Author: Isao KataokaPublisher:
ISBN:
Category : Fluid mechanics
Languages : en
Pages : 58
Book Description
Local Formulation of Interfacial Area Concentration and Its Measurements in Two-phase Flow
Author: Isao KataokaPublisher:
ISBN:
Category : Fluid mechanics
Languages : en
Pages : 58
Book Description
Measurements of Interfacial Area Concentration in Two-phase Bubbly Flow
Author: Publisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
Interfacial area concentration is an important parameter in the two-fluid model for two-phase flow analysis, which is defined as the total interface area per unit mixture volume and has the following local time-averaged expression:[bar a][sup t]= 1/[Delta]T[Sigma][sub j](1/[vert-bar]V[sub i][center-dot] n[sub i][vert-bar])[sub j], where j denotes the j-th interface that passes the point of interest in a time interval[Delta]T. V[sub i] and n[sub i] refer to the bubble interface velocity and surface normal vector, respectively. To measure this parameter, the double-sensor probe technique is commonly used. Due to the influences of the bubble lateral motions, however, the measurement results should be interpreted via a certain statistic approach. Recently, to take into account the effects of the probe spacing, Wu and Ishii provided the following new formula to correlate the measurable values to the interfacial area concentration:[bar a][sub i][sup t]= 2N[sub b]/[Delta]T ([Delta][bar t]/[Delta]s)[2+ (1.2[sigma][sub[Delta]t]/[Delta][bar t])[sup 2.25]], for D= 1.2[approximately] 2.8[Delta]s, where N[sub b] refers to the number of the bubbles that hit the probe front tip during time interval[Delta]T, [Delta]s denotes the distance between the two probe tips, D is the bubble diameter, [Delta][bar t] represents the measured average time interval for an interface to travel through the two probe tips, and[sigma][sub[Delta]t] is the standard deviation of[Delta]t. The theoretical accuracy of this formula is within[+-] 5% if the sample size is sufficiently large. The purpose of this study is to evaluate this method experimentally using an image processing method.
Measurements of Interfacial Area Concentration in Two-phase Flow with Two-point Conductivity Probe. Brief Communication
Author: Publisher:
ISBN:
Category :
Languages : en
Pages : 16
Book Description
Kataoka, Ishii and Serizawa analyzed the measurements of the local time-averaged interfacial area concentration in two-phase flow with a two-point conductivity probe. They considered the influence of the bubble velocity fluctuation on the measurement and directly transferred the mathematics concept of the local time-averaged interfacial area concentration into the measurable parameters. In the end of the derivation, however, the expression of the interfacial area concentration was inappropriate due to the over-simplification to the integration limits of the probability distributions. Consequently, the resultant interfacial area concentration may be significantly lower than the actual value. Since the formula is very important for the interpretation of experimental data, we feel it is necessary to provide a correction to the original work.
Measurement of Interfacial Area and Void Fraction by Two-phase Flow in a Vertical Tube
Author: Julio M.* DejesusTwo-Phase Flows
Author: Shih-i PaiPublisher: Springer-Verlag
ISBN: 3322863484
Category : Science
Languages : de
Pages : 373
Book Description
The role of interfacial area in two-phase flow in porous media
Author: Jennifer NiessnerPublisher: Sudwestdeutscher Verlag Fur Hochschulschriften AG
ISBN: 9783838127781
Category :
Languages : de
Pages : 268
Book Description
Understanding and predicting porous media flow is of central importance for investigating a tremendous number of physical systems, such as groundwater flow, transport of contaminants in the subsurface, CO2 storage, flow in fuel cells and hygiene products, or to improve the treatment of brain tumors. Classically, the involved processes are described partly empirically, partly physically-based which leads to a number of well-known problems and discrepancies in the classical porous medium flow model. Therefore, an alternative and physically-based two-phase flow model is proposed in this book.Besides an introduction into the classical porous medium flow models, this book introduces a new and physically-based alternative. After a short description of the numerics, a large number of simulation examples is presented and thoroughly discussed. An outlook is given on how this model can be transferred to a multi-scale multi-physics context.
Interfacial Area and Interfacial Transfer in Two-phase Flow
Author: Publisher:
ISBN:
Category :
Languages : en
Pages : 48
Book Description
A joint research program funded by the DOE/BES at Purdue University and the University of Wisconsin-Milwaukee has been underway. The main efforts of the Purdue program were concentrated on the following tasks. Development of Four Sensor Measurement Method; Experimental Study of Axial Changes of Transverse Void and Interfacial Area Profiles in Bubbly Flow; Modeling of the Probe-Particle Interaction Using Monte Carlo Numerical Simulation; and Experimental Study of the Stability of Interface of Very Large Bubbles. Highlights of these research results are reported.
Internal Structure and Interfacial Area in Two-phase Flow Systems
Author: Publisher:
ISBN:
Category :
Languages : en
Pages : 121
Book Description
The interfacial transfer terms and the importance of the interfacial area concentration are reviewed first with respect to the two-fluid model formulation of two-phase flow systems. Then the available measurement techniques for interfacial area are reviewed. At present, it appears that various methods such as the chemical, light attenuation, photographic, ultrasound attenuation and probe techniques have a number of limitations. Among these measurement techniques, however, the local probe method using one or more double sensors seems to have the greatest potential in terns of accuracy and wider applicability in various two-phase flow patterns. From the brief review of existing interfacial area modeling methods, it is concluded that the conventional approaches might not be sufficient, and new directions are indicated. Recent experimental results on local interfacial structural characteristics of horizontal bubbly two-phase flow and internal flow structure development are presented. More specifically, experimental results on local void fraction, interfacial area concentration, bubble size, bubble interface velocity and bubble frequency are documented in detail. Finally, a theoretical model predicting the mean bubble size and interfacial area concentration is proposed. The theoretically predicted bubble size and interfacial area concentration are found to agree reasonably well with those measured by using a double-sensor resistivity technique.
Interfacial Area and Two-phase Flow Structure Development Measured by a Double-sensor Probe
Author: Publisher:
ISBN:
Category :
Languages : en
Pages : 126
Book Description
In this report, we studied the local phasic characters of dispersed flow regime both at the entrance and at the fully developed regions. Since the dispersed phase is distributed randomly in the medium and enclosed in relatively small interfaces, the phasic measurement becomes difficult to obtain. Local probe must be made with a miniaturized sensor in order to reduce the interface distortion. The double-sensor resistivity probe has been widely used in local void fraction and interface velocity measurements because the are small in comparison with the interfaces. It has been tested and proved to be an accurate local phasic measurement tool. In these experiments, a double-sensor probe was employed to measure the local void fraction and interface velocity in an air-water system. The test section was flow regime can be determined by visualization. Furthermore, local phasic measurements can be verified by photographic studies. We concentrated our study on the bubbly flow regime only. The local measurements were conducted at two axial locations, L/D = 8 and 60, in which the first measurement represents the entrance region where the flow develops, and the second measurement represents the fully developed flow region where the radial profile does not change as the flow moves along the axial direction. Four liquid flow rates were chosen in combination with four different gas injection rates. The superficial liquid velocities were j{sub t} = 1.0, 0.6,0.4, and 0.1 m/s and superficial gas velocities were j{sub g} = 0.0965, 0.0696, 0.0384, and 0.0192 m/s. These combinations put the two-phase flow well in the bubbly flow regime. In this sequence of phenomenological studies, the local void fraction, interface area concentration, sauter mean diameter, bubble velocity and bubble frequency were measured.
Author: Seungjin Kim