Preliminary test of an ultrasonic liquid film sensor for high-temperature steam–water two-phase flow experiments

A prototype liquid film sensor for high-temperature steam–water experiments has been developed. The sensor shape simulates a boiling water reactor (BWR) fuel rod. The pulse-echo method can be utilized to measure the thickness of the liquid film covering the sensor surface. A piezoelectric element is soldered onto the inside of the sensor casing which consists of two curved casing pieces. After the piezoelectric element is attached, the two casing pieces are laser welded together. It is confirmed that the temperature rise at the time of the laser welding does not influence soldering of the piezoelectric element. The pressure proof test shows that the sensor can be used at a high-pressure condition of 7 MPa. Simple air–water experiments are done at atmospheric pressure to confirm the liquid film thickness can be measured with the sensor. The fluctuation of the liquid film thickness is satisfactorily captured with the sensor. The minimum and maximum thicknesses are 0.084 and 0.180 mm, respectively. The amplitude of the waveform at 286 °C is predicted by the calculation based on the acoustic impedance. It is expected that the sensor is able to measure the liquid film thickness even at BWR operating conditions.     

Effect of steam quality on two-phase flow in a natural circulation loop

Ｅｆｆｅｃｔｏｆｓｔｅａｍｑｕａｌｉｔｙｏｎｔｗｏ－ｐｈａｓｅｆｌｏｗｉｎａｎａｔｕｒａｌｃｉｒｃｕｌａｔｉｏｎｌｏｏｐＪｉａＨａｉ－Ｊｕｎ（贾海军）；ＷｕＳｈａｏ－Ｒｏｎｇ（吴少融）；ＷａｎｇＮｉｎｇ（王宁）ａｎｄＹａｏＳｉ－Ｍｉｎ（姚思民）（Ｉｎ...     

An investigation of steam–water countercurrent flow model in TRACE

This paper studies the countercurrent flow model in the TRACE code version 5.0. Steam and water are chosen as the working fluids that flow counter-currently in a circular pipe. Three types of countercurrent flow models, including the Wallis, Kutateladze and Bankoff correlations, are investigated. A single tube model was built to study the Wallis and the Kutateladze correlations, and the variable in the calculation model is the pipe diameter. A perforated plate model was constructed to study the Bankoff correlation, and the variables include the pipe and hole diameters, the number of holes and the plate thickness. The hydraulic diameter of the pipe varied from 2.5 to 200 mm for the tests on the Wallis and Kutateladze correlations. To validate the Bankoff correlation, the hydraulic diameter of the pipe was varied from 50 to 200 mm, and the plate thickness varied from 10 to 40 mm. In this study we validate the countercurrent flow model in the TRACE code, and comment on the application ranges of the three correlations.     

Experimental study of gas–liquid two-phase flow through packed bed under natural circulation conditions

Dry-out phenomena in packed beds or porous media may cause a significant digression of cooling/reaction performance in heat transfer/chemical reactor systems. One of the phenomena responsible for the dry-out in packed beds is known as the counter-current flow limitation (CCFL). In order to investigate the CCFL phenomena induced by gas–liquid two-phase flow in packed beds inside a pool, a natural circulation packed bed test facility was designed and constructed. A total of 27 experimental conditions covering various packing media sizes (sphere diameters: 3.0, 6.4 and 9.5 mm), packed bed heights (15, 35 and 50 cm) and water level heights (1.0, 1.5 and 2.0 m) were tested to examine the CCFL criteria with adiabatic air–water two-phase flow under natural circulation conditions. Both CCFL and flow reversal phenomena were observed, and the experimental data including instantaneous and time-averaged void fraction, differential pressure and superficial gas–liquid velocities were collected. The CCFL criteria were determined when periodical oscillations of void fraction and differential pressure appear. In addition, the Wallis correlation for CCFL was utilized for data analysis, and the Wallis coefficient, C, was determined experimentally from the packed bed CCFL tests. Compared to the existing data-sets in literature, the higher C values obtained in the present experiment suggest a possibly higher dry-out heat flux for natural circulation debris systems, which may be due to the water supply from both top and bottom surfaces of the packed beds. Considering the effects of bed height and hydraulic diameter of the packing media, a newly developed model for the Wallis coefficient, C, under natural circulation CCFL is presented. The present model can predict the experimental data with an averaged absolute error of ±7.9%.     

Improvement of a physical model for blockage formation of solid–liquid mixture flow with freezing for core safety evaluation of SFRs

The SIMMER code has been developed to analyze event progression during core disruptive accidents (CDAs) in sodium-cooled fast reactors. One of the key phenomena during CDAs is the discharge of molten fuel from the core region which reduces the reactivity effectively. The discharge flow is inhibited by blockage formation due to freezing of the molten fuel. Then, the blockage formation is enhanced by unmolten fuel which forms solid–liquid mixture flow with the molten fuel. A physical model for blockage formation of solid–liquid mixture flow with freezing in the SIMMER code is improved in this study to dissolve some inconsistencies between the modeling and the physical phenomena involved in the solid–liquid mixture flow with freezing for more precise evaluation of CDA. The improved model is validated with a systematical procedure through a benchmark analysis of an experiment. Consequently, experimental penetration behaviors are simulated reasonably by the SIMMER code analysis with the improved model while excessive blockage formation occurred in the analysis with the original model.     

Spatio-temporal evolution characteristics and pattern formation of a gas–liquid interfacial AC current argon discharge plasma with a deionized water electrode

A discharge ignited by an AC power source in contact with deionized water as one of the electrodes is investigated. Immediately after initiation, the discharge exhibits a unique phenomenon: the gasphase discharge is extended into the liquid. Later, a cone-like structure is observed at the liquid surface. Synchronous monitoring of current–voltage characteristics and liquid properties versus time suggests that the discharge shapes are functions of the liquid properties. The spatio-temporal profiles indicate the potential effects of water, ambient air impurities, and metastable argon on the discharge chemistry. This becomes more obvious near the liquid surface due to increasing production of various transient reactive species such as ·OH and NO·. Moreover, it is revealed that thermalization of the rotational population distributions of the rotational states(N' ≤ 6,J'≤13/2) in the Q_1 branch of the OH(A~2∑~+,v'S=0→X~2∏_(3/2),v'=0 ) band ro-vibrational system is influenced by the humid environment near the liquid surface. In addition, the transient behaviors of instantaneous concentrations of long-lived reactive species(LRS) such as H_2O_2,NO_2~-, and-NO_3~- are observed with lengthening the discharge time. The production of multiple transient and LRS proposes AC excited gas–liquid argon discharge as a potential applicant in industrial wastewater cleaning, clinical medicine, and agriculture.     

Film Boiling in Presence of a Magnetic Field in Liquid Metals Within Framework of Taylor–Helmholtz Instabilities in Application to Fusion Reactor Project

From a consideration of a model for the development of magnetohydrodynamics perturbation at the interface during film boiling on a liquid metal in presence of a magnetic field, an analytical expression for the effect of a magnetic field was derived. The predictions within Taylor–Helmholtz model disagree with the available experimental measurements made on mercury, where for high magnetic field where a vapor layer is expected the frequency bubble departure frequency decreases contrary to the invariable theoretical value predicted.