• Nuclear Engineering and Technology
• /
• 제56권2호
• /
• pp.611-623
• /
• 2024

The ISP-47 TOSQAN experiment was analyzed with containmentFOAM which is an open-source CFD code based on OpenFOAM. The containment phenomena taking place during the experiment are gas mixing, stratification and wall condensation in a mixture composed of steam and non-condensable gas. The k-ω SST turbulence model was adopted with buoyancy turbulence models. The wall condensation model used is based on the diffusion layer approach. We have simulated the full TOSQAN experiment which had a duration 20000 s. Sensitivity studies were conducted for the buoyancy turbulence models with SGDH and GGDH and there were not significant differences. All the main features of the experiments namely pressure history, temperature, velocity and gas species evolution were well predicted by containemntFOAM. The simulation results confirmed the formation of two large flow stream circulations and a mixing zone resulting by the combined effects of the condensation flow and natural convection flow. It was found that the natural convection in lower region of the vessel devotes to maintain two large circulations and to be varied the height of the mixing zone as result of sensitivity analysis of non-condensing wall temperature. The computational results obtained with the 2D mesh grid approach were comparable to the experimental results.

• 대한기계학회논문집B
• /
• 제36권3호
• /
• pp.335-342
• /
• 2012

자동차배출가스는 이산화탄소($CO_2$)에 의한 지구온난화 및 탄화수소(HC)와 질소산화물($NO_x$)에 의한 오존 생성을 야기하는 등, 인체와 환경에 나쁜 영향을 미치기 때문에 이에 대한 관심이 증폭되고 있다. 가솔린 직접분사 (Gasoline Direct Injection; GDI)엔진은 디젤엔진과 같이 연소실내에 연료를 직접 공급하는 방식으로서 가솔린엔진의 취약점으로 지적되어 오던 높은 연료소비율 문제를 획기적으로 개선할 수 있는 기술로 평가되고 있다. 본 연구에서는 분무유도방식(Spray-guided type)의 GDI엔진을 이용하여 공기과잉률 2.0 이상의 초희박 연소를 통해 연료소비율을 개선하였다. 추가적인 연료소비율 개선 및 배출가스 저감을 위해 희박연소시 다단 분사전략과 Exhaust Gas Recirculation (EGR)을 적용하였다. 배출가스 수준과 운전성능을 평가하고 이를 배출가스 규제와 비교 검토함으로써 국내 관련기술 개발 방향 및 상용화 가능성에 대해 검토하고자 하였다.

• Pediatric Gastroenterology, Hepatology & Nutrition
• /
• 제24권2호
• /
• pp.135-144
• /
• 2021

Purpose: Although ultrasonography is the gold standard of diagnosing intussusception, plain abdomen radiograph (AXR) is often used to make differential diagnosis for pediatric patients with abdominal pain. In intussusception patients, we aimed to analyze the AXR and clinical data to determine the characteristics of early AXR findings associated with diagnosis of intussusception and recurrence after reduction. Methods: Between January 2011 and June 2018, 446 patients diagnosed with intussusception based on International Classification of Diseases-10 code of K56.1 were admitted. We retrospectively reviewed medical records of 398 patients who received air reduction; 51 of them have recurred after initial reduction. We evaluated six AXR features including absent ascending colon gas, absent transverse colon gas, target sign, meniscus sign, mass, and ileus. Clinical data and AXR features were compared between single episode and recurrence groups. Results: Two groups did not show significant differences regarding clinical data. Mean time to recurrence from air reduction was 3.4±3.2 days. Absent ascending colon gas (63.9%) was the most common feature in intussusception, followed by mass (29.1%). All of six AXR features were observed more frequently in the recurrence group. Absent transverse colon gas was the most closely associated AXR finding for recurrence (odds ratio, 2.964; 95% confidence interval, 1.327-6.618; p=0.008). Conclusion: In our study, absence of ascending colon gas was the most frequently seen AXR factor in intussusception patients. Extended and careful observation after reduction may be beneficial if such finding on AXR is found in intussusception patients.

• 한국산림과학회지
• /
• 제102권3호
• /
• pp.398-406
• /
• 2013

신규조림/재조림 CDM은 교토의정서에서 인정하는 온실가스 흡수원 활동이다. 본 연구에서는 강원도 고성군 간성읍 흘리 지역에서 시행되고 있는 소규모 신규조림/재조림 CDM 시범사업을 대상으로 온실가스 감축량을 산정하였다. 적용된 방법론은 AR-AMS0001이며, 조림수종은 잣나무, 낙엽송, 자작나무 등이고 조림 면적은 총 75.0 ha이다. 베이스라인 시나리오 및 탄소 저장고 선택, 대상지 구획화 등을 실시하고 이를 바탕으로 실질 순 온실가스 감축량, 베이스라인 순 온실가스 감축량, 누출량 산정 등의 과정을 거쳐 순 인위적 온실가스 감축량을 산정하였다. 연구 결과 조림 후 20년간 발생하는 온실가스 감축량은 12,415 ton $CO_2-e$이며 ha당 165.5 ton $CO_2-e/ha$로 나타났다. 본 시범사업은 국내에서 시행된 최초의 신규조림/재조림 CDM이며, 온실가스 감축량 산정에서 대상지 실정을 반영한 국가 고유 자료를 사용함으로써 산정 결과의 정확성을 향상시켰다는 점에서 의미가 있다.

• Nuclear Engineering and Technology
• /
• 제48권4호
• /
• pp.881-892
• /
• 2016

Following the Fukushima accident and its extended station blackout, attention was brought to the importance of the spent fuel pools' (SFPs) behavior in case of a prolonged loss of the cooling system. Since then, many analytical works have been performed to estimate the timing of hypothetical fuel uncovery for various SFP types. Experimentally, however, little was done to investigate issues related to the formation of a flammable gas mixture, distribution, and stratification in the SFP building itself and to some extent assess the capability for the code to correctly predict it. This paper presents the main outcomes of the Experiments on Spent Fuel Pool (ESFP) project carried out under the auspices of Swissnuclear (Framework 2012-2013) in the PANDA facility at the Paul Scherrer Institut in Switzerland. It consists of an experimental investigation focused on hydrogen concentration build-up into a SFP building during a predefined scaled scenario for different venting positions. Tests follow a two-phase scenario. Initially steam is released to mimic the boiling of the pool followed by a helium/steam mixture release to simulate the deterioration of the oxidizing spent fuel. Results shows that while the SFP building would mainly be inerted by the presence of a high concentration of steam, the volume located below the level of the pool in adjacent rooms would maintain a high air content. The interface of the two-gas mixture presents the highest risk of flammability. Additionally, it was observed that the gas mixture could become stagnant leading locally to high hydrogen concentration while steam condenses. Overall, the experiments provide relevant information for the potentially hazardous gas distribution formed in the SFP building and hints on accident management and on eventual retrofitting measures to be implemented in the SFP building.

• Nuclear Engineering and Technology
• /
• 제56권3호
• /
• pp.1066-1080
• /
• 2024

SMART100 has a containment pressure and radioactivity suppression system (CPRSS) for passive containment cooling system (PCCS). This prevents overheating and over-pressurization of a containment through direct contact condensation in an in-containment refueling water storage tank (IRWST) and wall condensation in a CPRSS heat exchanger (CHX) in an emergency cool-down tank (ECT). The Korea Atomic Energy Research Institute (KAERI) constructed scaled-down test facilities, SISTA1 and SISTA2, for the thermal-hydraulic validation of the SMART100 CPRSS. Three separate effect tests were performed using SISTA1 to confirm the heat removal characteristics of SMART100 CPRSS. When the low mass flux steam with or without non-condensable gas is released into an IRWST, the conditions for mitigation of the chugging phenomenon were identified, and the physical variables were quantified by the 3D reconstruction method. The local behavior of the non-condensable gas was measured after condensation inside heat exchanger using a traverse system. Stratification of non-condensable gas occurred in large tank of the natural circulation loop. SISTA2 was used to simulate a small break loss-of-coolant accident (SBLCOA) transient. Since the test apparatus was a metal tank, compensations of initial heat transfer to the material and effect of heat loss during long-term operation were important for simulating cooling performance of SMART100 CPRSS. The pressure of SMART100 CPRSS was maintained below the design limit for 3 days even under sufficiently conservative conditions of an SBLOCA transient.

• 한국수소및신에너지학회논문집
• /
• 제34권2호
• /
• pp.155-161
• /
• 2023

Recently, a study on alternative and renewable energy is being conducted due to energy depletion and environmental problems. In particular, a hydrogen has the advantage of converting and storing the remaining energy into water-electrolyzed hydrogen through renewable energy generation. In general, due to reasons such as insulation problems, a study on high-pressure hydrogen storage tanks and related parts has recently been conducted. However, in the case of liquid hydrogen, the volume can be reduced by about 800 times or more compared to high-pressure hydrogen gas, so the study on this is needed as a technology that can increase energy density. In this study, the evaporation characteristics were analyzed under fixed heat flux conditions for liquid hydrogen storage tanks and the change in thermal stratification according to sloshing was analyzed. The heat flux condition was fixed at 250 W/m² and the horizontal resonance frequency of the primary mode was applied to the storage tank. As a result, it was confirmed that the thermal stratification phenomenon decreased compared to the case where the slashing was not present due to forced convection when the slashing was present.

• International Journal of Automotive Technology
• /
• 제2권3호
• /
• pp.93-101
• /
• 2001

Distribution of fuel-air mixture has a strong influence on performance and emissions of a compressed natural gas (CNG) engine. In this paper, parametric study is performed by KIVA-3V to investigate fuel-air mixture with respect to injection timing, cycle equivalence ratio and engine speed. With open-valve injection intensive mixing during intake and compression stroke results in relatively homogeneous mixture in the cylinder. Sequential induction of fuel-air mixture and fresh air results in stratification in the cylinder among the test cases at closed-valve injection. There is close similarity in the calculated distributions of the mixture in the cylinder with different cycle equivalence ratios and engine speeds. The results are compared against pressure traces and flame images obtained in a single cylinder engine converted from a 11L six-cylinder heavy duty diesel engine.

• 한국미생물·생명공학회지
• /
• 제3권1호
• /
• pp.23-29
• /
• 1975

맥주의 재래식 나분발효에 따른 5가지 조건, 즉 발효기간, 변온, 자동교반, 성층, 피포현상 가운데, 한가지 조건씩을 실험적으로 변경시켜 맥즙을 발효하고, 생성된 맥주를 개스크로마토 그래피로써 분석해 본 결과, 이상의 5가지 발효조건이 모두 맥주의 향미형함에 필요하다는 것을 알았다.

• 한국전산유체공학회지
• /
• 제6권4호
• /
• pp.1-7
• /
• 2001

Wind flow perturbations, recirculations and turbulence generated by buildings often dominate air pollutant distributions around buildings. This paper describes dispersion of contaminants in the vicinity of a building by solving the concentration equation based on previously simulated wind flow field. Turbulence closure is achieved by using the standard k-ε two-equation model. The paper shows application of the CIP method for solving a species concentration equation of contaminant gas around a rectangular building for two different sources under conditions of neutral atmospheric stratification. Results have been compared to the experimental data and the previous numerical results by hybrid scheme. The computational results of concentration profiles by the CIP method agree well with experimental data.