空间光学遥感器热设计

为了保证空间光学遥感器所需温度条件,本着被动热控为主、主动热控为辅的原则对其进行了热设计.首先,分析了遥感器在轨工作模式,建立了遥感器外热流计算模型,根据遥感器各面外热流变化,确定了3个极端工况.然后,以对日低温工况热设计为主对遥感器进行了热设计.最后,对热设计进行了热仿真分析和热试验验证.结果表明:镜组温度水平可控制...     

扫描型热像系统均匀性校正方法研究

随着热像系统时域噪声等效温差（NETD）的不断下降,残余固定图形噪声（RFPN）的不稳定性成为制约系统性能,特别是制约系统识别能力的一个关键因素。通过分析热像系统响应非均匀性产生的机理,介绍一种扫描型热像系统获得场景平均辐照度点的方法,实现了以场景平均辐照度点为校正基准点的动态校正。采用该方法研制的热像系统在（0～50）℃场景动态范围内可使系统的RFPN小于15mK。通过样机冬、夏两季外场试验以及各种环境试验,验证了该校正方法在热像系统温度发生变化以及场景辐照度发生变化时具有良好的适应性。     

电动汽车锂离子电池热管理系统研究进展

锂离子电池作为电动汽车最广泛使用的动力源,对工作温度高度敏感,为保证其高性能和安全运行,电池热管理系统必不可少.本文综述了近年来锂离子电池热管理系统的研究进展.首先讨论了由高低温环境和电池温度不均匀引起的临界热问题.在此基础上,对设计原则和现有的电池热管理系统进行了广泛的介绍和阐述.然后进一步分析了用于未来电池热管理系统的热电器件和内部加热方法等新兴技术.分析表明,被动和主动冷却/加热方法的组合有望满足苛刻的热要求,特别是在功率波动剧烈的动态条件下.此外,电池在变工况下所输出的电流、电压等均不相同,因此建议对电动汽车动力电池进行动态性能实时管理,从而延长电池使用寿命。     

真空罐内应用的太阳模拟灯阵热设计

为了解决太阳模拟灯阵整体放在真空罐内使用时的导热问题,采用热管导热的方案,设计了专门的氙灯导热机构。计算了液氮系统的导热能力,结果显示,真空罐液氮冷却系统的温度升高ΔT为2074 1 K,小于其过冷度4 K,表明真空罐液氮冷却系统完全可以将太阳模拟灯阵的热量导出。采用热管导热技术,设计了导热机构,用有限元分析法进行了热仿真分析,分析结果表明,氙灯阴阳极温度维持在100 ℃左右,氙灯灯泡维持在655 ℃左右,满足氙灯正常工作的温度条件;积分器和反射镜组件温度维持在200 ℃左右,椭球镜温度维持在135 ℃左右,亦满足正常工作的温度条件,从而验证了热设计的正确性。     

Model experiments for the Czochralski crystal growth technique

A lot of the physical and the numerical modeling of Czochralski crystal growth is done on the generic Rayleigh-Bénard system. To better approximate the conditions in a Czochralski puller, the influences of a rounded crucible bottom, deviations of the thermal boundary conditions from the generic case, crucible and/or crystal rotation, and the influence of magnetic fields are often studied separately. The present contribution reviews some of these topics while concentrating on studies of the flow and related temperature fluctuations in systems where a rotating magnetic field (RMF) was applied. The three-dimensional convective patterns and the resulting temperature fluctuations will be discussed both for the mere buoyant case and for the application of an RMF. It is shown that a system between a Rayleigh-Bénard and a more realistic configuration, which is still cylindrical but whose surface is partially covered by a crystal model, behaves much the same as a Rayleigh-Bénard system. An RMF can be used to damp the temperature fluctuations. Secondly, a more Czochralski-like system is examined. It turns out that the RMF does not provide the desired damping of the temperature fluctutions in the parameter range considered.     

基于ANSYS的传导冷却超导磁体系统的热分析

在传导冷却超导磁体系统中,超导磁体与系统其它部分的温度平衡过程是依靠固体间的热传导来实现热量传递的。由于超导磁体和冷屏等低温部件冷却条件的差异,将导致磁体内部各处和冷屏不同部位的温度分布不均匀。分析研究超导磁体系统的低温温度分布状况,对于低温系统的热设计和磁体的温度裕度设计具有重要意义。文中借助于ANSYS有限元分析软件,建立了一个大口径传导冷却超导磁体低温系统的稳态三维热分析模型,仿真了超导磁体和冷屏的空间温度场,得到了传导冷却超导磁体低温系统的热分布规律。该分析结果对于大口径传导冷却超导磁体的低温系统设计具有重要的参考价值。     

低轨道低能量空间光学遥感器热设计

为了保证空间光学遥感器所需温度条件,以被动热控为主、主动热控为辅的原则对其进行了热设计.分析了其轨道环境特点,计算了遥感器轨道寿命内原子氧通量,选择了一种玻纤增强聚四氟乙烯复合膜(β布)作为多层隔热组件面膜.根据其工作模式和外热流特点,确定了三个极端工况,以对日低温工况热设计为主要对象.热试验结果表明:热设计满足遥感器...     

内嵌定向高导热层疏导式结构热防护机理分析

针对飞行器高超声速飞行时严重的气动加热环境, 提出内嵌定向高导热层的疏导式热防护系统. 运用数值方法分析了特定条件下内嵌定向高导热层的疏导式系统的防热效果, 外壁面最高温度下降了9.1%, 内壁面最高温度下降了31.5%, 高温区和低温区都被封闭在外层区域, 内层温度更加均匀, 实现了热流由高温区向低温区的转移, 削弱了高温区的热载荷, 强化了整体结构的热防护能力. 研究表明, 随着气动热流密度比与辐射散热面积比的增大, 疏导结构的冷却效果增强. 本文还对疏导防热系统的结构参数和材料参数对冷却效果的影响进行了分析, 为结构的设计和材料的选取提供一定的依据.     

大口径内扫描红外变焦光学系统设计

设计了一种大口径内扫描三档变焦光学系统。系统工作波段为7.7～10.3μm,焦距为65mm、130mm、390mm,变倍比为6∶1,系统F数为1.67,最大口径为240mm。系统具有较好的成像质量,且对冷反射和扫描温差进行了优化控制,这种变焦光学系统具有大口径、长焦距,能够用于对远距离小目标跟踪的特点,在高性能红外热像仪中得到较好的应用。     

光学系统实现热补偿的通用条件

运用光学系统的近轴成像公式，推导出微分形式的物面位于任意位置时热补偿的通用条件，包括薄单透镜、密接薄透镜组和分离薄透镜组等不同情况。推导过程中假设物面位置不随温度发生变化，并且忽略分离薄透镜组中各组分上光线入射高度随温度的变化。利用推导的条件建立了像距的归一化温度变化率与各透镜光热膨胀系数之间的关系，指出所得到的条件具有更加普遍的意义，能够指导机械和伺服控制系统的工程设计，并且在物面位于无穷远时与目前普遍采用的热补偿条件相吻合，即光学系统的光热膨胀系数等于壳体的热膨胀系数。     

Remote sensing of thermal profile in the lower atmosphere by a radio-acoustic system

Summary A new radio-acoustic methodology, for the remote sensing of temperature profile in the lower troposphere, has been developed in the last few years. Since 1972 different types of radio-acoustic sounders have been designed and tested in the USA, Europe and Japan. The technique used for measurements in a Doppler tracking of a short acoustic pulse with a radar. Measurement of the sound speed as a function of delay from the start of the acoustic beam leads to the acquisition of the temperature vertical profile. After a brief review of the experimental radio-acoustic systems, the metric radio-acoustic sounder developed and tested at Istituto di Cosmogeofisica of the National Research Council (Italy) is analysed. Results of this sounder and its performance in fog-capping thermal inversion measurements are discussed. A comparison of the data measured with the radio-acoustic system and with traditional methods shows:a) sounder ability to produce vertical thermal profile with temperature accuracy and height discrimination comparable with conventional soundings;b) advantages typical of remote-sensing technique;c) applicability of the system both in assessing thermodynamic conditions in the planetary boundary layer (PBL) and in sensing conditions conductive to high concentrations of air pollutants at ground level. Preliminary results of the completely automatized system and application to air quality management are also presented. This work was partially supported by the Commission of the European Communities (CEC) under contract No. ENV·348 I(S) and by a research contract by ENEL-CRTN Milano.     

Thermal parameters of MgSO4·7H2O and NiSO4·7H2O crystals added with urea and thiourea

Pure and impurity-added (with urea and thiourea) MgSO₄·7H₂O and NiSO₄·7H₂O single crystals were grown by the free-evaporation method from aqueous solutions. Density was measured by the flotation method. X-ray diffraction data were collected for powder samples and used for the estimation of thermal parameters like Debye-Waller factor, mean-square amplitude of vibration, Debye temperature and Debye frequency. The thermal parameters do not vary in a particular order with respect to impurity concentration, which could be attributed to the random disturbance created by the impurity molecules in the hydrogen-bonding system of the MgSO₄·7H₂O and NiSO₄·7H₂O lattices.     

低温恒温器简介

在低温领域中,经常需要对低温恒温条件下样品的各种低温性能,如热物理性质、机械性能、光学物理性能、磁热性能及超导性能等进行测试。这就需要提供一种实验装置来维持样品的低温恒温条件。而低温恒温器是一种能够提供低温恒温条件并与外界热绝缘的低温装置,它应用广泛,是进行低温实验的必要设备。主要介绍了低温恒温器的概念、应用、分类、结构及其设计。     

Classical and photopyroelectric studies of optical and thermophysical properties of starch sheets: dependence on water content and temperature

The optical and thermophysical parameters of starch films (obtained by extrusion) were determined in order to obtain input data for photothermal studies of water migration in such films. The optical spectra, sorption isotherm, and volume change were measured for samples equilibrated at different levels of relative humidities. The photopyroelectric method was used to measure thermal parameters as a function of water content and temperature. The thermal conductivity, thermal effusivity, and volume specific heat all increase with water content while the thermal diffusivity remains almost constant. The temperature behaviour of the thermal parameters in the -15+70 °C temperature range was measured for samples with different water contents. No phase transition was observed at 0 °C, which proves either that water in the starch matrix is not in a free form, or the fact that water dissolved other particles shifting the melting point to a lower temperature. Received: 1 June 1999 / Final version: 13 March 2000 / Published online: 7 June 2000     

Scanning near field thermal microscopy on a micromachined thin membrane

A resistive probe based scanning thermal microscope (SThM) has been used to perform complementary near field thermal measurements on the surface of a thin semiconductor membrane. This thin structure is part of a micromachined thermal rf power sensor and includes an integrated resistive heater used as an absorbing element for the input power. The resulting 2D surface temperature distribution and the 2D thermal wave propagation characteristic were determined. Considering the thermal wave behaviour at near field conditions, the local thermal conductivity of the thin membrane and the surrounding bulk material was investigated by usage of the 3ω-method.     

半绝缘GaAs光电导开关的瞬态热效应

实验用波长1064 nm,触发光能为1.0 mJ的激光脉冲触发电极间隙为4 mm的半绝缘GaAs光电导开关,当光电导开关的偏置电压达到3800 V时,开关进入非线性(lock-on)工作模式,在偏置电场和触发光能不变的条件下,开关输出稳定的非线性电脉冲,1500次触发后GaAs开关表面出现因丝状电流引起损伤的痕迹.分析认为:在一定触发光能和电场阈值条件下,开关芯片内存在两种瞬态热效应:热弛豫效应和光激发电荷畴-声子曳引效应.热弛豫时间很短,在皮秒甚至亚皮秒量级,热弛豫过程导致了热传导的弛豫行为;当光激发电荷畴以10⁷ cm/s的速度从阴极向阳极渡越时,在这两种效应的作用下使得开关芯片瞬态温度变化发生了弛豫振荡现象.光激发电荷畴-声子曳引效应在位错运动方向上传播,声子流携带的热能集中在移动的平面内,使得移动区域温度升高,移动轨迹经多次叠加累积呈现出丝状的损伤痕迹. 关键词： 半绝缘GaAs光电导开关 热弛豫效应 光激发电荷畴-声子曳引效应 丝状电流     

Numerical investigation on properties of attack angle for an opposing jet thermal protection system

The three-dimensional Navier-Stokes equation and the k-ε viscous model are used to simulate the attack angle characteristics of a hemisphere nose-tip with an opposing jet thermal protection system in supersonic flow conditions.The numerical method is validated by the relevant experiment.The flow field parameters,aerodynamic forces,and surface heat flux distributions for attack angles of 0°,2°,5°,7°,and 10° are obtained.The detailed numerical results show that the cruise attack angle has a great influence on the flow field parameters,aerodynamic force,and surface heat flux distribution of the supersonic vehicle nose-tip with an opposing jet thermal protection system.When the attack angle reaches 10°,the heat flux on the windward generatrix is close to the maximal heat flux on the wall surface of the nose-tip without thermal protection system,thus the thermal protection has failed.     

VM-1500热真空试验箱的研制

热真空试验箱是用来模拟太空的真空、冷黑及太阳辐照环境,完成卫星的热平衡、热真空试验,满足卫星研制需要的关键地面大型试验设备。文章概要介绍了研制的一台VM-1500有效试验空间为1200mm×1600mm的空间模拟器的组成、采用的模拟技术、调试及使用情况。使用结果表明:该设备的各系统运行稳定、可靠,模拟室的真空度、热沉温度、温度测量系统等均能满足卫星整星热真空试验的要求。     

Thermal Explosion of a Heterogeneous Liquid–Solid System in a Semibatch Reactor with Consideration for the Temperature Dependence of Distribution Coefficient

The thermal explosion of a heterogeneous liquid–solid reaction system in a semibatch reactor was simulated with consideration for the temperature dependence of distribution coefficient. It was shown that this temperature dependence strongly influences the critical conditions of ignition. At weak temperature dependence of a distribution coefficient in a subcritical mode, the process was a degenerative one. Unlike a classical degenerative thermal explosion of homogeneous systems, which is determined by the small values of thermal effects and activation energies, degeneration in heterogeneous systems is determined by the laws of interphase mass transfer.     

LED灯表面对流换热系数的测算研究

提出了一种在第三类边界条件下,根据LED灯瞬态温度场的变化规律,通过对其表面温度的实际数值测定来推算LED灯表面对流换热系数的快速测定方法。基于对流热平衡理论,设计了一种可以在较高表面换热强度条件下进行测试的装置,通过实验测定LED灯上下表面的温度,结合曲线拟合对实测数据进行数理分析,得到较宽范围内的表面对流换热系数。实验结果表明:该测试方法简单、实用,测试时间较短(实验准备与数据测定大约需要30 min),测试精度较高(数据拟合误差不高于0.2%),可靠性强,可以用于工程热设计等多种相关发热体表面对流换热系数的测定。