Papers by Keyword: Thermal Conductivity (TC)

Abstract: The top of COREX-3000 gasifier was numerical simulated and investigated the relationship between thermal conductivity and the thermal-stress field. It is concluded that when the thermal conductivity of the working lining and permanent lining is respectively 0.95W / (m•K) and 0.5 W / (m•K), the change rate of the top stress along radical direction is minimum.

Abstract: The VIPs consist of the glass-fiber core material and two types of envelope film. The glass fiber was fabricated by a centrifugal blowing process. The core material was prepared by the wet method. The thermal conductivities of the materials were measured by the heat flow meter. The microstructure of the envelope film was observed by scanning electron microscopy. The porosity ratio and largest pore size diameters of the core materials are 92.27% and 20μm, respectively. The thermal conductivity of the VIP is about 8-10 times higher than that of the core materials. The thickness of type I and II envelope films are 45μm and 400μm, respectively. The thermal conductivities of the type I and type II envelope films are 0.11W/(m•K) and 0.69W/(m•K), respectively. The thermal conductivity of the VIP with type II envelope is higher than that of the VIP with type I envelope, which is attributed to the different structures and thickness of the envelope film.

Abstract: Polycrystalline filled Skutterudite compounds Ba_xCo₄Sb₁₂ (0-x-0.5) are synthesized by high pressure and high temperature （HPHT） technique. The thermal conductivity for CoSb₃ is depressed significantly by Ba-filling combined HPHT technique. The value of 1.25 Wm^-1 K^-1 for Ba_0.372Co₄Sb₁₂ is obtained at 633K. The dimensionless thermoelectric figure of merit ZT, increases with temperature increasing and reaches a maximal value of 1.01 at 663 K.

Abstract: Cu-10Ni-5Mo alloys have been prepared by arc-melting and induction melting injection moulding. The effects of melting processes on the microstructure and thermal conductivity of Cu-10Ni-5Mo alloys were studied. The results show that the grain of Cu-10Ni-5Mo alloy prepared by arc-melting is coarse and the structure includes α solid solution and Mo-Ni phase. The grain of Cu-10Ni-5Mo alloy prepared by induction melting injection moulding is superfine and the structure is α solid solution. Under this experiment condition, the coefficient of thermal conductivity of Cu-10Ni-5Mo alloy prepared by arc-melting is 56.9 W/(m•K)，while that of Cu-10Ni-5Mo alloy prepared by induction melting injection moulding is 35.7 W/(m•K). The melting points of Cu-10Ni-5Mo alloy prepared by two methods all increase and are little different.

Abstract: Lithium is widely used in the pharmaceutical industry, fuel cell, ceramic industry, glass, lubricants, aluminum industry, refrigerant, nuclear industry and photovoltaic industry. The thermal properties of lithium are very important for the design and safe operation. The MEAM potential was applied to calculate thermal conductivity of lithium with emphasis on size effect analysis in the lithium nanometer film using non-equilibrium molecular dynamics simulation method. The results show that the lithium thermal conductivity increases with increasing film thickness. The obvious size effect and anisotropy of thermal conductivity are found in the lithium nanometer film. From the simulation results, the difference of normal and tangential thermal conductivity has been analyzed quantitatively.

Abstract: The grain-size dependences of thermal conductivity and electrical resistivity of polycrystalline and nanocrystalline nickel were measured by the flash method and four-point probe method, respectively. Nanocrystalline nickel (grain size: 28 nm) was made by the pulsed-current electrodeposition process, while polycrystalline nickel (grain size: 57 μm) was the same material in fully annealed condition. Noticeable differences in thermal conductivity and electrical resistivity were observed for both materials. These results can be explained on the basis of the rapid increase in the intercrystalline grain boundary and triple junction volume fractions at very small grain sizes. The relationship between thermal conductivity and electrical resistivity of nanocrystalline nickel follows the classic Wiedemann-Franz law.

Abstract: The aim of the paper is to analyze the effect of the additives on thermal conductivity of the phase change material. The experiment about heat storage and heat release performance of the composite phase change material which uses sodium acetate trihydrate as host material is studied. The effect of the expanded graphite on the composite phase change material is investigated. The results show that: expanded graphite which can be dispersed evenly in the composite phase change material, the thermal stability is well, significantly improve the thermal conductivity of the composite phase change material.

Abstract: Nanoscale copper particles were synthesized by chemical reduction with polyvinyl pyrrolidone as dispersant, ascorbic acid as reduction agent, copper sulfate pentahydrate and ammonia as reagent. X-ray diffraction (XRD) analysis revealed that as-prepared copper nanoparticle was well crystallized without other impurities. Transmission electron microscopy (TEM) displayed that nanoscale coppers had homogenous distribution and the particle size was about 30~50 nm. Uniform and stable Cu-nanofluids were prepared by general stirring, high speed shear stirring and ultrasonic, with water/ethylene glycol as base fluid and as-synthesized copper nanoparticles as additives. The thermal conductivity of Cu-nanofluid was measured by a short-hot wire method. The results showed that the thermal conductivity of Cu-nanofluid was increased 8~9% compared to base fluid and the temperature had little effect on the enhancement of the thermal conductivity.

Abstract: Cu-11Ni-2W alloys have been prepared by vacuum non-consumable arc-melting and high-frequency induction melting injection moulding. The effects of melting processes on the resultant microstructure were studied. The results show that the grain of Cu-11Ni-2W alloy prepared by vacuum non-consumable arc-melting is coarse and the microstructure includes α solid solution and W particles. As for the sample prepared by high-frequency induction melting injection moulding, the grain is superfine and the microstructure is α solid solution. Moreover, the thermal conductivity coefficient for the sample prepared by vacuum non-consumable arc-melting is 67.2 W/(m•K), while that for high-frequency induction melting injection moulding is 47.8 W/(m•K). The melting point of Cu-11Ni-2W alloy prepared by vacuum non-consumable arc-melting is 1157.27°C.

Abstract: With the devices miniaturization, the properties of materials at the micro/nano scale were much different from what at Macro-scale because of the scale effect. The Interface Stress Element (ISE) was introduced into the multi-scale model. These three methods, Molecular Dynamics (MD), ISE and Finite Element (FE) were effectively combined by designing a handshake region and using the transition interface element method. The multi-scale model of film was built based on MD-ISE-FE. The sequential coupling method was used to calculate, and then, the results of the FE and ISE region were applied to the MD region. The EAM potential was used to simulate. The results were the basically same with the other experimental and simulation results in the reference. It indicated that the multi-scale analysis method could be applied to calculate the thermodynamics properties of the interface structure at the Micro/nano scale.