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1.
环路型脉动热管的工质流动和传热特性实验研究   总被引:13,自引:0,他引:13  
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。  相似文献
2.
倾斜角及充液率对脉动热管运行性能的影响   总被引:2,自引:0,他引:2  
在内径分别为1 mm和2 mm的细铜管弯曲而成的40弯头脉动热管试验装置上,采用R123、水和酒精为工作介质,研究了倾斜角及充液率对脉动热管传热性能的影响.结果表明:在相同的热负荷下,当倾斜角从+90°逐渐转到0°,最后转到-90°时,平均蒸发温度有不同程度的提高;在较低负荷下,倾斜角对运行性能的影响比较明显;对于多弯头数管状脉动热管,重力作用对其传热性能的影响仍然存在,但影响程度随着热负荷的增加及管内径的减小而减弱;最佳充液率范围与管内径、加热模式、热负荷及工质种类等因素有关,在工程应用中,最佳充液率可近似取管内总体积的55%左右.  相似文献
3.
A series of experiments were performed on three types of closed loop pulsating heat pipes(PHPs),intending toinvestigate various kinds of flow patterns,and to develop some improved configurations for the PHPs.Opticalvisualization results indicated that there might exist three flow patterns,i.e.bubble-liquid slug flow,semi-annularflow and annular flow,corresponding to different working conditions.For a given geometry and an adequate fillratio,the PHPs had the self-adjusting characteristic for the flow patterns(from slug flow to semi-annular and thento annular flow)to meet the demands of the increasing heat input.Two special configurations,one with alter-nately varying channel diameter,the other equipped with one section of thicker tube,were found to be advanta-geous in establishing and maintaining reliable circulation of the working fluid.The thermal performance of thePHPs was examined over a range of working conditions.Comparing with the normal PHP with uniform diameter,either of the improved PHPs exhibited higher thermal performance.  相似文献
4.
An experimental investigation is conducted to explore the heat-transport capability of pulsating heat pipes (PHP) working with functional thermal fluids (FS-39E microcapsule fluid and Al2O3 nano-fluid), by comparing them with pure water. The test tube is a four-turn pulsating heat pipe, made of a copper tube with an external diameter of 2.5 mm, and an inner diameter of 1.3 mm. The results show that the heat-transport capability of PHP can be enhanced by using FS-39E microcapsule fluid and Al2O3 nano-fluid as working fluid under specific conditions. When using vertical bottom heat mode, FS-39E microcapsule fluid is the best working fluid and its best concentration is 1 wt%; when using horizontal heat mode, Al2O3 nano-fluid is the best working fluid and its best concentration is 0.1 wt%.  相似文献
5.
在由内径分别为1 mm和2 mm的细铜管弯曲而成的2组40弯头开式回路脉动热管试验装置上,采用R123为工作介质,定性分析了充液率及加热方式对传热极限的影响,并将试验值与Katpradit传热极限关联式的计算值进行了比较,结果表明:随着充液率的提高,传热极限先增大而后减小,存在一个最佳充液率(约50%);在3种加热方式中,垂直底部加热有助于脉动热管取得较大的传热极限值,而垂直项部加热则对应较小的传热极限值.通过对Katpradit传热极限关联式进行适当修正,得到了新的试验关联式.  相似文献
6.
The paper presents the results of developing and investigating a compact cooler for electronics made on the basis of a closed loop pulsating heat pipe (CLPHP). The cooler is made of a copper tube 5.6 m long with OD of 2 mm and ID of 1.2 mm in the form a 3D spiral containing 17 turns. The device is equipped with a light copper radiator with a finning area of 1670 cm2, which was blown by an axial fan located inside the spiral. The thermal interface of the cooler situated in the heating zone is made of a copper plate with a thermocontact surface measuring 40 × 35 mm, which was in thermal contact with all the turns of the device. The cooler overall dimensions are 105 × 100 × 60 mm, its mass is 350 g.The operation of the cooler has been investigated with water, methanol and R141b as working fluids at a uniform and concentrated supply of a heat load in different heating modes. A reliable operation of the device has been demonstrated in the range of heat loads from 5 to 250 W. A minimum thermal resistance “heat source–ambient air” equal to 0.32 °C/W was attained with water and methanol as working fluids at a uniform heat load of 250 W. With a heat load concentrated on a section of the thermal interface limited by an area of 1 cm2, a minimum value of thermal resistance equal to 0.62 °C/W was attained at a heat load of 125 W when methanol was used as a working fluid.  相似文献
7.
林天轮  杨洪海 《节能》2010,29(8):22-25
设计加工1台脉动热管式换热器,用于夏季工况空调排风的余冷回收。通过实验,分析了风速、新排风温差等因素对余冷回收效率的影响,以及两侧压力损失随风速的变化情况。结果表明,余冷回收效率随新风、排风温差增大而升高,随风速的增大而降低。该换热器具有一定的优势,但还需进一步改进结构,以提高其效率。  相似文献
8.
A three-dimensional unsteady model of vapor–liquid two-phase flow and heat transfer in a flat-plate pulsating heat pipe (FP-PHP) is developed and numerically analyzed to study the thermal-hydrodynamic characteristics in two different configurations of FP-PHPs. The thermo-hydrodynamics characteristics under steady unidirectional circulation condition of the studied FP-PHPs are numerically investigated and discussed. The results indicate that the bubbly flow, slug flow and semi-annular/annular flow occur in the FP-PHP under the condition of steady unidirectional circulation, when the adjacent tubes of the FP-PHP become ‘upheaders’ and ‘downcomers’ of working fluid. The periodical oscillations of fluid temperature and vapor volume fraction are observed to be synchronous, while the temperature oscillation amplitude at adiabatic section is larger than that at condenser section but less than that at evaporator section. The increases in the heat load lead to the high temperature level and small integral equivalent thermal resistance of the FP-PHP. Additionally, compared with the traditional FP-PHP with uniform channels, the FP-PHP with micro grooves incorporated in the evaporator section is effective for the heat transfer enhancement and possesses a smaller thermal resistance at high heat loads.  相似文献
9.
This study develops an analytical model applicable for predicting the oscillatory motion of a pulsating heat pipe (PHP) with asymmetrical arrayed minichannel configuration. The analytic model takes into account the temperature difference between the average evaporating region and the average condensing region as the thermally driven force for the oscillatory motion. It is found that the dominant parameters affecting the PHP include configurations and dimensions of the flow channel, the number of turns, the filled liquid ratio, the frequency ratio, the operating temperature, and the temperature difference between the average evaporating region and the average condensing region are investigated in this study. The calculated results show that the closed-loop pulsating heat pipe with asymmetrical arrayed minichannel under lower number of turns, lower filled liquid ratio, higher operating temperature and higher temperature difference between the average evaporating region and the average condensing region for the frequency ratio of unity could attain a better performance of the oscillatory motions.  相似文献
10.
混合工质可为振荡热管带来独特的传热性能.比较甲醇、乙醇纯工质以及甲醇-乙醇混合工质振荡热管在不同充液率时的热阻随加热功率的变化情况,结果发现:在小充液率(45%)时甲醇-乙醇混合工质和乙醇振荡热管开始烧干时的加热功率高于甲醇工质振荡热管;在加热功率不是很大(低于65W)和大充液率(62%~90%)时,甲醇以及甲醇-乙醇混合工质振荡热管的传热性能优于乙醇振荡热管;在大加热功率(高于65W)和大充液率(62%~90%)时甲醇以及甲醇-乙醇混合工质振荡热管的热阻十分接近,均低于乙醇工质振荡热管的热阻,且热阻随着充液率的增加曲线变化越来越平缓.  相似文献
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