二乙二醇单甲醚液相导热系数的实验研究

利用钽丝作为热线的瞬态双热线系统对温度区间233－373K、压力区间为0．1—30 MPa的液相二乙二醇单甲醚（diethylene glycol monom ethylether,DGMME）的导热系数进行了实验研究,并将实验数据拟合为温度和压力的关联式。实验数据与导热系数关联式计算结果的标准偏差和最大偏差分别为0．...     

导热系数测量实验的改进

利用传感器和数字温度计代替热电偶和数字电压表测量导热系数 ,实验更简捷、科学、精确     

含水砂土导热系数实验研究

对含水砂土导热系数随含水率变化规律的实验研究是进行地源热泵系统设计的基础,本文制备了五类不同粒径,不同含水率的砂样及八类混合砂样,测试了其热导率随含水率的变化规律,并拟合了混合砂样的热导率曲线,结果表明:对于五类不同粒径的砂样及八类混合砂样,热导率均随含水率的增加而增大,而粒径对于热导率影响不大,在低水分含量(ω15%)条件下,混合砂样拟合曲线与实验值吻合较好。     

二乙二醇二甲醚液相导热系数实验研究

本文利用瞬态单热线法对温度区间233～373 K、压力区间0.1～30 MPa的二乙二醇二甲醚(DMDE)的导热系数进行了实验研究,为替代燃料研究提供了基础数据,导热系数测量不确定度为±2%.实验数据拟合成导热系数关于温度和压力的方程,实验数据与拟合方程计算值的最大偏差为-2.56%,平均绝对偏差为0.91%.     

热损耗条件下导热系数反演模型及实验研究

通过导热反问题反演求解导热系数通常误差较大,本文构建考虑热损耗条件下的虚拟薄板模型精确求解导热系数。首先通过数值算例验证模型的准确性和稳定性,正向问题使用有限差分法进行求解,反问题求解采用人工蜂群算法进行目标函数最优化。然后搭建第二类边界条件下导热正向装置,进行导热系数实例反演和实验研究,并将新模型与理论模型反演结果对比分析。结果表明理论模型反演结果的相对误差约为-14.76%,而新模型下导热系数反演相对误差达到-4.67%。新模型较理论模型反演结果更精确,有效降低了热损耗对反演的影响,提高了反演精度,更符合实际工况。     

混合制冷剂液相导热系数预测方程

本文提出了一个预测液相制冷剂混合物导热系数的方程。这种预测方法仅需要已知混合物各组元的导热系数、分子量、摩尔成分等几种物性,就可预测混合物的导热系数．本预测方程形式简单,并通过与文献试验数据及其它预测方程比较,证明本预测方程的计算精度比其它方程较高,能够满足工程要求。     

温度传感器在测定不良导体导热系数实验中的应用

将单片计算机与温度传感器结合用于导热系数测定仪中测量温度,改进后的导热系数测定仪结构紧凑,操作简单、读数方便.     

导热系数测定设计性实验

导热系数测定是大学物理热学中比较重要的实验,对稳态法测量不良导体导热系数的原理和实验方法进行研究,对于不同形态的导热材料,提出了几种可行的实验方案。实验内容和测量结果符合设计性实验要求,有助于启发学生的创新意识。     

特殊环境下织物的导热系数试验研究

舱外航天服织物的研究是舱外航天服设计工作中的一项重要环节,尤其是其热特性,对航天员舱外作业安全和工效有着重要的影响.为此,本文通过对织物的传热机理、服装的热舒适性及平板导热仪的原理等进行分析,研制了一种新型的双平板式导热仪对特殊环境(超低温、真空)下的织物导热系数进行了试验研究,得到了不同特殊环境下织物的导热系数,并对结果进行了分析和讨论.     

对不良导体导热系数测量实验的改进

对稳态法测量导热系数的实验进行改进,用AD590温度传感器代替热电偶,实现了计算机对数据的采集和处理     

高压烧结镀Cr、Ti膜金刚石/铜复合材料热导率研究

 采用磁控溅射方法,在金刚石表面镀覆活性金属Cr膜和Ti膜,在高温高压下合成了镀活性金属膜金刚石/铜复合材料。实验发现,活性金属的加入增强了金刚石与铜界面间的结合强度,减少了界面热阻,提高了复合材料的热导率。复合材料热导率随着金刚石体积分数的增加而降低,随着金刚石的粒度增大而提高。这主要是由界面热阻引起的,可以通过增大金刚石粒度和改善界面状态来提高复合材料热导率。     

用Origin处理导热系数测定实验的数据

基于用稳态法测量不良导体的导热系数实验,为了求得更为精确的导热系数,用origin软件处理实验数据,拟合出温度和时间的曲线,并求得冷却速率及导热系数.     

Controlling Thermal Conductivity of Few-Layer Graphene Nanoribbons by Using the Transversal Pressure

We study the thermal transport of few-layer graphene nanoribbons in the presence of the transversal pressure by using molecular dynamics simulations.It is reported that the pressure can improve the thermal conductivity of few-layer graphene nanoribbons.This improvement can reach 37.5%in the low temperature region.The pressure dependence of thermal conductivity is also investigated for diferent length,width and thickness of few-layer graphene.Our results provide an alternative option to tuning thermal conductivity of few-layer graphene nanoribbons.Furthermore,it maybe indicate a so-called pressure-thermal efect in nanomaterials.     

固体热导率测量仪的新发现

实验通过稳态法使用TC-3型固体热导率测定仪[1,9]的测量方法改变来测量海洋大气热导率,结构简单,误差更小,一机多用.通过改变加热铜盘A与散热铜盘B之间的距离,探究距离对大气热导率的影响,并与教材中介绍的气体热导率测定仪测量的大气热导率进行比较.     

Controlling Thermal Conductivity of Few-Layer Graphene Nanoribbons by Using the Transversal Pressure

We study the thermal transport of few-layer graphene nanoribbons in the presence of the transversal pressure by using molecular dynamics simulations. It is reported that the pressure can improve the thermal conductivity of few-layer graphene nanoribbons. This improvement can reach 37.5% in the low temperature region. The pressure dependence of thermal conductivity is also investigated for different length, width and thickness of few-layer graphene. Our results provide an alternative option to tuning thermal conductivity of few-layer graphene nanoribbons. Furthermore, it maybe indicate a so-called pressure-thermal effect in nanomaterials.     

Experimental Investigation on the Thermal Conductivity and Viscosity of Silver-Deionized Water Nanofluid

Abstract

This article presents an experimental investigation where the thermal conductivity and viscosity of silver-deionized water nanofluid is measured and studied. The mixture consists of silver nanoparticles of 0.3, 0.6, and 0.9% of volume concentrations and studied for temperatures between 50°C and 90°C. The transient hot-wire apparatus and Cannon-Fenske viscometer are used to measure the thermal conductivity and kinematic viscosity of nanofluid, respectively. The thermal conductivity increases with the increase in temperature and particle concentrations. A minimum and maximum enhancement of 27% at 0.3 vol% and 80% at 0.9 vol% are observed at an average temperature of 70°C. The viscosity decreases with the increase in temperature and increases with the increase in particle concentrations. The effect of Brownian motion and thermophoresis on the thermo-physical properties is discussed. Thus, an experimental correlation for thermal conductivity and viscosity, which relates the volume concentration and temperature, is developed, and the proposed correlation is found to be in good agreement with the experimental results.     

Characterization of Powder Beds by Thermal Conductivity: Effect of Gas Pressure on the Thermal Resistance of Particle Contact Points

The thermal conductivity of ceramic powder packed beds was measured at temperatures below 100 °C for various powder sizes and compositions and under different gas atmospheres. Measurements at low pressures (down to 10 Pa) combined with a theoretical model allowed the elucidation of geometrical and thermal resistance parameters for the contact points between granules. The gap thickness and contact point size were found to be well correlated with the mean particle size. The thermal conductivities of all powders at low pressure were found to differ at most by a factor of two, whereas the solid‐phase conductivities of the powder materials differed by more than one order of magnitude. A theoretical model accounting for the size‐dependence of contact point conductivity is incorporated to rationalize this trend.     

氮化铝陶瓷低温热导率的实验研究

根据轴向稳态热流法原理 ,实验研究了 Al N陶瓷的低温热导率 ,为高温超导制冷机直接冷却提供了必要的实验数据。 Al N的热导率在 30～ 170 K之间 ,随温度的升高而增大 ,在 10 0 K时达到 5 8.36 W/ (m· K)。根据平均自由程理论 ,对影响氮化铝陶瓷热导率的微观因素进行了分析 ,影响本次测试氮化铝样品低温热导率的主要因素为声子与缺陷之间的散射。     

高温高压下黑云斜长片麻岩的电性研究

 在压力1 GPa、温度250~1 100 ℃、频率0.1 Hz~1 MHz的条件下,采用阻抗谱方法,对来自阴山造山带的太古代黑云斜长片麻岩进行了电导率实验研究。实验发现：（1） 所有样品的阻抗谱都是由一个大的高频半圆弧Ⅰ和一个小的被压缩了的低频弧Ⅱ组成,阻抗弧Ⅰ主要代表矿物颗粒内部传导机制,阻抗弧Ⅱ更有可能代表的是样品和电极之间的传导机制;（2） 电导率随温度的变化遵循Arrhenian定律,但在700~750 ℃间有近一个量级的跳跃,通过对比实验前后样品的显微照片和探针分析数据,认为这一电导率的大幅跳跃可能是样品中黑云母发生大量脱水熔融的缘故;（3） 在高温段750~1 100 ℃,部分熔融样品的电导率主要由钠离子传导控制;（4） 在低温段250~700 ℃,样品的激活能为0.53 eV;在高温段750~1 100 ℃,样品的激活能为1.41 eV。激活能的改变可能与样品的结构变化有关,还与样品和熔体中钠的含量以及扩散有关。     

Effect of the Spin Fluctuations on the Carrier Thermal Conductivity in High-Tc Oxides

A theory of the carrier thermal conductivity for electron antiferromagnetic spin fluctuation scattering has been developed and on this basis the experimental results of high-T_c oxides have been interpreted. Our theoretical analysis fits the experimental results excellently and suggests that the antiferromagnetic spin fluctuations affect the carrier thermal conductivity in high-T_c oxides.