高温隔热纤维结构材料绝热特性分析

高温隔热纤维结构的绝热特性是决定金属热防护系统工作性能的关键因素。文中应用有限元法及有限容积法对理想化的纤维结构模型进行了数值研究,得出了纤维结构内部稳态下的温度场、热流场及速度场分布,并在此基础上计算得到纤维结构的等效导热系数,分析了温度、内部气体压力以及纤维结构密度对等效导热系数的影响。所建物理模型和分析方法可行,计算结果与实验结果吻合较好。     

对新型建筑节能保温墙体材料的探讨

新型墙体材料与建筑节能已经密不可分,在实际工作中,墙体节能还存在很多问题。现浇泡沫混凝土墙体具有轻质高强施工快捷的特点,并针对泡沫混凝土的原料、设备及技术指标进行了讨论。     

Optimization of Thermal Insulation Performance for the Porous Materials

ABSTRACT

Porous materials are widely used in porous media filtration, membrane separation, catalyst substrates, solid fuel cells, insulation, and other fields. When the porous material used in the field of insulation, heat transfer characteristics become its most important performance parameters. The heat transfer characteristics of porous material is a complex issue affected not only by solid elements and porosity, it is also affected by composite structures. Therefore, how to optimize the heat transfer properties of porous materials is a problem to be urgently solved. In this paper, the numerical method is used to study the effects of pore size, pore shape, pore connectivity, porosity and so on. It is found that pore shape, pore connectivity and gas conductivity have great impacts on the heat transfer of porous materials. The effect of pore arrangement is very little. The design optimization of porosity is affected by porous material mechanical property.     

材料沉降对水平圆形管道保温层设计的影响

定量分析了保温层材料下沉对经济厚度计算的影响,并通过分析整个保温层传热的热通路提出了经济厚度法的修正方法.在理论上研究经济厚度法的设计思路,通过修改设计参数值研究不同设计参数对经济厚度的影响.利用修正后的经济厚度法对黄台电厂实际运行的热力管道保温层进行设计.结果表明:采用修正后的经济厚度法可以使年总费用节约0.7%左右;热力管道直径D_0、下沉率M和管内介质温度T_0是影响经济厚度设计的主要参数.     

Thermal Insulation for a Pipe Using Phase Change Material

This research studies the effectiveness of phase change material (PCM) as a thermal insulation for a pipe. The proposed PCM insulation can be used for a pipe when the operating time is limited. The objective of using PCM is to utilize its latent heat from fusion to minimize heat loss from the pipe by absorbing and storing it to be discharged later to the pipe. The finite element method is employed to solve the problem, and both conduction and natural convection of liquid PCM are considered modes of heat transfer. The effectiveness of the PCM insulation is evaluated by comparing its thermal performance with insulation without phase change. Both time-dependent and time-independent boundary conditions are examined. For the time-independent case, the PCM insulation reduces the heat loss from the pipe for a significant amount of time if the Rayleigh number is low. For the time-dependent case, heat loss is effectively reduced with the PCM insulation for a significant amount of time. The high resolution capturing of the solid/liquid moving boundary and the details of flow structure are also presented.     

无锡居住建筑保温材料优化分析

通过分析无锡地区居住建筑设计方案及相关实例,从采用的保温材料供应厂家和材料成本入手,探索屋面及外墙在不同节能率下对应的保温材料成本情况,为当地建筑设计施工提供参考依据。研究表明,无锡地区勇力塑材制品厂提供的XPS被使用次数最多,50%节能率下屋面保温材料成本在30元/m2左右,外墙保温材料成本在20~60元/m2;65%节能率下屋面保温材料成本在45~70/m2元,外墙成本在35~120元/m2。     

直流系统绝缘监测装置的改进研究

直流系统绝缘监测装置对电力系统的安全稳定运行起着十分重要的作用.通过对直流系统绝缘监测原理优缺点的分析,提出了一种平衡电桥与开关电阻相结合的新型直流系统绝缘监测装置设计方案,设计母线电压检测电路和支路漏电流采集模块分别监测母线和支路的绝缘状态.采用STM32系列单片机作为主控MCU和采集MCU,建立了一种分散式模块化的多控制器绝缘监测结构.同时对直流系统绝缘监测装置的软硬件部分进行了详细的设计,并研制成样机,在多种接地状态下验证了装置接地电阻测量、支路定位和故障报警的准确性.     

Design of a Smart Thermal Insulation System

The present work aims to design a smart thermal insulation system. The smart system allows the passing of heat transfer in one direction while preventing its passing in the other direction. This system consists of two gaps separated by a thin movable partition. The two gaps have the same area and width. The partition has radiation emissivity very close to zero to exclude radiation heat transfer. The partition is free to move to either side depending on the driving force causing the motion. The first gap is filled with a fluid that has both high thermal conductivity and high thermal expansion properties, while the second gap is filled with a fluid that has very low thermal conductivity and very high thermal expansion properties. Each gap is connected by a tiny tube to its own small storage tank. Temperature and pressure sensors are used to provide signals to the programmable microcontroller in order to select and activate the desired insulation or conduction mode of the system.     

回复电压法用于变压器油纸绝缘老化状态评估

油纸绝缘材料发生老化现象时,往往会引起固体绝缘纸板材料中含水量增加及绝缘系统电介质响应特性改变。若对其进行回复电压测量,会表现出峰值升高、起始斜率增大以及峰值时间缩短等定性特征。为了进一步量化油纸绝缘老化现象与回复电压之间的关系,在介绍回复电压法基本原理的基础上,针对实验室内不同老化程度和不同含水量的油纸绝缘系统进行了回复电压试验,并结合现场实测经验,提出了基于回复电压的油纸绝缘老化状态评估方法。结果表明,油纸绝缘老化或受潮会显著降低其极化谱的主时间常数,绝缘固体材料的含水量与主时间常数的对数之间存在定量关系,利用主时间常数可以有效评估油纸绝缘的老化状态。     

用计算器编程计算管道保温层的经济厚度

本文叙述了在工程设计工作中随时计算经济保温厚度的必要性,并以实例介绍用ＣＡＳＩ）ｆｘ－１８０Ｐ或ｆｘ－３６００Ｐ（ＰＶ）型可程计算器求解单层保温经济厚度的数学原理和方法,通过对不同两种热价的对比计算,可知在同一条管道上计算结果差别很大,这就要求我们在保温设计时予以注意。     

几种新型外墙外保温材料介绍及应用

建筑围护结构革新是建筑节能的核心内容之一,针对建筑墙体节能保温工程,介绍了几种新型墙体节能保温材料的优缺点,包括无机节能保温材料、有机节能保温材料和有无机复合节能保温材料的性能,并对不同节能保温材料的性能进行了对比,指出了有无机复合材料为未来建筑用外墙节能保温材料材的发展方向。     

建筑保温隔热材料的研究及应用进展

建筑隔热保温是实现建筑节能和降耗减排的重要手段。对几种常用保温隔热材料的分类与发展进行了概述和评价,着重介绍了新型气凝胶保温隔热材料的特性与研究进展。概述了气凝胶超级隔热材料在建筑隔热保温中的应用进展,并对其建筑节能应用前景进行了展望。     

基于Lattice-Boltzmann方法的SiO2多孔绝热材料传热分析

采用四参数随机生成法构造了SiO2多孔绝热材料微观结构,引入二维九速度不可压格子多相Lattice-Boltzmann热模型,该模型能够方便的计算具有复杂边界的多孔材料微尺度传热问题,给出了从结构构造模拟到具体的Lattice-Boltzmann传热分析的程序实现流程,进行了完整的二维多孔绝热材料导热过程的数值分析。结果表明Knudsen数小于10-1时,相同孔隙率下孔径越大,有效导热系数越低。随着孔隙率的减小,有效导热系数明显增加,增加气相导热比重是增强该绝热材料绝热性能的有效途径。骨架结构对SiO2多孔绝热材料有效导热系数的影响显著。     

塔河油田井筒保温体系仿真计算

针对塔河油田的运行状况,为了降低稠油在井筒内的粘度从而降低地面集输系统能耗,开展保温技术研究.实验室测试了九种保温材料的密度、常温及高温下的导热系数、抗压强度及防水性能,结合塔河油田井况,优选出气凝胶涂料,通过建立井筒传热的物理模型和数学模型,构建塔河油田超稠油井筒保温体系,在油管外涂覆6 mm厚的气凝胶涂料可使塔河油...     

用热平衡方法求解保温层厚度的各种计算式

提出了五个用热平衡方法求解的不同情况下保温层厚度的新计算式。     

Functionally Graded Materials Optimization Using Particle Swarm-Based Algorithms

This article presents an application of particle swarm-based algorithms for volume fraction optimization of functionally graded materials. A simple and efficient method for constraint handling is included too. To optimize the material composition, two numerical examples are done. In the first example, the peak residual stresses are minimized when the FGM is cooled from a reference temperature. In the second example, the factor of safety against yielding are maximized for a temperature-dependent FGM sphere subjected to thermal gradients. The algorithms PSO, PSOPC, PSACO and PSPCACO are used too and the optimum volume fraction are obtained. According comparison of the results, particle swarm-based algorithms can be used as a powerful tool for optimizing the FG materials.     

Transparent Insulation System for Passive Solar Energy Utilization in Buildings

A new concept for the passive use of solar energy, transparent insulation, is described together with the first experimental results. Transparent insulation material has the property of being transparent or translucent to solar radiation while at the same time acting as heat insulation, Elements made of this material can be attached to the walls of buildings and thus permit the utilization of solar energy for heating. Relations are given for the dependence of heat flux and conversion efficiency of radiation into useful heat on the thermal resistance of the components. Calculations using meteorological data show that with materials parameters achievable with present technology not only south but also west/east and possibly even north orientations can lead to significant contributions to heating. In order to avoid overheating in summer, control of radiation must be provided.

Experiments with unoptimized materials on two buildings during 1982/83 showed promising results: for a south facade during a Sunny period in January, a mean flux of 9 W/m² into the house was observed. For the entire heating season the extrapolated value is 16 W/m². On a western orientation a net loss was observed, but the mean effective heat transfer coefficient of the element was lowered from 1.8 W/m²K without radiation to 0.25 W/m²K with radiation. The beneficial effect of masonry walls with regard to heat storage and damping of temperature fluctuation was also demonstrated. The elements proposed here therefore appear particularly attractive for retrofitting.     

纤维过滤器气相流场的数值研究

基于多孔介质模型对二维纤维过滤器内气相流场进行了数值计算,得到了不同结构(填充密度和过滤器深度)纤维过滤器内的静压分布.为了观察多孔介质模型在研究过滤器流场的适应性,本文还计算了不包括多孔介质模型时,相同填充密度不同纤维排列纤维过滤器内的气相流场.结果表明:基于多孔介质模型时,静压沿着过滤器深度方向线性变化,填充密度越大,初始压降越大.因此,如果多孔介质的粘性阻力系数选择合理,该模型可以应用于计算过滤器的气相流场.但是,该模型并没有考虑过滤器内部纤维排列方式对其内部流场的影响,而实际上,过滤器内部纤维的排列行为将显著影响过滤器的流场和初始压降.因此如果要进一步研究过滤器内复杂的气固两相流,还需进行深入研究.     

Influence of Participating Radiation on Measuring Thermal Conductivity of Translucent Thermal Insulation Materials with Hot Strip Method

The hot strip method, as one typical transient method, is widely used to measure the effective thermal conductivity of thermal insulation materials at various temperatures. Since the test theory is based on solving the energy equation via heat conduction, the test result will be questionable when measuring thermal insulation materials, such as silica aerogel and photovoltaic glazing, in which the participating thermal radiation is a dominant heat transfer mode at high temperature. In this study,...