Effects of inserted sphere on thermal field and heat-transfer characteristics of face-centered-cubic-structured pebble bed

2020 ◽  
Vol 172 ◽  
pp. 115151
Author(s):  
Leisheng Chen ◽  
Jaeyoung Lee
Keyword(s):  
Heat Transfer ◽  
Thermal Field ◽  
Face Centered Cubic ◽  
Heat Transfer Characteristics ◽  
Pebble Bed ◽  
Transfer Characteristics ◽  
Face Centered

scholarly journals Numerical Study on the Thermal Field and Heat Transfer Characteristics of a Hexagonal-Close-Packed Pebble Bed

Computation ◽  
2022 ◽  
Vol 10 (1) ◽  
pp. 1
Author(s):  
Leisheng Chen ◽  
Jiahao Zhao ◽  
Yuejin Yuan ◽  
Jaeyoung Lee
Keyword(s):  
Heat Transfer ◽  
Numerical Study ◽  
Face Centered Cubic ◽  
Heat Transfer Characteristics ◽  
Transfer Coefficients ◽  
Pebble Bed ◽  
Hexagonal Close Packed ◽  
Transfer Characteristics ◽  
Contact Points ◽  
Hcp Structure

Fuel elements in a high-temperature gas-cooled reactor (HTGR) core may be stacked with a hexagonal close-packed (HCP) structure; therefore, analyzing the temperature distribution and heat transfer efficiency in the HCP pebble bed is of great significance to the design and safety of HTGR cores. In this study, the heat transfer characteristics of an HCP pebble bed are studied using CFD. The thermal fields and convective heat transfer coefficients under different coolant inlet velocities are obtained, and the velocity fields in the gap areas are also analyzed in different planes. It is found that the strongest heat transfer is shown near the right vertices of the top and bottom spheres, while the weakest heat transfer takes place in areas near the contact points where no fluid flows over; in addition, the correlation of the overall heat transfer coefficient with the Reynolds number is proposed as havg = 0.1545(k/L)Re0.8 (Pr = 0.712, 1.6 × 104 ≤ Re ≤ 4 × 104). It is also found that the heat transfer intensity of the HCP structure is weaker than that of the face-centered-cubic structure. These findings provide a reference for reactor designers and will contribute to the development of safer pebble-bed cores.

scholarly journals Effect of inserted sphere size on heat transfer characteristics of FCC structured pebble bed in a HTGR

2019 ◽  
Vol 128 ◽  
pp. 03004 ◽  
Author(s):  
Leisheng Chen ◽  
Jaeyoung Lee
Keyword(s):  
Heat Transfer ◽  
Hot Spots ◽  
Maximum Velocity ◽  
Severe Accident ◽  
Sphere Diameter ◽  
Face Centered Cubic ◽  
Heat Transfer Characteristics ◽  
Pebble Bed ◽  
Small Sphere ◽  
Face Centered

Hot spots appearing in an operating high temperature gas-cooled reactor (HTGR) core have been considered as the most possible reason leading to a severe accident like fission production releasing to the environment, therefore, investigation on their positions and thus seeking ways to reduce the possibility of their appearance have attracted scientists’ attention. In our previous studies, heat transfercharacteristics of a face–centered–cubic (FCC) structured pebble–bed have been discussed,and a correlation on heat transfer coefficient with Reynolds number was presented. In this study, a method, placing a small sphere in thegap area, which is able to enhance the convective heat transfer wasproposed and the effect verifiedas well. The influence of the sphere diameter on heat transfer performances wasinvestigated in details. It is concluded through results analysis that (1) inserted sphere lowered thelocal surface temperature of adjacent pebbles by varying surrounding flow field;(2) maximum velocity of the fluid and average heat transfer coefficientincreased with sphere diameter, particularly, comparing with no small sphere case, 12.95% enhancement was achieved. Such findings may provide dataand information for reactor designers, andhelp to develop a safer HTGR pebble–bedcore.

Research on Heat Transfer Characteristics of the Thermometric Sphere in HTR-10

2018 ◽  
Author(s):  
Shiyan Sun ◽  
Youjie Zhang ◽  
Yanhua Zheng ◽  
Xiang Fang ◽  
Xiaoyong Yang
Keyword(s):  
Heat Transfer ◽  
Thermal Equilibrium ◽  
Reactor Core ◽  
Fluid Temperature ◽  
Heat Transfer Characteristics ◽  
Pebble Bed ◽  
The Core ◽  
Temperature Measuring ◽  
Transfer Characteristics ◽  
Metal Wires

During the operation of the High Temperature Gas-cooled Reactor (HTGR), the hot-spot temperature in the reactor core must be lower than the maximum permissible temperature of the fuel elements and the materials of construction, so that the reactor kept safe. However, no fixed temperature-measuring devices can be set in a pebble-bed core. A special spherical temperature-measuring device is adopted to make sure it brings as small impact to the reactor operation as possible. There are several metal wires with different melting points inside. The graphite thermometric balls will be put onto the top of HTR-10 reactor core, and they record and reflect the highest temperature in different positions in the core when flowing in the pebble bed. Before the reactor core temperature-measuring experiment of HTR-10, we must study the heat transfer characteristics of the graphite thermometric sphere to find out the relationship of the melting conditions and the temperature in the reactor core. A 3-D model of the graphite thermometric ball is established, and CFD method is adopted to research and figure out the thermal equilibrium time and temperature difference between the metal wires in the ball and the hot fluid outside the balls. Multiple situations are simulated, and the heat transfer process of the thermometric sphere is comprehensively studied. The heat convection is certified the most important aspect. Thermal equilibrium can be achieved within 19 minutes, far shorter than the period while the spheres flowing through the core. The simulation results can also applied to derive the thermal fluid temperature backward.

Sign in / Sign up

Export Citation Format

Share Document