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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。 相似文献
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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。 相似文献
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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。 相似文献
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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. 相似文献
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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 2rcw = 1.2 µm to overcome high gravitational heads. Elevation of the evaporator above the condenser ΔH = He ? Hc) 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 相似文献
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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. 相似文献
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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。 相似文献
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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 相似文献
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Yu WANG 《Frontiers in Energy》2015,9(2):134
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. 相似文献
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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. 相似文献