Optimization of multilayer thermal insulation

An iteration method is developed for determination of the thicknesses of layers of a multilayer thermal insulation with minimum mass, with consideration of temperature limitations. The penalty function method is employed.Notation M(h) target function - _i thickness of the i-th layer - p_i density of material in i-th layer - n number of layers of thermal insulation - y spatial coordinate - t time - Y_i, i = 0, 1, 2, ..., n coordinates of layer boundaries - Cⁱ(T) volume heat capacity of material in i-th layer - ⁱ(T) thermal conductivity coefficient of material in i-th layer - (y) initial temperature distribution - q thermal flux - t_c right-hand value of time interval - T _max ⁱ , i = 1, 2, ..., n maximum admissible temperatures on i-th boundary - penalty function - penalty parameters - g_i function considering temperature limitations - transformed function - k number of successive unconditional minimization problem - l number of iteration in search for local minimum - ,, s parameters of conjugate gradient method Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 39, No. 2, pp. 286–291, August, 1980.     

隔热涂料的研制

采用环氧树脂为基体,空心玻璃微珠、树脂中空微球和空心微珠为填料,制备了隔热性能和抗渗性优良的隔热涂料.研究了颜填料的种类、空心微珠的粒径对涂料隔热性能的影响;以及混合粒径的空心微珠制备涂层的隔热效果.结果表明,树脂中空微球的引入能较大提高涂层的隔热性能.涂层可以在长时间内保持很好的隔热效果,2mm厚的涂层的隔热温度一直保持在8℃左右.涂层经3.5%NaCI溶液中常温浸泡30d后,涂层电阻一直保持在109.56Ω·cm2,电容值保持在10-10.30F·cm-2,涂层具有较好的抗渗性能.     

热传导对双陶瓷热障涂层隔热效果影响研究

为了更好地设计双陶瓷热障涂层结构,考察在制备和服役过程中热导率的变化对隔热效果的影响,建立了双陶瓷热障涂层半透明数学模型,采用有限元ANSYS软件模拟了稳态隔热效果.结果表明:顶层陶瓷层的热导率增大降低了隔热效果,且随顶层厚度增加隔热效果降低幅度增大;第2层陶瓷层的热导率增大降低了隔热效果,且随顶层厚度增加隔热效果降低幅度减小;陶瓷层半透明且衰减系数很小时,顶层厚度增加,隔热效果先快速后缓慢增加至不变甚至略有降低,且远低于相同条件下不透明时.顶层陶瓷层热导率变化对隔热效果影响大于第2层陶瓷层.     

隔热预涂金属卷材涂料的研究进展

预涂金属卷材由于其多变的色彩,轻便,易加工及优越的机械性能,越来越多地被应用到建筑、汽车、家电面板等领域。随着城市发展对节能的要求越来越高,金属卷材对隔热的需求也日益显著。阐述了目前国内外卷材涂料的研究热点,初步探讨了隔热涂料的隔热机理及发展现状,特别对隔热卷材涂料的研究现状和市场情况进行了分析,并对隔热卷材涂料未来的发展趋势和研究方向提出了展望。     

Low temperature thermal insulation using diffraction effect

A new type of vacuum layer low temperature thermal insulator is proposed, a reflecting shield which is nontransparent for radiation, having a surface with a regular system of openings. Calculation of the diffraction of the electromagnetic waves allows one to make the total area of the openings close to the area of the shield and thus practically eliminate heat conduction in the insulator by residual gases.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 20, No. 6, pp. 965–972, June, 1971.     

Improved OCXO's oven using active thermal insulation

This paper shows how it is possible to improve the performance of thermal enclosures by using a compensating system the principle of which has been described by F. Walls a few years ago (41st AFCS, 1987). It is shown that because of the thermal network between the outside temperature, the temperature sensor and the device to be regulated, the latter may undergo residual temperature variations which reduce the overall thermal efficiency of the oven. This paper shows how thermal transfer functions can be measured by using an experimental setup in which the node temperatures are measured by thermal sensors. By identifying the thermal response of the nodes with the theoretical transfer function under external temperature or heater excitation, the components of the equivalent R-C network can be determined. By knowing these thermal transfer functions, it is then possible to make use of a compensating system which can eliminate the parasitic static as well as dynamic thermal effects. Validating measurements and experimental results are presented which show the strong improvement achieved by this compensating system with respect to the conventional approach     

双陶瓷层热障涂层的隔热行为有限元模拟研究

基于热传导、热对流和热辐射理论建立了双陶瓷层热障涂层不透明和半透明物理模型,采用有限元ANSYS软件模拟了稳态温度场。结果表明双陶瓷层在不透明时,随总厚度或顶层厚度增加,顶层上表面温度近似线性增加,第2层和粘结层上表面温度近似线性降低。在陶瓷层半透明条件下,衰减系数对各层温度有一定影响。在衰减系数很大时,各层温度与不透明情况类似;在衰减系数较小时,顶层上表面温度略低于不透明时,第2层上表面温度略高于不透明时,粘结层上表面温度先快速后缓慢降低并保持不变,且远高于不透明时,界面反射能降低各层温度。     

轻质复合材料高温隔热性能

设计了一套隔热材料高温(>1200℃)隔热效果的测试装置, 可对隔热材料进行快速、 低成本的有效测试和筛选。采用本装置在材料热面中心温度为1600℃±10℃时, 考察了碳/酚醛复合材料和ZrO₂纤维板材料背部升温历程, 评价了2种材料的隔热性能, 并采用有限差分法数值模拟了ZrO₂纤维板材料背部升温历程, 预测其有效导热系数。研究表明, 在加热初期400s时间内, 碳/酚醛复合材料的隔热性能优于ZrO₂纤维板的隔热性能, 后期则相反; ZrO₂纤维板的隔热性能与体积密度有关, 有效导热系数随温度升高而非线性地增大。      

高效绝热材料的研究

实验采用载体法制造氧化锆纤维,研究了不同稳定剂对氧化锆纤维稳定性及强度的影响,并采用DTA分析了浸渍的粘胶纤维在升温过程的物化过程,采用XRD分析了稳定剂含量对氧化锆纤维相组成的影响,利用SEM观察了氧化锆纤维的显微结构,结果表明,制备的氧化锆纤维具有优异的稳定性和绝热效果.     

真空绝热板热工性能的研究

介绍真空绝热板的构造及加工工艺，对其高效绝热热工性能进行理论分析及实验数据测试，运用数理统计及计算机数值模拟的方法分析其热工性能随自身参数及制造工艺的变化规律，提出产品生产、施工及使用中应注意的问题和改进的意见。     

Prediction of the thermal conductivity of insulation materials

From a theoretical and experimental examination of thermal conductivity expressions proposed in the literature, a geometric mean equation is found to give predictions which most closely agree with experimental data for debased alumina materials with a range of porosities. Using the equation a computer program is developed which predicts conductivities of multi-component systems and presents data in the form of a three-component diagram with iso-conductivity lines.     

电子倍增CCD相机制冷绝热设计

对电子倍增CCD(EMCCD)相机制冷的必要性以及热电制冷器(TEC)的特点进行了说明,阐述了真空绝热的优势,分析了真空绝热失效条件,提出了真空绝热的难点及真空保持方案,分析了相机芯片发挥其性能所需的制冷温度,对制冷相机漏热途径进行了分析,计算了克服漏热所需的制冷功率,并设计了制冷绝热方案,对相机进行了稳态热分析建模,将多级热电制冷器进行了参数化转化并将其带入模型边界中,经过迭代拟合得到了相机杜瓦及芯片温度分布,分析了绝热制冷方案的可行性。     

Thermophysical characteristics of thermal insulation on metal backing

An experimental method is described for determining the thermophysical characteristics of a coating of thermal insulation on metal backing. Results of measurements of samples of poly-methyl methacrylate and a composite material in the 10–80°C temperature range are presented.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 35, No. 1, pp. 18–24, July, 1978.     

Mechanical properties and thermal conductivity of lightweight and high-strength carbon-graphite thermal insulation materials

Journal of Materials Science - Thermal insulation composites are widely used in civil and military applications; however, it is difficult to achieve the synergy of multiple technical objectives...     

Layered composite thermal insulation system for nonvacuum cryogenic applications

A problem common to both space launch applications and cryogenic propulsion test facilities is providing suitable thermal insulation for complex cryogenic piping, tanks, and components that cannot be vacuum-jacketed or otherwise be broad-area-covered. To meet such requirements and provide a practical solution to the problem, a layered composite insulation system has been developed for nonvacuum applications and extreme environmental exposure conditions. Layered composite insulation system for extreme conditions (or LCX) is particularly suited for complex piping or tank systems that are difficult or practically impossible to insulate by conventional means. Consisting of several functional layers, the aerogel blanket-based system can be tailored to specific thermal and mechanical performance requirements. The operational principle of the system is layer-pairs working in combination. Each layer pair is comprised of a primary insulation layer and a compressible radiant barrier layer. Vacuum-jacketed piping systems, whether part of the ground equipment or the flight vehicle, typically include numerous terminations, disconnects, umbilical connections, or branches that must be insulated by nonvacuum means. Broad-area insulation systems, such as spray foam or rigid foam panels, are often the lightweight materials of choice for vehicle tanks, but the plumbing elements, feedthroughs, appurtenances, and structural supports all create “hot spot” areas that are not readily insulated by similar means. Finally, the design layouts of valve control skids used for launch pads and test stands can be nearly impossible to insulate because of their complexity and high density of components and instrumentation. Primary requirements for such nonvacuum thermal insulation systems include the combination of harsh conditions, including full weather exposure, vibration, and structural loads. Further requirements include reliability and the right level of system breathability for thermal cycling. The LCX system is suitable for temperatures from approximately 4 K to 400 K and can be designed to insulate liquid hydrogen, liquid nitrogen, liquid oxygen, or liquid methane equipment. Laboratory test data for thermal and mechanical performance are presented. Field demonstration cases and examples in operational cryogenic systems are also given.     

Three-dimensional porous graphene-based ultra-lightweight aerofoam exhibiting good thermal insulation

Three-dimensional (3D) architectures of graphene and carbon nanotubes (CNTs) were prepared via the in situ self-assembly of graphene oxide and carboxyl-functionalized CNTs by mild chemical reduction and freeze-drying. The prepared 3D architectures exhibited densities of 7.35–9.68 mg/mL and thermal conductivities of 0.0192–0.0414 W/mK. These features were created by a highly porous structure, including millimeter-, micrometer-, and nanometer-scale pores. A number of analytical techniques were used to characterize the 3D architectures of graphene. The highly porous graphene-based aerofoams exhibited low densities, good thermal stabilities, and low thermal conductivities, making them excellent candidates for application in thermal protection materials, as well as in super capacitors and energy storage systems.     

纳米TiO2在保温隔热涂料中的应用

通过对膨胀珍珠岩,成膜物等的分析,确定了隔热保温涂料的最佳配方;通过应用纳米TiO2浆料加入涂料,成功解决了涂料的耐候性问题.调整成膜乳液和成膜助剂质量比,应用纯丙乳液获得了一种保温性能良好,耐候性良好的纳米复合隔热保温涂料.经试验证明纳米TiO2浆料在添加量总质量的4%时性能最优.最终测定该保温涂料的导热系数为0.0598 W/(m·K).     

Rare-earth-niobate high-entropy ceramic foams with enhanced thermal insulation performance

The introduction of porous structures into high-entropy ceramics is expected to further improve its thermal insulation performance. In this work, a series of novel rare-earth-niobate high-entropy ceramic foams((Dy_0.2Ho_0.2Y_0.2Er_0.2Yb_0.2)₃NbO₇) with hierarchical pore structures were prepared by a particle-stabilized foaming method. Atomic-scale analysis reveals that high entropy causes atom displacement and lattice distor...     

Temperature variation of thermal conductivity of self-pumping multilayer insulation

Temperature dependence of the thermal conductivity of self-pumping multilayer insulation was measured in the temperature range 90–295 K. The measurements were performed with a flat-plate calorimeter and using the integral method. A comparison was made between the thermal conductivities of the self-pumping insulation and the conventional type.