共查询到20条相似文献,搜索用时 125 毫秒
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基于温度补偿原理和牛顿冷却定律,对电热法测量热功当量实验提出了2种散热修正方法,即温度补偿法和线性回归法.温度补偿法采用作图法,数据处理操作简单;而线性回归方法计算相对复杂,实验过程散热系数保持不变的假设也会给结果带来误差,但可以对实验结果的不确定度给出定量评估.基于此,针对不同的实验数据量和不同的数据采样间隔对实验结果进行了比较,给出了最佳方案. 相似文献
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采用稳态平板法测量不良导体的导热系数时,关键是得到稳态时不良导体的传热速率。根据稳态时传热速率与散热铝盘的散热速率相等,可以测定自然冷却过程中,稳态时散热铝盘温度T2所对应的冷却速率。基于Matlab软件,分析并绘制曲线直观反映出温度、时间、冷却速率三者之间的关系,用拟合法研究了不良导体导热系数随温度变化的关系。 相似文献
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文章记述了开展激光冷却气体原子研究的起步阶段,描述了推动文章作者从原子钟研究走向激光冷却气体原子研究的动力.在研究初期阶段,文章作者着重思考了激光冷却气体原子物理机制,如:积分球红移漫反射激光冷却气体原子的设想和利用光频移效应(交流斯塔克效应)激光冷却气体原子的物理思想.文章还描述了作者所在实验室用于激光冷却原子研究的原子束实验装置,并展示了几个物理实验结果.最后,文章还总结了经验和教训,深感起步艰辛和今日可贵,期盼光辉的未来. 相似文献
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简述了脉冲管制冷机研究现状和存在的问题 ,介绍了低温中心建立的脉冲管制冷机动态参数实验系统。通过对一典型脉冲管制冷机的动态参数的实验数据测量 ,分析了动态压力和质量流量之间的振幅和相位关系 ,首次在实验中发现了存在于脉冲管制冷机内部的直流现象 (DC-Flow)。指出该直流分量是脉冲管制冷机的一种损失 ,揭示了多路旁通进气方式可减小直流损失 ,提高脉冲管制冷机的效率。并从理论上分析了产生直流现象的根本原因 ,给出了直流分量的具体数值和大小。 相似文献
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LI Qiang ZHU Yuying HE Yunha WANG Xu LI Gong YU Jinku & SU Zhibin .Key Laboratory of Metastable Materials Science &Technology Yanshan University QinhuangdaO China .Department of Mechanical Engineering Yanshan University Qinhuangdao China .Department of Environmental & Chemical Engineering Yanshan University QinhuangdaO . China 《中国科学G辑(英文版)》2004,47(5):581-587
~~Undercooling and solidification of germanium melts studied by differential scanning calorimeter~~ 相似文献
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针对高热流密度激光介质高效散热与均匀冷却技术需求,设计并搭建了以去离子水为冷却工质的开式单喷嘴喷雾冷却实验平台,实验研究获得了不同热流密度(16~110 W/cm2)、不同冷却工质流量(200~300 mL/min)以及不同喷雾高度(15~25 mm)下单相喷雾冷却换热系数及其冷却均匀性效果。结果表明:该实验工况下,不同热流密度条件下喷雾高度及工质流量对于单相喷雾冷却换热效率及温度均匀性影响显著;喷雾高度15 mm、工质流量200 mL/min时获得最大对流换热系数为5.93 W/(cm2·K);喷雾高度15 mm、工质流量250 mL/min时面积20 mm×20 mm的热源表面温度均匀性最佳可优于0.6 ℃。 相似文献
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Mechanical effects of light on the Ξ-type three-level atom in a high-finesse optical cavity 下载免费PDF全文
A theoretical study is carried out for the modification and implication of the effect on the Ξ-type three level atom in a high-finesse optical cavity driven by light field including spontaneous emission and the cavity decay. Analytic expressions for the dipole force, the friction force, the optical potentials and the friction coefficient are obtained. Then the numerical and graphical methods are used to investigate the friction coefficient with the controlling parameters. It is shown that the friction coefficient is strongly dependent on the controlling parameters. The cooling rate can increase by one order of magnitude more than that of a two-level atomic system. The reason can be given using the dressed states and the Sisyphus cooling mechanism, which would stimulate further experimental investigations. 相似文献
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The objective of the current research deals with the experimental study of an air-atomized spray with surfactant-added water, cooling a 12-mm-thick AISI-1020 stationary steel plate at three different initial surface temperatures (400°C, 600°C, and 900°C). Furthermore, the effects of surfactant concentration and airflow rate on the cooling rate have been investigated. The surface heat flux and surface temperature show a significant improvement in cooling for all three cases of initial surface temperatures when the air-atomized spray was used with surfactant-added water. 相似文献
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High-density polyethylene (HDPE) pipes have been widely used as gas or water transport pipes owing to their comprehensive advantages. One of the principal failure modes determining pipe service lifetime is slow crack growth (SCG) with the crack occurring first at the inner surface due to the slow cooling rate of the pipe's inner wall during polyethylene (PE) pipe extrusion. In order to change the conventional cooling mode and increase the cooling rate in the inner wall of PE pipe during extrusion, a novel extrusion equipment was designed and manufactured by our research team. For this paper, compressed air as a cooling medium was introduced through the interior of the hot extruded pipe during its extrusion to realize the quick inner wall cooling, and the effects of the inner wall's cooling rate on the microstructure and mechanical properties of the PE pipe were investigated. The experimental results showed that simultaneously cooling of both the outer and inner walls could decrease the difference in the solidification rate across the pipe and reduce the residual internal stresses in PE pipe. The quick cooling of the inner wall of the extruded pipe could also decrease the PE crystal thickness, and increase the number of tie molecules in the inner wall, which is a key parameter determining the resistance to SCG. As a result, compared to the PE pipe produced by the conventional extrusion, the crack initiation time of the PE pipe manufactured by the novel method increased from 27 h to 45 h and the crack growth rate was slower. 相似文献