Dépouillements

A Review of high-heat-flux heat removal technologies / M. A. Ebadian 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. [110801/1-11] Titre : A Review of high-heat-flux heat removal technologies Type de document : texte imprimé Auteurs : M. A. Ebadian, Auteur ; C. X. Lin, Auteur Année de publication : 2012 Article en page(s) : pp. [110801/1-11] Note générale : Physique Langues : Anglais (eng) Mots-clés : Boiling  Drops  Heat  transfer  Jets  Microchannel  flow  Sprays  Two-phase  flow  Wetting Index. décimale : 536 Chaleur. Thermodynamique Résumé : In recent years, high-heat-flux cooling techniques have received great attention from researchers around the world due to its importance in thermal management of both commercial and defense high-power electronic devices. Although impressive progress has been made during the last few decades, high-heat-flux removal still largely remains as a challenging subject that needs further exploration and study. In this paper, we have reviewed recent developments in several high-heat-flux heat removal techniques, including microchannels, jet impingements, sprays, wettability effects, and piezoelectrically driven droplets. High-heat-flux removal can be achieved effectively by either single-phase flow or two-phase flow boiling heat transfer. Better understandings of the underlying heat transfer mechanisms for performance improvement are discussed. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000133000011 [...] [article] A Review of high-heat-flux heat removal technologies [texte imprimé] / M. A. Ebadian, Auteur ; C. X. Lin, Auteur . - 2012 . - pp. [110801/1-11]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 11 (Novembre 2011) . - pp. [110801/1-11] Mots-clés : Boiling  Drops  Heat  transfer  Jets  Microchannel  flow  Sprays  Two-phase  flow  Wetting Index. décimale : 536 Chaleur. Thermodynamique Résumé : In recent years, high-heat-flux cooling techniques have received great attention from researchers around the world due to its importance in thermal management of both commercial and defense high-power electronic devices. Although impressive progress has been made during the last few decades, high-heat-flux removal still largely remains as a challenging subject that needs further exploration and study. In this paper, we have reviewed recent developments in several high-heat-flux heat removal techniques, including microchannels, jet impingements, sprays, wettability effects, and piezoelectrically driven droplets. High-heat-flux removal can be achieved effectively by either single-phase flow or two-phase flow boiling heat transfer. Better understandings of the underlying heat transfer mechanisms for performance improvement are discussed. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000133000011 [...]

Combining integral transforms and bayesian inference in the simultaneous identification of variable thermal conductivity and thermal capacity in heterogeneous media / Carolina P. Naveira-Cotta 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. [111301/1-10] Titre : Combining integral transforms and bayesian inference in the simultaneous identification of variable thermal conductivity and thermal capacity in heterogeneous media Type de document : texte imprimé Auteurs : Carolina P. Naveira-Cotta, Auteur ; Helcio R. B. Orlande, Auteur ; Renato M. Cotta, Auteur Année de publication : 2012 Article en page(s) : pp. [111301/1-10] Note générale : Physique Langues : Anglais (eng) Mots-clés : Bayes  methods  Composite  materials  Disperse  systems  Eigenvalues  and  eigenfunctions  Gaussian  distribution  Heat  conduction  Inference  mechanisms  Inverse  problems  Inverse  transforms  Markov  processes  Monte  Carlo  methods  Physics  computing  Specific  heat  Thermal  conductivity Index. décimale : 536 Chaleur. Thermodynamique Résumé : This work presents the combined use of the integral transform method, for the direct problem solution, and of Bayesian inference, for the inverse problem analysis, in the simultaneous estimation of spatially variable thermal conductivity and thermal capacity for one-dimensional heat conduction within heterogeneous media. The direct problem solution is analytically obtained via integral transforms and the related eigenvalue problem is solved by the generalized integral transform technique (GITT), offering a fast, precise, and robust solution for the transient temperature field. The inverse problem analysis employs a Markov chain Monte Carlo (MCMC) method, through the implementation of the Metropolis-Hastings sampling algorithm. Instead of seeking the functions estimation in the form of local values for the thermal conductivity and capacity, an alternative approach is employed based on the eigenfunction expansion of the thermophysical properties themselves. Then, the unknown parameters become the corresponding series coefficients for the properties eigenfunction expansions. Simulated temperatures obtained via integral transforms are used in the inverse analysis, for a prescribed concentration distribution of the dispersed phase in a heterogeneous media such as particle filled composites. Available correlations for the thermal conductivity and theory of mixtures relations for the thermal capacity are employed to produce the simulated results with high precision in the direct problem solution, while eigenfunction expansions with reduced number of terms are employed in the inverse analysis itself, in order to avoid the inverse crime. Gaussian distributions were used as priors for the parameter estimation procedure. In addition, simulated results with different randomly generated errors were employed in order to test the inverse analysis robustness. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000133000011 [...] [article] Combining integral transforms and bayesian inference in the simultaneous identification of variable thermal conductivity and thermal capacity in heterogeneous media [texte imprimé] / Carolina P. Naveira-Cotta, Auteur ; Helcio R. B. Orlande, Auteur ; Renato M. Cotta, Auteur . - 2012 . - pp. [111301/1-10]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 11 (Novembre 2011) . - pp. [111301/1-10] Mots-clés : Bayes  methods  Composite  materials  Disperse  systems  Eigenvalues  and  eigenfunctions  Gaussian  distribution  Heat  conduction  Inference  mechanisms  Inverse  problems  Inverse  transforms  Markov  processes  Monte  Carlo  methods  Physics  computing  Specific  heat  Thermal  conductivity Index. décimale : 536 Chaleur. Thermodynamique Résumé : This work presents the combined use of the integral transform method, for the direct problem solution, and of Bayesian inference, for the inverse problem analysis, in the simultaneous estimation of spatially variable thermal conductivity and thermal capacity for one-dimensional heat conduction within heterogeneous media. The direct problem solution is analytically obtained via integral transforms and the related eigenvalue problem is solved by the generalized integral transform technique (GITT), offering a fast, precise, and robust solution for the transient temperature field. The inverse problem analysis employs a Markov chain Monte Carlo (MCMC) method, through the implementation of the Metropolis-Hastings sampling algorithm. Instead of seeking the functions estimation in the form of local values for the thermal conductivity and capacity, an alternative approach is employed based on the eigenfunction expansion of the thermophysical properties themselves. Then, the unknown parameters become the corresponding series coefficients for the properties eigenfunction expansions. Simulated temperatures obtained via integral transforms are used in the inverse analysis, for a prescribed concentration distribution of the dispersed phase in a heterogeneous media such as particle filled composites. Available correlations for the thermal conductivity and theory of mixtures relations for the thermal capacity are employed to produce the simulated results with high precision in the direct problem solution, while eigenfunction expansions with reduced number of terms are employed in the inverse analysis itself, in order to avoid the inverse crime. Gaussian distributions were used as priors for the parameter estimation procedure. In addition, simulated results with different randomly generated errors were employed in order to test the inverse analysis robustness. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000133000011 [...]

Pool boiling characteristics of metallic nanofluids / K. Hari Krishna 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. [111501/1-8] Titre : Pool boiling characteristics of metallic nanofluids Type de document : texte imprimé Auteurs : K. Hari Krishna, Auteur ; Harish Ganapathy, Auteur ; G. Sateesh, Auteur Année de publication : 2012 Article en page(s) : pp. [111501/1-8] Note générale : Physique Langues : Anglais (eng) Mots-clés : Boiling  Copper  Evaporation  Heat  transfer  Nanoparticles  Nucleation  Sorption  Surface  roughness  Suspensions  Thermal  conductivity  Two-phase  flow  Water Index. décimale : 536 Chaleur. Thermodynamique Résumé : Nanofluids, solid-liquid suspensions with solid particles of size of the order of few nanometers, have created interest in many researchers because of their enhancement in thermal conductivity and convective heat transfer characteristics. Many studies have been done on the pool boiling characteristics of nanofluids, most of which have been with nanofluids containing oxide nanoparticles owing to the ease in their preparation. Deterioration in boiling heat transfer was observed in some studies. Metallic nanofluids having metal nanoparticles, which are known for their good heat transfer characteristics in bulk regime, reported drastic enhancement in thermal conductivity. The present paper investigates into the pool boiling characteristics of metallic nanofluids, in particular of Cu-H2O nanofluids, on flat copper heater surface. The results indicate that at comparatively low heat fluxes, there is deterioration in boiling heat transfer with very low particle volume fraction of 0.01%, and it increases with volume fraction and shows enhancement with 0.1%. However, the behavior is the other way around at high heat fluxes. The enhancement at low heat fluxes is due to the fact that the effect of formation of thin sorption layer of nanoparticles on heater surface, which causes deterioration by trapping the nucleation sites, is overshadowed by the increase in microlayer evaporation, which is due to enhancement in thermal conductivity. Same trend has been observed with variation in the surface roughness of the heater as well. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000133000011 [...] [article] Pool boiling characteristics of metallic nanofluids [texte imprimé] / K. Hari Krishna, Auteur ; Harish Ganapathy, Auteur ; G. Sateesh, Auteur . - 2012 . - pp. [111501/1-8]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 11 (Novembre 2011) . - pp. [111501/1-8] Mots-clés : Boiling  Copper  Evaporation  Heat  transfer  Nanoparticles  Nucleation  Sorption  Surface  roughness  Suspensions  Thermal  conductivity  Two-phase  flow  Water Index. décimale : 536 Chaleur. Thermodynamique Résumé : Nanofluids, solid-liquid suspensions with solid particles of size of the order of few nanometers, have created interest in many researchers because of their enhancement in thermal conductivity and convective heat transfer characteristics. Many studies have been done on the pool boiling characteristics of nanofluids, most of which have been with nanofluids containing oxide nanoparticles owing to the ease in their preparation. Deterioration in boiling heat transfer was observed in some studies. Metallic nanofluids having metal nanoparticles, which are known for their good heat transfer characteristics in bulk regime, reported drastic enhancement in thermal conductivity. The present paper investigates into the pool boiling characteristics of metallic nanofluids, in particular of Cu-H2O nanofluids, on flat copper heater surface. The results indicate that at comparatively low heat fluxes, there is deterioration in boiling heat transfer with very low particle volume fraction of 0.01%, and it increases with volume fraction and shows enhancement with 0.1%. However, the behavior is the other way around at high heat fluxes. The enhancement at low heat fluxes is due to the fact that the effect of formation of thin sorption layer of nanoparticles on heater surface, which causes deterioration by trapping the nucleation sites, is overshadowed by the increase in microlayer evaporation, which is due to enhancement in thermal conductivity. Same trend has been observed with variation in the surface roughness of the heater as well. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000133000011 [...]

Combined radiation-evaporation model of a liquid droplet layer in space / Ye, Hong 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. [111502/1-7] Titre : Combined radiation-evaporation model of a liquid droplet layer in space Type de document : texte imprimé Auteurs : Ye, Hong, Auteur ; Yu-Long Ma, Auteur Année de publication : 2012 Article en page(s) : pp. [111502/1-7] Note générale : Physique Langues : Anglais (eng) Mots-clés : Automotive  components  Cooling  Drops  Evaporation  Flow  simulation  Heat  radiation  Two-phase  flow Index. décimale : 536 Chaleur. Thermodynamique Résumé : Assuming that the droplet layer is a uniform medium, an evaporation intensity analogous to radiation intensity was defined based on an analysis of vapor molecule transfer characteristics in the droplet layer. An evaporation transfer equation was then established, from which a one-dimensional evaporative mass flux expression was obtained and combined with the radiation heat transfer model. The combined radiation-evaporation model was used to analyze the influence of the exit temperature and the optical thickness of the droplet layer on temperature distribution, evaporation loss rate, and system lifetime. In the case of a certain droplet diameter and a small optical thickness (D1), the numerical results show that temperature decreases approximately linearly with layer length. The evaporation loss rate increases as the exit temperature and optical thickness increase, and the main contribution to the evaporation loss rate comes from the high temperature portion of the liquid layer near the exit of the liquid generator, i.e., the evaporation loss rate increases rapidly in a short length of the liquid droplet layer and approaches a stable value as the length reaches a certain value. With the same working fluid mass overloading proportion of the droplet layer, the system lifetime is mainly determined by the exit temperature of the liquid droplet layer. For example, if the exit temperature decreases from 320 to 310 K, the system lifetime increases by approximately three times. However, system lifetime has a weak relationship with optical thickness. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000133000011 [...] [article] Combined radiation-evaporation model of a liquid droplet layer in space [texte imprimé] / Ye, Hong, Auteur ; Yu-Long Ma, Auteur . - 2012 . - pp. [111502/1-7]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 11 (Novembre 2011) . - pp. [111502/1-7] Mots-clés : Automotive  components  Cooling  Drops  Evaporation  Flow  simulation  Heat  radiation  Two-phase  flow Index. décimale : 536 Chaleur. Thermodynamique Résumé : Assuming that the droplet layer is a uniform medium, an evaporation intensity analogous to radiation intensity was defined based on an analysis of vapor molecule transfer characteristics in the droplet layer. An evaporation transfer equation was then established, from which a one-dimensional evaporative mass flux expression was obtained and combined with the radiation heat transfer model. The combined radiation-evaporation model was used to analyze the influence of the exit temperature and the optical thickness of the droplet layer on temperature distribution, evaporation loss rate, and system lifetime. In the case of a certain droplet diameter and a small optical thickness (D1), the numerical results show that temperature decreases approximately linearly with layer length. The evaporation loss rate increases as the exit temperature and optical thickness increase, and the main contribution to the evaporation loss rate comes from the high temperature portion of the liquid layer near the exit of the liquid generator, i.e., the evaporation loss rate increases rapidly in a short length of the liquid droplet layer and approaches a stable value as the length reaches a certain value. With the same working fluid mass overloading proportion of the droplet layer, the system lifetime is mainly determined by the exit temperature of the liquid droplet layer. For example, if the exit temperature decreases from 320 to 310 K, the system lifetime increases by approximately three times. However, system lifetime has a weak relationship with optical thickness. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000133000011 [...]

Prediction of turbulent convective heat transfer to supercritical CH4/N2 in a vertical circular tube / Zhongxuan Du 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. [111701/1-6] Titre : Prediction of turbulent convective heat transfer to supercritical CH4/N2 in a vertical circular tube Type de document : texte imprimé Auteurs : Zhongxuan Du, Auteur ; Wensheng Lin, Auteur ; Anzhong Gu, Auteur Année de publication : 2012 Article en page(s) : pp. [111701/1-6] Note générale : Physique Langues : Anglais (eng) Mots-clés : Convection  Cooling  Critical  points  Nitrogen  Organic  compounds  Pipe  flow  Turbulence Index. décimale : 536 Chaleur. Thermodynamique Résumé : Cooling of supercritical CH4/N2 mixture is the most important heat transfer process during coalbed methane (CBM) liquefaction. In this paper, numerical studies of the turbulent convective heat transfer of supercritical CH4/N2 flowing inside a vertical circular tube have been conducted with Lam–Bremhorst low Reynolds turbulence model. The present numerical investigations focus on the effects of the nitrogen content, heat flux, and flow orientation. Results indicate that as nitrogen content increases, the maximum heat transfer coefficient gradually decreases and corresponds to lower temperature. Heat transfer coefficient is slightly affected by heat flux in the liquid-like region and increases with increasing heat flux in the gas-like region. Buoyancy effect gradually increases with decreasing bulk temperature, and reaches its maximum at the pseudo-critical point, and then drops as bulk temperature further decreases. It is significant in the liquid-like region and negligible in the gas-like region. At the same time, buoyancy effect enhances heat transfer in the upward flow and impairs it in the downward flow. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000133000011 [...] [article] Prediction of turbulent convective heat transfer to supercritical CH4/N2 in a vertical circular tube [texte imprimé] / Zhongxuan Du, Auteur ; Wensheng Lin, Auteur ; Anzhong Gu, Auteur . - 2012 . - pp. [111701/1-6]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 11 (Novembre 2011) . - pp. [111701/1-6] Mots-clés : Convection  Cooling  Critical  points  Nitrogen  Organic  compounds  Pipe  flow  Turbulence Index. décimale : 536 Chaleur. Thermodynamique Résumé : Cooling of supercritical CH4/N2 mixture is the most important heat transfer process during coalbed methane (CBM) liquefaction. In this paper, numerical studies of the turbulent convective heat transfer of supercritical CH4/N2 flowing inside a vertical circular tube have been conducted with Lam–Bremhorst low Reynolds turbulence model. The present numerical investigations focus on the effects of the nitrogen content, heat flux, and flow orientation. Results indicate that as nitrogen content increases, the maximum heat transfer coefficient gradually decreases and corresponds to lower temperature. Heat transfer coefficient is slightly affected by heat flux in the liquid-like region and increases with increasing heat flux in the gas-like region. Buoyancy effect gradually increases with decreasing bulk temperature, and reaches its maximum at the pseudo-critical point, and then drops as bulk temperature further decreases. It is significant in the liquid-like region and negligible in the gas-like region. At the same time, buoyancy effect enhances heat transfer in the upward flow and impairs it in the downward flow. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000133000011 [...]

Convective heat transfer in a rotor–stator system airgap with a centered natural suction of fluid / Julien Pellé 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. [111702/1-9] Titre : Convective heat transfer in a rotor–stator system airgap with a centered natural suction of fluid Type de document : texte imprimé Auteurs : Julien Pellé, Auteur ; Souad Harmand, Auteur Année de publication : 2012 Article en page(s) : pp. [111702/1-9] Note générale : Physique Langues : Anglais (eng) Mots-clés : convection  heat  transfer  Rotor-stator  syetems  Infrared  thermography  Natural  suction Index. décimale : 536 Chaleur. Thermodynamique Résumé : The present work relates to an experimental study of the local convective heat transfer over the rotor surface in the air-gap of a discoidal rotor–stator system. This configuration is of interest namely, in electrical machines or tubomachinery. Following precedent studies obtained for a single rotating disk or a closed (but unshrouded) rotor–stator system, an air suction comes through the stator and enters the air-gap in this particular work. Determination of Nusselt numbers is based on the use of infrared thermography. The influence of the suction is discussed for an interdisk dimensionless spacing interval, G ranging from 0.01 to 0.16 and for a rotational Reynolds number, Re between 30,000 and 5,16,000. Results shows that the suction could locally provide better cooling than in the closed rotor–stator and in the single disk configurations, even if the main influence is a decrease in the convective heat transfer. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000133000011 [...] [article] Convective heat transfer in a rotor–stator system airgap with a centered natural suction of fluid [texte imprimé] / Julien Pellé, Auteur ; Souad Harmand, Auteur . - 2012 . - pp. [111702/1-9]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 11 (Novembre 2011) . - pp. [111702/1-9] Mots-clés : convection  heat  transfer  Rotor-stator  syetems  Infrared  thermography  Natural  suction Index. décimale : 536 Chaleur. Thermodynamique Résumé : The present work relates to an experimental study of the local convective heat transfer over the rotor surface in the air-gap of a discoidal rotor–stator system. This configuration is of interest namely, in electrical machines or tubomachinery. Following precedent studies obtained for a single rotating disk or a closed (but unshrouded) rotor–stator system, an air suction comes through the stator and enters the air-gap in this particular work. Determination of Nusselt numbers is based on the use of infrared thermography. The influence of the suction is discussed for an interdisk dimensionless spacing interval, G ranging from 0.01 to 0.16 and for a rotational Reynolds number, Re between 30,000 and 5,16,000. Results shows that the suction could locally provide better cooling than in the closed rotor–stator and in the single disk configurations, even if the main influence is a decrease in the convective heat transfer. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000133000011 [...]

Experimental study on single-phase gas flow in microtubes / T. T. Zhang 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. [111703/1-6] Titre : Experimental study on single-phase gas flow in microtubes Type de document : texte imprimé Auteurs : T. T. Zhang, Auteur ; L. Jia, Auteur ; C. W. Li, Auteur Année de publication : 2012 Article en page(s) : pp. [111703/1-6] Note générale : Physique Langues : Anglais (eng) Mots-clés : Microtube  Compressibility  Viscous  heating  Temperature  field Index. décimale : 536 Chaleur. Thermodynamique Résumé : An experimental system for single-phase gas flow in microtubes has been developed. The effects of viscous heating and compressibility on the flow and temperature field were studied for a wide range of governing parameters. Also, an analytical/numerical model of the flow was developed. Numerical results for the flow and heat transfer in the slip flow region were found to agree quite well with the experimental data, lending support to the model. The study provides greater physical insight into and understanding the effects of viscous dissipation and compressibility in microtube flow and the associated heat transfer. In addition, the combined experimental and numerical simulation approaches of the process can be used for control and optimization of systems based on microtube heat transfer. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000133000011 [...] [article] Experimental study on single-phase gas flow in microtubes [texte imprimé] / T. T. Zhang, Auteur ; L. Jia, Auteur ; C. W. Li, Auteur . - 2012 . - pp. [111703/1-6]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 11 (Novembre 2011) . - pp. [111703/1-6] Mots-clés : Microtube  Compressibility  Viscous  heating  Temperature  field Index. décimale : 536 Chaleur. Thermodynamique Résumé : An experimental system for single-phase gas flow in microtubes has been developed. The effects of viscous heating and compressibility on the flow and temperature field were studied for a wide range of governing parameters. Also, an analytical/numerical model of the flow was developed. Numerical results for the flow and heat transfer in the slip flow region were found to agree quite well with the experimental data, lending support to the model. The study provides greater physical insight into and understanding the effects of viscous dissipation and compressibility in microtube flow and the associated heat transfer. In addition, the combined experimental and numerical simulation approaches of the process can be used for control and optimization of systems based on microtube heat transfer. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000133000011 [...]

Thermal assessment of forced convection through metal foam heat exchangers / A. Tamayol 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. [111801/1-7] Titre : Thermal assessment of forced convection through metal foam heat exchangers Type de document : texte imprimé Auteurs : A. Tamayol, Auteur ; K. Hooman, Auteur Année de publication : 2012 Article en page(s) : pp. [111801/1-7] Note générale : Physique Langues : Anglais (eng) Mots-clés : Metal  foams  Forced  convection  Parametric  study  Thermal  resistors  Model  development Index. décimale : 536 Chaleur. Thermodynamique Résumé : Using a thermal resistance approach, forced convection heat transfer through metal foam heat exchangers is studied theoretically. The complex microstructure of metal foams is modeled as a matrix of interconnected solid ligaments forming simple cubic arrays of cylinders. The geometrical parameters are evaluated from existing correlations in the literature with the exception of ligament diameter which is calculated from a compact relationship offered in the present study. The proposed, simple but accurate, thermal resistance model considers: the conduction inside the solid ligaments, the interfacial convection heat transfer, and convection heat transfer to (or from) the solid bounding walls. The present model makes it possible to conduct a parametric study. Based on the generated results, it is observed that the heat transfer rate from the heated plate has a direct relationship with the foam pore per inch (PPI) and solidity. Furthermore, it is noted that increasing the height of the metal foam layer augments the overall heat transfer rate; however, the increment is not linear. Results obtained from the proposed model were successfully compared with experimental data found in the literature for rectangular and tubular metal foam heat exchangers. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000133000011 [...] [article] Thermal assessment of forced convection through metal foam heat exchangers [texte imprimé] / A. Tamayol, Auteur ; K. Hooman, Auteur . - 2012 . - pp. [111801/1-7]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 11 (Novembre 2011) . - pp. [111801/1-7] Mots-clés : Metal  foams  Forced  convection  Parametric  study  Thermal  resistors  Model  development Index. décimale : 536 Chaleur. Thermodynamique Résumé : Using a thermal resistance approach, forced convection heat transfer through metal foam heat exchangers is studied theoretically. The complex microstructure of metal foams is modeled as a matrix of interconnected solid ligaments forming simple cubic arrays of cylinders. The geometrical parameters are evaluated from existing correlations in the literature with the exception of ligament diameter which is calculated from a compact relationship offered in the present study. The proposed, simple but accurate, thermal resistance model considers: the conduction inside the solid ligaments, the interfacial convection heat transfer, and convection heat transfer to (or from) the solid bounding walls. The present model makes it possible to conduct a parametric study. Based on the generated results, it is observed that the heat transfer rate from the heated plate has a direct relationship with the foam pore per inch (PPI) and solidity. Furthermore, it is noted that increasing the height of the metal foam layer augments the overall heat transfer rate; however, the increment is not linear. Results obtained from the proposed model were successfully compared with experimental data found in the literature for rectangular and tubular metal foam heat exchangers. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000133000011 [...]

Obtaining closure for fin-and-tube heat exchanger modeling based on volume averaging theory (VAT) / Feng Zhou 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. [111802/1-8] Titre : Obtaining closure for fin-and-tube heat exchanger modeling based on volume averaging theory (VAT) Type de document : texte imprimé Auteurs : Feng Zhou, Auteur ; Nicholas E. Hansen, Auteur ; David J. Geb, Auteur Année de publication : 2012 Article en page(s) : pp. [111802/1-8] Note générale : Physique Langues : Anglais (eng) Mots-clés : Volume  averaging  theory  Closure  Heat  exchanger  Length  scale Index. décimale : 536 Chaleur. Thermodynamique Résumé : Modeling a fin-and-tube heat exchanger as porous media based on volume averaging theory (VAT), specific geometry can be accounted for in such a way that the details of the original structure can be replaced by their averaged counterparts, and the VAT based governing equations can be solved for a wide range of heat exchanger designs. To complete the VAT based model, proper closure is needed, which is related to a local friction factor and a heat transfer coefficient of a representative elementary volume. The present paper describes an effort to model a fin-and-tube heat exchanger based on VAT and obtain closure for the model. Experiment data and correlations for the air side characteristics of fin-and-tube heat exchangers from the published literature were collected and rescaled using the “porous media” length scale suggested by VAT. The results were surprisingly good, collapsing all the data onto a single curve for friction factor and Nusselt number, respectively. It was shown that using the porous media length scale is very beneficial in collapsing complex data yielding simple heat transfer and friction factor correlations and that by proper scaling, closure is a function of the porous media, which further generalizes macroscale porous media equations. The current work is a step closer to our final goal, which is to develop a universal fast running computational tool for multiple-parameter optimization of heat exchangers. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000133000011 [...] [article] Obtaining closure for fin-and-tube heat exchanger modeling based on volume averaging theory (VAT) [texte imprimé] / Feng Zhou, Auteur ; Nicholas E. Hansen, Auteur ; David J. Geb, Auteur . - 2012 . - pp. [111802/1-8]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 11 (Novembre 2011) . - pp. [111802/1-8] Mots-clés : Volume  averaging  theory  Closure  Heat  exchanger  Length  scale Index. décimale : 536 Chaleur. Thermodynamique Résumé : Modeling a fin-and-tube heat exchanger as porous media based on volume averaging theory (VAT), specific geometry can be accounted for in such a way that the details of the original structure can be replaced by their averaged counterparts, and the VAT based governing equations can be solved for a wide range of heat exchanger designs. To complete the VAT based model, proper closure is needed, which is related to a local friction factor and a heat transfer coefficient of a representative elementary volume. The present paper describes an effort to model a fin-and-tube heat exchanger based on VAT and obtain closure for the model. Experiment data and correlations for the air side characteristics of fin-and-tube heat exchangers from the published literature were collected and rescaled using the “porous media” length scale suggested by VAT. The results were surprisingly good, collapsing all the data onto a single curve for friction factor and Nusselt number, respectively. It was shown that using the porous media length scale is very beneficial in collapsing complex data yielding simple heat transfer and friction factor correlations and that by proper scaling, closure is a function of the porous media, which further generalizes macroscale porous media equations. The current work is a step closer to our final goal, which is to develop a universal fast running computational tool for multiple-parameter optimization of heat exchangers. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000133000011 [...]

Heat transfer and pressure drop correlations for square channels with V-shaped ribs at high Reynolds numbers / Nawaf Y. Alkhamis 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. [111901/1-8] Titre : Heat transfer and pressure drop correlations for square channels with V-shaped ribs at high Reynolds numbers Type de document : texte imprimé Auteurs : Nawaf Y. Alkhamis, Auteur ; Akhilesh P. Rallabandi, Auteur ; Je-Chin Han, Auteur Année de publication : 2012 Article en page(s) : pp. [111901/1-8] Note générale : Physique Langues : Anglais (eng) Mots-clés : Rib  turbulators  Internal  coolings  Gas  turbine  cooling  Heat  transfer  enhancement Index. décimale : 536 Chaleur. Thermodynamique Résumé : Heat transfer coefficients and friction factors are measured in a 45 deg V-shaped rib roughened square duct at high Reynolds numbers, pertaining to internal passages of land-based gas turbine engines. Reynolds numbers in this study range from 30,000 to 400,000, which is much higher than prior studies of V-shaped rib roughened channels. The dimensions of the channel are selected to ensure that the flow is in the incompressible regime. Blockage ratio e/D ranges from 0.1 to 0.18 and the spacing ratio P/e ranges from 5 to 10. Reported heat transfer coefficients are regionally averaged, measured by isothermal copper plates. Results show that the heat transfer enhancement decreases with increasing Reynolds number. The friction factor is found to be independent of the Reynolds number. The thermal performance decreases when the Reynolds number increases. 45 deg V-shaped ribs show a higher thermal performance than corresponding 45 deg angled ribs, consistent with the trend established in literature. Correlations for the Nusselt number and the friction factor as function of Re, e/D, and P/e are developed. Also developed are correlations for R and G (friction and heat transfer roughness functions, respectively) as a function of the roughness Reynolds number (e+). DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000133000011 [...] [article] Heat transfer and pressure drop correlations for square channels with V-shaped ribs at high Reynolds numbers [texte imprimé] / Nawaf Y. Alkhamis, Auteur ; Akhilesh P. Rallabandi, Auteur ; Je-Chin Han, Auteur . - 2012 . - pp. [111901/1-8]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 11 (Novembre 2011) . - pp. [111901/1-8] Mots-clés : Rib  turbulators  Internal  coolings  Gas  turbine  cooling  Heat  transfer  enhancement Index. décimale : 536 Chaleur. Thermodynamique Résumé : Heat transfer coefficients and friction factors are measured in a 45 deg V-shaped rib roughened square duct at high Reynolds numbers, pertaining to internal passages of land-based gas turbine engines. Reynolds numbers in this study range from 30,000 to 400,000, which is much higher than prior studies of V-shaped rib roughened channels. The dimensions of the channel are selected to ensure that the flow is in the incompressible regime. Blockage ratio e/D ranges from 0.1 to 0.18 and the spacing ratio P/e ranges from 5 to 10. Reported heat transfer coefficients are regionally averaged, measured by isothermal copper plates. Results show that the heat transfer enhancement decreases with increasing Reynolds number. The friction factor is found to be independent of the Reynolds number. The thermal performance decreases when the Reynolds number increases. 45 deg V-shaped ribs show a higher thermal performance than corresponding 45 deg angled ribs, consistent with the trend established in literature. Correlations for the Nusselt number and the friction factor as function of Re, e/D, and P/e are developed. Also developed are correlations for R and G (friction and heat transfer roughness functions, respectively) as a function of the roughness Reynolds number (e+). DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000133000011 [...]

Interpolation between the acoustic mismatch model and the diffuse mismatch model for the interface thermal conductance / M. Kazan 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. [112401/1-7] Titre : Interpolation between the acoustic mismatch model and the diffuse mismatch model for the interface thermal conductance : application to inN/GaN superlattice Type de document : texte imprimé Auteurs : M. Kazan, Auteur Année de publication : 2012 Article en page(s) : pp. [112401/1-7] Note générale : Physique Langues : Anglais (eng) Mots-clés : Phonons  Interface  thermal  conductance  Specularity  coefficient Index. décimale : 536 Chaleur. Thermodynamique Résumé : A model for the thermal conductance of an interface is developed. It interpolates between the widely used acoustic mismatch model and diffuse mismatch model and accounts for the phonon dispersion curves of the materials in contact as calculated from first principles technique. In the present model, the interface morphology is modeled by assuming for the height a Gaussian probability density and a two-dimensional tangential autocorrelation function. The temperature as well as the interface conditions weight the probabilities for the diffuse scattering and the specular behavior of the phonon at the interface. The features of the developed expression for the transmission probability are found to be in excellent agreement with experimental results. The model is applied to predict the phonon events at the interfaces in the InN/GaN superlattice as functions of interface conditions. The results showed that in order to increase the thermal conductance of the InN/GaN superlattice one should decrease the interfaces' tangential correlation and/or the interfaces' root mean square roughness. The proposed model can be an efficient tool for engineering high thermal conductivity optoelectronic systems or efficient thermoelectric devices. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000133000011 [...] [article] Interpolation between the acoustic mismatch model and the diffuse mismatch model for the interface thermal conductance : application to inN/GaN superlattice [texte imprimé] / M. Kazan, Auteur . - 2012 . - pp. [112401/1-7]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 11 (Novembre 2011) . - pp. [112401/1-7] Mots-clés : Phonons  Interface  thermal  conductance  Specularity  coefficient Index. décimale : 536 Chaleur. Thermodynamique Résumé : A model for the thermal conductance of an interface is developed. It interpolates between the widely used acoustic mismatch model and diffuse mismatch model and accounts for the phonon dispersion curves of the materials in contact as calculated from first principles technique. In the present model, the interface morphology is modeled by assuming for the height a Gaussian probability density and a two-dimensional tangential autocorrelation function. The temperature as well as the interface conditions weight the probabilities for the diffuse scattering and the specular behavior of the phonon at the interface. The features of the developed expression for the transmission probability are found to be in excellent agreement with experimental results. The model is applied to predict the phonon events at the interfaces in the InN/GaN superlattice as functions of interface conditions. The results showed that in order to increase the thermal conductance of the InN/GaN superlattice one should decrease the interfaces' tangential correlation and/or the interfaces' root mean square roughness. The proposed model can be an efficient tool for engineering high thermal conductivity optoelectronic systems or efficient thermoelectric devices. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000133000011 [...]

Modeling of thermally driven resonance at multiscales / P. Srinivasan 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. [112402/1-10] Titre : Modeling of thermally driven resonance at multiscales Type de document : texte imprimé Auteurs : P. Srinivasan, Auteur ; S. Mark Spearing, Auteur Année de publication : 2012 Article en page(s) : pp. [112402/1-10] Note générale : Physique Langues : Anglais (eng) Mots-clés : Thermal  wave  Resonance  Phonons  Multiscales Index. décimale : 536 Chaleur. Thermodynamique Résumé : Understanding the mechanisms of thermally driven resonance is a key for designing many engineering and physical systems especially at small scales. This paper focuses on the modeling aspects of such phenomena using the classical Fourier diffusion theory. Critical analysis revealed that the thermally induced resonant excitation is characterized by the generation of multiple wave trains with a constant phase shift as opposed to the single standing wave generated in a mechanically driven resonant response. The hypothesis proposed herein, underpin a broad range of scientific and technological developments and the analytical treatment enables design of thermally driven resonant systems with improved performance. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000133000011 [...] [article] Modeling of thermally driven resonance at multiscales [texte imprimé] / P. Srinivasan, Auteur ; S. Mark Spearing, Auteur . - 2012 . - pp. [112402/1-10]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 11 (Novembre 2011) . - pp. [112402/1-10] Mots-clés : Thermal  wave  Resonance  Phonons  Multiscales Index. décimale : 536 Chaleur. Thermodynamique Résumé : Understanding the mechanisms of thermally driven resonance is a key for designing many engineering and physical systems especially at small scales. This paper focuses on the modeling aspects of such phenomena using the classical Fourier diffusion theory. Critical analysis revealed that the thermally induced resonant excitation is characterized by the generation of multiple wave trains with a constant phase shift as opposed to the single standing wave generated in a mechanically driven resonant response. The hypothesis proposed herein, underpin a broad range of scientific and technological developments and the analytical treatment enables design of thermally driven resonant systems with improved performance. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000133000011 [...]

Scaling analysis of the unsteady natural convection boundary layer adjacent to an inclined plate for Pr > 1 following instantaneous heating / Suvash C. Saha 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. [112501/1-9] Titre : Scaling analysis of the unsteady natural convection boundary layer adjacent to an inclined plate for Pr > 1 following instantaneous heating Type de document : texte imprimé Auteurs : Suvash C. Saha, Auteur ; Feng Xu, Auteur ; Md Mamun Molla, Auteur Année de publication : 2012 Article en page(s) : pp. [112501/1-9] Note générale : Physique Langues : Anglais (eng) Mots-clés : Boundary  layers  Flow  simulation  Integral  equations  Natural  convection  Navier-Stokes  equations  Numerical  analysis Index. décimale : 536 Chaleur. Thermodynamique Résumé : The unsteady natural convection boundary layer adjacent to an instantaneously heated inclined plate is investigated using an improved scaling analysis and direct numerical simulations. The development of the unsteady natural convection boundary layer following instantaneous heating may be classified into three distinct stages including a start-up stage, a transitional stage, and a steady state stage, which can be clearly identified in the analytical and numerical results. Major scaling relations of the velocity and thicknesses and the flow development time of the natural convection boundary layer are obtained using triple-layer integral solutions and verified by direct numerical simulations over a wide range of flow parameters. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000133000011 [...] [article] Scaling analysis of the unsteady natural convection boundary layer adjacent to an inclined plate for Pr > 1 following instantaneous heating [texte imprimé] / Suvash C. Saha, Auteur ; Feng Xu, Auteur ; Md Mamun Molla, Auteur . - 2012 . - pp. [112501/1-9]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 11 (Novembre 2011) . - pp. [112501/1-9] Mots-clés : Boundary  layers  Flow  simulation  Integral  equations  Natural  convection  Navier-Stokes  equations  Numerical  analysis Index. décimale : 536 Chaleur. Thermodynamique Résumé : The unsteady natural convection boundary layer adjacent to an instantaneously heated inclined plate is investigated using an improved scaling analysis and direct numerical simulations. The development of the unsteady natural convection boundary layer following instantaneous heating may be classified into three distinct stages including a start-up stage, a transitional stage, and a steady state stage, which can be clearly identified in the analytical and numerical results. Major scaling relations of the velocity and thicknesses and the flow development time of the natural convection boundary layer are obtained using triple-layer integral solutions and verified by direct numerical simulations over a wide range of flow parameters. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000133000011 [...]

Energy conservative dissipative particle dynamics simulation of natural convection in liquids / Eiyad Abu-Nada 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. [112501/1-12] Titre : Energy conservative dissipative particle dynamics simulation of natural convection in liquids Type de document : texte imprimé Auteurs : Eiyad Abu-Nada, Auteur Année de publication : 2012 Article en page(s) : pp. [112501/1-12] Note générale : Physique Langues : Anglais (eng) Mots-clés : Dissipative  particle  dynamics  eDPD  Natural  convection  Rayleigh-Bénard  convection  Prandtl  number Index. décimale : 536 Chaleur. Thermodynamique Résumé : Dissipative particle dynamics with energy conservation (eDPD) was used to study natural convection in liquid domain over a wide range of Rayleigh Numbers. The problem selected for this study was the Rayleigh–Bénard convection problem. The Prandtl number used resembles water where the Prandtl number is set to Pr = 6.57. The eDPD results were compared to the finite volume solutions, and it was found that the eDPD method calculates the temperature and flow fields throughout the natural convection domains correctly. The eDPD model recovered the basic features of natural convection, such as development of plumes, development of thermal boundary layers, and development of natural convection circulation cells (rolls). The eDPD results were presented by means of temperature isotherms, streamlines, velocity contours, velocity vector plots, and temperature and velocity profiles. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000133000011 [...] [article] Energy conservative dissipative particle dynamics simulation of natural convection in liquids [texte imprimé] / Eiyad Abu-Nada, Auteur . - 2012 . - pp. [112501/1-12]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 11 (Novembre 2011) . - pp. [112501/1-12] Mots-clés : Dissipative  particle  dynamics  eDPD  Natural  convection  Rayleigh-Bénard  convection  Prandtl  number Index. décimale : 536 Chaleur. Thermodynamique Résumé : Dissipative particle dynamics with energy conservation (eDPD) was used to study natural convection in liquid domain over a wide range of Rayleigh Numbers. The problem selected for this study was the Rayleigh–Bénard convection problem. The Prandtl number used resembles water where the Prandtl number is set to Pr = 6.57. The eDPD results were compared to the finite volume solutions, and it was found that the eDPD method calculates the temperature and flow fields throughout the natural convection domains correctly. The eDPD model recovered the basic features of natural convection, such as development of plumes, development of thermal boundary layers, and development of natural convection circulation cells (rolls). The eDPD results were presented by means of temperature isotherms, streamlines, velocity contours, velocity vector plots, and temperature and velocity profiles. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000133000011 [...]

Restrictions on the validity of the thermal conditions at the porous-fluid interface / Kun Yang 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. [112601/1-12] Titre : Restrictions on the validity of the thermal conditions at the porous-fluid interface : an exact solution Type de document : texte imprimé Auteurs : Kun Yang, Auteur ; Kambiz Vafai, Auteur Année de publication : 2012 Article en page(s) : pp. [112601/1-12] Note générale : Physique Langues : Anglais (eng) Mots-clés : Thermal  condition  Porous-fluis  interface  Local  thermal  nonequilibrium Index. décimale : 536 Chaleur. Thermodynamique Résumé : Thermal conditions at the porous-fluid interface under local thermal nonequilibrium (LTNE) conditions are analyzed in this work. Exact solutions are derived for both the fluid and solid temperature distributions for five of the most fundamental forms of thermal conditions at the interface between a porous medium and a fluid under LTNE conditions and the relationships between these solutions are discussed. This work concentrates on restrictions, based on the physical attributes of the system, which must be placed for validity of the thermal interface conditions. The analytical results clearly point out the range of validity for each model for the first time in the literature. Furthermore, the range of validity of the local thermal equilibrium (LTE) condition is discussed based on the introduction of a critical parameter. The Nusselt number for the fluid at the wall of a channel that contains the fluid and porous medium is also obtained. The effects of the pertinent parameters such as Darcy number, Biot number, Bi, Interface Biot number, Biint, and fluid to solid thermal conductivity ratio are discussed. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000133000011 [...] [article] Restrictions on the validity of the thermal conditions at the porous-fluid interface : an exact solution [texte imprimé] / Kun Yang, Auteur ; Kambiz Vafai, Auteur . - 2012 . - pp. [112601/1-12]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 11 (Novembre 2011) . - pp. [112601/1-12] Mots-clés : Thermal  condition  Porous-fluis  interface  Local  thermal  nonequilibrium Index. décimale : 536 Chaleur. Thermodynamique Résumé : Thermal conditions at the porous-fluid interface under local thermal nonequilibrium (LTNE) conditions are analyzed in this work. Exact solutions are derived for both the fluid and solid temperature distributions for five of the most fundamental forms of thermal conditions at the interface between a porous medium and a fluid under LTNE conditions and the relationships between these solutions are discussed. This work concentrates on restrictions, based on the physical attributes of the system, which must be placed for validity of the thermal interface conditions. The analytical results clearly point out the range of validity for each model for the first time in the literature. Furthermore, the range of validity of the local thermal equilibrium (LTE) condition is discussed based on the introduction of a critical parameter. The Nusselt number for the fluid at the wall of a channel that contains the fluid and porous medium is also obtained. The effects of the pertinent parameters such as Darcy number, Biot number, Bi, Interface Biot number, Biint, and fluid to solid thermal conductivity ratio are discussed. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000133000011 [...]

Exact solutions for a thermal nonequilibrium model of fluid saturated porous media based on an effective porosity / F. Kuwahara 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. [112602/1-9] Titre : Exact solutions for a thermal nonequilibrium model of fluid saturated porous media based on an effective porosity Type de document : texte imprimé Auteurs : F. Kuwahara, Auteur ; C. Yang, Auteur ; K. Ando, Auteur Année de publication : 2012 Article en page(s) : pp. [112602/1-9] Note générale : Physique Langues : Anglais (eng) Mots-clés : Porous  media  Thermal  nonequilibrium  Aluminum  Metal  foam  Conductivity Index. décimale : 536 Chaleur. Thermodynamique Résumé : An effective porosity concept has been introduced to account for the effects of tortuosity and thermal dispersion on the individual effective thermal conductivities of the solid and fluid phases in a fluid-saturated porous medium. Using this effective porosity concept, a thermal nonequilibrium model has been proposed to attack locally thermal nonequilibrium problems associated with convection within a fluid-saturated porous medium. Exact solutions are obtained, assuming a plug flow, for the two cases of thermally fully developed convective flows through a channel, namely, the case of isothermal hot and cold walls and the case of constant heat flux walls. These exact solutions for the cases of metal foam and air combination reveal that the local thermal equilibrium assumption may hold for the case of isothermal hot and cold walls, but may fail for the case of constant heat flux walls. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000133000011 [...] [article] Exact solutions for a thermal nonequilibrium model of fluid saturated porous media based on an effective porosity [texte imprimé] / F. Kuwahara, Auteur ; C. Yang, Auteur ; K. Ando, Auteur . - 2012 . - pp. [112602/1-9]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 11 (Novembre 2011) . - pp. [112602/1-9] Mots-clés : Porous  media  Thermal  nonequilibrium  Aluminum  Metal  foam  Conductivity Index. décimale : 536 Chaleur. Thermodynamique Résumé : An effective porosity concept has been introduced to account for the effects of tortuosity and thermal dispersion on the individual effective thermal conductivities of the solid and fluid phases in a fluid-saturated porous medium. Using this effective porosity concept, a thermal nonequilibrium model has been proposed to attack locally thermal nonequilibrium problems associated with convection within a fluid-saturated porous medium. Exact solutions are obtained, assuming a plug flow, for the two cases of thermally fully developed convective flows through a channel, namely, the case of isothermal hot and cold walls and the case of constant heat flux walls. These exact solutions for the cases of metal foam and air combination reveal that the local thermal equilibrium assumption may hold for the case of isothermal hot and cold walls, but may fail for the case of constant heat flux walls. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000133000011 [...]

Fluid flow and heat transfer within a single horizontal fracture in an enhanced geothermal system / Rosemarie Mohais 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. [112603/1-8] Titre : Fluid flow and heat transfer within a single horizontal fracture in an enhanced geothermal system Type de document : texte imprimé Auteurs : Rosemarie Mohais, Auteur ; Chaoshui Xu, Auteur ; Peter Dowd, Auteur Année de publication : 2012 Article en page(s) : pp. [112603/1-8] Note générale : Physique Langues : Anglais (eng) Mots-clés : Enhanced  geothermal  systems  Channel  Fracture  Permeable  walls Index. décimale : 536 Chaleur. Thermodynamique Résumé : We present an analysis of fluid flow and heat transfer through a single horizontal channel with permeable walls which are at different temperatures. The problem is set in the context of hot dry rock geothermal energy extraction where water, introduced through an injection well, passes through a horizontal fracture by which transfer of heat is facilitated through advection of the fluid flowing toward the recovery well. We consider the walls of the fracture to have properties of a permeable medium and we study the effect of slip boundary conditions on velocity and temperature profiles for low Reynolds number (< 7) based on a similarity solution and perturbation expansion. We show that the velocity and heat transfer profiles are altered with the channel width, the permeability and a slip coefficient , which is a dimensionless constant related to the inherent properties of the channel. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000133000011 [...] [article] Fluid flow and heat transfer within a single horizontal fracture in an enhanced geothermal system [texte imprimé] / Rosemarie Mohais, Auteur ; Chaoshui Xu, Auteur ; Peter Dowd, Auteur . - 2012 . - pp. [112603/1-8]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 11 (Novembre 2011) . - pp. [112603/1-8] Mots-clés : Enhanced  geothermal  systems  Channel  Fracture  Permeable  walls Index. décimale : 536 Chaleur. Thermodynamique Résumé : We present an analysis of fluid flow and heat transfer through a single horizontal channel with permeable walls which are at different temperatures. The problem is set in the context of hot dry rock geothermal energy extraction where water, introduced through an injection well, passes through a horizontal fracture by which transfer of heat is facilitated through advection of the fluid flowing toward the recovery well. We consider the walls of the fracture to have properties of a permeable medium and we study the effect of slip boundary conditions on velocity and temperature profiles for low Reynolds number (< 7) based on a similarity solution and perturbation expansion. We show that the velocity and heat transfer profiles are altered with the channel width, the permeability and a slip coefficient , which is a dimensionless constant related to the inherent properties of the channel. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000133000011 [...]

Extension of the FLASH method to semitransparent polymer foams / R. Coquard 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. [112604/1-8] Titre : Extension of the FLASH method to semitransparent polymer foams Type de document : texte imprimé Auteurs : R. Coquard, Auteur ; J. Randrianalisoa, Auteur ; S. Lallich, Auteur Année de publication : 2012 Article en page(s) : pp. [112604/1-8] Note générale : Physique Langues : Anglais (eng) Mots-clés : Heat  conduction  Heat  transfer  Least  squares  approximations  Photothermal  effects  Polymer  foams  Thermal  conductivity  measurement Index. décimale : 536 Chaleur. Thermodynamique Résumé : The classical photo-thermal FLASH method is a very practicable method for measurement of the conductive properties of solid materials due to its simplicity, rapidity, and to the limited size of the samples required. It has been applied successfully to a wide variety of materials. However, it is theoretically restricted to purely conductive media. Notably, it could, strictly speaking, not be used to measure the equivalent conductivity of low-density thermal insulators since a significant part of the heat transfer is due to the propagation of thermal radiation. This constitutes a major drawback of the method. Therefore, the present study investigates the possibility to extend the method to this kind of materials by estimating the errors made on the equivalent conductivity when the classical FLASH method is used. To this aim, FLASH experiments have been conducted at different temperatures on several low-density polymer foams whose radiative properties have been estimated from spectrometric measurements. By applying a least-square fit-method associated with a numerical simulation of the 1D coupled heat transfer, we managed to identify the phonic conductivities of the samples and to compute their equivalent conductivities. These values have been compared with the thermal conductivities obtained from classical FLASH method, i.e., assuming that the thermal transfer occurs only by heat conduction. It appears that the discrepancies between the conductivities stemming from the classical FLASH method and the equivalent conductivities computed are quite negligible at ambient temperature even for foams with very low densities. This demonstrates the applicability of the classical FLASH method to this type of materials for building applications. This conclusion is likely to interest foam manufacturers in view of reducing the time required for an accurate measurement of the insulating performances. On the other hand, at elevated temperatures, the errors become significant so that the method could not be considered satisfactory. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000133000011 [...] [article] Extension of the FLASH method to semitransparent polymer foams [texte imprimé] / R. Coquard, Auteur ; J. Randrianalisoa, Auteur ; S. Lallich, Auteur . - 2012 . - pp. [112604/1-8]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 11 (Novembre 2011) . - pp. [112604/1-8] Mots-clés : Heat  conduction  Heat  transfer  Least  squares  approximations  Photothermal  effects  Polymer  foams  Thermal  conductivity  measurement Index. décimale : 536 Chaleur. Thermodynamique Résumé : The classical photo-thermal FLASH method is a very practicable method for measurement of the conductive properties of solid materials due to its simplicity, rapidity, and to the limited size of the samples required. It has been applied successfully to a wide variety of materials. However, it is theoretically restricted to purely conductive media. Notably, it could, strictly speaking, not be used to measure the equivalent conductivity of low-density thermal insulators since a significant part of the heat transfer is due to the propagation of thermal radiation. This constitutes a major drawback of the method. Therefore, the present study investigates the possibility to extend the method to this kind of materials by estimating the errors made on the equivalent conductivity when the classical FLASH method is used. To this aim, FLASH experiments have been conducted at different temperatures on several low-density polymer foams whose radiative properties have been estimated from spectrometric measurements. By applying a least-square fit-method associated with a numerical simulation of the 1D coupled heat transfer, we managed to identify the phonic conductivities of the samples and to compute their equivalent conductivities. These values have been compared with the thermal conductivities obtained from classical FLASH method, i.e., assuming that the thermal transfer occurs only by heat conduction. It appears that the discrepancies between the conductivities stemming from the classical FLASH method and the equivalent conductivities computed are quite negligible at ambient temperature even for foams with very low densities. This demonstrates the applicability of the classical FLASH method to this type of materials for building applications. This conclusion is likely to interest foam manufacturers in view of reducing the time required for an accurate measurement of the insulating performances. On the other hand, at elevated temperatures, the errors become significant so that the method could not be considered satisfactory. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000133000011 [...]

Numerical simulation of hydrogen–air boundary layer flows augmented by catalytic surface reactions / M. M. Abou-Ellail 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. [114501/1-12] Titre : Numerical simulation of hydrogen–air boundary layer flows augmented by catalytic surface reactions Type de document : texte imprimé Auteurs : M. M. Abou-Ellail, Auteur ; T. W. Tong, Auteur ; Y. Li, Auteur Année de publication : 2012 Article en page(s) : pp. [114501/1-12] Note générale : Physique Langues : Anglais (eng) Mots-clés : Cataytic  surface  reaction  Hydrogen/air  Numerical  methods Index. décimale : 536 Chaleur. Thermodynamique Résumé : Catalytic combustion of hydrogen–air boundary layers involves the adsorption of hydrogen and oxygen into a platinum coated surface, chemical reactions of the adsorbed species, and the desorption of the resulting products. Re-adsorption of some produced gases is also possible. The catalytic reactions can be beneficial in porous burners and catalytic reactors that use low equivalence ratios. In this case, the porous burner flame can be stabilized at low temperatures to prevent any substantial gas emissions, such as nitrogen oxides. The present paper is concerned with the numerical computation of heat transfer and chemical reactions in hydrogen–air mixture boundary layers that flow over platinum coated hot plates and inside rectangular channels. Chemical reactions are included in the gas-phase as well as on the solid platinum surface. In the gas-phase, eight species are involved in 26 elementary reactions. On the platinum hot surface, additional surface species are included that are involved in 16 additional surface chemical reactions. The platinum surface temperature distribution is prespecified, while the properties of the reacting flow are computed. The flow configurations investigated in the present paper are those of a flat plate boundary layer and a rectangular channel reacting flow. Finite-volume equations are obtained by formal integration over control volumes surrounding each grid node. Hybrid differencing is used to ensure that the finite-difference coefficients are always positive or equal to zero to reflect the real effect of neighboring nodes on a typical central node. The finite-volume equations are solved iteratively for the reacting gas flow properties. On the platinum surface, surface species balance equations, under steady-state conditions, are solved numerically. A nonuniform computational grid is used, concentrating most of the nodes in the boundary sub-layer adjoining the catalytic surface. For the flat plate boundary layer flow, the computed OH concentration is compared with experimental and numerical data of similar geometry. The obtained agreement is fairly good, with differences observed for the location of the peak value of OH. Surface temperature of 1170 K caused fast reactions on the catalytic surface in a very small part at the leading edge of the catalytic flat plate. The flat plate computational results for heat and mass transfer and chemical surface reactions at the gas-surface interface are correlated by nondimensional relations. The channel flow computational results are also compared with recent detailed experimental data for similar geometry. In this case, the catalytic surface temperature profile along the x-axis was measured accurately and is used in the present work as the boundary condition for the gas-phase energy equation. The present numerical results for the gas temperature, water vapor mole fraction, and hydrogen mole fraction are compared with the corresponding experimental data. In general, the agreement is very good especially in the first 105 mm. However, some differences are observed in the vicinity of the exit section of the rectangular channel. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000133000011 [...] [article] Numerical simulation of hydrogen–air boundary layer flows augmented by catalytic surface reactions [texte imprimé] / M. M. Abou-Ellail, Auteur ; T. W. Tong, Auteur ; Y. Li, Auteur . - 2012 . - pp. [114501/1-12]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 11 (Novembre 2011) . - pp. [114501/1-12] Mots-clés : Cataytic  surface  reaction  Hydrogen/air  Numerical  methods Index. décimale : 536 Chaleur. Thermodynamique Résumé : Catalytic combustion of hydrogen–air boundary layers involves the adsorption of hydrogen and oxygen into a platinum coated surface, chemical reactions of the adsorbed species, and the desorption of the resulting products. Re-adsorption of some produced gases is also possible. The catalytic reactions can be beneficial in porous burners and catalytic reactors that use low equivalence ratios. In this case, the porous burner flame can be stabilized at low temperatures to prevent any substantial gas emissions, such as nitrogen oxides. The present paper is concerned with the numerical computation of heat transfer and chemical reactions in hydrogen–air mixture boundary layers that flow over platinum coated hot plates and inside rectangular channels. Chemical reactions are included in the gas-phase as well as on the solid platinum surface. In the gas-phase, eight species are involved in 26 elementary reactions. On the platinum hot surface, additional surface species are included that are involved in 16 additional surface chemical reactions. The platinum surface temperature distribution is prespecified, while the properties of the reacting flow are computed. The flow configurations investigated in the present paper are those of a flat plate boundary layer and a rectangular channel reacting flow. Finite-volume equations are obtained by formal integration over control volumes surrounding each grid node. Hybrid differencing is used to ensure that the finite-difference coefficients are always positive or equal to zero to reflect the real effect of neighboring nodes on a typical central node. The finite-volume equations are solved iteratively for the reacting gas flow properties. On the platinum surface, surface species balance equations, under steady-state conditions, are solved numerically. A nonuniform computational grid is used, concentrating most of the nodes in the boundary sub-layer adjoining the catalytic surface. For the flat plate boundary layer flow, the computed OH concentration is compared with experimental and numerical data of similar geometry. The obtained agreement is fairly good, with differences observed for the location of the peak value of OH. Surface temperature of 1170 K caused fast reactions on the catalytic surface in a very small part at the leading edge of the catalytic flat plate. The flat plate computational results for heat and mass transfer and chemical surface reactions at the gas-surface interface are correlated by nondimensional relations. The channel flow computational results are also compared with recent detailed experimental data for similar geometry. In this case, the catalytic surface temperature profile along the x-axis was measured accurately and is used in the present work as the boundary condition for the gas-phase energy equation. The present numerical results for the gas temperature, water vapor mole fraction, and hydrogen mole fraction are compared with the corresponding experimental data. In general, the agreement is very good especially in the first 105 mm. However, some differences are observed in the vicinity of the exit section of the rectangular channel. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000133000011 [...]

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 [...]

Exemplaires

Bibliothèque Ecole Nationale Polytechnique d'Alger

Accueil

Se connecter

Météo

Adresse