和R245fa为工质的长3m、管内径为40mm、管外径为44mm的重力热管开展了传热性能实验研究。热源为恒温水浴,冷源为固定进口温度和流量的冷水。实验得出了不同热源温度下的热管传热负荷、工质蒸发换热系数和冷凝换热系数,并与经典拟合公式的预测值进行了对比。实验分析对比表明,R32更适宜工作在热源温度为常温到50℃的工况,R245fa更适合工作在50~100℃的热管工况。     

采用混合工质的热声驱动脉管制冷实验研究

在计算了惰性气体二元混合工质的热力学参数之后,采用氦-氩混合气体作为工质来提高热声驱动脉管制冷的性能。实验结果表明,热声驱动脉管制冷机采用适当配比的氦-氩工质可获得比纯氦更加优越的制冷性能。     

大功率集成LED热管散热器的传热性能

针对大功率集成LED单位热流密度高的特点,提出一种新型的翅片式重力热管散热器,并对其传热性能进行了实验研究,讨论了加热功率和充液率对散热器传热性能的影响。实验结果表明:在加热功率为150W、散热热流密度为37.5W/cm2时,翅片式重力热管散热器的系统热阻在0.08～0.33K/W,此时加热表面温度低于80℃,冷凝段管壁温度相差不超过3℃。该散热器不仅具有良好的均温性,且在工况变化时能快速重新达到稳定,满足大功率LED的散热需求。     

热环非共沸循环工质的优选

本文在对一种新型热管－泵或风机驱动的动力型分离式热管（简称热环）进行简要介绍的基础上,对热环应用于变温冷热源进所需的非共混混合工质的要求,优选方法进行了研究,并为造纸,食品等行业的典型工况优选了一组非共沸循环工质。     

混合工质脉管制冷机性能的数值模拟

开发了适用于混合工质的脉管制冷机的计算程序，利用此程序对应用混合工质提高脉管制冷机的制冷性能进行了研究，发现当混合工质采用氦气和氢气，且处于合适的配比下，可以进一步改进脉管制冷机的制冷性能，给出了当混合工质最佳配比时，脉管制冷机内热力参数的瞬时变化及一周期的循环参数，用该计算程序可以获得混合工质脉管制冷机内复杂过程的详细信息，为制冷机设计和改进提供依据。     

一种新型高温热泵混合工质的循环性能

对一种ODP(臭氧破坏势)为零的新型环保非共沸混合工质M1,在冷凝温度范围为80~110°C、循环温升为45°C的高温热泵工况下,进行了循环性能的理论和实验研究。理论循环性能分析表明,M1的综合性能优于传统工质CFC114;实验结果表明,M1系统的制热量Q和循环性能系数COP随工况温度的升高而提高。实验中,M1的最高平均冷凝温度达到102.3°C,相应热输出温度为103.0°C,冷凝压力和排气温度分别为1.951 MPa和119.0°C,都在安全应用的限制范围内。     

环路型脉动热管的工质流动和传热特性实验研究

建立了部分可视化的环路型铜-乙醇脉动热管试验台,研究了充液率、倾斜角度、环路数目等因素对脉动热管传热性能的影响。结果表明:不能形成脉动效应时工质的流型是间歇振动,形成脉动效应时工质的流型是弹状流或环状流;最佳倾角为70°~90,°最佳充液率在50%左右;热阻随着环路数目的增加而减小。     

Experimental research on heat transfer of pulsating heat pipe

Experimental research was conducted to understand heat transfer characteristic of pulsating heat pipe in this paper, and the PHP is made of high quality glass capillary tube. Under different fill ratio, heat transfer rate and many other influence factors, the flow patterns were observed in the start-up, transition and stable stage. The effects of heating position on heat transfer were discussed. The experimental results indicate that no annular flow appears in top heating condition. Under different fall ratios and heat transfer rate, the flow pattern in PHP is transferred from bulk flow to semi-annular flow and annular flow, and the performance of heat transfer is improved for down heating case. The experimental results indicate that the total heat resistant of PHP is increased with fill ratio, and heat transfer rate achieves optimum at filling rate 50%. But for pulsating heat pipe with changing diameters the thermal resistance is higher than that with uniform diameters.     

Heat transfer performance of a flexible looped heat pipe using R134a as a working fluid: Proposal for a method to predict the maximum heat transfer rate of FLHP

This paper presents the heat transfer performance of a Flexible Looped Heat Pipe (FLHP) using R134a as a working fluid. In our evaluation system, an evaporator and a condenser are connected by long flexible tubes with a diameter of 3 mm, and the total piping length of this looped heat pipe system is approximately 7500 mm. We selected porous Teflon with an effective pore diameter of 2r_cw = 1.2 µm to overcome high gravitational heads. Elevation of the evaporator above the condenser ΔH = H_e ? H_c) was changed in three conditions [ Top heat mode (ΔH = +1 m), Horizontal mode (ΔH = 0), Bottom heat mode (ΔH = ?1 m)] considering the terrestrial application and the influence of gravity on the FLHP performance was investigated. FLHP provided high thermal transport capacities over long distances through small cross‐sectional flexible tubes compared with conventional heat pipes. We also proposed an analysis method to predict the maximum heat transfer rate of FLHP. © 2003 Wiley Periodicals, Inc. Heat Trans Asian Res, 32(4): 306–318, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.10093     

脉动热管的研究综述

自从上世纪九十年代初期脉动热管问世以来,对它的研究主要是建立数学模型的理论研究,还有关于运行机理的可视化,以及充液率、管径、加热端与冷却端相对位置、工质、不凝性气体等参数对脉动热管的热性能影响的实验研究。对于脉动热管优化和设计的完整方案还需要进一步的研究。文中主要介绍了有关脉动热管研究的近期进展,并对脉动热管的进一步研究和在电子冷却中的应用做了展望。     

Flower-type pulsating heat pipe for a solar collector

Inspired by the sunflower, we report a new structure of a solar collector that integrates a pulsating heat pipe (PHP) into a flat-plate collector. The proposed flower-type PHP solar collector is designed after a sunflower with petals that absorb sunlight and transfer nutrients to the stem after photosynthesis. The evaporator section adopts the shape of a flower to absorb sunlight fully, and the condenser section is rolled into a cylinder and placed in the lower part of the structure. A systematic experimental study is conducted upon start-up, and the performance characteristics, with acetone as the working fluid, are evaluated. We also did a heat loss analysis, which has a deviation of 8%. The effects of the mass flow rate of cooling water, filling ratio, length of the condenser section, and solar intensity are assessed. As the temperature of the heat absorber plate increases, the thermal resistance of the PHP can decrease to a minimum of 0.14°C/W. Under sunny weather conditions, the instantaneous thermal efficiency of the system with a filling ratio of 50% reaches 50%. Besides, we discussed the unstable operation conditions and possible dryout phenomenon that happened inside the PHP.     

氧化石墨烯对脉动热管传热性能的影响

实验选用外径为4mm、内径为2mm的铜质脉动热管研究了氧化石墨烯对以去离子水和体积分数为50%的乙醇溶液为工质的脉动热管传热性能的影响。实验分别采用加有少量氧化石墨烯的去离子水溶液(简称氧化石墨烯水溶液)和体积分数为50%的乙醇溶液(简称氧化石墨烯乙醇溶液),氧化石墨烯质量分数均为0.03%。实验发现：氧化石墨烯对以去离子水为工质的脉动热管传热性能具有强化作用,对以体积分数为50%的乙醇溶液为工质的脉动热管传热性能的影响较差,但都和脉动热管的加热功率密切相关。对于以去离子水为工质的脉动热管,在加热功率低于20W时,氧化石墨烯对脉动热管的强化作用较弱；当加热功率在30～60W之间时,氧化石墨烯对脉动热管的强化作用较强,在3.71～11.33%之间,且强化作用随加热功率的增大呈逐渐增强趋势；但随着功率继续增大,氧化石墨烯的强化作用逐渐减弱,当加热功率达到80W后,热管传热性能减弱,原因可能是氧化石墨烯颗粒出现了沉降现象。     

Effect of amount of fluid charge in thermal performance of loop heat pipe

Loop heat pipes (LHPs) are two‐phase thermal control system, which works only by heat from its cooling target. In order to utilize the LHPs in various fields, it is required to be smaller, more reliable, and higher in performance. In the present study, a miniature LHP has been fabricated, and the effect of the amount of working fluid charged on thermal performance of the LHPs has been investigated. Tests were conducted including start‐up, and power step up, as function of the amount of working fluid. The test results showed that under‐charging the working fluid caused start‐up failure, while over‐charging the working fluid made the LHP less stable. © 2010 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/htj.20306     

Experimental investigations on operating characteristics of a closed loop pulsating heat pipe

The operating mechanism of the pulsating heat pipe (PHP) is not well understood and the present technology cannot predict required design parameters for a given task. The aim of research work presented in this paper is to better understand the operation regimes of the PHP through experimental investigations. A series of experiments were conducted on a closed loop PHP with 5 turns made of copper capillary tube of 2 mm in inner diameter. Two different working fluids viz. ethanol and acetone were employed. The operating characteristics were studied for the variation of heat input, filling ratio (FR) and inclination angle of the tested device. The results strongly demonstrate the effect of the filling ratio of the working fluid on the operational stability and heat transfer capability of the device. Important insight into the operational characteristics of PHP has been obtained.     

太阳能用低温无机工质热管的试验方法

阐述了以无机元素为传热工质,工作范围为40～200℃的太阳能用低温热管的试验方法。试验方法给出了试验条件、要求和仪器设备。通过对数千支热管试验数据的归纳、整理、分析,确定了热管的启动性能,等温性能和耐高、低温性能等技术指标,经过在太阳能热水器和太阳能集热工程中的实际运行表明,可以满足使用要求。     

An experimental investigation on heat transfer performance of nanofluid pulsating heat pipe

The effect of SiO2 particles on heat transfer performance of a pulsating heat pipe(PHP) was investigated experimentally.DI water was used as the base fluid and contrast medium for the PHP.In order to study and measure the character,there are SiO2 /H2 O nanofluids with different concentration and applying with various heating powers during the experiment investigation.According to the experimental result,the high fraction of SiO2 /H2 O will deteriorate the performance of PHP compared with DI water,i.e.the thermal resistance and the temperature of evaporation section increases.It is in contrary in the case of low fraction of SiO2 /H2 O.Finally,the comparison of the thermal performances between the normal operation system and the static settlement system is given.It is found that both the thermal resistance of nanofluid PHP and the temperature of the evaporation section increase after standing for a period,and it is the same trend for the temperature fluctuation at the identical heating power for PHP.