A numerical study of convection heat transfer within enclosed horizontal rod bundles

Journal Article · Tue Jan 31 23:00:00 EST 1995 · Nuclear Science and Engineering; (United States)

OSTI ID:6601407

Keyhani, M; Luo, L ^[1]

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1. Univ. of Tennessee, Knoxville, TN (United States). Mechanical and Aerospace Engineering Dept.

The design of casks for transportation, storage, and permanent disposal of spent fuel assemblies requires a clear understanding of the convective and radiative heat transfer processes that take place inside such enclosures. These heat transfer processes depend on internal geometric parameters, surface properties, rate of heat generation by the spent fuel, thermal boundary conditions on the canister surface, and fill medium within the canister. Here, natural-convection heat transfer in enclosed horizontal N[times]N arrays of heated rods with a constant heat flux dissipation is numerically investigated. For a fixed rod diameter d, the width of the isothermal outer enclosure W is fixed at W/d = 20.33. Furthermore, the pitch-to-diameter ratio of the arrays is fixed at P/d = 1.33. The average Nusselt number of each rod Nu[sub d] in N = 3, 5, 7, and 9 arrays is predicted for a modified Rayleigh number Ra[sub d]* range of 1--316 with a constant Prantdl number of Pr = 0.7. Pure conduction results are also obtained for rod bundles ranging from 3[times]3 to 13[times]13. The conduction Nusselt number of the corner rod in the array is found to decrease with the increase in N from 3--7. However, the trend reverses, and the Nusselt number begins to increase for N>9. The convection results show that the bottom-row rods experience the maximum variation in their local Nusselt numbers. For a given Ra[sub d]*, the Nu[sub d] of the rods is found to decrease with the increase in the row number (from bottom to top). The streamlines show that there is significant flow activity in the enclosure, especially in the top-half region. For arrays with N = 3--9, significant convection heat transfer is observed even at Ra[sub d]* = 1. This horizontal orientation with distributed energy sources within the enclosure is suspected to be an inherently unstable phenomenon. The isotherms clearly show that the majority of the energy generated is transferred to the top and side surfaces.

• OSTI ID: 6601407
• Journal Information: Nuclear Science and Engineering; (United States), Journal Name: Nuclear Science and Engineering; (United States) Vol. 119:2; ISSN NSENAO; ISSN 0029-5639
• Country of Publication: United States
• Language: English

Related Subjects

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11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS
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CASKS
CONTAINERS
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NUMERICAL ANALYSIS
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RADIOACTIVE WASTE DISPOSAL
RADIOACTIVE WASTE MANAGEMENT
REACTOR COMPONENTS
SPENT FUEL CASKS
SPENT FUEL ELEMENTS
SPENT FUEL STORAGE
STORAGE
THEORETICAL DATA
TRANSPORT
WASTE DISPOSAL
WASTE MANAGEMENT