Papers by Keyword: Thermal Conductivity (TC)

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Authors: Soo Woong Lee, Nam Jin Song, Jinwook Burm, Chul An
Authors: Dan Li
Abstract: Well-dispersed and hydrophilic copper nanoparticles have been synthesized from an organometallic precursor in an organic (or oil) phase. There are two layers coated on the surface of the copper nanoparticles. The coating layer can not be dissolved or rinsed off by organic media. The changing of viscosity and enhancement of the thermal conductivity of copper nanofluids is also presented.
Authors: Wei Ting Jiang
Abstract: Nanoparticles in nanofluids are in the form of nanoparticle clusters caused by aggregation. In order to calculate the thermal and electric conductivity of the nanofluids, the growth process and three-dimensional space structure of the nanoparticle cluster in the host fluid is simulated, and then the thermal and electric conductivity of the cluster are calculated with the resistance network method. The thermal and electric conductivity of the nanofluid are calculated based on the simulated thermal and electric conductivity of nanoparticle clusters, the volume fraction of nanoparticle clusters to the nanofluid as well as the liquid molecule adsorption layer of the nanoparticle. The simulation method is validated by experimental data.
Authors: Ya Fen Han, Xin Lin Xia, Hai Dong Liu
Abstract: A Modified Monte-Carlo Method (MMCM) in which phonon bundles take non-energy is developed to model the steady state phonon radiative transfer in nanoscale materials. Heat transfer in silicon thin films is analyzed to examine the validity of the developed method. The temperature distributions and cross-plane thermal conductivity are determined by using the developed method for the silicon thin films and compared with the results in reference. The results indicate that the developed method has a good accuracy in solving the phonon radiative transfer in nanoscale materials. In addition, numerical accuracy can be improved by the increase of the number of samples in the simulations.
Authors: Hai Bo Wang, Zi Zeng Lin, Zhong Yi He
Abstract: Series of experimental tests on the forming technique, sintering technique, performance and effectiveness of a new fired brick by mixing municipal sewage sludge and shale are carried out. Test results show that adding sludge properly in the process of manufacture shale fired common brick is feasible. Along with increase of sludge content, the compacting of uniformity of unburned brick decreased and its porosity increased. When shale-sludge mixtures were calcined, the heavy metal solidified, the ignition lost and organic substance volatilized that reduced the unconfined compressive strength (UCS) of the brick and improve its thermal insulation ability. The phase composition and leaching toxicity of sewage sludge-shale baked brick can be up to national standard. Good quality brick can be produced by blending mixture with the optimum moisture content (OMC) 18.0%-20.0%, drying at 105°C and sintering at 960°C. With all being considered in manufacturing brick, the content of sewage sludge shall be controlled within 9.0% that can make UCS of the new brick reach MU10 criterion and it has a superior heat preservation effect to normal brick from clay or shale alone.
Authors: Roland Rupp, Fanny Björk, Gerald Deboy, Matthias Holz, Michael Treu, Jochen Hilsenbeck, Ralf Otremba, Hannes Zeichen
Abstract: With the help of an improved die attach the Rth,jc of SiC Schottky diodes can be reduced by 40-50% at a given chip size. This enables a significant higher power density for these SiC diode chips, resulting in a chip shrink of ~ 35% for a given nominal current. This has a significant impact not only on the cost position of the device but also on the switching performance of the diodes, as their capacitive charge directly scales with the chip area. Of course these advantages are accompanied by a small penalty in static losses as the Vf of the diodes at nominal current also slightly increases by the chip shrink. However, the reduction of switching losses dominates upon the marginally increased static losses besides full load operation conditions (which are pretty exceptional in today’s SiC Schottky diode applications) combined with frequencies below 130 kHz. This allows a better competitive positioning against fast Si-based diodes and improved system efficiency at the same time.
Authors: Sheng Qiang, Chao Wu, Nan Nan Zhang, Zhi Qiang Xie
Abstract: The real thermal parameters always have inevitable influence on the simulation results of the structure thermal field and stress field in the construction of mass concrete. A new measuring and calculation method for concrete thermal conductivity was put forward. Eight or six sensor points measuring method and calculation formula are present, and the latter is the simplification of the former. Comparing the real thermal conductivity with the calculation result by the new method, it can be seen that the thermal conductivity can be obtained within about 6 day’s age at site and with the accurate degree of 98%. The new method will provide an efficient way for the concrete structure researcher and designer.
Authors: Xiang Yu Li, Xiao Long Zhao, Xiang Yong Guo, Li Qiang Cao
Abstract: A new theoretical equation that represents the thermal conductivity of two-phase composite has been proposed. The Cheng-Vachon equation has been modified by introducing a new parameter that is the corrected porosity. It was found that the new equation can describe the thermal conductivity of cellular concrete very accurately. Development of the equation is helpful to understanding heat transfer mechanism and improving thermal property of cellular concrete.
Authors: Long Gang Wan, Zhi Gang Huang, Shao Rong Song, Jia Ping Wang, Jie Li
Abstract: Based on SiC aggregate, SiC powder and ultra-fine SiC powder as the main starting materials and B4C as additive, the newly-developed self-bonded SiC material was pressed and fired at 2200°C for 10 hours in Ar environment in the high-temperature furnace. The phase composition and microstructure were investigated. In the paper, traditional self-bonded SiC material and Si3N4-bonded SiC material were taken for comparison with the newly-developed self-bonded SiC material in terms of strength, thermal conductivity, cryolite resistance, molten alkali resistance and oxidation resistance etc. The results show that the newly-developed self-bonded SiC material contains 98.42% α-SiC and presents obvious higher thermal conductivity than traditional self-bonded SiC material and much better cryolite resistance, molten alkali resistance and oxidation resistance than traditional self-bonded SiC and Si3N4-bonded SiC materials.
Authors: Zi Sheng Wang, Hao Chi Tu, Jin Xiu Gao, Guo Dong Qian, Xian Ping Fan, Zhi Yu Wang
Abstract: Aerogel is regarded as one kind of super thermal insulation materials which could be large-scalely used as building materials. However, the aerogel’s production cost and poor mechanical property limit the its applications. In this paper, we put forward a new low cost way to produce a novel building thermal insulation material: synthesized the aerogel within the expanded perlite’s pores, and using sodium silicate as precursor without adopting supercritical fluid drying and surface modification. The thermal conductivity of expanded perlite was successfully decreased after modified by aerogel.
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