Scalability of Validation Data for Safety Evaluation of Water-cooled Nuclear Reactors

Chul-Hwa Song(송철화) 한국유체기계학회 2023 한국유체기계학회 학술대회 논문집 Vol.2023 No.7

피동적 유체기구의 유동 조절 특성에 관한 실험

서정식,송철화,조석,정문기,최영돈,Seo, Jeong-Sik,Song, Chul-Hwa,Cho, Seok,Chung, Moon-Ki,Choi, Young-Don 대한기계학회 2000 大韓機械學會論文集B Vol.24 No.3

A model testing has been performed to investigate the flow characteristics of a vortex chamber, which plays a role of a flow switch and passively controls the discharge flow rate. This method of passive flow control is a matter of concern in the design of advanced nuclear reactor systems as an alternative to the active flow control to provide emergency water to the reactor core in case of postulated accidents like LOCA (Loss-Of-Coolant Accident). By changing the inflow direction in the vortex chamber and varying the flow resistance inside the chamber, the vortex chamber can control passively the injection flowrate. Fundamental characteristics such as discharge flow rate and pressure drop of the vortex chamber are measured, and its parametric effects on the performance of the vortex chamber are also systematically investigated.

과냉각수조에서 증기응축 특성에 관한 실험적 연구

김환열,조석,송철화,정문기,최상민,Kim, Hwan-Yeol,Cho, Seok,Song, Chul-Hwa,Chung, Moon-Ki,Choi, Sang-Min 한국에너지학회 1999 에너지공학 Vol.8 No.2

과냉각수조로 분사되는 증기의 직접접촉 응축특성을 알아보기 위하여 다섯 개의 수평 노즐에 대해 증기 질량유량과 수조 온도를 여러 가지로 변화시키면서 실험적 연구를 수행하였다. 증기응축현상을 육안관찰과 고속 비디오 카메라를 사용한 방법으로 분석한 결과, 안정된 증기제트인 경우 증기 질량속과 수조온도가 변화함에 따라 타원형 및 원추형 증기제트 형상이 나타나는 것을 관찰하였다. 증기제트 팽창비, 증기제트 길이 및 응축연전달계수를 구하였고, 증기 질량속, 수조온도 및 노즐 내경이 미치는 영향을 분석하였다. 증기제트 길이와 응축열전달계수를 증기 질량속 및 응축추진 포텐셜의 함수로 나타낸 상관식을 구하였다. 증기제트 내부와 주위 수조온도 분포를 구했으며 증기 질량속, 수조온도 및 노즐 내경이 미치는 영향을 분석하였다. 처깅, 천이처깅, 응축진동, 안정응축, 방울응축진동 및 간헐진동응축 등 여섯 가지 영역으로 구분된 응축 영역도를 작성하였다. 그 외, 수조 벽면에서의 동압을 측정하였고, 증기 질량속과 수조온도에 따라 변화하는 증기 응축모드와 동압과는 밀접한 연관성이 있음을 확인하였다. Experimental study on characteristics of direct contact condensation of steam discharged into a sub-cooled water pool has been performed using five different sizes of horizontal nozzle over a wide range of steam mass fluxes and pool temperatures. Steam condensation phenomena have been observed visually and by taking pictures of steam jets using a high speed video camera. Two different steam jet shapes such as ellipsoidal shape and conical shape were typically observed for a stable steam jet, depending on the steam mass flux and pool temperature. The steam jet expansion ratio and the steam jet length as well as the condensation heat transfer coefficients were determined. The effect of steam mass flux, pool temperature, and nozzle diameter on these parameters were also discussed. Empirical correlations for the steam jet lengths and the condensation heat transfer coefficients as a function of steam mass flux and condensation driving potential were established. The axial and radial temperature distributions in steam jet and in surrounding water were measured. The effect of steam mass flux, pool temperature, and nozzle diameter were also discussed. The condensation regime map, which consists of six regimes such as chugging, transient chugging, condensation oscillation, stable condensation, bubble condensation oscillation, and intermittent oscillation condensation, were established. In addition, the dynamic pressures at the pool wall were measured. The close relation of dynamic pressure and steam condensation mode, which is also dependent on steam mass flux and pool temperature, was found.

수조내 I-Sparser의 증기제트 응축에 의한 열혼합 실험

김연식,전형길,송철화,Kim Yeon-Sik,Jun Hyeong-Gil,Song Chul-Hwa 한국에너지학회 2005 에너지공학 Vol.14 No.1

B&C(Blowdown and Condensation)장치를 이용하여 APR1400 실규모 I-Sparger의 증기제트 응축에 의한 수조내 열혼합 현상에 대한 실험이 수행되었다. 한정된 가압기 용량으로 인하여 과도상태 실험이 수행되었으며, 실험을 통해 수조내에 배치된 열전대를 사용하여 열혼합 자료를 얻었다. 측정된 열혼합 자료를 바탕으로 지역별 온도 변화의 경향과 수조 수직-단면상의 온도 윤곽도를 작성하였으며 이를 바탕으로 I-Sparger의 열혼합 특성을 파악하였다. 실험결과에서 I-Sparger에 의한 열혼합 특성은 I-Sparger 설계특성이 나타나는 열혼합 경향을 보이고 있음을 확인하였다. An experimental study on thermal mixing of steam jet condensation through the I-Sparger of APR1400 design using B&C (Blowdown and Condensation) test facility. Due to the limit of the steam supply capability of the pressurizer, transient thermal mixing experiments were conducted. Temperature distributions in the quench tank were measured using thermocouples located at various positions. From the experimental data, local temperature variations for various locations and vertically cross-sectional temperature distributions for several times were depicted and presented. The result shows the characteristics of thermal mixing of the I-Sparger depending on the design features of the I-Sparger.

Ultrasonic Image of the Side Drilled Holes in SS Reference Block as Combining Bases of Support for Spatial Frequency Response

Kil-Mo Koo(구길모),Chul-Hwa Song(송철화),Won-Pil Beak(백원필),Hee-Young Kang(강희영) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.11

In this paper, we have studied the images which have been reconstructed by using combination of images acquired by the variation of operating frequency. When inner images have been reconstructed, they have been superposed by the surface state effect. In this case, the images of the phase object can be enhanced by the contrast of inner images. There is a kind of specimen, one is a reference block having 1/4T, 1/2T, 3/4T side drilled holes as main run piping material of the steam generator in nuclear power plants. It has been shown that the two results of defect shapes have better than before in this processing and phase contrast grow about twice. And we have constructed the acoustic microscope by using a quadrature detector that enables to acquire the amplitude and phase of the reflected signal simultaneously. Further more we have studied the reconstruction method of the amplitude and phase images, the enhancement method of the defect images' contrast.

난류 에디크기를 고려한 접속시간 항 개선을 통한 기포 합체모델 개발

우옌반타이(Nguyen Van-Thai),송철화(Song Chul-Hwa),배병언(Bae Byoung-Uhn),어동진(Euh Dong-Jin) 대한기계학회 2012 대한기계학회 춘추학술대회 Vol.2012 No.5-3

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.

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.

대류방식을 이용한 열유속센서의 검정에 관한 연구

양훈철(Hooncheul Yang),송철화(Chul Hwa Song),김무환(Moo Hwan Kim) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.4

The objective of this work is to propose calibration facility in which a thin film type heat flux sensor can be calibrated under convective flow condition by using a small wind tunnel with the constant temperature plate condition. A small wind tunnel has been built to produce a boundary layer shear flow above a constant temperature copper plate. 12-independent copper blocks, thin film heaters, insulators and temperature controllers were used to keep the temperature of flat plate constant at a specified temperature. Three commercial thin film-type heat flux sensors were tested. Convective calibrations of these gages were performed over the available heat flux range of 1.4~2.5 ㎾/㎡. The uncertainty in the heat flux measurements in the convective-type heat flux calibration facility was ±2.07%. Non-dimensional sensitivity is proposed to compare the sensitivity calibrated by manufacturer and that of experiment conducted in this study.

고 질량유속 증기제트 방출시 과냉각수조 내의 열혼합 해석

강형석(Hyung Seok Kang),송철화(Chul Hwa Song) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.6

A CFD benchmak calculation for a thermal mixing test was performed for 30 seconds to develop the methodology analysis for the thermal mixing between steam and subcooled water. In the CFD analysis, the grid model simulating the sparger and the IRWST pool were developed by the axisymmetry condition and then the steam condensation phenomena by a direct contact was modelled by the so-called condensation region model. The comparison of the CFD results with the test data showed a good agreement as a whole, but a small temperature difference was locally found at some locations. However, the commercial CFD code of CFX4.4 together with the condensation region model can simulate the thermal mixing behaviour reasonably well when a sufficient number of mesh distribution and a proper numerical method are adopted.