F222 Natural Convection in a Horizontal Cylindrical Annulus : Heat Transfer and Flow Characteristics of 3-D Spiral Flow

2005 ◽  
Vol 2005 (0) ◽  
pp. 439-440
Author(s):  
Hiroyuki NAKAGAWA ◽  
Mamoru SENDA ◽  
Kyoji INAOKA
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Flow Characteristics ◽  
Spiral Flow ◽  
Cylindrical Annulus

Natural Convection Heat Transfer of Water Within a Horizontal Cylindrical Annulus With Density Inversion Effects

1983 ◽  
Vol 105 (1) ◽  
pp. 117-123 ◽  
Author(s):  
P. Vasseur ◽  
L. Robillard ◽  
B. Chandra Shekar
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Numerical Solutions ◽  
Cold Water ◽  
Freezing Point ◽  
Convection Heat Transfer ◽  
Natural Convection Heat Transfer ◽  
Convection Heat ◽  
Density Inversion ◽  
Cylindrical Annulus

The effect of density inversion on steady natural convection heat transfer of cold water, between two horizontal concentric cylinders of gap width, L, is studied numerically. Water near its freezing point is characterized by a density maximum at 4°C. Numerical solutions are obtained for cylinders with nonlinear Rayleigh numbers RA ranging from 2 × 103 to 7.6 × 104, a radius ratio 1.75 ≤ ra ≤ 2.6 and an inversion parameter γ, relating the temperature for maximum density with the cavity wall temperatures, between −2 and 2. The results obtained are presented graphically in the form of streamline and isotherm contour plots. The heat transfer characteristics, velocity profiles, and local and overall Nusselt numbers are studied. The results of the present study were found qualitatively valid when compared with an experimental investigation carried out in the past.

Natural Convection Heat Transfer of Cold Water Within an Eccentric Horizontal Cylindrical Annulus

1988 ◽  
Vol 110 (4a) ◽  
pp. 894-900 ◽  
Author(s):  
C. J. Ho ◽  
Y. H. Lin
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Cold Water ◽  
Convection Heat Transfer ◽  
Orientation Angle ◽  
Natural Convection Heat Transfer ◽  
Convection Heat ◽  
Density Inversion ◽  
Cylindrical Annulus ◽  
Isothermal Cylinders

Natural convection heat transfer of cold water, encompassing a density inversion, within an eccentric horizontal annulus made of two isothermal cylinders, is numerically studied via a finite difference method. Numerical results have been obtained for an annular radius ratio 2.6 with Rayleigh number ranging from 103 to 106, the inversion parameter being 0.0 to 1.0, the eccentricity varying from 0 to 0.8, and the orientation angle of the inner cylinder between 0 and π. Results indicate that the flow patterns and heat transfer characteristics are strongly influenced by the combined effect induced by the density inversion of water and the position of the inner cylinder of the annulus. For the cases considered in the present study, a minimum in heat transfer arises with the inversion parameter between 0.4 and 0.5 depending primarily on the position of the inner cylinder.

Magnetohydrodynamic Natural Convection Heat Transfer of Hybrid Nanofluid in a Square Enclosure in the Presence of a Wavy Circular Conductive Cylinder

2019 ◽  
Vol 12 (3) ◽  
Author(s):  
Tahar Tayebi ◽  
Ali J. Chamkha
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Convection Heat Transfer ◽  
Flow Characteristics ◽  
Hybrid Nanofluid ◽  
Square Enclosure ◽  
Convection Problem ◽  
Laminar Natural Convection ◽  
Natural Convection Problem ◽  
Volume Method

Abstract In this paper, steady natural convective heat transfer and flow characteristics of Al2O3-Cu/water hybrid nanofluid filled square enclosure in the presence of magnetic field has been investigated numerically. The enclosure is equipped with a wavy circular conductive cylinder. The natural convection in the cavity is induced by a temperature difference between the vertical left hot wall and the other right cold wall. The steady 2-D equations of laminar natural convection problem for Newtonian and incompressible mixture are discretized using the finite volume method. The effective thermal conductivity and viscosity of the hybrid nanofluid are calculated using Corcione correlations taking into consideration the Brownian motion of the nanoparticles. A numerical parametric investigation is carried out for different values of the nanoparticles volumic concentration, Hartmann number, Rayleigh number, and the ratio of fluid to solid thermal conductivities. According to the results, the corrugated conductive block plays an important role in controlling the convective flow characteristic and the heat transfer rate within the system.

Optimal Cooling Channel Layout in a Hot Enclosure Subject to Natural Convection

2019 ◽  
Vol 141 (11) ◽  
Author(s):  
Sam Yang ◽  
Juan C. Ordonez
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Ant Colony Optimization ◽  
Flow Characteristics ◽  
Ant Colony ◽  
Bejan Number ◽  
Optimization Approach ◽  
Cooling Channel ◽  
Ant Colony Optimization Algorithm ◽  
Cooling Channels

Abstract We analyzed the optimal cooling channel layouts emerged from minimizing the total entropy generation ST and mean enclosure temperature T¯ in a hot enclosure subject to natural convection. The conservation of mass, momentum, and energy were solved numerically in two-dimensional (2D) space using the finite element method, and an ant colony optimization algorithm was employed to determine the optimal layouts with respect to the number of cooling channels (N) and Rayleigh number (Ra). The total allocatable cooling channel area was fixed in all cases and thus each channel area decreased with increasing N. Subsequently, we examined the heat transfer and flow characteristics based on temperature field, streamlines, and local Bejan number of each optimum and deduced the following: (1) All optimal channel layouts were symmetric about the vertical enclosure centerline; however, the optima resulting in ST,min and T¯min did not always coincide and depended heavily on the flow configuration dictated by N and Ra; (2) the competing nature between heat transfer and its irreversibility was pronounced at low Ra and N when convection and fluid friction were ineffective; and (3) the first and second law performance improved as N increased in most cases. Furthermore, results verified the global convergence and robustness of the ant colony optimization approach in solving a layout optimization problem with pure natural convection.

Heat Transfer and Fluid Flow Characteristic of One Side Heated Vertical Rectangular Channel That Inserted Thin Metallic Wire

2020 ◽  
Author(s):  
Gota Suga ◽  
Tetsuaki Takeda
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
High Temperature ◽  
Natural Convection ◽  
Cooling System ◽  
Copper Wire ◽  
Rectangular Channel ◽  
Flow Characteristics ◽  
Experimental Apparatus ◽  
High Temperature Reactor

Abstract A Very High Temperature Reactor (VHTR) is one of the next generation nuclear systems. From a view point of safety characteristics, a passive cooling system should be designed as the best way of a reactor vessel cooling system (VCS) in the VHTR. Therefore, the gas cooling system with natural circulation is considered as a candidate for the VCS of the VHTR. Japan Atomic Energy Agency (JAEA) is advancing the technology development of the VHTR and is now pursuing design and development of commercial systems such as the 300MWe gas turbine high temperature reactor GTHTR300C (Gas Turbine High Temperature Reactor 300 for Cogeneration). In the VCS of the GTHTR300C, many rectangular flow channels are formed around the reactor pressure vessel (RPV), and a cooling panel utilizing natural convection of air has been proposed. In order to apply the proposed panel to the VCS of the GTHTR300C, it is necessary to clarify the heat transfer and flow characteristics of the proposed channel in the cooling panel. Thus, we carried out an experiment to investigate heat transfer and fluid flow characteristics by natural convection in a vertical rectangular channel heated on one side. Experiments were also carried out to investigate the heat transfer and fluid flow characteristics by natural convection when a porous material with high porosity is inserted into the channel. An experimental apparatus is a vertical rectangular flow channel with a square cross section in which one surface is heated by a rubber heater. Dimensions of the experimental apparatus is 600 mm in height and 50 mm on one side of the square cross section. Air was used as a working fluid and fine copper wire (diameter: 0.5 mm) was used as a porous material. The temperature of the wall surface and gas in the channel were measured by K type thermocouples. We measured the outlet flow rate by hot-wire anemometer which is an omnidirectional spherical probe of diameter 2.5mm. The experiment has been carried out under the condition that a copper wire with a scourer model and a cubic lattice model were inserting into the channel.

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