Nucleation Processes in Large Scale Vapor Explosions

1979 ◽  
Vol 101 (2) ◽  
pp. 280-287 ◽  
Author(s):  
R. E. Henry ◽  
H. K. Fauske
Keyword(s):  
Large Scale ◽  
Interface Temperature ◽  
Liquid Droplets ◽  
Contact Interface ◽  
Vapor Cavity ◽  
Spontaneous Nucleation ◽  
System Pressure ◽  
Nucleation Model ◽  
Vapor Explosions ◽  
Cold Liquid

A spontaneous nucleation model is proposed for the mechanisms which lead to explosive boiling in the free contacting mode. The model considers that spontaneous nucleation cannot occur until the thermal boundary layer is sufficiently thick to support a critical size vapor cavity, and that significant bubble growth requires an established pressure gradient in the cold liquid. This results in a prediction that, for an interface temperature above the spontaneous nucleation limit, large cold liquid droplets will remain in film boiling due to coalescence of vapor nuclei, whereas smaller droplets will be captured by the hot liquid surface and rapidly vaporize, which agrees with the experimental observations. The model also predicts that explosions are eliminated by an elevated system pressure or a supercritical contact interface temperature, and this is also in agreement with experimental data.

Study of Large-Scale Vapor Explosions in Interaction of Fusible Metals with Water

2001 ◽  
Vol 32 (7-8) ◽  
pp. 7
Author(s):  
G. A. Kapinos ◽  
Yu. P. Meleshko ◽  
V. I. Nalivaev ◽  
O. V. Remizov ◽  
S. R. Kharitonov
Keyword(s):  
Large Scale ◽  
Vapor Explosions

Investigation of the Role of Droplet Transport in Mitigating Top of the Line Corrosion

CORROSION ◽  
10.5006/2764 ◽  
2018 ◽  
Vol 74 (8) ◽  
pp. 873-885
Author(s):  
Nicolas Jauseau ◽  
Fernando Farelas ◽  
Marc Singer ◽  
Srdjan Nešić
Keyword(s):  
Large Scale ◽  
Flow Region ◽  
Limited Range ◽  
Operating Conditions ◽  
Experimental Methodology ◽  
Liquid Droplets ◽  
Flow Loop ◽  
Droplet Entrainment ◽  
Droplet Transport ◽  
Large Scale Flow

The entrainment of liquid droplets, occurring in a limited range of gas and liquid flow conditions within the stratified flow region, could represent an effective way to transport a non-volatile liquid corrosion inhibitor through the gas phase and combat top of the line corrosion (TLC). However, such an approach is only viable if the inhibitor can reach the top of the pipe and deposit at a rate higher than the local rate of condensing water can dilute it. This work presents a combined modeling and experimental methodology to determine the onset of droplet entrainment from the bottom and deposition at the top of the line. A modeling approach predicting the droplet entrainment onset is proposed and validated against new multiphase flow data recorded in a large scale flow loop, at operating conditions similar to those encountered in gas-condensate production facilities. Additionally, TLC experiments were performed in the same flow loop under simulated water condensation conditions to measure the actual corrosion at different rates of inhibiting droplet deposition. The results confirm that the droplet entrainment/deposition can effectively mitigate TLC when operating parameters are accurately controlled.

Explicit Finite Element Models of Friction Dampers in Forced Response Analysis of Bladed Discs

2007 ◽  
Author(s):  
E. P. Petrov
Keyword(s):  
Finite Element ◽  
Large Scale ◽  
Dynamic Properties ◽  
Forced Response ◽  
Response Analysis ◽  
Contact Interactions ◽  
Contact Interface ◽  
Explicit Finite Element ◽  
Friction Dampers ◽  
Time Dynamic

A generic method for analysis of nonlinear forced response for bladed discs with friction dampers of different design has been developed. The method uses explicit finite element modelling of dampers, which allows accurate description of flexibility and, for the first time, dynamic properties of dampers of different design in multiharmonic analysis of bladed discs. Large-scale finite element damper and bladed disc models containing 104–106 DOFs can be used. These models, together with detailed description of contact interactions over contact interface areas, allow for any level of refinement required for modelling of elastic damper bodies and for modelling of friction contact interactions. Numerical studies of realistic bladed discs have been performed with three different types of underplatform dampers: (i) a ‘cottage-roof’ (called also ‘wedge’) damper; (ii) seal wire damper; and (iii) a strip damper. Effects of contact interface parameters and excitation levels on damping properties of the dampers and forced response are extensively explored.

Vapor Bubble Condensation Characteristics of Subcooled Flow Boiling in Vertical Rectangular Channel

2012 ◽  
Author(s):  
Zhi-wei Tan ◽  
Liang-ming Pan
Keyword(s):  
Bubble Size ◽  
Vapor Bubble ◽  
Large Scale ◽  
Flow Boiling ◽  
Rectangular Channel ◽  
Size Variation ◽  
Transfer Model ◽  
Bubble Deformation ◽  
Initial Diameter ◽  
System Pressure

In this study, the behavior of condensing single vapor bubble in subcooled boiling flow within two different vertical rectangular channels has been numerically investigated by using the VOF (Volume of Fluid) multiphase flow model. The mass and energy transfer model of bubble condensing process induced from the interfacial heat transfer was proposed to describe the interfacial transportation between the two phases. The results of VOF simulations showed good agreements with previous experimental data in the bubble size variation and lifetime. The bubble lifetime was almost proportional to bubble initial size and prolonged by system pressure. With the increase of subcooling, the bubble lifetime reduces significantly, and the effect of mass flux could be negligible. When bubble size increased, the bubble shape tends to be changed in a large-scale channel. The VOF simulation results of deformation have good agreement with those of Kamei’ experiment and the results of MPS (Moving Particle Semi-implicit) simulation in the large-scale channel. Furthermore, the initial bubble size, subcooling of liquid and system pressure play an important role to influence the bubble deformation behaviors significantly. The bubble could deform sharper with the increase of subcooling and initial diameter, or could breakup when the subcooling and the initial diameter reached a certain value at the last bubble stage. Whereas the trend of bubble deformation would be weaken with the increase of system pressure.

Method for Direct Parametric Analysis of Nonlinear Forced Response of Bladed Discs With Friction Contact Interfaces

2004 ◽  
Author(s):  
E. P. Petrov
Keyword(s):  
Parametric Analysis ◽  
Large Scale ◽  
Normal Load ◽  
Forced Response ◽  
Finite Element Models ◽  
Contact Interface ◽  
Friction Contact ◽  
Interface Parameters ◽  
First Time ◽  
Contact Parameters

An effective method for direct parametric analysis of periodic nonlinear forced response of bladed discs with friction contact interfaces has been developed. The method allows, for the first time, forced response levels to be calculated directly as a function of contact interface parameters such as the friction coefficient, contact surface stiffness (normal and tangential coefficients), clearances, interferences, and the normal stresses at the contact interfaces. The method is based on exact expressions for sensitivities of the multiharmonic interaction forces with respect to variation of all parameters of the friction contact interfaces. These novel expressions are derived in the paper for a friction contact model, accounting for the normal load variation and the possibility of separation-contact transitions. Numerical analysis of effects of the contact parameters on forced response levels has been performed using large-scale finite element models of a practical bladed turbine disc with underplatform dampers and with shroud contacts.

Numerical Investigation of Heat Transfer in Wet Steam Flow in Convergent-Divergent Nozzles

2013 ◽  
Author(s):  
Navid Sharifi ◽  
Majid Sharifi
Keyword(s):  
Experimental Data ◽  
Thermodynamic Properties ◽  
Steam Turbine ◽  
Pressure Ratio ◽  
Relevant Literature ◽  
Flow Analysis ◽  
Numerical Procedure ◽  
Liquid Droplets ◽  
Wet Steam ◽  
Spontaneous Nucleation

Nucleation and condensation phenomena are of fundamental importance in many fields such as steam-turbine design and power generation technologies. Wet steam flows are typically considered as multiphase gas droplet mixtures in which both vapor and liquid droplets coexist. In such flows, spontaneous nucleation leads to the formation of liquid droplets from vapor. Our key goal is to determine the rate of nucleation and droplets growth correctly. This will enable us to predict the variations of thermodynamic properties along the nozzle axis. In this study, a CFD code is generated based on the assumption of non-isothermal homogenous nucleation rate. A “Used-Defined Function” (UDF) was written in a compatible format with FLUENT solver such that it implements all the required wet steam calculations through a finite-volume method. The predicted numerical results were well supported by experimental data from literature for a specific nozzle. The predicted distribution of pressure ratio along the main axis of the nozzle shows a reasonable agreement with experimental data. Moreover, the droplets sizes predicted were in good agreement with experimental data too. Besides, the variations of some important thermodynamic properties along the nozzles were determined as well. The predicted results were compared to available data from relevant literature. The outcome of current numerical procedure confirms the superiority of this module for wet steam considerations in supersonic flow. It can further be applied to wet flow analysis in so many applications such as steam turbine cascades.

Method for Direct Parametric Analysis of Nonlinear Forced Response of Bladed Disks With Friction Contact Interfaces

2004 ◽  
Vol 126 (4) ◽  
pp. 654-662 ◽  
Author(s):  
E. P. Petrov
Keyword(s):  
Parametric Analysis ◽  
Large Scale ◽  
Normal Load ◽  
Forced Response ◽  
Finite Element Models ◽  
Contact Interface ◽  
Friction Contact ◽  
Bladed Disks ◽  
Interface Parameters ◽  
Contact Parameters

An effective method for direct parametric analysis of periodic nonlinear forced response of bladed disks with friction contact interfaces has been developed. The method allows, forced response levels to be calculated directly as a function of contact interface parameters such as the friction coefficient, contact surface stiffness (normal and tangential coefficients), clearances, interferences, and the normal stresses at the contact interfaces. The method is based on exact expressions for sensitivities of the multiharmonic interaction forces with respect to variation of all parameters of the friction contact interfaces. These novel expressions are derived in the paper for a friction contact model, accounting for the normal load variation and the possibility of separation-contact transitions. Numerical analysis of effects of the contact parameters on forced response levels has been performed using large-scale finite element models of a practical bladed turbine disk with underplatform dampers and with shroud contacts.

Finite Element Modeling of a Microdroplet Generator With Integrated Sensing

2011 ◽  
Author(s):  
William S. Rone ◽  
Pinhas Ben-Tzvi
Keyword(s):  
Finite Element ◽  
Large Scale ◽  
Open Loop ◽  
Liquid Droplets ◽  
Gas Reservoir ◽  
Element Simulation ◽  
Droplet Liquid ◽  
Pressure Changes ◽  
Dominant Paradigm ◽  
Compressible Gas

This paper describes the analysis of a novel microdroplet generator’s integrated sensing capability using finite element simulation. The dominant paradigm for utilizing droplet generation is with either open-loop or externally-sensed closed-loop methods, each with significant disadvantages in terms of reliability and large-scale implementation, respectively. This work utilizes a system designed with a compressible gas reservoir adjacent to the incompressible droplet liquid reservoir. The compressible gas pressure changes as liquid droplets are dispensed from the constant volume fluid reservoir. This change was found to be linearly dependent on the size of the droplet that was ejected, validating this gas reservoir pressure as a useful means of indirectly measuring droplet size internally within the system.

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