稳态平板法测量导热系数的若干影响因素分析

研究发现,热源温度和环境温度等因素通过试样的侧面散热影响平板稳态法测量导热系数的精度,散热铜板的上下表面散热功率不一致也将影响导热系数测量的准确性.用大空间自然对流理论对实验数据处理公式修正后,可有效减小侧面散热对测量的影响.在设计实验时应首先获得散热铜板的散热功率曲线,选择合适的散热铜板温度,而后通过综合考虑试样厚度和热源温度以控制传热温差,使测量时散热铜板温度处于最佳温度附近.     

用3ω法测量非线性KTP晶体各向异性导热系数

 非线性KTP（KTiOPO₄）晶体的各向异性导热性能对于部分消除热应力以改善倍频效果具有重要作用。建立了3ω法测试系统，介绍了其测量各向异性材料的原理。测试了SiO₂薄膜/Si衬底试样的导热系数，验证了该实验方法及系统的合理性。应用此方法测试得到KTP晶体沿径向和倍频方向（轴向）的导热系数，得到其不均匀度为0.737。结果验证了KTP晶体导热系数的各向异性。设计的实验系统可以有效测量各向异性晶体的导热性能。     

树脂基碳纤维复合材料各向异性导热系数研究

本文通过实验测试与数值预测结合研究了平纹、斜纹树脂基碳纤维复合材料的各向异性传热性能。实验方面,采用基于电加热膜加热的稳态"三明治"结构进行测试,得到了材料厚度与面内方向导热系数随温度的变化规律。模拟方面,观测复合材料内部微观结构,重构建立了代表性单胞模型,在三维方向分别模拟其一维稳态导热过程来预测材料不同方向的导热系数。研究结果表明,实验获得的树脂基碳纤维复合材料厚度与面内方向导热系数均随材料热面温度升高而近似线性增大,面内方向导热系数约为厚度方向的2.8倍,因密度相近,平纹、斜纹机织结构材料各主轴方向导热系数偏差小于10%。数值预测结果与实验结果基本符合,并对引起实验与数值结果偏差的来源进行分析。     

双室热保护法测定真空绝热板导热系数的研究

给出了双室热保护法测定真空绝热板(VIP)的导热系数的原理,设计了测试装置.外室作为热保护装置,内室作为测试加热装置,基于稳态下测试VIP平板的导热系数,该装置不受VIP尺寸的限制.分析了影响测试结果的因素和理论误差,并与标定值对比,测试结果较精确.该装置可以用于VIP出厂前的导热系数的测试及使用过的VIP的老化程度的...     

吸附剂基质膨胀石墨的渗透率与导热系数研究

为了测试混合吸附剂基质材料石墨的传热传质特性,设计了吸附剂渗透率与导热系数测试装置,首先用平板热源法测试了散装石墨在不同膨胀温度及不同膨胀时间下的导热系数,优选出了石墨的最佳膨胀工艺,然后采用最佳膨胀工艺下的石墨进行固化,以氮气作为气源对固化石墨进行了渗透率研究,以稳态热源加热法对固化石墨进行导热系数测试,结果表明,当...     

导热系数测定过程中下铜板散热速率的理论计算

采用传热学的相关理论,对稳态法测量导热系数实验过程中下铜板的散热速率进行了计算,并与实测结果进行对比分析。     

Origin在不同材料导热系数测定中的应用

针对导热系数测定实验中数据处理不准确的问题,对牛筋、橡胶、铝三种不同材料在自然冷却和风扇冷却条件下的导热系数进行了测量,利用Origin软件进行分析比较表明,用二项式拟合和指数拟合即可得到较高的相关度,并且材料的导热系数与降温方式无关。     

冻融条件下通辽粉砂导热系数的试验研究

土体导热系数是进行寒区工程热工计算的重要参数。主要受到含水率、冻融状态等因素的影响。准确测定不同含水率和冻融条件下土体的导热系数,探究其变化规律,对寒区工程热工计算和冻害防治具有重要意义.本文对采自内蒙古通辽某高速公路的路基填土(粉质砂土)在-12.5～12.5℃的温度和0%～14%的含水率条件下进行了导热系数试验.试验结果表明:通辽粉砂导热系数随含水率的增加表现出三个阶段和两次跃变;温度对导热系数的影响随含水率增加分为两个阶段.通过对比相同含水率下正、负温区的导热系数平均值与各温度下导热系数的实测值,确定了最接近导热系数平均值的实测温度,将其定义为该含水率下的最佳测试温度,在该温度下测试导热系数可减少试验次数。     

摘要:针对导热系数测定实验中数据处理不准确的问题,对牛筋、橡胶、铝三种不同材料在自然冷却和风扇冷却条件下的导热系数进行了测量,利用Origin软件进行分析比较表明,用二项式拟合和指数拟合即可得到较高的相关度,并且材料的导热系数与降温方式无关.关键词:物理实验;导热系数;Origin软件;数据处理中图分类号:O551.3文献标志码:A

针对导热系数测定实验中数据处理不准确的问题,对牛筋、橡胶、铝三种不同材料在自然冷却和风扇冷却条件下的导热系数进行了测量,利用Origin软件进行分析比较表明,用二项式拟合和指数拟合即可得到较高的相关度,并且材料的导热系数与降温方式无关.     

铜芯线缆整体导热系数的一种测量方法

根据传热学的基本原理 ,设计了真空低温环境用于一种铜芯电缆的整体导热系数的测量。介绍了试验原理及装置 ,并测量了该电缆在低温下的导热系数。对试验数据进行了分析和处理。文中介绍的低温下导热系统的测量方法可用于同类型元器件导热系数的测量     

Copper coated nickel foam as current collector for H2S-containing syngas solid oxide fuel cells

Copper coated nickel foam with Cu/Ni ratio of 2.5 was fabricated using electrochemical plating and characterized using XRD, SEM, EDS and Van der Pauw four point conductivity measurements. Copper coated nickel foam exhibited good stability of electronic conductivity and mechanical strength during more than 150 h exposure to 500 ppm H₂S-containing syngas at 750 °C. In contrast, uncoated nickel foam readily underwent severe carbon deposition and brittle fracture resulting in dramatic increase of electronic resistance under the same testing conditions. Copper coated nickel foam is a promising current collector for H₂S-containing syngas solid oxide fuel cells (SOFCs).     

A Numerical Investigation of Nanocomposite of Copper and Titanium Dioxide in Water Based Fluid Influenced by Instigated Magnetic Region

Presence of external electrical field plays a vital role in heat transfer and fluid flow phenomena. Keeping this in view present article is a numerical investigation of stagnation point flow of water based nanoparticles suspended fluid under the influence of induced magnetic field. A detailed comparative analysis has been performed by considering Copper and Titanium dioxide nanoparticles. Utilization of similarity analysis leads to a simplified system of coupled nonlinear differential equations, which has been tackled numerically by means of shooting technique followed by Runge-Kutta of order 5. The solutions are computed correct up to 6 decimal places. Influence of pertinent parameters is examined for fluid flow, induced magnetic field, and temperature profile. One of the key findings includes that magnetic parameter plays a vital role in directing fluid flow and lowering temperature profile. Moreover, it is concluded that Cu-water based nanofluid high thermal conductivity contributes in enhancing heat transfer efficiently.     

A Numerical Investigation of Nanocomposite of Copper and Titanium Dioxide in Water Based Fluid Influenced by Instigated Magnetic Region

Presence of external electrical field plays a vital role in heat transfer and fluid flow phenomena. Keeping this in view present article is a numerical investigation of stagnation point flow of water based nanoparticles suspended fluid under the influence of induced magnetic field. A detailed comparative analysis has been performed by considering Copper and Titanium dioxide nanoparticles. Utilization of similarity analysis leads to a simplified system of coupled nonlinear differential equations, which has been tackled numerically by means of shooting technique followed by Runge-Kutta of order 5. The solutions are computed correct up to 6 decimal places. Influence of pertinent parameters is examined for fluid flow, induced magnetic field, and temperature profile. One of the key findings includes that magnetic parameter plays a vital role in directing fluid flow and lowering temperature profile. Moreover, it is concluded that Cu-water based nanofluid high thermal conductivity contributes in enhancing heat transfer efficiently.     

Molecular dynamics simulation of decomposition and thermal conductivity of methane hydrate in porous media

The hydrate has characteristics of low thermal conductivity and temperature sensitivity. To further analysis the mechanism of thermal conductivity and provide method for the exploitation, transportation and utilization of hydrate, the effect of decomposition and thermal conductivity of methane hydrate in porous media has been studied by using the molecular dynamics simulation. In this study, the simulation is carried out under the condition of temperature 253.15 K-273.15 K and pressure 1 MPa. The results show that the thermal conductivity of methane hydrate increases with the increase of temperature and has a faster growth near freezing. With the addition of porous media, the thermal conductivity of the methane hydrate improves significantly. The methane hydrate-porous media system also has the characteristics of vitreous body.With the decrease of the pore size of the porous media, thermal conductivity of the system increases gradually at the same temperature. It can be ascertained that the porous media of different pore sizes have strengthened the role of the thermal conductivity of hydrates.     

快速热响应复合材料的储/放热性能分析

以膨胀石墨为无机支撑材料、石蜡为有机相变材料,制备出高导热系数和储热密度的快速热响应复合材料,并构建传热性能测试系统对该复合材料的储/放热性能进行研究分析。研究结果表明,复合材料不仅能在熔融状态下保持形状稳定,而且显著提高了在储/放热过程的传热性能,从而有效地解决了传统相变材料高储热密度和低导热系数之间的矛盾。     

Electrical conductivity studies of mixed phthalocyanine thin films

Thin films of mixed of Copper Phthalocyanine (CuPc) and Nickel Phthalocyanine (NiPc) are deposited onto a pure glass substrate by a simultaneous thermal evaporation technique at room temperature. The material D.C. electrical conductivity of films at room temperature and also films annealed at 523 K has been investigated. The optical absorption and band gaps of the films are also measured. The results show that the electrical resistance is lower for the mixed films compared with the pure samples and also the optical band gap decreases for the mixed samples compared to the pure samples.     

Conventional interconnects: the crisis

As the design rules drop below 200 nm, a variety of problems emerges such as RC delay, electromigration resistance and heat dissipation exacerbated by increasing chip power. The use of Copper should solve resistivity and electromigration problems but reliability issue with respect to an efficient diffusion barrier is a concern. Low- k dielectrics allowing capacitance reduction have low thermal conductivity thus poor heat dissipation capability. Integration of Copper and low- k dielectrics is intensively studied world wide. The following gives an overview of the international state of the art to overcome critical issues of advanced interconnects.     

疏导式结构在头锥热防护中的应用

针对高超声速飞行器工作时头锥恶劣的热环境,为了保证飞行器头锥的尖锐外形, 提出疏导式热防护结构,利用内置高导热碳材料结构为飞行器头锥提供热防护. 采用流固耦合方法对头锥疏导式防热结构进行了分析,验证了头锥内置高导热碳材料具有较好防热效果, 其中来流马赫数(Ma)为9时头锥前缘壁面最高温度下降了21.9%,尾部最低温度升高了15.2%, 实现了热流由高温区向低温区的转移,削弱了头锥的热载荷,强化了头锥的热防护能力. 本文对外蒙皮结构参数、材料参数以及内部高导热碳材料导热率对头锥热防护性能的影响进行了分析, 其中头锥最高温度随着蒙皮材料导热系数的增加而降低到一个稳定值; 随着蒙皮材料表面黑度的增加而降低;随着蒙皮厚度的增加而升高;随着高导热碳材料导热系数的 增加而呈抛物线下降.     

CO_2水合物导热特性的分子动力学模拟

使用分子动力学模拟方法在NVT系综下对结构完整CO_2水合物以及结构缺陷CO_2水合物进行了导热模拟计算.对于结构完整的CO_2水合物,在200-230 K温度区间内,体系导热系数由0.4684 W·m~(-1)·K~(-1)变化到0.4836 W·m~(-1)·K~(-1),温度相关性较弱;而在230-280 K温度区间内,体系导热系数由0.4836 W·m~(-1)·K~(-1)变化到0.7494 W·m~(-1)·K~(-1),温度相关性变强;另外,通过计算功率图谱发现主体分子对水合物体系的导热贡献更大.对于结构缺陷CO_2水合物,发现晶穴占有率和笼形结构缺陷对体系导热均有一定影响,空笼晶胞导热系数约为完整晶胞导热系数的86.67%,体系的导热能力主要取决于主体结构的性质.     

粒径均匀散体导热系数的分形描述

本文以分形理论为工具,采用填充率、散体颗粒直径等宏观易等测参数较准确地描述了颗粒散体的几何结构;运用导热与逾渗的类比,建立了均匀散体导热系数的逾渗模型,模型的预测值与实验测量结果基本一致。