Geometry Evaluation of Heat Transfer by Mixed Convention in Driven Cavities with Two Inserted Fins

2019 ◽  
Vol 396 ◽  
pp. 164-173 ◽  
Author(s):  
Priscila M. Rodrigues ◽  
Cicero C. de Escobar ◽  
Luiz Alberto Oliveira Rocha ◽  
Liércio André Isoldi ◽  
Elizaldo Domingues dos Santos
Keyword(s):  
Heat Transfer ◽  
Degrees Of Freedom ◽  
Numerical Study ◽  
Lower Surface ◽  
Stable Stratification ◽  
Geometric Constraints ◽  
Driven Cavity ◽  
Geometric Configurations ◽  
Two Dimensional Flow ◽  
Volume Method

In this work, a numerical study of a flow with heat transfer by mixed convection are carried out. The objective is the geometric evaluation through the application of the Construtal Design and the exhaustive search method. The behavior of a lid-driven cavity with stable stratification subjected to an incompressible, laminar and two-dimensional flow is investigated. The cavity has two rectangular fins inserted in the lower surface. The problem is subject to three constrains: three geometric constraints: the area of the cavity, two fin areas. The investigated geometry has three degrees of freedom: the ratio between height and cavity length (H/L) and the ratio between height and length of each fin (H1/L1 and H2/L2). The effect of the fin geometry over spatial-averaged Nusselt (NuH) is investigated for Reynolds number (ReH) = 400 and Richardson (Ri) = 0.1. The conservation equations of mass, momentum and energy are tackled with Finite Volume Method (FVM) through the use of commercial software FLUENT. The results showed that the lower H2/L2 ratios resulted in higher NuH values. An increase in NuH value of approximately 49% between the worst and the best geometrical configuration was found, thus highlighting the importance of geometric evaluation on this kind of problem. It is concluded that for the problem addressed the best behavior is obtained when the fins have a small insertion into the cavity, thus avoiding the restriction of the main vortex flow. The results found highlight the importance of the geometric evaluation for the purpose of theoretical recommendation on the geometric configurations that lead to the best thermal performance.

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.

AN EXPERIMENTAL AND NUMERICAL STUDY OF HEAT TRANSFER IN A SIMULATED COLLECTOR FOR A SOLAR DRYER

1993 ◽  
Vol 17 (2) ◽  
pp. 145-160
Author(s):  
P.H. Oosthuizen ◽  
A. Sheriff
Keyword(s):  
Heat Transfer ◽  
Numerical Study ◽  
Local Heat Transfer ◽  
Lower Surface ◽  
Local Heat ◽  
Electrical Heating ◽  
Temperature Profiles ◽  
Measured Temperature ◽  
Transfer Rates ◽  
Thermocouple Probe

Indirect passive solar crop dryers have the potential to considerably reduce the losses that presently occur during drying of some crops in many parts of the “developing” world. The performance so far achieved with such dryers has, however, not proved to be very satisfactory. If this performance is to be improved it is necessary to have an accurate computer model of such dryers to assist in their design. An important element is any dryer model is an accurate equation for the convective heat transfer in the collector. To assist in the development of such an equation, an experimental and numerical study of the collector heat transfer has been undertaken. In the experimental study, the collector was simulated by a 1m long by 1m wide channel with a gap of 4 cm between the upper and lower surfaces. The lower surface of the channel consisted of an aluminium plate with an electrical heating element, simulating the solar heating, bonded to its lower surface. Air was blown through this channel at a measured rate and the temperature profiles at various points along the channel were measured using a shielded thermocouple probe. Local heat transfer rates were then determined from these measured temperature profiles. In the numerical study, the parabolic forms of the governing equations were solved by a forward-marching finite difference procedure.

Thermal Management of Surface Mount Power Magnetic Components

1999 ◽  
Vol 122 (4) ◽  
pp. 323-327
Author(s):  
G. Refai-Ahmed ◽  
M. M. Yovanovich
Keyword(s):  
Heat Transfer ◽  
Power Loss ◽  
Numerical Study ◽  
Lower Surface ◽  
Experimental Results ◽  
Surface Mount ◽  
Conduction Heat Transfer ◽  
Magnetic Components ◽  
Underfill Material ◽  
Good Agreement

A numerical and experimental study of conduction heat transfer from low power magnetic components with gull wing leads was conducted to determine the effects of distributing the power loss between the core, the winding and the thermal underfill on the thermal resistance. The numerical study was conducted in the power loss ratio range of 0.5⩽PR⩽1.0, where the only active power loss was from the winding at PR=1. In addition, the effect of the thermal underfill material between the substrate and the lower surface of the magnetic package on the thermal performance of the magnetic device was also examined. For comparison, a test was conducted on a magnetic component at PR=1, without thermal underfill. This comparison revealed good agreement between the numerical and experimental results. Finally, a general model was proposed for conduction heat transfer from the surface mount power magnetic packages. The agreement between the model and the experimental results was within 8 percent. [S1043-7398(00)00704-0]

Effect of Periodic Imposed Heat Flux on Three-Dimensional Natural Convection in a Partially Heated Cubical Enclosure

2016 ◽  
Vol 831 ◽  
pp. 83-91
Author(s):  
Lahoucine Belarche ◽  
Btissam Abourida
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Numerical Study ◽  
Control Volume ◽  
Vertical Wall ◽  
Three Dimensional ◽  
Maximum Temperature ◽  
Cubical Enclosure ◽  
Simplec Algorithm ◽  
Volume Method

The three-dimensional numerical study of natural convection in a cubical enclosure, discretely heated, was carried out in this study. Two heating square sections, similar to the integrated electronic components, are placed on the vertical wall of the enclosure. The imposed heating fluxes vary sinusoidally with time, in phase and in opposition of phase. The temperature of the opposite vertical wall is maintained at a cold uniform temperature and the other walls are adiabatic. The governing equations are solved using Control volume method by SIMPLEC algorithm. The sections dimension ε = D / H and the Rayleigh number Ra were fixed respectively at 0,35 and 106. The average heat transfer and the maximum temperature on the active portions will be examined for a given set of the governing parameters, namely the amplitude of the variable temperatures a and their period τp. The obtained results show significant changes in terms of heat transfer, by proper choice of the heating mode and the governing parameters.

scholarly journals Effect of Heat Source Position in Fluid Flow, Heat Transfer and Entropy Generation in a Naturally Ventilated Room

Mathematics ◽  
2022 ◽  
Vol 10 (2) ◽  
pp. 178
Author(s):  
Mohammed Alghaseb ◽  
Walid Hassen ◽  
Abdelhakim Mesloub ◽  
Lioua Kolsi
Keyword(s):  
Heat Transfer ◽  
Rayleigh Number ◽  
Heat Source ◽  
Numerical Study ◽  
Temperature Fields ◽  
Left Wall ◽  
Heating Efficiency ◽  
Discrete Heat Source ◽  
Volume Method ◽  
The Impact

In this study, a 3D numerical study of free ventilated room equipped with a discrete heat source was performed using the Finite Volume Method (FVM). To ensure good ventilation, two parallel openings were created in the room. A suction opening was located at the bottom of the left wall and another opening was located at the top of the opposite wall; the heat source was placed at various positions in order to compare the heating efficiency. The effects of Rayleigh number (103 ≤ Ra ≤ 106) for six heater positions was studied. The results focus on the impact of these parameters on the particle trajectories, temperature fields and on the heat transfer inside the room. It was found that the position of the heater has a dramatic effect on the behavior and topography of the flow in the room. When the heat source was placed on the wall with the suction opening, two antagonistic behaviors were recorded: an improvement in heat transfer of about 31.6%, compared to the other positions, and a low Rayleigh number against 22% attenuation for high Ra values was noted.

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.

Constructal Design of Rectangular Fin Intruded Into Mixed Convective Lid-Driven Cavity Flows

2016 ◽  
Vol 138 (10) ◽  
Author(s):  
G. Lorenzini ◽  
B. S. Machado ◽  
L. A. Isoldi ◽  
E. D. dos Santos ◽  
L. A. O. Rocha
Keyword(s):  
Nusselt Number ◽  
Aspect Ratio ◽  
Convective Flow ◽  
Numerical Study ◽  
Reynolds Numbers ◽  
Lower Surface ◽  
Driven Cavity ◽  
Constructal Design ◽  
Mixed Convective Flow ◽  
Forced Convective Flow

The present work shows a numerical study of laminar, steady, and mixed convective flow inside lid-driven square cavity with intruded rectangular fin in its lower surface. The main purpose here is to maximize the heat transfer between the rectangular fin and the surrounding mixed convective flow inside a lid-driven cavity by means of constructal design. The problem is subject to two constraints, the lid-driven cavity and intruded fin areas. The ratio between the fin and cavity areas is kept fixed (ϕ = 0.05). The investigated geometry has one degree-of-freedom (DOF), the fin aspect ratio (H1/L1), which is varied in the range 0.1 ≤ H1/L1 ≤ 10. The aspect ratio of the cavity is maintained fixed (H/L = 1.0). The effect of the fin geometry over the Nusselt number is investigated for several Rayleigh (RaH = 103, 104, 105 and 106) and Reynolds numbers (ReH = 10, 102, 3.0 × 102, 5.0 × 102, 7.0 × 102 and 103). For all simulations, the Prantdl number is fixed (Pr = 0.71). The conservation equations of mass, momentum, and energy are numerically solved with the finite volume method. Results showed that fin geometry (H1/L1) has strong influence over the Nusselt number in the fin. It was also observed that the effect of H1/L1 over Nusselt number changes considerably for different Rayleigh numbers and for the lowest magnitudes of Reynolds numbers, for example, differences of nearly 770% between RaH = 106 and forced convective flow were observed for the lowest Reynolds number studied (ReH = 10).

Mixed Convection in a Horizontal Porous Duct With a Sudden Expansion and Local Heating From Below

1999 ◽  
Vol 121 (3) ◽  
pp. 653-661 ◽  
Author(s):  
Y. Yokoyama ◽  
F. A. Kulacki ◽  
R. L. Mahajan
Keyword(s):  
Heat Transfer ◽  
Convective Heat ◽  
Numerical Study ◽  
Local Heating ◽  
Lower Surface ◽  
Porous Matrix ◽  
Sudden Expansion ◽  
Nusselt Numbers ◽  
Matrix Heat ◽  
Heating From Below

Results are reported for an experimental and numerical study of forced and mixed convective heat transfer in a liquid-saturated horizontal porous duct. The cross section of the duct has a sudden expansion with a heated region on the lower surface downstream and adjacent to the expansion. Within the framework of Darcy’s formulation, the calculated and measured Nusselt numbers for 0.1 < Pe < 100 and 50 < Ra < 500 are in excellent agreement. Further, the calculated Nusselt numbers are very close to those for the bottom-heated flat duct. This finding has important implications for convective heat and mass transfer in geophysical systems and porous matrix heat exchangers. The calculations were also carried out for glass bead-packed beds saturated with water using non-Darcy’s formula. The streamlines in the forced convection indicate that, even with non-Darcy effects included, recirculation is not observed downstream of an expansion and the heat transfer rate is decreased but only marginally.

scholarly journals Asymmetrical Flow Driving in Two-Sided Lid-Driven Square Cavity with Antiparallel Wall Motion

2020 ◽  
Vol 330 ◽  
pp. 01009
Author(s):  
El Amin Azzouz ◽  
Samir Houat
Keyword(s):  
Wall Motion ◽  
Velocity Ratio ◽  
Two Dimensional ◽  
Square Cavity ◽  
Driven Cavity ◽  
Dimensional Flow ◽  
Fluid Properties ◽  
Two Dimensional Flow ◽  
Vertical Walls ◽  
Volume Method

The two-dimensional flow in a two-sided lid-driven cavity is often handled numerically for the same imposed wall velocities (symmetrical driving) either for parallel or antiparallel wall motion. However, in this study, we present a finite volume method (FVM) based on the second scheme of accuracy to numerically explore the steady two-dimensional flow in a two-sided lid-driven square cavity for antiparallel wall motion with different imposed wall velocities (asymmetrical driving). The top and the bottom walls of the cavity slide in opposite directions simultaneously at different velocities related to various imposed velocity ratios, λ = -2, -6, and -10, while the two remaining vertical walls are stationary. The results show that varying the velocity ratio and consequently the Reynolds ratios have a significant effect on the flow structures and fluid properties inside the cavity.

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