scholarly journals GEOMETRIC EVALUATION OF COMPLEX CAVITY INTRUDED IN HEAT GENERATED WALLS

2017 ◽  
Vol 16 (1) ◽  
pp. 31
Author(s):  
M. V. F. Guimaraes ◽  
L. R. Emmendorfer ◽  
J. F. Prolo Filho ◽  
E. D. dos Santos
Keyword(s):  
Degrees Of Freedom ◽  
Numerical Study ◽  
Heat Diffusion ◽  
The Finite Element Method ◽  
Heat Diffusion Equation ◽  
Constructal Design ◽  
High Magnitude ◽  
Optimal Shapes ◽  
Complex Cavity ◽  
Volumetric Heat Generation

In this work it is presented a numerical study about geometrical evaluation of heat transfer in solids with volumetric heat generation and complex intruded cavity for cooling the wall by means of Constructal Design. Several cavities with varied shapes have been evaluated in literature, such as I-, T- and H-shaped cavities. The purpose here is to evaluate a complex cavity that combines different elemental shapes. More precisely, the resultant cavity is a merge between a H-shaped cavity and a I-shaped one, forming a ramified geometry, which is more expected in the flow between a point and volume in systems with high magnitude. The main purpose is to minimize two times the maximal temperature in the solid domain (Tmax). Here two degrees of freedom are defined for the cavity: H1/L1 (ratio between the second branch thickness and its length) and H0/L0 (ratio between the third branch height and its thickness) and the area of cavity is the constraint. For each geometrical configuration the heat diffusion equation is solved with the Finite Element Method (FEM). Results showed that differences of until five times between the optimal shapes and the worst ones are achieved, showing the importance of application of Constructal Design in the problem. Moreover, the best performance is achieved when the vertical branches are fully intruded in the solid domain for intermediate lengths of horizontal branch.

scholarly journals Thermal Influence Analysis of Coatings and Contact Resistance in Turning Cutting Tool using Comsol

2021 ◽  
Author(s):  
Carlos Adriano Ribeiro ◽  
João Roberto Ferreira ◽  
Sandro Metrevelle Marcondes Lima e Silva
Keyword(s):  
Contact Resistance ◽  
Cutting Tools ◽  
Heat Diffusion ◽  
The Finite Element Method ◽  
Machining Processes ◽  
Transient Heating ◽  
Heat Diffusion Equation ◽  
Tool Holder ◽  
Thermal Influence ◽  
Cutting Speeds

Abstract In machining processes, cutting tools reach temperatures higher than 900ºC, thus deteriorating their mechanical properties. To reduce this problem, cutting tools are coated with materials possessing thermal insulation characteristics. Such coatings benefit machining, providing faster cutting speeds and tools life. However, the heating of the tools is still present. Therefore, this work simulates the transient heating phenomenon of a tool and its tool holder, considering the presence of the coating. The effects of convection, radiation, and contact resistance between the tool and the tool holder are also considered. The thermophysical properties of the tool elements depend on temperature. Experimental measurements of parameters related to contact resistance were carried out to make the thermal model closer to real situations. The COMSOL program was used to solve the heat diffusion equation using the Finite Element Method. Comparisons of calculated temperatures are presented for the uncoated (substrate only) and coated inserts with aluminum oxide (Al2O3) and titanium nitride (TiN), respectively. Finally, the results and the consequences of the assembly parameters in the fields of temperature and contact resistance are discussed.

scholarly journals A Numerical Study of Diffusion of Nanoparticles in a Viscous Medium During Solidification

2018 ◽  
Vol 11 (1) ◽  
Author(s):  
Kazi M. Rahman ◽  
M. Ruhul Amin ◽  
Ahsan Mian
Keyword(s):  
Fluid Flow ◽  
Marangoni Number ◽  
Numerical Study ◽  
Control Volume ◽  
Mathematical Formulation ◽  
Heat Diffusion ◽  
Solidification Time ◽  
Original Position ◽  
Heat Diffusion Equation ◽  
Metal Matrix Nanocomposites

Abstract In the field of additive manufacturing process, laser cladding is widely considered due to its cost effectiveness, small localized heat generation, and full fusion to metals. Introducing nanoparticles with cladding metals produces metal matrix nanocomposites, which in turn improves the material characteristics of the clad layer. The governing equations that control the fluid flow are standard incompressible Navier–Stokes and heat diffusion equation, whereas the Euler–Lagrange approach has been considered for particle tracking. The mathematical formulation for solidification is adopted based on enthalpy porosity method. Liquid titanium has been considered as the initial condition where particle distribution has been assumed uniform throughout the geometry. A numerical model implemented in a commercial software based on control volume method has been developed, which allows to simulate the fluid flow during solidification as well as tracking nanoparticles during this process. A detailed parametric study has been conducted by changing the Marangoni number, convection heat transfer coefficient, constant temperature below the melting point of titanium, and insulated boundary conditions to analyze the behavior of the nanoparticle movement. The influence of increase in Marangoni number results in a higher concentration of nanoparticles in some portions of the geometry and lack of nanoparticles in rest of the geometry. The high concentration of nanoparticles decreases with a decrease in Marangoni number. Furthermore, an increase in the rate of solidification time limits the nanoparticle movement from its original position which results in different distribution patterns with respect to the solidification time.

Analysis of Geometric Variation of Three Degrees of Freedom through the Constructal Design Method for a Oscillating Water Column Device with Double Hidropneumatic Chamber

2019 ◽  
Vol 396 ◽  
pp. 22-31
Author(s):  
Yuri T.B. Lima ◽  
Mateus das Neves Gomes ◽  
Camila F. Cardozo ◽  
Liércio André Isoldi ◽  
Elizaldo D. Santos ◽  
...  
Keyword(s):  
Water Column ◽  
Degrees Of Freedom ◽  
Numerical Study ◽  
Design Method ◽  
Geometric Optimization ◽  
Oscillating Water Column ◽  
Constructal Design ◽  
Wave Energy Converters ◽  
Volume Method ◽  
Geometric Variation

This paper presents a biphasic two-dimensional numerical study of sea wave energy converters with operating principle being Oscillating Water Column (CAO) devices with two couples chambers. For the study of the geometric optimization, the Constructal Design method is applied in association with the exhaustive search method to determine the geometric arrangement that leads to the greatest hydropneumatic power available. The objective function is the maximization of hydropneumatic power converted by the device. The constraints of the problem are the inflow volumes of the hydropneumatic chamber (VE1, VE2), the total volumes (VT1, VT2) and the thicknesses of the device columns (e1, e3). The degrees of freedom analyzed were H1/L1(ratio between height and length of the hydropneumatic chamber of the first device), H2/L2 (ratio between height and length of the hydropneumatic chamber of the second device), H2 (height of the column dividing the two devices) and e2 (thickness of the column dividing the devices). In the present work the degree of freedom H6 (depth of immersion of the device) is kept constant and equal to H6 = 9.86 m. The Finite Volume Method (FVM) was used in the numerical solution of the equations employed. For the treatment of the interaction between the air and water phases, the Volume of Fluid (VOF) method was applied. The results show that the maximum hydropneumatic power available was 5715.2 W obtained for degrees of freedom H1/L1 = H2/L2 = 0.2613 and e2 = 2.22 m. The case of lower performance has a power value equal to 4818.5 W with degrees of freedom equal to H1/L1 = H2/L2 = 0.2613 and e2 = 0.1 m.

scholarly journals GEOMETRIC EVALUATION OF FOUR STAGGERED CYLINDERS ARRAY SUBJECTED TO FORCED CONVECTIVE FLOWS BY MEANS OF CONSTRUCTAL DESIGN

2019 ◽  
Vol 18 (1) ◽  
pp. 57
Author(s):  
A. P. D. Aghenese ◽  
F. B. Teixeira ◽  
L. A. O. Rocha ◽  
L. A. Isoldi ◽  
J. F. Prolo Filho ◽  
...  
Keyword(s):  
Degrees Of Freedom ◽  
Numerical Study ◽  
Design Method ◽  
Fluid Dynamic ◽  
Working Fluid ◽  
Convective Flows ◽  
Constructal Design ◽  
Staggered Arrangement ◽  
Forced Convective Flow ◽  
Volume Method

This work presents a numerical study on the geometric evaluation of forced convective flows over four staggered arrangement of four cylinders. The forced convective flow is considered incompressible, two-dimensional, laminar and unsteady. Geometry varies according to Constructal Design method. The objectives are the maximization of Nusselt number (NuD) and minimization of drag coefficient (CD) between the cylinders and the surrounding flow. Simulations were performed considering Reynolds numbers of ReD = 10, 40 and 150 and air as working fluid, i.e., Prandtl number is assumed Pr = 0.71. The problem presents three degrees of freedom: ST/D (ratio between transversal pitch of the intermediate cylinders and the cylinders diameter), SL1/D (ratio between the frontal and intermediate cylinders longitudinal pitch and the cylinders diameter) and SL2/D (ratio between the intermediate and posterior cylinders longitudinal pitch and the cylinders diameter). However, SL1/D and SL2/D measures were kept fixed at 1.5 and ST/D varies in the range 1.5 ≤ ST/D ≤ 5.0. The conservation equations of mass, momentum and energy conservation are solved with the Finite Volume Method (FVM). Optimal results for fluid-dynamic study in all ReD cases occurred for the lowest values of ST/D, i.e., (ST/D)o,f = 1.5. For thermal analysis, NuD behavior was assessed, where optimal results for ReD = 10 and 40 occurred for the highest values of ST/D, whilst, for ReD = 150, the optimal value was achieved for the intermediate ratio of ST/D = 4.0.

Constructal Design Associated to Genetic Algorithm of Asymmetric V-Shaped Pathways

2015 ◽  
Vol 137 (6) ◽  
Author(s):  
Emanuel da S. D. Estrada ◽  
Tadeu M. Fagundes ◽  
Liércio A. Isoldi ◽  
Elizaldo D. dos Santos ◽  
Gongnan Xie ◽  
...  
Keyword(s):  
Genetic Algorithm ◽  
Thermal Resistance ◽  
Degrees Of Freedom ◽  
Volume Fraction ◽  
Geometric Optimization ◽  
Heat Sinks ◽  
Heat Generation Rate ◽  
Conductive Materials ◽  
Constructal Design ◽  
Optimal Shapes

This work relies on constructal design to perform the geometric optimization of the V-shaped pathways of highly conductive materials (inserts) that remove a constant heat generation rate from a body and deliver it to isothermal heat sinks. It is shown numerically that the global thermal resistance of the V-shaped pathway can be minimized by geometric optimization subject to total volume and V-shaped pathways material constraints. Constructal design and genetic algorithm (GA) optimization showed the emergence of an optimal architecture that minimizes the global thermal resistance: an optimal external shape for the assembly of pathways and optimal geometry features for the V-shaped pathway. Parametric study was performed to show the behavior of the minimized global thermal resistance as function of the volume fraction of the V-shaped pathways. First achieved results for ϕ = 0.3 indicated that when freedom is given to the geometry, the thermal performance is improved. Afterward, the employment of GA with constructal design allowed the achievement of the optimal shapes of V-shaped pathways for different volume fractions (0.2 ≤ ϕ ≤ 0.4). It was not realized the occurrence of one universal optimal shape for the several values of ϕ investigated, i.e., the optimal design was dependent on the degrees of freedom and the parameter ϕ and it is reached according to constructal principle of optimal distribution of imperfections.

scholarly journals Calculating the Dynamic Impedances of Foundations and their Effect on the Seismic Response of Structures: Analytical and Numerical Study

2021 ◽  
Vol 31 (2) ◽  
pp. 178-217
Author(s):  
Radhwane Boulkhiout ◽  
Salah Messast
Keyword(s):  
Degrees Of Freedom ◽  
Numerical Study ◽  
Displacement Vector ◽  
Soft Soil ◽  
The Finite Element Method ◽  
Rheological Models ◽  
Soil Densification ◽  
Structure Height ◽  
Impedance Functions ◽  
Numerical Program

Abstract This study evaluates the movement of a frame built on soft soil under seismic excitation taking into account soil-structure interaction. First, the study was evaluated using the finite element method, then, by using a substructure method which modelled the soil using springs and dampers in a linear and nonlinear study. Rheological models were determined using impedance functions, calculated using a numerical program CONAN. These dynamic impedances are shown in the displacement vector of a three-degrees-of-freedom frame, which was calculated on the basis of lateral forces distributed over the structure height using the equivalent static method. In this regard, two different calculation norms were chosen; RPA2003 and UBC97. Finally, a parametric study was carried out, based on the effects of soil densification and the foundation geometry on the response of the RC frame.

scholarly journals CONSTRUCTAL DESIGN OF A VORTEX TUBE FOR SEVERAL INLET STAGNATION PRESSURES

2012 ◽  
Vol 11 (1-2) ◽  
pp. 85 ◽  
Author(s):  
C. H. Marques ◽  
L. A. Isoldi ◽  
E. D. Dos Santos ◽  
L. A. O. Rocha
Keyword(s):  
Turbulent Flows ◽  
Degrees Of Freedom ◽  
Vortex Tube ◽  
Numerical Study ◽  
Cylindrical Tube ◽  
Navier Stokes ◽  
Working Fluid ◽  
Computational Domain ◽  
Constructal Design ◽  
Volume Method

The present paper shows a numerical study concerned with the geometrical optimization of a vortex tube device by means of Constructal Design for several inlet stagnation pressures. In the present study, it is evaluated a vortex tube with two-dimensional axisymmetric computational domain with dry air as the working fluid. The compressible and turbulent flows are numerically solved with the commercial CFD package FLUENT, which is based on the Finite Volume Method. The turbulence is tackled with the k-ε model into the Reynolds Averaged Navier-Stokes (RANS) approach. The geometry has one global restriction, the total volume of the cylindrical tube, and four degrees of freedom: d3/D (the ratio between the diameter of the cold outlet and the diameter of the vortex tube), d1/D (the ratio between the diameter of the inlet nozzle and the diameter of the vortex tube), L2/L (the ratio between the length of the hot exit annulus and the length of the vortextube) and D/L (the ratio between the diameter of the vortex tube and its length). The degree of freedom L2/L will be represented here by the cold mass fraction (yc). In the present work it is optimized the degrees of freedom yc and d3/D while the other degrees of freedom and the global restriction are kept fixed. The purpose here is to maximize the amount of energy extracted from the cold region (cooling effect) for several geometries, as well as, investigate the influence of the inlet stagnation pressure over the optimal geometries. Results showed an increase of the twice maximized cooling heat transfer rate of nearly 330 % from 300 kPa to 700 kPa. Moreover, the optimization showed a higher dependence of (d3/D)o for the lower range of inlet pressures, while the optimization is more dependent of yc,oo for higher inlet stagnation pressures.

Constructal Design Applied to the Geometric Optimization of Y-shaped Cavities Embedded in a Conducting Medium

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
G. Lorenzini ◽  
C. Biserni ◽  
L. A. Isoldi ◽  
E. D. dos Santos ◽  
L. A. O. Rocha
Keyword(s):  
Thermal Resistance ◽  
Degrees Of Freedom ◽  
Vertical Direction ◽  
Optimization Procedure ◽  
Power Laws ◽  
Geometric Optimization ◽  
Constructal Design ◽  
Conducting Wall ◽  
Geometric Conditions ◽  
Optimal Shapes

In this paper, we rely on the Constructal method to optimize the geometry of a Y-shaped cavity embedded into a solid conducting wall. The structure has four degrees of freedom. The objective is to minimize the global thermal resistance between the solid and the cavity. The optimization procedure has demonstrated that for larger solids, a cavity shaped as T led to a minimization of the global thermal resistance, while the opposite effect is observed for tall solids, where the optimal shapes are reached when the bifurcated branches deeply penetrates the solid in the vertical direction, according to the Constructal principle of “optimal distribution of imperfections”. The three times minimized global thermal resistance of the Y-shaped cavity has been correlated by power laws as a function of its corresponding optimal configurations. Finally, the performance of the Y-shaped intrusion proved to be superior to that of other basic geometries: the optimized global thermal resistances of the Y-shaped cavities obtained for H/L = 1.0, 2.0, and 5.0 were, respectively 66.61%, 55.37%, and 19.05% lower than the optimal T-shaped cavities under the same thermal and geometric conditions. Furthermore, in comparison with the “finger cavity” shaped as C, the Y-shaped cavities increased the thermal performance in 109.12%, 84.45%, 59.32%, and 20.10% for H/L = 0.5, 1.0, 2.0, and 5.0, respectively.

Constructal Design Applied to a Channel with Triangular Fins Submitted to Forced Convection

2017 ◽  
Vol 372 ◽  
pp. 152-162 ◽  
Author(s):  
Bruno Costa Feijó ◽  
Martim dos Santos Pereira ◽  
Filipe Branco Teixeira ◽  
Liércio André Isoldi ◽  
Luiz Alberto Oliveira Rocha ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamics ◽  
Forced Convection ◽  
Degrees Of Freedom ◽  
Numerical Study ◽  
Design Method ◽  
Convection Heat Transfer ◽  
Lower Surface ◽  
Worst Case ◽  
Constructal Design

The purpose of this work is to present a numerical study of a two-dimensional channel with two triangular fins submitted to a laminar flow with forced convection heat transfer, evaluating the geometry of the first fin through the Constructal Design method. The main objectives are to maximize the heat transfer rate and minimize the pressure difference between the inlet and outlet flow of the channel for different dimensions of the first channel fin, considering the same Reynolds (ReH = 100) and Prandtl numbers (Pr = 0.71). The problem is subjected to three constraints given by the channel area, fin area and maximum occupancy area of ​​each fin. The system has three degrees of freedom. The first is given by the ratio between height and length of the channel, which is kept fixed, H/L = 0.0625. The other two are the ratio between height and width of the upstream fin base (H3/L3) positioned on the lower surface of the channel, and the ratio between height and width of the downstream fin (H4/L4) positioned on the upper surface of the channel, which is also kept fixed, H4/L4 = 1.11. The problem is simulated for three different values ​​of the fraction area of upstream fin (φ1 = 0.1, 0.2 and 0.3). For the numerical approach of the problem, the conservation equations of mass, momentum and energy are solved using the finite volume method (MVF). The results showed that a ratio of φ1 = 0.2 is the one that best meets the proposed multi-objective. It was also observed that φ1 = 0.1 led to a better fluid dynamics performance with a ratio between the best and the worst performance for fluid dynamics case of 25.2 times. For φ1 = 0.3, the best thermal performance is achieved, where the optimal case has a performance 65.75% higher than that reached for the worst case.

Design of Cooling Cavities by the Application of the Constructal Design

2017 ◽  
Vol 372 ◽  
pp. 163-169
Author(s):  
Júlio César Burlamaqui Vianna ◽  
Emanuel da Silva Diaz Estrada ◽  
Liércio André Isoldi ◽  
Elizaldo Domingues dos Santos ◽  
Jeferson Avila Souza
Keyword(s):  
Hot Spots ◽  
Numerical Study ◽  
Internal Heat ◽  
Constructal Theory ◽  
Maximum Temperature ◽  
The Finite Element Method ◽  
Constructal Design ◽  
Solid Geometry ◽  
Building Process ◽  
Solid Bodies

This paper develops a numerical study about the geometry of isothermal cavities in solid bodies with internal heat generation. The solid is constituted of a isotropic material, with low thermal conductivity, and adiabatic external surfaces. The cavity is used to dissipate the internally generated heat. An evolutionary algorithm is proposed, based on Constructal Theory, that builds a cavity able to maximize the heat transfer between the solid body and the ambient. Initial solid geometry (a squared fin) is divided into smaller squared elements (regions) that will be remove in order to build the cavity. First element is removed from the bottom center of the geometry and other elements are, at every step, removed so that minimize the hot spots in the solid domain. At every stage of the building process, thermal diffusion equation is numerically solved by the finite element method (FEM). The cavity construction must be flexible so that it freely progresses (evolves) in direction to the hot spots. Results show that the smaller the elements (resolution) used in the cavity construction the lower will be the maximum temperature. Besides that, present results are compare with similar works for cavities C, H, X e Y, presented in literature, showing that current methodology is very efficient in minimizing maximum solid internal temperature.

Sign in / Sign up

Export Citation Format

Share Document