Natural Convection in a Partially Heat Generating Rod Bundle Inside an Enclosure

2010 ◽  
Vol 132 (10) ◽  
Author(s):  
D. Jaya Krishna ◽  
M. R. Thansekhar ◽  
S. P. Venkateshan ◽  
Tanmay Basak ◽  
Sarit K. Das
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Experimental Study ◽  
Porous Media ◽  
Natural Convection ◽  
Temperature Distribution ◽  
Diameter Ratio ◽  
Rod Bundles ◽  
Rod Bundle ◽  
Power Inputs

Buoyancy induced flows in a partially heat generating rod bundle enclosed inside a tall cavity are investigated. First, a detailed experimental study is carried out, and the thermal hydraulics is analyzed at different power inputs and boundary cooling rates of the enclosure. Later, a generalized non-Darcy simulation is developed using a heat generating orthotropic porous media approach and is compared with the experimental results. The results of a numerical simulation for natural convection in enclosed partially heat generating rod bundles satisfactorily predict the temperature distribution within the rod bundle. Finally, a parametric study is carried out by varying the porosity (pitch to diameter ratio of the rod bundle) of the considered enclosure for the understanding of flow physics and heat transfer in such applications.

An Analysis of Heat Transfer to Axial Dispersed Flow between Rod Bundles under Reactor Emergency Cooling Conditions

1980 ◽  
Vol 102 (3) ◽  
pp. 508-512 ◽  
Author(s):  
S. Wong ◽  
L. E. Hochreiter
Keyword(s):  
Heat Transfer ◽  
Diameter Ratio ◽  
Circular Pipe ◽  
Rod Bundles ◽  
Dispersed Flow ◽  
Rod Bundle ◽  
Cooling Conditions ◽  
Flow Heat ◽  
Square Array ◽  
The Heat Transfer Coefficient

Analysis is carried out for dispersed flow heat transfer under reactor emergency cooling conditions. The present formulation explicitly reveals an extra dependence of the heat transfer coefficient and Nusselt number on the mean vapor temperature for droplet dispersed flow which is not found in single phase flow heat transfer. The heat transfer results obtained from three different geometries—an infinite square array of cylindrical rods, an annulus and a circular pipe—are compared; all have the same hydraulic diameter. It is found that, within the framework of the present analysis, results for the annulus and the rod bundles agree well when the pitch-to-diameter ratio is 1.5 or greater. The circular pipe is in general a poor approximation for rod bundle geometries except at a pitch-to-diameter ratio of about 1.3 which is typical of present day light water reactor fuel assemblies.

Experimental Study of Internal Forced Convection of Ferrofluid Flow in Porous Media

2014 ◽  
Vol 348 ◽  
pp. 139-146 ◽  
Author(s):  
Ashkan Sehat ◽  
Hani Sadrhosseini ◽  
M. Behshad Shafii
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Experimental Study ◽  
Porous Media ◽  
Temperature Distribution ◽  
Pressure Drop ◽  
Forced Convection ◽  
Volume Fraction ◽  
Flow In Porous Media ◽  
Tetra Methyl Ammonium Hydroxide

This work presents an experimental study of the effect of a magnetic field on laminar forced convection of a ferrofluid flowing in a tube filled with permeable material. The walls of the tube are subjected to a uniform heat flux and the permeable bed consists of uniform spheres of 3-mm diameter. The ferrofluid synthesis is based on reacting iron (II) and iron (III) in an aqueous ammonia solution to form magnetite, Fe3O4. The magnetite is mixed with aqueous tetra methyl ammonium hydroxide, (CH3)4NOH, solution. The dependency of the pressure drop on the volume fraction, and comparison of the pressure drop and the temperature distribution of the tube wall is studied. Also comparison of the wall temperature distribution, convection heat transfer coefficient and the Nusselt numbers of ferrofluids with different volume fractions is investigated for various Reynolds numbers (147 < Re < 205 ). It is observed that the heat transfer is enhanced by using a porous media, increasing the volume fraction had a similar effect. The pressure coefficient decreases for higher Reynolds number. The effect of magnetic field in four strategies, named modes, on ferrofluid flow through the porous media is presented.

Laminar Natural Convection Heat Transfer From Vertical 7 × 7 Rod Bundles in Liquid Sodium

2019 ◽  
Vol 5 (2) ◽  
Author(s):  
Koichi Hata ◽  
Katsuya Fukuda ◽  
Tohru Mizuuchi
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Convection Heat Transfer ◽  
Liquid Sodium ◽  
Natural Convection Heat Transfer ◽  
Convection Heat ◽  
Rod Bundles ◽  
Nusselt Numbers ◽  
Rod Bundle ◽  
Laminar Natural Convection

Laminar natural convection heat transfer from vertical 7 × 7 rod bundle in liquid sodium was numerically analyzed to optimize the thermal–hydraulic design for the bundle geometry with equilateral square array (ESA). The unsteady laminar three-dimensional basic equations for natural convection heat transfer caused by a step heat flux were numerically solved until the solution reaches a steady-state. The code of the parabolic hyperbolic or elliptic numerical integration code series (PHOENICS) was used for the calculation considering the temperature dependence of thermophysical properties concerned. The 7 × 7 heated rods for diameter (D = 0.0076 m), length (L = 0.2 m) and L/D (=26.32) were used in this work. The surface heat fluxes for each cylinder, which was uniformly heated along the length, were equally given for a modified Rayleigh number, (Raf,L)ij and (Raf,L)Nx×Ny,S/D, ranging from 3.08 × 104 to 4.28 × 107 (q = 1 × 104∼7 × 106 W/m2) in liquid temperature (TL = 673.15 K). The values of ratio of the diagonal center-line distance between rods for bundle geometry to the rod diameter (S/D) for vertical 7 × 7 rod bundle were ranged from 1.8 to 6 on the bundle geometry with ESA. The spatial distribution of average Nusselt numbers for a vertical single cylinder of a rod bundle, (Nuav)ij, and average Nusselt numbers for a vertical rod bundle, (Nuav,B)Nx×Ny,S/D, were clarified. The average values of Nusselt number, (Nuav)ij and (Nuav,B)Nx×Ny,S/D, for the bundle geometry with various values of S/D were calculated to examine the effect of array size, bundle geometry, S/D, (Raf,L)ij and (Raf,L)Nx×Ny,S/D on heat transfer. The bundle geometry for the higher (Nuav,B)Nx×Ny,S/D value under the condition of S/D = constant was examined. The general correlations for natural convection heat transfer from a vertical Nx×Ny rod bundle with the ESA and equilateral triangle array (ETA), including the effects of array size, (Raf,L)Nx×Ny,S/D and S/D were derived. The correlations for vertical Nx×Ny rod bundles can describe the theoretical values of (Nuav,B)Nx×Ny,S/D for each bundle geometry in the wide analytical range of S/D (=1.8–6) and the modified Rayleigh number ((Raf,L)Nx×Ny,S/D = 3.08 × 104 to 4.28 × 107) within −9.49 to 10.6% differences.

Natural Convection Heat Transfer From Vertical 7x7 Rod Bundles in Liquid Sodium

2017 ◽  
Author(s):  
Koichi Hata ◽  
Katsuya Fukuda ◽  
Tohru Mizuuchi
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Convection Heat Transfer ◽  
Liquid Sodium ◽  
Natural Convection Heat Transfer ◽  
Convection Heat ◽  
Rod Bundles ◽  
Nusselt Numbers ◽  
Rod Bundle ◽  
Square Array

Natural convection heat transfer from vertical 7×7 rod bundle in liquid sodium was numerically analyzed to optimize the thermal-hydraulic design for the bundle geometry with equilateral square array, ESA. The unsteady laminar three dimensional basic equations for natural convection heat transfer caused by a step heat flux were numerically solved until the solution reaches a steady-state. The PHOENICS code was used for the calculation considering the temperature dependence of thermo-physical properties concerned. The 7×7 test rods for diameter (D = 7.6 mm), heated length (L = 200 mm) and L/d (= 26.32) were used in this work. The surface heat fluxes for each cylinder were equally given for a modified Rayleigh number, (Rf,L)ij and (Rf,L)Nx×Ny,S/D, ranging from 3.08×104 to 4.28×107 (q = 1×104∼7×106 W/m2) in liquid temperature (TL = 673.15 K). The values of S/D, which are ratios of the diameter of flow channel for bundle geometry to the rod diameter, for vertical 7×7 rod bundle were ranged from 1.8 to 6 on the bundle geometry with equilateral square array. The spatial distribution of average Nusselt numbers for a vertical single cylinder of a rod bundle, (Nuav)ij, and average Nusselt numbers for a vertical rod bundle, (Nuav,B)Nx×Ny,S/D, were clarified. The average value of Nusselt number, (Nuav)ij and (Nuav,B)Nx×Ny,S/D, for the bundle geometry with various values of S/D were calculated to examine the effect of array size, bundle geometry, S/D, (Rf,L)ij and (Rf,L)Nx×Ny,S/D on heat transfer. The bundle geometry for the higher (Nuav,B)Nx×Ny,S/D value under the condition of S/D = constant was examined. The general correlations for natural convection heat transfer from a vertical Nx×Ny rod bundle with the equilateral square and triangle arrays including the effects of array size, (Rf,L)Nx×Ny,S/D and S/D were derived. The correlations for vertical Nx×Ny rod bundles can describe the theoretical values of (Nuav,B)Nx×Ny,S/D for each bundle geometry in the wide analytical range of S/D (= 1.8 to 6) and the modified Rayleigh number ((Rf,L)Nx×Ny,S/D = 3.08×104 to 4.28×107) within −9.49 to 10.6 % differences.

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