Begell House Inc.
Computational Thermal Sciences: An International Journal
CTS
1940-2503
4
2
2012
NUMERICAL SIMULATION OF HIGH-PRESSURE AND - TEMPERATURE WATER IN A 2 MM PIPE: WHAT IS THE CONDITION FOR THE RAPID INCREASE IN TEMPERATURE?
99-106
Yoshio
Masuda
National Institute of Advanced Industrial Science and Technology (AIST), Miyagi Sendai 4-2-1, Nigatake, Miyagino-ku, Japan
Osamu
Sato
National Institute of Advanced Industrial Science and Technology (AIST), Miyagi Sendai 4-2-1, Nigatake, Miyagino-ku, Japan
Takafumi
Aizawa
National Institute of Advanced Industrial Science and Technology (AIST), Miyagi Sendai 4-2-1, Nigatake, Miyagino-ku, Japan
Masayuki
Shirai
National Institute of Advanced Industrial Science and Technology (AIST), Miyagi Sendai 4-2-1, Nigatake, Miyagino-ku, Japan
Akira
Suzuki
National Institute of Advanced Industrial Science and Technology (AIST), Miyagi Sendai 4-2-1, Nigatake, Miyagino-ku, Japan
A model of a supercritical water microreactor has been numerically simulated. The fluid flow with natural convection and temperature fields is calculated for four types of mixing patterns. Further, we discuss the fine mixing pattern for the rapid heating of a substrate. When forced convection is dominant, employing a method in which hot and cold water are mixed well yields good results. Further, it is preferable to avoid the case in which the inlet of the substrate is above the mixing point since natural convection reaches near the inlet of the substrate and the temperatures of the particles increase.
COMPUTATIONAL AND EXPERIMENTAL INVESTIGATION ON THERMAL INSULATION CAPABILITIES OF RICE-HUSK FILLED EPOXY COMPOSITES
107-114
Arun Kumar
Rout
Department of Production Engineering, Veer Surendra Sai University of Technology, Burla-768018, India
Alok
Satapathy
Department of Mechanical Engineering, National Institute of Technology, Rourkela 769008, India
The finite-element method (FEM) is a powerful computational technique for approximate solutions to a variety of engineering problems having complex domains subjected to general boundary conditions. In this paper FEM is implemented to determine the effective thermal conductivity of rice-husk filled polymer composites and is validated by experimentation. A commercially available finite-element package (ANSYS) is used to for this numerical analysis. Three-dimensional spheres-in-cube lattice array models are constructed to simulate the microstructure of composite materials for various filler concentrations ranging from about 0 to 6.5 vol. %. Composites with similar filler contents are fabricated by the hand layup technique by reinforcing microsized rice husk in epoxy resin. The guarded heat flow meter test method is used to measure the thermal conductivity of these composites using the instrument UnithermTMmodel 2022 as per ASTM-E1530. This study shows that the incorporation of rice husk results in reduction of conductivity of epoxy resin and thereby improves its thermal insulation capability. With the addition of 6.5 vol. % of filler, the thermal conductivity of epoxy is found to decrease by about 8.26%. The experimentally measured conductivity values are compared with the numerically calculated ones and also with the existing theoretical and empirical models. The values obtained using finite-element analysis (FEA) are found to be in reasonable agreement with the experimental values.
Preface
117
Antonio Ferreira
Miguel
Department of Physics, School of Sciences and
Technology, University of Evora, Institute of Earth Sciences (ICT) Pole of Evora,
Portugal
Andreas
Ochsner
Centre for Mass and Thermal Transport in Engineering Materials, The University of Newcastle, Callaghan ; Department of Solid Mechanics and Design, Faculty of Mechanical Engineering, University of Technology Malaysia - UTM UTM Skudai, Johor, Malaysia; Griffith University, Australia
Preface
Special Issue on Fluid Flow: Analysis and Numerics
GEOMETRIC OPTIMIZATION BASED ON THE CONSTRUCTAL DESIGN OF PERFORATED THIN PLATES SUBJECT TO BUCKLING
119-129
Luiz Alberto O.
Rocha
Programa de Pos-Graduacao em Engenharia Mecanica,
Universidade Federal do Rio Grande do Sul Porto Alegre, Brazil, Rua Sarmento Leite, 425, 90.050-170
M. V.
Real
Programa de Pos-Graduacão em Engenharia Oceânica (PPGEO), Escola de Engenharia (EE), Universidade Federal do Rio Grande (FURG), Rio Grande do Sul, Brazil
A. L. G.
Correia
Programa de Pos-Graduacão em Engenharia Oceânica (PPGEO), Escola de Engenharia (EE), Universidade Federal do Rio Grande (FURG), Rio Grande do Sul, Brazil
J.
Vaz
Programa de Pos-Graduacão em Engenharia Oceânica (PPGEO), Escola de Engenharia (EE), Universidade Federal do Rio Grande (FURG), Rio Grande do Sul, Brazil
E. D.
dos Santos
Universidade Federal do Rio Grande (FURG), Escola de Engenharia (EE), Programa de Pos-Graduacao em Engenharia Oceanica (PPGEO), Rio Grande, Rio Grande do Sul, Brazil
L. A.
Isoldi
Universidade Federal do Rio Grande (FURG), Escola de Engenharia (EE), Programa de Pos-Graduacao em Engenharia Oceanica (PPGEO), Rio Grande, Rio Grande do Sul, Brazil
Elastic buckling is an instability phenomenon that can occur if a slender and thin-walled plate is subjected to axial compressive load. It is well known that the presence of holes in structural plate elements is almost inevitable in inspection, maintenance, and service purposes, or to reduce the structural weight. In this paper constructal design was employed to optimize the geometry of thin perforated plates submitted to elastic buckling. Simply supported rectangular perforated plates were analyzed with three different shapes of centered holes: elliptical, rectangular, and diamond. The purpose was to obtain the optimal geometry that maximizes the critical buckling load. The ratio between the height and length of the plate was kept constant, while the ratio between the characteristic dimensions of the holes was optimized for several hole volume fractions (φ). A finite-element model was used to assess the plate buckling load, and the Lanczos method was applied to the solution of the corresponding eigenvalue problem. When φ ≤ 0.20 the optimum geometry is the diamond hole, reaching maximum buckling loads around 80.0,21.5, and 17.4% higher than a plate without perforation and plates with elliptical and rectangular holes, respectively. For intermediate and higher values of φ, the elliptical and rectangular holes, respectively, led to the best performance. The optimal shapes were obtained according to the constructal principle of minimization of distribution of imperfections, showing that the constructal design also can be employed to define the optimized geometries in the mechanics of material problems.
A LATTICE MONTE CARLO ANALYSIS ON CHEMICAL REACTION WITH MOVING BOUNDARY
131-135
Thomas
Fiedler
Centre for Mass and Thermal Transport in Engineering Materials, The University of Newcastle, Callaghan, School of Engineering, NSW 2308, Australia
Irina V.
Belova
Centre for Mass and Thermal Transport in Engineering Materials, The University of Newcastle, Callaghan, School of Engineering, NSW 2308, Australia
Andreas
Ochsner
Centre for Mass and Thermal Transport in Engineering Materials, The University of Newcastle, Callaghan ; Department of Solid Mechanics and Design, Faculty of Mechanical Engineering, University of Technology Malaysia - UTM UTM Skudai, Johor, Malaysia; Griffith University, Australia
Graeme
Murch
Centre for Mass and Thermal Transport in Engineering Materials, The University of Newcastle, Callaghan, School of Engineering, NSW 2308, Australia
The current paper aims to simulate combined mass diffusion and chemical reaction. Two solid reactants are brought into contact and the product is formed at the interface. Chemical reaction is assumed to occur instantaneously, thus the reaction rate is limited only by the interdiffusion of the two solid constituents. First, parametric studies for a range of constant diffusivities are performed and simple relations for the growth of the product phase are obtained. It is found that the thickness of the product layer increases proportionally to the square root of the product of diffusivity and time. In the second part of the analyses the formation of NiAl by interdiffusion of nickel and aluminum is simulated. This self-propagating exothermic reaction is of great interest for joining temperature-sensitive components. Within the limits of these calculations, the concentration dependence of the diffusion coefficients of nickel and aluminum is considered in order to improve the accuracy of the simulation.
1D AND 2D MODELING AND SIMULATION OF RADIAL COMBUSTION PROPAGATION ON Fe2O3/Al THERMITE SYSTEMS
137-149
P.
Brito
CIEPQPF, Department of Chemical Engineering, Faculty of Sciences and Technology, University of Coimbra, Polo II, Rua Silvio Lima, 3030-790 Coimbra, Portugal ; Department of Chemical and Biological Technology, School of Technology and Management,
Luisa
Duraes
CIEPQPF, Department of Chemical Engineering, Faculty of Sciences and Technology, University of Coimbra, Polo II, Rua Silvio Lima, 3030-790 Coimbra, Portugal
A.
Portugal
CIEPQPF, Department of Chemical Engineering, Faculty of Sciences and Technology, University of Coimbra, Polo II, Rua Silvio Lima, 3030-790 Coimbra, Portugal
In previous works, a one-dimensional model was built to simulate the nonsteady radial combustion propagation on thin disk-shaped samples of Fe2O3/aluminum thermite mixtures and was successfully tested. Now, the purpose is to extend the referred model to the more sensible two-dimensional features of the samples, maintaining the main characteristics of the previous model: zero-order kinetics, conductive/radiative heat transfer, assumption of phase transitions, temperature and composition dependency for all system properties during propagation. Therefore, an adaptive numerical algorithm that conjugates a method of lines (MOL) strategy based on finite differences space discretizations, with a collocation scheme based on increasing level dyadic grids is applied for the solution of the problem. The particular integration method proves to cope satisfactorily with the steep traveling thermal wave in 1D and 2D spatial domains, either for trivial uniform mixing conditions, as in complex examples developed to feature more sophisticated circumstances, such as nonhomogeneous reactant mixing, which realistically replicate the observed experimental conditions.
EFFECTS OF RADIAL FINS ON THE LAMINAR NATURAL CONVECTION OF A NANOFLUID IN CONCENTRIC ANNULI
151-158
Ghanbar Ali
Sheikhzadeh
Department of Mechanical Engineering, University of Kashan, Kashan, Iran
Maryam
Arbaban
Isfahan University Of Technology
A.
Arefmanesh
Department of Mechanical Engineering, University of Kashan, Iran
The laminar natural convection of the Cu-water nanofluid between two horizontal concentric cylinders with four radial fins attached to the inner cylinder is studied numerically. The governing equations with the respective boundary conditions are solved by using the finite volume method and the SIMPLER algorithm. The computations are performed for various Rayleigh numbers, fin lengths, and thermal conductivity ratios. The results presented in this study are for a range of Rayleigh numbers from 103 to 105, dimensionless lengths of the fins between 0.1 to 0.4, and two thermal conductivity ratios, namely, 100 and 654. It is observed from the results that the average Nusselt number decreases with increasing the fins' lengths. However, the heat transfer rate and the average Nusselt number increase by increasing the fins' thermal conductivity at high Rayleigh numbers.
NATURAL CONVECTION IN A NANOFLUID-FILLED SQUARE CAVITY WITH AN ARC-SHAPED HEATED BAFFLE
159-168
Ali Akbar
Abbasian Arani
Mechanical Engineering Departement, University of Kashan, Kashan, Iran
Ehsan
Roohi
Mechanical Engineering Departement, University of Kashan, Kashan, Iran
Buoyancy driven natural convection in a nanofluid-filled square cavity induced by an arc-shaped heated baffle is analyzed numerically. Upper and bottom walls of the cavity are insulated and the remaining two walls have constant temperature; their values are lower than the baffle's temperature. The calculations were performed for various values of Rayleigh number (104 « (Ra) « 106) dimensionless arc length (0.25 « S « 0.75), shape parameter of the baffle (π/4 « Θ « π), types of nanoparticles (Cu, Al2O3) in a wide range of solid volume fraction of nanoparticles (0 « φ « 0.15). It is found that the net heat transfer can be enhanced by increasing the Rayleigh number, baffle length, and shape parameter. As the baffle length is increased for a fixed Rayleigh number, the average Nusselt number increases and for a fixed baffle length when the Rayleigh numbers are increased, the average Nusselt number also increases. The addition of copper and alumina Nanoparticles has produced a remarkable enhancement of the heat transfer. The average Nusselt number increases with increasing solid volume fraction of nanoparticles, especially at low Rayleigh numbers. Adding Al2 O3 increases the heat transfer rate but the influence of adding Cu nanoparticles to pure water on the heat transfer rate is much more pronounced because of its higher value of thermal conductivity compared to Al2O3. The difference in the average Nusselt number using different nanoparticles is negligible at low solid volume fractions, but as the volume fraction of nanoparticles increases, the difference for the mean Nusselt number becomes larger. This is similar to results which were obtained by other authors.
MODELING OF VIRTUAL PARTICLES OF THE BIG BANG
169-181
R. Leticia
Corral-Bustamante
Technological Institute of Cuauhtemoc City, Tecnológico Ave. S/N, Z.P. 31500, Cuauhtemoc City, Chihuahua, Mexico
Aaron Raul
Rodriguez-Corral
Autonome University of Chihuahua City, Av. Escorza No. 900, Z.P. 31000, Chihuahua City, Mexico
Teresita de Jesus
Amador-Parra
Technological Institute of Cuauhtemoc City, Tecnológico Ave. S/N, Z.P. 31500, Cuauhtemoc City, Chihuahua, Mexico
Eva
Martinez-Loera
Technological Institute of Cuauhtemoc City, Tecnológico Ave. S/N, Z.P. 31500, Cuauhtemoc City, Chihuahua, Mexico
Gilberto
Irigoyen-Chavez
Technological Institute of Cuauhtemoc City, Tecnológico Ave. S/N, Z.P. 31500, Cuauhtemoc City, Chihuahua, Mexico
In this work, a mathematical model in four dimensions proposed to predict the behavior of the transport phenomena of mass (energy) in the space-time continuum through a metric tensor in the Planck scale is presented. The Ricci tensor was determined with the aim of measuring the turbulent flow of a mass with a large gravitational field similar to that which is believed to have existed in the Big Bang. Computing the curvature of space-time through tensor analysis, we predict a vacuum solution of the Einstein field equations through numerical integration with approximate solutions. A quantum vacuum is filled with virtual particles of enormous superficial gravity of black holes and wormholes as predicted by other authors. By generating the geodesic equations, we obtain the relativistic equation, which is the carrier of information pertaining to the behavior of the entropy of matter The results of the measurements of the evolution of the mass during its collapse and evaporation allow us to argue the evidence of virtual particles including all the values (and beyond) of the experimental search by other authors for gauges and Higgs bosons. We conclude that the matter behaves as virtual particles, which appear and disappear in Planck time at speeds greater than that of light, representing those that probably existed during the Big Bang.