Research Papers: Heat and Mass Transfer

A Numerical Investigation on the Influence of Porosity on the Steady-State and Transient Thermal–Hydraulic Behavior of the PBMR

[+] Author and Article Information
Masoumeh Sadat Latifi

Department of Energy Engineering and Physics,
Amirkabir University of Technology,
424 Hafez Ave,
Tehran, Iran
e-mail: m.s.latifi@aut.ac.ir

Saeed Setayeshi

Department of Energy Engineering and Physics,
Amirkabir University of Technology,
424 Hafez Ave.
Tehran, Iran
e-mail: setayesh@aut.ac.ir

Giuseppe Starace

Department of Engineering for Innovation,
University of Salento,
Lecce 73100, Italy
e-mail: giuseppe.starace@unisalento.it

Maria Fiorentino

Department of Engineering for Innovation,
University of Salento,
Lecce 73100, Italy
e-mail: maria.fiorentino@unisalento.it

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received January 27, 2016; final manuscript received May 3, 2016; published online June 7, 2016. Editor: Portonovo S. Ayyaswamy.

J. Heat Transfer 138(10), 102003 (Jun 07, 2016) (9 pages) Paper No: HT-16-1034; doi: 10.1115/1.4033544 History: Received January 27, 2016; Revised May 03, 2016

The thermal–hydraulic phenomena in a pebble bed modular reactor (PBMR) core have been simulated under steady-state and transient conditions. The PBMR core is basically a long right circular cylinder with a fuel effective height of 11 m and a diameter of 3.7 m. It contains approximately 452,000 fuel pebbles. A three-dimensional computational fluid dynamic (CFD) model of the PBMR core has been developed to study the influence of porosity on the core performance after reactor shutdown. The developed model was carried out on a personal computer using ANSYS fluent 14.5. Several important heat transfer and fluid flow parameters have been examined under steady-state and transient conditions, including the coolant temperature, effective thermal conductivity of the pebble bed, and the decay heat. Porosity was found to have a significant influence on the coolant temperature, on the effective thermal conductivity of the pebble bed, on the decay heat, and on the required time for heat removal.

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Fig. 1

The vertical power distribution profile

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Fig. 2

Porosity variation as a function of distance from wall

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Fig. 3

The simplified geometry used in the computations

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Fig. 8

Porosity effect on the average temperature across the axial position of the core under transient conditions

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Fig. 6

Porosity effect on the average temperature across the axial position of the core under steady-state conditions

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Fig. 7

Porosity effect on the coolant thermal conductivity across the axial position of the core

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Fig. 4

Grid independence test

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Fig. 5

Comparison between the DIN 25,485 standard calculation and CFD results

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Fig. 9

Porosity effect on the ratio of unsteady to steady-state temperature

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Fig. 10

The porosity effect on the effective thermal conductivity of the pebble bed across the axial position of the core: (a) under steady-state condition and (b) under transient condition

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Fig. 11

Contour plots of the effective thermal conductivity of the pebble bed along the radial direction at the height of 5.5 m of the core in different porosities: (a) ε = 0.36, (b) ε = 0.39, and (c) ε = 0.43

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Fig. 12

The porosity effect on the behavior of the decay heat at various time periods: (a) 2 hrs < t < 20 hrs, (b) 100 hrs < t < 1100 hrs, and (c) 50 weeks < t < 330 weeks



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