Dépouillements

The effect of spatially correlated roughness and boundary conditions on the conduction of heat through a slab / A. F. Emery in Journal of heat transfer, Vol. 132 N° 5 (Mai 2010) 

Public ISBD [article]  in Journal of heat transfer > Vol. 132 N° 5 (Mai 2010) . - pp. [051301-1/11] Titre : The effect of spatially correlated roughness and boundary conditions on the conduction of heat through a slab Type de document : texte imprimé Auteurs : A. F. Emery, Auteur ; H. Dillon, Auteur ; A. M. Mescher, Auteur Article en page(s) : pp. [051301-1/11] Note générale : Physique Langues : Anglais (eng) Mots-clés : Surface  roughness  Correlated  boundary  conditions  Stochastic  conduction  Uncertainty Index. décimale : 536 Chaleur. Thermodynamique Résumé : The nominally one-dimensional conduction of heat through a slab becomes two dimensional when one of the surfaces is rough or when the boundary conditions are spatially nonuniform. This paper develops the stochastic equations for a slab whose surface roughness or convective boundary condition is spatially correlated with correlation lengths ranging from 0 (white noise) to a length long in comparison to the slab thickness. The effect is described in terms of the standard deviation and the resulting spatial correlation of the heat flux as a function of depth into the slab. In contrast to the expectation that the effect is monotonic with respect to the correlation length, it is shown that the effect is maximized at an intermediate correlation length. It is also shown that roughness or a random convective heat transfer coefficient have essentially the same effects on the conducted heat, but that the combination results in a much deeper penetration than does each effect individually. In contrast to the usual methods of solving stochastic problems, both the case of a rough edge and a smooth edge with stochastic convective heat transfer coefficients can only be treated with reasonable computational expense by using direct Monte Carlo simulations. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...] [article] The effect of spatially correlated roughness and boundary conditions on the conduction of heat through a slab [texte imprimé] / A. F. Emery, Auteur ; H. Dillon, Auteur ; A. M. Mescher, Auteur . - pp. [051301-1/11]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 132 N° 5 (Mai 2010) . - pp. [051301-1/11] Mots-clés : Surface  roughness  Correlated  boundary  conditions  Stochastic  conduction  Uncertainty Index. décimale : 536 Chaleur. Thermodynamique Résumé : The nominally one-dimensional conduction of heat through a slab becomes two dimensional when one of the surfaces is rough or when the boundary conditions are spatially nonuniform. This paper develops the stochastic equations for a slab whose surface roughness or convective boundary condition is spatially correlated with correlation lengths ranging from 0 (white noise) to a length long in comparison to the slab thickness. The effect is described in terms of the standard deviation and the resulting spatial correlation of the heat flux as a function of depth into the slab. In contrast to the expectation that the effect is monotonic with respect to the correlation length, it is shown that the effect is maximized at an intermediate correlation length. It is also shown that roughness or a random convective heat transfer coefficient have essentially the same effects on the conducted heat, but that the combination results in a much deeper penetration than does each effect individually. In contrast to the usual methods of solving stochastic problems, both the case of a rough edge and a smooth edge with stochastic convective heat transfer coefficients can only be treated with reasonable computational expense by using direct Monte Carlo simulations. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...]

Self-contained, oscillating flow liquid cooling system for thin form factor high performance electronics / R. Wälchli in Journal of heat transfer, Vol. 132 N° 5 (Mai 2010) 

Public ISBD [article]  in Journal of heat transfer > Vol. 132 N° 5 (Mai 2010) . - pp. [051401-1/7] Titre : Self-contained, oscillating flow liquid cooling system for thin form factor high performance electronics Type de document : texte imprimé Auteurs : R. Wälchli, Auteur ; T. Brunschwiler, Auteur ; B. Michel, Auteur Article en page(s) : pp. [051401-1/7] Note générale : Physique Langues : Anglais (eng) Mots-clés : Microchannel  Liquid  cooling  Thermal  pachaging  Oscillating  flow Index. décimale : 536 Chaleur. Thermodynamique Résumé : A self-contained, small-volume liquid cooling system for thin form-factor electronic equipment (e.g., blade server modules) is demonstrated experimentally in this paper. A reciprocating water flow loop absorbs heat using mesh-type microchannel cold plates and spreads it periodically to a larger area. From there, the thermal energy is interchanged via large area, low pressure drop cold plates with a secondary heat transfer loop (air or liquid). Four phase-shifted piston pumps create either a linearly or radially oscillating fluid flow in the frequency range of 0.5–3 Hz. The tidal displacement of the pumps covers 42–120% of the fluid volume, and, therefore, an average flow rate range of 100–800 ml/min is tested. Three different absorber mesh designs are tested. Thermal and fluidic characteristics are presented in a time-resolved and a time-averaged manner. For a fluid pump power of 1 W, a waste heat flux of 180 W/cm2 (DeltaT=67 K) could be dissipated from a 3.5 cm2 chip. A linear oscillation flow pattern is advantageous over a radial one because of the more efficient heat removal from the chip and lower hydraulic losses. The optimum microchannel mesh density is determined as a combination of low pump losses and high heat transfer rates. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...] [article] Self-contained, oscillating flow liquid cooling system for thin form factor high performance electronics [texte imprimé] / R. Wälchli, Auteur ; T. Brunschwiler, Auteur ; B. Michel, Auteur . - pp. [051401-1/7]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 132 N° 5 (Mai 2010) . - pp. [051401-1/7] Mots-clés : Microchannel  Liquid  cooling  Thermal  pachaging  Oscillating  flow Index. décimale : 536 Chaleur. Thermodynamique Résumé : A self-contained, small-volume liquid cooling system for thin form-factor electronic equipment (e.g., blade server modules) is demonstrated experimentally in this paper. A reciprocating water flow loop absorbs heat using mesh-type microchannel cold plates and spreads it periodically to a larger area. From there, the thermal energy is interchanged via large area, low pressure drop cold plates with a secondary heat transfer loop (air or liquid). Four phase-shifted piston pumps create either a linearly or radially oscillating fluid flow in the frequency range of 0.5–3 Hz. The tidal displacement of the pumps covers 42–120% of the fluid volume, and, therefore, an average flow rate range of 100–800 ml/min is tested. Three different absorber mesh designs are tested. Thermal and fluidic characteristics are presented in a time-resolved and a time-averaged manner. For a fluid pump power of 1 W, a waste heat flux of 180 W/cm2 (DeltaT=67 K) could be dissipated from a 3.5 cm2 chip. A linear oscillation flow pattern is advantageous over a radial one because of the more efficient heat removal from the chip and lower hydraulic losses. The optimum microchannel mesh density is determined as a combination of low pump losses and high heat transfer rates. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...]

The effect of the angle of inclination on the operation limiting heat flux of long R-134a filled thermosyphons / M. H. M. Grooten in Journal of heat transfer, Vol. 132 N° 5 (Mai 2010) 

Public ISBD [article]  in Journal of heat transfer > Vol. 132 N° 5 (Mai 2010) . - pp. [051501-1/5] Titre : The effect of the angle of inclination on the operation limiting heat flux of long R-134a filled thermosyphons Type de document : texte imprimé Auteurs : M. H. M. Grooten, Auteur ; C. W. M. Van Der Geld, Auteur Article en page(s) : pp. [051501-1/5] Note générale : Physique Langues : Anglais (eng) Mots-clés : Heat  pipes  Thermosyphon  Heat  exchangers  R-134a  Limiting  heat  flux Index. décimale : 536 Chaleur. Thermodynamique Résumé : When traditional air-to-air cooling is too voluminous, long thermosyphons may offer a way out. For safe operation of heat exchangers equipped with thermosyphons, the limiting heat flux qlim[double-prime] is an important design parameter. Some literatures are found to deal with the operation limiting heat flux of closed two-phase thermosyphons. However, R-134a filled thermosyphons with large length-to-diameter (188) are hardly investigated up to now. Extrapolation of existing correlations to predict qlim[double-prime] in this case results in large scatter. The effect of the angle of inclination on qlim[double-prime] has not been considered until now. Dedicated experiments with a single thermosyphon with a large length-to-diameter ratio (188) and filled with R-134a are presented and analyzed. Effects of saturation temperature, filling ratio, and angle of inclination beta on the operational limiting heat flux have been investigated. The thermosyphon functions properly if beta<83 deg, and qlim[double-prime] is found to increase with increasing beta. With decreasing saturation temperature, qlim[double-prime] increases. The filling ratio is found not to be crucial if it exceeds 25%. Correlations are presented to accurately predict the operation limiting heat flux for thermosyphons with a L/d ratio up to 188. Because of the accounting for the above new aspects, these correlations are also relevant for filling refrigerants other than R-134a. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...] [article] The effect of the angle of inclination on the operation limiting heat flux of long R-134a filled thermosyphons [texte imprimé] / M. H. M. Grooten, Auteur ; C. W. M. Van Der Geld, Auteur . - pp. [051501-1/5]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 132 N° 5 (Mai 2010) . - pp. [051501-1/5] Mots-clés : Heat  pipes  Thermosyphon  Heat  exchangers  R-134a  Limiting  heat  flux Index. décimale : 536 Chaleur. Thermodynamique Résumé : When traditional air-to-air cooling is too voluminous, long thermosyphons may offer a way out. For safe operation of heat exchangers equipped with thermosyphons, the limiting heat flux qlim[double-prime] is an important design parameter. Some literatures are found to deal with the operation limiting heat flux of closed two-phase thermosyphons. However, R-134a filled thermosyphons with large length-to-diameter (188) are hardly investigated up to now. Extrapolation of existing correlations to predict qlim[double-prime] in this case results in large scatter. The effect of the angle of inclination on qlim[double-prime] has not been considered until now. Dedicated experiments with a single thermosyphon with a large length-to-diameter ratio (188) and filled with R-134a are presented and analyzed. Effects of saturation temperature, filling ratio, and angle of inclination beta on the operational limiting heat flux have been investigated. The thermosyphon functions properly if beta<83 deg, and qlim[double-prime] is found to increase with increasing beta. With decreasing saturation temperature, qlim[double-prime] increases. The filling ratio is found not to be crucial if it exceeds 25%. Correlations are presented to accurately predict the operation limiting heat flux for thermosyphons with a L/d ratio up to 188. Because of the accounting for the above new aspects, these correlations are also relevant for filling refrigerants other than R-134a. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...]

A phase-sensitive technique for measurements of liquid thermal conductivity / Zhefu Wang in Journal of heat transfer, Vol. 132 N° 5 (Mai 2010) 

Public ISBD [article]  in Journal of heat transfer > Vol. 132 N° 5 (Mai 2010) . - pp. [051601-1/8] Titre : A phase-sensitive technique for measurements of liquid thermal conductivity Type de document : texte imprimé Auteurs : Zhefu Wang, Auteur ; Richard B. Peterson, Auteur Article en page(s) : pp. [051601-1/8] Note générale : Physique Langues : Anglais (eng) Mots-clés : Heat  conduction  Measurement  techniques  Thermal  properties  Phase  detection  nanofluids Index. décimale : 536 Chaleur. Thermodynamique Résumé : An experimental technique based on the thermal wave approach for measuring the thermal conductivity of liquids is developed in this paper. A stainless steel strip functions as both a heating element and a sealing cover for a chamber containing a test liquid. A periodic current passing through this metal strip generates a periodic Joule heating source. An infrared detector measures the temperature response at the front surface of the stainless steel strip. The phase and magnitude of the temperature response with respect to the heating signal were measured by a lock-in amplifier at various frequencies from 22 Hz to 502 Hz. A one-dimensional, two-layered transient heat conduction model was developed to predict the temperature response on the front surface of the stainless steel strip. The phase information from this temperature response shows high sensitivity to the change in thermal properties of the liquid layer and is employed to match experimental data to find the thermal properties of the test liquid. The measured thermal conductivities of water and ethylene glycol agree quite well with the data from literature and support the validity of this measurement technique. An aqueous fluid consisting of gold nanoparticles is tested and anomalous thermal conductivity enhancement is observed. A discrepancy in the thermal transport behavior between pure liquids and nanofluids is suggested from our experimental results. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...] [article] A phase-sensitive technique for measurements of liquid thermal conductivity [texte imprimé] / Zhefu Wang, Auteur ; Richard B. Peterson, Auteur . - pp. [051601-1/8]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 132 N° 5 (Mai 2010) . - pp. [051601-1/8] Mots-clés : Heat  conduction  Measurement  techniques  Thermal  properties  Phase  detection  nanofluids Index. décimale : 536 Chaleur. Thermodynamique Résumé : An experimental technique based on the thermal wave approach for measuring the thermal conductivity of liquids is developed in this paper. A stainless steel strip functions as both a heating element and a sealing cover for a chamber containing a test liquid. A periodic current passing through this metal strip generates a periodic Joule heating source. An infrared detector measures the temperature response at the front surface of the stainless steel strip. The phase and magnitude of the temperature response with respect to the heating signal were measured by a lock-in amplifier at various frequencies from 22 Hz to 502 Hz. A one-dimensional, two-layered transient heat conduction model was developed to predict the temperature response on the front surface of the stainless steel strip. The phase information from this temperature response shows high sensitivity to the change in thermal properties of the liquid layer and is employed to match experimental data to find the thermal properties of the test liquid. The measured thermal conductivities of water and ethylene glycol agree quite well with the data from literature and support the validity of this measurement technique. An aqueous fluid consisting of gold nanoparticles is tested and anomalous thermal conductivity enhancement is observed. A discrepancy in the thermal transport behavior between pure liquids and nanofluids is suggested from our experimental results. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...]

Temperature measurements of diesel fuel combustion with multicolor pyrometry / Tairan Fu in Journal of heat transfer, Vol. 132 N° 5 (Mai 2010) 

Public ISBD [article]  in Journal of heat transfer > Vol. 132 N° 5 (Mai 2010) . - pp. [051602-1/7] Titre : Temperature measurements of diesel fuel combustion with multicolor pyrometry Type de document : texte imprimé Auteurs : Tairan Fu, Auteur ; Zhe Wang, Auteur ; Xiaofang Cheng, Auteur Article en page(s) : pp. [051602-1/7] Note générale : Physique Langues : Anglais (eng) Mots-clés : Temperature  pyrometry  Optical  diagnostics  Diesel  combustion  flame Index. décimale : 536 Chaleur. Thermodynamique Résumé : Optical diagnostics techniques to measure diesel combustion flame temperatures are useful for evaluation and control of combustion processes. In this paper, diesel combustion flame temperatures are measured based on a multicolor pyrometry method respectively adopting an optical fiber spectrometer and a color charge coupled device (CCD). The intensity ratios for various wavelengths/wavebands are utilized as the analytical variables to deduce the temperatures to avoid the need to calibrate each system for the specific geometry conditions. The measured multicolor data can determine the temperature T and the soot factor KL. Extra data collected at many wavelengths is used to reduce the noise and random fluctuations in the measurements. To improve the solving precision, a data-processing method based on the least-squares technique is proposed to fit the data for approximate solutions. Verification experiments using the multicolor pyrometry were conducted in a 54–120 kW test furnace with diesel fuel. Data for 16 wavelengths detected by a fiber optic spectrometer from a diesel flame is analyzed to determine how to choose a suitable combination of three wavelengths for three-color pyrometry. The CCD-based three-color measurements, which would be much more practical in field measurements, are compared with the spectrometer-based results. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...] [article] Temperature measurements of diesel fuel combustion with multicolor pyrometry [texte imprimé] / Tairan Fu, Auteur ; Zhe Wang, Auteur ; Xiaofang Cheng, Auteur . - pp. [051602-1/7]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 132 N° 5 (Mai 2010) . - pp. [051602-1/7] Mots-clés : Temperature  pyrometry  Optical  diagnostics  Diesel  combustion  flame Index. décimale : 536 Chaleur. Thermodynamique Résumé : Optical diagnostics techniques to measure diesel combustion flame temperatures are useful for evaluation and control of combustion processes. In this paper, diesel combustion flame temperatures are measured based on a multicolor pyrometry method respectively adopting an optical fiber spectrometer and a color charge coupled device (CCD). The intensity ratios for various wavelengths/wavebands are utilized as the analytical variables to deduce the temperatures to avoid the need to calibrate each system for the specific geometry conditions. The measured multicolor data can determine the temperature T and the soot factor KL. Extra data collected at many wavelengths is used to reduce the noise and random fluctuations in the measurements. To improve the solving precision, a data-processing method based on the least-squares technique is proposed to fit the data for approximate solutions. Verification experiments using the multicolor pyrometry were conducted in a 54–120 kW test furnace with diesel fuel. Data for 16 wavelengths detected by a fiber optic spectrometer from a diesel flame is analyzed to determine how to choose a suitable combination of three wavelengths for three-color pyrometry. The CCD-based three-color measurements, which would be much more practical in field measurements, are compared with the spectrometer-based results. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...]

Superior convective heat transport for laminar boundary layer flow over a flat plate using binary gas mixtures with light helium and selected heavier gases / Antonio Campo in Journal of heat transfer, Vol. 132 N° 5 (Mai 2010) 

Public ISBD [article]  in Journal of heat transfer > Vol. 132 N° 5 (Mai 2010) . - pp. [051701-1/9] Titre : Superior convective heat transport for laminar boundary layer flow over a flat plate using binary gas mixtures with light helium and selected heavier gases Type de document : texte imprimé Auteurs : Antonio Campo, Auteur ; Chikh, Salah, Auteur ; Mohammad M. Papari, Auteur Article en page(s) : pp. [051701-1/9] Note générale : Physique Langues : Anglais (eng) Mots-clés : Boundary  layer  flow  Helium  gas  Binary  gas  mixtures  Heat  transfer  enhancement Index. décimale : 536 Chaleur. Thermodynamique Résumé : This paper addresses the laminar boundary layer flow of certain binary gas mixtures along a heated flat plate. To form the binary gas mixtures, light helium (He) is the primary gas and the heavier secondary gases are nitrogen (N2), oxygen (O2), xenon (Xe), carbon dioxide (CO2), methane (CH4), tetrafluoromethane (CF4), and sulfur hexafluoride (SF6). The central objective of this paper is to investigate the potential of this group of binary gas mixtures for heat transfer intensification. From fluid physics, two thermophysical properties, i.e., viscosity eta and density rho, influence the fluid flow, whereas four thermophysical properties, i.e., viscosity eta, thermal conductivity lambda, density rho, and heat capacity at constant pressure Cp, affect the forced convective heat transfer. The heat transfer augmentation from the flat plate is pursued by stimulating the forced convection mode as a whole. In this regard, it became necessary to construct a specific correlation equation to handle binary gas mixtures owing Prandtl number Pr[is-an-element-of](0.1,1). Whenever there is heat transfer invigoration in forced flow, drag force accretion seems to be inevitable. A standard formula for estimating the drag force Fd exerted on the flat plate is available from the fluid dynamics literature. The descriptive equations for the heat transfer rate Qmix and drag force Fd,mix associated with the seven binary gas mixtures are channeled through the four thermophysical properties, i.e., density rhomix, viscosity etamix, thermal conductivity lambdamix, and heat capacity at constant pressure Cp,mix, which depend on the molar gas composition w. Two case studies suffice to elucidate the modified convective heat and momentum transport that the binary gas mixtures bring forward. At a film temperature Tf=300 K and 1 atm, the He+SF6 mixture delivers the absolute maximum for the relative heat transfer Qmix,abs max/B=16.71 at an optimal molar gas composition wopt=0.96. When compared with the light primary He gas with a relative heat transfer rate QHe/B=12.04, the He+SF6 mixture generates a significant heat transfer enhancement of 39%. At a film temperature Tf=600 K and the same 1 atm, the relative heat transfer QHe/B for the light primary gas He comes down to 10.77. In reference to this, the He+SF6 mixture furnishes an absolute maximum heat transfer Qmix,abs max/B=18.11 at an optimal molar gas composition wopt=0.96, yielding a remarkable heat transfer enhancement of 68%. In the global context, the usage of exotic binary gas mixtures with light helium and selected heavier gases may be envisioned for special tasks in industries that demand high heat transfer rates. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...] [article] Superior convective heat transport for laminar boundary layer flow over a flat plate using binary gas mixtures with light helium and selected heavier gases [texte imprimé] / Antonio Campo, Auteur ; Chikh, Salah, Auteur ; Mohammad M. Papari, Auteur . - pp. [051701-1/9]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 132 N° 5 (Mai 2010) . - pp. [051701-1/9] Mots-clés : Boundary  layer  flow  Helium  gas  Binary  gas  mixtures  Heat  transfer  enhancement Index. décimale : 536 Chaleur. Thermodynamique Résumé : This paper addresses the laminar boundary layer flow of certain binary gas mixtures along a heated flat plate. To form the binary gas mixtures, light helium (He) is the primary gas and the heavier secondary gases are nitrogen (N2), oxygen (O2), xenon (Xe), carbon dioxide (CO2), methane (CH4), tetrafluoromethane (CF4), and sulfur hexafluoride (SF6). The central objective of this paper is to investigate the potential of this group of binary gas mixtures for heat transfer intensification. From fluid physics, two thermophysical properties, i.e., viscosity eta and density rho, influence the fluid flow, whereas four thermophysical properties, i.e., viscosity eta, thermal conductivity lambda, density rho, and heat capacity at constant pressure Cp, affect the forced convective heat transfer. The heat transfer augmentation from the flat plate is pursued by stimulating the forced convection mode as a whole. In this regard, it became necessary to construct a specific correlation equation to handle binary gas mixtures owing Prandtl number Pr[is-an-element-of](0.1,1). Whenever there is heat transfer invigoration in forced flow, drag force accretion seems to be inevitable. A standard formula for estimating the drag force Fd exerted on the flat plate is available from the fluid dynamics literature. The descriptive equations for the heat transfer rate Qmix and drag force Fd,mix associated with the seven binary gas mixtures are channeled through the four thermophysical properties, i.e., density rhomix, viscosity etamix, thermal conductivity lambdamix, and heat capacity at constant pressure Cp,mix, which depend on the molar gas composition w. Two case studies suffice to elucidate the modified convective heat and momentum transport that the binary gas mixtures bring forward. At a film temperature Tf=300 K and 1 atm, the He+SF6 mixture delivers the absolute maximum for the relative heat transfer Qmix,abs max/B=16.71 at an optimal molar gas composition wopt=0.96. When compared with the light primary He gas with a relative heat transfer rate QHe/B=12.04, the He+SF6 mixture generates a significant heat transfer enhancement of 39%. At a film temperature Tf=600 K and the same 1 atm, the relative heat transfer QHe/B for the light primary gas He comes down to 10.77. In reference to this, the He+SF6 mixture furnishes an absolute maximum heat transfer Qmix,abs max/B=18.11 at an optimal molar gas composition wopt=0.96, yielding a remarkable heat transfer enhancement of 68%. In the global context, the usage of exotic binary gas mixtures with light helium and selected heavier gases may be envisioned for special tasks in industries that demand high heat transfer rates. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...]

Forced convection heat transfer enhancement by porous pin fins in rectangular channels / Jian Yang in Journal of heat transfer, Vol. 132 N° 5 (Mai 2010) 

Public ISBD [article]  in Journal of heat transfer > Vol. 132 N° 5 (Mai 2010) . - pp. [051702-1/8] Titre : Forced convection heat transfer enhancement by porous pin fins in rectangular channels Type de document : texte imprimé Auteurs : Jian Yang, Auteur ; Min Zeng, Auteur ; Qiuwang Wang, Auteur Article en page(s) : pp. [051702-1/8] Note générale : Physique Langues : Anglais (eng) Mots-clés : Porous  pin  fun  channel  Forced  convection  Heat  transfer  enhancement  CFD  simulation Index. décimale : 536 Chaleur. Thermodynamique Résumé : The forced convective heat transfer in three-dimensional porous pin fin channels is numerically studied in this paper. The Forchheimer–Brinkman extended Darcy model and two-equation energy model are adopted to describe the flow and heat transfer in porous media. Air and water are employed as the cold fluids and the effects of Reynolds number (Re), pore density (PPI) and pin fin form are studied in detail. The results show that, with proper selection of physical parameters, significant heat transfer enhancements and pressure drop reductions can be achieved simultaneously with porous pin fins and the overall heat transfer performances in porous pin fin channels are much better than those in traditional solid pin fin channels. The effects of pore density are significant. As PPI increases, the pressure drops and heat fluxes in porous pin fin channels increase while the overall heat transfer efficiencies decrease and the maximal overall heat transfer efficiencies are obtained at PPI=20 for both air and water cases. Furthermore, the effects of pin fin form are also remarkable. With the same physical parameters, the overall heat transfer efficiencies in the long elliptic porous pin fin channels are the highest while they are the lowest in the short elliptic porous pin fin channels. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...] [article] Forced convection heat transfer enhancement by porous pin fins in rectangular channels [texte imprimé] / Jian Yang, Auteur ; Min Zeng, Auteur ; Qiuwang Wang, Auteur . - pp. [051702-1/8]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 132 N° 5 (Mai 2010) . - pp. [051702-1/8] Mots-clés : Porous  pin  fun  channel  Forced  convection  Heat  transfer  enhancement  CFD  simulation Index. décimale : 536 Chaleur. Thermodynamique Résumé : The forced convective heat transfer in three-dimensional porous pin fin channels is numerically studied in this paper. The Forchheimer–Brinkman extended Darcy model and two-equation energy model are adopted to describe the flow and heat transfer in porous media. Air and water are employed as the cold fluids and the effects of Reynolds number (Re), pore density (PPI) and pin fin form are studied in detail. The results show that, with proper selection of physical parameters, significant heat transfer enhancements and pressure drop reductions can be achieved simultaneously with porous pin fins and the overall heat transfer performances in porous pin fin channels are much better than those in traditional solid pin fin channels. The effects of pore density are significant. As PPI increases, the pressure drops and heat fluxes in porous pin fin channels increase while the overall heat transfer efficiencies decrease and the maximal overall heat transfer efficiencies are obtained at PPI=20 for both air and water cases. Furthermore, the effects of pin fin form are also remarkable. With the same physical parameters, the overall heat transfer efficiencies in the long elliptic porous pin fin channels are the highest while they are the lowest in the short elliptic porous pin fin channels. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...]

Modeling the effects of system rotation on the turbulent scalar fluxes / B. A. Younis in Journal of heat transfer, Vol. 132 N° 5 (Mai 2010) 

Public ISBD [article]  in Journal of heat transfer > Vol. 132 N° 5 (Mai 2010) . - pp. [051703-1/14] Titre : Modeling the effects of system rotation on the turbulent scalar fluxes Type de document : texte imprimé Auteurs : B. A. Younis, Auteur ; B. Weigand, Auteur ; F. Mohr, Auteur Article en page(s) : pp. [051703-1/14] Note générale : Physique Langues : Anglais (eng) Mots-clés : Channel  flow  Flow  simulation  Rotational  flow  Turbulence Index. décimale : 536 Chaleur. Thermodynamique Résumé : A proposal for modeling the effects of system rotation on the turbulent scalar fluxes is presented. It is based on extension to rotating frames of an explicit algebraic model derived using tensor-representation theory. The model is formulated to allow for the turbulent scalar fluxes to depend on the details of the turbulence field and on the gradients of both the mean-velocity and the scalar. Such dependence, which is absent from conventional models, is required by the exact equations governing the transport of the scalar fluxes. The model's performance is assessed, both a priori and by actual computations, by comparisons with results from recent direct numerical simulations (DNS) of flows in heated channels rotated about their streamwise, spanwise, and wall-normal axes. To place the new model's performance in context, additional comparisons are made with predictions obtained from three alternative models, namely, the conventional gradient-transport model, a model that is implicit in the scalar fluxes derived by simplification of the modeled transport equations for the scalar fluxes, and a differential scalar-flux transport model. The results show that the present model yields predictions that are substantially in better agreement with the DNS results than the algebraic models, and which are indistinguishable from those obtained with the more complex differential model. However, important differences remain and reasons for these are discussed. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...] [article] Modeling the effects of system rotation on the turbulent scalar fluxes [texte imprimé] / B. A. Younis, Auteur ; B. Weigand, Auteur ; F. Mohr, Auteur . - pp. [051703-1/14]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 132 N° 5 (Mai 2010) . - pp. [051703-1/14] Mots-clés : Channel  flow  Flow  simulation  Rotational  flow  Turbulence Index. décimale : 536 Chaleur. Thermodynamique Résumé : A proposal for modeling the effects of system rotation on the turbulent scalar fluxes is presented. It is based on extension to rotating frames of an explicit algebraic model derived using tensor-representation theory. The model is formulated to allow for the turbulent scalar fluxes to depend on the details of the turbulence field and on the gradients of both the mean-velocity and the scalar. Such dependence, which is absent from conventional models, is required by the exact equations governing the transport of the scalar fluxes. The model's performance is assessed, both a priori and by actual computations, by comparisons with results from recent direct numerical simulations (DNS) of flows in heated channels rotated about their streamwise, spanwise, and wall-normal axes. To place the new model's performance in context, additional comparisons are made with predictions obtained from three alternative models, namely, the conventional gradient-transport model, a model that is implicit in the scalar fluxes derived by simplification of the modeled transport equations for the scalar fluxes, and a differential scalar-flux transport model. The results show that the present model yields predictions that are substantially in better agreement with the DNS results than the algebraic models, and which are indistinguishable from those obtained with the more complex differential model. However, important differences remain and reasons for these are discussed. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...]

Computational fluid dynamics evaluation of heat transfer correlations for sodium flows in a heat exchanger / Seok-Ki Choi in Journal of heat transfer, Vol. 132 N° 5 (Mai 2010) 

Public ISBD [article]  in Journal of heat transfer > Vol. 132 N° 5 (Mai 2010) . - pp. [051801-1/6] Titre : Computational fluid dynamics evaluation of heat transfer correlations for sodium flows in a heat exchanger Type de document : texte imprimé Auteurs : Seok-Ki Choi, Auteur ; Seong-O Kim, Auteur ; Hoon-Ki Choi, Auteur Article en page(s) : pp. [051801-1/6] Note générale : Physique Langues : Anglais (eng) Mots-clés : Computational  fluid  dynamics  Heat  exchangers  Heat  transfer  Pipe  flow  Sodium  Turbulence Index. décimale : 536 Chaleur. Thermodynamique Résumé : A numerical study for the evaluation of heat transfer correlations for sodium flows in a heat exchanger of a fast breeder nuclear reactor is performed. Three different types of flows such as parallel flow, cross flow, and two inclined flows are considered. Calculations are performed for these three typical flows in a heat exchanger changing turbulence models. The tested turbulence models are the shear stress transport (SST) model and the SSG-Reynolds stress turbulence model by Speziale, Sarkar, and Gaski (1991, “Modelling the Pressure-Strain Correlation of Turbulence: An Invariant Dynamical System Approach,” J. Fluid Mech., 227, pp. 245–272). The computational model for parallel flow is a flow past tubes inside a circular cylinder and those for the cross flow and inclined flows are flows past the perpendicular and inclined tube banks enclosed by a rectangular duct. The computational results show that the SST model produces the most reliable results that can distinguish the best heat transfer correlation from other correlations for the three different flows. It was also shown that the SSG-RSTM high-Reynolds number turbulence model does not deal with the low-Prandtl number effect properly when the Peclet number is small. According to the present calculations for a parallel flow, all the old correlations do not match with the present numerical solutions and a new correlation is proposed. The correlations by Dwyer (1966, “Recent Developments in Liquid-Metal Heat Transfer,” At. Energy Rev., 4, pp. 3–92) for a cross flow and its modified correlation that takes into account of flow inclination for inclined flows work best and are accurate enough to be used for the design of the heat exchanger. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...] [article] Computational fluid dynamics evaluation of heat transfer correlations for sodium flows in a heat exchanger [texte imprimé] / Seok-Ki Choi, Auteur ; Seong-O Kim, Auteur ; Hoon-Ki Choi, Auteur . - pp. [051801-1/6]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 132 N° 5 (Mai 2010) . - pp. [051801-1/6] Mots-clés : Computational  fluid  dynamics  Heat  exchangers  Heat  transfer  Pipe  flow  Sodium  Turbulence Index. décimale : 536 Chaleur. Thermodynamique Résumé : A numerical study for the evaluation of heat transfer correlations for sodium flows in a heat exchanger of a fast breeder nuclear reactor is performed. Three different types of flows such as parallel flow, cross flow, and two inclined flows are considered. Calculations are performed for these three typical flows in a heat exchanger changing turbulence models. The tested turbulence models are the shear stress transport (SST) model and the SSG-Reynolds stress turbulence model by Speziale, Sarkar, and Gaski (1991, “Modelling the Pressure-Strain Correlation of Turbulence: An Invariant Dynamical System Approach,” J. Fluid Mech., 227, pp. 245–272). The computational model for parallel flow is a flow past tubes inside a circular cylinder and those for the cross flow and inclined flows are flows past the perpendicular and inclined tube banks enclosed by a rectangular duct. The computational results show that the SST model produces the most reliable results that can distinguish the best heat transfer correlation from other correlations for the three different flows. It was also shown that the SSG-RSTM high-Reynolds number turbulence model does not deal with the low-Prandtl number effect properly when the Peclet number is small. According to the present calculations for a parallel flow, all the old correlations do not match with the present numerical solutions and a new correlation is proposed. The correlations by Dwyer (1966, “Recent Developments in Liquid-Metal Heat Transfer,” At. Energy Rev., 4, pp. 3–92) for a cross flow and its modified correlation that takes into account of flow inclination for inclined flows work best and are accurate enough to be used for the design of the heat exchanger. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...]

A design and rating method for shell-and-tube heat exchangers with helical baffles / Jian-Fei Zhang in Journal of heat transfer, Vol. 132 N° 5 (Mai 2010) 

Public ISBD [article]  in Journal of heat transfer > Vol. 132 N° 5 (Mai 2010) . - pp. [051802-1/8] Titre : A design and rating method for shell-and-tube heat exchangers with helical baffles Type de document : texte imprimé Auteurs : Jian-Fei Zhang, Auteur ; Ya-Ling He, Auteur ; Wen-Quan Tao, Auteur Article en page(s) : pp. [051802-1/8] Note générale : Physique Langues : Anglais (eng) Mots-clés : Shell-and-tube  heat  exchanger  Helical  baffe  Pressure  drop  Heat  transfer  Design  and  rating  method Index. décimale : 536 Chaleur. Thermodynamique Résumé : A method for design and rating of shell-and-tube heat exchanger with helical baffles (STHXHB) has been developed in present study based on the public literatures and the widely used Bell–Delaware method for shell-and-tube heat exchanger with segmental baffles (STHXSB). A number of curve-type factors in the literature have all been replaced by mathematical expressions for the convenience of engineering design. The detailed calculation procedure of the method is provided. The accuracy of present method is validated with some experimental data. Four design cases of replacing original STHXsSB by STHXsHB are supplied, and the comparison results show that all of the STHXsHB have better performance than the original heat exchangers with segmental baffles. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...] [article] A design and rating method for shell-and-tube heat exchangers with helical baffles [texte imprimé] / Jian-Fei Zhang, Auteur ; Ya-Ling He, Auteur ; Wen-Quan Tao, Auteur . - pp. [051802-1/8]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 132 N° 5 (Mai 2010) . - pp. [051802-1/8] Mots-clés : Shell-and-tube  heat  exchanger  Helical  baffe  Pressure  drop  Heat  transfer  Design  and  rating  method Index. décimale : 536 Chaleur. Thermodynamique Résumé : A method for design and rating of shell-and-tube heat exchanger with helical baffles (STHXHB) has been developed in present study based on the public literatures and the widely used Bell–Delaware method for shell-and-tube heat exchanger with segmental baffles (STHXSB). A number of curve-type factors in the literature have all been replaced by mathematical expressions for the convenience of engineering design. The detailed calculation procedure of the method is provided. The accuracy of present method is validated with some experimental data. Four design cases of replacing original STHXsSB by STHXsHB are supplied, and the comparison results show that all of the STHXsHB have better performance than the original heat exchangers with segmental baffles. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...]

Inverse determination of eroded smelter wall thickness variation using an elastic membrane concept / Daniel Baker in Journal of heat transfer, Vol. 132 N° 5 (Mai 2010) 

Public ISBD [article]  in Journal of heat transfer > Vol. 132 N° 5 (Mai 2010) . - pp. [052101-1/8] Titre : Inverse determination of eroded smelter wall thickness variation using an elastic membrane concept Type de document : texte imprimé Auteurs : Daniel Baker, Auteur ; George S. Dulikravich, Auteur ; Brian H. Dennis, Auteur Article en page(s) : pp. [052101-1/8] Note générale : Physique Langues : Anglais (eng) Mots-clés : Inverse  problems  Shape  determination  Refractory  wall  Wall  erosion  Shape  design  Hearth  wear Index. décimale : 536 Chaleur. Thermodynamique Résumé : A novel algorithm has been developed for the nondestructive determination of the shape of the interface between a melt and a refractory material wall in smelter furnaces. This method uses measurements of temperature and heat flux at a number of points on the outer surface of the furnace, and assumes that the inner (guessed) surface of the furnace wall is isothermal. The temperature field is then predicted in the entire furnace wall material by numerically solving a steady state heat conduction equation subject to the measured temperature values on the external surface and the isothermal melt material solidus temperature on the inner surface of the wall. The byproduct of this analysis is the computed heat flux on the external surface. The difference between the measured and the computed heat fluxes on the outer surface of the furnace is then used as a forcing function in an elastic membrane motion concept to determine perturbations to the inner (melt-refractory) surface motion. The inverse determination of the melt-refractory interface shape can be achieved by utilizing this algorithm and any available analysis software for the temperature field in the refractory wall. The initial guess of the inner shape of the wall can be significantly different from the final (unknown) wall shape. The entire wall shape determination procedure requires typically 5–15 temperature field analyses in the furnace wall material. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...] [article] Inverse determination of eroded smelter wall thickness variation using an elastic membrane concept [texte imprimé] / Daniel Baker, Auteur ; George S. Dulikravich, Auteur ; Brian H. Dennis, Auteur . - pp. [052101-1/8]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 132 N° 5 (Mai 2010) . - pp. [052101-1/8] Mots-clés : Inverse  problems  Shape  determination  Refractory  wall  Wall  erosion  Shape  design  Hearth  wear Index. décimale : 536 Chaleur. Thermodynamique Résumé : A novel algorithm has been developed for the nondestructive determination of the shape of the interface between a melt and a refractory material wall in smelter furnaces. This method uses measurements of temperature and heat flux at a number of points on the outer surface of the furnace, and assumes that the inner (guessed) surface of the furnace wall is isothermal. The temperature field is then predicted in the entire furnace wall material by numerically solving a steady state heat conduction equation subject to the measured temperature values on the external surface and the isothermal melt material solidus temperature on the inner surface of the wall. The byproduct of this analysis is the computed heat flux on the external surface. The difference between the measured and the computed heat fluxes on the outer surface of the furnace is then used as a forcing function in an elastic membrane motion concept to determine perturbations to the inner (melt-refractory) surface motion. The inverse determination of the melt-refractory interface shape can be achieved by utilizing this algorithm and any available analysis software for the temperature field in the refractory wall. The initial guess of the inner shape of the wall can be significantly different from the final (unknown) wall shape. The entire wall shape determination procedure requires typically 5–15 temperature field analyses in the furnace wall material. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...]

Numerical simulation of transient thermal transport on a rotating disk under partially confined laminar liquid jet impingement / Jorge C. Lallave in Journal of heat transfer, Vol. 132 N° 5 (Mai 2010) 

Public ISBD [article]  in Journal of heat transfer > Vol. 132 N° 5 (Mai 2010) . - pp. [052201-1/8] Titre : Numerical simulation of transient thermal transport on a rotating disk under partially confined laminar liquid jet impingement Type de document : texte imprimé Auteurs : Jorge C. Lallave, Auteur ; Muhammad M. Rahman, Auteur Article en page(s) : pp. [052201-1/8] Note générale : Physique Langues : Anglais (eng) Mots-clés : Partially  confined  liquid  jet  impingement  Transeint  conjugate  transfer  Rotating  disk Index. décimale : 536 Chaleur. Thermodynamique Résumé : This paper considers the transient conjugate heat transfer characterization of a partially confined liquid jet impinging on a rotating and uniformly heated solid disk of finite thickness and radius. A constant heat flux was imposed at the bottom surface of the solid disk at t=0, and heat transfer was monitored for the entire duration of the transient until the steady state condition was reached. Calculations were done for a number of disk materials using water as the coolant, covering a range of Reynolds numbers (225–900), Ekman numbers (7.08×10−5−[infinity]), nozzle-to-target spacing (beta=0.25–1.0), confinement ratios (rp/rd=0.2–0.75), disk thicknesses to nozzle diameter ratios (b/dn=0.25–1.67), and solid to fluid thermal conductivity ratios (36.91–697.56). It was found that a higher Reynolds number decreases the time to achieve the steady state condition and increases the local and average Nusselt number. The duration of the transient increases with the increment of the Ekman number and disk thickness, and the reduction in the thermal diffusivity of the disk material. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...] [article] Numerical simulation of transient thermal transport on a rotating disk under partially confined laminar liquid jet impingement [texte imprimé] / Jorge C. Lallave, Auteur ; Muhammad M. Rahman, Auteur . - pp. [052201-1/8]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 132 N° 5 (Mai 2010) . - pp. [052201-1/8] Mots-clés : Partially  confined  liquid  jet  impingement  Transeint  conjugate  transfer  Rotating  disk Index. décimale : 536 Chaleur. Thermodynamique Résumé : This paper considers the transient conjugate heat transfer characterization of a partially confined liquid jet impinging on a rotating and uniformly heated solid disk of finite thickness and radius. A constant heat flux was imposed at the bottom surface of the solid disk at t=0, and heat transfer was monitored for the entire duration of the transient until the steady state condition was reached. Calculations were done for a number of disk materials using water as the coolant, covering a range of Reynolds numbers (225–900), Ekman numbers (7.08×10−5−[infinity]), nozzle-to-target spacing (beta=0.25–1.0), confinement ratios (rp/rd=0.2–0.75), disk thicknesses to nozzle diameter ratios (b/dn=0.25–1.67), and solid to fluid thermal conductivity ratios (36.91–697.56). It was found that a higher Reynolds number decreases the time to achieve the steady state condition and increases the local and average Nusselt number. The duration of the transient increases with the increment of the Ekman number and disk thickness, and the reduction in the thermal diffusivity of the disk material. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...]

Effects of variable viscosity and thermal conductivity of CuO-water nanofluid on heat transfer enhancement in natural convection / Eiyad Abu-Nada in Journal of heat transfer, Vol. 132 N° 5 (Mai 2010) 

Public ISBD [article]  in Journal of heat transfer > Vol. 132 N° 5 (Mai 2010) . - pp. [052401-1/9] Titre : Effects of variable viscosity and thermal conductivity of CuO-water nanofluid on heat transfer enhancement in natural convection : mathematical model and simulation Type de document : texte imprimé Auteurs : Eiyad Abu-Nada, Auteur Article en page(s) : pp. [052401-1/9] Note générale : Physique Langues : Anglais (eng) Mots-clés : Nanofluid  Viscosity  Thermal  conductivity  Natural  convection  Annulus Index. décimale : 536 Chaleur. Thermodynamique Résumé : Heat transfer enhancement in horizontal annuli using variable thermal conductivity and variable viscosity of CuO-water nanofluid is investigated numerically. The base case of simulation used thermal conductivity and viscosity data that consider temperature property dependence and nanoparticle size. It was observed that for Ra>=104, the average Nusselt number was deteriorated by increasing the volume fraction of nanoparticles. However, for Ra=103, the average Nusselt number enhancement depends on aspect ratio of the annulus as well as volume fraction of nanoparticles. Also, for Ra=103, the average Nusselt number was less sensitive to volume fraction of nanoparticles at high aspect ratio and the average Nusselt number increased by increasing the volume fraction of nanoaprticles for aspect ratios <=0.4. For Ra>=104, the Nusselt number was deteriorated everywhere around the cylinder surface especially at high aspect ratio. However, this reduction is only restricted to certain regions around the cylinder surface for Ra=103. For Ra>=104, the Maxwell–Garnett and the Chon et al. conductivity models demonstrated similar results. But, there was a deviation in the prediction at Ra=103 and this deviation becomes more significant at high volume fraction of nanoparticles. The Nguyen et al. data and the Brinkman model give completely different predictions for Ra>=104, where the difference in prediction of the Nusselt number reached 50%. However, this difference was less than 10% at Ra=103. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...] [article] Effects of variable viscosity and thermal conductivity of CuO-water nanofluid on heat transfer enhancement in natural convection : mathematical model and simulation [texte imprimé] / Eiyad Abu-Nada, Auteur . - pp. [052401-1/9]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 132 N° 5 (Mai 2010) . - pp. [052401-1/9] Mots-clés : Nanofluid  Viscosity  Thermal  conductivity  Natural  convection  Annulus Index. décimale : 536 Chaleur. Thermodynamique Résumé : Heat transfer enhancement in horizontal annuli using variable thermal conductivity and variable viscosity of CuO-water nanofluid is investigated numerically. The base case of simulation used thermal conductivity and viscosity data that consider temperature property dependence and nanoparticle size. It was observed that for Ra>=104, the average Nusselt number was deteriorated by increasing the volume fraction of nanoparticles. However, for Ra=103, the average Nusselt number enhancement depends on aspect ratio of the annulus as well as volume fraction of nanoparticles. Also, for Ra=103, the average Nusselt number was less sensitive to volume fraction of nanoparticles at high aspect ratio and the average Nusselt number increased by increasing the volume fraction of nanoaprticles for aspect ratios <=0.4. For Ra>=104, the Nusselt number was deteriorated everywhere around the cylinder surface especially at high aspect ratio. However, this reduction is only restricted to certain regions around the cylinder surface for Ra=103. For Ra>=104, the Maxwell–Garnett and the Chon et al. conductivity models demonstrated similar results. But, there was a deviation in the prediction at Ra=103 and this deviation becomes more significant at high volume fraction of nanoparticles. The Nguyen et al. data and the Brinkman model give completely different predictions for Ra>=104, where the difference in prediction of the Nusselt number reached 50%. However, this difference was less than 10% at Ra=103. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...]

Monte Carlo study of phonon heat conduction in silicon thin films including contributions of optical phonons / Arpit Mittal in Journal of heat transfer, Vol. 132 N° 5 (Mai 2010) 

Public ISBD [article]  in Journal of heat transfer > Vol. 132 N° 5 (Mai 2010) . - pp. [052402-1/11] Titre : Monte Carlo study of phonon heat conduction in silicon thin films including contributions of optical phonons Type de document : texte imprimé Auteurs : Arpit Mittal, Auteur ; Sandip Mazumder, Auteur Article en page(s) : pp. [052402-1/11] Note générale : Physique Langues : Anglais (eng) Mots-clés : Monte  Carlo  Boltzmann  transport  equation  Thin  film  Thermal  conductivity  Optical  phonon  Silicon Index. décimale : 536 Chaleur. Thermodynamique Résumé : The Monte Carlo method has found prolific use in the solution of the Boltzmann transport equation for phonons for the prediction of nonequilibrium heat conduction in crystalline thin films. This paper contributes to the state-of-the-art by performing a systematic study of the role of the various phonon modes on thermal conductivity predictions, in particular, optical phonons. A procedure to calculate three-phonon scattering time-scales with the inclusion of optical phonons is described and implemented. The roles of various phonon modes are assessed. It is found that transverse acoustic (TA) phonons are the primary carriers of energy at low temperatures. At high temperatures (T>200 K), longitudinal acoustic (LA) phonons carry more energy than TA phonons. When optical phonons are included, there is a significant change in the amount of energy carried by various phonons modes, especially at room temperature, where optical modes are found to carry about 25% of the energy at steady state in silicon thin films. Most importantly, it is found that inclusion of optical phonons results in better match with experimental observations for silicon thin-film thermal conductivity. The inclusion of optical phonons is found to decrease the thermal conductivity at intermediate temperatures (50–200 K) and to increase it at high temperature (>200 K), especially when the film is thin. The effect of number of stochastic samples, the dimensionality of the computational domain (two-dimensional versus three-dimensional), and the lateral (in-plane) dimension of the film on the statistical accuracy and computational efficiency is systematically studied and elucidated for all temperatures. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...] [article] Monte Carlo study of phonon heat conduction in silicon thin films including contributions of optical phonons [texte imprimé] / Arpit Mittal, Auteur ; Sandip Mazumder, Auteur . - pp. [052402-1/11]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 132 N° 5 (Mai 2010) . - pp. [052402-1/11] Mots-clés : Monte  Carlo  Boltzmann  transport  equation  Thin  film  Thermal  conductivity  Optical  phonon  Silicon Index. décimale : 536 Chaleur. Thermodynamique Résumé : The Monte Carlo method has found prolific use in the solution of the Boltzmann transport equation for phonons for the prediction of nonequilibrium heat conduction in crystalline thin films. This paper contributes to the state-of-the-art by performing a systematic study of the role of the various phonon modes on thermal conductivity predictions, in particular, optical phonons. A procedure to calculate three-phonon scattering time-scales with the inclusion of optical phonons is described and implemented. The roles of various phonon modes are assessed. It is found that transverse acoustic (TA) phonons are the primary carriers of energy at low temperatures. At high temperatures (T>200 K), longitudinal acoustic (LA) phonons carry more energy than TA phonons. When optical phonons are included, there is a significant change in the amount of energy carried by various phonons modes, especially at room temperature, where optical modes are found to carry about 25% of the energy at steady state in silicon thin films. Most importantly, it is found that inclusion of optical phonons results in better match with experimental observations for silicon thin-film thermal conductivity. The inclusion of optical phonons is found to decrease the thermal conductivity at intermediate temperatures (50–200 K) and to increase it at high temperature (>200 K), especially when the film is thin. The effect of number of stochastic samples, the dimensionality of the computational domain (two-dimensional versus three-dimensional), and the lateral (in-plane) dimension of the film on the statistical accuracy and computational efficiency is systematically studied and elucidated for all temperatures. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...]

Design and test of carbon nanotube biwick structure for high-heat-flux phase change heat transfer / Qingjun Cai in Journal of heat transfer, Vol. 132 N° 5 (Mai 2010) 

Public ISBD [article]  in Journal of heat transfer > Vol. 132 N° 5 (Mai 2010) . - pp. [052403-1/8] Titre : Design and test of carbon nanotube biwick structure for high-heat-flux phase change heat transfer Type de document : texte imprimé Auteurs : Qingjun Cai, Auteur ; Chung-Lung Chen, Auteur Article en page(s) : pp. [052403-1/8] Note générale : Physique Langues : Anglais (eng) Mots-clés : Thermometer  Carbon  nanotube  Wick  structure  Temperature  measurement  Capillarity  Cooling Index. décimale : 536 Chaleur. Thermodynamique Résumé : With the increase in power consumption in compact electronic devices, passive heat transfer cooling technologies with high-heat-flux characteristics are highly desired in microelectronic industries. Carbon nanotube (CNT) clusters have high thermal conductivity, nanopore size, and large porosity and can be used as wick structure in a heat pipe heatspreader to provide high capillary force for high-heat-flux thermal management. This paper reports investigations of high-heat-flux cooling of the CNT biwick structure, associated with the development of a reliable thermometer and high performance heater. The thermometer/heater is a 100-nm-thick and 600 µm wide Z-shaped platinum wire resistor, fabricated on a thermally oxidized silicon substrate of a CNT sample to heat a 2×2 mm2 wick area. As a heater, it provides a direct heating effect without a thermal interface and is capable of high-temperature operation over 800°C. As a thermometer, reliable temperature measurement is achieved by calibrating the resistance variation versus temperature after the annealing process is applied. The thermally oxidized layer on the silicon substrate is around 1-µm-thick and pinhole-free, which ensures the platinum thermometer/heater from the severe CNT growth environments without any electrical leakage. For high-heat-flux cooling, the CNT biwick structure is composed of 250 µm tall and 100 µm wide stripelike CNT clusters with 50 µm stripe-spacers. Using 1×1 cm2 CNT biwick samples, experiments are completed in both open and saturated environments. Experimental results demonstrate 600 W/cm2 heat transfer capacity and good thermal and mass transport characteristics in the nanolevel porous media. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...] [article] Design and test of carbon nanotube biwick structure for high-heat-flux phase change heat transfer [texte imprimé] / Qingjun Cai, Auteur ; Chung-Lung Chen, Auteur . - pp. [052403-1/8]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 132 N° 5 (Mai 2010) . - pp. [052403-1/8] Mots-clés : Thermometer  Carbon  nanotube  Wick  structure  Temperature  measurement  Capillarity  Cooling Index. décimale : 536 Chaleur. Thermodynamique Résumé : With the increase in power consumption in compact electronic devices, passive heat transfer cooling technologies with high-heat-flux characteristics are highly desired in microelectronic industries. Carbon nanotube (CNT) clusters have high thermal conductivity, nanopore size, and large porosity and can be used as wick structure in a heat pipe heatspreader to provide high capillary force for high-heat-flux thermal management. This paper reports investigations of high-heat-flux cooling of the CNT biwick structure, associated with the development of a reliable thermometer and high performance heater. The thermometer/heater is a 100-nm-thick and 600 µm wide Z-shaped platinum wire resistor, fabricated on a thermally oxidized silicon substrate of a CNT sample to heat a 2×2 mm2 wick area. As a heater, it provides a direct heating effect without a thermal interface and is capable of high-temperature operation over 800°C. As a thermometer, reliable temperature measurement is achieved by calibrating the resistance variation versus temperature after the annealing process is applied. The thermally oxidized layer on the silicon substrate is around 1-µm-thick and pinhole-free, which ensures the platinum thermometer/heater from the severe CNT growth environments without any electrical leakage. For high-heat-flux cooling, the CNT biwick structure is composed of 250 µm tall and 100 µm wide stripelike CNT clusters with 50 µm stripe-spacers. Using 1×1 cm2 CNT biwick samples, experiments are completed in both open and saturated environments. Experimental results demonstrate 600 W/cm2 heat transfer capacity and good thermal and mass transport characteristics in the nanolevel porous media. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...]

Constructal allocation of nanoparticles in nanofluids / Chao Bai in Journal of heat transfer, Vol. 132 N° 5 (Mai 2010) 

Public ISBD [article]  in Journal of heat transfer > Vol. 132 N° 5 (Mai 2010) . - pp. [052404-1/6] Titre : Constructal allocation of nanoparticles in nanofluids Type de document : texte imprimé Auteurs : Chao Bai, Auteur ; Liqiu Wang, Auteur Article en page(s) : pp. [052404-1/6] Note générale : Physique Langues : Anglais (eng) Mots-clés : Blade  configuration  Design  Constructal  theory  Transition  line  Dispersed  configuration  Heat  sinks  Nanofluids  Nanoparticles Index. décimale : 536 Chaleur. Thermodynamique Résumé : We perform a constructal design of heat conduction in a blade-configured disk-shaped domain with uniform heat generation and periphery heat-sink by introducing a transition line from two-path conduction to one-path conduction in the domain. This orderly arranged blade configuration can offer significantly smaller constructal overall temperature difference than that of the dispersed configuration and thus performs much better. The constructal allocation of nanoparticles inside the base fluids and thus the heat-conduction design inside the nanofluids are very important for better system performance. This work shows that the search for heat-flow configuration is a key to performance, and the constructal theory is the strategy for discovering the configuration and the significantly better performance. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...] [article] Constructal allocation of nanoparticles in nanofluids [texte imprimé] / Chao Bai, Auteur ; Liqiu Wang, Auteur . - pp. [052404-1/6]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 132 N° 5 (Mai 2010) . - pp. [052404-1/6] Mots-clés : Blade  configuration  Design  Constructal  theory  Transition  line  Dispersed  configuration  Heat  sinks  Nanofluids  Nanoparticles Index. décimale : 536 Chaleur. Thermodynamique Résumé : We perform a constructal design of heat conduction in a blade-configured disk-shaped domain with uniform heat generation and periphery heat-sink by introducing a transition line from two-path conduction to one-path conduction in the domain. This orderly arranged blade configuration can offer significantly smaller constructal overall temperature difference than that of the dispersed configuration and thus performs much better. The constructal allocation of nanoparticles inside the base fluids and thus the heat-conduction design inside the nanofluids are very important for better system performance. This work shows that the search for heat-flow configuration is a key to performance, and the constructal theory is the strategy for discovering the configuration and the significantly better performance. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...]

The effect of local thermal nonequilibrium on the onset of convection in a nanofluid / D. A. Nield in Journal of heat transfer, Vol. 132 N° 5 (Mai 2010) 

Public ISBD [article]  in Journal of heat transfer > Vol. 132 N° 5 (Mai 2010) . - pp. [052405-1/7] Titre : The effect of local thermal nonequilibrium on the onset of convection in a nanofluid Type de document : texte imprimé Auteurs : D. A. Nield, Auteur ; Andrey V. Kuznetsov, Auteur Article en page(s) : pp. [052405-1/7] Note générale : Physique Langues : Anglais (eng) Mots-clés : Nanofluid  Brownian  motion  Thermophoresis  Rayleigh-Bénard  problem  Local  thermal  nonequilibrium Index. décimale : 536 Chaleur. Thermodynamique Résumé : The onset of convection in a horizontal layer of a nanofluid is studied analytically. The model used for the nanofluid incorporates the effects of Brownian motion and thermophoresis, and allows for local thermal nonequilibrium (LTNE) between the particle and fluid phases. The analysis reveals that in some circumstances, the effect of LTNE can be significant, but for a typical dilute nanofluid (with large Lewis number and with small particle-to-fluid heat capacity ratio), the effect is small. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...] [article] The effect of local thermal nonequilibrium on the onset of convection in a nanofluid [texte imprimé] / D. A. Nield, Auteur ; Andrey V. Kuznetsov, Auteur . - pp. [052405-1/7]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 132 N° 5 (Mai 2010) . - pp. [052405-1/7] Mots-clés : Nanofluid  Brownian  motion  Thermophoresis  Rayleigh-Bénard  problem  Local  thermal  nonequilibrium Index. décimale : 536 Chaleur. Thermodynamique Résumé : The onset of convection in a horizontal layer of a nanofluid is studied analytically. The model used for the nanofluid incorporates the effects of Brownian motion and thermophoresis, and allows for local thermal nonequilibrium (LTNE) between the particle and fluid phases. The analysis reveals that in some circumstances, the effect of LTNE can be significant, but for a typical dilute nanofluid (with large Lewis number and with small particle-to-fluid heat capacity ratio), the effect is small. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...]

Spectral collocation method for transient combined radiation and conduction in an anisotropic scattering slab with graded index / Ya-Song Sun in Journal of heat transfer, Vol. 132 N° 5 (Mai 2010) 

Public ISBD [article]  in Journal of heat transfer > Vol. 132 N° 5 (Mai 2010) . - pp. [052701-1/9] Titre : Spectral collocation method for transient combined radiation and conduction in an anisotropic scattering slab with graded index Type de document : texte imprimé Auteurs : Ya-Song Sun, Auteur ; Ben-Wen Li, Auteur Article en page(s) : pp. [052701-1/9] Note générale : Physique Langues : Anglais (eng) Mots-clés : Spectral  collocation  method  Rediative  heat  transfer  Graded  index  Anisotropic  scattering  Transient  combined  radiation  and  conduction Index. décimale : 536 Chaleur. Thermodynamique Résumé : The spectral collocation method for transient combined radiation and conduction heat transfer in a planar participating medium with spatially variable refractive index is introduced and formulated. The angular dependence of the problem is discretized by discrete ordinates method and the space dependence is expressed by Chebyshev polynomial and discretized by spectral collocation method. Due to the exponential convergence of spectral methods, very high accuracy can be obtained even using a small resolution for present problem. Numerical results in one-dimensional planar slab by Chebyshev collocation spectral-discrete ordinates method (SP-DOM) are compared with those available data in references. Effects of various parameters such as the variable thermal conductivity, the scattering albedo, the emissivity of boundary, the conduction-radiation parameter, the optical thickness, and the graded index are studied for absorbing, emitting, and anisotropic scattering medium. The SP-DOM has been found to successfully and efficiently deal with transient combined radiation and conduction heat transfer problem in graded index medium. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...] [article] Spectral collocation method for transient combined radiation and conduction in an anisotropic scattering slab with graded index [texte imprimé] / Ya-Song Sun, Auteur ; Ben-Wen Li, Auteur . - pp. [052701-1/9]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 132 N° 5 (Mai 2010) . - pp. [052701-1/9] Mots-clés : Spectral  collocation  method  Rediative  heat  transfer  Graded  index  Anisotropic  scattering  Transient  combined  radiation  and  conduction Index. décimale : 536 Chaleur. Thermodynamique Résumé : The spectral collocation method for transient combined radiation and conduction heat transfer in a planar participating medium with spatially variable refractive index is introduced and formulated. The angular dependence of the problem is discretized by discrete ordinates method and the space dependence is expressed by Chebyshev polynomial and discretized by spectral collocation method. Due to the exponential convergence of spectral methods, very high accuracy can be obtained even using a small resolution for present problem. Numerical results in one-dimensional planar slab by Chebyshev collocation spectral-discrete ordinates method (SP-DOM) are compared with those available data in references. Effects of various parameters such as the variable thermal conductivity, the scattering albedo, the emissivity of boundary, the conduction-radiation parameter, the optical thickness, and the graded index are studied for absorbing, emitting, and anisotropic scattering medium. The SP-DOM has been found to successfully and efficiently deal with transient combined radiation and conduction heat transfer problem in graded index medium. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...]

Thermal wave applications in flow fields with steady velocity profile / Zhefu Wang in Journal of heat transfer, Vol. 132 N° 5 (Mai 2010) 

Public ISBD [article]  in Journal of heat transfer > Vol. 132 N° 5 (Mai 2010) . - pp. [054501-1/4] Titre : Thermal wave applications in flow fields with steady velocity profile Type de document : texte imprimé Auteurs : Zhefu Wang, Auteur ; Richard B. Peterson, Auteur Article en page(s) : pp. [054501-1/4] Note générale : Physique Langues : Anglais (eng) Mots-clés : Convection  Periodic  boundary  conditions  Complex  combination  Phase  shift Index. décimale : 536 Chaleur. Thermodynamique Résumé : This study explores the use of a thermal wave approach for flow field measurement applications, such as flow diagnostics near surfaces and in microfluidic systems. The basic mathematical characteristics of the governing equations of heat convection, with periodic heating boundary conditions in steady flow, are discussed and the validity of applying the complex combination method to this problem is illustrated. A scaling analysis of a two-dimensional thermal wave configuration with a linear velocity profile is performed to provide important insights into this type of heat transfer phenomena. A two-dimensional conjugate heat transfer model is developed and solved numerically with a finite difference method to demonstrate an example of imposing a thermal wave onto a flow field. The simulation results show that the temperature signal, especially the phase information, can be used for the measurement of flow properties near the surface, such as the wall shear stress. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...] [article] Thermal wave applications in flow fields with steady velocity profile [texte imprimé] / Zhefu Wang, Auteur ; Richard B. Peterson, Auteur . - pp. [054501-1/4]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 132 N° 5 (Mai 2010) . - pp. [054501-1/4] Mots-clés : Convection  Periodic  boundary  conditions  Complex  combination  Phase  shift Index. décimale : 536 Chaleur. Thermodynamique Résumé : This study explores the use of a thermal wave approach for flow field measurement applications, such as flow diagnostics near surfaces and in microfluidic systems. The basic mathematical characteristics of the governing equations of heat convection, with periodic heating boundary conditions in steady flow, are discussed and the validity of applying the complex combination method to this problem is illustrated. A scaling analysis of a two-dimensional thermal wave configuration with a linear velocity profile is performed to provide important insights into this type of heat transfer phenomena. A two-dimensional conjugate heat transfer model is developed and solved numerically with a finite difference method to demonstrate an example of imposing a thermal wave onto a flow field. The simulation results show that the temperature signal, especially the phase information, can be used for the measurement of flow properties near the surface, such as the wall shear stress. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...]

Vapor flow analysis in flat plate heat pipes using homotopy perturbation method / Hamid Reza Seyf in Journal of heat transfer, Vol. 132 N° 5 (Mai 2010) 

Public ISBD [article]  in Journal of heat transfer > Vol. 132 N° 5 (Mai 2010) . - pp. [054502-1/4] Titre : Vapor flow analysis in flat plate heat pipes using homotopy perturbation method Type de document : texte imprimé Auteurs : Hamid Reza Seyf, Auteur ; Mohammad Layeghi, Auteur Article en page(s) : pp. [054502-1/4] Note générale : Physique Langues : Anglais (eng) Mots-clés : Flat  plate  heat  pipe  Vapor  flow  Laminar  and  incompressible  Homotopy  perturbation  method  Numerical  method Index. décimale : 536 Chaleur. Thermodynamique Résumé : In the present study, an analytical solution for 2D vapor flow in flat plate heat pipes is presented. The governing equations are solved analytically using the homotopy perturbation method, and numerically using the finite volume method, based on collocated grids. The analytical results are obtained for nondimensional velocity profiles and axial pressures distribution along the entire length of the heat pipe, and compared with the numerical ones. It is shown that there is a relatively small difference of about 1% in the worst case between the analytical and numerical results. Furthermore, the effects of the Reynolds number and the ratio of condenser to evaporator lengths on the flow variables are discussed. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...] [article] Vapor flow analysis in flat plate heat pipes using homotopy perturbation method [texte imprimé] / Hamid Reza Seyf, Auteur ; Mohammad Layeghi, Auteur . - pp. [054502-1/4]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 132 N° 5 (Mai 2010) . - pp. [054502-1/4] Mots-clés : Flat  plate  heat  pipe  Vapor  flow  Laminar  and  incompressible  Homotopy  perturbation  method  Numerical  method Index. décimale : 536 Chaleur. Thermodynamique Résumé : In the present study, an analytical solution for 2D vapor flow in flat plate heat pipes is presented. The governing equations are solved analytically using the homotopy perturbation method, and numerically using the finite volume method, based on collocated grids. The analytical results are obtained for nondimensional velocity profiles and axial pressures distribution along the entire length of the heat pipe, and compared with the numerical ones. It is shown that there is a relatively small difference of about 1% in the worst case between the analytical and numerical results. Furthermore, the effects of the Reynolds number and the ratio of condenser to evaporator lengths on the flow variables are discussed. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...]

Transient conduction in a hollow cylinder with variable thermal conductivity / M. Kandula in Journal of heat transfer, Vol. 132 N° 5 (Mai 2010) 

Public ISBD [article]  in Journal of heat transfer > Vol. 132 N° 5 (Mai 2010) . - pp. [054503-1/3] Titre : Transient conduction in a hollow cylinder with variable thermal conductivity Type de document : texte imprimé Auteurs : M. Kandula, Auteur Article en page(s) : pp. [054503-1/3] Note générale : Physique Langues : Anglais (eng) Mots-clés : Transient  heat  conduction  Hollow  cylinder  Variable  thermal  conductivity  Optimal  linearization Index. décimale : 536 Chaleur. Thermodynamique Résumé : A closed form approximate solution has been obtained for the transient temperature distribution in a hollow cylinder with a linear variation in thermal conductivity with temperature. The boundary conditions considered are convective heating (Newton's law) at the exposed inner surface and adiabatic outer surface. The solution is obtained using the method of optimal linearization, with the initial solution given by the integral method. The nonlinear analytical solution is shown to compare well with the finite difference solution. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...] [article] Transient conduction in a hollow cylinder with variable thermal conductivity [texte imprimé] / M. Kandula, Auteur . - pp. [054503-1/3]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 132 N° 5 (Mai 2010) . - pp. [054503-1/3] Mots-clés : Transient  heat  conduction  Hollow  cylinder  Variable  thermal  conductivity  Optimal  linearization Index. décimale : 536 Chaleur. Thermodynamique Résumé : A closed form approximate solution has been obtained for the transient temperature distribution in a hollow cylinder with a linear variation in thermal conductivity with temperature. The boundary conditions considered are convective heating (Newton's law) at the exposed inner surface and adiabatic outer surface. The solution is obtained using the method of optimal linearization, with the initial solution given by the integral method. The nonlinear analytical solution is shown to compare well with the finite difference solution. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...]

Oscillatory streaming flow based mini/microheat pipe technology / Z. Zhang in Journal of heat transfer, Vol. 132 N° 5 (Mai 2010) 

Public ISBD [article]  in Journal of heat transfer > Vol. 132 N° 5 (Mai 2010) . - pp. [055001-1/8] Titre : Oscillatory streaming flow based mini/microheat pipe technology Type de document : texte imprimé Auteurs : Z. Zhang, Auteur ; C. Liu, Auteur ; A. Fadl, Auteur Article en page(s) : pp. [055001-1/8] Note générale : Physique Langues : Anglais (eng) Mots-clés : Heat  pipe  Flow  streaming  Oscillation  flow  Bifurcation  Microchannel Index. décimale : 536 Chaleur. Thermodynamique Résumé : The sustained drive for faster and smaller micro-electronic devices has led to a considerable increase in power density. The ability to effectively pump and enhance heat transfer in mini-/microchannels is of immense technological importance. Using oscillatory flow to enhance the convective heat transfer coefficients in micro-/minichannels is one of many new concepts and methodologies that have been proposed. In this paper, a novel and simple concept is presented on oscillating streaming flow based mini/microheat pipe or heat spreader technology. Phenomena of the flow streaming can be found in zero-mean velocity oscillating flows in many channel geometries. Although there is no net mass flow (zero-mean velocity) passing through the channel, discrepancy in the velocity profiles between the forward and backward flows causes fluid particles near the walls to drift toward one end while particles near the centerline drift to the other end. This unique characteristic of flow streaming could be used for various applications. Some of the advantages include enhanced heat/mass transfer, pumpless fluid propulsion, multichannel fluid distribution, easy system integration, and cost-effective operation. Preliminary work has been conducted on scaling analysis, computer simulations, and visualization experiments of fluid streaming, propulsion, and multichannel distribution by flow oscillation in minitapered channels and channel networks. Results show that streaming flow has the potential to be used as a cost-effective and reliable heat pipe and/or as a heat spreader technique when fluid thermal conductivity is low. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...] [article] Oscillatory streaming flow based mini/microheat pipe technology [texte imprimé] / Z. Zhang, Auteur ; C. Liu, Auteur ; A. Fadl, Auteur . - pp. [055001-1/8]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 132 N° 5 (Mai 2010) . - pp. [055001-1/8] Mots-clés : Heat  pipe  Flow  streaming  Oscillation  flow  Bifurcation  Microchannel Index. décimale : 536 Chaleur. Thermodynamique Résumé : The sustained drive for faster and smaller micro-electronic devices has led to a considerable increase in power density. The ability to effectively pump and enhance heat transfer in mini-/microchannels is of immense technological importance. Using oscillatory flow to enhance the convective heat transfer coefficients in micro-/minichannels is one of many new concepts and methodologies that have been proposed. In this paper, a novel and simple concept is presented on oscillating streaming flow based mini/microheat pipe or heat spreader technology. Phenomena of the flow streaming can be found in zero-mean velocity oscillating flows in many channel geometries. Although there is no net mass flow (zero-mean velocity) passing through the channel, discrepancy in the velocity profiles between the forward and backward flows causes fluid particles near the walls to drift toward one end while particles near the centerline drift to the other end. This unique characteristic of flow streaming could be used for various applications. Some of the advantages include enhanced heat/mass transfer, pumpless fluid propulsion, multichannel fluid distribution, easy system integration, and cost-effective operation. Preliminary work has been conducted on scaling analysis, computer simulations, and visualization experiments of fluid streaming, propulsion, and multichannel distribution by flow oscillation in minitapered channels and channel networks. Results show that streaming flow has the potential to be used as a cost-effective and reliable heat pipe and/or as a heat spreader technique when fluid thermal conductivity is low. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...]

Exemplaires

Bibliothèque Ecole Nationale Polytechnique d'Alger

Accueil

Se connecter

Météo

Adresse