A Compressible Approach to Solve Combined Natural Convection-Radiation Heat Transfer in Participating Media

Two-dimensional simulations of steady natural convection and radiation heat transfer for a 14×14 pressurized water reactor (PWR) spent nuclear fuel assembly within a square basket tube of a typical transport package were conducted using a commercial computational fluid dynamics package. The assembly is composed of 176 heat generating fuel rods and 5 larger guide tubes. The maximum cladding temperature was determined for a range of assembly heat generation rates and uniform basket wall temperatures, with both helium and nitrogen backfill gases. The results are compared with those from earlier simulations of a 7×7 boiling water reactor (BWR). Natural convection/radiation simulations exhibited measurably lower cladding temperatures only when nitrogen is the backfill gas and the wall temperature is below 100°C. The reduction in temperature is larger for the PWR assembly than it was for the BWR. For nitrogen backfill, a ten percent increase in the cladding emissivity (whose value is not well characterized) causes a 4.7% reduction in the maximum cladding to wall temperature difference in the PWR, compared to 4.3% in the BWR at a basket wall temperature of 400°C. Helium backfill exhibits reductions of 2.8% and 3.1% for PWR and BWR respectively. Simulations were performed in which each guide tube was replaced with four heat generating fuel rods, to give a homogeneous array. They show that the maximum cladding to wall temperature difference versus total heat generation within the assembly is not sensitive to this geometric variation.

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Natural Convection Coupled with Radiation Heat Transfer in Slanted Square and Shallow Enclosures Containing an Isotropic Scattering Medium

Numerical Heat Transfer Part A Applications ◽

10.1080/10407782.2015.1052314 ◽

2015 ◽

Vol 68 (12) ◽

pp. 1369-1393

Author(s):

Lirong Fu ◽

Wenping Zhang ◽

Pingjian Ming ◽

Meng Zhang ◽

Daming Ni

Keyword(s):

Heat Transfer ◽

Natural Convection ◽

Radiation Heat Transfer ◽

Isotropic Scattering ◽

Scattering Medium ◽

Radiation Heat

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Simulation of Radiation Heat Transfer of Three Dimensional Participating Media by Radiative Exchange Method

Heat Transfer: Volume 3 ◽

10.1115/ht2008-56076 ◽

2008 ◽

Author(s):

Mohammad Hadi Bordbar ◽

Timo Hyppa¨nen

Keyword(s):

Heat Transfer ◽

Balance Equation ◽

Radiation Heat Transfer ◽

Three Dimensional ◽

Radiation Balance ◽

Scattering Media ◽

Radiation Heat ◽

Exchange Method ◽

Participating Media ◽

Radiative Exchange

This paper describes the theoretical bases of the Radiative Exchange Method, a new numerical method for simulating radiation heat transfer. By considering radiative interaction between all points of the geometry and solving the radiation balance equation in a mesh structure coarser than the structure used in computational fluid flow calculation, this method is able to simulate radiative heat transfer in arbitrary 3D space with absorbing, emitting and scattering media surrounded by emitting, absorbing and reflecting surfaces. A new concept is introduced, that of the exchange factors between the different elements that are necessary for completing the radiative balance equation set. Using this method leads to a set of algebraic equations for the radiative outgoing power from each coarse cell being produced and the result of this set of equations was then used to calculate the volumetric radiative source term in the fine cell structure. The formulation of the exchange factor for a three-dimensional state and also a mesh size analysis that was conducted to optimize the accuracy and runtime are presented. The results of this model to simulate typical 3D furnace shape geometry, is verified by comparison with those of other numerical methods.

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