Analysis of the flow pattern of entrained bubbly flow in a molten salt reactor heat exchanger based on CFD-PBM method

WANG Ziye; ZHU Guifeng; CHEN Liang; LIANG Xiaolin; ZOU Yang

doi:10.3724/j.0253-3219.2026.hjs.49.250426

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Analysis of the flow pattern of entrained bubbly flow in a molten salt reactor heat exchanger based on CFD-PBM method

Special Issue of Excellent Papers on The Second Academic Annual Conference of the Research Reactor and Innovative Reactor Association of Chinese Nuclear Society | 更新时间：2026-07-29

- Analysis of the flow pattern of entrained bubbly flow in a molten salt reactor heat exchanger based on CFD-PBM method
- NUCLEAR TECHNIQUES Vol. 49, Issue 7, Article number: 071122(2026)
- 作者机构：
  
  1.中国科学院上海应用物理研究所上海 201800
  2.钍基核裂变能全国重点实验室上海 201800
  3.中国科学院大学北京 100049
- 作者简介：
  
  WANG Ziye, male, born in 1998, graduated from ShanghaiTech University with a master's degree in 2024, focusing on CFD analysis and experimental verification of bubble entrainment in molten salt reactor
  ZHU Guifeng, E-mail: zhuguifeng@sinap.ac.cn
  ZOU Yang, E-mail: zouyang@sinap.ac.cn
- 基金信息：
  
  Shanghai Natural Science Foundation(25ZR1401383);Thorium Based Molten Salt Reactor Nuclear Energy System Industry Fund Project(SINAP-CYJJ-202401;SINAP-CYJJ-202501)
- DOI：10.3724/j.0253-3219.2026.hjs.49.250426
  CLC： TL99
- Received：05 December 2025，
  
  Revised：2026-02-28，
  
  Online First：29 July 2026，
  
  Published：15 July 2026
- 稿件说明：
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王子业,朱贵凤,陈亮等.基于CFD-PBM方法熔盐堆换热器内夹带气泡流动规律分析[J].核技术,2026,49(07):071122.

WANG Ziye,ZHU Guifeng,CHEN Liang,et al.Analysis of the flow pattern of entrained bubbly flow in a molten salt reactor heat exchanger based on CFD-PBM method[J].NUCLEAR TECHNIQUES,2026,49(07):071122.
王子业,朱贵凤,陈亮等.基于CFD-PBM方法熔盐堆换热器内夹带气泡流动规律分析[J].核技术,2026,49(07):071122. DOI： 10.3724/j.0253-3219.2026.hjs.49.250426. CSTR： 32193.14.hjs.CN31-1342/TL.2026.49.250426.

WANG Ziye,ZHU Guifeng,CHEN Liang,et al.Analysis of the flow pattern of entrained bubbly flow in a molten salt reactor heat exchanger based on CFD-PBM method[J].NUCLEAR TECHNIQUES,2026,49(07):071122. DOI： 10.3724/j.0253-3219.2026.hjs.49.250426. CSTR： 32193.14.hjs.CN31-1342/TL.2026.49.250426.

摘要

夹带气泡的引入对熔盐堆（Molten Salt Reactor，MSR）反应性控制、换热性能以及难溶裂变产物的迁移产生影响。其中换热器中夹带气泡流动十分复杂，且缺少实验数据，边界条件与流动分布规律的关系并不明确，使得气泡对换热器内换热性能和难溶裂变产物迁移行为等研究难以进一步开展。本文运用计算流体力学（Computational Fluid Dynamics，CFD）手段，采用基于群体平衡模型（Population Balance Model，PBM）的非均匀多尺寸组离散形式（inhomogeneous Multiple Size Group Model，iMUSIG），分析了两种换热器在不同入口速度、气体份额和气泡尺寸边界条件下，从入口到出口的速度场、气体份额、气泡尺寸和界面面积浓度（Interfacial Area Concentration，IAC）分布。结果表明，两种换热器中流场具有相同的涡结构而具有类似的气体聚集现象；气泡尺寸增加促进了气体聚集，高流速促使气体向涡心聚集；高气体份额和更低的速度促进气泡聚并，尺寸增大；从入口到出口，界面面积浓度由于单位气体份额内气泡尺寸增大呈下降趋势，低气体份额和大气泡尺寸的界面面积浓度变化平稳。以上结果为熔盐换热器内夹带气泡带来的影响研究提供参考。

Abstract

Background

Entrained bubbles in molten salt reactors affect reactivity control

heat transfer performance

and the migration of insoluble fission products. However

the relationship between inlet boundary conditions and bubbly-flow distribution in molten-salt heat exchangers remains unclear because of complex internal flow structures and limited experimental data.

Purpose

This study aims to investigate the flow patterns of entrained bubbly flow in molten-salt heat exchangers under different inlet velocities

gas fractions

and bubble-size boundary conditions.

Methods

Firstly

an inhomogeneous multiple size group model based on the population balance model was coupled with computational fluid dynamics to simulate polydisperse bubbly flow in two simplified shell-and-tube heat exchangers. Then

horizontal and vertical heat exchanger configurations were compared under varying inlet velocities

inlet gas fractions

and inlet bubble diameters. Finally

the distributions of velocity

gas fraction

bubble size

and interfacial area concentration from the inlet to the outlet were analyzed using consistent mesh and solver settings. Because simplified geometries were used

the results are mainly applicable to compact heat exchangers or similar simplified flow units with comparable symmetry and large-scale periodic flow structures.

Results

The vortex structures of the flow fields remain stable when the inlet velocity is 1.8~5.3 m·s

-1

in the horizontal heat exchanger and 2~5 m·s

-1

in the vertical heat exchanger

leading to similar gas accumulation behavior in both configurations. Under different inlet bubble diameters

the gas fraction ranges from 0.4% to 1.1% and increases with increasing inlet bubble diameter

while a local gas fraction exceeding 3% appears in the vortex region when the inlet gas fraction is only 0.5%. Higher inlet gas fractions and lower velocities promote bubble coalescence and increase the bubble size; the maximum bubble size in the horizontal heat exchanger is 1.9 times that in the vertical heat exchanger under the maximum gas-fraction condition and 2.3 ti

mes that under the minimum-velocity condition. From the inlet to the outlet

the interfacial area concentration generally decreases because the bubble size per unit gas fraction increases

whereas the interfacial area concentration changes steadily at a low inlet gas fraction of 0.25% and a large inlet bubble diameter of 0.5 mm.

Conclusion

This study reveals the effects of heat exchanger orientation and inlet boundary conditions on gas accumulation

bubble coalescence

and interfacial area concentration evolution in molten-salt heat exchangers. The quantitative results

including the 0.4%~1.1% gas-fraction range

the local gas fraction exceeding 3%

and the 1.9-2.3-fold difference in maximum bubble size between the two configurations

provide a reference for evaluating bubble entrainment

mass transfer

and heat exchanger optimization in molten salt reactor systems.

关键词

Keywords

references

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