Abstract
Pipe height in cylindrical neutron moderator is an important factor to flow pattern, temperature distribution and even the neutron characters. In this paper, the steady-state thermal analysis of cold neutron moderator is carrying out with different heights, conjugated heat transfer method and one-way coupled with a neutron transfer software. The different pipe heights, which is the jet-to-surface distances (H/D = 0.5~6), were compared using a 2D moderator model. The results show that vortex size and velocity gradient from container wall to vortex center vary with H/D, the center of recirculation zone nearly remain constant, and heat transfer effect is weakened on the target bottom surface. With H/D increasing, the velocity at bottom target surface is progressively decreased, and cooling effect is poor, leading to the rise in temperature. The optimal range cooling performance is (H/D) = 0.5~1 at Re = 1.7 × 105, and the enhancement of beam power further strengthens the thermal deposition difference between container and liquid hydrogen. The results can be applied to moderator component design and optimization in the future spallation neutron source.
Highlights
Published: 16 September 2021The Spallation Neutron Source (SNS) project is a large-scale basic scientific platform for neutron scattering research by using high-energy protons to bombard heavy metal targets and slow down neutrons into cold and hot neutrons [1,2]
The results revealed that the large decrease of fluid density of the near wall region compared with the central potential flow region, which leads to the acceleration of flow, deterioration of heat transfer and the suppression of turbulence
The overall heat source of moderator was unevenly distributed, including thermal deposition of external container, hydrogen inlet pipe and liquid hydrogen both gradually increased along axial direction
Summary
The Spallation Neutron Source (SNS) project is a large-scale basic scientific platform for neutron scattering research by using high-energy protons to bombard heavy metal targets and slow down neutrons into cold and hot neutrons [1,2]. Beryllium reflectors, cryogenic liquid hydrogen moderators are main components for neutron production, enhancing neutron intensity and slowing the neutron energy [3,4,5,6]. The coupled moderator with cylindrical shape, which can absorb high-energy neutrons from neutron production target and exchanges neutrons with reflectors, is a key component in spallation neutron sources. A lot of research on heat transfer enhancement of supercritical hydrogen have been carried out by Xie and Zhang [11,12,13] They pointed out that the addition of spherical bulges and grooves on the cooling wall was beneficial to decrease the effect of uneven temperature distribution, increasing surface convective heat transfer coefficient and improving overall cooling performance.
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