共查询到19条相似文献,搜索用时 109 毫秒
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本文基于MEMS工艺研制了硅基微型脉动热管实验芯片,并搭建了热管流动与传热性能实验测试平台,高速可视化观测了热管内气液两相脉动行为特性与流型演化规律,并探索了工质脉动运行状态与热管传热性能间的内在联系。实验结果表明:微型脉动热管内部工质脉动运行主要包括三类要素:小幅脉动、大幅脉动与停滞,且这三种运行模式既可单独出现,也可间歇性共存;随着热负荷的升高,脉动热管内工质运行状态出现由停滞向大幅脉动的转变,导致热管传热性能大幅提升;微型脉动热管内的主要流型有泡状流、塞状流与环状流等,而由通道尺度效应引起的特征性喷射流现象诱发了通道内环状流向塞状流的演化. 相似文献
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喷嘴雾化特性实验研究 总被引:56,自引:0,他引:56
液体雾化是当前两相流研究中非常重要的课题,在农业、能源以及环境工程中具有广泛的应用价值,进行深入系统的研究具有重要意义。本文以空气、水为工质,使用马尔文粒度仪对单相和两相雾化器喷嘴的雾化特性进行了比较实验研究。测量了不同压力配比条件下液体雾化粒子的粒径分布,详细讨论了压力对于喷嘴雾化效果的影响。同时得出了两相流量与压力之间的变化规律。 相似文献
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微柱群阻力特性实验研究 总被引:1,自引:0,他引:1
以去离子水为工质,流经直径为0.5 aim,高度分别为1.0 mm、0.75 mm、0.5 mm和0.25 mm的圆柱组成的柱群板,其宽度与长宽分别为3.5 mm和40 mm,测量通道进出口压差及流量,研究微柱群内部分别在叉排和顺排时液体流动的阻力特性.研究表明,微柱群内流动阻力系数f,随Re数的增大而逐渐减小,当Re数大于500时,f基本不变;微柱高度和直径之间存在一个有利于流动的最佳比例,该值介于1到1.5之间;顺排微柱群的f明显小于叉排微柱群,其,值为叉排微柱群的0.5倍. 相似文献
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X. M. Zhang 《实验传热》2013,26(1):47-67
Experimental studies were performed on a pulsating heat pipe (PHP), consisting of a heating section, an adiabatic section, and a condensation section incorporating a heat sink. The capillary tube used in this study has an inside diameter of 1.18 mm and a wall thickness of 0.41 mm. The experiments were conducted under the condition of pure natural convection, for heating powers from 5 to 60 W, fill ratios from 60% to 90%. Three working fluids—FC-72, ethanol, and deionized water—were used. The thermal oscillation of the thin wall surface was recorded by a high-speed data acquisition system. Such thermal oscillation waves are random for some run cases due to the randomly distributed vapor plug and liquid slugs inside the PHP. The thermal oscillation amplitude is much smaller for FC-72, due to its lower surface tension, than for ethanol and water, while the oscillation cycle period for FC-72 is shorter than for the other two fluids, indicating the faster oscillation movement in the channels, possibly due to the lower latent heat of evaporation for FC-72. The unlooped PHP is not helpful for the fluid circulation and the PHP does not work. For the looped PHP, there is a minimum heating power that initiates the PHP working. Such minimum heating power is strongly dependent on the working fluid, and is considerably smaller for FC-72 compared with water. The optimal filling ratio is around 70% for all three working fluids. The looped PHP with water as working fluid provides better overall thermal performance once the heating power is greater than a minimum value. However, FC-72 is suggested to be used for low-heat-flux situations, due to its lower minimum heating power. 相似文献
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工质变比热条件下内燃机循环普适特性 总被引:4,自引:0,他引:4
用有限时间热力学的方法分析空气标准不可逆内燃机循环,导出了考虑工质变比热情况下,存在摩擦及传热损失时,由两个加热过程、两个放热过程和两个绝热过程组成的普适的空气标准不可逆内燃机循环的功率与压缩比、效率与压缩比以及功率和效率的最佳特性关系,同时由数值计算分析了工质变比热和循环过程对循环性能的影响特点,比较了工质恒、变比热时循环性能差异。所得结果包含了不可逆往复式Diesel、Otto、Brayton、Atkinson、Dual和Miller 循环的性能特性。 相似文献
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