Dépouillements

Review of heat conduction in nanofluids / Jing Fan 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. [040801/1-14] Titre : Review of heat conduction in nanofluids Type de document : texte imprimé Auteurs : Jing Fan, Auteur ; Liqiu Wang, Auteur Année de publication : 2011 Article en page(s) : pp. [040801/1-14] Note générale : Physique Langues : Anglais (eng) Mots-clés : Nanofluids  Heat  conduction  Experiments  Models  Dual-lagging  Thermal  wave Index. décimale : 536 Chaleur. Thermodynamique Résumé : Nanofluids—fluid suspensions of nanometer-sized particles—are a very important area of emerging technology and are playing an increasingly important role in the continuing advances of nanotechnology and biotechnology worldwide. They have enormously exciting potential applications and may revolutionize the field of heat transfer. This review is on the advances in our understanding of heat-conduction process in nanofluids. The emphasis centers on the thermal conductivity of nanofluids: its experimental data, proposed mechanisms responsible for its enhancement, and its predicting models. A relatively intensified effort has been made on determining thermal conductivity of nanofluids from experiments. While the detailed microstructure-conductivity relationship is still unknown, the data from these experiments have enabled some trends to be identified. Suggested microscopic reasons for the experimental finding of significant conductivity enhancement include the nanoparticle Brownian motion, the Brownian-motion-induced convection, the liquid layering at the liquid-particle interface, and the nanoparticle cluster/aggregate. Although there is a lack of agreement regarding the role of the first three effects, the last effect is generally accepted to be responsible for the reported conductivity enhancement. The available models of predicting conductivity of nanofluids all involve some empirical parameters that negate their predicting ability and application. The recently developed first-principles theory of thermal waves offers not only a macroscopic reason for experimental observations but also a model governing the microstructure-conductivity relationship without involving any empirical parameter. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...] [article] Review of heat conduction in nanofluids [texte imprimé] / Jing Fan, Auteur ; Liqiu Wang, Auteur . - 2011 . - pp. [040801/1-14]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 4 (Avril 2011) . - pp. [040801/1-14] Mots-clés : Nanofluids  Heat  conduction  Experiments  Models  Dual-lagging  Thermal  wave Index. décimale : 536 Chaleur. Thermodynamique Résumé : Nanofluids—fluid suspensions of nanometer-sized particles—are a very important area of emerging technology and are playing an increasingly important role in the continuing advances of nanotechnology and biotechnology worldwide. They have enormously exciting potential applications and may revolutionize the field of heat transfer. This review is on the advances in our understanding of heat-conduction process in nanofluids. The emphasis centers on the thermal conductivity of nanofluids: its experimental data, proposed mechanisms responsible for its enhancement, and its predicting models. A relatively intensified effort has been made on determining thermal conductivity of nanofluids from experiments. While the detailed microstructure-conductivity relationship is still unknown, the data from these experiments have enabled some trends to be identified. Suggested microscopic reasons for the experimental finding of significant conductivity enhancement include the nanoparticle Brownian motion, the Brownian-motion-induced convection, the liquid layering at the liquid-particle interface, and the nanoparticle cluster/aggregate. Although there is a lack of agreement regarding the role of the first three effects, the last effect is generally accepted to be responsible for the reported conductivity enhancement. The available models of predicting conductivity of nanofluids all involve some empirical parameters that negate their predicting ability and application. The recently developed first-principles theory of thermal waves offers not only a macroscopic reason for experimental observations but also a model governing the microstructure-conductivity relationship without involving any empirical parameter. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...]

Thermodynamic basis of dual-phase-lagging heat conduction / Mingtian Xu 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. [041401/1-7] Titre : Thermodynamic basis of dual-phase-lagging heat conduction Type de document : texte imprimé Auteurs : Mingtian Xu, Auteur Année de publication : 2011 Article en page(s) : pp. [041401/1-7] Note générale : Physique Langues : Anglais (eng) Mots-clés : Dual-phase-lagging  heat  conduction  Extended  irreversible  thermodynamics  Second  law  of  thermodynamics  Maxwell  model Index. décimale : 536 Chaleur. Thermodynamique Résumé : The thermal vibration phenomenon occurring in the dual-phase-lagging heat conduction violates the second law of thermodynamics under the local equilibrium assumption. In order to resolve this paradox, two types of the extended irreversible thermodynamics are developed in the present work, which make the dual-phase-lagging heat conduction model compatible with the second law of thermodynamics. It is also shown that these extended irreversible thermodynamics can give rise to the Maxwell model for the viscoelastic fluid flow. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...] [article] Thermodynamic basis of dual-phase-lagging heat conduction [texte imprimé] / Mingtian Xu, Auteur . - 2011 . - pp. [041401/1-7]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 4 (Avril 2011) . - pp. [041401/1-7] Mots-clés : Dual-phase-lagging  heat  conduction  Extended  irreversible  thermodynamics  Second  law  of  thermodynamics  Maxwell  model Index. décimale : 536 Chaleur. Thermodynamique Résumé : The thermal vibration phenomenon occurring in the dual-phase-lagging heat conduction violates the second law of thermodynamics under the local equilibrium assumption. In order to resolve this paradox, two types of the extended irreversible thermodynamics are developed in the present work, which make the dual-phase-lagging heat conduction model compatible with the second law of thermodynamics. It is also shown that these extended irreversible thermodynamics can give rise to the Maxwell model for the viscoelastic fluid flow. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...]

Correlation of subatmospheric pressure, saturated, pool boiling of water on a structured-porous surface / Sean J. Penley 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. [041501/1-11] Titre : Correlation of subatmospheric pressure, saturated, pool boiling of water on a structured-porous surface Type de document : texte imprimé Auteurs : Sean J. Penley, Auteur ; R. A. Wirtz, Auteur Année de publication : 2011 Article en page(s) : pp. [041501/1-11] Note générale : Physique Langues : Anglais (eng) Mots-clés : Boilling  Enhanced  surface  Subatmospheric  pressure  Correlation  Water  nucleation  Structured-porous  surface  Screen  laminate  Thermal  management  Electronic  cooling Index. décimale : 536 Chaleur. Thermodynamique Résumé : Saturated pool-boiling experiments at 1 atm and subatmospheric pressure assess the utility of fine-filament screen-laminate enhanced surfaces as effective bubble nucleation sites. Experiments were conducted on vertically oriented, multilayer laminates in saturated distilled water at pressures of 0.2–1.0 atm. The performance of 12 different copper-filament surfaces, having pore hydraulic diameters ranging from 14 µm to 172 µm, is documented. Experimental results show that boiling performance is a strong function of screen-laminate geometry. In the present work, enhancement of up to 27 times that of an unenhanced surface was obtained at a superheat of 8 K and a pressure of 0.2 atm. Dimensional analysis and multiparameter regression are used to develop a heat transfer correlation that relates the boiling heat transfer coefficient to the lamination geometry. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...] [article] Correlation of subatmospheric pressure, saturated, pool boiling of water on a structured-porous surface [texte imprimé] / Sean J. Penley, Auteur ; R. A. Wirtz, Auteur . - 2011 . - pp. [041501/1-11]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 4 (Avril 2011) . - pp. [041501/1-11] Mots-clés : Boilling  Enhanced  surface  Subatmospheric  pressure  Correlation  Water  nucleation  Structured-porous  surface  Screen  laminate  Thermal  management  Electronic  cooling Index. décimale : 536 Chaleur. Thermodynamique Résumé : Saturated pool-boiling experiments at 1 atm and subatmospheric pressure assess the utility of fine-filament screen-laminate enhanced surfaces as effective bubble nucleation sites. Experiments were conducted on vertically oriented, multilayer laminates in saturated distilled water at pressures of 0.2–1.0 atm. The performance of 12 different copper-filament surfaces, having pore hydraulic diameters ranging from 14 µm to 172 µm, is documented. Experimental results show that boiling performance is a strong function of screen-laminate geometry. In the present work, enhancement of up to 27 times that of an unenhanced surface was obtained at a superheat of 8 K and a pressure of 0.2 atm. Dimensional analysis and multiparameter regression are used to develop a heat transfer correlation that relates the boiling heat transfer coefficient to the lamination geometry. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...]

Numerical simulation of dynamics and heat transfer associated with a single bubble in subcooled boiling and in the presence of noncondensables / Jinfeng Wu 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. [041502/1-14] Titre : Numerical simulation of dynamics and heat transfer associated with a single bubble in subcooled boiling and in the presence of noncondensables Type de document : texte imprimé Auteurs : Jinfeng Wu, Auteur ; Vijay K. Dhir, Auteur Année de publication : 2011 Article en page(s) : pp. [041502/1-14] Note générale : Physique Langues : Anglais (eng) Mots-clés : Subcooled  nucleate  boiling  Level-set  method  Moving  mesh  method  Numerical  simulation  Condensation  Noncondensable Index. décimale : 536 Chaleur. Thermodynamique Résumé : During phase change at the bubble-liquid interface, under subcooled boiling conditions, noncondensable gases dissolved in the liquid will be injected into the bubble along with vapor. Due to heat transfer into subcooled liquid, vapor will condense in the upper regions of the bubble while noncondensables will continue to accumulate. Subsequently, thermocapillary convection caused by nonuniform saturation temperature at the interface may occur. The aim of this work is to investigate the effects of noncondensables on heat transfer and bubble dynamics. The numerical results show that the effects of noncondensables on 5°C subcooled boiling of water are minor in terms of the equilibrium bubble diameter and overall Nusselt number. However, induced flow pattern around the bubble is altered, especially under reduced gravity conditions. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...] [article] Numerical simulation of dynamics and heat transfer associated with a single bubble in subcooled boiling and in the presence of noncondensables [texte imprimé] / Jinfeng Wu, Auteur ; Vijay K. Dhir, Auteur . - 2011 . - pp. [041502/1-14]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 4 (Avril 2011) . - pp. [041502/1-14] Mots-clés : Subcooled  nucleate  boiling  Level-set  method  Moving  mesh  method  Numerical  simulation  Condensation  Noncondensable Index. décimale : 536 Chaleur. Thermodynamique Résumé : During phase change at the bubble-liquid interface, under subcooled boiling conditions, noncondensable gases dissolved in the liquid will be injected into the bubble along with vapor. Due to heat transfer into subcooled liquid, vapor will condense in the upper regions of the bubble while noncondensables will continue to accumulate. Subsequently, thermocapillary convection caused by nonuniform saturation temperature at the interface may occur. The aim of this work is to investigate the effects of noncondensables on heat transfer and bubble dynamics. The numerical results show that the effects of noncondensables on 5°C subcooled boiling of water are minor in terms of the equilibrium bubble diameter and overall Nusselt number. However, induced flow pattern around the bubble is altered, especially under reduced gravity conditions. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...]

Scaling of natural convection of an inclined flat plate / Suvash C. Saha 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. [041503/1-9] Titre : Scaling of natural convection of an inclined flat plate : sudden cooling condition Type de document : texte imprimé Auteurs : Suvash C. Saha, Auteur ; John C. Patterson, Auteur ; Chengwang Lei, Auteur Année de publication : 2011 Article en page(s) : pp. [041503/1-9] Note générale : Physique Langues : Anglais (eng) Mots-clés : Natural  convection  Sudden  cooling  Boundary  layer  Unsteady  flow  Instability Index. décimale : 536 Chaleur. Thermodynamique Résumé : The natural convection boundary layer adjacent to an inclined plate subject to sudden cooling boundary condition has been studied. It is found that the cold boundary layer adjacent to the plate is potentially unstable to Rayleigh–Bénard instability if the Rayleigh number exceeds a certain critical value. A scaling relation for the onset of instability of the boundary layer is achieved. The scaling relations have been developed by equating important terms of the governing equations based on the development of the boundary layer with time. The flow adjacent to the plate can be classified broadly into a conductive, a stable convective, or an unstable convective regime determined by the Rayleigh number. Proper scales have been established to quantify the flow properties in each of these flow regimes. An appropriate identification of the time when the instability may set in is discussed. A numerical verification of the time for the onset of instability is also presented in this study. Different flow regimes based on the stability of the boundary layer have been discussed with numerical results. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...] [article] Scaling of natural convection of an inclined flat plate : sudden cooling condition [texte imprimé] / Suvash C. Saha, Auteur ; John C. Patterson, Auteur ; Chengwang Lei, Auteur . - 2011 . - pp. [041503/1-9]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 4 (Avril 2011) . - pp. [041503/1-9] Mots-clés : Natural  convection  Sudden  cooling  Boundary  layer  Unsteady  flow  Instability Index. décimale : 536 Chaleur. Thermodynamique Résumé : The natural convection boundary layer adjacent to an inclined plate subject to sudden cooling boundary condition has been studied. It is found that the cold boundary layer adjacent to the plate is potentially unstable to Rayleigh–Bénard instability if the Rayleigh number exceeds a certain critical value. A scaling relation for the onset of instability of the boundary layer is achieved. The scaling relations have been developed by equating important terms of the governing equations based on the development of the boundary layer with time. The flow adjacent to the plate can be classified broadly into a conductive, a stable convective, or an unstable convective regime determined by the Rayleigh number. Proper scales have been established to quantify the flow properties in each of these flow regimes. An appropriate identification of the time when the instability may set in is discussed. A numerical verification of the time for the onset of instability is also presented in this study. Different flow regimes based on the stability of the boundary layer have been discussed with numerical results. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...]

A new technique to determine convection coefficients with flow through particle beds / Xiaodong Nie 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. [041601/1-8] Titre : A new technique to determine convection coefficients with flow through particle beds Type de document : texte imprimé Auteurs : Xiaodong Nie, Auteur ; Richard Evitts, Auteur ; Robert Besant, Auteur Année de publication : 2011 Article en page(s) : pp. [041601/1-8] Note générale : Physique Langues : Anglais (eng) Mots-clés : Convection  Heat  transfer  coefficient  Correlation  Transient  Energy  storage  Spherical  particle  bed  Uncertainty  analysis Index. décimale : 536 Chaleur. Thermodynamique Résumé : A new method for determining the heat transfer coefficient for air flowing steadily through beds of particles is presented. In this technique, a step change in the inlet air temperature is applied to a small test bed and temperature distributions in the bed and at the air outlet are sampled over a short time period. The convective heat transfer coefficient is determined using data from the convective heat transfer process in the bed where the analysis includes the partial differential equation that describes the transient energy storage in the particles within the bed. The analysis is performed for a short time duration when the temperature distribution in the particle bed is almost linear along the axis of the bed. This time period permits the most accurate determination of the heat transfer coefficient using the data. Using beds of spherical particles a new correlation is developed for the Nusselt number versus the Reynolds number (5 DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...] [article] A new technique to determine convection coefficients with flow through particle beds [texte imprimé] / Xiaodong Nie, Auteur ; Richard Evitts, Auteur ; Robert Besant, Auteur . - 2011 . - pp. [041601/1-8]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 4 (Avril 2011) . - pp. [041601/1-8] Mots-clés : Convection  Heat  transfer  coefficient  Correlation  Transient  Energy  storage  Spherical  particle  bed  Uncertainty  analysis Index. décimale : 536 Chaleur. Thermodynamique Résumé : A new method for determining the heat transfer coefficient for air flowing steadily through beds of particles is presented. In this technique, a step change in the inlet air temperature is applied to a small test bed and temperature distributions in the bed and at the air outlet are sampled over a short time period. The convective heat transfer coefficient is determined using data from the convective heat transfer process in the bed where the analysis includes the partial differential equation that describes the transient energy storage in the particles within the bed. The analysis is performed for a short time duration when the temperature distribution in the particle bed is almost linear along the axis of the bed. This time period permits the most accurate determination of the heat transfer coefficient using the data. Using beds of spherical particles a new correlation is developed for the Nusselt number versus the Reynolds number (5 DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...]

An improved volume of fluid method for two-phase flow computations on collocated grid system / Dong-Liang Sun 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. [041901/1-8] Titre : An improved volume of fluid method for two-phase flow computations on collocated grid system Type de document : texte imprimé Auteurs : Dong-Liang Sun, Auteur ; Yong-Ping Yang, Auteur ; Jin-Liang Xu, Auteur Année de publication : 2011 Article en page(s) : pp. [041901/1-8] Note générale : Physique Langues : Anglais (eng) Mots-clés : ADV-VOF  IDV-VOF  Two-phase  flow  Collacated  grid  system Index. décimale : 536 Chaleur. Thermodynamique Résumé : An improved volume of fluid method called the accurate density and viscosity volume of fluid (ADV-VOF) method is proposed to solve two-phase flow problems. The method has the following features: (1) All operations are performed on a collocated grid system. (2) The piecewise linear interface calculation is used to capture interfaces and perform accurate estimations of cell-edged density and viscosity. (3) The conservative Navier–Stokes equations are solved with the convective term discretized by a second and third order interpolation for convection scheme. (4) A fractional-step method is applied to solve the conservative Navier–Stokes equations, and the BiCGSTAB algorithm is used to solve the algebraic equations by discretizing the pressure-correction equation. The above features guarantee a simple, stable, efficient, and accurate simulation of two-phase flow problems. The effectiveness of the ADV-VOF method is verified by comparing it with the conventional volume of fluid method with rough treatment of cell-edged density and viscosity. It is found that the ADV-VOF method could successfully model the two-phase problems with large density ratio and viscosity ratio between two phases and is better than the conventional volume of fluid method in this respect. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...] [article] An improved volume of fluid method for two-phase flow computations on collocated grid system [texte imprimé] / Dong-Liang Sun, Auteur ; Yong-Ping Yang, Auteur ; Jin-Liang Xu, Auteur . - 2011 . - pp. [041901/1-8]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 4 (Avril 2011) . - pp. [041901/1-8] Mots-clés : ADV-VOF  IDV-VOF  Two-phase  flow  Collacated  grid  system Index. décimale : 536 Chaleur. Thermodynamique Résumé : An improved volume of fluid method called the accurate density and viscosity volume of fluid (ADV-VOF) method is proposed to solve two-phase flow problems. The method has the following features: (1) All operations are performed on a collocated grid system. (2) The piecewise linear interface calculation is used to capture interfaces and perform accurate estimations of cell-edged density and viscosity. (3) The conservative Navier–Stokes equations are solved with the convective term discretized by a second and third order interpolation for convection scheme. (4) A fractional-step method is applied to solve the conservative Navier–Stokes equations, and the BiCGSTAB algorithm is used to solve the algebraic equations by discretizing the pressure-correction equation. The above features guarantee a simple, stable, efficient, and accurate simulation of two-phase flow problems. The effectiveness of the ADV-VOF method is verified by comparing it with the conventional volume of fluid method with rough treatment of cell-edged density and viscosity. It is found that the ADV-VOF method could successfully model the two-phase problems with large density ratio and viscosity ratio between two phases and is better than the conventional volume of fluid method in this respect. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...]

Heat transfer enhancement using laminar gas-liquid segmented plug flows / Y. S. Muzychka 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. [041902/1-9] Titre : Heat transfer enhancement using laminar gas-liquid segmented plug flows Type de document : texte imprimé Auteurs : Y. S. Muzychka, Auteur ; Edmond J. Walsh, Auteur ; P. Walsh, Auteur Année de publication : 2011 Article en page(s) : pp. [041902/1-9] Note générale : Physique Langues : Anglais (eng) Mots-clés : Heat  transfer  Segmented  flow  Two  phase  flow  Thermal  enhancement  Graetz  flow  Plug  flow  Poiseuille  flow  Taylor  flow Index. décimale : 536 Chaleur. Thermodynamique Résumé : Heat transfer enhancement using segmented nonboiling gas-liquid flow is examined. Segmentation results in a two phase flow of liquid/gas having a constant liquid fraction; i.e., no phase change occurs. In this flow configuration, enhanced heat transfer occurs as a result of a shorter effective thermal length due to internal fluid circulation in the liquid plugs. A simple theory for laminar segmented flows is developed based on scaled Graetz theory and comparisons made with existing published data from the literature and new experimental data obtained in a companion study. The proposed model is valid for an isothermal tube wall provided that the axial residence time of the flow is such that dimensionless tube length L[small star, filled]<0.1. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...] [article] Heat transfer enhancement using laminar gas-liquid segmented plug flows [texte imprimé] / Y. S. Muzychka, Auteur ; Edmond J. Walsh, Auteur ; P. Walsh, Auteur . - 2011 . - pp. [041902/1-9]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 4 (Avril 2011) . - pp. [041902/1-9] Mots-clés : Heat  transfer  Segmented  flow  Two  phase  flow  Thermal  enhancement  Graetz  flow  Plug  flow  Poiseuille  flow  Taylor  flow Index. décimale : 536 Chaleur. Thermodynamique Résumé : Heat transfer enhancement using segmented nonboiling gas-liquid flow is examined. Segmentation results in a two phase flow of liquid/gas having a constant liquid fraction; i.e., no phase change occurs. In this flow configuration, enhanced heat transfer occurs as a result of a shorter effective thermal length due to internal fluid circulation in the liquid plugs. A simple theory for laminar segmented flows is developed based on scaled Graetz theory and comparisons made with existing published data from the literature and new experimental data obtained in a companion study. The proposed model is valid for an isothermal tube wall provided that the axial residence time of the flow is such that dimensionless tube length L[small star, filled]<0.1. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...]

Enhancement and prediction of heat transfer rate in turbulent flow through tube with perforated twisted tape inserts / J. U. Ahamed 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. [041903/1-9] Titre : Enhancement and prediction of heat transfer rate in turbulent flow through tube with perforated twisted tape inserts : a new correlation Type de document : texte imprimé Auteurs : J. U. Ahamed, Auteur ; M. A. Wazed, Auteur ; S. Ahmed, Auteur Année de publication : 2011 Article en page(s) : pp. [041903/1-9] Note générale : Physique Langues : Anglais (eng) Mots-clés : Nusselt  number  Perforated  twisted  Friction  factor  Turbulent  flow Index. décimale : 536 Chaleur. Thermodynamique Résumé : An experimental investigation has been carried out for turbulent flow in a tube with perforated twisted tape inserts. The mild steel twisted tape inserts with circular holes of different diameters (i.e., perforation) are used in the flow field. An intensive laboratory study is conducted for heat transfer and pressure drop characteristics in the tubes for turbulent flow with various airflow rates. Heat transfer and pressure drop data are engendered for a wide range Reynolds number (1.3×104–5.2×104). Tube wall temperature, pressure drop, air velocity, and its temperature are measured both for plain tube and for tube with perforated twisted tape inserts. Heat transfer coefficients, Nusselt number, pumping power, and heat transfer effectiveness are calculated for both cases. Experimental results showed that perforated twisted inserts of different geometry in a circular tube enhanced the heat transfer rate with an increase in friction factor and pumping power for turbulent flow. The pumping power, heat transfer coefficient, and effectiveness in the tube with the twisted tape inserts are found to increase up to 1.8, 5.5, and 4.0 times of those for the plain tube for same Reynolds number, respectively. Finally, a correlation is developed for prediction of the heat transfer rate for turbulent flow through a circular tube with perforated twisted tape inserts. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...] [article] Enhancement and prediction of heat transfer rate in turbulent flow through tube with perforated twisted tape inserts : a new correlation [texte imprimé] / J. U. Ahamed, Auteur ; M. A. Wazed, Auteur ; S. Ahmed, Auteur . - 2011 . - pp. [041903/1-9]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 4 (Avril 2011) . - pp. [041903/1-9] Mots-clés : Nusselt  number  Perforated  twisted  Friction  factor  Turbulent  flow Index. décimale : 536 Chaleur. Thermodynamique Résumé : An experimental investigation has been carried out for turbulent flow in a tube with perforated twisted tape inserts. The mild steel twisted tape inserts with circular holes of different diameters (i.e., perforation) are used in the flow field. An intensive laboratory study is conducted for heat transfer and pressure drop characteristics in the tubes for turbulent flow with various airflow rates. Heat transfer and pressure drop data are engendered for a wide range Reynolds number (1.3×104–5.2×104). Tube wall temperature, pressure drop, air velocity, and its temperature are measured both for plain tube and for tube with perforated twisted tape inserts. Heat transfer coefficients, Nusselt number, pumping power, and heat transfer effectiveness are calculated for both cases. Experimental results showed that perforated twisted inserts of different geometry in a circular tube enhanced the heat transfer rate with an increase in friction factor and pumping power for turbulent flow. The pumping power, heat transfer coefficient, and effectiveness in the tube with the twisted tape inserts are found to increase up to 1.8, 5.5, and 4.0 times of those for the plain tube for same Reynolds number, respectively. Finally, a correlation is developed for prediction of the heat transfer rate for turbulent flow through a circular tube with perforated twisted tape inserts. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...]

Intraparticle mass transfer in adsorption heat pumps / Alexander Raymond 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. [042001/1-13] Titre : Intraparticle mass transfer in adsorption heat pumps : limitations of the linear driving force approximation Type de document : texte imprimé Auteurs : Alexander Raymond, Auteur ; Srinivas Garimella, Auteur Année de publication : 2011 Article en page(s) : pp. [042001/1-13] Note générale : Physique Langues : Anglais (eng) Mots-clés : Adsorption  Diffusion  Flow  simulation  Gels  Heat  pumps  Heat  transfer  Mass  transfer  Two-phase  flow Index. décimale : 536 Chaleur. Thermodynamique Résumé : Adsorption heat pumps and chillers (ADHPCs) can utilize solar or waste heat to provide space conditioning, process heating or cooling, or energy storage. In these devices, intraparticle diffusion is shown to present a significant mass transfer resistance compared with interparticle permeation. Therefore, accurate modeling of intraparticle adsorbate mass transfer is essential for the accurate prediction of overall ADHPC performance. The linear driving force (LDF) approximation is often used to model intraparticle mass transfer in place of more detailed equations because of its computational simplicity. This paper directly compares the adsorbate contents predicted using the LDF and Fickian diffusion (FD) equations for cylindrical and spherical geometries. These geometries are typical of adsorbents commonly used in adsorption refrigeration such as cylindrical activated carbon fibers (ACFs) and spherical silica gel particles. In addition to the conventional LDF approximation, an empirical LDF approximation proposed by El-Sharkawy et al. (2006, “A Study on the Kinetics of Ethanol-Activated Carbon Fiber: Theory and Experiments,” Int. J. Heat Mass Transfer, 49(17–18), pp. 3104–3110) for ACF-ethanol (cylindrical geometry) is compared with the FD solution. By analyzing the relative error of the LDF approximation compared with the FD solution for an isothermal step-change boundary condition, the conditions under which the LDF approximation agrees with the FD equation are evaluated. It is shown that for a given working pair, agreement between the LDF and FD equations is affected by diffusivity, particle radius, half-cycle time, initial adsorbate content, and equilibrium adsorbate content. A step change in surface adsorbate content for an isothermal particle is shown to be the boundary condition that yields the maximum LDF error, and therefore provides a conservative bound for the LDF error under nonisothermal conditions. The trends exhibited by the ACF-ethanol and silica gel-water working pairs are generalized through dimensionless time and dimensionless driving adsorbate content, and LDF error is mapped using these two variables. This map may be used to determine ranges of applicability of the LDF approximation in an ADHPC model. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...] [article] Intraparticle mass transfer in adsorption heat pumps : limitations of the linear driving force approximation [texte imprimé] / Alexander Raymond, Auteur ; Srinivas Garimella, Auteur . - 2011 . - pp. [042001/1-13]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 4 (Avril 2011) . - pp. [042001/1-13] Mots-clés : Adsorption  Diffusion  Flow  simulation  Gels  Heat  pumps  Heat  transfer  Mass  transfer  Two-phase  flow Index. décimale : 536 Chaleur. Thermodynamique Résumé : Adsorption heat pumps and chillers (ADHPCs) can utilize solar or waste heat to provide space conditioning, process heating or cooling, or energy storage. In these devices, intraparticle diffusion is shown to present a significant mass transfer resistance compared with interparticle permeation. Therefore, accurate modeling of intraparticle adsorbate mass transfer is essential for the accurate prediction of overall ADHPC performance. The linear driving force (LDF) approximation is often used to model intraparticle mass transfer in place of more detailed equations because of its computational simplicity. This paper directly compares the adsorbate contents predicted using the LDF and Fickian diffusion (FD) equations for cylindrical and spherical geometries. These geometries are typical of adsorbents commonly used in adsorption refrigeration such as cylindrical activated carbon fibers (ACFs) and spherical silica gel particles. In addition to the conventional LDF approximation, an empirical LDF approximation proposed by El-Sharkawy et al. (2006, “A Study on the Kinetics of Ethanol-Activated Carbon Fiber: Theory and Experiments,” Int. J. Heat Mass Transfer, 49(17–18), pp. 3104–3110) for ACF-ethanol (cylindrical geometry) is compared with the FD solution. By analyzing the relative error of the LDF approximation compared with the FD solution for an isothermal step-change boundary condition, the conditions under which the LDF approximation agrees with the FD equation are evaluated. It is shown that for a given working pair, agreement between the LDF and FD equations is affected by diffusivity, particle radius, half-cycle time, initial adsorbate content, and equilibrium adsorbate content. A step change in surface adsorbate content for an isothermal particle is shown to be the boundary condition that yields the maximum LDF error, and therefore provides a conservative bound for the LDF error under nonisothermal conditions. The trends exhibited by the ACF-ethanol and silica gel-water working pairs are generalized through dimensionless time and dimensionless driving adsorbate content, and LDF error is mapped using these two variables. This map may be used to determine ranges of applicability of the LDF approximation in an ADHPC model. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...]

Heat transfer from freely suspended bimaterial microcantilevers / Arvind Narayanaswamy 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. [042401/1-6] Titre : Heat transfer from freely suspended bimaterial microcantilevers Type de document : texte imprimé Auteurs : Arvind Narayanaswamy, Auteur ; Ning Gu, Auteur Année de publication : 2011 Article en page(s) : pp. [042401/1-6] Note générale : Physique Langues : Anglais (eng) Mots-clés : Thermal  conductance  Heated  microcantilever  Photothermal  heating  Atomic  force  microscope Index. décimale : 536 Chaleur. Thermodynamique Résumé : Bimaterial atomic force microscope cantilevers have been used extensively over the last 15 years as physical, chemical, and biological sensors. As a thermal sensor, the static deflection of bimaterial cantilevers, due to the mismatch of the coefficient of thermal expansion between the two materials, has been used to measure temperature changes as small as 10−6 K, heat transfer rate as small as 40 pW, and energy changes as small as 10 fJ. Bimaterial cantilevers have also been used to measure “heat transfer-distance” curves—a heat transfer analogy of the force-distance curves obtained using atomic force microscopes. In this work, we concentrate on the characterization of heat transfer from the microcantilever. The thermomechanical response of a bimaterial cantilever is used to determine the (1) thermal conductance of a bimaterial cantilever, and (2) overall thermal conductance from the cantilever to the ambient. The thermal conductance of a rectangular gold coated silicon nitride cantilever is Gc=4.09±0.04 µW K−1. The overall thermal conductance from the cantilever to the ambient (at atmospheric pressure) is Ga=55.05±0.69 µW K−1. The effective heat transfer coefficient from the cantilever to the ambient (at atmospheric pressure) is determined to be [approximate]3400 W m−2 K−1. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...] [article] Heat transfer from freely suspended bimaterial microcantilevers [texte imprimé] / Arvind Narayanaswamy, Auteur ; Ning Gu, Auteur . - 2011 . - pp. [042401/1-6]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 4 (Avril 2011) . - pp. [042401/1-6] Mots-clés : Thermal  conductance  Heated  microcantilever  Photothermal  heating  Atomic  force  microscope Index. décimale : 536 Chaleur. Thermodynamique Résumé : Bimaterial atomic force microscope cantilevers have been used extensively over the last 15 years as physical, chemical, and biological sensors. As a thermal sensor, the static deflection of bimaterial cantilevers, due to the mismatch of the coefficient of thermal expansion between the two materials, has been used to measure temperature changes as small as 10−6 K, heat transfer rate as small as 40 pW, and energy changes as small as 10 fJ. Bimaterial cantilevers have also been used to measure “heat transfer-distance” curves—a heat transfer analogy of the force-distance curves obtained using atomic force microscopes. In this work, we concentrate on the characterization of heat transfer from the microcantilever. The thermomechanical response of a bimaterial cantilever is used to determine the (1) thermal conductance of a bimaterial cantilever, and (2) overall thermal conductance from the cantilever to the ambient. The thermal conductance of a rectangular gold coated silicon nitride cantilever is Gc=4.09±0.04 µW K−1. The overall thermal conductance from the cantilever to the ambient (at atmospheric pressure) is Ga=55.05±0.69 µW K−1. The effective heat transfer coefficient from the cantilever to the ambient (at atmospheric pressure) is determined to be [approximate]3400 W m−2 K−1. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...]

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& [...]

Measurement of time-averaged turbulent free convection in a tall enclosure using interferometry / M. E. Poulad 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. [042501/1-8] Titre : Measurement of time-averaged turbulent free convection in a tall enclosure using interferometry Type de document : texte imprimé Auteurs : M. E. Poulad, Auteur ; D. Naylor, Auteur ; P. H. Oosthuizen, Auteur Année de publication : 2011 Article en page(s) : pp. [042501/1-8] Note générale : Physique Langues : Anglais (eng) Mots-clés : Interferometry  Convective  heat  transfer  Turbulence  Free  convection Index. décimale : 536 Chaleur. Thermodynamique Résumé : Laser interferometry is combined with high-speed digital cinematography to measure time-averaged transient and turbulent convective heat transfer rates. The method is applied to study free convection in a tall vertical air-filled enclosure. Measurements are made at three wall spacings in the turbulent flow regime (5.2×104<=RaW<=2.8×105). An automated image processing algorithm is used to calculate the instantaneous local heat flux from a sequence of interferograms that is captured by a high-speed camera. The local Nusselt number distributions on the hot and cold walls are obtained by time-averaging the fluctuations in local heat flux. The effects of key experimental parameters, such as the camera frame rate and the total image capture time, are investigated. For the current problem, it is shown that a total capture interval of about 10 s is required to accurately measure the time-average local Nusselt number. Within the measurement uncertainty, the average Nusselt number results are in agreement with a widely used empirical correlation from the literature. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...] [article] Measurement of time-averaged turbulent free convection in a tall enclosure using interferometry [texte imprimé] / M. E. Poulad, Auteur ; D. Naylor, Auteur ; P. H. Oosthuizen, Auteur . - 2011 . - pp. [042501/1-8]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 4 (Avril 2011) . - pp. [042501/1-8] Mots-clés : Interferometry  Convective  heat  transfer  Turbulence  Free  convection Index. décimale : 536 Chaleur. Thermodynamique Résumé : Laser interferometry is combined with high-speed digital cinematography to measure time-averaged transient and turbulent convective heat transfer rates. The method is applied to study free convection in a tall vertical air-filled enclosure. Measurements are made at three wall spacings in the turbulent flow regime (5.2×104<=RaW<=2.8×105). An automated image processing algorithm is used to calculate the instantaneous local heat flux from a sequence of interferograms that is captured by a high-speed camera. The local Nusselt number distributions on the hot and cold walls are obtained by time-averaging the fluctuations in local heat flux. The effects of key experimental parameters, such as the camera frame rate and the total image capture time, are investigated. For the current problem, it is shown that a total capture interval of about 10 s is required to accurately measure the time-average local Nusselt number. Within the measurement uncertainty, the average Nusselt number results are in agreement with a widely used empirical correlation from the literature. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...]

Resonance of natural convection inside a bidisperse porous medium enclosure / Arunn Narasimhan 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. [042601/1-9] Titre : Resonance of natural convection inside a bidisperse porous medium enclosure Type de document : texte imprimé Auteurs : Arunn Narasimhan, Auteur ; B. V. K. Reddy, Auteur Année de publication : 2011 Article en page(s) : pp. [042601/1-9] Note générale : Physique Langues : Anglais (eng) Mots-clés : Natural  convection  Resonance  Bidisperse  Monodisperse  Porous  media  Numerical  simulations  Scale  analysis Index. décimale : 536 Chaleur. Thermodynamique Résumé : An enclosure filled with blocks made of a microscale porous medium, separated by macrosize pores, can be treated as a bidisperse porous medium (BDPM) enclosure. This study investigates natural convection resonance inside such a BDPM enclosure subjected to time-periodic heat flux at a side wall, with the opposite wall kept isothermal while the top and bottom walls are adiabatic. The BDPM enclosure is made from uniformly spaced, disconnected, square, porous blocks that form the microporous medium saturated with a fluid of Pr=0.7. For Rayleigh numbers, Ra=108 and 107, the pulsating wall heat flux is varied over a frequency range of 0.01<=f<=0.1, and the bidispersion effect is induced by varying both the internal (micropore) Darcy number (DaI) and external (macropore) Darcy number DaE. Natural convection resonance is observed in the BDPM enclosure and the resonance heating frequency fr increases with Ra, DaI, and DaE. However, fr of the BDPM enclosure is always less than that of the corresponding clear fluid enclosure limit (at DaI-->[infinity]). Predictions of fr using a modified scale analysis incorporating BDPM effects agree well with that arrived by numerical methods. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...] [article] Resonance of natural convection inside a bidisperse porous medium enclosure [texte imprimé] / Arunn Narasimhan, Auteur ; B. V. K. Reddy, Auteur . - 2011 . - pp. [042601/1-9]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 4 (Avril 2011) . - pp. [042601/1-9] Mots-clés : Natural  convection  Resonance  Bidisperse  Monodisperse  Porous  media  Numerical  simulations  Scale  analysis Index. décimale : 536 Chaleur. Thermodynamique Résumé : An enclosure filled with blocks made of a microscale porous medium, separated by macrosize pores, can be treated as a bidisperse porous medium (BDPM) enclosure. This study investigates natural convection resonance inside such a BDPM enclosure subjected to time-periodic heat flux at a side wall, with the opposite wall kept isothermal while the top and bottom walls are adiabatic. The BDPM enclosure is made from uniformly spaced, disconnected, square, porous blocks that form the microporous medium saturated with a fluid of Pr=0.7. For Rayleigh numbers, Ra=108 and 107, the pulsating wall heat flux is varied over a frequency range of 0.01<=f<=0.1, and the bidispersion effect is induced by varying both the internal (micropore) Darcy number (DaI) and external (macropore) Darcy number DaE. Natural convection resonance is observed in the BDPM enclosure and the resonance heating frequency fr increases with Ra, DaI, and DaE. However, fr of the BDPM enclosure is always less than that of the corresponding clear fluid enclosure limit (at DaI-->[infinity]). Predictions of fr using a modified scale analysis incorporating BDPM effects agree well with that arrived by numerical methods. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...]

Global spectral methods in gas radiation / V. P. Solovjov 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. [042701/1-9] Titre : Global spectral methods in gas radiation : the exact limit of the SLW model and its relationship to the ADF and FSK methods Type de document : texte imprimé Auteurs : V. P. Solovjov, Auteur ; B. W. Webb, Auteur Année de publication : 2011 Article en page(s) : pp. [042701/1-9] Note générale : Physique Langues : Anglais (eng) Mots-clés : Gas  radiation  SLW  model Index. décimale : 536 Chaleur. Thermodynamique Résumé : The exact form of the spectral line weighted-sum-of-gray-gases (SLW) model is developed as a limiting case of the classical SLW method when the number of gray gases in the classical model approaches infinity. Solutions of the exact SLW radiative transfer equation are obtained in the case of isothermal media. It is demonstrated that the accuracy of the exact SLW method is limited only by the accuracy of the absorption-line blackbody distribution function (ALBDF) correlations used for the characterization of the absorption spectrum. This work also theoretically and rigorously demonstrates for the first time the relationship among the SLW, absorption distribution function (ADF), and full spectrum k-distribution (FSK) models. The theoretical foundation is laid for the extension of the exact method in the case of nonisothermal media. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...] [article] Global spectral methods in gas radiation : the exact limit of the SLW model and its relationship to the ADF and FSK methods [texte imprimé] / V. P. Solovjov, Auteur ; B. W. Webb, Auteur . - 2011 . - pp. [042701/1-9]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 4 (Avril 2011) . - pp. [042701/1-9] Mots-clés : Gas  radiation  SLW  model Index. décimale : 536 Chaleur. Thermodynamique Résumé : The exact form of the spectral line weighted-sum-of-gray-gases (SLW) model is developed as a limiting case of the classical SLW method when the number of gray gases in the classical model approaches infinity. Solutions of the exact SLW radiative transfer equation are obtained in the case of isothermal media. It is demonstrated that the accuracy of the exact SLW method is limited only by the accuracy of the absorption-line blackbody distribution function (ALBDF) correlations used for the characterization of the absorption spectrum. This work also theoretically and rigorously demonstrates for the first time the relationship among the SLW, absorption distribution function (ADF), and full spectrum k-distribution (FSK) models. The theoretical foundation is laid for the extension of the exact method in the case of nonisothermal media. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...]

Effects of film evaporation and condensation on oscillatory flow and heat transfer in an oscillating heat pipe / Wei Shao 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. [042901/1-11] Titre : Effects of film evaporation and condensation on oscillatory flow and heat transfer in an oscillating heat pipe Type de document : texte imprimé Auteurs : Wei Shao, Auteur ; Yuwen Zhang, Auteur Année de publication : 2011 Article en page(s) : pp. [042901/1-11] Note générale : Physique Langues : Anglais (eng) Mots-clés : Film  evaporation  Film  condensation  Oscillating  heat  pipe Index. décimale : 536 Chaleur. Thermodynamique Résumé : An advanced theoretical model of a U-shaped minichannel, a building block of a closed-end oscillating heat pipe, has been developed. Thin film evaporation in the evaporator and thin film condensation in the condenser, axial variation of surface temperature, and pressure loss at the bend are incorporated in this model. The sensible heat transfer coefficients between the liquid slug and the wall are obtained by analytical solution for laminar liquid flow and by empirical correlations for turbulent liquid flow. The effects of the inner diameter, evaporator temperature on the thermally induced oscillatory flow and heat transfer performance, and the mechanism of film condensation and evaporation are investigated. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...] [article] Effects of film evaporation and condensation on oscillatory flow and heat transfer in an oscillating heat pipe [texte imprimé] / Wei Shao, Auteur ; Yuwen Zhang, Auteur . - 2011 . - pp. [042901/1-11]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 4 (Avril 2011) . - pp. [042901/1-11] Mots-clés : Film  evaporation  Film  condensation  Oscillating  heat  pipe Index. décimale : 536 Chaleur. Thermodynamique Résumé : An advanced theoretical model of a U-shaped minichannel, a building block of a closed-end oscillating heat pipe, has been developed. Thin film evaporation in the evaporator and thin film condensation in the condenser, axial variation of surface temperature, and pressure loss at the bend are incorporated in this model. The sensible heat transfer coefficients between the liquid slug and the wall are obtained by analytical solution for laminar liquid flow and by empirical correlations for turbulent liquid flow. The effects of the inner diameter, evaporator temperature on the thermally induced oscillatory flow and heat transfer performance, and the mechanism of film condensation and evaporation are investigated. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...]

Efficiency comparison between circular and semicircular fins circumscribing circular pipes / R. Chakraborty 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. [044501/1-4] Titre : Efficiency comparison between circular and semicircular fins circumscribing circular pipes Type de document : texte imprimé Auteurs : R. Chakraborty, Auteur ; A. Sirkar, Auteur Année de publication : 2011 Article en page(s) : pp. [044501/1-4] Note générale : Physique Langues : Anglais (eng) Mots-clés : Semicrircular  fin  Circular  fin  Fin  efficiency Index. décimale : 536 Chaleur. Thermodynamique Résumé : A new design of fin has been conceived, which is in the shape of a semicircular strip. A step-by-step straightforward detailed derivation of the governing equations for two-dimensional temperature distribution in a semicircular fin has been presented, assuming a third degree polynomial. Numerical results are presented to illustrate the effects of pipe size and the number of semicircular fins on the thermal performance of the fin. It has been shown mathematically that the efficiency of a semicircular fin can be greater than that of a circular fin, having same total volume of fin material when employed over the circumference of a circular pipe. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...] [article] Efficiency comparison between circular and semicircular fins circumscribing circular pipes [texte imprimé] / R. Chakraborty, Auteur ; A. Sirkar, Auteur . - 2011 . - pp. [044501/1-4]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 4 (Avril 2011) . - pp. [044501/1-4] Mots-clés : Semicrircular  fin  Circular  fin  Fin  efficiency Index. décimale : 536 Chaleur. Thermodynamique Résumé : A new design of fin has been conceived, which is in the shape of a semicircular strip. A step-by-step straightforward detailed derivation of the governing equations for two-dimensional temperature distribution in a semicircular fin has been presented, assuming a third degree polynomial. Numerical results are presented to illustrate the effects of pipe size and the number of semicircular fins on the thermal performance of the fin. It has been shown mathematically that the efficiency of a semicircular fin can be greater than that of a circular fin, having same total volume of fin material when employed over the circumference of a circular pipe. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...]

Improved discrete ordinates method for ray effects mitigation / Zhi-Feng Huang 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. [044502/1-5] Titre : Improved discrete ordinates method for ray effects mitigation Type de document : texte imprimé Auteurs : Zhi-Feng Huang, Auteur ; Huai-Chun Zhou, Auteur ; Pei-feng Hsu, Auteur Année de publication : 2011 Article en page(s) : pp. [044502/1-5] Note générale : Physique Langues : Anglais (eng) Mots-clés : Radiative  transfer  Three  dimensional  Ray  effects  Isotropic  scattering  Discrete  ordinates  method Index. décimale : 536 Chaleur. Thermodynamique Résumé : A new and improved method based on the concept of discrete ordinates scheme with infinitely small weights (DOS+ISW) is developed for modeling radiative heat transfer in three-dimensional participating media. To demonstrate the effectiveness of the method in mitigating ray effects, the ray effects caused by (1) abrupt step changes in the boundary conditions and (2) the stepwise variation of the medium emissive power are considered. In this work, angular quadrature sets with large number of discrete ordinate directions are chosen to mitigate ray effects while at the same time keeping the computational time increase to a minimum. Comparing with the conventional discrete ordinates method, the difference is that intensities in these directions are calculated by DOS+ISW method. Intensity with fine directional resolution calculated by this method is validated by comparing with that of reverse Monte Carlo method. The large number of discrete ordinate directions used in the new method becomes computationally prohibitive in the conventional discrete ordinates method due to the increased computer memory and computation time requirements. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...] [article] Improved discrete ordinates method for ray effects mitigation [texte imprimé] / Zhi-Feng Huang, Auteur ; Huai-Chun Zhou, Auteur ; Pei-feng Hsu, Auteur . - 2011 . - pp. [044502/1-5]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 4 (Avril 2011) . - pp. [044502/1-5] Mots-clés : Radiative  transfer  Three  dimensional  Ray  effects  Isotropic  scattering  Discrete  ordinates  method Index. décimale : 536 Chaleur. Thermodynamique Résumé : A new and improved method based on the concept of discrete ordinates scheme with infinitely small weights (DOS+ISW) is developed for modeling radiative heat transfer in three-dimensional participating media. To demonstrate the effectiveness of the method in mitigating ray effects, the ray effects caused by (1) abrupt step changes in the boundary conditions and (2) the stepwise variation of the medium emissive power are considered. In this work, angular quadrature sets with large number of discrete ordinate directions are chosen to mitigate ray effects while at the same time keeping the computational time increase to a minimum. Comparing with the conventional discrete ordinates method, the difference is that intensities in these directions are calculated by DOS+ISW method. Intensity with fine directional resolution calculated by this method is validated by comparing with that of reverse Monte Carlo method. The large number of discrete ordinate directions used in the new method becomes computationally prohibitive in the conventional discrete ordinates method due to the increased computer memory and computation time requirements. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...]

Heat transfer properties and energy-exergy efficiency in a finned cross-flow heat recovery unit / Isak Kotcioglu 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. [044503/1-4] Titre : Heat transfer properties and energy-exergy efficiency in a finned cross-flow heat recovery unit Type de document : texte imprimé Auteurs : Isak Kotcioglu, Auteur ; Ahmet Cansiz, Auteur Année de publication : 2011 Article en page(s) : pp. [044503/1-4] Note générale : Physique Langues : Anglais (eng) Mots-clés : Exergy  loss  Heat  recovery  Cross  flow  Entropy  generation Index. décimale : 536 Chaleur. Thermodynamique Résumé : In this study, a cross-flow heat recovery-exchanger system operating with unmixed fluids was manufactured and tested. The thermodynamic analysis of the system was presented via determining the variations of exergy loss with Reynolds number. The analysis also included the effects of convergent and divergent plate-type winglets on heat transfer properties of the designed system. Experimental tests consisted of temperature and pressure drop measurements for the Reynolds numbers (3000 and 12,000) according to the working conditions of the boiler, fan, preheater, and reheater. The effects of inlet conditions of the working fluids on the heat transfer characteristics were correlated via entropy generation number and exergy loss. The variation of the effectiveness with the number of transfer unit of heat recovery unit was calculated and discussed in terms of literature. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...] [article] Heat transfer properties and energy-exergy efficiency in a finned cross-flow heat recovery unit [texte imprimé] / Isak Kotcioglu, Auteur ; Ahmet Cansiz, Auteur . - 2011 . - pp. [044503/1-4]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 4 (Avril 2011) . - pp. [044503/1-4] Mots-clés : Exergy  loss  Heat  recovery  Cross  flow  Entropy  generation Index. décimale : 536 Chaleur. Thermodynamique Résumé : In this study, a cross-flow heat recovery-exchanger system operating with unmixed fluids was manufactured and tested. The thermodynamic analysis of the system was presented via determining the variations of exergy loss with Reynolds number. The analysis also included the effects of convergent and divergent plate-type winglets on heat transfer properties of the designed system. Experimental tests consisted of temperature and pressure drop measurements for the Reynolds numbers (3000 and 12,000) according to the working conditions of the boiler, fan, preheater, and reheater. The effects of inlet conditions of the working fluids on the heat transfer characteristics were correlated via entropy generation number and exergy loss. The variation of the effectiveness with the number of transfer unit of heat recovery unit was calculated and discussed in terms of literature. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...]

Numerical inversion of laplace transform for time resolved thermal characterization experiment / J. Toutain 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. [044504/1-3] Titre : Numerical inversion of laplace transform for time resolved thermal characterization experiment Type de document : texte imprimé Auteurs : J. Toutain, Auteur ; J.-L. Battaglia, Auteur ; C. Pradere, Auteur Année de publication : 2011 Article en page(s) : pp. [044504/1-3] Note générale : Physique Langues : Anglais (eng) Mots-clés : Thermal  characterization  Analytical  solution  Numerical  Laplace  inversion  Fourier  series Index. décimale : 536 Chaleur. Thermodynamique Résumé : The aim of this technical brief is to test numerical inverse Laplace transform methods with application in the framework of the thermal characterization experiment. The objective is to find the most reliable technique in the case of a time resolved experiment based on a thermal disturbance in the form of a periodic function or a distribution. The reliability of methods based on the Fourier series methods is demonstrated. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...] [article] Numerical inversion of laplace transform for time resolved thermal characterization experiment [texte imprimé] / J. Toutain, Auteur ; J.-L. Battaglia, Auteur ; C. Pradere, Auteur . - 2011 . - pp. [044504/1-3]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 4 (Avril 2011) . - pp. [044504/1-3] Mots-clés : Thermal  characterization  Analytical  solution  Numerical  Laplace  inversion  Fourier  series Index. décimale : 536 Chaleur. Thermodynamique Résumé : The aim of this technical brief is to test numerical inverse Laplace transform methods with application in the framework of the thermal characterization experiment. The objective is to find the most reliable technique in the case of a time resolved experiment based on a thermal disturbance in the form of a periodic function or a distribution. The reliability of methods based on the Fourier series methods is demonstrated. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...]

Re-examining electron-fermi relaxation in gold films with a nonlinear thermoreflectance model / Patrick E. Hopkins 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. [044505/1-4] Titre : Re-examining electron-fermi relaxation in gold films with a nonlinear thermoreflectance model Type de document : texte imprimé Auteurs : Patrick E. Hopkins, Auteur ; Leslie M. Phinney, Auteur ; Justin R. Serrano, Auteur Année de publication : 2011 Article en page(s) : pp. [044505/1-4] Note générale : Physique Langues : Anglais (eng) Mots-clés : Fermi  relaxation  Electron-electron  scattering  Thermoreflectance Index. décimale : 536 Chaleur. Thermodynamique Résumé : In this work, we examine Fermi relaxation in 20 nm Au films with pump-probe themoreflectance using a thin film, intraband thermoreflectance model. Our results indicate that the Fermi relaxation of a perturbed electron system occurs approximately 1.10±0.05 ps after absorption of a 785 nm, 185 fs laser pulse. This is in agreement with reported values from electron emission experiments but is higher than the Fermi relaxation time determined from previous thermoreflectance measurements. This discrepancy arises due to thermoreflectance modeling and elucidates the importance of the use of a proper thermoreflectance model for thermophysical property determination in pump-probe experiments. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...] [article] Re-examining electron-fermi relaxation in gold films with a nonlinear thermoreflectance model [texte imprimé] / Patrick E. Hopkins, Auteur ; Leslie M. Phinney, Auteur ; Justin R. Serrano, Auteur . - 2011 . - pp. [044505/1-4]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 4 (Avril 2011) . - pp. [044505/1-4] Mots-clés : Fermi  relaxation  Electron-electron  scattering  Thermoreflectance Index. décimale : 536 Chaleur. Thermodynamique Résumé : In this work, we examine Fermi relaxation in 20 nm Au films with pump-probe themoreflectance using a thin film, intraband thermoreflectance model. Our results indicate that the Fermi relaxation of a perturbed electron system occurs approximately 1.10±0.05 ps after absorption of a 785 nm, 185 fs laser pulse. This is in agreement with reported values from electron emission experiments but is higher than the Fermi relaxation time determined from previous thermoreflectance measurements. This discrepancy arises due to thermoreflectance modeling and elucidates the importance of the use of a proper thermoreflectance model for thermophysical property determination in pump-probe experiments. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...]

Forced convection in a polygonal duct with a circular core / Wang, C. Y. 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. [044506/1-4] Titre : Forced convection in a polygonal duct with a circular core Type de document : texte imprimé Auteurs : Wang, C. Y., Auteur Année de publication : 2011 Article en page(s) : pp. [044506/1-4] Note générale : Physique Langues : Anglais (eng) Mots-clés : Forced  convection  Duct  Polygonal  Core Index. décimale : 536 Chaleur. Thermodynamique Résumé : The H1 forced convection through a regular polygonal duct with a centered core is studied using eigenfunction expansions and point match. Accurate Nusselt numbers for the full range of core radii are presented. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...] [article] Forced convection in a polygonal duct with a circular core [texte imprimé] / Wang, C. Y., Auteur . - 2011 . - pp. [044506/1-4]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 4 (Avril 2011) . - pp. [044506/1-4] Mots-clés : Forced  convection  Duct  Polygonal  Core Index. décimale : 536 Chaleur. Thermodynamique Résumé : The H1 forced convection through a regular polygonal duct with a centered core is studied using eigenfunction expansions and point match. Accurate Nusselt numbers for the full range of core radii are presented. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...]

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