Ferrofluid Convection in a Lid-Driven Cavity

2018 ◽  
Vol 388 ◽  
pp. 407-419
Author(s):  
Fatih Selimefendigil ◽  
Ali Jawad Chamkha
Keyword(s):  
Heat Transfer ◽  
Magnetic Dipole ◽  
Richardson Number ◽  
Vertical Wall ◽  
Thermal Characteristics ◽  
Dipole Source ◽  
Dipole Strength ◽  
Square Enclosure ◽  
Lower Temperature ◽  
The Right

This study numerically investigates the mixed convection of ferrofluids in a partially heated lid driven square enclosure. The heater is located to the left vertical wall and the right vertical wall is kept at constant lower temperature while other walls of the cavity are assumed to be adiabatic. The governing equations are solved with Galerkin weighted residual finite element method. The influence of the Richardson number (between 0.01 and 100), heater location (between 0.25 H and 0.75H), strength of the magnetic dipole (between 0 and 4), and horizontal location of the magnetic dipole source (between-2H and-0.5H) on the fluid flow and heat transfer are numerically investigated. It is found that local and averaged heat transfer deteriorates with increasing values of Richardson number and magnetic dipole strength. The flow field and thermal characteristics are sensitive to the magnetic dipole source strength and its position and heater location.

Prandtl and Richardson Number Effects on Mixed Convection in a Vented Enclosure on Application to the Cooling of the Fins

2021 ◽  
Vol 406 ◽  
pp. 78-86
Author(s):  
Mohamed Chaour ◽  
Saadoun Boudebous
Keyword(s):  
Heat Transfer ◽  
Mixed Convection ◽  
Richardson Number ◽  
Transport Mechanism ◽  
Vertical Wall ◽  
Thomas Algorithm ◽  
Laminar Mixed Convection ◽  
Sweeping Method ◽  
The Finite Difference Method ◽  
The Right

In the present study, a numerical investigate the transport mechanism of laminar mixed convection in a vented enclosure. The walls of the cavity were kept adiabatic except the right vertical wall which was equipped with three fins dissipating the heat at a constant temperature. The equations of considered phenomenon were established and discretized by the finite difference method. The sweeping method line-by-line and the Thomas Algorithm (TDMA) were used for the resolution of the system of discretized equations. The results obtained showed that both the variations of the Prandtl and Richardson number have important effects on the flow structure and on the heat transfer.

Numerical Study of Natural Convection in a Ferrofluid-Filled Corrugated Cavity With Internal Heat Generation

2016 ◽  
Vol 138 (12) ◽  
Author(s):  
Fatih Selimefendigil ◽  
Hakan F. Öztop
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Rayleigh Number ◽  
Magnetic Dipole ◽  
Heat Generation ◽  
Internal Heat ◽  
Internal Heat Generation ◽  
Dipole Source ◽  
Internal Heating ◽  
Dipole Strength

In this paper, numerical simulations for the natural convection in a ferrofluid-filled corrugated cavity with internal heat generation under the influence of a magnetic dipole source were performed. The cavity is heated from below and cooled from above while vertical side walls are assumed to be adiabatic. A magnetic dipole source was located under the bottom heated wall. The governing equations were solved by Galerkin weighted residual finite-element formulation. The influence of external Rayleigh number (between 104 and 5 × 105), internal Rayleigh number (between 104 and 5 × 106), magnetic dipole strength (between 0 and 4), horizontal (between 0.2 and 0.8) and vertical (between −5 and −2) locations of the magnetic dipole source on fluid flow, and heat transfer are numerically investigated. It was observed that depending on heating mechanism (the external or internal heating), the presence of corrugation of the bottom wall either enhances or deteriorates the absolute value of the averaged heat transfer. The strength and locations of the magnetic dipole source affect the distribution of the flow and thermal patterns within the cavity for both flat and corrugated wall cavity. The net effect of the complicated interaction of the internal heating, external heating, and ferroconvection of magnetic source results in heat transfer enhancement with increasing values of magnetic dipole strength. Wall corrugation causes more enhancement of averaged heat transfer and this is more pronounced for low values of vertical location of magnetic source.

scholarly journals Natural convection in a Square Enclosure with Partially Active Vertical Wall

2020 ◽  
Vol 330 ◽  
pp. 01004
Author(s):  
Abdennacer Belazizia ◽  
Smail Benissaad ◽  
Said Abboudi
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Rayleigh Number ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Vertical Wall ◽  
Left Wall ◽  
Convection And Heat Transfer ◽  
Square Enclosure ◽  
Active Location

Steady, laminar, natural convection flow in a square enclosure with partially active vertical wall is considered. The enclosure is filled with air and subjected to horizontal temperature gradient. Finite volume method is used to solve the dimensionless governing equations. The physical problem depends on three parameters: Rayleigh number (Ra =103-106), Prandtl number (Pr=0.71), and the aspect ratio of the enclosure (A=1). The active location takes two positions in the left wall: top (T) and middle (M). The main focus of the study is on examining the effect of Rayleigh number on fluid flow and heat transfer rate. The results including the streamlines, isotherm patterns, flow velocity and the average Nusselt number for different values of Ra. The obtained results show that the increase of Ra leads to enhance heat transfer rate. The fluid particles move with greater velocity for higher thermal Rayleigh number. Also by moving the active location from the top to the middle on the left vertical wall, convection and heat transfer rate are more important in case (M). Furthermore for high Rayleigh number (Ra=106), Convection mechanism in (T) case is principally in the top of the enclosure, whereas in the remaining case it covers the entire enclosure.

Upward and downward conjugate mixed convection heat transfer in a partially porous cavity

2016 ◽  
Vol 26 (1) ◽  
pp. 159-188 ◽  
Author(s):  
Abderrahim Bourouis ◽  
Abdeslam Omara ◽  
Said Abboudi
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Mixed Convection ◽  
Transfer Rate ◽  
Vertical Wall ◽  
Thermal Conductivity Ratio ◽  
Conductivity Ratio ◽  
Content Type ◽  
Moving Wall ◽  
The Right

Purpose – The purpose of this paper is to provide a numerical study of conjugate heat transfer by mixed convection and conduction in a lid-driven enclosure with thick vertical porous layer. The effect of the relevant parameters: Richardson number (Ri=0.1, 1, 10) and thermal conductivity ratio (Rk=0.1, 1, 10, 100) are investigated. Design/methodology/approach – The studied system is a two dimensional lid-driven enclosure with thick vertical porous layer. The left vertical wall of the enclosure is allowed to move in its own plane at a constant velocity. The enclosure is heated from the right vertical wall isothermally. The left and the right vertical walls are isothermal but temperature of the outside of the right vertical wall is higher than that of the left vertical wall. Horizontal walls are insulated. The governing equations are solved by finite volume method and the SIMPLE algorithm. Findings – From the finding results, it is observed that: for the two studied cases, heat transfer rate along the hot wall is a decreasing function of thermal conductivity ratio irrespective of Richardson numbers contrary to the heat transfer rate along the fluid-porous layer interface which is an increasing function of thermal conductivity ratio. At forced convection dominant regime, the difference between heat transfer rate for upward and downward moving wall is insensitive to the thermal conductivity ratio. For downward moving wall, average Nusselt number is higher than that of upward moving wall. Practical implications – Some applications: building applications, furnace design, nuclear reactors, air solar collectors. Originality/value – From the bibliographic work and the authors’ knowledge, the conjugate mixed convection in lid-driven partially porous enclosures has not yet been investigated which motivates the present work that represent a continuation of the preceding investigations.

scholarly journals Optimal Conditions of Natural and Mixed Convection in a Vented Rectangular Cavity with a Sinusoidal Heated Wall Inside with a Heated Solid Block

2021 ◽  
Vol 15 ◽  
Keyword(s):  
Heat Transfer ◽  
Amplitude Ratio ◽  
Vertical Wall ◽  
Rectangular Cavity ◽  
Heated Wall ◽  
Fluid Temperature ◽  
Thermal Coefficient ◽  
Phase Deviation ◽  
The Right ◽  
Solid Block

The present investigation deals with the natural, mixed and forced convection in a vented rectangular cavity having a sinusoidal heated vertical wall with a conducting solid block placed at one of the nine positions. The objective is to analyze numerically using finite element method the effects of the following parameters: inlet, outlet positions, solid square positions, thermal coefficient λ, amplitude ratio ɛ, phase deviation ϕ and the solid square size on the thermo-convective flows. The Richardson number is varied from 0 to 40, the Reynolds and Prandtl numbers are fixed respectively at 100 and 0.71. To quantify the heat transfer of the solid block and to get closer to real conditions, we have developed a modification based on the evaluation of the Nusselt number using the average temperature in the cavity, unlike previous works which used the input temperature. As results, the sinusoidal temperature at the right wall gives higher heat transfer enhancement. The variation of the phase deviation and amplitude ratio have a slightly effect on the average fluid temperature and average Nusselt at the right wall and at the square solid.

scholarly journals Design of Cross Flow Heat Exchanger Using Performance Charts

2018 ◽  
Vol 3 (2) ◽  
pp. 1
Author(s):  
Mohammed Al Arfaj ◽  
Nasser Al Mulhim ◽  
Abdullah Al Mulhim ◽  
Ahmed Al Naim
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Surface Area ◽  
Material Flow ◽  
Cross Flow ◽  
Thermal Characteristics ◽  
Preliminary Design ◽  
Dimensionless Parameters ◽  
Flow Heat ◽  
The Right

The manuscript reviews the various steps involved in the design of a cross flow heat exchanger. Performance charts describing the thermal performance of the heat exchanger in terms of dimensionless parameters are used to develop the preliminary design of the heat exchanger. The preliminary design involves choosing the required number of heat exchanger passes, the required number of transfer units (NTU) and the capacity rate ratio for a given heat transfer application. These dimensionless parameters account for material, flow and thermal characteristics of the heat exchanger. In addition, NTU accounts for heat exchanger size, flow configuration and the type of heat exchanger. Since the preliminary design accounts for all the major characteristics of the heat exchanger, this approach is beneficial in optimizing the heat exchanger during the design phase. Performance charts indicate that indefinitely increasing the surface area (or NTU) does not increase the rate of heat transfer. There exists a threshold limit beyond which increasing the surface area adds no benefit to the heat exchanger. Instead, it just adds weight, material and cost of the heat exchanger. It must be noted that an undersized heat exchanger for a given application may not deliver the required heat transfer and while an oversized heat exchanger will increase the capital cost. Hence, it is very important to choose the right parameters during design of a heat exchanger. From the preliminary design, the detailed design for the heat exchanger can be readily extrapolated. The benefits of using performance charts in the design of a cross flow heat exchanger are described in the manuscript.

Numerical Study of Magnetic Field Effects on Buoyancy Driven Convection in a Non-Isothermally Heated Square Enclosure

2011 ◽  
Vol 312-315 ◽  
pp. 536-541
Author(s):  
Ghanbar Ali Sheikhzadeh ◽  
Mohsen Pirmohammadi ◽  
A. Fattahi ◽  
M.A. Mehrabian
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Hartmann Number ◽  
Numerical Study ◽  
Convection Heat Transfer ◽  
Magnetic Field Effects ◽  
Left Wall ◽  
Square Enclosure ◽  
The Right ◽  
Sinusoidal Function

Numerical simulation of natural convection heat transfer in the presence of a magnetic field is analyzed in a non-isothermally heated square enclosure. The left wall is heated and cooled with a sinusoidal heat source and the right wall is cooled isothermally. The horizontal walls of the enclosure are adiabatic. The effects of Rayleigh number (Ra = 104, 105 and 106), Hartmann number (Ha = 0, 25, 50 and 100) and amplitude of sinusoidal function (n = 0.25, 0.5 and 1) on temperature and flow fields are analyzed. It is observed that the rate of heat transfer is decreased with increasing the Hartmann number; it is also decreased when decreasing the amplitude of sinusoidal function.

scholarly journals Heat-Mass Transfer of Nanofluid in Lid-Driven Enclosure under three Convective Modes

2019 ◽  
Vol 38 ◽  
pp. 73-83
Author(s):  
MS Rahman ◽  
R Nasrin ◽  
MI Hoque
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Temperature Difference ◽  
Richardson Number ◽  
Numerical Study ◽  
Mass Transfer Rate ◽  
Square Enclosure ◽  
Coupled Equations ◽  
Wide Range

Heat is a form of energy which transfers between bodies which are kept under thermal interactions. When a temperature difference occurs between two bodies or a body with its surroundings, heat transfer occurs. Heat transfer occurs in three modes. Three modes of heat transfer are conduction, convection and radiation. Convection is a very important phenomenon in heat transfer applications and it occurs due to two different gradients, such as, temperature and concentration. This paper reports a numerical study on forced-mixed-natural convections within a lid-driven square enclosure, filled with a mixture of water and 2% concentrated Cu nanoparticles. It is assumed that the temperature difference driving the convection comes from the side moving walls, when both horizontal walls are kept insulated. In order to solve general coupled equations, a code based on the Galerkin's finite element method is used. To make clear the effect of using nanofluid on heat and mass transfers inside the enclosure, a wide range of the Richardson number, taken from 0.1 to 10 is studied. A fair degree of precision can be found between the present and previously published works. The phenomenon is analyzed through streamlines, isotherm and iso-concentration plots, with special attention to the Nusselt number and Sherwood number. The larger heat and mass transfer rates can be achieved with nanofluid than the base fluid for all conditions at Richardson number, Ri = 0.1 to 10. It has been found that the heat and mass transfer rate increase approximately 6% for water with the increase of Ri = 0.1 to 10, whereas these increase about 34% for nanofluid. GANIT J. Bangladesh Math. Soc.Vol. 38 (2018) 73-83

Natural convection analysis for both protruding and flush-mounted heaters located in triangular enclosure

2008 ◽  
Vol 222 (7) ◽  
pp. 1203-1214 ◽  
Author(s):  
A Koca ◽  
H F Oztop ◽  
Y Varol
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Vertical Wall ◽  
Convection Heat Transfer ◽  
Dimensionless Length ◽  
Dimensionless Distance ◽  
First Case ◽  
Triangular Enclosure ◽  
The Right ◽  
Single Heater

A numerical was performed analysis on laminar natural convection heat transfer and fluid flow in both protruding heaters (PHs) and flush-mounted heaters (FMHs) located in a triangular enclosure using finite-difference technique. The heaters were isothermal and the temperature of the inclined wall was lower than that of the heaters while the remaining walls of the triangular enclosure were adiabatic. Results are presented according to the location of the heaters in two cases. In the first case, the PH was located near the vertical wall and the FMH near the right corner. In the second case, the PH was located near the right corner of the enclosure, whereas the FMH was located close to the vertical wall. The governing parameters on natural convection were Rayleigh number (104≤Ra≤106), dimensionless length of the PH ( W1), dimensionless length of the FMH ( W2), dimensionless height of the PH (Hp), dimensionless distance between the heater and the vertical wall ( S1), dimensionless distance between the PH and the FMH ( S2), and aspect ratio of the triangular enclosure (0.25 ≤AR≤ 1.0). It was found that better heat transfer occured when the PH was located near the right corner of the triangular enclosure, while the other heater was mounted near the left vertical wall. Heaters behaved as a single heater when they were close to each other.

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