Impact of dissolved salts on two-phase flow and boiling heat transfer in a natural circulation loop

The intrinsic activity of hydrogen evolution reaction (HER) catalysts has been significantly improved in the past decades, and current efforts are devoted to implement these catalysts for HER applications through electrode design and fabrication. However, HER in an electrode usually involves complex processes including electrochemical reaction, ion transport, bubble behavior, and gas–liquid flow near the electrode surface. The coupling of different processes makes it difficult to accurately analyze the effect of each process on the HER performance of the electrode. In this paper, a multiphase fluid dynamics and mass transport model is proposed to decouple the HER processes and provide a deep understanding on the interactions among those processes. The results reveal a strong interaction between ion transport inside the electrode and bubble detachment/ascending outside the electrode. The surface design can effectively improve the velocity profile of the liquid and hence dominate the ion transport near the electrode, whereas the design of pore structure can remarkably enhance the ions diffusion inside the electrode. In addition, external forced electrolyte flow can further enhance the fluid convection and ion transport when the speed of forced flow is higher than that induced by bubble ascending. These results conclude that the proposed model contributes to the understanding of interactions among electrochemical reaction, ion transport, bubble behavior, and gas–liquid flow near the electrode surface, providing a guideline for HER electrode design.

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“…where Re p is the particle Reynolds number. The departure diameter of the hydrogen gas bubble can be estimated by using the Fritz equation 29,30…”

Section: ■ Model Descriptionmentioning

confidence: 99%

“…The departure diameter of the hydrogen gas bubble can be estimated by using the Fritz equation , where ϑ is the contact angle of the hydrogen gas bubble and Γ is the surface tension.…”

Section: Model Descriptionmentioning

confidence: 99%

Multiphase Fluid Dynamics and Mass Transport Modeling in a Porous Electrode toward Hydrogen Evolution Reaction

Yang

Sun

Tang

et al. 2022

Ind. Eng. Chem. Res.

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“…In the present study, the calculation is performed by setting the initial bubble radius a little larger than the critical bubble radius. It is known that the magnitude of bubble interference would affect bubble growth at the very early stage but has little influence on the later stage. ,,, According to Wang et al, the application of (1 + 10 –9 ) R c as an interference to the initial bubble radius is best for consistencies between the simulation and experimental results for most cases. Therefore, the initial bubble radius is set as (1 + 10 –9 ) R c to proceed with the simulation.…”

Section: Model Developmentmentioning

confidence: 99%

“…Such approaches, however, have failed to address the vapor bubble growth in saline solutions. − The reason is that only the influence of salt from the aspect of physical properties is considered in these approaches. Actually, when a vapor bubble is formed in a superheated liquid, the water is removed from bulk liquid to the gas phase through the gas–liquid interface, while the salts present in the water remain behind. , The dissolved salts are then thought to accumulate in the superheated liquid layer at the vapor–liquid interface, hence influencing the bubble growth period. To the best of our knowledge, few studies have focused on quantitatively modeling the accumulative effect in bubble hydrodynamics simulations.…”

Section: Introductionmentioning

confidence: 99%

Bubble Growth in NaCl Solution: Influence of Superheat Temperature and Solution Concentration

Liu

Zhang

et al. 2021

Ind. Eng. Chem. Res.

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An in-depth understanding of vapor bubble growth characteristics is of great importance for the design and optimization of gas–liquid two-phase flow instruments, which are widely utilized in chemical and thermal engineering processes. The effects of dissolved salts on vapor bubble growth remain unclear at present. In this work, we developed a surface-based bubble growth model to analyze the bubble growth rates and interface hydrodynamics in sodium chloride solution by considering the influence of dissolved salt on bubble growth. The effects of the mass fraction of NaCl and the superheat temperature on bubble growth rates and interface parameters were studied. Further, the characteristics of three typical bubble growth stages were discussed, and the roles of interfacial forces under different operating conditions were demonstrated. The results indicate that the bubble growth rates increased with the increase of the superheat temperature and mass fraction. The effects of the superheat temperature on the bubble duration time are more significant than the NaCl concentration. Besides, the validated surface-based bubble growth model could be extended to other electrolytes by modified solution properties and interface evaporation parameters.

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“…Void fraction and pressure drop measurements are obtained to understand the differences in saturated flow boiling characteristics between seawater and normal water cooled experiments. Previously, natural circulation and sub-cooled boiling studies were conducted using the same artificial seawater coolant [7,8]. Our motivation for the current, more controlled and X-ray monitored saturated flow boiling study was prompted by the two-phase flow differences observed that can be attributed to hydrodynamic and thermodynamic differences in seawater and tap water flow boiling characteristics.…”

Section: Introductionmentioning

confidence: 99%

X-ray Imaging-Based Void Fraction Measurement in Saturated Flow Boiling Experiments with Seawater Coolant

Eckels

Ahmed

Ross

et al. 2021

QuBS

Self Cite

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Recent studies have shown that the presence of dissolved salts in water can exhibit peculiar flow boiling and two-phase flow regimes. Two-phase flow and convective flow boiling are typically characterized with the help of void fraction measurements. To quantitatively improve our understanding of two-phase flow and boiling phenomenon with seawater coolant, void fraction data are needed, which can not be obtained from optical imaging. In this paper, we present experimental void fraction measurements of saturated flow boiling of tap water and seawater using X-ray radiography. X-rays with a maximum energy level of 40 KeV were used for imaging the exit region of the heated test section. At lower heat flux levels, the two phase flow in seawater was bubbly and homogeneous in nature, resulting in higher void fractions as compared to tap water. With an increase in heat flux, the flow regime was similar to slug flow, and void fraction measurements approached similarity with tap water. The predicted pressure drop using the measured void faction shows good agreement with the measured total pressure drop across the test section, demonstrating the validity of the measurement process.

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Impact of dissolved salts on two-phase flow and boiling heat transfer in a natural circulation loop

Cited by 16 publications

References 23 publications

Multiphase Fluid Dynamics and Mass Transport Modeling in a Porous Electrode toward Hydrogen Evolution Reaction

Multiphase Fluid Dynamics and Mass Transport Modeling in a Porous Electrode toward Hydrogen Evolution Reaction

Bubble Growth in NaCl Solution: Influence of Superheat Temperature and Solution Concentration

X-ray Imaging-Based Void Fraction Measurement in Saturated Flow Boiling Experiments with Seawater Coolant

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