共查询到17条相似文献,搜索用时 140 毫秒
1.
2.
本文建立了小型平板CPL蒸发器毛细多孔芯内汽液两相流动与传热的模型以及金属外壁和工质区的导热模型,并进行耦合求解.分析了金属侧壁效应对蒸发器性能的影响,提出小型平板CPL存在着侧壁效应传热极限.数值结果表明,工质蒸发发生在多孔芯加热表面附近,蒸发器采用单一金属外壁时由于侧壁效应导致系统传热极限低,而上壁采用导热系数大,侧壁及下壁采用导热系数小的新型结构能够明显的提高系统的传热能力,同时使加热表面的温度维持在较低的水平. 相似文献
3.
4.
环路热管吸液芯毛细抽吸特性研究 总被引:1,自引:0,他引:1
采用计算机记录毛细抽吸量实时变化曲线的方法,研究了环路热管吸液芯对不同工质的毛细抽吸特性,结果表明所有的吸液芯毛细抽吸过程均可分阶段采用玻耳兹曼方程进行描述,其误差在启动阶段和稳健抽吸阶段分别在5%和1%以内。工质的表面张力越大、密度越大,吸液芯的毛细抽吸量就越大;工质的表面张力越大、黏度越小,毛细抽吸速度越大。对孔隙率为45%~56%的吸液芯进行毛细抽吸实验发现,随着孔隙率的增大,抽吸速度和毛细抽吸量均随之增大,可见适当提高吸液芯的孔隙率有助于提高环路热管的性能。 相似文献
5.
《工程热物理学报》2021,42(6):1531-1537
如何在有限空间内提高吸液芯的毛细力的同时降低气液流动阻力成为制备超薄热管的关键问题。丝网是一种常用的热管吸液芯结构,当其用于超薄热管时,因厚度较大及毛细力较小而受到限制。为解决这一问题,本文采用电化学沉积法对铜网进行梯度结构修饰。文章对三种不同规格的铜网进行试验,探究不同反应条件对形貌及毛细性能的影响。结果表明,随着反应时间及电流的增加,修饰结构梯度幅度增大,毛细性能增强。以乙醇为工质时,修饰后的最大吸液高度为62.5 mm。与多尺度复合烧结铜粉毛细芯结构相比,在相同的毛细性能条件下,梯度修饰丝网在厚度上减小了 90%,从而为其在超薄热管中的使用奠定了基础。 相似文献
6.
7.
工质热物性显著影响脉动热管的流动与传热特性。本文通过理论计算及实验研究,定性分析了工质热物性对临界直径、毛细滞后阻力、启动运行及传热极限等方面的影响。研究表明,为保证脉动热管的运行性能,在设计阶段应综合考虑工质、管材及管径大小等因素。首先,根据使用场合的热流密度及运行温度高低合理选取工质种类;然后,选用合适的管壁材料,尽可能减少液塞与管壁之间前、后接触角不同引起的毛细滞后阻力;最后,确定管内直径范围。本文工作旨在为脉动热管的设计和选用提供一些依据和参考。 相似文献
8.
9.
本文描述了一种新型的太阳能热管喷射式制冷系统。其中热管吸液芯分别采用普通不锈钢丝和反向槽道毛细结构,分析其工作性能。另外为了获得更好的系统COP值,选择四种适合热管工作的工质进行计算,分析它们在采用前述两种吸液芯时的工作情况。研究表明由于反向槽道毛细结构可使工质流动压降更低,增强传热,当系统发生温度为70℃左右时,该系统具有更好的运行性能。而且此系统可有效利用太阳能,该系统若能与建筑复合,则具有广阔的应用前景。 相似文献
10.
11.
12.
The design and test results for a capillary pumped loop (CPL) for thermal management of up to 210 W at the source and heat transfer over a distance of 1 m are discussed. The design configuration of the CPL evaporator consists of an internally grooved aluminum evaporator, 31.70-mm outer diameter and 500-mm long, fitted with a porous ultra-high molecular weight polyethylene wick, 8- to 15-μm pore radius, and 38% porous volume. Heat was transferred using a stainless steel tube of 4.5-mm internal diameter for vapor and liquid lines. High-grade acetone (99.99% pure) was used as the heat transfer fluid inside the loop. In the tests, thermal characteristics of the CPL were specifically studied with respect to the temperature control capability using an active thermal device on the reservoir and to the start-up process through pressure priming of the capillary evaporator. The loop was able to start-up successfully at both low and high heat loads, although proper priming of the wick structure before start-up was necessary to attain low evaporator temperatures during steady-state operation. While maintaining constant reservoir temperature through active means, the loop was able to control evaporator temperature within 55 ± 3°C, even with changing input heat from 30 to 210 W. Total thermal resistance from the evaporator surface to the surroundings was 0.19° to 1.15° C/W with the minimum value achieved at the maximum heat load of 210 W. This study is intended to illustrate the thermal potential of the CPL as an effective temperature control device in automotive applications. 相似文献
13.
14.
分析了小型平板CPL蒸发器毛细多孔芯上下表面温差对启动的影响,建立了蒸发器满液启动的数学模型.结果表明,对不同的金属外壁,多孔芯上下表面平均温差存在一个最大值,铜壁时,温差较小,侧壁效应明显;采用不锈钢壁及上壁铜、侧壁下壁不锈钢时,温差大,侧壁效应小;采用不锈钢外壁时蒸发器加热面的温度过高.上壁采用导热系数大、侧壁下壁为导热系数小的金属对小型平板CPL蒸发器的正常启动以及降低加热表面温度非常有利. 相似文献
15.
In this paper, it was investigated experimentally that the effect of different kinds of working fluid on the thermal performance of evaporator with capillary wick consisted by multilayered sintered copper mesh under different electric field strengths at the operating pressure of 1.01 × 105 Pa R141b and R123 were used as the working fluids. The electric field strength in this study was in the range of 0kV/m–1600 kV/m, respectively. The experimental results showed that the applied electric field strength has significant effect on heat transfer characteristic. The heat transfer enhancement effects increased with the increase of the electric field. Under the applied electric field strength, the maximum heat transfer enhancement factors could reach as high as 1.5 and 1.32 for the two kinds of working fluids in the experiment. 相似文献
16.
As an example of a coupled gas-phase diffusion flame with porous media flow, a candle burning model with a porous wick is offered in this paper. The porous media analysis includes capillarity-induced liquid flow, liquid vaporisation, vapour motion and re-condensation and multi-phase heat transfer. Coupling with the gas phase flame is through the conservation of mass, momentum and energy at the wick surface. The steady state solutions obtained not only yield the flame structure but also the detailed flow pattern and saturation distributions inside the wick. One of the novel features of the present model is the capability to address the self-trimming phenomena of candle burning. The self-trimming wick length and the associated flame characteristics have been computed as a function of gravity level, wick permeability and wick diameter. 相似文献