Open Access

ARTICLE

Characterization of Purged Gas-Liquid Two-Phase Flow in a Molten Salt Regulating Valve

Shuxun Li^1,2, Jianwei Wang^1,2,*, Tingjin Ma¹, Guolong Deng^1,2, Wei Li^1,2

1 School of Petrochemical Technology, Lanzhou University of Technology, Lanzhou, 730050, China
2 Machinery Industry Pump and Special Valve Engineering Research Center, Lanzhou University of Technology, Lanzhou, 730050, China

* Corresponding Author: Jianwei Wang. Email:

Fluid Dynamics & Materials Processing 2025, 21(4), 959-988. https://doi.org/10.32604/fdmp.2025.059570

Received 11 October 2024; Accepted 17 December 2024; Issue published 06 May 2025

Abstract

In photothermal power (solar energy) generation systems, purging residual molten salt from pipelines using high-pressure gas poses a significant challenge, particularly in clearing the bottom of regulating valves. Ineffective purging can lead to crystallization of the molten salt, resulting in blockages. To address this issue, understanding the gas-liquid two-phase flow dynamics during high-pressure gas purging is crucial. This study utilizes the Volume of Fluid (VOF) model and adaptive dynamic grids to simulate the gas-liquid two-phase flow during the purging process in a DN50 PN50 conventional molten salt regulating valve. Initially, the reliability of the CFD simulations is validated through comparisons with experimental data and findings from the literature. Subsequently, simulation experiments are conducted to analyze the effects of various factors, including purge flow rates, initial liquid accumulation masses, purge durations, and the profiles of the valve bottom flow channels. The results indicate that the purging process comprises four distinct stages: Initial violent surge stage, liquid discharge stage, liquid partial fallback stage, liquid dissipation stage. For an initial liquid height of 17 mm at the bottom of the valve, the critical purge flow rate lies between 3 and 5 m/s. Notably, the critical purge flow rate is independent of the initial liquid accumulation mass. As the purge gas flow rate increases, the volume of liquid discharged also increases. Beyond the critical purge flow rate, higher purge gas velocities lead to shorter purge durations. Interestingly, the residual liquid mass after purging remains unaffected by the initial liquid accumulation. Additionally, the flow channel profile at the bottom of the valve significantly influences both the critical purge speed and the efficiency of the purging process.

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Keywords

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