Modeling of Flashing Two-Phase Flow

Abstract

A review of the published work on the flashing of a two-phase flow system, owing to a sudden depressurization of a compressed liquid, is presented. Of concern is the two-phase flow transient occurring during a failure of a pressurized tube or vessel-blowdown. Abrupt depressurization of a confined liquid can bring the liquid to a superheated state. If this occurs, an intense nucleation process is triggered. The level of superheating at which the nucleation process begins is referred to as the "flashing inception" point. The rapidity of the bubble nucleation and growth processes substantial influence the mixture blowdown scenario that sometimes can be in the form of a Boiling Expanding Vapor Explosion (BLEVE).The current review deals with flashing of a single pure substance. First, the models of bubble formation and growth are presented. This is followed by a description on the incorporation of these models into two-phase flow transport models. The two-phase models are used for analysis of the blowdown scenario. This subject is of critical importance for the investigation of the safety of compressed liquid systems.

Solid–fluid phase transitions under extreme pressures including negative ones

“…This explosive fragmentation is very similar to the sudden, explosive boiling of liquids close to the mechanical spinodal (i.e. during homogeneous nucleation under very high metastability), also called sometimes spall [41,42]. The spallation strength for a solid is the strain needed to separate the material along a plane surface instantaneously.…”

Evaluation of Interfacial Heat Transfer Models for Flashing Flow with Two-Fluid CFD

“…In the nuclear industry, during the hypothetical loss of coolant accident of pressurized water nuclear reactors, the rate of coolant loss is determined by the critical flashing flow through the crack [2]. In the chemical industry, the severity of failure of pressurized vessels or pipes containing liquefied chemical hazardous gases is characterized by the external flashing flow [3]. An additional flashing evaporation phenomenon was reported in [4], which refers to an aerospace application and concerns the leading edge cooling of a space vehicle.…”

“…The complexity of flashing flows is represented by gas-liquid mixture with rapid phase change and bubble dynamics [5], and numerical studies are directed towards the determination of vapour generation rate. Good reviews have been given by Pinhasi [3] and Liao & Lucas [6]. In general, two methods have been used for the evaluation of the interfacial mass transfer rate in flashing flows.…”

Estimation of the Thermodynamic Limit of Overheating for Bulk Water from Interfacial Properties

“…The phenomenon constitutes an operational hazard for equipment containing heated pressurized liquids: after a sudden accidental pressure loss or temperature increase, the liquid might reach a deeply metastable state and then relax by explosive boiling. LOCA (Loss of Coolant Accident) in pressurized water nuclear reactors [6] and BLEVE (Boiling Liquid Expanding Vapor Explosion, [7,8]) in pressurized (liquified) gas tanks are two well known examples for violent and sudden boiling and the cause of many accidents. To minimize the risk of accidents, scientists and engineers dealing with pressurized heated liquids should be aware of the metastable region and know the properties of liquids in it.…”