angxing Li

Investigation of the effect of magnetic field on melting of solid gallium in a bottom-heated rectangular cavity using the lattice Boltzmann method

ABSTRACT A numerical study is presented for two-dimensional convection melting of solid gallium in a rectangular cavity. The bottom wall of the cavity is uniformly heated and a uniform magnetic field is applied separately in both horizontal and vertical directions. The lattice Boltzmann (LB) method considering the magnetic field force is employed to solve the governing equations. The effects of magnetic field on flow and heat transfer during melting are presented and discussed at Rayleigh number Ra = 1 × 105 and Hartmann number Ha = 0, 15, and 30. The results show that the magnetic field with an inclination angle has a significant impact on the flow and heat transfer in the melting process. For a small Hartmann number, similar melting characteristics are observed for both horizontally applied and vertically applied magnetic fields. For a high value of Hartmann number, it is found that in the earlier stage of melting process, the flow retardation effect caused by the horizontally applied magnetic field is less obvious than that caused by the vertically applied magnetic field. However, the opposite is true in the later stage.

Experimental Study of Two-Phase Flow Regime and Pressure Drop in a Particulate Bed Packed with Multidiameter Particles

Abstract This paper documents an experimental study on two-phase flow regimes and frictional pressure drop characteristics in a particulate (porous) bed packed with multidiameter (1.5-, 3-, and 6-mm) glass spheres. The experimental results provide new data to validate/develop hydrodynamic models for coolability analysis of debris beds formed in fuel-coolant interactions during a postulated severe accident. The POMECO-FL test facility is employed to perform the experiment, with the spheres packed in a test section of 90 mm diameter and 635 mm height. The pressure drops are measured for air/water two-phase flow through the packed bed, and flow patterns are obtained by means of visual observations. Meanwhile, local void fraction in the center of the bed is measured by a microconductive probe. The experimental results show that the frictional pressure drop of single-phase flow through the bed can be predicted by the Ergun equation, if the area mean diameter of the particles is chosen in the calculation. Given the so-determined effective particle diameter, the estimation of the Reed model for two-phase flow pressure gradient in the bed has a good agreement with the experimental data. The characteristics of the local void fraction can be used to predict flow pattern and mean void fraction. It is observed that slug flow prevails when the mean void fraction is <0.5, whereas annular flow dominates after the mean void fraction is >0.7. If the effective particle diameter is further used as an influential parameter in flow pattern identification, the observed flow regimes of two-phase flow in porous media are well predicted by the existing flow pattern map.

Development of Heat Transfer Correlation for Supercritical Water in Vertical Upward Tubes

ABSTRACT Supercritical water is widely used in many advanced single-phase thermosiphons due to its favorable heat and mass transfer characteristics and potentially high thermal efficiency. However, the heat transfer characteristics of supercritical water in the deterioration regime cannot be accurately predicted due to the absence of exact evaluation of the effect on steep variation in thermophysical properties near the pseudocritical point. The present paper focuses on the deterioration mode by analyzing the physical mechanism and constructing a new correlation. About 3,000 experimental data on supercritical water, including 40 deteriorated heat transfer cases from open literature, were collected. Quantitative assessment of heat transfer behavior was conducted based on existing test data and previous criteria gathered from extant literature. Based on experimental data evaluation and phenomenological analysis, an improved dimensionless correlation is proposed by introducing multi-dimensionless parameters, which can correct the deviation of heat transfer from its conventional behavior in the Dittus-Boelter equation. Comparisons of various heat transfer correlations with the selected test data show that the new correlation agrees better with the test data versus other correlations selected from the open literature.

Validation of TRACE Code Against ROSA/LSTF Test for SBLOCA of Pressure Vessel Upper-Head Small Break

OECD/NEA ROSA/LSTF project tests are performed on the Large Scale Test Facility (LSTF). LSTF is a full-height, full-pressure and 1/48 volumetrically-scaled two-loop system which aims to simulate Ja ...

Experimental investigation on the dynamic characteristics of molten droplets and high‐temperature particles falling in coolant

This paper presents the dynamic characteristics of molten droplets and hot particles at the very beginning of their falling into coolant pools, which are of importance to the subsequent interactions such as fragmentation of the droplets in coolants. The falling course of a single droplet or a single hot particle was recorded by a high‐speed camera and a curve of velocity vs. time was obtained. Emphasis was placed on the effects of the droplet’s size and temperature, the coolant’s temperature and properties, and the droplet’s physical properties on the moving behavior. Tests with hot particles were also performed for a comparison with the droplets. The results for the all cases showed that the velocity of a falling droplet/particle decreased rapidly but rebounded shortly, at the beginning of droplet/particle falling in the coolant. Following such a V‐shaped evolution in velocity, the droplet/particle slows down gradually till a comparatively steady velocity. An increase in either coolant temperature or dro...