Experimental Heat Transfer Rates of Natural Convection of Molten Gallium Suppressed Under an External Magnetic Field in Either the X, Y, or Z Direction

1992 ◽  
Vol 114 (1) ◽  
pp. 107-114 ◽  
Author(s):  
K. Okada ◽  
H. Ozoe
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Natural Convection ◽  
External Magnetic Field ◽  
Magnetic Fields ◽  
Vertical Wall ◽  
Vertical Direction ◽  
Heated Wall ◽  
Heating Rates ◽  
Transfer Rates

The heat transfer rates of natural convection of molten gallium were measured under various strengths of heating rates and three coordinate directional magnetic fields. Molten gallium (Pr = 0.024) was filled in a cubic enclosure of 30 mm × 30 mm × 30 mm whose one vertical wall was uniformly heated and an opposing wall was isothermally cooled, with otherwise insulated walls. An external magnetic field was impressed either perpendicular and horizontal to the heated wall (x direction) or in parallel and horizontal to the heated wall (y direction) of the enclosure or in a vertical direction (z direction). For the modified Grashof number, based on the heat flux, less than 4.24 × 106 and the Hartmann number less than 461, the average Nusselt numbers were measured. These results proved that our previous three-dimensional numerical analyses for an isothermal hot wall boundary were in good qualitative agreement. A much higher suppression effect is given in the x- and z-directional magnetic fields than that in the y-directional one. The measured heat transfer rates were correlated as follows: NuB−1Nu0−1=1−[1+(aGr1/3/Ha)b]−1/nMagneticfield¯a¯b¯c¯x-directional0.573.191.76y-directional4.192.071.45z-directional0.522.721.44

Enhanced Heat Transfer Rate Measured for Natural Convection in Liquid Gallium in a Cubical Enclosure Under a Static Magnetic Field

1998 ◽  
Vol 120 (4) ◽  
pp. 1027-1032 ◽  
Author(s):  
Toshio Tagawa ◽  
Hiroyuki Ozoe
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Natural Convection ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Heated Wall ◽  
Electric Heater ◽  
Liquid Gallium ◽  
Cubical Enclosure ◽  
Moderate Magnetic Field

The heat transfer rate of natural convection in liquid gallium in a cubical enclosure was measured experimentally under an external magnetic field applied horizontally and parallel to the vertical heated wall and the opposing cooled wall and the opposing cooled wall of the enclosure. One vertical wall was heated with an electric heater and the opposing wall was cooled isothermally with running water. Experiments were conducted in the range of modified Rayleigh number from 1.85 × 106 to 4.76 × 106 and of Hartmann number from 0 to 573. The average Nusselt number was measured and found to increase when a moderate magnetic field was applied, but to decrease under a stronger magnetic field. This result means that the heat transfer rate has a maximum value at a certain moderate magnetic field, which supports our previous numerical analyses.

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 

MHD natural convection in a square porous cavity filled with a water-based magnetic fluid in the presence of geothermal viscosity

2018 ◽  
Vol 28 (9) ◽  
pp. 2111-2131 ◽  
Author(s):  
Mikhail A. Sheremet ◽  
Marina S. Astanina ◽  
Ioan Pop
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Natural Convection ◽  
Magnetic Fluid ◽  
Convective Flow ◽  
Uniform Magnetic Field ◽  
Vertical Wall ◽  
Content Type ◽  
Porous Cavity ◽  
Water Based

Purpose The purpose of this paper is a numerical analysis of natural convection in a square porous cavity filled with a water-based magnetic fluid of geothermal viscosity under the effect of inclined uniform magnetic field. Design/methodology/approach The domain of interest includes the square porous cavity filled with a water-based magnetic fluid (W40). Horizontal walls are supposed to be adiabatic, while right vertical wall is kept at constant low temperature and left vertical wall is kept at constant high temperature. An inclined uniform magnetic field affects the fluid flow and heat transfer inside the cavity. The viscosity of the working fluid is proportional to the linearly decreasing function of depth (vertical coordinate) and inversely proportional to the linear function of temperature. It is assumed in the analysis that the flow is laminar. The fluid is Newtonian and the Boussinesq approximation is valid. The governing equations have been discretized using the finite difference method with the uniform grid. Simulations have been carried out for different values of the Rayleigh number, Hartmann number, Darcy number, magnetic field inclination angle and viscosity variation parameters. Findings It has been revealed that an increase in the viscosity parameters leads to the heat transfer enhancement and convective flow intensification. At the same time, this intensification is more essential for high values of the Rayleigh number. Originality/value The originality of this work is to analyze MHD natural convection in a square porous cavity filled with a water-based magnetic fluid of geothermal viscosity. The results would benefit scientists and engineers to become familiar with the analysis of convective heat and mass transfer in nanofluids, and the way to predict the properties of nanofluid convective flow in advanced technical systems, in industrial sectors including transportation, power generation, chemical sectors and electronics.

Natural Convection of Mercury in a Magnetic Field parallel to the Gravity

1979 ◽  
Vol 101 (2) ◽  
pp. 227-232 ◽  
Author(s):  
M. Seki ◽  
H. Kawamura ◽  
K. Sanokawa
Keyword(s):  
Magnetic Field ◽  
Nusselt Number ◽  
Natural Convection ◽  
Vertical Wall ◽  
Heated Wall ◽  
Gravity Vector ◽  
Stagnation Region ◽  
Numerical Studies ◽  
Calculated Velocity ◽  
The Magnetic Field

Experimental and numerical studies were carried out on the natural convection of mercury in a rectangular container heated from a vertical wall. A magnetic field was applied parallel to the gravity vector and to the heated wall. Experimental results showed that the magnetic field decreased the Nusselt number considerably in the low region of the Grashof number. The effect of the parallel field was found to be less than that for a field normal to the gravity vector, but it is still not negligible. Numerical results on the Nusselt number were found to predict approximately the experimental ones. Calculated velocity profiles displayed noticeable changes due to the application of the magnetic field. A broad stagnation region was formed in the core of the container.

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