Documents disponibles écrits par cet auteur

Convective heat transfer in microchannels of noncircular cross sections / S. Shahsavari in Journal of heat transfer, Vol 134 N° 9 (Septembre 2012) 

Public ISBD [article]  in Journal of heat transfer > Vol 134 N° 9 (Septembre 2012) . - 10 p. Titre : Convective heat transfer in microchannels of noncircular cross sections : an analytical approach Type de document : texte imprimé Auteurs : S. Shahsavari, Auteur ; A. Tamayol, Auteur ; E. Kjeang, Auteur Année de publication : 2012 Article en page(s) : 10 p. Note générale : heat transfer Langues : Anglais (eng) Mots-clés : mini/microchannels;  fully  developed  flow;  noncircular  channels;  forced  convection Index. décimale : 536 Chaleur. Thermodynamique Résumé : Analytical solutions are presented for velocity and temperature distributions of laminar fully developed flow of Newtonian, constant property fluids in micro/minichannels of hyperelliptical and regular polygonal cross sections. The considered geometries cover several common shapes such as ellipse, rectangle, rectangle with round corners, rhombus, star-shape, and all regular polygons. The analysis is carried out under the conditions of constant axial wall heat flux with uniform peripheral heat flux at a given cross section. A linear least squares point matching technique is used to minimize the residual between the actual and the predicted values on the boundary of the channel. Hydrodynamic and thermal characteristics of the flow are derived; these include pressure drop and local and average Nusselt numbers. The proposed results are successfully verified with existing analytical and numerical solutions from the literature for a variety of cross sections. The present study provides analytical-based compact solutions for velocity and temperature fields that are essential for basic designs, parametric studies, and optimization analyses required for many thermofluidic applications. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000134000009 [...] [article] Convective heat transfer in microchannels of noncircular cross sections : an analytical approach [texte imprimé] / S. Shahsavari, Auteur ; A. Tamayol, Auteur ; E. Kjeang, Auteur . - 2012 . - 10 p. heat transfer Langues : Anglais (eng) in Journal of heat transfer > Vol 134 N° 9 (Septembre 2012) . - 10 p. Mots-clés : mini/microchannels;  fully  developed  flow;  noncircular  channels;  forced  convection Index. décimale : 536 Chaleur. Thermodynamique Résumé : Analytical solutions are presented for velocity and temperature distributions of laminar fully developed flow of Newtonian, constant property fluids in micro/minichannels of hyperelliptical and regular polygonal cross sections. The considered geometries cover several common shapes such as ellipse, rectangle, rectangle with round corners, rhombus, star-shape, and all regular polygons. The analysis is carried out under the conditions of constant axial wall heat flux with uniform peripheral heat flux at a given cross section. A linear least squares point matching technique is used to minimize the residual between the actual and the predicted values on the boundary of the channel. Hydrodynamic and thermal characteristics of the flow are derived; these include pressure drop and local and average Nusselt numbers. The proposed results are successfully verified with existing analytical and numerical solutions from the literature for a variety of cross sections. The present study provides analytical-based compact solutions for velocity and temperature fields that are essential for basic designs, parametric studies, and optimization analyses required for many thermofluidic applications. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000134000009 [...]

Impact of particulate deposition on the thermohydraulic performance of metal foam heat exchangers / K. Hooman in Journal of heat transfer, Vol 134 N° 9 (Septembre 2012) 

Public ISBD [article]  in Journal of heat transfer > Vol 134 N° 9 (Septembre 2012) . - 07 p. Titre : Impact of particulate deposition on the thermohydraulic performance of metal foam heat exchangers : a simplified theoretical model Type de document : texte imprimé Auteurs : K. Hooman, Auteur ; A. Tamayol, Auteur ; M. R. Malayeri, Auteur Année de publication : 2012 Article en page(s) : 07 p. Note générale : heat transfer Langues : Anglais (eng) Mots-clés : metal  foams;  forced  convection;  parametric  study;  thermal  resistors;  dust Index. décimale : 536 Chaleur. Thermodynamique Résumé : Assuming uniform particulate deposit layer, with deposition layer thickness in the range of 10–400 µm, on the ligaments of a metal foam heat sink, the effects of airborne particle deposition on the steady-state thermohydraulic performance of a metal foam heat sink are examined theoretically. Using a cubic cell model, changes in the foam internal structure, due to deposition, have been theoretically related to the increased pressure drop due to partial blockage of the pores. Our results suggest that the fouled to clean pressure drop ratio is only a function of the ligament to pore diameter ratio. Another interesting observation is that, compared to clean foams, the pressure drop can increase by orders of magnitude depending on the extent to which the pores are blocked. To examine the fouling effects on heat transfer from the foams, a thermal resistance network has been used. Moreover, the heat transfer from metal foams is more affected by fouling at higher fluid velocities. For example, when air is pushed through foams which their ligaments are uniformly covered by particles at 3 m/s, up to 15% decrease in the total heat transfer from the heated surface is predicted. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000134000009 [...] [article] Impact of particulate deposition on the thermohydraulic performance of metal foam heat exchangers : a simplified theoretical model [texte imprimé] / K. Hooman, Auteur ; A. Tamayol, Auteur ; M. R. Malayeri, Auteur . - 2012 . - 07 p. heat transfer Langues : Anglais (eng) in Journal of heat transfer > Vol 134 N° 9 (Septembre 2012) . - 07 p. Mots-clés : metal  foams;  forced  convection;  parametric  study;  thermal  resistors;  dust Index. décimale : 536 Chaleur. Thermodynamique Résumé : Assuming uniform particulate deposit layer, with deposition layer thickness in the range of 10–400 µm, on the ligaments of a metal foam heat sink, the effects of airborne particle deposition on the steady-state thermohydraulic performance of a metal foam heat sink are examined theoretically. Using a cubic cell model, changes in the foam internal structure, due to deposition, have been theoretically related to the increased pressure drop due to partial blockage of the pores. Our results suggest that the fouled to clean pressure drop ratio is only a function of the ligament to pore diameter ratio. Another interesting observation is that, compared to clean foams, the pressure drop can increase by orders of magnitude depending on the extent to which the pores are blocked. To examine the fouling effects on heat transfer from the foams, a thermal resistance network has been used. Moreover, the heat transfer from metal foams is more affected by fouling at higher fluid velocities. For example, when air is pushed through foams which their ligaments are uniformly covered by particles at 3 m/s, up to 15% decrease in the total heat transfer from the heated surface is predicted. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000134000009 [...]

Parallel flow through ordered fibers / A. Tamayol in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 11 (Novembre 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 11 (Novembre 2010) . - 07 p. Titre : Parallel flow through ordered fibers : an analytical approach Type de document : texte imprimé Auteurs : A. Tamayol, Auteur ; M. Bahrami, Auteur Année de publication : 2011 Article en page(s) : 07 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : flow  (dynamics);  permeability;  fibers;  computer  simulation;  cylinders;  poisson  equation;  porosity Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : In this study, fully developed flow parallel to ordered fibers is investigated analytically. The considered fibrous media are made up of in-line (square), staggered, and hexagonal arrays of cylinders. Starting from the general solution of Poisson’s equation, compact analytical solutions are proposed for both velocity distribution and permeability of the considered structures. In addition, independent numerical simulations are performed for the considered arrangements over the entire range of porosity and the results are compared with the proposed solutions. The developed solutions are successfully verified through comparison with experimental data, collected by others, and the present numerical results over a wide range of porosity. The results show that for the ordered arrangements with high porosity, the parallel permeability is independent of the microstructure geometrical arrangements; on the other hand, for lower porosities the hexagonal arrangement provides lower pressure drop, as expected. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27439 [...] [article] Parallel flow through ordered fibers : an analytical approach [texte imprimé] / A. Tamayol, Auteur ; M. Bahrami, Auteur . - 2011 . - 07 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 11 (Novembre 2010) . - 07 p. Mots-clés : flow  (dynamics);  permeability;  fibers;  computer  simulation;  cylinders;  poisson  equation;  porosity Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : In this study, fully developed flow parallel to ordered fibers is investigated analytically. The considered fibrous media are made up of in-line (square), staggered, and hexagonal arrays of cylinders. Starting from the general solution of Poisson’s equation, compact analytical solutions are proposed for both velocity distribution and permeability of the considered structures. In addition, independent numerical simulations are performed for the considered arrangements over the entire range of porosity and the results are compared with the proposed solutions. The developed solutions are successfully verified through comparison with experimental data, collected by others, and the present numerical results over a wide range of porosity. The results show that for the ordered arrangements with high porosity, the parallel permeability is independent of the microstructure geometrical arrangements; on the other hand, for lower porosities the hexagonal arrangement provides lower pressure drop, as expected. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27439 [...]

Slip-flow pressure drop in microchannels of general cross section / M. Bahrami in Transactions of the ASME . Journal of fluids engineering, Vol. 131 N° 3 (Mars 2009) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 3 (Mars 2009) . - 08 p. Titre : Slip-flow pressure drop in microchannels of general cross section Type de document : texte imprimé Auteurs : M. Bahrami, Auteur ; A. Tamayol, Auteur ; P. Taheri, Auteur Année de publication : 2009 Article en page(s) : 08 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : compact  analytical  model;  pressure  drop Résumé : In the present study, a compact analytical model is developed to determine the pressure drop of fully-developed, incompressible, and constant properties slip-flow through arbitrary cross section microchannels. An averaged first-order Maxwell slip boundary condition is considered. Introducing a relative velocity, the difference between the bulk flow and the boundary velocities, the axial momentum reduces to Poisson’s equation with homogeneous boundary condition. Square root of area is selected as the characteristic length scale. The model of (2006, “ Pressure Drop of Laminar, Fully Developed Flow in Microchannels of Arbitrary Cross Section,” ASME J. Fluids Eng., 128, pp. 1036–1044), which was developed for no-slip boundary condition, is extended to cover the slip-flow regime in this study. The proposed model for pressure drop is a function of geometrical parameters of the channel: cross sectional area, perimeter, polar moment of inertia, and the Knudsen number. The model is successfully validated against existing numerical and experimental data collected from different sources in literature for several shapes, including circular, rectangular, trapezoidal, and double-trapezoidal cross sections and a variety of gases such as nitrogen, argon, and helium. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Slip-flow pressure drop in microchannels of general cross section [texte imprimé] / M. Bahrami, Auteur ; A. Tamayol, Auteur ; P. Taheri, Auteur . - 2009 . - 08 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 3 (Mars 2009) . - 08 p. Mots-clés : compact  analytical  model;  pressure  drop Résumé : In the present study, a compact analytical model is developed to determine the pressure drop of fully-developed, incompressible, and constant properties slip-flow through arbitrary cross section microchannels. An averaged first-order Maxwell slip boundary condition is considered. Introducing a relative velocity, the difference between the bulk flow and the boundary velocities, the axial momentum reduces to Poisson’s equation with homogeneous boundary condition. Square root of area is selected as the characteristic length scale. The model of (2006, “ Pressure Drop of Laminar, Fully Developed Flow in Microchannels of Arbitrary Cross Section,” ASME J. Fluids Eng., 128, pp. 1036–1044), which was developed for no-slip boundary condition, is extended to cover the slip-flow regime in this study. The proposed model for pressure drop is a function of geometrical parameters of the channel: cross sectional area, perimeter, polar moment of inertia, and the Knudsen number. The model is successfully validated against existing numerical and experimental data collected from different sources in literature for several shapes, including circular, rectangular, trapezoidal, and double-trapezoidal cross sections and a variety of gases such as nitrogen, argon, and helium. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

Thermal assessment of forced convection through metal foam heat exchangers / A. Tamayol in Journal of heat transfer, Vol. 133 N° 11 (Novembre 2011) 

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