• International Journal of Aeronautical and Space Sciences
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• 제8권2호
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• pp.126-131
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• 2007

In this paper, Monte Carlo Simulation (MCS) method was used as an uncertainty assessment tool for air flow, net thrust measurement. Uuncertainty sources of the net thrust measurement were analyzed, and the probability distribution characteristics of each source were discussed. Detailed MCS methodology was described including the effect of the number of simulation. Compared to the conventional sensitivity coefficient method, the MCS method has advantage in the uncertainty assessment. The MCS is comparatively simple, convenient and accurate, especially for complex or nonlinear measurement modeling equations. The uncertainty assessment result by MCS was compared with that of the conventional sensitivity coefficient method, and each method gave different result. The uncertainties in the net thrust measurement by the MCS and the conventional sensitivity coefficient method were 0.906% and 1.209%, respectively. It was concluded that the first order Taylor expansion in the conventional sensitivity coefficient method and the nonlinearity of model equation caused the difference. It was noted that the uncertainty assessment method should be selected carefully according to the mathematical characteristics of the model equation of the measurement.

• 소음진동
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• 제4권2호
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• pp.231-238
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• 1994

This paper presents an experimental method to find the vibrational transmission characteristics of structures by using the structural intensity method which is used as the important techniques of active vibration control method. Experimental results are obtained from measurements performed on a structure beam by 2, 3 and 4 position linear accelerometr array (2, 3 and 4 structural intensity : 2, 3 and 4 S.I.) methods at near and farfield conditions. These results are compared with the measurement values of conventional power flow measurement method called input power measurement in order to verify the accuracy of structural intensity methods. To minimize the errors associated with 2, 3 and 4 S.I. methods, the measurement locations were selected by the result of modal analysis and the averaged data by the inter-change of accelerometer array was utilized. In 3 and 4 S.I. methods measured wavenumber instead of theoretical wavenumber was used. This paper shows that measurements of bending wave power flow by using 2, 3 and 4 S.I. methods can give accurate values under general field conditions in structural beam and the accuracy of 2, 3 S.I. methods is higher than 4 S.I. methods. Finally, 2 position linear accelerometer array method is suggested as the practical structural intensity technique.

• Nuclear Engineering and Technology
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• 제51권4호
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• pp.1169-1175
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• 2019

The minimum detectable activity (MDA) value was derived according to the flow rate of the sample and degree of amplification of the device by sending the sample directly from the collection site to the detection part through a pump. This method can lead to reduction in time and cost compared to the existing measurement method that uses a pre-treatment process. In this study, experiments were conducted on $^3H$ and $^{90}Sr$, which are the major pure beta-emitting radionuclides, by setting the sample flow rate and the amplification gain as factors. The MDA values were derived according to the flow rates, considering that the flow rate can affect the MDA values. There were no change in the MDA under different flow rates of 0, 600, 800, and 1000 mL/min. Therefore, it was confirmed that the flow rate may not be considered when collecting samples for monitoring in actual field. As the degree of amplification of the amplifier increased, the time required to reach the target MDA decreased. When the amplification was quadrupled, the detection efficiency increased by approximately 23.4 times, and the time to reach the MDA decreased to approximately 1/550 times. This method offers the advantage of real-time on-site monitoring.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2006년 제4회 한국유체공학학술대회 논문집
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• pp.227-230
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• 2006

The method of mass flow rate measurement using a critical nozzle is well established in the flow satisfying ideal gas law. However, in the case of measuring high-pressure gas flow, the current method shows invalid discharge coefficient because the flow does not follow ideal gas law. Therefore an appropriate equation of state considering real gas effects should be applied into the method. The present computational study has been performed to give an understanding of the physics of a critical nozzle flow for high-pressure hydrogen gas and find a way for the exact mass flow prediction. The two-dimensional, axisymmetric, compressible Navier-Stokes equations are computed using a fully implicit finite volume method. The real gas effects are considered in the calculation of discharge coefficient as well as in the computation. The computational results are compared with the previous experimental data and predict well the measured mass flow rates. It has been found that the discharge coefficient for high-pressure hydrogen gas can be corrected properly adopting the real gas effects.

• 한국안전학회지
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• 제25권6호
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• pp.22-27
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• 2010

Flow Coefficients of intake port in an engine cylinder head were measured by a newly designed flow rig. In measuring the flow coefficient with traditional method, the valve lift was manually varied by technician with adjusting a micrometer which is directly connected to the intake valve of the cylinder head. The cam shaft of the cylinder head is directly rotated by a step motor and the valve lift was automatically varied with cam shaft profile in the newly designed flow rig. The measurement of the flow coefficient was automated by rotating the cam shaft with the step motor. Automatic measurement of the flow coefficient could be safely measured by separating a technician from the noise and vibration of the traditional flow rig. Also, the automatic measurement of the flow coefficient reduce the measurement time and provide meaningful statistical data.

• 반도체디스플레이기술학회지
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• 제7권2호
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• pp.55-58
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• 2008

The objective of the research is to design, manufacture and test a Mass Flow Controller(MFC) capable of measuring compressible fluid flows based on a "bucket and stop-watch"method. The basic principle is the measurement of time, where the time taken to fill and empty a bucket of known volume is measured. This method of flow measurement is a new concept when compared to a commercilized current mass flow controller. For the flow meter to be able to compete with established designs it not only must be comparable in cost and robustness, it must be very accurate and reliable as well. This device should be able to handle fluid flows in the range of 0.1ml/min to 10ml/min within an accuracy of ${\pm}$1%. A possible application for a device such as this is in electronics industry where arsenic gas is used in the production of silicon chips.

• 대한기계학회논문집B
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• 제28권6호
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• pp.682-687
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• 2004

Y-junction microchannels are widely used as a flew mixer. Fluids are entered from two branch channels and merged together at a combined channel. In this study, we suggest a simple method to create the fluid digitization using flow instability phenomena. Two immiscible liquids (water/oil) are infused continuously to each Y-junction inlets. Because of the differences in fluid and flow properties at the interface, oil droplet is formed automatically followed by flow instability. In order to clarify the hydrodynamic aspects involved in oil droplet formation, a quantitative flow visualization study has performed. Highly resolved velocity vector fields are obtained by a micro-PIV technique, so that detail flow structures around the droplet are illustrated. In this study, fluorescent particles were mixed with water only for visualization of oil droplet and velocity field measurement in water flow.

• 한국태양에너지학회 논문집
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• 제34권1호
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• pp.117-124
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• 2014

Airtightness standards using fan pressurization method are normally used for measuring small buildings, detached houses, and apartment units. And, it is easy to conduct airtightness measurement through this fan pressurization method. However, it can be difficult to achieve accurate measurement results for the large buildings as the height and volume of the buildings have been increased. In this paper, we studied the principle of airtightness method by fan pressurization. And, we reviewed the measurement process described in ISO 9972, EN 13829, ASTM E779, ATTMA TS 1, CAN/CGSB 149.15, and JIS A 2201. Then, we categorized the methods' items according by air flow rate (Q) and pressure difference(${\Delta}P$). As a result, we made a comparison analysis on the measurement methods appeared in each standards. And, we achieved 5 test conditions about air flow rate and pressure difference to state requirements for large buildings airtightness measurement.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2088-2093
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• 2008

In this study, flow field measurement of the Pebble Bed Reactor(PBR) for the High Temperature Gas-cooled Reactor(HTGR) was performed. Large number of pebbles in the core of PBR provides complicated flow channel. Due to the complicated geometries, numerical analysis has been intensively made rather than experimental observation. However, the justification of computational simulation by the experimental study is crucial to develop solid analysis of design method. In the present study, a wind tunnel installed with pebbles stacked was constructed and equipped with the Particle Image Velocimetry(PIV). We designed the system scaled up to realize the room temperature condition according to the similarity. The PIV observation gave us stagnation points, low speed region so that the suspected high temperature region can be identified. With the further supplementary experimental works, the present system may produce valuable data to justify the Computational Fluid Dynamics(CFD) simulation method.

• 한국가시화정보학회지
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• 제10권3호
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• pp.30-36
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• 2012

We are planning to construct a scaled-down moderator facility to simulate the CANDU-6 moderator circulation phenomena during steady state operating and accident conditions. In the present work a preliminary experiment using a 1/40 scaled-down moderator tank has been performed to investigate the anticipated problems of the flow visualization and measurement in the planning scaled-down moderator facility. We shortly describe CFD analysis result for the 1/40 scaled-down test model and the flow measurement techniques used for this test facility under isothermal flow conditions. The Particle Image Velocimetry (PIV) method is used to visualize and measure the velocity field of water in a transparent Plexiglas tank. Planar Laser Induced Fluorescence (PLIF) technique is used to evaluate the feasibility of temperature field measurement in the range of $20-40^{\circ}C$ of water temperature using an one-color method.