Dépouillements

Heat transfer between colliding surfaces and particles / Like Li in Journal of heat transfer, Vol. 134 N° 1 (Janvier 2012) 

Public ISBD [article]  in Journal of heat transfer > Vol. 134 N° 1 (Janvier 2012) . - 12 p. Titre : Heat transfer between colliding surfaces and particles Type de document : texte imprimé Auteurs : Like Li, Auteur ; Renwei Mei, Auteur ; James F. Klausner, Auteur Année de publication : 2012 Article en page(s) : 12 p. Note générale : Heat transfer Langues : Anglais (eng) Mots-clés : Finite  difference  methods  Flow  simulation  Fractals  Heat  transfer  Thermal  conductivity  Thermal  diffusion  Two-phase  flow Index. décimale : 536 Chaleur. Thermodynamique Résumé : Collisional heat transfer between two contacting curved surfaces is investigated computationally using a finite difference method and analytically using various asymptotic methods. Transformed coordinates that scale with the contact radius and the diffusion length are used for the computations. Hertzian contact theory of elasticity is used to characterize the contact area as a function of time. For an axisymmetric contact area, a two-dimensional self-similar solution for the thermal field during the initial period of contact is obtained, and it serves as an initial condition for the heat transfer simulation throughout the entire duration of collision. A two-dimensional asymptotic heat transfer result is obtained for small Fourier number. For finite Fourier numbers, local analytical solutions are presented to elucidate the nature of the singularity of the thermal field and heat flux near the contact point. From the computationally determined heat transfer during the collision, a closed-form formula is developed to predict the heat transfer as a function of the Fourier number, the thermal diffusivity ratio, and the thermal conductivity ratio of the impacting particles. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000134000001 [...] [article] Heat transfer between colliding surfaces and particles [texte imprimé] / Like Li, Auteur ; Renwei Mei, Auteur ; James F. Klausner, Auteur . - 2012 . - 12 p. Heat transfer Langues : Anglais (eng) in Journal of heat transfer > Vol. 134 N° 1 (Janvier 2012) . - 12 p. Mots-clés : Finite  difference  methods  Flow  simulation  Fractals  Heat  transfer  Thermal  conductivity  Thermal  diffusion  Two-phase  flow Index. décimale : 536 Chaleur. Thermodynamique Résumé : Collisional heat transfer between two contacting curved surfaces is investigated computationally using a finite difference method and analytically using various asymptotic methods. Transformed coordinates that scale with the contact radius and the diffusion length are used for the computations. Hertzian contact theory of elasticity is used to characterize the contact area as a function of time. For an axisymmetric contact area, a two-dimensional self-similar solution for the thermal field during the initial period of contact is obtained, and it serves as an initial condition for the heat transfer simulation throughout the entire duration of collision. A two-dimensional asymptotic heat transfer result is obtained for small Fourier number. For finite Fourier numbers, local analytical solutions are presented to elucidate the nature of the singularity of the thermal field and heat flux near the contact point. From the computationally determined heat transfer during the collision, a closed-form formula is developed to predict the heat transfer as a function of the Fourier number, the thermal diffusivity ratio, and the thermal conductivity ratio of the impacting particles. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000134000001 [...]

Boundary control of temperature distribution in a spherical shell with spatially varying parameters / Hossein Rastgoftar in Journal of heat transfer, Vol. 134 N° 1 (Janvier 2012) 

Public ISBD [article]  in Journal of heat transfer > Vol. 134 N° 1 (Janvier 2012) . - 05 p. Titre : Boundary control of temperature distribution in a spherical shell with spatially varying parameters Type de document : texte imprimé Auteurs : Hossein Rastgoftar, Auteur ; Mohammad Eghtesad, Auteur ; Alireza Khayatian, Auteur Année de publication : 2012 Article en page(s) : 05 p. Note générale : Heat transfer Langues : Anglais (eng) Mots-clés : Heat  conduction  Lyapunov  methods  Numerical  analysis  Partial  differential  equations  Specific  heat  Temperature  distribution  Thermal  conductivity Index. décimale : 536 Chaleur. Thermodynamique Résumé : This paper presents a solution to the control (stabilization) problem of temperature distribution in spherical shells with spatially varying properties. The desired temperature distribution satisfies the steady-state heat conduction equation. For the spherical shell under consideration, it is assumed that material properties such as thermal conductivity, density, and specific heat capacity may vary in radial, polar, and azimuthal directions of the spherical shell; the governing heat conduction equation of the shell is a second-order partial differential equation. Using Lyapunov's theorem, it is shown how to obtain boundary heat flux required for producing a desired steady-state distribution of the temperature. Finally, numerical simulation is provided to verify the effectiveness of the proposed method such that by applying the boundary transient heat flux, in-domain distributed temperature converges to its desired steady-state temperature. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000134000001 [...] [article] Boundary control of temperature distribution in a spherical shell with spatially varying parameters [texte imprimé] / Hossein Rastgoftar, Auteur ; Mohammad Eghtesad, Auteur ; Alireza Khayatian, Auteur . - 2012 . - 05 p. Heat transfer Langues : Anglais (eng) in Journal of heat transfer > Vol. 134 N° 1 (Janvier 2012) . - 05 p. Mots-clés : Heat  conduction  Lyapunov  methods  Numerical  analysis  Partial  differential  equations  Specific  heat  Temperature  distribution  Thermal  conductivity Index. décimale : 536 Chaleur. Thermodynamique Résumé : This paper presents a solution to the control (stabilization) problem of temperature distribution in spherical shells with spatially varying properties. The desired temperature distribution satisfies the steady-state heat conduction equation. For the spherical shell under consideration, it is assumed that material properties such as thermal conductivity, density, and specific heat capacity may vary in radial, polar, and azimuthal directions of the spherical shell; the governing heat conduction equation of the shell is a second-order partial differential equation. Using Lyapunov's theorem, it is shown how to obtain boundary heat flux required for producing a desired steady-state distribution of the temperature. Finally, numerical simulation is provided to verify the effectiveness of the proposed method such that by applying the boundary transient heat flux, in-domain distributed temperature converges to its desired steady-state temperature. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000134000001 [...]

Design optimization of electrical power contact using finite element method / Amine Beloufa in Journal of heat transfer, Vol. 134 N° 1 (Janvier 2012) 

Public ISBD [article]  in Journal of heat transfer > Vol. 134 N° 1 (Janvier 2012) . - 15 p. Titre : Design optimization of electrical power contact using finite element method Type de document : texte imprimé Auteurs : Amine Beloufa, Auteur Année de publication : 2012 Article en page(s) : 15 p. Note générale : Heat transfer Langues : Anglais (eng) Mots-clés : Automotive  components  Automotive  electronics  Contact  resistance  Design  engineering  Electric  connectors  Electrical  contacts  Finite  element  analysis  Loading  Mechanical  strength  Optimisation  Stress  analysis Index. décimale : 536 Chaleur. Thermodynamique Résumé : Automotive connectors in modern car generations are submitted to high current; this can cause many problems and requires the minimization of their electrical contact resistances. The new major contribution of this work is the optimization by finite element method of contact resistance, contact temperature, design, and mechanical stress of sphere/plane contact samples. These contact samples were made with recent high-copper alloys and were subjected to indentation loading. Experimental tests were carried out in order to validate the developed numerical model and to select the material which presents a low contact temperature and contact resistance. Another model with multipoint contacts was developed in order to minimize electrical contact resistance and contact temperature. Shape optimization results indicate that the volume of contact samples was reduced by 12%. The results show also for the model with multipoint contacts that the contact resistance was reduced by 41%, contact temperature by 22% and maximum Von Mises stress by 49%. These several gains are more interesting for the connector designers. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000134000001 [...] [article] Design optimization of electrical power contact using finite element method [texte imprimé] / Amine Beloufa, Auteur . - 2012 . - 15 p. Heat transfer Langues : Anglais (eng) in Journal of heat transfer > Vol. 134 N° 1 (Janvier 2012) . - 15 p. Mots-clés : Automotive  components  Automotive  electronics  Contact  resistance  Design  engineering  Electric  connectors  Electrical  contacts  Finite  element  analysis  Loading  Mechanical  strength  Optimisation  Stress  analysis Index. décimale : 536 Chaleur. Thermodynamique Résumé : Automotive connectors in modern car generations are submitted to high current; this can cause many problems and requires the minimization of their electrical contact resistances. The new major contribution of this work is the optimization by finite element method of contact resistance, contact temperature, design, and mechanical stress of sphere/plane contact samples. These contact samples were made with recent high-copper alloys and were subjected to indentation loading. Experimental tests were carried out in order to validate the developed numerical model and to select the material which presents a low contact temperature and contact resistance. Another model with multipoint contacts was developed in order to minimize electrical contact resistance and contact temperature. Shape optimization results indicate that the volume of contact samples was reduced by 12%. The results show also for the model with multipoint contacts that the contact resistance was reduced by 41%, contact temperature by 22% and maximum Von Mises stress by 49%. These several gains are more interesting for the connector designers. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000134000001 [...]

Simulation of mist film cooling on rotating gas turbine blades / T. S. Dhanasekaran in Journal of heat transfer, Vol. 134 N° 1 (Janvier 2012) 

Public ISBD [article]  in Journal of heat transfer > Vol. 134 N° 1 (Janvier 2012) . - 11 p. Titre : Simulation of mist film cooling on rotating gas turbine blades Type de document : texte imprimé Auteurs : T. S. Dhanasekaran, Auteur ; Ting Wang, Auteur Année de publication : 2012 Article en page(s) : 11 p. Note générale : Heat transfer Langues : Anglais (eng) Mots-clés : Blades  Computational  fluid  dynamics  Convection  Cooling  Drops  Flow  simulation  Flue  gases  Gas  turbines  Jets  Liquid  films  Rotational  flow  Thin  films  Two-phase  flow Index. décimale : 536 Chaleur. Thermodynamique Résumé : Film cooling techniques have been successfully applied to gas turbine blades to protect them from the hot flue gas. However, a continuous demand of increasing the turbine inlet temperature to raise the efficiency of the turbine requires continuous improvement in film cooling effectiveness. The concept of injecting mist (tiny water droplets) into the cooling fluid has been proven under laboratory conditions to significantly augment adiabatic cooling effectiveness by up to 50%–800% in convective heat transfer and impingement cooling. The similar concept of injecting mist into air film cooling has not been proven in the laboratory, but computational simulations have been performed on stationary turbine blades. As a continuation of previous research, this paper extends the mist film cooling scheme to the rotating turbine blade. For the convenience of understanding the effect of rotation, the simulation is first conducted with a single pair of cooling holes located near the leading edge at either side of the blade. Then, a row of multiple-hole film cooling jets is put in place under both stationary and rotating conditions. Both the laboratory (baseline) and elevated gas turbine conditions are simulated and compared. Elevated conditions refer to a high temperature and pressure closer to actual gas turbine working conditions. The effects of various parameters including mist concentration, water droplet diameter, droplet wall boundary condition, blowing ratio, and rotational speed are investigated. The results showed that the effect of rotation on droplets under laboratory conditions is minimal. The computational fluid dynamics (CFD) model employed is the discrete phase model (DPM) including both wall film and droplet reflect conditions. The results showed that the droplet-wall interaction is stronger on the pressure side than on the suction side, resulting in a higher mist cooling enhancement on the pressure side. The average rates of mist cooling enhancement of about 15% and 35% were achieved under laboratory and elevated conditions, respectively. This translates to a significant blade surface temperature reduction of 100–125 K with 10% mist injection at elevated conditions. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000134000001 [...] [article] Simulation of mist film cooling on rotating gas turbine blades [texte imprimé] / T. S. Dhanasekaran, Auteur ; Ting Wang, Auteur . - 2012 . - 11 p. Heat transfer Langues : Anglais (eng) in Journal of heat transfer > Vol. 134 N° 1 (Janvier 2012) . - 11 p. Mots-clés : Blades  Computational  fluid  dynamics  Convection  Cooling  Drops  Flow  simulation  Flue  gases  Gas  turbines  Jets  Liquid  films  Rotational  flow  Thin  films  Two-phase  flow Index. décimale : 536 Chaleur. Thermodynamique Résumé : Film cooling techniques have been successfully applied to gas turbine blades to protect them from the hot flue gas. However, a continuous demand of increasing the turbine inlet temperature to raise the efficiency of the turbine requires continuous improvement in film cooling effectiveness. The concept of injecting mist (tiny water droplets) into the cooling fluid has been proven under laboratory conditions to significantly augment adiabatic cooling effectiveness by up to 50%–800% in convective heat transfer and impingement cooling. The similar concept of injecting mist into air film cooling has not been proven in the laboratory, but computational simulations have been performed on stationary turbine blades. As a continuation of previous research, this paper extends the mist film cooling scheme to the rotating turbine blade. For the convenience of understanding the effect of rotation, the simulation is first conducted with a single pair of cooling holes located near the leading edge at either side of the blade. Then, a row of multiple-hole film cooling jets is put in place under both stationary and rotating conditions. Both the laboratory (baseline) and elevated gas turbine conditions are simulated and compared. Elevated conditions refer to a high temperature and pressure closer to actual gas turbine working conditions. The effects of various parameters including mist concentration, water droplet diameter, droplet wall boundary condition, blowing ratio, and rotational speed are investigated. The results showed that the effect of rotation on droplets under laboratory conditions is minimal. The computational fluid dynamics (CFD) model employed is the discrete phase model (DPM) including both wall film and droplet reflect conditions. The results showed that the droplet-wall interaction is stronger on the pressure side than on the suction side, resulting in a higher mist cooling enhancement on the pressure side. The average rates of mist cooling enhancement of about 15% and 35% were achieved under laboratory and elevated conditions, respectively. This translates to a significant blade surface temperature reduction of 100–125 K with 10% mist injection at elevated conditions. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000134000001 [...]

On the Scaling of Pool Boiling Heat Flux With Gravity and Heater Size / Rishi Raj in Journal of heat transfer, Vol. 134 N° 1 (Janvier 2012) 

Public ISBD [article]  in Journal of heat transfer > Vol. 134 N° 1 (Janvier 2012) . - 13 p. Titre : On the Scaling of Pool Boiling Heat Flux With Gravity and Heater Size Type de document : texte imprimé Auteurs : Rishi Raj, Auteur ; Jungho Kim, Auteur ; John McQuillen, Auteur Année de publication : 2012 Article en page(s) : 13 p. Note générale : Heat transfer Langues : Anglais (eng) Mots-clés : Boiling  Heat  transfer  Surface  tension  Zero  gravity  experiments Index. décimale : 536 Chaleur. Thermodynamique Résumé : A framework for scaling pool boiling heat flux is developed using data from various heater sizes over a range of gravity levels. Boiling is buoyancy dominated for large heaters and/or high gravity conditions and the heat flux is heater size independent. The power law coefficient for gravity is a function of wall temperature. As the heater size or gravity level is reduced, a sharp transition in the heat flux is observed at a threshold value of Lh/Lc = 2.1. Below this threshold value, boiling is surface tension dominated and the dependence on gravity is smaller. The gravity scaling parameter for the heat flux in the buoyancy dominated boiling regime developed in the previous work is updated to account for subcooling effect. Based on this scaling parameter and the transition criteria, a methodology for predicting heat flux in the surface tension dominated boiling regime, typically observed under low-gravity conditions, is developed. Given the heat flux at a reference gravity level and heater size, the current framework allows the prediction of heat flux at any other gravity level and/or heater size under similar experimental conditions. The prediction is validated using data at over a range of subcoolings (11 °C <= DeltaTsub <= 32.6 °C), heater sizes (2.1 mm <= Lh <= 7 mm), and dissolved gas concentrations (3 ppm <= cg <= 3500 ppm). The prediction errors are significantly smaller than those from correlations currently available in the literature. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000134000001 [...] [article] On the Scaling of Pool Boiling Heat Flux With Gravity and Heater Size [texte imprimé] / Rishi Raj, Auteur ; Jungho Kim, Auteur ; John McQuillen, Auteur . - 2012 . - 13 p. Heat transfer Langues : Anglais (eng) in Journal of heat transfer > Vol. 134 N° 1 (Janvier 2012) . - 13 p. Mots-clés : Boiling  Heat  transfer  Surface  tension  Zero  gravity  experiments Index. décimale : 536 Chaleur. Thermodynamique Résumé : A framework for scaling pool boiling heat flux is developed using data from various heater sizes over a range of gravity levels. Boiling is buoyancy dominated for large heaters and/or high gravity conditions and the heat flux is heater size independent. The power law coefficient for gravity is a function of wall temperature. As the heater size or gravity level is reduced, a sharp transition in the heat flux is observed at a threshold value of Lh/Lc = 2.1. Below this threshold value, boiling is surface tension dominated and the dependence on gravity is smaller. The gravity scaling parameter for the heat flux in the buoyancy dominated boiling regime developed in the previous work is updated to account for subcooling effect. Based on this scaling parameter and the transition criteria, a methodology for predicting heat flux in the surface tension dominated boiling regime, typically observed under low-gravity conditions, is developed. Given the heat flux at a reference gravity level and heater size, the current framework allows the prediction of heat flux at any other gravity level and/or heater size under similar experimental conditions. The prediction is validated using data at over a range of subcoolings (11 °C <= DeltaTsub <= 32.6 °C), heater sizes (2.1 mm <= Lh <= 7 mm), and dissolved gas concentrations (3 ppm <= cg <= 3500 ppm). The prediction errors are significantly smaller than those from correlations currently available in the literature. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000134000001 [...]

Enhanced condensation of ethylene glycol on single pin-fin tubes / Hafiz Muhammad Ali in Journal of heat transfer, Vol. 134 N° 1 (Janvier 2012) 

Public ISBD [article]  in Journal of heat transfer > Vol. 134 N° 1 (Janvier 2012) . - 08 p. Titre : Enhanced condensation of ethylene glycol on single pin-fin tubes : effect of pin geometry Type de document : texte imprimé Auteurs : Hafiz Muhammad Ali, Auteur ; Adrian Briggs, Auteur Année de publication : 2012 Article en page(s) : 08 p. Note générale : Heat transfer Langues : Anglais (eng) Mots-clés : Condensation  Heat  transfer  Organic  compounds  Pipe  flow  Surface  tension Index. décimale : 553 Géologie économique. Minérographie. Minéraux. Formation et gisements de minerais Résumé : This paper presents a fundamental study into the underlying mechanisms influencing heat transfer during condensation on enhanced surfaces. New experimental data are reported for condensation of ethylene glycol at near atmospheric pressure and low velocity on 11 different 3-dimensional pin-fin tubes tested individually. Enhancements of the vapor-side, heat-transfer coefficients were found between 3 and 5.5 when compared to a plain tube at the same vapor-side temperature difference. Heat-transfer enhancement was found to be strongly dependent on the active surface area of the tubes, i.e., on the surface area of the parts of the tube and pin surface not covered by condensate retained by surface tension. For all the tubes, vapor-side, heat-transfer enhancements were found to be approximately twice the corresponding active-area enhancements. The best performing pin-fin tube gave a heat-transfer enhancement of 5.5; 17% higher than obtained from “optimised” two-dimensional fin-tubes reported in the literature and about 24% higher than the “equivalent” two-dimensional integral-fin tube (i.e., with the same fin-root diameter, longitudinal fin spacing and thickness, and fin height). The effects of surface area and surface tension induced enhancement and retention are discussed in the light of the new data and those of previous investigations. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000134000001 [...] [article] Enhanced condensation of ethylene glycol on single pin-fin tubes : effect of pin geometry [texte imprimé] / Hafiz Muhammad Ali, Auteur ; Adrian Briggs, Auteur . - 2012 . - 08 p. Heat transfer Langues : Anglais (eng) in Journal of heat transfer > Vol. 134 N° 1 (Janvier 2012) . - 08 p. Mots-clés : Condensation  Heat  transfer  Organic  compounds  Pipe  flow  Surface  tension Index. décimale : 553 Géologie économique. Minérographie. Minéraux. Formation et gisements de minerais Résumé : This paper presents a fundamental study into the underlying mechanisms influencing heat transfer during condensation on enhanced surfaces. New experimental data are reported for condensation of ethylene glycol at near atmospheric pressure and low velocity on 11 different 3-dimensional pin-fin tubes tested individually. Enhancements of the vapor-side, heat-transfer coefficients were found between 3 and 5.5 when compared to a plain tube at the same vapor-side temperature difference. Heat-transfer enhancement was found to be strongly dependent on the active surface area of the tubes, i.e., on the surface area of the parts of the tube and pin surface not covered by condensate retained by surface tension. For all the tubes, vapor-side, heat-transfer enhancements were found to be approximately twice the corresponding active-area enhancements. The best performing pin-fin tube gave a heat-transfer enhancement of 5.5; 17% higher than obtained from “optimised” two-dimensional fin-tubes reported in the literature and about 24% higher than the “equivalent” two-dimensional integral-fin tube (i.e., with the same fin-root diameter, longitudinal fin spacing and thickness, and fin height). The effects of surface area and surface tension induced enhancement and retention are discussed in the light of the new data and those of previous investigations. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000134000001 [...]

A study of critical heat flux during flow boiling in microchannel heat sinks / Tailian Chen in Journal of heat transfer, Vol. 134 N° 1 (Janvier 2012) 

Public ISBD [article]  in Journal of heat transfer > Vol. 134 N° 1 (Janvier 2012) . - 09 p. Titre : A study of critical heat flux during flow boiling in microchannel heat sinks Type de document : texte imprimé Auteurs : Tailian Chen, Auteur ; Suresh V. Garimella, Auteur Année de publication : 2012 Article en page(s) : 09 p. Note générale : Heat transfer Langues : Anglais (eng) Mots-clés : Boiling  Bubbles  Coolants  Cooling  Flow  visualisation  Heat  of  vaporisation  Heat  sinks  Microchannel  flow  Two-phase  flow Index. décimale : 536 Chaleur. Thermodynamique Résumé : The cooling capacity of two-phase transport in microchannels is limited by the occurrence of critical heat flux (CHF). Due to the nature of the phenomenon, it is challenging to obtain reliable CHF data without causing damage to the device under test. In this work, the critical heat fluxes for flow boiling of FC-77 in a silicon thermal test die containing 60 parallel microchannels were measured at five total flow rates through the microchannels in the range of 20–80 ml/min. CHF is caused by dryout at the wall near the exit of the microchannels, which in turn is attributed to the flow reversal upstream of the microchannels. The bubbles pushed back into the inlet plenum agglomerate; the resulting flow blockage is a likely cause for the occurrence of CHF which is marked by an abrupt increase in wall temperature near the exit and an abrupt decrease in pressure drop across the microchannels. A database of 49 data points obtained from five experiments in four independent studies with water, R-113, and FC-77 as coolants was compiled and analyzed. It is found that the CHF has a strong dependence on the coolant, the flow rate, and the area upon which the heat flux definition is based. However, at a given flow rate, the critical heat input (total heat transfer rate to the coolant when CHF occurs) depends only on the coolant and has minimal dependence on the details of the microchannel heat sink (channel size, number of channels, substrate material, and base area). The critical heat input for flow boiling in multiple parallel microchannels follows a well-defined trend with the product of mass flow rate and latent heat of vaporization. A power-law correlation is proposed which offers a simple, yet accurate method for predicting the CHF. The thermodynamic exit quality at CHF is also analyzed and discussed to provide insights into the CHF phenomenon in a heat sink containing multiple parallel microchannels. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000134000001 [...] [article] A study of critical heat flux during flow boiling in microchannel heat sinks [texte imprimé] / Tailian Chen, Auteur ; Suresh V. Garimella, Auteur . - 2012 . - 09 p. Heat transfer Langues : Anglais (eng) in Journal of heat transfer > Vol. 134 N° 1 (Janvier 2012) . - 09 p. Mots-clés : Boiling  Bubbles  Coolants  Cooling  Flow  visualisation  Heat  of  vaporisation  Heat  sinks  Microchannel  flow  Two-phase  flow Index. décimale : 536 Chaleur. Thermodynamique Résumé : The cooling capacity of two-phase transport in microchannels is limited by the occurrence of critical heat flux (CHF). Due to the nature of the phenomenon, it is challenging to obtain reliable CHF data without causing damage to the device under test. In this work, the critical heat fluxes for flow boiling of FC-77 in a silicon thermal test die containing 60 parallel microchannels were measured at five total flow rates through the microchannels in the range of 20–80 ml/min. CHF is caused by dryout at the wall near the exit of the microchannels, which in turn is attributed to the flow reversal upstream of the microchannels. The bubbles pushed back into the inlet plenum agglomerate; the resulting flow blockage is a likely cause for the occurrence of CHF which is marked by an abrupt increase in wall temperature near the exit and an abrupt decrease in pressure drop across the microchannels. A database of 49 data points obtained from five experiments in four independent studies with water, R-113, and FC-77 as coolants was compiled and analyzed. It is found that the CHF has a strong dependence on the coolant, the flow rate, and the area upon which the heat flux definition is based. However, at a given flow rate, the critical heat input (total heat transfer rate to the coolant when CHF occurs) depends only on the coolant and has minimal dependence on the details of the microchannel heat sink (channel size, number of channels, substrate material, and base area). The critical heat input for flow boiling in multiple parallel microchannels follows a well-defined trend with the product of mass flow rate and latent heat of vaporization. A power-law correlation is proposed which offers a simple, yet accurate method for predicting the CHF. The thermodynamic exit quality at CHF is also analyzed and discussed to provide insights into the CHF phenomenon in a heat sink containing multiple parallel microchannels. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000134000001 [...]

Extending fluorescence thermometry to measuring wall surface temperatures using evanescent-wave illumination / Myeongsub Kim in Journal of heat transfer, Vol. 134 N° 1 (Janvier 2012) 

Public ISBD [article]  in Journal of heat transfer > Vol. 134 N° 1 (Janvier 2012) . - 08 p. Titre : Extending fluorescence thermometry to measuring wall surface temperatures using evanescent-wave illumination Type de document : texte imprimé Auteurs : Myeongsub Kim, Auteur ; Minami Yoda, Auteur Année de publication : 2012 Article en page(s) : 08 p. Note générale : Heat transfer Langues : Anglais (eng) Mots-clés : Boundary  layers  Computational  fluid  dynamics  Cooling  Dissolving  Flow  simulation  Flow  visualisation  Fluorescence  Laminar  flow  Microchannel  flow  Poiseuille  flow  Two-phase  flow Index. décimale : 536 Chaleur. Thermodynamique Résumé : Cooling microelectronics with heat flux values of hundreds of kW/cm2 over hot spots with typical dimensions well below 1 mm will require new single- and two-phase thermal management technologies with micron-scale addressability. However, experimental studies of thermal transport through micro- and mini-channels report a wide range of Nusselt numbers even in laminar single-phase flows, presumably due in part to variations in channel geometry and surface roughness. These variations make constructing accurate numerical models for what would be otherwise straightforward computational simulations challenging. There is, therefore, a need for experimental techniques that can measure both bulk fluid and wall surface temperatures at micron-scale spatial resolution without disturbing the flow in both heat transfer and microfluidics applications. We report here the evaluation of a nonintrusive technique, fluorescence thermometry (FT), to determine wall surface and bulk fluid temperatures with a spatial resolution of O(10 µm) for water flowing through a heated channel. Fluorescence thermometry is typically used to estimate water temperature fields based on variations in the emission intensity of a fluorophore dissolved in the water. The accuracy of FT can be improved by taking the ratio of the emission signals from two different fluorophores (dual-tracer FT or DFT) to eliminate variations in the signal due to (spatial and temporal) variations in the excitation intensity. In this work, two temperature-sensitive fluorophores, fluorescein and sulforhodamine B, with emission intensities that increase and decrease, respectively, with increasing temperature, are used to further improve the accuracy of the temperature measurements. Water temperature profiles were measured in steady Poiseuille flow at Reynolds numbers of 3.3 and 8.3 through a 1 mm2 heated minichannel. Water temperatures in the bulk flow (i.e., away from the walls) were measured using DFT with an average uncertainty of 0.2 °C at a spatial resolution of 30 µm. Temperatures within the first 0.3 µm next to the wall were measured using evanescent-wave illumination of a single temperature-sensitive fluorophore with an average uncertainty of less than 0.2 °C at a spatial resolution of 10 µm. The results are compared with numerical predictions, which suggest that the water temperatures at an average distance of ~70 nm from the wall are identical within experimental uncertainty to the wall surface temperature. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000134000001 [...] [article] Extending fluorescence thermometry to measuring wall surface temperatures using evanescent-wave illumination [texte imprimé] / Myeongsub Kim, Auteur ; Minami Yoda, Auteur . - 2012 . - 08 p. Heat transfer Langues : Anglais (eng) in Journal of heat transfer > Vol. 134 N° 1 (Janvier 2012) . - 08 p. Mots-clés : Boundary  layers  Computational  fluid  dynamics  Cooling  Dissolving  Flow  simulation  Flow  visualisation  Fluorescence  Laminar  flow  Microchannel  flow  Poiseuille  flow  Two-phase  flow Index. décimale : 536 Chaleur. Thermodynamique Résumé : Cooling microelectronics with heat flux values of hundreds of kW/cm2 over hot spots with typical dimensions well below 1 mm will require new single- and two-phase thermal management technologies with micron-scale addressability. However, experimental studies of thermal transport through micro- and mini-channels report a wide range of Nusselt numbers even in laminar single-phase flows, presumably due in part to variations in channel geometry and surface roughness. These variations make constructing accurate numerical models for what would be otherwise straightforward computational simulations challenging. There is, therefore, a need for experimental techniques that can measure both bulk fluid and wall surface temperatures at micron-scale spatial resolution without disturbing the flow in both heat transfer and microfluidics applications. We report here the evaluation of a nonintrusive technique, fluorescence thermometry (FT), to determine wall surface and bulk fluid temperatures with a spatial resolution of O(10 µm) for water flowing through a heated channel. Fluorescence thermometry is typically used to estimate water temperature fields based on variations in the emission intensity of a fluorophore dissolved in the water. The accuracy of FT can be improved by taking the ratio of the emission signals from two different fluorophores (dual-tracer FT or DFT) to eliminate variations in the signal due to (spatial and temporal) variations in the excitation intensity. In this work, two temperature-sensitive fluorophores, fluorescein and sulforhodamine B, with emission intensities that increase and decrease, respectively, with increasing temperature, are used to further improve the accuracy of the temperature measurements. Water temperature profiles were measured in steady Poiseuille flow at Reynolds numbers of 3.3 and 8.3 through a 1 mm2 heated minichannel. Water temperatures in the bulk flow (i.e., away from the walls) were measured using DFT with an average uncertainty of 0.2 °C at a spatial resolution of 30 µm. Temperatures within the first 0.3 µm next to the wall were measured using evanescent-wave illumination of a single temperature-sensitive fluorophore with an average uncertainty of less than 0.2 °C at a spatial resolution of 10 µm. The results are compared with numerical predictions, which suggest that the water temperatures at an average distance of ~70 nm from the wall are identical within experimental uncertainty to the wall surface temperature. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000134000001 [...]

Heat transfer characteristics of compressible laminar flow through microtubes / Chungpyo Hong in Journal of heat transfer, Vol. 134 N° 1 (Janvier 2012) 

Public ISBD [article]  in Journal of heat transfer > Vol. 134 N° 1 (Janvier 2012) . - 08 p. Titre : Heat transfer characteristics of compressible laminar flow through microtubes Type de document : texte imprimé Auteurs : Chungpyo Hong, Auteur ; Takaharu Yamamoto, Auteur ; Yutaka Asako, Auteur Année de publication : 2012 Article en page(s) : 08 p. Note générale : Heat transfer Langues : Anglais (eng) Mots-clés : Aerodynamics  Compressible  flow  Convection  Laminar  flow  Mach  number  Pipe  flow  Stagnation  flow  Subsonic  flow Index. décimale : 536 Chaleur. Thermodynamique Résumé : This paper describes experimental results on heat transfer characteristics of gaseous flow in a microtube with constant wall temperature. The experiments were performed for nitrogen gas flow through three microtubes of 123 µm, 163 µm, and 243 µm in diameter with 50mm in length, respectively. The wall temperature was maintained at 310 K, 330 K, and 350 K by circulating water around the microtube, respectively. The stagnation pressure is chosen in such a way that the exit Mach number ranges from 0.1 to 1.0. The outlet pressure was fixed at the atmospheric condition. The total temperature at the outlet, the inlet stagnation temperature, the mass flow rate, and the inlet pressure were measured. The numerical computations based on the Arbitrary-Lagrangian-Eulerian (ALE) method were also performed with the same conditions of the experiment for validation of numerical results. Both the results are in excellent agreement. In some cases, the total temperatures obtained by the present experimental study are higher than the wall temperature. This is due to the additional heat transfer from the wall to the gas near the microtube outlet caused by the temperature fall due to the energy conversion into the kinetic energy. A quantitative correlation for the prediction of the heat transfer rate of the gaseous flow in microtubes which had been proposed in our previous study (Hong and Asako, 2007, “Heat Transfer Characteristics of Gaseous Flows in a Microchannel and a Microtube with Constant Wall Temperature,” Numer. Heat Transfer, Part A, 52, pp. 219–238) was validated. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000134000001 [...] [article] Heat transfer characteristics of compressible laminar flow through microtubes [texte imprimé] / Chungpyo Hong, Auteur ; Takaharu Yamamoto, Auteur ; Yutaka Asako, Auteur . - 2012 . - 08 p. Heat transfer Langues : Anglais (eng) in Journal of heat transfer > Vol. 134 N° 1 (Janvier 2012) . - 08 p. Mots-clés : Aerodynamics  Compressible  flow  Convection  Laminar  flow  Mach  number  Pipe  flow  Stagnation  flow  Subsonic  flow Index. décimale : 536 Chaleur. Thermodynamique Résumé : This paper describes experimental results on heat transfer characteristics of gaseous flow in a microtube with constant wall temperature. The experiments were performed for nitrogen gas flow through three microtubes of 123 µm, 163 µm, and 243 µm in diameter with 50mm in length, respectively. The wall temperature was maintained at 310 K, 330 K, and 350 K by circulating water around the microtube, respectively. The stagnation pressure is chosen in such a way that the exit Mach number ranges from 0.1 to 1.0. The outlet pressure was fixed at the atmospheric condition. The total temperature at the outlet, the inlet stagnation temperature, the mass flow rate, and the inlet pressure were measured. The numerical computations based on the Arbitrary-Lagrangian-Eulerian (ALE) method were also performed with the same conditions of the experiment for validation of numerical results. Both the results are in excellent agreement. In some cases, the total temperatures obtained by the present experimental study are higher than the wall temperature. This is due to the additional heat transfer from the wall to the gas near the microtube outlet caused by the temperature fall due to the energy conversion into the kinetic energy. A quantitative correlation for the prediction of the heat transfer rate of the gaseous flow in microtubes which had been proposed in our previous study (Hong and Asako, 2007, “Heat Transfer Characteristics of Gaseous Flows in a Microchannel and a Microtube with Constant Wall Temperature,” Numer. Heat Transfer, Part A, 52, pp. 219–238) was validated. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000134000001 [...]

Flow and heat transfer of Jeffrey fluid over a continuously moving surface with a parallel free stream / Hayat, T. in Journal of heat transfer, Vol. 134 N° 1 (Janvier 2012) 

Public ISBD [article]  in Journal of heat transfer > Vol. 134 N° 1 (Janvier 2012) . - 07 p. Titre : Flow and heat transfer of Jeffrey fluid over a continuously moving surface with a parallel free stream Type de document : texte imprimé Auteurs : Hayat, T., Auteur ; Z. Iqbal, Auteur ; Mustafa, M., Auteur Année de publication : 2012 Article en page(s) : 07 p. Note générale : Heat transfer Langues : Anglais (eng) Mots-clés : Boundary  layers  External  flows  Flow  simulation  Heat  transfer  Non-Newtonian  flow  Non-Newtonian  fluids  Rheology Index. décimale : 536 Chaleur. Thermodynamique Résumé : This communication studies the flow and heat transfer characteristics over a continuously moving surface in the presence of a free stream velocity. The Jeffrey fluid is treated as a rheological model. The series expressions of velocity and temperature fields are constructed by applying the homotopy analysis method (HAM). The influence of emerging parameters such as local Deborah number (beta), the ratio of relaxation and retardation times (lambda2), the Prandtl number (Pr), and the Eckert number (Ec) on the velocity and temperature profiles are presented in the form of graphical and tabulated results for different values of lambda. It is found that the boundary layer thickness is an increasing function of local Deborah number (beta). However, the temperature and thermal boundary layer thickness decreases with the increasing values of local Deborah number (beta). DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000134000001 [...] [article] Flow and heat transfer of Jeffrey fluid over a continuously moving surface with a parallel free stream [texte imprimé] / Hayat, T., Auteur ; Z. Iqbal, Auteur ; Mustafa, M., Auteur . - 2012 . - 07 p. Heat transfer Langues : Anglais (eng) in Journal of heat transfer > Vol. 134 N° 1 (Janvier 2012) . - 07 p. Mots-clés : Boundary  layers  External  flows  Flow  simulation  Heat  transfer  Non-Newtonian  flow  Non-Newtonian  fluids  Rheology Index. décimale : 536 Chaleur. Thermodynamique Résumé : This communication studies the flow and heat transfer characteristics over a continuously moving surface in the presence of a free stream velocity. The Jeffrey fluid is treated as a rheological model. The series expressions of velocity and temperature fields are constructed by applying the homotopy analysis method (HAM). The influence of emerging parameters such as local Deborah number (beta), the ratio of relaxation and retardation times (lambda2), the Prandtl number (Pr), and the Eckert number (Ec) on the velocity and temperature profiles are presented in the form of graphical and tabulated results for different values of lambda. It is found that the boundary layer thickness is an increasing function of local Deborah number (beta). However, the temperature and thermal boundary layer thickness decreases with the increasing values of local Deborah number (beta). DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000134000001 [...]

Solution of inverse convection heat transfer problem using an enhanced particle swarm optimization algorithm / Peng Ding in Journal of heat transfer, Vol. 134 N° 1 (Janvier 2012) 

Public ISBD [article]  in Journal of heat transfer > Vol. 134 N° 1 (Janvier 2012) . - 10 p. Titre : Solution of inverse convection heat transfer problem using an enhanced particle swarm optimization algorithm Type de document : texte imprimé Auteurs : Peng Ding, Auteur Année de publication : 2012 Article en page(s) : 10 p. Note générale : Heat transfer Langues : Anglais (eng) Mots-clés : Channel  flow  Convection  Particle  swarm  optimisation Index. décimale : 536 Chaleur. Thermodynamique Résumé : The main objective of this paper is to solve the inverse convection heat transfer problems with particle swarm optimization method. An enhanced particle swarm optimization (EPSO) algorithm is proposed to overcome the shortcoming of earlier convergence of standard PSO algorithms. The performance of EPSO is tested by some benchmark functions; it is shown that EPSO has a strong antilocal trap capability especially for high dimensional multimodal optimization problems. At last, EPSO is used to identify the unknown boundary heat flux in a channel flow. According to the computational results of four test problems, it is clear that the proposed EPSO algorithm is able to estimate the unknown heat flux accurately even when the input data contain measurement error. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000134000001 [...] [article] Solution of inverse convection heat transfer problem using an enhanced particle swarm optimization algorithm [texte imprimé] / Peng Ding, Auteur . - 2012 . - 10 p. Heat transfer Langues : Anglais (eng) in Journal of heat transfer > Vol. 134 N° 1 (Janvier 2012) . - 10 p. Mots-clés : Channel  flow  Convection  Particle  swarm  optimisation Index. décimale : 536 Chaleur. Thermodynamique Résumé : The main objective of this paper is to solve the inverse convection heat transfer problems with particle swarm optimization method. An enhanced particle swarm optimization (EPSO) algorithm is proposed to overcome the shortcoming of earlier convergence of standard PSO algorithms. The performance of EPSO is tested by some benchmark functions; it is shown that EPSO has a strong antilocal trap capability especially for high dimensional multimodal optimization problems. At last, EPSO is used to identify the unknown boundary heat flux in a channel flow. According to the computational results of four test problems, it is clear that the proposed EPSO algorithm is able to estimate the unknown heat flux accurately even when the input data contain measurement error. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000134000001 [...]

Local heat/mass transfer and friction loss measurement in a rotating matrix cooling channel / In Taek Oh in Journal of heat transfer, Vol. 134 N° 1 (Janvier 2012) 

Public ISBD [article]  in Journal of heat transfer > Vol. 134 N° 1 (Janvier 2012) . - 09 p. Titre : Local heat/mass transfer and friction loss measurement in a rotating matrix cooling channel Type de document : texte imprimé Auteurs : In Taek Oh, Auteur ; Kyung Min Kim, Auteur ; Dong Hyun Lee, Auteur Année de publication : 2012 Article en page(s) : 09 p. Note générale : Heat transfer Langues : Anglais (eng) Mots-clés : Channel  flow  Gas  turbines  Heat  transfer  Mass  transfer  Rotational  flow  Swirling  flow  Turbulence Index. décimale : 536 Chaleur. Thermodynamique Résumé : The present investigation provides detailed local heat/mass transfer and pressure drop characteristics in a matrix cooling channel, under rotating conditions. The matrix channel had cooling subpassages with crossing angles of 45 deg. The detailed heat/mass transfer coefficients were measured via the naphthalene sublimation method, and pressure drops were also obtained. The experiments were conducted for various Reynolds numbers (10,500 to 44,000) and rotation numbers (0.0 to 0.8). In the stationary case, the heat transfer characteristics were dominated by turning, impinging, and swirling flow, induced by the matrix channel geometry. Average heat/mass transfer coefficients on the leading and trailing surfaces in the stationary channel were approximately 2.1 times greater than those in a smooth channel. In the rotating cases, the effect of rotation on heat/mass transfer characteristics differed from that of typical rotating channels with radially outward flow. As the rotation number increased, the Sherwood number ratios increased on the leading surfaces but changed only slightly on the trailing surfaces. The thermal performance factors increased with rotation number due to the increased Sherwood number ratios and decreased friction factor ratios. DEWEY : 536 ISSN : 0022-1481 En ligne : http://www.asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO00013400 [...] [article] Local heat/mass transfer and friction loss measurement in a rotating matrix cooling channel [texte imprimé] / In Taek Oh, Auteur ; Kyung Min Kim, Auteur ; Dong Hyun Lee, Auteur . - 2012 . - 09 p. Heat transfer Langues : Anglais (eng) in Journal of heat transfer > Vol. 134 N° 1 (Janvier 2012) . - 09 p. Mots-clés : Channel  flow  Gas  turbines  Heat  transfer  Mass  transfer  Rotational  flow  Swirling  flow  Turbulence Index. décimale : 536 Chaleur. Thermodynamique Résumé : The present investigation provides detailed local heat/mass transfer and pressure drop characteristics in a matrix cooling channel, under rotating conditions. The matrix channel had cooling subpassages with crossing angles of 45 deg. The detailed heat/mass transfer coefficients were measured via the naphthalene sublimation method, and pressure drops were also obtained. The experiments were conducted for various Reynolds numbers (10,500 to 44,000) and rotation numbers (0.0 to 0.8). In the stationary case, the heat transfer characteristics were dominated by turning, impinging, and swirling flow, induced by the matrix channel geometry. Average heat/mass transfer coefficients on the leading and trailing surfaces in the stationary channel were approximately 2.1 times greater than those in a smooth channel. In the rotating cases, the effect of rotation on heat/mass transfer characteristics differed from that of typical rotating channels with radially outward flow. As the rotation number increased, the Sherwood number ratios increased on the leading surfaces but changed only slightly on the trailing surfaces. The thermal performance factors increased with rotation number due to the increased Sherwood number ratios and decreased friction factor ratios. DEWEY : 536 ISSN : 0022-1481 En ligne : http://www.asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO00013400 [...]

Protuberances in a turbulent thermal boundary layer / Steven R. Mart in Journal of heat transfer, Vol. 134 N° 1 (Janvier 2012) 

Public ISBD [article]  in Journal of heat transfer > Vol. 134 N° 1 (Janvier 2012) . - 12 p. Titre : Protuberances in a turbulent thermal boundary layer Type de document : texte imprimé Auteurs : Steven R. Mart, Auteur ; Stephen T. McClain, Auteur Année de publication : 2012 Article en page(s) : 12 p. Note générale : Heat transfer Langues : Anglais (eng) Mots-clés : Anemometry  Blades  Boundary  layer  turbulence  Flow  visualisation  Heat  transfer  Infrared  imaging  Thermal  conductivity  Thermocouples  Turbines Index. décimale : 536 Chaleur. Thermodynamique Résumé : Recent efforts to evaluate the effects of isolated protuberances within velocity and thermal boundary layers have been performed using transient heat transfer approaches. While these approaches provide accurate and highly resolved measurements of surface flux, measuring the state of the thermal boundary layer during transient tests with high spatial resolution presents several challenges. As such, the heat transfer enhancement evaluated during transient tests is presently correlated to a Reynolds number based either on the distance from the leading edge or on the momentum thickness. Heat flux and temperature variations along the surface of a turbine blade may cause significant differences between the shapes and sizes of the velocity and thermal boundary layer profiles. Therefore, correlations are needed which relate the states of both the velocity and thermal boundary layers to protuberance and roughness distribution heat transfer. In this study, a series of three experiments are performed for various freestream velocities to investigate the local temperature details of protuberances interacting with thermal boundary layers. The experimental measurements are performed using isolated protuberances of varying thermal conductivity on a steadily heated, constant flux flat plate. In the first experiment, detailed surface temperature maps are recorded using infrared thermography. In the second experiment, the unperturbed velocity profile over the plate without heating is measured using hot-wire anemometry. Finally, the thermal boundary layer over the steadily heated plate is measured using a thermocouple probe. Because of the constant flux experimental configuration, the protuberances provide negligible heat flux augmentation. Consequently, the variation in protuberance temperature is investigated using the velocity boundary layer parameters, the thermal boundary layer parameters, and the local fluid temperature at the protuberance apices. A comparison of results using plastic and steel protuberances illuminates the importance of the shape of the thermal and velocity boundary layers in determining the minimum protuberance temperatures. DEWEY : 536 ISSN : 0022-1481 En ligne : http://www.asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO00013400 [...] [article] Protuberances in a turbulent thermal boundary layer [texte imprimé] / Steven R. Mart, Auteur ; Stephen T. McClain, Auteur . - 2012 . - 12 p. Heat transfer Langues : Anglais (eng) in Journal of heat transfer > Vol. 134 N° 1 (Janvier 2012) . - 12 p. Mots-clés : Anemometry  Blades  Boundary  layer  turbulence  Flow  visualisation  Heat  transfer  Infrared  imaging  Thermal  conductivity  Thermocouples  Turbines Index. décimale : 536 Chaleur. Thermodynamique Résumé : Recent efforts to evaluate the effects of isolated protuberances within velocity and thermal boundary layers have been performed using transient heat transfer approaches. While these approaches provide accurate and highly resolved measurements of surface flux, measuring the state of the thermal boundary layer during transient tests with high spatial resolution presents several challenges. As such, the heat transfer enhancement evaluated during transient tests is presently correlated to a Reynolds number based either on the distance from the leading edge or on the momentum thickness. Heat flux and temperature variations along the surface of a turbine blade may cause significant differences between the shapes and sizes of the velocity and thermal boundary layer profiles. Therefore, correlations are needed which relate the states of both the velocity and thermal boundary layers to protuberance and roughness distribution heat transfer. In this study, a series of three experiments are performed for various freestream velocities to investigate the local temperature details of protuberances interacting with thermal boundary layers. The experimental measurements are performed using isolated protuberances of varying thermal conductivity on a steadily heated, constant flux flat plate. In the first experiment, detailed surface temperature maps are recorded using infrared thermography. In the second experiment, the unperturbed velocity profile over the plate without heating is measured using hot-wire anemometry. Finally, the thermal boundary layer over the steadily heated plate is measured using a thermocouple probe. Because of the constant flux experimental configuration, the protuberances provide negligible heat flux augmentation. Consequently, the variation in protuberance temperature is investigated using the velocity boundary layer parameters, the thermal boundary layer parameters, and the local fluid temperature at the protuberance apices. A comparison of results using plastic and steel protuberances illuminates the importance of the shape of the thermal and velocity boundary layers in determining the minimum protuberance temperatures. DEWEY : 536 ISSN : 0022-1481 En ligne : http://www.asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO00013400 [...]

A numerical simulation study on the effects of crucible rotation and magnetic fields in growth of SiGe by the traveling heater method / Youhei Takagi in Journal of heat transfer, Vol. 134 N° 1 (Janvier 2012) 

Public ISBD [article]  in Journal of heat transfer > Vol. 134 N° 1 (Janvier 2012) . - 07 p. Titre : A numerical simulation study on the effects of crucible rotation and magnetic fields in growth of SiGe by the traveling heater method Type de document : texte imprimé Auteurs : Youhei Takagi, Auteur ; Yasunori Okano, Auteur ; Sadik Dost, Auteur Année de publication : 2012 Article en page(s) : 07 p. Note générale : Heat transfer Langues : Anglais (eng) Mots-clés : Convection  Crystal  growth  from  melt  Flow  simulation  Ge-Si  alloys  Magnetohydrodynamics  Numerical  analysis  Rotational  flow  Semiconductor  growth  Semiconductor  materials  Zone  melting Index. décimale : 536 Chaleur. Thermodynamique Résumé : A numerical simulation study was carried out to shed light on the effects of applied crucible rotation and static magnetic field during the traveling heater method growth of bulk SiGe single crystals. The simulation results show that the application of crucible rotation weakens the radial silicon concentration gradient due to the effect of centrifugal force. The effects of applied static magnetic field direction and strength on the concentration field in the melt were also studied. It was found that the simultaneous application of crucible rotation and static magnetic field is best to grow large crystals with uniform composition. An optimum combination of crucible rotation rates and applied magnetic field strengths is determined. DEWEY : 536 ISSN : 0022-1481 En ligne : http://www.asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO00013400 [...] [article] A numerical simulation study on the effects of crucible rotation and magnetic fields in growth of SiGe by the traveling heater method [texte imprimé] / Youhei Takagi, Auteur ; Yasunori Okano, Auteur ; Sadik Dost, Auteur . - 2012 . - 07 p. Heat transfer Langues : Anglais (eng) in Journal of heat transfer > Vol. 134 N° 1 (Janvier 2012) . - 07 p. Mots-clés : Convection  Crystal  growth  from  melt  Flow  simulation  Ge-Si  alloys  Magnetohydrodynamics  Numerical  analysis  Rotational  flow  Semiconductor  growth  Semiconductor  materials  Zone  melting Index. décimale : 536 Chaleur. Thermodynamique Résumé : A numerical simulation study was carried out to shed light on the effects of applied crucible rotation and static magnetic field during the traveling heater method growth of bulk SiGe single crystals. The simulation results show that the application of crucible rotation weakens the radial silicon concentration gradient due to the effect of centrifugal force. The effects of applied static magnetic field direction and strength on the concentration field in the melt were also studied. It was found that the simultaneous application of crucible rotation and static magnetic field is best to grow large crystals with uniform composition. An optimum combination of crucible rotation rates and applied magnetic field strengths is determined. DEWEY : 536 ISSN : 0022-1481 En ligne : http://www.asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO00013400 [...]

Size effects during femtosecond laser interaction with nanosized metal particles / Jing Huang in Journal of heat transfer, Vol. 134 N° 1 (Janvier 2012) 

Public ISBD [article]  in Journal of heat transfer > Vol. 134 N° 1 (Janvier 2012) . - 07 p. Titre : Size effects during femtosecond laser interaction with nanosized metal particles Type de document : texte imprimé Auteurs : Jing Huang, Auteur ; Yuwen Zhang, Auteur ; J. K. Chen, Auteur Année de publication : 2012 Article en page(s) : 07 p. Note générale : Heat teansfer Langues : Anglais (eng) Mots-clés : Evaporation  Gold  High-speed  optical  techniques  Laser  beam  effects  Laser  sintering  Melting  Nanoparticles  Particle  size  Solidification Index. décimale : 536 Chaleur. Thermodynamique Résumé : To obtain more in-depth knowledge about the microscopic process during laser sintering, phase change processes including melting, evaporation, and resolidification during the irradiation of femtosecond laser on nanosized gold particles were simulated. The effects of multiple reflections and pulse energy overlapping in small particle size were considered. The results show that when the particle size is big enough, the simulation results match those of old model. When the particle size is small and laser fluence is high, no resolidification takes place in the time range of the simulation. The laser fluence range to achieve partial melting is narrow when the particle is small. When the diameter is smaller than 400 nm, temperature gradient during the heating period is ignorable, which is different from the large particles. The threshold value of laser fluence to achieve vaporization is about two times higher than that of melting with the same particle size. DEWEY : 536 ISSN : 0022-1481 En ligne : http://www.asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO00013400 [...] [article] Size effects during femtosecond laser interaction with nanosized metal particles [texte imprimé] / Jing Huang, Auteur ; Yuwen Zhang, Auteur ; J. K. Chen, Auteur . - 2012 . - 07 p. Heat teansfer Langues : Anglais (eng) in Journal of heat transfer > Vol. 134 N° 1 (Janvier 2012) . - 07 p. Mots-clés : Evaporation  Gold  High-speed  optical  techniques  Laser  beam  effects  Laser  sintering  Melting  Nanoparticles  Particle  size  Solidification Index. décimale : 536 Chaleur. Thermodynamique Résumé : To obtain more in-depth knowledge about the microscopic process during laser sintering, phase change processes including melting, evaporation, and resolidification during the irradiation of femtosecond laser on nanosized gold particles were simulated. The effects of multiple reflections and pulse energy overlapping in small particle size were considered. The results show that when the particle size is big enough, the simulation results match those of old model. When the particle size is small and laser fluence is high, no resolidification takes place in the time range of the simulation. The laser fluence range to achieve partial melting is narrow when the particle is small. When the diameter is smaller than 400 nm, temperature gradient during the heating period is ignorable, which is different from the large particles. The threshold value of laser fluence to achieve vaporization is about two times higher than that of melting with the same particle size. DEWEY : 536 ISSN : 0022-1481 En ligne : http://www.asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO00013400 [...]

Onset of thermogravitational convection in a ferrofluid layer with temperature dependent viscosity / I. S. Shivakumara in Journal of heat transfer, Vol. 134 N° 1 (Janvier 2012) 

Public ISBD [article]  in Journal of heat transfer > Vol. 134 N° 1 (Janvier 2012) . - 07 p. Titre : Onset of thermogravitational convection in a ferrofluid layer with temperature dependent viscosity Type de document : texte imprimé Auteurs : I. S. Shivakumara, Auteur ; Jinho Lee, Auteur ; C. E. Nanjundappa, Auteur Année de publication : 2012 Article en page(s) : 07 p. Note générale : Heat transfer Langues : Anglais (eng) Mots-clés : Convection  Magnetic  fluids  Magnetisation  Magnetohydrodynamics  Viscosity Index. décimale : 536 Chaleur. Thermodynamique Résumé : The onset of thermogravitational convection in a horizontal ferrofluid layer is investigated with viscosity depending exponentially on temperature. The bounding surfaces of the ferrofluid layer are considered to be either stress free or rigid-ferromagnetic and insulated to temperature perturbations. The resulting eigenvalue problem is solved numerically using the Galerkin technique and also by a regular perturbation technique for different types of velocity boundary conditions, namely free-free, rigid-rigid, and lower rigid- upper free. It is observed that increasing the viscosity parameter, Lambda, and the magnetic number, M1, is to hasten the onset of ferroconvection, while the nonlinearity of fluid magnetization, M3, is found to have no influence on the stability of the system. The critical stability parameters are found to be the same in the limiting cases of either no magnetic forces or no buoyancy forces. DEWEY : 536 ISSN : 0022-1481 En ligne : http://www.asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO00013400 [...] [article] Onset of thermogravitational convection in a ferrofluid layer with temperature dependent viscosity [texte imprimé] / I. S. Shivakumara, Auteur ; Jinho Lee, Auteur ; C. E. Nanjundappa, Auteur . - 2012 . - 07 p. Heat transfer Langues : Anglais (eng) in Journal of heat transfer > Vol. 134 N° 1 (Janvier 2012) . - 07 p. Mots-clés : Convection  Magnetic  fluids  Magnetisation  Magnetohydrodynamics  Viscosity Index. décimale : 536 Chaleur. Thermodynamique Résumé : The onset of thermogravitational convection in a horizontal ferrofluid layer is investigated with viscosity depending exponentially on temperature. The bounding surfaces of the ferrofluid layer are considered to be either stress free or rigid-ferromagnetic and insulated to temperature perturbations. The resulting eigenvalue problem is solved numerically using the Galerkin technique and also by a regular perturbation technique for different types of velocity boundary conditions, namely free-free, rigid-rigid, and lower rigid- upper free. It is observed that increasing the viscosity parameter, Lambda, and the magnetic number, M1, is to hasten the onset of ferroconvection, while the nonlinearity of fluid magnetization, M3, is found to have no influence on the stability of the system. The critical stability parameters are found to be the same in the limiting cases of either no magnetic forces or no buoyancy forces. DEWEY : 536 ISSN : 0022-1481 En ligne : http://www.asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO00013400 [...]

Tomography-based determination of effective transport properties for reacting porous media / Sophia Haussener in Journal of heat transfer, Vol. 134 N° 1 (Janvier 2012) 

Public ISBD [article]  in Journal of heat transfer > Vol. 134 N° 1 (Janvier 2012) . - 08 p. Titre : Tomography-based determination of effective transport properties for reacting porous media Type de document : texte imprimé Auteurs : Sophia Haussener, Auteur ; Iwan Jerjen, Auteur ; Peter Wyss, Auteur Année de publication : 2012 Article en page(s) : 08 p. Note générale : Heat transfer Langues : Anglais (eng) Mots-clés : Chemically  reactive  flow  Computerised  tomography  Convection  Finite  volume  methods  Flow  simulation  Flow  through  porous  media  Fuel  gasification  Mass  transfer  Porosity  Pyrolysis  Solid-vapour  transformations  Thermochemistry  Two-phase  flow Index. décimale : 536 Chaleur. Thermodynamique Résumé : The effective heat and mass transport properties of a porous packed bed of particles undergoing a high-temperature solid–gas thermochemical transformation are determined. The exact 3D geometry of the reacting porous media is obtained by high-resolution computed tomography. Finite volume techniques are applied to solve the governing conservation equations at the pore-level scale and to determine the effective transport properties as a function of the reaction extent, namely, the convective heat transfer coefficient, permeability, Dupuit–Forchheimer coefficient, tortuosity, and residence time distributions. These exhibit strong dependence on the bed morphological properties (e.g., porosity, specific surface area, particle size) and, consequently, vary with time as the reaction progresses. DEWEY : 536 ISSN : 0022-1481 En ligne : http://www.asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO00013400 [...] [article] Tomography-based determination of effective transport properties for reacting porous media [texte imprimé] / Sophia Haussener, Auteur ; Iwan Jerjen, Auteur ; Peter Wyss, Auteur . - 2012 . - 08 p. Heat transfer Langues : Anglais (eng) in Journal of heat transfer > Vol. 134 N° 1 (Janvier 2012) . - 08 p. Mots-clés : Chemically  reactive  flow  Computerised  tomography  Convection  Finite  volume  methods  Flow  simulation  Flow  through  porous  media  Fuel  gasification  Mass  transfer  Porosity  Pyrolysis  Solid-vapour  transformations  Thermochemistry  Two-phase  flow Index. décimale : 536 Chaleur. Thermodynamique Résumé : The effective heat and mass transport properties of a porous packed bed of particles undergoing a high-temperature solid–gas thermochemical transformation are determined. The exact 3D geometry of the reacting porous media is obtained by high-resolution computed tomography. Finite volume techniques are applied to solve the governing conservation equations at the pore-level scale and to determine the effective transport properties as a function of the reaction extent, namely, the convective heat transfer coefficient, permeability, Dupuit–Forchheimer coefficient, tortuosity, and residence time distributions. These exhibit strong dependence on the bed morphological properties (e.g., porosity, specific surface area, particle size) and, consequently, vary with time as the reaction progresses. DEWEY : 536 ISSN : 0022-1481 En ligne : http://www.asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO00013400 [...]

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

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

Controlling thermal conductivity of alloys via atomic ordering / John C. Duda in Journal of heat transfer, Vol. 134 N° 1 (Janvier 2012) 

Public ISBD [article]  in Journal of heat transfer > Vol. 134 N° 1 (Janvier 2012) . - 04 p. Titre : Controlling thermal conductivity of alloys via atomic ordering Type de document : texte imprimé Auteurs : John C. Duda, Auteur ; Timothy S. English, Auteur ; Donald A. Jordan, Auteur Année de publication : 2012 Article en page(s) : 04 p. Note générale : Heat transfer Langues : Anglais (eng) Mots-clés : Molecular  dynamics  method  Order-disorder  transformations  Phonons  Solid  solutions  Thermal  conductivity Index. décimale : 536 Chaleur. Thermodynamique Résumé : Many random substitutional solid solutions (alloys) will display a tendency to atomically order given the appropriate kinetic and thermodynamic conditions. Such order–disorder transitions will result in major crystallographic reconfigurations, where the atomic basis, symmetry, and periodicity of the alloy change dramatically. Consequently, phonon behavior in these alloys will vary greatly depending on the type and degree of ordering achieved. To investigate these phenomena, the role of the order–disorder transition on phononic transport properties of Lennard–Jones type binary alloys is explored via nonequilibrium molecular dynamics simulations. Particular attention is paid to regimes in which the alloy is only partially ordered. It is shown that by varying the degree of ordering, the thermal conductivity of a binary alloy of fixed composition can be tuned across an order of magnitude at 10% of the melt temperature, and by a factor of three at 40% of the melt temperature. DEWEY : 536 ISSN : 0022-1481 En ligne : http://www.asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO00013400 [...] [article] Controlling thermal conductivity of alloys via atomic ordering [texte imprimé] / John C. Duda, Auteur ; Timothy S. English, Auteur ; Donald A. Jordan, Auteur . - 2012 . - 04 p. Heat transfer Langues : Anglais (eng) in Journal of heat transfer > Vol. 134 N° 1 (Janvier 2012) . - 04 p. Mots-clés : Molecular  dynamics  method  Order-disorder  transformations  Phonons  Solid  solutions  Thermal  conductivity Index. décimale : 536 Chaleur. Thermodynamique Résumé : Many random substitutional solid solutions (alloys) will display a tendency to atomically order given the appropriate kinetic and thermodynamic conditions. Such order–disorder transitions will result in major crystallographic reconfigurations, where the atomic basis, symmetry, and periodicity of the alloy change dramatically. Consequently, phonon behavior in these alloys will vary greatly depending on the type and degree of ordering achieved. To investigate these phenomena, the role of the order–disorder transition on phononic transport properties of Lennard–Jones type binary alloys is explored via nonequilibrium molecular dynamics simulations. Particular attention is paid to regimes in which the alloy is only partially ordered. It is shown that by varying the degree of ordering, the thermal conductivity of a binary alloy of fixed composition can be tuned across an order of magnitude at 10% of the melt temperature, and by a factor of three at 40% of the melt temperature. DEWEY : 536 ISSN : 0022-1481 En ligne : http://www.asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO00013400 [...]

Falling film of ionic liquid-water binary solutions on a uniformly heated vertical wall / Jing Peng in Journal of heat transfer, Vol. 134 N° 1 (Janvier 2012) 

Public ISBD [article]  in Journal of heat transfer > Vol. 134 N° 1 (Janvier 2012) . - 05 p. Titre : Falling film of ionic liquid-water binary solutions on a uniformly heated vertical wall Type de document : texte imprimé Auteurs : Jing Peng, Auteur ; Ming-Ming Wang, Auteur ; Jiao Geng, Auteur Année de publication : 2012 Article en page(s) : 05 p. Note générale : Heat transfer Langues : Anglais (eng) Mots-clés : Boundary  layers  Convection  Film  flow  Flow  visualisation  Organic  compounds  Pattern  formation  Water Index. décimale : 536 Chaleur. Thermodynamique Résumé : The flow characteristics of falling film of amino acid ionic liquid (AAIL) aqueous solution on a uniformly heated vertical plane have been experimentally studied. The infrared images and temperature profiles have been determined and used to analyze the fluid flow. It is proven that the Marangoni effect exists widely and has significant influence on the flow region of falling film. A novel flow pattern is additionally observed when the mass fraction of AAIL is 30%. The flow patterns are also shown to be affected by the wall-liquid temperature differential, the flow rate and the concentration of solute. The experimental results of AAIL falling film are expected to be helpful for the further industrial application of ionic liquids. DEWEY : 536 ISSN : 0022-1481 En ligne : http://www.asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO00013400 [...] [article] Falling film of ionic liquid-water binary solutions on a uniformly heated vertical wall [texte imprimé] / Jing Peng, Auteur ; Ming-Ming Wang, Auteur ; Jiao Geng, Auteur . - 2012 . - 05 p. Heat transfer Langues : Anglais (eng) in Journal of heat transfer > Vol. 134 N° 1 (Janvier 2012) . - 05 p. Mots-clés : Boundary  layers  Convection  Film  flow  Flow  visualisation  Organic  compounds  Pattern  formation  Water Index. décimale : 536 Chaleur. Thermodynamique Résumé : The flow characteristics of falling film of amino acid ionic liquid (AAIL) aqueous solution on a uniformly heated vertical plane have been experimentally studied. The infrared images and temperature profiles have been determined and used to analyze the fluid flow. It is proven that the Marangoni effect exists widely and has significant influence on the flow region of falling film. A novel flow pattern is additionally observed when the mass fraction of AAIL is 30%. The flow patterns are also shown to be affected by the wall-liquid temperature differential, the flow rate and the concentration of solute. The experimental results of AAIL falling film are expected to be helpful for the further industrial application of ionic liquids. DEWEY : 536 ISSN : 0022-1481 En ligne : http://www.asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO00013400 [...]

New correlative models for fully developed turbulent heat and mass transfer in circular and noncircular ducts / Zhipeng Duan in Journal of heat transfer, Vol. 134 N° 1 (Janvier 2012) 

Public ISBD [article]  in Journal of heat transfer > Vol. 134 N° 1 (Janvier 2012) . - 06 p. Titre : New correlative models for fully developed turbulent heat and mass transfer in circular and noncircular ducts Type de document : texte imprimé Auteurs : Zhipeng Duan, Auteur Année de publication : 2012 Article en page(s) : 06 p. Note générale : Heat transfer Langues : Anglais (eng) Mots-clés : Heat  transfer  Mass  transfer  Pipe  flow  Turbulence Index. décimale : 536 Chaleur. Thermodynamique Résumé : Fully developed turbulent flow in noncircular ducts is examined, and simple models are proposed to predict the friction, heat and mass transfer in most common noncircular channels. It is found that the square root of cross-sectional area is the relatively more appropriate length scale to use in defining the dimensionless parameters to ensure similarity between the circular and most noncircular ducts. By using the dimensionless parameters based on the square root of cross-sectional area, it is demonstrated that the circular tube relations may be applied to most noncircular ducts eliminating large errors in estimation. As turbulent transport phenomena are inherently complex and there, currently, is no extensive experimental data for turbulent heat and mass transfer in noncircular ducts, the simple models are valuable in spite of their limitations. DEWEY : 536 ISSN : 0022-1481 En ligne : http://www.asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO00013400 [...] [article] New correlative models for fully developed turbulent heat and mass transfer in circular and noncircular ducts [texte imprimé] / Zhipeng Duan, Auteur . - 2012 . - 06 p. Heat transfer Langues : Anglais (eng) in Journal of heat transfer > Vol. 134 N° 1 (Janvier 2012) . - 06 p. Mots-clés : Heat  transfer  Mass  transfer  Pipe  flow  Turbulence Index. décimale : 536 Chaleur. Thermodynamique Résumé : Fully developed turbulent flow in noncircular ducts is examined, and simple models are proposed to predict the friction, heat and mass transfer in most common noncircular channels. It is found that the square root of cross-sectional area is the relatively more appropriate length scale to use in defining the dimensionless parameters to ensure similarity between the circular and most noncircular ducts. By using the dimensionless parameters based on the square root of cross-sectional area, it is demonstrated that the circular tube relations may be applied to most noncircular ducts eliminating large errors in estimation. As turbulent transport phenomena are inherently complex and there, currently, is no extensive experimental data for turbulent heat and mass transfer in noncircular ducts, the simple models are valuable in spite of their limitations. DEWEY : 536 ISSN : 0022-1481 En ligne : http://www.asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO00013400 [...]

Experimental investigation of a pulsating heat pipe using ferrofluid (magnetic nanofluid) / Maziar Mohammadi in Journal of heat transfer, Vol. 134 N° 1 (Janvier 2012) 

Public ISBD [article]  in Journal of heat transfer > Vol. 134 N° 1 (Janvier 2012) . - 03 p. Titre : Experimental investigation of a pulsating heat pipe using ferrofluid (magnetic nanofluid) Type de document : texte imprimé Auteurs : Maziar Mohammadi, Auteur ; Mohammad Mohammadi, Auteur ; M. B. Shafii, Auteur Année de publication : 2012 Article en page(s) : 03 p. Note générale : Heat transfer Langues : Anglais (eng) Mots-clés : Heat  pipes  Magnetic  fluids  Magnetohydrodynamics  Nanofluidics  Pulsatile  flow  Thermal  resistance Index. décimale : 536 Chaleur. Thermodynamique Résumé : In this work, a four-turn pulsating heat pipe (PHP) is fabricated and tested experimentally. The novelty of the present PHP is the capability to obtain various thermal performances at a specific heat input by changing the magnetic field. The effects of working fluid (water and ferrofluid), charging ratio (40% and 70%), heat input (35, 45, 55, 65, 75, and 85 W), orientation (horizontal and vertical heat mode), ferrofluid volumetric concentration (2.5% and 7%), and magnetic field on the thermal performance of PHPs are investigated. The results showed that applying the magnetic field on the water-based ferrofluid reduced the thermal resistance of PHP in all orientations. In the presence of a magnetic field, the best thermal performance was achieved at the higher charging ratios (70%) in all orientations. DEWEY : 536 ISSN : 0022-1481 En ligne : http://www.asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO00013400 [...] [article] Experimental investigation of a pulsating heat pipe using ferrofluid (magnetic nanofluid) [texte imprimé] / Maziar Mohammadi, Auteur ; Mohammad Mohammadi, Auteur ; M. B. Shafii, Auteur . - 2012 . - 03 p. Heat transfer Langues : Anglais (eng) in Journal of heat transfer > Vol. 134 N° 1 (Janvier 2012) . - 03 p. Mots-clés : Heat  pipes  Magnetic  fluids  Magnetohydrodynamics  Nanofluidics  Pulsatile  flow  Thermal  resistance Index. décimale : 536 Chaleur. Thermodynamique Résumé : In this work, a four-turn pulsating heat pipe (PHP) is fabricated and tested experimentally. The novelty of the present PHP is the capability to obtain various thermal performances at a specific heat input by changing the magnetic field. The effects of working fluid (water and ferrofluid), charging ratio (40% and 70%), heat input (35, 45, 55, 65, 75, and 85 W), orientation (horizontal and vertical heat mode), ferrofluid volumetric concentration (2.5% and 7%), and magnetic field on the thermal performance of PHPs are investigated. The results showed that applying the magnetic field on the water-based ferrofluid reduced the thermal resistance of PHP in all orientations. In the presence of a magnetic field, the best thermal performance was achieved at the higher charging ratios (70%) in all orientations. DEWEY : 536 ISSN : 0022-1481 En ligne : http://www.asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO00013400 [...]

Heat transfer mechanisms during flow boiling in microchannels / M. M. Awad in Journal of heat transfer, Vol. 134 N° 1 (Janvier 2012) 

Public ISBD [article]  in Journal of heat transfer > Vol. 134 N° 1 (Janvier 2012) . - 01 p. Titre : Heat transfer mechanisms during flow boiling in microchannels Type de document : texte imprimé Auteurs : M. M. Awad, Auteur Année de publication : 2012 Article en page(s) : 01 p. Note générale : Heat transfer Langues : Anglais (eng) Mots-clés : Boiling  Heat  transfer  Microchannel  flow Index. décimale : 536 Chaleur. Thermodynamique Note de contenu : Discussion: “Heat Transfer Mechanisms During Flow Boiling in Microchannels” (Kandlikar, S. G., 2004, ASME J. Heat Transfer, 126(1), pp. 8–16) DEWEY : 536 ISSN : 0022-1481 En ligne : http://www.asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO00013400 [...] [article] Heat transfer mechanisms during flow boiling in microchannels [texte imprimé] / M. M. Awad, Auteur . - 2012 . - 01 p. Heat transfer Langues : Anglais (eng) in Journal of heat transfer > Vol. 134 N° 1 (Janvier 2012) . - 01 p. Mots-clés : Boiling  Heat  transfer  Microchannel  flow Index. décimale : 536 Chaleur. Thermodynamique Note de contenu : Discussion: “Heat Transfer Mechanisms During Flow Boiling in Microchannels” (Kandlikar, S. G., 2004, ASME J. Heat Transfer, 126(1), pp. 8–16) DEWEY : 536 ISSN : 0022-1481 En ligne : http://www.asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO00013400 [...]

Heat transfer mechanisms during flow boiling in microchannels / Satish G. Kandlikar in Journal of heat transfer, Vol. 134 N° 1 (Janvier 2012) 

Public ISBD [article]  in Journal of heat transfer > Vol. 134 N° 1 (Janvier 2012) . - 01 p. Titre : Heat transfer mechanisms during flow boiling in microchannels Type de document : texte imprimé Auteurs : Satish G. Kandlikar, Auteur Année de publication : 2012 Article en page(s) : 01 p. Note générale : Heat transfer Langues : Anglais (eng) Mots-clés : Boiling  Contact  angle  Evaporation  Heat  transfer  Microchannel  flow  Surface  tension Index. décimale : 536 Chaleur. Thermodynamique Note de contenu : Closure to “Discussion of `Heat Transfer Mechanisms During Flow Boiling in Microchannels' ” (2012, ASME J. Heat Transfer, 134, p. 015501) DEWEY : 536 ISSN : 0022-1481 En ligne : http://www.asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO00013400 [...] [article] Heat transfer mechanisms during flow boiling in microchannels [texte imprimé] / Satish G. Kandlikar, Auteur . - 2012 . - 01 p. Heat transfer Langues : Anglais (eng) in Journal of heat transfer > Vol. 134 N° 1 (Janvier 2012) . - 01 p. Mots-clés : Boiling  Contact  angle  Evaporation  Heat  transfer  Microchannel  flow  Surface  tension Index. décimale : 536 Chaleur. Thermodynamique Note de contenu : Closure to “Discussion of `Heat Transfer Mechanisms During Flow Boiling in Microchannels' ” (2012, ASME J. Heat Transfer, 134, p. 015501) DEWEY : 536 ISSN : 0022-1481 En ligne : http://www.asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO00013400 [...]

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