Готові списки джерел за темами / Thermal conductivities

Добірка наукової літератури з теми "Thermal conductivities"

Автор: Grafiati

Опубліковано: 13 липня 2022

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Статті в журналах з теми "Thermal conductivities":

Jang, Seok-Pil. "Thermal Conductivities of Nanofluids." Transactions of the Korean Society of Mechanical Engineers B 28, no. 8 (August 1, 2004): 968–75. http://dx.doi.org/10.3795/ksme-b.2004.28.8.968.

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Wu, Guoqiang, Zhaowei Sun, Xianren Kong, and Dan Zhao. "Molecular dynamics simulation on the out‐of plane thermal conductivity of single‐crystal silicon thin films." Aircraft Engineering and Aerospace Technology 77, no. 6 (December 1, 2005): 475–77. http://dx.doi.org/10.1108/00022660510628462.

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PurposeCombining the characteristic of satellite “minisize nucleus” non‐equilibrium molecular dynamics (NEMD) method is used. We select corresponding Tersoff potential energy function to build model and, respectively, simulate thermal conductivities of silicon nanometer thin film.Design/methodology/approachNEMD method is used, and the corresponding Tersoff potential energy function is used to build model.FindingsThe thermal conductivities of silicon nanometer thin film are markedly below the corresponding thermal conductivities of their crystals under identical temperature. The thermal conductivities are rising with the increase of thickness of thin film; what's more, the conductivities have a linear approximation with thickness of the thin film.Research limitations/implicationsIt is difficult to do physics experiment.Practical implicationsThe findings have some theory guidance to analyze satellite thermal control.Originality/valueThe calculation results of thermal conductivities specify distinct size effect. The normal direction thick film thermal conductivity of silicon crystal declines with the increasing temperature. The thermal conductivities are rising with the increase of thickness of thin film; what's more, the conductivities have a linear approximation with thickness of the thin film.

Hands, D., K. Lane, and R. P. Sheldon. "Thermal conductivities of amorphous polymers." Journal of Polymer Science: Polymer Symposia 42, no. 2 (March 8, 2007): 717–26. http://dx.doi.org/10.1002/polc.5070420223.

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DiGuilio, Ralph M., William L. McGregor, and Amyn S. Teja. "Thermal conductivities of the ethanolamines." Journal of Chemical & Engineering Data 37, no. 2 (April 1992): 242–45. http://dx.doi.org/10.1021/je00006a029.

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Maloka, I. E. "Thermal Conductivities of Liquid Mixtures." Petroleum Science and Technology 25, no. 8 (August 2007): 1065–72. http://dx.doi.org/10.1081/lft-200041074.

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Lovell, M. A. "Thermal conductivities of marine sediments." Quarterly Journal of Engineering Geology and Hydrogeology 18, no. 4 (November 1985): 437–41. http://dx.doi.org/10.1144/gsl.qjeg.1985.018.04.14.

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Midttømme, K., E. Roaldset, and P. Aagaard. "Thermal conductivities of argillaceous sediments." Geological Society, London, Engineering Geology Special Publications 12, no. 1 (1997): 355–63. http://dx.doi.org/10.1144/gsl.eng.1997.012.01.33.

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Rowley, Richard L., Gary L. White, and Mudau Chiu. "Ternary liquid mixture thermal conductivities." Chemical Engineering Science 43, no. 2 (1988): 361–71. http://dx.doi.org/10.1016/0009-2509(88)85049-8.

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Tang, Boning, Chuanqing Zhu, Ming Xu, Tiange Chen, and Shengbiao Hu. "Thermal conductivity of sedimentary rocks in the Sichuan basin, Southwest China." Energy Exploration & Exploitation 37, no. 2 (October 29, 2018): 691–720. http://dx.doi.org/10.1177/0144598718804902.

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The optical scanning method was adopted to measure the thermal conductivities of 418 drill-core samples from 30 boreholes in Sichuan basin. All the measured thermal conductivities mainly range from 2.00 to 4.00 W/m K with a mean of 2.85 W/m K. For clastic rocks, the mean thermal conductivities of sandstone, mudstone, and shale are 3.06 ± 0.73, 2.57 ± 0.42, and 2.48 ± 0.33 W/m K, respectively; for carbonate rocks, the mean thermal conductivities of limestone and dolomite are 2.53 ± 0.44 and 3.55 ± 0.71 W/m K, respectively; for gypsum rocks, the mean thermal conductivity is 3.60 ± 0.64 W/m K. The thermal conductivities of sandstone and mudstone increase with burial depth and stratigraphic age, but this trend is not obvious for limestone and dolomite. Compared with other basins, the thermal conductivities of sandstone and mudstone in Sichuan basin are distinctly higher, while the thermal conductivities of limestone are close to Tarim basin. The content of mineral composition such as quartz is the principal factor that results in thermal conductivity of rocks differing from normal value. In situ thermal conductivity of sandstones was corrected with the consideration of water saturation. Finally, a thermal conductivity column of sedimentary formation of the Sichuan basin was given out, which can provide thermal conductivity references for the research of deep geothermal field and lithospheric thermal structure in the basin.

Goo, Nam Seo, and Kyeongsik Woo. "Measurement and Prediction of Effective Thermal Conductivity for Woven Fabric Composites." International Journal of Modern Physics B 17, no. 08n09 (April 10, 2003): 1808–13. http://dx.doi.org/10.1142/s0217979203019708.

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The current paper deals with the measurement and prediction of thermal conductivities for plain weave fabric composites. An experimental apparatus was setup to measure the temperature gradients from which the thermal conductivities were obtained. The thermal conductivities were also calculated using finite element analyses for plain weave unit cell models and then compared with experimental results. In addition, the effect of a phase shift and the fiber volume fraction in the tow on the thermal conductivities was addressed.

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Дисертації з теми "Thermal conductivities":

Yao, Yulong. "THERMAL CONDUCTIVITIES OF ORGANIC SEMICONDUCTORS." UKnowledge, 2017. http://uknowledge.uky.edu/physastron_etds/48.

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Organic semiconductors have gained a lot of interest due to their ease of processing, low-cost and inherent mechanical flexibility. Although most of the research has been on their electronic and optical properties, knowledge of the thermal properties is important in the design of electronic devices as well. Our group has used ac-calorimetric techniques to measure both in-plane and transverse thermal conductivities of a variety of organic semiconductors including small-molecule crystals and polymer blends. For layered crystals composed of molecules with planar backbones and silylethynyl (or germylethynyl) sidegroups projecting between the layers, very high interplanar thermal conductivities have been observed, presumably implying that heat flows between layers mostly via interactions between librations on these sidegoups. Since most organic semiconducting devices require materials in thin film rather than bulk crystal form, I have focused on using the “3ω- technique” to measure the thermal resistances of thin films of this class of organic semiconductors, including bis(triisopropylsilylethynyl) pentacene (TIPS-pn), bis(triethylsilylethynyl) anthradithiophene (TES-ADT), and difluoro bis(triethylsilylethynyl) anthradithiophene (diF-TES-ADT). For each material, several films of different thicknesses have been measured to separate the effects of intrinsic thermal conductivity from interface thermal resistance. For sublimed films of TIPS-pn and diF-TES-ADT, with thicknesses ranging from less than 100 nm to greater than 4 μm, the thermal conductivities are similar to those of polymers and over an order of magnitude smaller than those of single crystals, presumably reflecting the large reduction in phonon mean-free path due to disorder in the films. On the other hand, the thermal resistances of thin (≤ 205 nm) crystalline films of TES-ADT, prepared by vapor-annealing of spin-cast films, are dominated by their interface resistances, possibly due to dewetting of the film from the substrate during the annealing process.

Agab, Ali Faisal. "Hydraulic and thermal conductivities of soils." Thesis, University of Newcastle Upon Tyne, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.417418.

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Tang, Xiaoli Dong Jianjun. "Theoretical study of thermal properties and thermal conductivities of crystals." Auburn, Ala, 2008. http://repo.lib.auburn.edu/EtdRoot/2008/SUMMER/Physics/Dissertation/Tang_Xiaoli_9.pdf.

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Rowan, Linda. "The measurement of the thermal conductivity of gaseous mixture using the transient hot wire technique." Thesis, University of Leeds, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.252676.

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Zhang, Hantao S. M. Massachusetts Institute of Technology. "Computational investigation of the thermal conductivities and phonon properties of strontium cobalt oxides." Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/123356.

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This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Thesis: S.M., Massachusetts Institute of Technology, Department of Nuclear Science and Engineering, 2019
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 87-91).
The thermal conductivities of electrochemically tuned strontium cobalt oxides (SCO) are significantly different among the perovskite SrCoO3 (P-SCO), the brownmillerite SrCoO2.5 (BM-SCO) and the hydrogenated HSrCoO2.5 (H-SCO)1. The underlying mechanism causing this large difference is still unclear. And phonon properties in SCO have not been investigated thoroughly or have some contradictive predictions. In this work, we have calculated the thermal conductivities in P-SCO and BM-SCO by applying molecular and lattice dynamics, and successfully reconstructed the large difference of the thermal conductivities, consistent with measurements. Furthermore, several phonon properties including heat capacities, group velocities, lifetimes and mean free paths have been calculated, and the key roles of local atomic environment and crystal symmetry in determining the thermal conductivities have been identified. We have also analyzed the impact of interfaces, isotropic strains and defects on thermal conductivities, predicted the neutron scattering intensity in P-SCO, and tested the accuracy and performance of molecular dynamics based on deep learning. Additionally, even though the calculations about the phonon properties in H-SCO are not complete, it still offers some inspirations about its thermal conductivity. The thorough investigations about the phonon properties and the mechanisms determining the thermal conductivities in SCO may benefit future research about tunable thermal conductivities in complex oxides.
by Hantao Zhang.
S.M.
S.M. Massachusetts Institute of Technology, Department of Nuclear Science and Engineering

Zuo, Yanjia. "Preparation of silica aerogels with improved mechanical properties and extremely low thermal conductivities through modified sol-gel process." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/64600.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2010.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 90-96).
Reported silica aerogels have a thermal conductivity as low as 15 mW/mK. The fragility of silica aerogels, however, makes them impractical for structural applications. The purpose of the study is to improve the ductility of aerogels while retain the low thermal conductivity of silica aerogels. We have established a new synthesis route, a 3-step sol-gel processing method. The method provides better control of the formation of aerogel structures. The produced silica aerogels show much improved ductility compared to conventional methods in literatures. Furthermore, the synthesized silica aerogels have thermal conductivities as low as about 9 mW/mK, which is the lowest in all reported solids. The ultra low thermal conductivity can be explained with nano-scale structures for the silica aerogels, which have been characterized using advanced techniques including BET and SEM. We have further investigated and demonstrated the ability of enhancing mechanical properties of silica aerogels through structure modification using the proposed 3-step sol-gel processing method. The molecular-level synergism between silica particles/clusters and the doped functional materials inverts the relative host-guest roles in the produced aerogel composite, leading to new stronger and more robust low-density materials.
by Yanjia Zuo.
S.M.

Jäger, Tino [Verfasser]. "Thermoelectric properties of TiNiSn and Zr 0.5 Hf 0.5 NiSn thin films and superlattices with reduced thermal conductivities / Tino Jäger." Mainz : Universitätsbibliothek Mainz, 2014. http://d-nb.info/1046354167/34.

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Gelaye, Ababu A. "UPSCALING OF A THERMAL EVOLUTION EXPERIMENT ON SHREDDED-TIRE MONOFILLS." University of Akron / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=akron1512762530668535.

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Kasali, Suraju Olawale. "Thermal diodes based on phase-change materials." Thesis, Poitiers, 2021. http://www.theses.fr/2021POIT2254.

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Nous étudions dans cette thèse la rectification thermique de diodes thermiques radiatives ou conductive constituées de matériaux à changement de phase.Cette thèse est divisée en trois parties. Dans les premières parties, nous modélisons comparativement les performances d’une diode thermique conductive sphérique et cylindrique constitués de VO2 présentant un transition de phase et des matériaux n’en présentant pas. Des expressions analytiques aux bornes des diodes sont dérivées. Des flux thermiques, des facteurs de rectifications ainsi que les profils de température à l’intérieur de la diode sont obtenus. Nos résul-tats montrent que les différentes géométries de diodes ont un impact significatif sur les profils de température et les flux thermiques, mais moins un sur les facteurs de rectification. Dans ce travail, nous avons obtenu des facteurs de rectification maximaux allant jusqu’à 20.8% et 20.7%, qui sont supérieurs à celui prédit pour une diode plane constituée de VO2. Nous montrons également que des facteurs de rectification similaires à ceux obtenus avec le VO2 dans les géométries sphériques et cylindriques peuvent être atteints avec des matériaux à changement de phase dont le contraste de conductivité est plus important que dans le cas du VO2. Dans la deuxième partie, nous étudions la rectification de diodes thermiques constituées de deux matériaux à changement de phase. Avec, l’idée de générer un facteur de redressement plus élevé que dans le cas d’une diode thermique conductive ne comprenant qu’un matériau à changement de phase unique. Là encore, le travail a conduit à l’établissement d’expressions explicites pour les profils de température, les flux thermiques et le facteur de rectification. Nous avons obtenu un facteur de rectification optimal de 60% avec une variation de température de 250 K couvrant les transitions métal-isolant des deux matériaux. Dans la troisième partie de notre travail, nous avons modélisé et optimisé la rectification thermique de diodes thermiques planes, cylindriques et sphériques radiatives à base de deux matériaux à changement de phase. Nous savons calculer et analyser les facteurs de rectification de ces trois diodes et obtenu les facteurs de rectification optimaux respectifs pour les trois géométries 82%, 86% et 90.5%. Nos résultats montrent que la géométrie sphérique est la meilleure pour optimiser la rectification des courants thermiques radiatifs. De plus, des facteurs de rectification potentiellement supérieurs à ceux prédits ici peuvent être réalisés en utilisant deux matériaux à changement de phase avec des contrastes d’émissivités plus élevés que ceux proposés ici. Ces résultats analytiques et graphiques fournissent un guide utile pour optimiser les facteurs de rectification des diodes thermiques conductives et radiatifs basées sur des matériaux à changement de phase de géométries différentes
The thermal rectification of conductive and radiative thermal diodes based on phase-change materials, whose thermal conductivities and effective emissivities significant change within a narrow range of temperatures, is theoretically studied and optimized in different geometries. This thesis is divided into three parts. In the first part, we comparatively model the performance of a spherical and cylindrical conductive thermal diodes operating with vanadium dioxide (VO2) and non-phase-change materials, and derive analytical expressions for the heat flows, temperature profiles and optimal rectification factors for both diodes. Our results show that different diode geometries have a significant impact on the temperature profiles and heat flows, but less one on the rectification factors. We obtain maximum rectification factors of up to 20.8% and 20.7%, which are higher than the one predicted for a plane diode based on VO2. In addition, it is shown that higher rectification factors could be generated by using materials whose thermal conductivity contrast is higher than that of VO2. In the second part, on the other hand, we theoretically study the thermal rectification of a conductive thermal diode based on the combined effect of two phase-change materials. Herein, the idea is to generate rectification factors higher than that of a conductive thermal diode operating with a single phase-change material. This is achieved by deriving explicit expressions for the temperature profiles, heat fluxes and rectification factor. We obtain an optimal rectification factor of 60% with a temperature variation of 250 K spanning the metal-insulator transitions of VO2 and polyethylene. This enhancement of the rectification factor leads us to the third part of our work, where we model and optimize the thermal rectification of a plane, cylindrical and spherical radiative thermal diodes based on the utilization of two phase-change materials. We analyze the rectification factors of these three diodes and obtain the following optimal rectification factors of 82%, 86% and 90.5%, respectively. The spherical geometry is thus the best shape to optimize the rectification of radiative heat currents. In addition, potential rectification factors greater than the one predicted here can be realized by utilizing two phase-change materials with higher emissivities contrasts than the one proposed here. Our analytical and graphical results provide a useful guide for optimizing the rectification factors of conductive and radiative thermal diodes based on phase-change materials with different geometries

Bamford, Erik, Gustav Ek, Daniel Hedbom, Johan Nyman, Victor Petterson, Josefin Sjöberg, Ida Styffe, and Olivier Vizuete. "Quartzene – A promising thermal insulator : Studies of thermal conductivity’s dependence of density and compression of Quartzene® in the form of powder." Thesis, Uppsala universitet, Institutionen för teknikvetenskaper, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-228087.

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The purpose of this project was to study Svenska Aerogel AB’s product Quartzene®, and develop its capacity as a thermal insulator. Quartzene® is a silica based mesoporous material developed by Svenska Aerogel AB, with properties similar to aerogels produced by the sol-gel process. In this report, the correlation between pore structure and thermal conductivity in the material has been studied using techniques, such as scanning electron microscopy, focused ion beam, finite element simulations and transient plane source. Its properties are interesting because of the expanding market of insulated vacuum panels; in which Svenska Aerogel AB wish to expand to. It was found that the pore sizes of M21-BU increased after compression, and the pore sizes of M4-0-2 decreased. The pore sizes of M21-BU became so large that the Knudsen effect is no longer of interest, and that could explain the different behaviors in thermal conductivity.

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Частини книг з теми "Thermal conductivities":

Torres-Rincon, Juan M. "Thermal and Electrical Conductivities." In Hadronic Transport Coefficients from Effective Field Theories, 75–89. Cham: Springer International Publishing, 2013. http://dx.doi.org/10.1007/978-3-319-00425-9_5.

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Mills, K. C., B. J. Monaghan, and B. J. Keene. "Thermal Conductivities of Liquid Metals." In Thermal Conductivity 23, 519–29. Boca Raton: CRC Press, 2021. http://dx.doi.org/10.1201/9781003210719-54.

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Moore, J. P., F. J. Weaver, R. S. Graves, and D. L. McElroy. "The Thermal Conductivities of SrCl2 and SrF2 from 85 to 400 K." In Thermal Conductivity 18, 115–24. Boston, MA: Springer US, 1985. http://dx.doi.org/10.1007/978-1-4684-4916-7_12.

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Reiss, H., and B. Ziegenbein. "Temperature-Dependent Extinction Coefficients and Solid Thermal Conductivities of Glass Fiber Insulations." In Thermal Conductivity 18, 413–24. Boston, MA: Springer US, 1985. http://dx.doi.org/10.1007/978-1-4684-4916-7_40.

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Lan, Rui. "Thermal Conductivities of Ge–Sb–Te Alloys." In Thermophysical Properties and Measuring Technique of Ge-Sb-Te Alloys for Phase Change Memory, 45–69. Singapore: Springer Singapore, 2020. http://dx.doi.org/10.1007/978-981-15-2217-8_3.

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Huang, Ji-Ping. "Coupling Theory for Temperature-Independent Thermal Conductivities: Thermal Correlated Self-Fixing." In Theoretical Thermotics, 119–33. Singapore: Springer Singapore, 2020. http://dx.doi.org/10.1007/978-981-15-2301-4_11.

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Sivakumar, R., K. Aoyagi, T. Watanabe, and T. Akiyama. "Thermal Conductivities of β-SiAlONs by Mechanically Activated Combustion Synthesis." In SiAlONs and Non-oxides, 139–40. Stafa: Trans Tech Publications Ltd., 2008. http://dx.doi.org/10.4028/3-908454-00-x.139.

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Hafizovic, S., and O. Paul. "Temperature Dependent Thermal Conductivities of CMOS Layers by Micromachined Thermal van der Pauw Test Structures." In Transducers ’01 Eurosensors XV, 1370–73. Berlin, Heidelberg: Springer Berlin Heidelberg, 2001. http://dx.doi.org/10.1007/978-3-642-59497-7_323.

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Huang, Ji-Ping. "Coupling Theory for Temperature-Dependent Thermal Conductivities: Nonlinearity Modulation and Enhancement." In Theoretical Thermotics, 135–47. Singapore: Springer Singapore, 2020. http://dx.doi.org/10.1007/978-981-15-2301-4_12.

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Srivalli, G., G. Jamuna Rani, and V. Balakrishna Murthy. "Effect of Debond and Randomness on Thermal Conductivities of Hollow Fiber Composites." In Lecture Notes in Mechanical Engineering, 597–605. Singapore: Springer Singapore, 2020. http://dx.doi.org/10.1007/978-981-15-1307-7_68.

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Тези доповідей конференцій з теми "Thermal conductivities":

Wang, Zhefu, and Richard B. Peterson. "Thermal Wave Based Measurement of Liquid Thermal Conductivities." In ASME 2008 Heat Transfer Summer Conference collocated with the Fluids Engineering, Energy Sustainability, and 3rd Energy Nanotechnology Conferences. ASMEDC, 2008. http://dx.doi.org/10.1115/ht2008-56418.

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This work develops an experimental technique capable of determining thermal conductivity of liquids with application to nanofluids. A periodic current passing through a thin stainless steel strip generates a periodic Joule heating source and an infrared detector measures the temperature response at the front surface of the stainless steel strip. An open chamber is machined out of a delrin plate with the stainless steel strip acting as the sealing cover. This resulting closed chamber contains the test liquid. The phase and magnitude of the temperature response were measured using a lock-in amplifier at various frequencies from 22 to 502 Hz. A one-dimensional, two-layered transient heat conduction model was developed to predict the temperature response on the front surface of the stainless steel strip. This temperature response, including phase and magnitude, is a function of the thermal properties of the liquid. The phase information shows high sensitivity to thermal properties of the liquid layer and is employed to match experimental data to find thermal conductivities. The measured thermal conductivities of water and ethylene glycol agree well with data from the literature and support the validity of this measurement technique. An aqueous fluid consisting of gold nanoparticles was tested. Anomalous thermal conductivity enhancement was observed. Our measurement results also show a divergence of thermal transport behavior between nanofluids and pure liquids. This suggests the need to carefully examine the role of measurement techniques in the study of nanofluid heat transfer phenomena.

ILLKOVA, KSENIA, RADEK MUSALEK, and JAN MEDRICKY. "Measured and Predicted Thermal Conductivities for YSZ Layers: Application of Different Models." In Thermal Conductivity 33/Thermal Expansion 21. Lancaster, PA: DEStech Publications, Inc., 2019. http://dx.doi.org/10.12783/tc33-te21/30338.

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Wang, Yingtao, Yuan Gao, Elham Easy, Eui-Hyeok Yang, Baoxing Xu, and Xian Zhang. "Thermal Conductivities and Interfacial Thermal Conductance of 2D WSe2." In 2020 IEEE 15th International Conference on Nano/Micro Engineered and Molecular System (NEMS). IEEE, 2020. http://dx.doi.org/10.1109/nems50311.2020.9265628.

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Shi, Li, Qing Hao, Choongho Yu, Natalio Mingo, Xiangyang Kong, and Zhong Lin Wang. "Thermal Conductivities of Individual Tin Dioxide Nanobelts." In ASME 2004 Heat Transfer/Fluids Engineering Summer Conference. ASMEDC, 2004. http://dx.doi.org/10.1115/ht-fed2004-56469.

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We have measured the thermal conductivities of a 53-nm-thick and a 64-nm-thick tin dioxide (SnO2) nanobelt using a microfabricated device in the temperature range of 80–350 K. The uncertainty of the measurement result was estimated to be 10 percent. The thermal conductivities of the nanobelts were found to be significantly lower than the bulk values, and agree with our calculation results using a full dispersion transmission function approach. Comparison between measurements and calculation suggests that phonon-boundary scattering is the primary effect determining the thermal conductivities.

Hartung, D., F. Gather, and P. J. Klar. "Comparison of different methods for measuring thermal conductivities." In 9TH EUROPEAN CONFERENCE ON THERMOELECTRICS: ECT2011. AIP, 2012. http://dx.doi.org/10.1063/1.4731576.

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Zhang, Min, Jianhua Chen, Zhenhua Che, Jiahua Lu, Zhiyou Zhong, Le Yang, and Huizhong Zhao. "Determination of thermal conductivities of biological tissue protein." In 2010 3rd International Conference on Biomedical Engineering and Informatics (BMEI). IEEE, 2010. http://dx.doi.org/10.1109/bmei.2010.5639616.

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Wang, Zuyuan, and Xiulin Ruan. "Uncertainties of Thermal Conductivities From Equilibrium Molecular Dynamics Simulations." In ASME 2016 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/imece2016-68083.

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The Green-Kubo method in the framework of equilibrium molecular dynamics (EMD) simulations is an effective method that has been widely used to calculate thermal conductivities of materials. The previous studies focused on the thermal conductivity values or the average values from repetitive simulations. Little research has been done to investigate the uncertainties of the thermal conductivities from EMD simulations. In this paper, we use solid argon as the material system to study the factors influencing the uncertainties of the predicted thermal conductivities. We find that the uncertainties decrease with the total simulation time as (ttotal)−α and increase with correlation time as (tcorre)β, where 0.48 < α, β < 0.52. We also find that the uncertainties decrease with increasing temperature, but the simulation domain size has a negligible effect. We propose some guidelines for selecting appropriate simulation parameters (e.g., the correlation time and total simulation time) to achieve a desired level of uncertainty. This work is potentially useful for future studies on calculating the thermal conductivities of materials using EMD simulations.

Zhang, Min, Zhenhua Che, Jiahua Lu, Jianhua Chen, Le Yang, Zhiyou Zhong, and Huizhong Zhao. "Prediction model of thermal conductivities of agricultural products postharvest." In 2010 3rd International Congress on Image and Signal Processing (CISP). IEEE, 2010. http://dx.doi.org/10.1109/cisp.2010.5646672.

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Chena, Yunfei, Deyu Li, Juekuan Yang, Zhonghua Ni, and Jennifer R. Lukes. "Interface Effect on Lattice Thermal Conductivities of Superlattice Nanowires." In ASME 2004 International Mechanical Engineering Congress and Exposition. ASMEDC, 2004. http://dx.doi.org/10.1115/imece2004-59149.

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The nonequilibrium molecular dynamics (NEMD) method has been used to calculate the lattice thermal conductivities of Ar and Kr/Ar nanostructures in order to study the effects of interface scattering, boundary scattering, and elastic strain on lattice thermal conductivity. Results show that interface scattering poses significant resistance to phonon transport in superlattices and superlattice nanowires. The thermal conductivity of the Kr/Ar superlattice nanowire is only about 1/3 of that for pure Ar nanowires with the same cross sectional area and total length due to the additional interfacial thermal resistance. It is found that nanowire boundary scattering provides significant resistance to phonon transport. As the cross sectional area increases, the nanowire boundary scattering decreases, which leads to increased nanowire thermal conductivity. The ratio of the interfacial thermal resistance to the total effective thermal resistance increases from 30% for the superlattice nanowire to 42% for the superlattice film. Period length is another important factor affecting the effective thermal conductivity of the nanostructures. Increasing the period length will lead to increased acoustic mismatch between the adjacent layers, and hence increased interfacial thermal resistance. However, if the total length of the superlattice nanowire is fixed, reducing the period length will lead to decreased effective thermal conductivity due to the increased number of interfaces. Finally, it is found that the interfacial thermal resistance decreases as the reference temperature increases, which might be due to the inelastic interface scattering.

Chen, Yunfei, Deyu Li, Jennifer R. Lukes, and Zhonghua Ni. "Monte Carlo Simulation of Thermal Conductivities of Silicon Nanowires." In ASME 2005 Summer Heat Transfer Conference collocated with the ASME 2005 Pacific Rim Technical Conference and Exhibition on Integration and Packaging of MEMS, NEMS, and Electronic Systems. ASMEDC, 2005. http://dx.doi.org/10.1115/ht2005-72377.

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One-dimensional (1D) materials such as various kinds of nanowires and nanotubes have attracted considerable attention due to their potential applications in electronic and energy conversion devices. The thermal transport phenomena in these nanowires and nanotubes could be significantly different from that in bulk material due to boundary scattering, phonon dispersion relation change, and quantum confinement. It is very important to understand the thermal transport phenomena in these materials so that we can apply them in the thermal design of microelectronic, photonic, and energy conversion devices. While intensive experimental efforts are being carried out to investigate the thermal transport in nanowires and nanotube, an accurate numerical prediction can help the understanding of phonon scattering mechanisms, which is of fundamental theoretical significance. A Monte Carlo simulation was developed and applied to investigate phonon transport in single crystalline Si nanowires. The Phonon-phonon Normal (N) and Umklapp (U) scattering processes were modeled with a genetic algorithm to satisfy both the energy and the momentum conservation. The scattering rates of N and U scattering processes were given from the first perturbation theory. Ballistic phonon transport was modeled with the code and the numerical results fit the theoretical prediction very well. The thermal conductivity of bulk Si was then simulated and good agreement was achieved with the experimental data. Si nanowire thermal conductivity was then studied and compared with some recent experimental results. In order to study the confinement effects on phonon transport in nanowires, two different phonon dispersions, one based on bulk Si and the other solved from the elastic wave theory for nanowires, were adopted in the simulation. The discrepancy from the simulations based on different phonon dispersions increases as the nanowire diameter decreases, which suggests that the confinement effect is significant when the nanowire diameter goes down to tens nanometer range. It was found that the U scattering probability engaged in Si nanowires was increased from that in bulk Si due to the decrease of the frequency gap between different modes and the reduced phonon group velocity. Simulation results suggest that the dispersion relation for nanowire solved from the elasticity theory should be used to evaluate nanowire thermal conductivity as the nanowire diameter reduced to tens nanometer.

Звіти організацій з теми "Thermal conductivities":

Henager, C. H. Jr, and W. T. Pawlewicz. Thermal conductivities of thin, sputtered optical films. Office of Scientific and Technical Information (OSTI), May 1991. http://dx.doi.org/10.2172/10108496.

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Henager, C. H. Jr, and W. T. Pawlewicz. Thermal conductivities of thin, sputtered optical films. Office of Scientific and Technical Information (OSTI), May 1991. http://dx.doi.org/10.2172/6109768.

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Van Woerkom, Linn, and Richard Freeman. The Measurement of Electrical and Thermal Conductivities in Warm Dense Matter. Office of Scientific and Technical Information (OSTI), May 2019. http://dx.doi.org/10.2172/1514487.

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Mrochek, J. E., J. H. Wilson, and J. K. Johnson. Thermal conductivities of Wilsonville solvent and Wilsonville solvent/Illinois No. 6 coal slurry. Office of Scientific and Technical Information (OSTI), December 1985. http://dx.doi.org/10.2172/6200832.

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Han, L. S., and L. Glower. Directional Thermal Conductivities of Graphite/Epoxy Composites: 0/90 and 0/ + or - 45/90. Fort Belvoir, VA: Defense Technical Information Center, January 1985. http://dx.doi.org/10.21236/ada152209.

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Sanchez, L. C., and M. L. Hudson. Determination of effective thermal conductivities for a full-scale mock-up of a 217-element breeder reactor fuel assembly subjected to normal shipping conditions. Office of Scientific and Technical Information (OSTI), December 1986. http://dx.doi.org/10.2172/7039593.

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Yarbrough, D. W., R. K. Williams, and D. R. Shockley. Thermal conductivities, electrical resistivities, and Seebeck coefficients of YBa{sub 2}Cu{sub 3}O{sub 7{minus}x} superconductors from 80 to 300 K. Office of Scientific and Technical Information (OSTI), December 1993. http://dx.doi.org/10.2172/10111984.

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Friedman, Shmuel, Jon Wraith, and Dani Or. Geometrical Considerations and Interfacial Processes Affecting Electromagnetic Measurement of Soil Water Content by TDR and Remote Sensing Methods. United States Department of Agriculture, 2002. http://dx.doi.org/10.32747/2002.7580679.bard.

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Time Domain Reflectometry (TDR) and other in-situ and remote sensing dielectric methods for determining the soil water content had become standard in both research and practice in the last two decades. Limitations of existing dielectric methods in some soils, and introduction of new agricultural measurement devices or approaches based on soil dielectric properties mandate improved understanding of the relationship between the measured effective permittivity (dielectric constant) and the soil water content. Mounting evidence indicates that consideration must be given not only to the volume fractions of soil constituents, as most mixing models assume, but also to soil attributes and ambient temperature in order to reduce errors in interpreting measured effective permittivities. The major objective of the present research project was to investigate the effects of the soil geometrical attributes and interfacial processes (bound water) on the effective permittivity of the soil, and to develop a theoretical frame for improved, soil-specific effective permittivity- water content calibration curves, which are based on easily attainable soil properties. After initializing the experimental investigation of the effective permittivity - water content relationship, we realized that the first step for water content determination by the Time Domain Reflectometry (TDR) method, namely, the TDR measurement of the soil effective permittivity still requires standardization and improvement, and we also made more efforts than originally planned towards this objective. The findings of the BARD project, related to these two consequential steps involved in TDR measurement of the soil water content, are expected to improve the accuracy of soil water content determination by existing in-situ and remote sensing dielectric methods and to help evaluate new water content sensors based on soil electrical properties. A more precise water content determination is expected to result in reduced irrigation levels, a matter which is beneficial first to American and Israeli farmers, and also to hydrologists and environmentalists dealing with production and assessment of contamination hazards of this progressively more precious natural resource. The improved understanding of the way the soil geometrical attributes affect its effective permittivity is expected to contribute to our understanding and predicting capability of other, related soil transport properties such as electrical and thermal conductivity, and diffusion coefficients of solutes and gas molecules. In addition, to the originally planned research activities we also investigated other related problems and made many contributions of short and longer terms benefits. These efforts include: Developing a method and a special TDR probe for using TDR systems to determine also the soil's matric potential; Developing a methodology for utilizing the thermodielectric effect, namely, the variation of the soil's effective permittivity with temperature, to evaluate its specific surface area; Developing a simple method for characterizing particle shape by measuring the repose angle of a granular material avalanching in water; Measurements and characterization of the pore scale, saturation degree - dependent anisotropy factor for electrical and hydraulic conductivities; Studying the dielectric properties of cereal grains towards improved determination of their water content. A reliable evaluation of the soil textural attributes (e.g. the specific surface area mentioned above) and its water content is essential for intensive irrigation and fertilization processes and within extensive precision agriculture management. The findings of the present research project are expected to improve the determination of cereal grain water content by on-line dielectric methods. A precise evaluation of grain water content is essential for pricing and evaluation of drying-before-storage requirements, issues involving energy savings and commercial aspects of major economic importance to the American agriculture. The results and methodologies developed within the above mentioned side studies are expected to be beneficial to also other industrial and environmental practices requiring the water content determination and characterization of granular materials.