Research on the effect of Reynolds correlation in natural convection film condensation

Film condensation is a vital phenomenon in the nuclear engineering applications,such as the gas-steam pressurizer design,and heat removing on containment in the case of postulated accident.Reynolds number in film condensation can be calculated from either the mass relation or the energy relation,but few researches have distinguished the difference between them at present.This paper studies the effect of Reynolds correlation in the natural convection film condensation on the outer tube.The general forms of the heat transfer coefficient correlation of film condensation are developed in different flow regimes.By simultaneously solving a set of the heat transfer coefficient correlations with Re_(mass) and Re_(energy),the general expressions for Re_(mass) and Re_(energy) and the relation between the corresponding heat transfer coefficients are obtained.In the laminar and wavefree flow regime,Re_(mass) and Re_(energy) are equivalent,while in the laminar and wavy flow regime,Re_(mass) is much smaller than Re_(energy),and the deviation of the corresponding average heat transfer coefficients is about 30% at the maximum.In the turbulent flow regime,the relation of Re_(mass) and Re_(energy)is greatly influenced by Prandtl number.The relative deviation of their average heat transfer coefficients is the nonlinear function of Reynolds number and Prandtl number.Compared with experimental results,the heat transfer coefficient calculated from Re_(energy) is more accurate.

Research on the steam–gas pressurizer model with Relap5 code

Steam–gas pressurizers are self-pressurizing, and since steam and noncondensable gas are used to sustain their pressure, they experience very complicated thermal–hydraulic phenomena owing to the presence of the latter. A steam–gas pressurizer model was developed using Relap5 code to investigate such a pressurizer's thermal–hydraulic characteristics.The important thermal–hydraulic processes occurring in the pressurizer model include bulk flashing, rainout, wall condensation with noncondensable gas, and interfacial heat and mass transfer. The pressurizer model was verified using results from insurge experiments performed at the Massachusetts Institute of Technology. It was found that noncondensable gas was one of the important factors governing the pressure response, and the accuracy of the developed model would change with different mass fractions and types of noncondensable gas.

Liutex-based analysis of drag force and vortex in two-phase flow past 2-D square obstacle using LBM on GPU

The two-phase flow past a square is a ubiquitous phenomenon widely encountered in industries and engineering,where the interaction of disparate phases coupled with the influence of the solid is rather complicated.In this context,the flow characteristics and the vortex field are investigated to reveal the mechanisms of the two-phase drag and the vortex variation.The lattice Boltzmann method(LBM)is utilized to study the multi-component two-phase flow.The computation implemented on the GPU is remarkably accelerated thanks to the natural parallelism of the LBM.The process of the two-phase flow past a square is thoroughly examined.The drag and lift forces,including the total force and the components caused by the dispersed phase and the continuous phase,respectively,are obtained,and their variation mechanisms are explained.Meanwhile,the vortex-identification approaches based on the Liutex as well as the traditional methods are compared.The relationship between the bubble breakup and coalescence processes and the extremums of different vortex identification variables is analyzed.