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.

scholarly journals CONSTRUCTAL DESIGN APPLIED TO A FINNED CHANNEL UNDER FORCED CONVECTION FLOWS WITH DIFFERENT IMPOSED PRESSURE DROPS

2017 ◽  
Vol 16 (2) ◽  
pp. 72
Author(s):  
B. C. Feijo ◽  
F. B. Teixeira ◽  
M. S. Pereira ◽  
L. A. O. Rocha ◽  
J. N. V. Goulart ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Degrees Of Freedom ◽  
Fluid Motion ◽  
Convection Heat Transfer ◽  
Lower Surface ◽  
Pressure Drops ◽  
Constructal Design ◽  
Inlet Stream ◽  
Thermal Improvement ◽  
The Difference

This paper aims to numerically study the heat transfer in a two dimensional finned channel under laminar, incompressible and forced convective flow with adiabatic walls. The main purpose is to maximize the convection heat transfer by changing the fin’s dimensions by means of Constructal Design. Numerical computations are performed for different Bejan numbers ranging from 0.182 up to 18.2. For all simulations the Prandlt number is kept constant, Pr = 0.71. The fluid motion throughout the channel is caused by imposition of pressure difference between inlet/outlet surfaces. Concerning heat transfer, it is caused by the difference of temperature between the inlet stream of fluid and the heated fins placed at the channel surfaces. The first fin is positioned in the lower surface of the channel while the second one is placed in the upper one. The problem is submitted to three constraints, the channel area (H × L), area of two fins and occupancy areas for the fins. It is considered here that both fins have the same fraction area (ratio between the fins and occupancy areas) f = 0.2. The problem is submitted to three degrees of freedom: H/L (ratio between height and length of channel), H3/L3 and H4/L4 which represent the ratio between the height and length of the first and second fin, respectively. Here, the second fin remains unchanged, being its dimensions H4/L4 = 2.0, whereas the first one is free to modify its dimensions, H3/L3. The channel dimensions are also constant. The solutions are sought using the conservation equations of mass, momentum and energy being these ones discretized through the Finite Volume Method (FVM). Results showed the importance of Constructal Design application for thermal improvement of the problem. Thermal efficiency differences of 5 times where achieved when comparing the best and worst cases. Other important observation is concerned with the effect of ratio H3/L3 over heat transfer ratio (q) which varied significantly from a case where a pressure drop is imposed in the channel to other case where the driven force is caused by imposition of velocity field at the channel inlet.

scholarly journals Numerical study of forced convection heat transfer over three cylinders in staggered arrangement immersed in porous media

2018 ◽  
Vol 22 (1 Part B) ◽  
pp. 467-475 ◽  
Author(s):  
Habib-Olah Sayehvand ◽  
Sakene Yari ◽  
Parsa Basiri
Keyword(s):  
Heat Transfer ◽  
Porous Media ◽  
Forced Convection ◽  
Numerical Study ◽  
Convection Heat Transfer ◽  
Circular Cylinders ◽  
Convection Heat ◽  
State Equations ◽  
Forced Convection Heat Transfer ◽  
Staggered Arrangement

Staggered arrangement is one of the common configurations in heat exchangers that make better mixing of flow and heat transfer augmentation than other arrangements. In this paper forced convection heat transfer over three isothermal circular cylinders in staggered configuration in isotropic packed bed was investigated. In this work laminar 2-D incompressible steady-state equations of momentum and energy were solved numerically by finite volume method. Simulation was done in three Reynolds numbers of 80, 120, and 200. The results indicate that, using porous medium the Nusselt number enhanced considerably for any of cylinders and it presents thin temperature contours for them. Also is shown that by increasing Reynolds number, the heat transfer increased in both channel but the growth rate of it in porous media is larger. In addition, results of simulation in porous channel show that with increasing Peclet number, heat transfer increased logarithmically.

Geometrical Evaluation of a Pair of Elliptical Tubes Subjected to a Flow with Forced Convection Heat Transfer

2019 ◽  
Vol 396 ◽  
pp. 155-163
Author(s):  
Ana Paula Del Aghenese ◽  
Eliander Manke Heinemann ◽  
Gabriel de Avila Barreto ◽  
Filipe Branco Teixeira ◽  
Liércio André Isoldi ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Forced Convection ◽  
Degrees Of Freedom ◽  
Fluid Dynamic ◽  
Convection Heat Transfer ◽  
Numerical Approach ◽  
Angle Of Incidence ◽  
Prandtl Numbers ◽  
Forced Convective Flow ◽  
Volume Method

In the present work it is performed a study on the geometric evaluation of a pair of elliptical tubes subjected to external flow with forced convection by means of numerical approach. The objectives are the maximization of Nusselt number (NuD) and the minimization of drag coefficient (CD). The degrees of freedom for the pair of tubes arrangement are: the ratio between the transverse pitch and characteristic length of tubes (ST/D), where D = (A)1/2, the ratio of the main and secondary axes of the elliptical tube (a/b) and the angle of incidence of the flow on the pair of tubes (α). The simulations were carried out considering two-dimensional forced convective flows, in the laminar regime and incompressible conditions. For all configurations, Reynolds and Prandtl numbers are constant, ReD = 100 and Pr = 0.71. The Finite Volume Method (FVM) is used to solve conservation equations of mass, momentum and energy. The software Gmsh is used for creation of the geometries and generation of the meshes. Results showed that the degrees of freedom affected the fluid dynamic and thermal performance of the forced convective flow. According to the objectives outlined in this study, the best performance for the maximization of heat transfer was obtained when α = 0o, a/b = 1⁄2 and ST/D = 3.5. In the case of the fluid dynamics study, the optimal result for CD minimization occurred when α = 0o, a/b = 2.0 and ST/D = 4.0. Thus, the optimal geometry will depend on the indicator performance where the problem is evaluated.

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