Simulation research on the boiling heat transfer characteristics of liquid sodium under microgravity

doi:10.11949/0438-1157.20250481

Abstract

Abstract:

With the advancement of space nuclear power technology, sodium-cooled fast reactors have become a promising energy solution for space systems. However, the heat transfer mechanism of liquid metal sodium boiling in microgravity is unclear, and there is a lack of effective methods to prevent heat transfer degradation. This study conducts a numerical investigation on liquid sodium flow boiling in space sodium-cooled fast reactors under microgravity using a two-fluid model. A comparative analysis of heat transfer performance between microgravity and normal gravity conditions is performed, and the effects of inlet velocity and subcooling degree on boiling behavior in vertical channels under microgravity are systematically examined. The results demonstrate that, compared to normal gravity, microgravity degrades the boiling heat transfer performance of liquid sodium, advances the boiling onset time, and increases susceptibility to heat transfer deterioration. Enhancing inlet velocity or subcooling significantly improves heat transfer under microgravity. Notably, no heat transfer deterioration occurs when the inlet velocity reaches 2.0 m·s^-1 combined with an inlet subcooling of 300 K. This work elucidates the unique heat transfer characteristics of liquid sodium flow boiling under microgravity and provides critical theoretical insights for the safety design of the primary loop in space sodium-cooled fast reactors under microgravity environments.

Key words: boiling, microgravity, heat transfer, two-phase flow, numerical simulation

摘要：

随着空间核动力技术的进步，钠冷快堆成为空间核动力系统理想能源方案，然而微重力下液态金属钠沸腾传热机制不清晰，且缺少防止传热恶化的有效方法。围绕微重力下空间钠冷快堆中液钠流动沸腾问题开展了数值模拟研究，采用双流体模型，对比了常重力与微重力下液钠流动沸腾传热性能，并分析了入口流速以及入口过冷度对微重力下竖直管道中液钠沸腾传热性能的影响。结果表明，与常重力相比，微重力下液钠沸腾传热性能下降，沸腾起始时间提前，更容易发生传热恶化；增加入口流速与过冷度能改善微重力下液钠沸腾传热性能，当入口流速为2.0 m·s^-1，入口过冷度为300 K时，未发生传热恶化。研究结果解释了微重力下液钠流动沸腾传热特性，为空间钠冷快堆一回路微重力下的安全设计提供了理论指导。

关键词: 沸腾, 微重力, 传热, 两相流, 数值模拟

CLC Number:

TK 124

Yufeng ZENG, Yurong HE, Tianyu WANG. Simulation research on the boiling heat transfer characteristics of liquid sodium under microgravity[J]. CIESC Journal, 2025, 76(11): 5697-5708.

曾育峰, 何玉荣, 王天宇. 微重力下液态金属钠沸腾传热特性模拟研究[J]. 化工学报, 2025, 76(11): 5697-5708.

Figures/Tables 13

Fig.1 Mass transfer coefficient r sensitivity analysis

Fig.2 Structure diagram of vertical channel configuration

Table 1 Parameters used in the simulation［32-33］

物理量		数值
竖直通道	x、y方向尺寸/m	0.0066、1.76
	x、y方向网格数/个	10、1800
	通道宽度D/m	0.0066
	加热段长度L₁/m	1
	绝热段长度L₂/m	0.38
液态钠	液钠比定压热容C_pl /(J·kg^-1·K^-1)	1260
	液钠密度ρ_l /(kg·m^-3)	780
	液钠热导率λ_l /(W·m^-1·K^-1)	55.03
	液钠黏度μ_l /(Pa·s)	0.00019
	相变潜热∆H_g/(kJ·kg^-1)	3881.3
钠蒸气	钠蒸气比定压热容C_p_v/(J·kg^-1·K^-1)	2560
	钠蒸气密度ρ_v/(kg·m^-3)	0.281
	钠蒸气热导率λ_v/(W·m^-1·K^-1)	0.048
	钠蒸气黏度μ_v/(Pa·s)	0.000022

Fig.3 Grid independence test and model validation

Fig.4 Boiling inception time of liquid sodium under different gravity conditions

Fig.5 Average temperature variation curve of the end cross-section in the heating section under different gravity conditions

Fig.6 Phase distribution contour plot within the channel at 0.74 s under different gravity conditions

Fig.7 Distribution of wall temperature and surface heat transfer coefficient along the channel under different inlet velocities

Fig.8 Contour plot of liquid sodium boiling phase distribution in vertical channel under different inlet velocities

Fig.9 Cross-sectional average void fraction and time of occurrence for boiling inception and heat transfer deterioration under different inlet velocities

Fig.10 Distribution of wall temperature and surface heat transfer coefficient under different inlet subcooling

Fig.11 Contour plot of liquid sodium boiling phase distribution in vertical channel under different inlet subcooling

Fig.12 Cross-sectional average void fraction and time of occurrence for boiling inception and heat transfer deterioration under different inlet subcooling

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