Documents disponibles écrits par cet auteur

Direct simulation of thermal transport through sintered wick microstructures / Karthik K. Bodla in Journal of heat transfer, Vol. 134 N° 1 (Janvier 2012) 

Public ISBD [article]  in Journal of heat transfer > Vol. 134 N° 1 (Janvier 2012) . - 10 p. Titre : Direct simulation of thermal transport through sintered wick microstructures Type de document : texte imprimé Auteurs : Karthik K. Bodla, Auteur ; Jayathi Y. Murthy, Auteur ; Suresh V. Garimella, Auteur Année de publication : 2012 Article en page(s) : 10 p. Note générale : Heat transfer Langues : Anglais (eng) Mots-clés : Computational  fluid  dynamics  Computerised  tomography  Copper  Flow  simulation  Flow  through  porous  media  Fluidised  beds  Heat  pipes  Heat  transfer  Image  reconstruction  Mesh  generation  Microfluidics  Permeability  Pipe  flow  Porosity  Statistical  analysis  Thermal  conductivity Index. décimale : 536 Chaleur. Thermodynamique Résumé : Porous sintered microstructures are critical to the functioning of passive heat transport devices such as heat pipes. The topology and microstructure of the porous wick play a crucial role in determining the thermal performance of such devices. Three sintered copper wick samples employed in commercial heat pipes are characterized in this work in terms of their thermal transport properties––porosity, effective thermal conductivity, permeability, and interfacial heat transfer coefficient. The commercially available samples of nearly identical porosities (~61% open volume) are CT scanned at 5.5 µm resolution, and the resulting image stack is reconstructed to produce high-quality finite volume meshes representing the solid and interstitial pore regions, with a conformal mesh at the interface separating these two regions. The resulting mesh is then employed for numerical analysis of thermal transport through fluid-saturated porous sintered beds. Multiple realizations are employed for statistically averaging out the randomness exhibited by the samples under consideration. The effective thermal conductivity and permeability data are compared with analytical models developed for spherical particle beds. The dependence of effective thermal conductivity of sintered samples on the extent of sintering is quantified. The interfacial heat transfer coefficient is compared against a correlation from the literature based on experimental data obtained with spherical particle beds. A modified correlation is proposed to match the results obtained. DEWEY : 536 ISSN : 0022-1481 En ligne : http://www.asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO00013400 [...] [article] Direct simulation of thermal transport through sintered wick microstructures [texte imprimé] / Karthik K. Bodla, Auteur ; Jayathi Y. Murthy, Auteur ; Suresh V. Garimella, Auteur . - 2012 . - 10 p. Heat transfer Langues : Anglais (eng) in Journal of heat transfer > Vol. 134 N° 1 (Janvier 2012) . - 10 p. Mots-clés : Computational  fluid  dynamics  Computerised  tomography  Copper  Flow  simulation  Flow  through  porous  media  Fluidised  beds  Heat  pipes  Heat  transfer  Image  reconstruction  Mesh  generation  Microfluidics  Permeability  Pipe  flow  Porosity  Statistical  analysis  Thermal  conductivity Index. décimale : 536 Chaleur. Thermodynamique Résumé : Porous sintered microstructures are critical to the functioning of passive heat transport devices such as heat pipes. The topology and microstructure of the porous wick play a crucial role in determining the thermal performance of such devices. Three sintered copper wick samples employed in commercial heat pipes are characterized in this work in terms of their thermal transport properties––porosity, effective thermal conductivity, permeability, and interfacial heat transfer coefficient. The commercially available samples of nearly identical porosities (~61% open volume) are CT scanned at 5.5 µm resolution, and the resulting image stack is reconstructed to produce high-quality finite volume meshes representing the solid and interstitial pore regions, with a conformal mesh at the interface separating these two regions. The resulting mesh is then employed for numerical analysis of thermal transport through fluid-saturated porous sintered beds. Multiple realizations are employed for statistically averaging out the randomness exhibited by the samples under consideration. The effective thermal conductivity and permeability data are compared with analytical models developed for spherical particle beds. The dependence of effective thermal conductivity of sintered samples on the extent of sintering is quantified. The interfacial heat transfer coefficient is compared against a correlation from the literature based on experimental data obtained with spherical particle beds. A modified correlation is proposed to match the results obtained. DEWEY : 536 ISSN : 0022-1481 En ligne : http://www.asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO00013400 [...]

A meshless finite difference method for conjugate heat conduction problems / Chandrashekhar Varanasi in Journal of heat transfer, Vol. 132 N° 8 (Août 2010) 

Public ISBD [article]  in Journal of heat transfer > Vol. 132 N° 8 (Août 2010) . - pp. [081303-1/13] Titre : A meshless finite difference method for conjugate heat conduction problems Type de document : texte imprimé Auteurs : Chandrashekhar Varanasi, Auteur ; Jayathi Y. Murthy, Auteur ; Sanjay Mathur, Auteur Article en page(s) : pp. [081303-1/13] Note générale : Physique Langues : Anglais (eng) Mots-clés : Finite  point  method  Weighted  least-squares  Conjugate  heat  conduction Index. décimale : 536 Chaleur. Thermodynamique Résumé : A meshless finite difference method is developed for solving conjugate heat transfer problems. Starting with an arbitrary distribution of mesh points, derivatives are evaluated using a weighted least-squares procedure. The resulting system of algebraic equations is sparse and is solved using an algebraic multigrid method. The implementation of the Neumann, Dirichlet, and mixed boundary conditions within this framework is described. For conjugate heat transfer problems, continuity of the heat flux and temperature are imposed on mesh points at multimaterial interfaces. The method is verified through application to classical heat conduction problems with known analytical solutions. It is then applied to the solution of conjugate heat transfer problems in complex geometries, and the solutions so obtained are compared with more conventional unstructured finite volume methods. The method improves on existing meshless methods for conjugate heat conduction by eliminating spurious oscillations previously observed. Metrics for accuracy are provided and future extensions are discussed. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&ONLINE=YES&smode= [...] [article] A meshless finite difference method for conjugate heat conduction problems [texte imprimé] / Chandrashekhar Varanasi, Auteur ; Jayathi Y. Murthy, Auteur ; Sanjay Mathur, Auteur . - pp. [081303-1/13]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 132 N° 8 (Août 2010) . - pp. [081303-1/13] Mots-clés : Finite  point  method  Weighted  least-squares  Conjugate  heat  conduction Index. décimale : 536 Chaleur. Thermodynamique Résumé : A meshless finite difference method is developed for solving conjugate heat transfer problems. Starting with an arbitrary distribution of mesh points, derivatives are evaluated using a weighted least-squares procedure. The resulting system of algebraic equations is sparse and is solved using an algebraic multigrid method. The implementation of the Neumann, Dirichlet, and mixed boundary conditions within this framework is described. For conjugate heat transfer problems, continuity of the heat flux and temperature are imposed on mesh points at multimaterial interfaces. The method is verified through application to classical heat conduction problems with known analytical solutions. It is then applied to the solution of conjugate heat transfer problems in complex geometries, and the solutions so obtained are compared with more conventional unstructured finite volume methods. The method improves on existing meshless methods for conjugate heat conduction by eliminating spurious oscillations previously observed. Metrics for accuracy are provided and future extensions are discussed. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&ONLINE=YES&smode= [...]

Modeling of polarization-specific phonon transmission through interfaces / Zhen Huang in Journal of heat transfer, Vol. 133 N° 11 (Novembre 2011) 

Public ISBD [article]  in Journal of heat transfer > Vol. 133 N° 11 (Novembre 2011) . - pp. [114502/1-3] Titre : Modeling of polarization-specific phonon transmission through interfaces Type de document : texte imprimé Auteurs : Zhen Huang, Auteur ; Jayathi Y. Murthy, Auteur ; Timothy S. Fisher, Auteur Année de publication : 2012 Article en page(s) : pp. [114502/1-3] Note générale : Physique Langues : Anglais (eng) Mots-clés : Phonon  Green's  function  Polarization-specific  Transmission  function Index. décimale : 536 Chaleur. Thermodynamique Résumé : In this work, the atomistic Green's function method is extended to compute transmission functions for each phonon polarization. The eigenvectors and eigenvalues of the overall density of states matrices are manipulated to yield a density of states matrix for each polarization. A decomposed self-energy is calculated from the density of states matrix for each polarization and used to calculate the transmission function for a particular phonon branch. In a pure bulk material such as silicon, each transmission function exhibits a frequency-independent value of unity. In heterogeneous bulk materials, the transmission function is reduced significantly due to the junction of dissimilar materials. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000133000011 [...] [article] Modeling of polarization-specific phonon transmission through interfaces [texte imprimé] / Zhen Huang, Auteur ; Jayathi Y. Murthy, Auteur ; Timothy S. Fisher, Auteur . - 2012 . - pp. [114502/1-3]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 11 (Novembre 2011) . - pp. [114502/1-3] Mots-clés : Phonon  Green's  function  Polarization-specific  Transmission  function Index. décimale : 536 Chaleur. Thermodynamique Résumé : In this work, the atomistic Green's function method is extended to compute transmission functions for each phonon polarization. The eigenvectors and eigenvalues of the overall density of states matrices are manipulated to yield a density of states matrix for each polarization. A decomposed self-energy is calculated from the density of states matrix for each polarization and used to calculate the transmission function for a particular phonon branch. In a pure bulk material such as silicon, each transmission function exhibits a frequency-independent value of unity. In heterogeneous bulk materials, the transmission function is reduced significantly due to the junction of dissimilar materials. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000133000011 [...]

Molecular dynamics simulation of phonon scattering at silicon/germanium interfaces / Lin Sun in Journal of heat transfer, Vol. 132 N° 10 (Octobre 2010) 

Public ISBD [article]  in Journal of heat transfer > Vol. 132 N° 10 (Octobre 2010) . - pp. [102403/1-9] Titre : Molecular dynamics simulation of phonon scattering at silicon/germanium interfaces Type de document : texte imprimé Auteurs : Lin Sun, Auteur ; Jayathi Y. Murthy, Auteur Année de publication : 2010 Article en page(s) : pp. [102403/1-9] Note générale : Physique Langues : Anglais (eng) Mots-clés : Molecular  dynamics  Phonon  transport  Interface  Wave  packet Index. décimale : 536 Chaleur. Thermodynamique Résumé : Detailed phonon transport at Si/Ge interfaces is studied using the molecular dynamics wave-packet method. Three types of interfaces are investigated: A smooth interface, an interface with random roughness, and an interface with a regularly patterned roughness. The phonon transmissivity for each case is calculated as a function of phonon frequency, roughness characteristic length, and atomic structure. For a smooth interface, the transmissivities predicted by the MD simulations agree well with the acoustic mismatch model based on the continuum assumption. The rough interface simulation results indicate that random roughness is the source of incoherent phonon scattering and decreases the phonon transmission. Periodic structures such as the regularly patterned roughness employed in this paper cause strong phonon wave interference and may restore phonon transmission as the layer thickness increases. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&ONLINE=YES&smode= [...] [article] Molecular dynamics simulation of phonon scattering at silicon/germanium interfaces [texte imprimé] / Lin Sun, Auteur ; Jayathi Y. Murthy, Auteur . - 2010 . - pp. [102403/1-9]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 132 N° 10 (Octobre 2010) . - pp. [102403/1-9] Mots-clés : Molecular  dynamics  Phonon  transport  Interface  Wave  packet Index. décimale : 536 Chaleur. Thermodynamique Résumé : Detailed phonon transport at Si/Ge interfaces is studied using the molecular dynamics wave-packet method. Three types of interfaces are investigated: A smooth interface, an interface with random roughness, and an interface with a regularly patterned roughness. The phonon transmissivity for each case is calculated as a function of phonon frequency, roughness characteristic length, and atomic structure. For a smooth interface, the transmissivities predicted by the MD simulations agree well with the acoustic mismatch model based on the continuum assumption. The rough interface simulation results indicate that random roughness is the source of incoherent phonon scattering and decreases the phonon transmission. Periodic structures such as the regularly patterned roughness employed in this paper cause strong phonon wave interference and may restore phonon transmission as the layer thickness increases. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&ONLINE=YES&smode= [...]

Phonon transport across mesoscopic constrictions / Dhruv Singh in Journal of heat transfer, Vol. 133 N° 4 (Avril 2011) 

Public ISBD [article]  in Journal of heat transfer > Vol. 133 N° 4 (Avril 2011) . - pp. [042402/1-8] Titre : Phonon transport across mesoscopic constrictions Type de document : texte imprimé Auteurs : Dhruv Singh, Auteur ; Jayathi Y. Murthy, Auteur ; Timothy S. Fisher, Auteur Année de publication : 2011 Article en page(s) : pp. [042402/1-8] Note générale : Physique Langues : Anglais (eng) Mots-clés : Boltzman  transport  equation  Constriction  resistance  Ballistic-diffusive  transition  Gas  gap  conductance  Slip  flow  and  heat  transfer  Knudsen  number  Temperature  jump Index. décimale : 536 Chaleur. Thermodynamique Résumé : Phonon transport across constrictions formed by a nanowire or a nanoparticle on a substrate is studied by a numerical solution of the gray Boltzmann transport equation (BTE) resolving the effects of two length scales that govern problems of practical importance. Predictions of total thermal resistance for wire/substrate and particle/substrate combinations are made for the entire range of Knudsen number, with an emphasis on resolving transport in the mesoscopic regime where ballistic-diffusive mechanisms operate and analytical expressions are not available. The relative magnitudes of bulk and constriction resistance are established, and a correlation for overall thermal resistance spanning the range of practical Knudsen numbers is provided. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...] [article] Phonon transport across mesoscopic constrictions [texte imprimé] / Dhruv Singh, Auteur ; Jayathi Y. Murthy, Auteur ; Timothy S. Fisher, Auteur . - 2011 . - pp. [042402/1-8]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 4 (Avril 2011) . - pp. [042402/1-8] Mots-clés : Boltzman  transport  equation  Constriction  resistance  Ballistic-diffusive  transition  Gas  gap  conductance  Slip  flow  and  heat  transfer  Knudsen  number  Temperature  jump Index. décimale : 536 Chaleur. Thermodynamique Résumé : Phonon transport across constrictions formed by a nanowire or a nanoparticle on a substrate is studied by a numerical solution of the gray Boltzmann transport equation (BTE) resolving the effects of two length scales that govern problems of practical importance. Predictions of total thermal resistance for wire/substrate and particle/substrate combinations are made for the entire range of Knudsen number, with an emphasis on resolving transport in the mesoscopic regime where ballistic-diffusive mechanisms operate and analytical expressions are not available. The relative magnitudes of bulk and constriction resistance are established, and a correlation for overall thermal resistance spanning the range of practical Knudsen numbers is provided. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...]

Phonon transport modeling using Boltzmann transport equation with anisotropic relaxation times / Chunjian Ni in Journal of heat transfer, Vol. 134 N° 8 (special issue) (Août 2012) 

Permalink