Measurements of interfacial area concentration in two-phase bubbly flow

Conference · Wed Dec 31 04:00:00 EST 1997

OSTI ID:296640

Wu, Q; Kim, S; McCreary, D; Ishii, M ^[1]; Beus, S G ^[2]

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1. Purdue Univ., West Lafayette, IN (United States)
2. Bettis Atomic Power Lab., West Mifflin, PA (United States)

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.

• Research Organization: Bettis Atomic Power Lab., West Mifflin, PA (United States)
• Sponsoring Organization: USDOE Assistant Secretary for Nuclear Energy, Washington, DC (United States)
• DOE Contract Number: AC11-93PN38195
• OSTI ID: 296640
• Report Number(s): WAPD-T--3178; CONF-971125--; ON: DE99000477
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
BUBBLES
EQUATIONS
EVALUATION
FLOW MODELS
INTERFACES
TWO-PHASE FLOW