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- 주제어 : Subcooled boiling(미포화 비등) (검색결과 7 건)
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열분배모델을 이용한 수직유로에서의 저압 미포화비등 해석
이바로(Ba-Ro Lee),이연건(Yeon-Gun Lee) 대한기계학회 2016 大韓機械學會論文集B Vol.40 No.7
벽면비등 모델로 열분배모델을 채택하는 CFD 스케일의 전산해석코드는 저압 조건에서 미포화비등 발생 시 2상유동 변수의 해석 정확도가 낮은 것으로 알려진다. 본 연구에서는 열분배모델을 기반으로 벽면비등 현상을 예측하는 열수력 기기해석코드인 CUPID 코드를 이용하여 수직상향류 미포화비등 실험을 해석하였다. 10 bar 이상의 고압 조건에서는 CUPID 코드의 기포율 예측 정확도가 높았으나, 대기압 주변의 저압 조건에서는 기포율 분포에 대한 해석결과가 실험결과와 큰 차이를 보였다. 따라서 열분배모델 내 주요 인자에 사용되는 부모델에 대한 민감도 분석을 수행하였으며, 저압 조건 미포화비등 예측에 적합한 최적 부모델 조합을 선정하였다. 또한, 열분배모델 내 주요 인자 중 하나인 K-인자가 기포율에 미치는 영향을 평가하였다. Most CFD codes, that mainly adopt the heat partitioning model as the wall boiling model, have shown low accuracies in predicting the two-phase flow parameters of subcooled boiling phenomena under low pressure conditions. In this study, a number of subcooled boiling experiments in vertical channels were analyzed using a thermal-hydraulic component code, CUPID. The prediction of the void fraction distribution using the CUPID code agreed well with experimental data at high-pressure conditions; whereas at low-pressure conditions, the predicted void fraction deviated considerably from measured ones. Sensitivity tests were performed on the submodels for major parameters in the heat partitioning model to find the optimized sets of empirical correlations suitable for low-pressure subcooled flow boiling. The effect of the K-factor on the void fraction distribution was also evaluated.
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환형채널 내 저압 미포화비등 유동장의 국소 이상유동 변수 측정
이연건(Yeon-Gun Lee),유지웅(Ji-Woong Yoo),김신(Sin Kim) 대한기계학회 2018 大韓機械學會論文集B Vol.42 No.12
대기압 주변 저압조건에서 미포화비등 유동장 내 국소 기포인자를 측정하기 위한 실험 연구를 수행하였다. 시험부는 유효 가열길이 2 m의 수직 환형채널이며, 기포변수의 측정에 광섬유센서를 적용하였다. 네 군데의 높이에서 국소 기포율, 평균 기포속도, 계면면적밀도, Sauter mean diameter를 측정하였으며, 광섬유센서의 측정 팁을 이송함으로써 각 높이에서의 반경방향 단면 분포를 획득하였다. 실험에서 유동 조건은 열속 370 kW/m², 질량속 430~680 kg/m²s, 입구 과냉각도 12~18 K, 그리고 압력 114~152kPa의 범위로 조절하였다. 국소 기포인자의 다차원 분포 측정 결과는 전산유체역학 코드의 벽면 비등모델 검증에 유용하게 활용될 수 있다. In this study, an experimental investigation is performed to measure the local bubble parameters in steam-water subcooled boiling flow under atmospheric pressure conditions. The test section is a vertical concentric annulus with an effective height of 2 m, and optical fiber probes are used to measure various local bubble parameters during boiling of the subcooled flow. The local void fraction, mean bubble velocity, interfacial area density, and Sauter mean diameter are measured at four elevations, and their radial profiles are obtained by traversing the tip of optical probes. In the experiments, the flow conditions were set for a heat flux of 370 kW/m², a mass flux of 430~680 kg/m²s, and an inlet subcooling of 12~18 K at pressures ranging from 114 to 152 kPa.
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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.
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배병언(B.U. Bae),윤한영(H.Y. Yoon),어동진(D.J. Euh),송철화(C.H. Song),박군철(G.C. Park) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.5
For the analysis of a two-phase flow, the interaction between two phases such as the interfacial momentum or heat transfer is proportional to the interfacial area. So the interfacial area concentration (IAC) is one of the most important parameters governing the behavior of each phase. This study focuses on the development of a computational fluid dynamics (CFD) code for investigating a boiling flow with a one-group IAC transport equation. It was based on the two-fluid model and governing equations were calculated by SMAC algorithm. For checking the robustness of the developed code, the experiment of a subcooled boiling in a vertical annulus channel was analyzed to validate the capability of the IAC transport equation. As the results, the developed code was confirmed to have the capability in predicting multi-dimensional phenomena of vapor generation and propagation in a subcooled boiling.
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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.
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단일 수평관을 가지는 저장조 내의 이상 유동 열전달 계산
신병수(Byungsoo Shin),정애주(Ae Ju Cheong),장현섭(Hyun Sop Chang) 대한기계학회 2013 대한기계학회 춘추학술대회 Vol.2013 No.12
Generally, to predict overall heat transfer of heat exchanger including tube bundle, the study on the heat exchanger with a single tube should be preceded. The objective of this study is to calculate the heat flux and the heat transfer coefficient at the inside and outside of a heat exchanger tube using previous heat transfer correlations under a certain given condition. The different correlations were applied to calculation according to two phase flow pattern of horizontal flow inside a tube and the onset of nucleate boiling outside a tube. And the sensitivity study was conducted about the thermal hydraulic parameters near the outside of horizontal tube. Finally, the major effective parameters were investigated.
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