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미포화 비등 유동에 대한 Bubble lift-off model 개발 및 1군 계면면적 수송방정식 해석
배병언(B.U. Bae),윤병조(B.J. Yun),윤한영(H.Y. Yoon),송철화(C.H. Song),박군철(G.C. Park) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5
The interfacial area transport equation for the subcooled boiling flow was developed with a mechanistic model for the wall boiling source term. It included the bubble lift-off diameter model and lift-off frequency reduction factor model. Those models took into account the bubble's sliding on the heated wall after a departure from the nucleate site and the coalescences of sliding bubbles. To implement the model, the two-phase flow CFD code was developed, which was named as EAGLE (Elaborated Analysis of Gas-Liquid Evolution). The developed model and EAGLE code was validated the experimental data of SUBO (Subcooled Boiling) facility. The computational analysis revealed that the interfacial area transport equation with the bubble lift-off diameter model agreed well with the experimental results. It presents that the source term for the wall nucleation enhanced the prediction capability for a multi-dimensional behavior of void fraction or interfacial area concentration.
미포화 비등 이상유동 내 국소 기포 인자에 대한 실험적 연구
배병언(B.U. Bae),윤병조(B.J. Yun),박원만(W.M. Park),송철화(C.H. Song),박군철(G.C. Park) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5
Subcooled boiling test was carried out in the SUBO (Subcooled boiling) test facility to extend a database for a code benchmark. The test section is a vertical annulus with a heater rod at the channel center. For the measurement of local bubble parameters, double optical fiber sensors were applied at the six elevations. Total six test matrixes are chosen for the parametric study of the heat flux, mass flux and inlet subcooling. Void fraction, interfacial area concentration and bubble velocity were measured at 12 radial locations at each elevation. The local bubble parameters show well the characteristics and propagation of a void fraction and an interfacial area concentration along the test section in the subcooled boiling flow. The present data will be suitable for the benchmark, verification and model development for the CFD style codes or existing safety analysis codes.
슬러그 유동 조건에서 국소 기포인자 측정을 위한4-센서 광섬유 프로브 개발
문정민,윤병조 한국유체기계학회 2018 한국유체기계학회 논문집 Vol.21 No.2
Bubble parameters such as void fraction, bubble velocity, and interfacial area concentration(IAC) are important for an accurate prediction of bubble behaviors in the two-phase flow. The 4-sensor probe method is one of the representative multi-sensor probe techniques which can measure the local bubble parameters regardless of bubble shape and bubble behavior. However, there is a lack of evaluation as to whether it is applicable to flow conditions in which distorted and slug bubbles appear. Therefore, in this study, the performance of 4-sensor probe was investigated with numerical simulations under the postulated flow conditions for various bubble shapes. It is found from the study that bubble parameters are measured more accurately as the radial distance between sensors is close. For the IAC, the method proposed by Revankar et al. showed the best accuracy. Also, in order to verify the design of the optimized 4-sensor optical fiber probe, verification experiment was performed in the air-water flow condition. It showed that the 4-sensor optical fiber probe(4S-OFP) measured the void fraction, bubble velocity, and IAC within 10 %, 8 %, and 22 % of deviations against visualization data, respectively.