Onset of flow instability with one-side heated swirl tube for fusion reactor safety

Lim, Ji Hwan; Lee, Su-Won; Oh, Hoongyo; Park, Minkyu; Hwang, Donkoan; Kim, Moo Hwam; Jo, HangJin

doi:10.1088/1741-4326/ac3c83

Cited by 14 publications

(5 citation statements)

References 33 publications

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“…A solenoid valve with on-off function is installed under the accumulator to discharge all used water out of the loop after the experiment. Detailed information on the experimental equipment or loop design process can be found in previous papers [39][40][41]. Table 1 summarizes the ranges of the system parameters and uncertainties of the measured variables of the sub-cooled flow boiling experiment conducted in this study.…”

Section: Experimental Methods 21 Test Loopmentioning

confidence: 99%

“…The heating area loaded by the heater was designed to have a width of 23 mm and a length of 100 mm, based on the results of a previous study, in which the peak heat flux of several MW m −2 was loaded on a diverter whose length did not exceed 100 mm [44]. The results of a number of experiments conducted for the heater development or heater design process can be found in previous studies [39][40][41].…”

Section: One-sided Heating Systemmentioning

confidence: 99%

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Enhanced single-phase heat transfer performance via vortex secondary flow in hypervapotron configuration

Lim¹,

Park²

2021

Phys. Scr.

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As the hypervapotron (HV) heat sink is used to cool many areas inside the fusion tokamak, it is essential to understand its heat transfer performance to calculate the thermal efficiency of the power generation system. Therefore, in this study, the single-phase (SP) heat transfer performance of HV heat sink was evaluated through sub-cooled flow boiling experiments under one-side high-heat load conditions. When vapor is generated inside the heat sink, flow instability and a potential risk of reaching the critical heat flux are created. Therefore, in commercial power plants, cooling systems tend to operate in the SP regime. System parameters that can be adjusted in the power generation system include the system pressure, mass flow rate, and subcooling, and the effect of these three parameters on the heat transfer performance in the SP regime was analyzed. It was experimentally observed that the mass flow rate was the most influential variable. The prediction performance of the SP forced convection heat transfer correlations of the existing conventiaonl channel were evaluated. The results revealed that they tended to under-predict the heat transfer performance of the HV heat sink. In addition, the same trends were found when the forced convection heat transfer correlation of the curved channel was evaluated. The reasons for the former and the latter are that the heat transfer enhancement effect by the vortex flow occurring between the fins of the HV heat sink is not reflected in the correlations, and the vortex effect of the HV heat sink is not expressed as a variable. Therefore, a new vortex forced convection heat transfer correlation was developed through the newly defined Dean number of the HV heat sink. The developed correlation recorded an average error rate of 0.48%.

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Section: Experimental Methods 21 Test Loopmentioning

confidence: 99%

Section: One-sided Heating Systemmentioning

confidence: 99%

Enhanced single-phase heat transfer performance via vortex secondary flow in hypervapotron configuration

Lim¹,

Park²

2021

Phys. Scr.

Self Cite

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“…Table 1 shows the range of system parameters and uncertainties of the measuring equipment for the subcooled flow boiling experiment conducted in this study. Detailed information on the loop design process and equipment can be found in previous studies [12,13,[17][18][19].…”

Section: Methodsmentioning

confidence: 99%

Predicting the onset of nucleate boiling heat flux of one-side heated flat heat sink in sub-cooled flow conditions for fusion divertor cooling

Lim¹,

Park²

2021

Phys. Scr.

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For the cooling system of the future, nuclear fusion tokamak, to operate stably and continuously, it is important to identify potential hazards that may occur in the system in advance. Among the various potential hazards associated with the nuclear fusion tokamak, the onset of nucleate boiling (ONB) is a point at which the heat-transfer mechanism changes dramatically and is a crucial factor that must be addressed. In particular, the equipment inside the tokamak is loaded with a heat flux of several MW/m2 under single-side heating conditions, and it is important to predict the ONB under these special heating conditions. Therefore, in this study, the ONB of a flat heat sink was experimentally investigated under highly subcooled flow conditions. Based on the physical understanding of the thermo-hydraulic aspect of the ONB, the wall temperature gradient change point, which is mainly used in the subcooled flow condition, was selected as the ONB detection criterion. Trends in the ONB heat flux change were analyzed as representative system parameters that can be tuned in the cooling system, such as subcooling, mass flow rate, and pressure. In addition, the ONB correlations developed in the previous studies were evaluated for predicting the performance under one-side high heat load conditions. However, the large difference in the experimental conditions (range of system parameters and heating conditions) and the fact that the influence of system parameters was not reflected in the correlation resulted in high error rates. Therefore, the ONB correlation that can be used in the tokamak heat flux condition was newly developed through a dimensional analysis that can effectively reflect the influences in the correlation through dimensionless numbers. The developed correlation can be of great help in designing a diverter or blanket cooling system and establishing an operational strategy.

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“…To address this issue, the RANdom SAMple consensus (RANSAC) algorithm was used in our regression analysis. RANSAC has the characteristic of completely ignoring data above a certain threshold, allowing for the mitigation of the influence of outliers and the derivation of an optimal model supported by the bulk of the data [53,54]. The RANSAC algorithm operates under the following assumptions: (1) that the dataset contains outliers; (2) that the dataset can be expressed using mathematical model factors; (3) that inlier data can be incorrectly determined to be outliers as a result of extreme values, incorrect measurement of data, or incorrect assumptions about data interpretation; and (4) that there is an algorithm that can predict the model parameters or fit the data in a given set of inliers.…”

Section: Python Code Developmentmentioning

confidence: 99%

Study on onset of nucleate boiling with screw tube for fusion reactor application

Lim

Park

2022

Nucl. Fusion

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The onset of nucleate boiling (ONB) is the point at which the heat transfer mechanism in fluids changes and is one of the thermo-hydraulic factors that must be considered when establishing a cooling system operation strategy. Because the high heat flux of several MW/m2, which is loaded within a tokamak, is applied under a one-side heating condition, it is necessary to determine a correlative relation that can predict ONB under special heating conditions. In this study, the ONB of a one-side-heated screw tube was experimentally analyzed via a subcooled flow boiling experiment. The helical nut structure of the screw tube flow path wall allows for improved heat transfer performance relative to smooth tubes, providing a screw tube with a 53.98% higher ONB than a smooth tube. The effects of the system parameters on the ONB heat flux were analyzed based on the changes in the heat transfer mechanism, with the results indicating that the flow rate and degree of subcooling are proportional to the ONB heat flux because increasing these factors improves the forced convection heat transfer and increases the condensation rate, respectively. However, it was observed that the liquid surface tension and latent heat decrease as the pressure increases, leading to a decrease in the ONB heat flux. An evaluation of the predictive performance of existing ONB correlations revealed that most have high error rates because they were developed based on ONB experiments on micro-channels or smooth tubes and not under one-side high heat load conditions. To address this, we used dimensional analysis based on Python code to develop new ONB correlations that reflect the influence of system parameters.

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Onset of flow instability with one-side heated swirl tube for fusion reactor safety

Cited by 14 publications

References 33 publications

Enhanced single-phase heat transfer performance via vortex secondary flow in hypervapotron configuration

Enhanced single-phase heat transfer performance via vortex secondary flow in hypervapotron configuration

Predicting the onset of nucleate boiling heat flux of one-side heated flat heat sink in sub-cooled flow conditions for fusion divertor cooling

Study on onset of nucleate boiling with screw tube for fusion reactor application

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