Numerical study of natural convection heat transfer from single-layer horizontal spheres under aligned arrangement

doi:10.7523/j.ucas.2021.0034

Abstract

Abstract: With the three dimensional computational model extended based on that by Bejan in two dimensional condition, natural convection heat transfer from the single-layer horizontal spheres under the aligned arrangement is numerically investigated at Gr=10³ for array changing from 3×3 to 15×15. The study found that with the increase of the number of array N, the plume makes the absolute value of negative pressure above the single-layer spheres bigger, which leads to the acceleration of air sucked up through the gaps among the spheres, thereby enhancing heat transfer; the local Nu number in the upstream of the spheres is more affected by the arrangement number since it has a greater influence on the temperature boundary layer in this region. Furthermore, the correlation of the average Nusselt number Nu of the central sphere with the arrangement number N is obtained, which could be predicted by the idea of limit in mathematics that the central sphere of the single-layer spheres has a Nu number of 4.162 8 that is not affected by the increase of the number of surrounding spheres,which reduces by 30.2% than that of single sphere at same Gr number. It provides some value of reference not only for the optimal design of the granular flow target of the accelerator driven subcritical system in China, but also for other industrial applications including multi-spherical systems.

Key words: single-layer horizontal spheres, natural convection, idea of limit, average Nusselt number of the central sphere, correlation

CLC Number:

TK124

WANG Dichang, LIU Zeyuan, LIU Jie, LU Wenqiang. Numerical study of natural convection heat transfer from single-layer horizontal spheres under aligned arrangement[J]. Journal of University of Chinese Academy of Sciences, 2023, 40(3): 303-312.

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