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Bubble Sizing of Two-Phase Flow using A-B-Polar Scan Mode by Ultrasonic Reflection Coefficients
Kil-Mo KOO(구길모),In-Cheol Chu(주인철),Nam-Hyun Choi(최남현),Chul-Hwa SONG(송철화),Won-Pil BAEK(백원필) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11
In this paper, a preliminary examination for a bubble sizing technique shows that a bubble of a two-phase flow can be measured by a quantitative method using patterns of an ultrasonic reflection coefficient on a single channel mode between parameters of an ultrasonic transducer and reflection coefficients of a bubble shape. In that experiment, we also have established a PC-based UT special mode system through analysis of ultrasonic measurement principles and a basic reflection theory for a bubble sizing which can be shown A-BPolar scan mode. This system will be used to study the applications of ultrasonic semi-tomographic techniques having 8 channels as a robust non-invasive tool for direct analysis of the characteristics of multiphase flows.
수평 수조비등시 기포성장과 미세액막층 거동의 동시 관찰
주인철(In-Cheol Chu),송철화(Chul-Hwa Song) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11
The bubble growth rate and microlayer behavior were simultaneously visualized for an isolated boiling regime of saturated water by using a shadow graph and a total reflection technique, respectively. The increase rate of the bubble volume dropped sharply when the microlayer was totally depleted. However, the contribution of the superheated liquid layer evaporation to the bubble volume increase was comparable to or even higher than that of the microlayer evaporation during the time when the microlayer evaporation was active. The total contribution the macrolayer evaporation to the whole process of the bubble growth was about 70%, and the rest of the bubble growth was due to the inertia of the pressure potential and the microlayer evaporation. The bubble growth due to the microlayer evaporation was closely related to the area of the microlyaer underneath the bubble and showed the same tendency with the area of the microlyaer.
물-공기 횡류시 U 자형 튜브 다발에서의 유체탄성불안정
주인철(In-Cheol Chu),정흥준(Heung June Chung),이창희(Chang Hee Lee),윤영중(Young Jung Yun),정한섭(Han-Sub Chung),변형현(Hyung Hyun Byun),김무용(Moo Yong Kim),문효익(Hyo Ik Moon),이희남(Hui Nam Rhee) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.11
In the present study, a series of experiments have been performed to investigate a fluid-elastic instability of an U-tube bundle in air-water two-phase cross-flow. A total of 39 prototypic U-bend tubes are arranged in a rotated square array with a p/d of 1.633, which is identical to U-bend tube bundle of OPR1000 steam generators. The present experimental facility has 2-span U-tubes in contrast to 9-span U-tubes of OPR1000 steam generators. However, modal analysis shows that the major vibration mode and corresponding natural frequencies are almost same to the full 9-span U-tubes. A total of 12 3-axis acceleromters are installed inside U-tubes to monitor a precise vibration motions. The following parameters were obtained throughout a series of experiments: tube vibration responses and critical velocity for fluid-elastic instability, two-phase damping ratio, hydrodynamic mass. Finally, the instability factor (K) of Connors’ relation was evaluated based on the above measured parameters.
Performance Improvement and Validation of Advanced Safety Injection Tanks
윤영중,주인철,권태순,송철화,Youn, Young Jung,Chu, In-Cheol,Kwon, Tae-Soon,Song, Chul-Hwa Korean Society of Pressure Vessels and Piping 2011 한국압력기기공학회 논문집 Vol.7 No.1
Advanced SITs of the evolutionary PWRs have the advantage that they can passively control the ECC water discharge flow rate. Thus, the LPSI pumps can be eliminated from the safety injection system owing to the benefit of the advanced SITs. In the present study, a passive sealing plate was designed in order to overcome the shortcoming of the advanced SITs, i.e., the early nitrogen discharge through the stand pipe. The operating principle of the sealing plate depends only on the natural phenomena of buoyancy and gravity. The performance of the sealing plate was evaluated using the VAPER test facility, equipped with a full-scale SIT. It was verified that the passive sealing plate effectively prevented the air discharge during the entire duration of the ECC water discharge. Also, the major performance parameters of the advanced SIT were not changed with the installation of the sealing plate.
장석규(Seok-Kyu Chang),주인철(In-Cheol Chu),송철화(Chul-Hwa Song) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11
For the development of the constitutive relations in the interfacial area transport equations, adiabatic air-water two-phase flow experiments were conducted on a 4x4 rod bundle array. A squared center subchannel was chosen for the measurement of a total 1,321 points in a full subchannel, and the axial location of measured section was placed at 44D<SUB>H</SUB> from the inlet of the bundle array. Bundle array was consisted of 16 rods with a diameter of 25.4 ㎜, a rod to rod pitch of 33.7 ㎜ and the subchannel hydraulic diameter, D<SUB>H</SUB> of 31.5 ㎜. A double-sensor optical probe with the automatic controlled traverse system was used for the measurement of flow parameters such as local void fraction, interfacial velocity, Sauter mean diameter and interfacial area concentration in a subchannel. Three data sets were acquired consisting of void fractions, about 0.05, 0.10 and 0.20 at a superficial liquid velocity, 1.60 ㎧. The detailed profiles of two-phase flow parameters in a subchannel were obtained and the phase distribution patterns according to the bubble conditions were discussed.
CFD Modeling of Two-Phase Flows using Interfacial Area Transport Equation
Nguyen Van-Thai(우옌반타이),Song Chul-Hwa(송철화),Bae Byoung-Uhn(배병언),Chu In-Cheol(주인철),Euh Dong-Jin(어동진) 대한기계학회 2012 대한기계학회 춘추학술대회 Vol.2012 No.11
The application of one-group and two-group interfacial area transport equations (IATE) coupled with the computational fluid dynamics (CFD) solver to describe the temporal and spatial evolution of the two-phase geometrical structure is presented. Available mechanistic models of interfacial area sink and source terms in open literatures as well as our newly developed models are assessed with the CFD EAGLE code. Numerical predictions of the models are evaluated against experimental data of the VAWL facility for vertical-upward air-water pipe flow with an inner diameter of 80 ㎜. Better agreement between measured and predicted distributions of void fraction, interfacial area concentration (IAC) and bubble diameter is achieved with our models.