气体导热率理论方程和两个定理

分析了杰出科学家Maxwell等的理论方程普适性差精确度低的深刻理论根源,是难以消除的严重缺陷。利用氩模型及其微分方程导出气体导热率理论方程,并以逻辑推理建立2个定理。作者方程经用极性与非极性以及量子气体等24种结构类型178种有机与无机纯质802个实验数据验证,平均误差仅1.71％,达到实验允许误差范围内,比科学家公认的非平衡态统计力学上最重大成就之一的Enskog-Chapman理论方程的精度高5倍以上,比Chung式高3.5倍。证明解决了当代化学工程与非平衡态统计力学交叉学科领域内极需解决的科学难题之一,有很大的理论意义和应用价值,是这一领域的重大突破。

论物质的分子结构与液体导热率理论方程

分析了在国际化学化工学术界有影响的Ｂｒｉｄｇｍ ａｎ 理论式及著名的Ｌａｔｉｎｉ经验式的不足后，以张克武气体不平衡状态理论方程导出的液体导热率理论方程和有机分子的半金属结构理论为基础，建立了用分子结构来计算液体导热率的理论方程．以液烃、醚、醛、酮和酯等２５６ 种纯质８５０ 个实验数据检验，平均误差１．８％ ，其精确度比Ｂｒｉｄｇｍ ａｎ 理论式约高１０ 倍，比Ｌａｔｉｎｉ式高５ 倍，显著优于前人公式．

填充型导热橡胶研究开发现状

综述了填充型导热橡胶的典型理论模型和导热机理,介绍了单组分导热填料填充体系和多组分导热填料填充体系的国内外研究开发状况,指出了今后导热橡胶的开发方向。

柔性导热纳米复合材料研究进展

柔性导热纳米复合材料在微电子、航空航天、智能驱动等领域具有广泛的应用。综述了以零维纳米粒子、一维纳米纤维和二维纳米片层为填料的柔性导热纳米复合材料的最新研究进展。概述了柔性导热纳米复合材料的研究中存在的主要问题及解决方法。纳米填料的分散性差是阻碍柔性导热纳米复合材料发展的重要问题,可采用物理包覆法、偶联剂法、接枝改性等方法对纳米填料进行表面修饰,提高纳米填料的分散性及与基体的结合性,从而提高材料的导热性能;另外完善导热机制的理论研究,建立导热微观模型,可为柔性导热纳米复合材料的实际应用提供重要依据。开发新型纳米填料,特别是混合填料体系是改善柔性导热纳米复合材料综合性能的重要途径。

导热高分子材料的研究新进展

总述了导热高分子材料的典型理论模型和导热机理;并对国内外导热高分子材料的研究开发现状作了详细介绍;最后提出了导热高分子材料综合性能提高的途径。

导热橡胶模型及导热橡胶的应用研究进展

对导热橡胶的导热机理、导热模型及其应用研究进展进行论述。导热橡胶的导热性能最终由橡胶基体和导热填料综合作用决定。导热填料根据形态分为粉状填料、片状填料和纤维状填料,可单独或并用填充导热橡胶;采用不同导热橡胶典型理论模型对不同填料填充导热橡胶进行预测,其结果与实测值吻合良好。目前,对导热橡胶的研究主要集中在填料表面改性和粒径分布等方面。如何大幅提高导热橡胶的热导率,提高其热疲劳性能、热力学性能及在使用中的稳定性,是未来导热橡胶研究的核心。

导热硅橡胶的研究进展

综述了导热橡胶的典型理论模型和导热机理,并对国内外导热硅橡胶的研究现状做了详细介绍。硅橡胶的导热性主要取决于硅橡胶基体、填料、以及加工工艺三个方面的因素。填料的导热性、添加量及其在基体中的分布形式对硅橡胶的导热性能起着关键作用。

填料对地热井固井材料导热性能的影响

在地热井固井水泥中加入导热填料能够明显改善水泥石导热性能,提升地热井取热效果。在总结导热路径理论和紧密堆积理论的基础上,通过试验研究不同填料种类、粒径及掺量对固井水泥导热性能的影响。试验结果表明:较其他种类填料,石墨对水泥石导热性能提升效果最好;石墨粒径越大对应水泥石导热系数越高。不同粒径的石墨混合,较单一粒径石墨对水泥石导热性能的提升效果更好,其最优混合配比为:石墨粒径为150μm与100μm,质量比为2︰1。随着石墨掺量增加,固井材料的导热系数逐渐增大,但流动度和48 h抗压强度逐渐降低。参照固井相关规范,提出固井材料中石墨掺量应控制在9%左右为宜。研究成果为地热井高导热固井材料的制备提供借鉴。

碳纳米管/聚丙烯腈基复合材料的热导率研究

采用原位聚合法制备了碳纳米管/聚丙烯腈(CNT/PAN)复合材料,用MDSC的测试方法研究了复合材料的热性能,并由此推导了复合材料的热导率。应用Cheng-Vachon、Nielsen-Lewis和Okamoto-Ishida3种导热理论模型对CNT/PAN复合材料的热导率进行估算。对比实验测试与导热理论模型的计算结果,考虑到碳纳米管在聚合物基体中的分散和取向情况,得出Nielsen-Lewis理论在低填充含量及室温条件下可以较准确地估算无规分散的CNT/PAN复合材料体系的热导率。

贵州省兴义市下午屯地下热水资源形成条件分析

地下热水是一种非常宝贵的矿产资源,也是一种清洁可再生资源,开发利用地热资源对促进地方经济发展和国家节能减排均具有重要作用。本文通过贵州省兴义市下午屯地区区域地质、水文地质、地球物理情况,来研究区域断层特征,总结断层的导热规律,以及贵州省兴义市下午屯地下热水资源赋存规律,丰富了该地区的储热—导热理论。

Theoretical expressions of thermal conductivity of wood

In this paper, the theoretical expressions of wood thermal conductiv ity in the choral and radical direction are derived from the micro-structure of wood by applying some basic principles in physical mechanics. The thermal conduc tivities of about twenty species of trees were calculated by means of the expres sions and compared with its experimental values under the same condition. The av erage relative error is about 5%, so the calculation result is satisfactory.

Theoretical solution of transient heat conduction problem in one-dimensional double-layer composite medium

To make heat conduction equation embody the essence of physical phenomenon under study, dimensionless factors were introduced and the transient heat conduction equation and its boundary conditions were transformed to dimensionless forms. Then, a theoretical solution model of transient heat conduction problem in one-dimensional double-layer composite medium was built utilizing the natural eigenfunction expansion method. In order to verify the validity of the model, the results of the above theoretical solution were compared with those of finite element method. The results by the two methods are in a good agreement. The maximum errors by the two methods appear when τ（τ is nondimensional time） equals 0.1 near the boundaries of ζ =1 （ζ is nondimensional space coordinate） and ζ =4. As τ increases, the error decreases gradually, and when τ =5 the results of both solutions have almost no change with the variation of coordinate 4.

Fractal analysis of thermal conduction of loose coal

For deep mining engineering, heat transfer of coal mass is a vital factor in the thermal environment of coal mines. In order to study the thermal conduction mechanism, we obtained gray images of coal mass microstructure by scanning samples with a digital microscope. With the use of Matlab, these gray images were transformed into binary images, which were then transformed into a corresponding matrix consisting only of the values 0 and 1. According to the calculation method of box-counting dimension, we calculated the fractal dimension of the loose coal to be approximately 1.86. The thermal conductivity expressions of loose coal were derived based on the simulation method of thermal resistance. We calculated the thermal conductivity of loose coal by using a fractal model and compared the calculated values with our experimental data. The results show that the test data show an encourag-ing agreement with the calculated values. Hence fractal theory is a feasible method for studying thermal conductivity of loose coal.

Oxidative heat release intensity in coal at low temperatures measured by the hot-wire method

Directly measuring the oxidative heat release intensity at low temperatures is difficult at present.We developed a new method based on heat conduction theory that directly measures heat release intensity of loose coal at low temperatures.Using this method, we calculated the oxidative heat release intensity of differently sized loose coals by comparing the temperature rise of the coal in nitrogen or an air environment.The results show that oxidation heat release intensity of Shenhua coal sized 0～15 mm is 0.001～0.03 W/m3 at 30～90 °C and increases with increasing temperature.The heat release intensity at a given temperature is larger for smaller sized coal.The temperature effect on heat release intensity is muted as the coal size increases.At lower temperature the change in heat release intensity as a function of size becomes smaller.These results show that the test system is usable for practical applications and is easy to operate and is capable of measuring mass samples.

Research on Construction Process of EPS in the Thermal Insulation Building

In order to improve the efficiency of EPS integral thermal insulation building design and optimize the construction process of insulation construction, this paper uses experiment parts and simulation form to design the thermal insulation construction process, and evaluates the effect of heat preservation. Based on the finite element theory this paper designs adding process of insulation material EPS in the thermal insulation layer, and establishes the radiation heat conduction model of EPS material, finally obtains the solid heat conduction equation. Finally this paper uses ANSYS software to do simulation on the strength and temperature of EPS construction, and evaluates the quality of construction works, which provides technical reference for the design of integrated thermal insulation buildings.

Determination of Effective Thermal Conductivity ForReal Porous Media Using Fractal Theory

In this paper, using fractal theory3 the geometric structure of real soil was described with its sectionview and section particle area fractal dimension d of porous media was counted. The volumetric solidcontent and the relation between volumetric solid content and porous media particle arrangementsas well as measure scale were obtainted. A heat conduction model was established and the effectivethermal conductivity of real soil based on the volumetric solid content was calculated.

Exothermic process of cast-in-place pile foundation and its thermal agitation of the frozen ground under a long dry bridge on the Qinghai-Tibet Railway

A number of dry bridges have been built to substitute for the roadbed on the Qinghai-Tibet Railway,China.The aim of this study was to investigate the exothermic process of cast-in-place (CIP) pile foundation of a dry bridge and its harm to the stability of nearby frozen ground.We present 3D heat conduction functions of a concrete pile and of frozen ground with related boundaries.Our analysis is based on the theory of heat conduction and the exponent law describing the adiabatic temperature rise caused by hydration heat.Results under continuous and initial conditions were combined to establish a finite element model of a CIP pile-frozen ground system for a dry bridge under actual field conditions in cold regions.Numerical results indicated that the process could effectively simulate the exothermic process of CIP pile foundation.Thermal disturbance to frozen ground under a long dry bridge caused by the casting temperature and hydration heat of CIP piles was substantial and long-lasting.The simulated thermal analysis results agreed with field measurements and some significant rules relating to the problem were deduced and conclusions reached.

Measurement of boiling heat transfer coefficient in liquid nitrogen bath by inverse heat conduction method

Inverse heat conduction method (IHCM) is one of the most effective approaches to obtaining the boiling heat transfer coefficient from measured results. This paper focuses on its application in cryogenic boiling heat transfer. Experiments were conducted on the heat transfer of a stainless steel block in a liquid nitrogen bath, with the assumption of a 1D conduction condition to realize fast acquisition of the temperature of the test points inside the block. With the inverse-heat conduction theory and the explicit finite difference model, a solving program was developed to calculate the heat flux and the boiling heat transfer coefficient of a stainless steel block in liquid nitrogen bath based on the temperature acquisition data. Considering the oscillating data and some unsmooth transition points in the inverse-heat-conduction calculation result of the heat-transfer coefficient, a two-step data-fitting procedure was proposed to obtain the expression for the boiling heat transfer coefficients. The coefficient was then verified for accuracy by a comparison between the simulation results using this expression and the verifying experimental results of a stainless steel block. The maximum error with a revised segment fitting is around 6%, which verifies the feasibility of using IHCM to measure the boiling heat transfer coefficient in liquid nitrogen bath.

Estimation of thermophysical properties of solid propellants based on particle packing model

A method for the estimation of thermophysical properties of two-and multi-phase solid propellants is proposed in this paper.The theoretical solutions for thermal conductivity and specific heat of a homogeneous solid propellant cell in the transient thermal conductivity process are deduced on the condition that one boundary of the cell is heated while others are adiabatic.A homogenization theory and the finite element method are employed to compute the mean temperature and heat flux of a representative volume element(RVE).According to the mean results and the theoretical solutions,the effective thermal conductivity and specific heat of solid propellant can be estimated.A packing algorithm,considering the solid particles(ammonium perchlorate(AP)or aluminum)as spheres or discs,is used to match the size distribution and volume fraction of solid propellants,and some mesoscopic models of two-phase and three-phase solid propellants are established.According to the estimation theory proposed in this paper,the effective thermal conductivity and specific heat of solid propellants are predicted.The effect of AP or Al volume fraction is also discussed in this paper.

A high-efficiency aerothermoelastic analysis method

In this paper,a high-efficiency aerothermoelastic analysis method based on unified hypersonic lifting surface theory is established.The method adopts a two-way coupling form that couples the structure,aerodynamic force,and aerodynamic thermo and heat conduction.The aerodynamic force is first calculated based on unified hypersonic lifting surface theory,and then the Eckert reference temperature method is used to solve the temperature field,where the transient heat conduction is solved using Fourier’s law,and the modal method is used for the aeroelastic correction.Finally,flutter is analyzed based on the p-k method.The aerothermoelastic behavior of a typical hypersonic low-aspect ratio wing is then analyzed,and the results indicate the following:(1)the combined effects of the aerodynamic load and thermal load both deform the wing,which would increase if the flexibility,size,and flight time of the hypersonic aircraft increase;(2)the effect of heat accumulation should be noted,and therefore,the trajectory parameters should be considered in the design of hypersonic flight vehicles to avoid hazardous conditions,such as flutter.