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Arabian Journal for Science and Engineering

, Volume 44, Issue 2, pp 981–991 | Cite as

A Numerical Study to Investigate the Effect of Inlet Reynolds Number on the Thermal–Fluid Phenomena in the Supercritical Carbon Dioxide-Cooled Pebble Bed Reactor

  • Masoumeh Sadat LatifiEmail author
  • C. G. du Toit
Research Article - Mechanical Engineering
  • 24 Downloads

Abstract

This paper presents a numerical investigation into thermal–fluid phenomena in a supercritical carbon dioxide-cooled pebble bed reactor (SCPBR) core under steady state using computational fluid dynamic. In this study, a three-dimensional model with the capability to simulate the fluid flow and heat transfer in the SCPBR core has been developed. The developed model was implemented on a personal computer using ANSYS Fluent 14.5. Several important fluid flow and heat transfer parameters have been examined, including the pressure drop over the reactor core, the heat transfer coefficient, the temperature distribution, the coolant density and the coolant velocity. Results obtained from the simulation show that with increasing the inlet Reynolds number, the pressure drop, the coolant density and the heat transfer coefficient increase. However, the coolant temperature and the temperature difference between pebble and coolant decrease with increasing the inlet Reynolds number. The conclusion of the analysis is that supercritical carbon dioxide (S-CO\(_{2})\), compared to other coolants such as helium, could be a suitable coolant for use in a pebble bed reactor due to its large mass density and heat transfer characteristics, which could lead to obtain a higher temperature rise and a lower pressure gradient.

Keywords

CFD Heat transfer \(\hbox {S-CO}_{2}\) SCPBR Reynolds number 

List of symbols

\(a_\mathrm{sf}\)

Surface area per unit volume (1/m)

\(C_{p}\)

Specific heat capacity [J/(kg K)]

d

Diameter of the fuel sphere (pebble) (m)

\(d_\mathrm{peb}\)

Diameter of pebble (m)

e

Emissivity of pebble

\(G_\mathrm{K}\)

Generation of turbulence kinetic energy [\(\hbox {kg}/ (\hbox {m}\,\hbox {s}^{3})\)]

\(h_\mathrm{sf}\)

Fluid–solid heat transfer coefficient (\(\hbox {W}/(\hbox {m}^{2}\) \(\hbox {K})\))

k

Turbulence kinetic energy (\(\hbox {m}^{2}/\hbox {s}^{2}\))

p

Pebble bed packing fraction

P

Pressure (Pa)

\(Q_{\mathrm{th}}\)

Thermal power

Q

Flow rate

Re

Reynolds number

Pr

Prandtl number

\(S_\mathrm{h}\)

Heat source (\(\hbox {W/m}^{3}\))

T

Pebble temperature (K)

\(\Delta T\)

Inlet–outlet temperature difference (K)

u

Superficial mean exit velocity (m/s)

v

Velocity (m/s)

Greek Letters

\(\varepsilon \)

Bed porosity

\(\varepsilon _{\mathrm{e}}\)

Energy dissipation rate (\(\hbox {m}^{2}/\hbox {s}^{3}\))

\(\varepsilon _{b}\)

Volumetric porosity

\(\mu \)

Dynamic viscosity [kg/(m s)]

\(\mu _{\mathrm{t}}\)

Turbulent viscosity [kg/ (m s)]

\(\rho \)

Fluid density (\(\hbox {kg/m}^{3}\))

\(\rho _{\mathrm{fuel} }\)

Power density of each fuel sphere (\(\hbox {W/m}^{3}\))

\(\sigma \)

Stefan–Boltzmann constant   \(=\) 5.670 \(\times \)\(10^{-8} [\hbox {W}/ (\hbox {m}^{2}\, \hbox {K}^{4})\)]

\(\lambda _\mathrm{f}\)

Fluid thermal conductivity [W/(m K)]

\(\lambda _\mathrm{peb}\)

Thermal conductivity of pebble [W/(m K)]

\(\lambda _\mathrm{s}\)

Solid thermal conductivity [W/(m K)]

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Copyright information

© King Fahd University of Petroleum & Minerals 2018

Authors and Affiliations

  1. 1.Department of Energy Engineering and PhysicsAmirkabir University of TechnologyTehranIran
  2. 2.School of Mechanical and Nuclear EngineeringNorth-West UniversityPotchefstroomSouth Africa

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