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 Effects of Non-Homogeneous Nanofluid Model on Natural Convection in a Square Cavity in the Presence of Conducting Solid Block and Corner Heater

Energies ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 2507 ◽  
Author(s):  
Ammar Alsabery ◽  
Tahar Tayebi ◽  
Ali Chamkha ◽  
Ishak Hashim
Keyword(s):  
Thermal Conductivity ◽  
Natural Convection ◽  
Volume Fraction ◽  
Vertical Wall ◽  
Heated Wall ◽  
Square Cavity ◽  
Two Phase ◽  
Corner Heater ◽  
The Right ◽  
Solid Block

This study investigates numerically the effect of the two-phase nanofluid model due to natural convection within a square cavity along with the existence of a conducting solid block, and a corner heater using the finite difference method (FDM). The top horizontal wall is retained at a cold temperature that is fixed as constant, while the isothermal heater is positioned at the bottom left corner within the square cavity. The remaining fractions of the right vertical wall and the heated wall are set to be adiabatic. The water-based nanofluid, together with Al 2 O 3 nanoparticles, have been evaluated by determining the following parameters: the volume fraction of nanoparticles, thickness of solid block, Rayleigh number, and the solid block thermal conductivity. As a result, the comparative evaluation with outputs reported in publications and prior experimental works has pointed out exceptional agreement with the findings retrieved in this study. The experimental outcomes are graphically illustrated in terms of the average and local Nusselt numbers, isotherms, distribution of nanoparticles, and the streamlines. The findings indicate that an elevation of the thermal conductivity in blocks with a similar size successfully increases the transfer rate of heat, wherein the dominance of conduction has been observed.

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.

scholarly journals Heat transfer during pulsating liquid jet impingement onto a vertical wall

2020 ◽  
Author(s):  
J. Wassenberg ◽  
P. Stephan ◽  
T. Gambaryan-Roisman
Keyword(s):  
Heat Transfer ◽  
Vertical Wall ◽  
Jet Impingement ◽  
High Heat ◽  
Heated Wall ◽  
Liquid Jet ◽  
Pulsation Frequency ◽  
Cooling Efficiency ◽  
Heat Transfer Efficiency ◽  
Impingement Point

Abstract Liquid jet impingement is used for cooling and cleaning in various industrial branches. The advantages of jet impingement include high heat and mass transport rates in the vicinity of the impingement point. Pulsating liquid jets impinging on horizontal substrates with a pulsation frequency around 100 Hz have been shown to increase the cooling efficiency in comparison to jets with continuous mass flow rates. The influence of jet pulsation on cooling efficiency for impingement of horizontal jets onto vertical walls has not yet been investigated. In the case of a vertical heated wall, gravity contributes to the liquid flow pattern. In particular, if the time span between two pulses is sufficiently long, the liquid drainage from the region above the impingement point can contribute to heat transport without increasing the average flow rate of the cooling medium. In this work, the influence of pulsations on heat transfer during impingement of a horizontal liquid jet onto a vertical wall is investigated experimentally for the pulsation frequency range 1–5 Hz. The results regarding increase of heat transfer efficiency are related to flow patterns developing by impingement of successive pulses, as well as to the liquid splattering.

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.

Aspect Ratio Effect on Natural Convection Flow in a Cavity Submitted to a Periodical Temperature Boundary

2006 ◽  
Vol 129 (8) ◽  
pp. 1060-1068 ◽  
Author(s):  
Nader Ben Cheikh ◽  
Brahim Ben Beya ◽  
Taieb Lili
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Aspect Ratio ◽  
Vertical Wall ◽  
Heated Wall ◽  
Convection Flow ◽  
Natural Convection Flow ◽  
Temperature Boundary ◽  
Shallow Cavities ◽  
Periodic Temperature

The effect of aspect ratio on natural convection flow in a cavity submitted to periodic temperature boundary, is investigated numerically. The temperature of the heated wall is either maintained constant or varied sinusoidally with time while the temperature of the opposite vertical wall is maintained constant. The results are given for a range of varied parameters as Rayleigh number (5×103⩽Ra⩽106), cavity aspect ratio (1∕6⩽A⩽8), and period of the sinusoidally heated wall (1⩽τ⩽1600). The amplitude of oscillation (a=0.8) and the Prandtl number (Pr=0.71) were kept constant. The results obtained in the steady state regime show that the heat transfer averaged over the cold wall is maximum when the aspect ratio is in the range 1⩽A⩽2. In the case of a periodic temperature boundary, it is shown that the deviation between the mean heat transfer and the heat transfer of the constant heated case is larger for shallow cavities.

scholarly journals Natural convection flow in a square cavity with internal heat generation and a flush mounted heater on a side wall

2011 ◽  
Vol 7 (2) ◽  
pp. 37-50 ◽  
Author(s):  
Md. Mustafizur Rahman ◽  
M. Arif Hasan Mamun ◽  
M. Masum Billah ◽  
Saidur Rahman
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Natural Convection ◽  
Heat Generation ◽  
Vertical Wall ◽  
Heated Wall ◽  
Convection Flow ◽  
Square Cavity ◽  
Natural Convection Flow ◽  
Heater Length

In this study natural convection flow in a square cavity with heat generating fluid and a finite size heater on the vertical wall have been investigated numerically. To change the heat transfer in the cavity, a heater is placed at different locations on the right vertical wall of the cavity, while the left wall is considered to be cold. In addition, the top and bottom horizontal walls are considered to be adiabatic and the cavity is assumed to be filled with a Bousinessq fluid having a Prandtl number of 0.72. The governing mass, momentum and energy equations along with boundary conditions are expressed in a normalized primitive variables formulation. Finite Element Method is used in solution of the normalized governing equations. The parameters leading the problem are the Rayleigh number, location of the heater, length of the heater and heat generation. To observe the effects of the mentioned parameters on natural convection in the cavity, we considered various values of heater locations, heater length and heat generation parameter for different values of Ra varying in the range 102 to 105. Results are presented in terms of streamlines, isotherms, average Nusselt number at the hot wall and average fluid temperature in the cavity for the mentioned parameters. The results showed that the flow and thermal fields through streamlines and isotherms as well as the rate of heat transfer from the heated wall in terms of Nusselt number are strongly dependent on the length and locations of the heater as well as heat generating parameter.DOI: 10.3329/jname.v7i2.3292 

scholarly journals Effect of Inlet and Outlet Locations on Transverse Mixed Convection Inside a Vented Enclosure

1970 ◽  
Vol 36 ◽  
pp. 27-37 ◽  
Author(s):  
Sumon Saha ◽  
Md. Tofiqul Islam ◽  
Mohammad Ali ◽  
Md. Arif Hassan Mamun ◽  
M Quamrul Islam
Keyword(s):  
Heat Transfer ◽  
Finite Element Method ◽  
Reynolds Number ◽  
Finite Element ◽  
Mixed Convection ◽  
Vertical Wall ◽  
Flow Fields ◽  
Temperature Fields ◽  
Heated Wall ◽  
Element Method

Transverse mixed convection is studied numerically in a vented enclosure with constant heat flux from uniformly heated bottom wall. An external airflow enters the enclosure through an opening in one vertical wall and exits from another opening in the opposite wall. The two-dimensional mathematical model includes the system of four partial differential equations of continuity, linear momentum and energy, solved by the finite element method. Flow fields are investigated by numerical simulations for air flowing with a Reynolds number in the range 50 ≤ Re ≤ 1000, for Richardson numbers: 0 ≤ Ri ≤ 10. Four different locations of inlet and outlets are introduced to analyze the effect of heat transfer in terms of velocity and temperature fields within the enclosure. The computational results show that the location of inlet and outlets alters significantly the temperature distribution in the flow fields and the heat transfer across the heated wall of the cavities. Empirical correlation is developed for relations using Nusselt number, Reynolds number and Richardson number, based on the enclosure height.   Keywords: Mixed convection, finite element method, vented enclosure, Richardson number.Journal of Mechanical Engineering Vol.36 Dec. 2006 pp.27-37DOI = 10.3329/jme.v36i0.808

scholarly journals Heat transfer comparison between a vertical rectangular cavity and an isosceles right-angled triangular cavity of equal cross-sectional area

2011 ◽  
Vol 15 (suppl. 2) ◽  
pp. 357-365 ◽  
Author(s):  
Antonio Campo ◽  
Jane Chang ◽  
El Ridouane
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Heat Transfer Performance ◽  
Vertical Wall ◽  
Rectangular Cavity ◽  
Temperature Fields ◽  
Graphical Form ◽  
Transfer Performance ◽  
Square Cavity ◽  
The Common

This paper addresses the heat transfer performance of natural convection flows in three different, (but related) cavities in the form of: a square, isosceles right-angled triangle, and vertical rectangle with aspect ratio 2:1. The isosceles right-angled triangular cavity is derived from a square cavity when cut in half diagonally, whereas the vertical rectangular cavity is derived from a square cavity when cut in half vertically. In the three cavities, the left vertical wall is the common wall heated. The buoyant air flow is characterized by height-based Rayleigh numbers ranging from a conduction-dominant to up to 106 for the laminar natural convection regime. Employing the finite volume method, the velocity and temperature fields as well as the mean convective coefficients evaluated at the common heated vertical wall are numerically determined for the isosceles right-angled triangular cavity. For this cavity, flow streamlines and temperature contours are presented in graphical form and some numerical results are validated against published experimental measurements. A one-to-one comparison for the heat transfer performance of the three interconnected cavities is reported in tabulated form.

scholarly journals Finite Element Analysis of Mixed Convection in a Rectangular Cavity with a Heat-Conducting Horizontal Circular Cylinder

2009 ◽  
Vol 14 (2) ◽  
pp. 217-247 ◽  
Author(s):  
Md. M. Rahman ◽  
M. A. Alim ◽  
M. A. H. Mamun
Keyword(s):  
Heat Transfer ◽  
Finite Element ◽  
Heat Source ◽  
Mixed Convection ◽  
Rectangular Cavity ◽  
Heated Wall ◽  
Physical Parameters ◽  
Element Formulation ◽  
Heat Conducting ◽  
Coupled Equations

. Combined free and forced convection in a two dimensional rectangular cavity with a uniform heat source applied on the right vertical wall is studied numerically. A circular heat conducting horizontal cylinder is placed somewhere within the cavity. The present study simulates a practical system, such as a conductive material in an inert atmosphere inside a furnace with a constant flow of gas from outside. Importance is placed on the influences of the configurations and physical properties of the cavity. The development mathematical model is governed by the coupled equations of continuity, momentum and energy and is solved by employing Galerkin weighted residual finite element method. In this paper, a finite element formulation for steadystate incompressible conjugate mixed convection and conduction flow is developed. The computations are carried out for wide ranges of the governing parameters, Reynolds number (Re), Richardson number (Ri), Prandtl number (Pr) and some physical parameters. The results indicate that both the heat transfer rate from the heated wall and the dimensionless temperature in the cavity strongly depend on the governing parameters and configurations of the system studied, such as size, location, thermal conductivity of the cylinder and the location of the inflow and outflow opening. Detailed results of the interaction between forced airstreams and the buoyancy-driven flow by the heat source are demonstrated by the distributions of streamlines, isotherms and heat transfer coefficient.

Computational fluid dynamics and experimental analysis of the heat transfer in a room with a roof solar chimney

2021 ◽  
pp. 1-26
Author(s):  
Adolfo Vazquez ◽  
Jose MA Navarro ◽  
Jesus Hinojosa ◽  
Dr. Jesús Xamán
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamics ◽  
Heat Flux ◽  
Computational Fluid Dynamics ◽  
Experimental Analysis ◽  
Vertical Wall ◽  
Temperature Fields ◽  
Heated Wall ◽  
Transfer Coefficients ◽  
Solar Chimney

Abstract This study reports a numerical-experimental analysis of heat transfer and airflow in a scaled room with a heated wall coupled with a double-channel vertical roof solar chimney. For the experimental part, a parametric study was performed in the thermal system, considering different values of heat flux supplied to a vertical wall of the scaled room (75 and 150 W/m2) and the absorber surface of the solar chimney (151 and 667 W/m2). Experimental temperature profiles were obtained at six different depths and heights, and experimental heat transfer coefficients were computed for both heated surfaces. The renormalization group k-e turbulence model was evaluated against experimental data using computational fluid dynamics software. With the validated model, the effect of the heated wall and solar chimney on temperature fields, flow patterns, and heat transfer convective coefficients are presented and discussed. The cases with heat flux on the heated wall of the scaled room produce the biggest air changes per hour (ACH), being 30.1, 31.2, and 23.4 ACH for cases 1 to 3 respectively, while cases with no heated wall produce fewer ACH (11.72 and 12.28 for case 4 and 5). The comparison between cases with and without heat flux on one vertical wall but the same solar chimney heat flux shows that the ACH increases between 154 % and 156% respectively.

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