Begell House Inc.
Computational Thermal Sciences: An International Journal
CTS
1940-2503
3
3
2011
Numerical study of heat transfer and phase change in a single metal particle of powder material in application to selective laser sintering
169-177
Ram
Dayal
Center of Smart Interfaces, Technische Universität Darmstadt, Petersenstr. 3264287 Germany ; Institute of Technical Thermodynamics, Technische Universitat Darmstadt, Petersenstr. 17, 64287 Germany; School of Automobile, Mechanical and Mechatronics Engineering, Manipal University Jaipur, India
Tatiana
Gambaryan-Roisman
Technische Universität Darmstadt
Eberhard
Abele
Center of Smart Interfaces, Technische Universität Darmstadt; Institute of Production Management, Technology and Machine Tools, Technische Universität Darmstadt, 64287 Germany
The heat transfer and phase change induced by interaction between a spherical metal particle and pulsed laser source during liquid phase sintering of metal powders is investigated numerically. The heat transfer model used for this study accounts for melting and resolidification occurring during heating and cooling phases of pulsed laser sintering. The particle surroundings are modeled as a continuum representing the loose powder. Evolution of temperature field and the phase change in the metal particle as well as its surroundings are discussed. The influence of laser pulse frequency, pulse duration and powder particle size on the melting process are described.
NUMERICAL MODELING OF DROPLET-SUBSTRATE INTERACTION USING A LATTICE BOLTZMANN MOMENT MODEL
179-186
Yali
Guo
Key Laboratory of Desalination, Liaoning Province;
School of Energy and Power Engineering, Dalian University of Technology, Dalian 116024, China
Rachid
Bennacer
L2MGC F-95000, University of Cergy-Pontoise, 95031 Cergy-Pontoise Cedex, Paris, France; ENS-Cachan Dpt GC/LMT/CNRS UMR 8535, 61 Ave. du Président Wilson, 94235 Cachan Cedex, France; Tianjin Key Lab of Refrigeration Technology, Tianjin University of Commerce, 300134
Sheng Qiang
Shen
Dalian University of Technology
Weizhong
Li
Key Laboratory of Ocean Energy Utilization and Energy Conservation of Ministry of Education,
School of Energy and Power Engineering, Dalian University of Technology, Dalian 116024, China
The shape and surface texture of a liquid droplet were studied in two dimensions when a droplet impinges on a solid substrate under isothermal conditions. The lattice Boltzmann moment model was applied to simulate the fluid dynamics considering the adhesive interaction between fluid particles and surfaces. The results show the influence of wetting on the process and the drop shape For a hydrophobic surface, the process after impinging may be divided into two stages: the spreading process driven by inertial forces and the subsequent oscillations (recoiling process) driven by surface tension forces; while for the hydrophilic surface, the droplet will only deposit on the surface and there is no recoiling stage. In addition, the effects of the impingement speed on the droplet shape and texture were studied. The spreading speed and the maximum droplet diameter increase with the rise of the impingement speed. The evaporation and thermal effects were underlined and illustrated.
Comprehensive investigation of an inverse geometry problem in heat conduction via adjoint-based optimization method
187-201
Hamid
Fazeli
K. N. Toosi University of Technology, Tehran, ‎Iran
P.
Forooghi
Department of Mechanical Engineering, University of Queensland, Brisbane
An inverse geometry problem in heat conduction is solved using different versions of an iterative regularization method. The algorithm consists of direct and inverse problems, which aims to modification of geometry. The direct problem is solved using a finite element method(FEM). The employed iterative regularization method is constructed using the adjoint and sensitivity equations that are used to calculate the gradient of the objective function and the optimal step size, respectively. Results shown that the Powel-Beale version has the best convergence rate compared to the Fletcher-Reeves and Polak-Ribiere versions of the conjugate gradient method (CGM). Effects of geometric parameters, location and number of sensors, heat flux value, error of sensors, and size of meshes are studied. Results show that as the sensors get closer to the unknown boundary, both accuracy and convergence rate of the algorithm improve. Increasing the number of sensors has a positive effect on accuracy and convergence rate, only when it is smaller than a certain number. Presence of a measurement error leads to inaccurate estimation of the geometry shape. A proper size of mesh has the best convergence and accuracy in shape identification problem.
MIXED CONVECTION-RADIATION HEAT TRANSFER IN A VENTED PARTITIONED RECTANGULAR ENCLOSURE
203-217
Ahmed
Bahlaoui
Sultan Moulay Slimane university, Faculty of Sciences and Technologies, Physics Department, UFR of Sciences and Engineering of Materials, Team of Flows and Transfers Modelling (EMET), B.P. 523, Béni-Mellal, Morocco
Abdelghani
Raji
Sultan Moulay Slimane university, Faculty of Sciences and Technologies, Physics Department, UFR of Sciences and Engineering of Materials, Team of Flows and Transfers Modelling (EMET), B.P. 523, Béni-Mellal, Morocco
Mohammed
Hasnaoui
Cadi Ayyad University, Faculty of Sciences Semlalia, Physics Department, UFR TMF, Laboratory of Fluid Mechanics and Energetics (LMFE), B.P. 2390, Marrakech, Morocco
Mohamed
Naimi
Faculty of Sciences and Technologies, Physics Department, Laboratory of Flows and Transfers Modeling (LAMET), Sultan Moulay Slimane University, B.P. 523, Beni-Mellal, Morocco
A numerical study has been performed on mixed convection coupled to radiation in a vented enclosure by a finite difference method. An external fluid flow enters the enclosure through an opening in the lower part of the left vertical wall and exits from another opening located on the upper part of the right vertical wall. The cavity is provided with an adiabatic partition of finite thickness located vertically on the upper horizontal wall. Air is considered as cooling fluid; it is radiatively non participating. The effect of the governing parameters, which are the Reynolds number, 200 ≤ Re ≤ 5000, the partition position from the inlet, 0.25 ≤ Lb ≤ 1.75, and the emissivity of the walls, 0 ≤ ε ≤ 1, on fluid flow and heat transfer characteristics are analyzed and discussed. Maximum and mean temperatures are also presented versus the controlling parameters. Results of the study show that, by an appropriate choice of the governing parameters, the heat transfer across the cavity can be enhanced and the mean and maximum temperatures could be reduced.
Magnetohydrodynamic Free Convection Heat Transfer in a Square Enclosure heated from side and cooled from the ceiling
219-226
Zeynab
Talea'pour
Department of Electrical Engineering, University of Sistan & Baluchestan, Zahedan
Mostafa
Mahmoodi
Department of Mechanical Engineering, Amirkabir University of Technology, Tehran 15875-4413,
Iran; Department of Mechanical Engineering, University of Kashan, Kashan 87317-53153, Iran
The Magnetohydrodynamic free convection fluid flow and heat transfer in a square cavity filled with a fluid with Prandtl number of Pr = 0.7 is investigated numerically. The left vertical wall and top horizontal wall of the cavity are maintained at a constant temperature Th and Tc respectively with Th > Tc. Other walls of the cavity are insulated. The governing equations written in terms of the primitive variables are solved numerically using the finite volume method and the SIMPLER algorithm. Using the developed code, a parametric study is performed, and the effects of the Rayleigh number and the Hartman number on the fluid flow and heat transfer inside the enclosure are investigated. The results show that temperature distribution and flow pattern inside the enclosure depend both the strength of the magnetic field and Rayleigh number. For all cases a clockwise primary vortex is formed inside the enclosure. The magnetic field decrease the intensity of free convection and flow velocity and for low Rayleigh numbers suppresses free convection.
ISOTHERMAL REACTIVE MIXING LAYER : NUMERICAL STUDY
227-235
Mohamed
Si-Ameur
LESEI Laboratory, Department of Mechanical Engineering, Technology Faculty, University of Batna 2, Algeria
Numerical simulations are used to study the space development of a reactive mixing layer which allows to observe the mark of the coherent structures of turbulence on the chemical activity within the flow. The chemical reactions within the shear flows are important in a broad range of applications in particular in chemical engineering and aeronautics, it greatly helps to comprehend fundamental mechanisms of turbulence. Reaction with low heat release permits to detail the interaction between flow dynamics and chemical activity. Typical reaction rate fields patterns are presented in this paper, taken into account reaction time, diffusive proprieties, dilution of reactants. Reaction develops intermittently a long the coherent structures as reaction gets faster. For slow reaction, it develops in a wide domain, which includes the eddy cores.
Basic dependence with diffusive and chemical proprieties has been highlighted through the influence of Schmidt number and stochiometric coefficients. The agreement with the experimentally results is good, particularly the growth rate of shear layer thickness and wavelength of instabilities which give rise to turbulent structures.
Performance comparison of relations for nanofluids properties in the CFD prediction of mixed convection
237-260
Mahmood
Akbari
Université de Sherbrooke
Nicolas
Galanis
THERMAUS, Département de génie mécanique, Université de Sherbrooke, Sherbrooke J1K 2R1, Quèbec, Canada
Amin
Behzadmehr
The hydrodynamic and thermal fields for laminar mixed convection of an Al2O3 nanofluid in a horizontal tube with uniform heat flux at the solid-fluid interface have been calculated for two Reynolds numbers with six different combinations of published expressions for the viscosity and conductivity. The results include velocity and temperature profiles at different axial positions, the axial evolution of the centerline velocity and temperature, as well as that of the skin friction coefficient and the velocity vectors of the buoyancy induced secondary flow. They show that the prediction of all these quantities depends considerably on the expressions used to evaluate the viscosity and conductivity of the nanofluid. For example, the predicted enhancement of the convection heat transfer coefficient due to an increase of the particle volume fraction (from 0.6% to 1.6%) varies between 2.0% and 24.1% while the corresponding increase of the pressure drop varies between 8.7% and 96.6%. Comparisons of the calculated convection heat transfer coefficient with corresponding published experimental results indicate that among the tested combinations, those including the conductivity relation give better predictions of this quantity.