• 에너지공학
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• 제26권3호
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• pp.71-77
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• 2017

피동고압충수용 혼합형 안전주입탱크 (Hybrid SIT)의 압력평형시간은 냉각수 주입시기를 결정하는 주요인자이다. 한국원자력연구원 (KAERI)에서는 Hybrid SIT에서의 내부 열수력적 거동을 고찰하기 위해 개별효과시험 장치를 구축하였으며, 다양한 운전조건에서의 압력평형시간에 대한 민감도 시험을 수행하였다. 개별효과시험을 통해 압력평형시간을 결정하는 주요인자들을 도출하였으며, 그 중 증기의 벽면응축 및 냉각재와의 직접접촉응축이 압력평형시간을 결정하는 주요 현상임을 파악하였다. 본 연구에서는 개별효과 시험결과들을 이용하여 각각의 응축현상들이 압력평형에 미치는 영향을 정량적으로 분석하고 혼합형 SIT의 압력평형시간을 예측하기 위한 방법론을 제시하였다.

• 한국전산유체공학회지
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• 제17권3호
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• pp.75-86
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• 2012

We developed a preliminary CFD analysis methodology to predict a pressure build up due to hydrogen flame acceleration in the APR1400 IRWST on the basis of CFD analysis results for test data of hydrogen flame acceleration in a scaled-down test facility performed by Korea Atomic Energy Research Institute. We found out that ANSYS CFX-13 with a combustion model of the so-called turbulent flame closure and a model constant of A = 5.0, a grid model with a hexahedral cell length of 5.0 mm, and a time step size of $1.0{\times}10^{-5}$ s can be a useful tool to predict the pressure build up due to the hydrogen flame acceleration in the test results. Through the comparison of the simulated results with the test results, we found out that the proposed CFD analysis methodology enables us to predict the peak pressure within an error range of about ${\pm}29%$ for the hydrogen concentration of 19.5%. However, the error ranges of the peak pressure for the hydrogen concentration of 15.4% and 18.6% were about 66% and 51%, respectively. To reduce the error ranges in case of the hydrogen concentration of 15.4% and 18.6%, some uncertainties of the test conditions should be clarified. In addition, an investigation for a possibility of flame extinction in the test results should be performed.

• 연구논문집
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• 통권29호
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• pp.185-194
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• 1999

The shape and thickness distribution according to the pressure-time curve were carried out using the FEM and experiment. Also, mechanical properties were investigated. The square cup parts have been formed with pressure-time curve generated by result of analysis. The tensile strength and elongation have been investigated according to applied pressure conditions using the tensile test specimen obtained from the superplastic formed cup. We can use to predict the shape of formed part under the applied pressure using the FEM analysis. In the case of optimum pressure condition, the thickness distribution and mechanical properties were improved. From this study, we can find the important of optimum pressure-time condition. We have investigated about the forming of airplane part and fuel tank for motorcycle. If the applied load used in boundary conditions was appropriate, the simulation result coincides with the formed part. However, it is very difficult to define the pressure condition in complicated shape. Thus, it is need to develop the optimum pressure condition for superplastic forming.

• International Journal of Air-Conditioning and Refrigeration
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• 제12권2호
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• pp.70-78
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• 2004

An experimental study on the pressure drop during flow boiling for pure refrigerants Rl34a and R123, and their mixture was carried out in a uniformly heated horizontal tube. Tests were run at a pressure of 0.6㎫ and in the ranges of heat flux 5-50㎾/$m^2$, vapor quality 0-100 percent and mass velocity of 150-600 kg/$m^2$s. Generally, the two-phase frictional multiplier is used to predict the frictional pressure drop during the two-phase flow boiling. The obtained results have been compared to the existing various correlations for the two-phase multiplier. Also, the frictional pressure drop was compared to a few available correlations; The Lockhart-Martinelli correlation considerally overpredicted the frictional pressure drop data for mixture as well as pure components in the entire mass velocity ranges employed in the present study, while the Chisholm correlation underpredicted the present data. The Friedel correlation was found to satisfactorily correlate the frictional pressure drop data except for a low quality region.

• 한국농공학회:학술대회논문집
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• 한국농공학회 1998년도 학술발표회 발표논문집
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• pp.142-145
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• 1998

The purpose of this study is to estimate lateral formwork pressure controlled by super-workable fresh concrete using prototype structrues such as, tall wall, retaining wall, and beam quantitativly. As a result of this experiment, a function which can be used to design a formwork system and to predict formwork pressure curve is formulated.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1986년도 한국자동제어학술회의논문집; 한국과학기술대학, 충남; 17-18 Oct. 1986
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• pp.212-215
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• 1986

For distillation columns, dynamic models which consider variable pressure and vapor holdup were studied. A most rigorous model which used the vapor hydraulic equation was studied with implicit methods. Vapor holdup must be considered in high pressure columns in order to predict dynamic responses accurately. The effect of pressure changes on the tray was only important for the vacuum column, particularly when heat input disturbances occurred. The rigorous vapor hydraulic model was shown to be useful, despite the fact that it is extremely stiff, provided an implicit integration algorithm (LSODES) is employed.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 추계학술대회논문집
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• pp.555-558
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• 2005

If sound pressure values on boundary are available, then we can predict the sound field in it. Similarly, we can reproduce sound field by manipulating sound pressure values on boundary. In this paper, a noble method of sound reproduction using this concept is introduced and evaluated for the case in which sound field is 2-D half-infinite plane by computer simulation.

• Journal of Biosystems Engineering
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• 제20권4호
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• pp.333-342
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• 1995

The resistance to air flow through fruits and vegetables in bulk was an important consideration in the design of the pressure cooling system. The amount of resistance to air flow through produce in bulk normally depended upon air flow rate, stacking depth, porosity, stacking patterns and shape and site of product. But, there was not enough information relating the effects of those factors on air flow resistance. The objectives of this study were to investigate the effect of stacking depth, stacking patterns, porosity and airflow rate on airflow resistance and to develop a statistical model to predict static pressure drop across the produce bed as a function of air flow rate, stacking depth, bed porosity, and product size. Mandarins and tomatoes were used in the experiment. The airflow rate were in the range of 0.1~1.0 ㎥/s.$m^2$, the porosity were in the range of 0.25~0.45, the depth were in the range of 0.3~0.9m and the equivalent diameters were 5.3cm and 6.3cm for mandarins, and 6.5cm and 8.5cm for tomatoes. Three methods of stacking arrangement were used i.e. cubic, square staggered, and staggered stacking arrangement. The results were summarized as follows. 1. The pressure drops across produce bed increased in proportion to stacking depth and superficial air velocity and decreased in proportion to porosity. 2. The increasing rates of pressure drop according to stacking patterns with the increase of superficial air velocity were different one another. The staggered stacking arrangement produced the highest increasing rate and the cubic stacking arrangement produced the lowest increasing rate. But it could be assumed that the stacking patterns had not influenced greatly on pressure drops if it was of equal porosity. 3. The statistical models to predict the pressure drop across produce bed as a function of superficial air velocity, stacking depth, porosity, and product diameter were developed from these experiments.

• 전력전자학회논문지
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• 제13권3호
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• pp.171-178
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• 2008

본 논문에서는 압력예측기법과 직접 순시토크 제어기법을 통한 유압펌프용 SRM의 압력제어 구동시스템을 제안하였다. 일반적으로 유압 펌프 시스템은 유압센서의 응답성으로 인하여 제어시스템의 시지연이 비교적 길어지게 되며, 이러한 시간지연은 PI 또는 PID 제어 구조에서 장시간의 진동과 불안정화를 만들기 쉽다. 본 논문에서는 시간 지연문제를 해결하고 리플이 없는 압력제어를 위하여 스미스 예측기(simth predictor)를 통한 지연보상과 직접 순시토크제어기법(Direct Instantaneous Torque, 이하 DITC)을 적용하였다. 제안된 제어 방식은 펌프와 센서간의 기구적 문제에 의한 지연문제 해결과 안정성을 확보하고, 펌프 압력제어의 동특성을 향상시키며 전류(轉流, commutation) 구간에서 균일한 토크를 발생시켜 토크 리플을 억제하기 위함이다. 제안된 제어방식은 시뮬레이션과 실험을 통하여 효용성을 검증하였다.

• 한국환경과학회지
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• 제32권9호
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• pp.659-669
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• 2023

The purpose of this study is to predict the pressure drop due to the installation of venturi under diverse operating conditions such as dust concentration, pulse interval and pressure, and filtration velocity using algebraic-linear regression model and use it as an economic data and efficient operating condition for a pulse air jet bag filter. A pilot scale bag filter with a filter a filter size(Ø140 × 850ℓ, 12) was used, and the filters used in the experiment were the polyester filters most commonly used in real industrial sites. The SAS 9.4 program (SAS Institute, USA) was used to predict and to determine the effects of inlet concentration (C_i), pulse interval (P_i) and pressure (P_p), filtration velocity (V_f), presence or absence of venturi, etc. The results are shown below. The variation in pressure drop with or without venturi installation was 38.8 mmAq when venturi is installed and 47.6 mmAq when venturi is not installed, indicating a difference in pressure drop of 8.8 mmAq depending on venturi installation. It is estimated that the efficiency can be improved by about 18.5% if the venturi is installed.