Analytical expression for the evolution of interfacial area density between transformed grains during nucleation and growth transformations

2006 ◽  
Vol 54 (8) ◽  
pp. 1509-1513 ◽  
Author(s):  
P.R. Rios ◽  
R.B. Godiksen ◽  
S. Schmidt ◽  
D. Juul Jensen ◽  
R.A. Vandermeer
Keyword(s):  
Interfacial Area ◽  
Nucleation And Growth ◽  
Area Density ◽  
Analytical Expression ◽  
Interfacial Area Density

scholarly journals Effect of Pressure With Wall Heating in Annular Two-Phase Flow

2003 ◽  
Vol 125 (1) ◽  
pp. 84-96 ◽  
Author(s):  
Ranganathan Kumar ◽  
Thomas A. Trabold
Keyword(s):  
Aspect Ratio ◽  
Void Fraction ◽  
High Aspect Ratio ◽  
Test Section ◽  
Full Range ◽  
Interfacial Area ◽  
Two Phase ◽  
Local Flow ◽  
Area Density ◽  
Interfacial Area Density

The local distributions of void fraction, interfacial frequency, and velocity have been measured in annular flow of R-134a through a wall-heated, high aspect ratio duct. High aspect ratio ducts provide superior optical access to tubes or irregular geometries. This work expands upon earlier experiments conducted with adiabatic flows in the same test section. Use of thin, transparent heater films on quartz windows provided sufficient electrical power capacity to produce the full range of two-phase conditions of interest. With wall vapor generation, the system pressure was varied from 0.9 to 2.4 MPa, thus allowing the investigation of flows with liquid-to-vapor density ratios covering the range of about 7 to 27, far less than studied in air-water and similar systems. There is evidence that for a given cross-sectional average void fraction, the local phase distributions can be different depending on whether the vapor phase is generated at the wall, or upstream of the test section inlet. In wall-heated flows, local void fraction profiles measured across both the wide and narrow test section dimensions illustrate the profound effect that pressure has on the local flow structure; notably, increasing pressure appears to thin the wall-bounded liquid films and redistribute liquid toward the edges of the test section. This general trend is also manifested in the distributions of mean droplet diameter and interfacial area density, which are inferred from local measurements of void fraction, droplet frequency and velocity. At high pressure, the interfacial area density is increased due to the significant enhancement in droplet concentration.

scholarly journals A Nonequilibrium Vapor Generation Model for Flashing Flows

1984 ◽  
Vol 106 (1) ◽  
pp. 198-203 ◽  
Author(s):  
P. Saha ◽  
N. Abuaf ◽  
B. J. C. Wu
Keyword(s):  
Flow Regime ◽  
Bubbly Flow ◽  
Interfacial Area ◽  
Superheated Liquid ◽  
Generation Model ◽  
Vapor Generation ◽  
Area Density ◽  
Interfacial Area Density ◽  
Inception Point ◽  
Liquid Superheat

A nonequilibrium vapor generation model for flashing flows is presented. The model consists of a flashing inception point, a bubbly flow regime followed by a bubbly-slug regime, an annular or annular-mist regime, and finally a dispersed-droplet regime. Existence of superheated liquid at the inception point and beyond is recognized. The vapor generation rate is calculated from the flow-regime dependent interfacial area density and net interfacial heat flux. However, the bubble number density at the flashing inception point was varied to obtain optimum fits with the void fraction data taken in a vertical converging-diverging nozzle. The interfacial area density at the inception point, thus determined, showed a rapid increase with the decrease in the liquid superheat at that point. This trend is plausible, since in the limit of thermal equilibrium flow where the liquid superheat approaches zero, the interfacial area for heat and mass transfer should be very large.

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