Initially sub-cooled liquid flashing flow CFD modeling: closure parameters for a non-symmetric interfacial area density formulation

Egoi Ortego Sampedro,Maroun Nemer

doi:10.1051/e3sconf/202132103010

Abstract

A bubble to droplet transition non-symmetric interfacial area density formulation was developed for flash boiling nozzles CFD modeling. This formulation is used in a two fluid Euler- Euler modeling with a thermal phase change model. The regime transition formulation is based on the number of bubbles density and number of droplet density values. The first affects mainly the flow regime close to the nozzle throat and the second parameter affects mainly the flow close to the outlet. The physical factors affecting the calibration values of these parameters are analyzed in this paper with the aim of defining appropriate closure models. The analysis is done using experimental data available in literature. The comparison is done on the mass flow rate and the nozzle outlet velocity. It appears that the number of bubbles density is related to the inlet sub -cooling conditions and that the number of droplets density is affected by the outlet pressure and Reynolds number.

Highlights

IntroductionFlash boiling nozzles are the motive elements of various energy conversion components such as twophase impulse turbines [1] or two-phase ejectors [2]
Flash boiling nozzles are the motive elements of various energy conversion components such as twophase impulse turbines [1] or two-phase ejectors [2].Both have been identified as key components for energy efficiency improvement in mechanical power and cold power production thermodynamic systems
The purpose of this paper is to present a model allowing the adjustment of the evaporative term close to the nozzle throat and close to the nozzle outlet independently

Summary

Introduction

Flash boiling nozzles are the motive elements of various energy conversion components such as twophase impulse turbines [1] or two-phase ejectors [2]. Both have been identified as key components for energy efficiency improvement in mechanical power and cold power production thermodynamic systems. The behavior of flash nozzles is strongly related to the evaporation regime during the expansion observed by the flow. This affects the critical flow rate and the pressure, void fraction and velocity profiles of the flow [3]. Models for the interfacial mass transfer term are specially investigated either for nuclear safety applications [4] or for CO2 two-phase ejectors [2]

Objectives

Results

Discussion

Conclusion