• 설비공학논문집
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• 제18권2호
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• pp.186-191
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• 2006

In this study, five experiments were carried out, with an orifice located downstream of a fan in case I where upstream duct length is 6 D, and that in the downstream is 4 D and different downstream distance to the fan in the rest, so as to determine the optimal location of the orifice and reduce the duct length of airflow measurement device. The resulting flow rate-pressure drop correlations were found to satisfy the limitation of SMACNA standard, which specified an error of $\pm7.5\%$ based on the real flow rate. Also, the best one of five. cases was achieved with the orifice located midway of the orifice duct four times its diameter long.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.2151-2156
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• 2004

In this study, five experiments were carried out, with an orifice located downstream of a fan in case I and upstream distance to the fan in the rest cases(case $II{\sim}$), so as to determine the optimal location of the orifice and reduce the size of airflow measurement device. The resulting flow rate-pressure drop correlations were found to satisfy the limitation of SMACNA standard, which specified an error of ${\pm}7.5%$ based on the real flow rate. The best outcome was achieved with the orifice located midway of the orifice duct 4 times its diameter long.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2011년 춘계학술대회논문집
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• pp.596-600
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• 2011

In this numerical analysis, the distortion of flow measurement by inlet velocity profile of orifice flowmeter was investigated. To validate the numerical method, the convergence was monitored and the grid dependency was also checked. realizable k-e model was selected and y+ was about 50 in this calculation. the results shows that the pressure at the pressure tab near pipe wall was changed by inclined inlet velocity profile and it leads to distorted a measurement values of flow through the orifice plate from -3.8% to 9%. Therefore, the fully developed inlet flow was required for accurate flow measurement by orifice flowmeter. If not, the orifice plate installed at wrong location should be re-installed or additional actions should be taken.

• 대한기계학회논문집B
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• 제26권2호
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• pp.278-287
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• 2002

The objective of the paper was to calculate the pressure drop and to investigate the recirculation region of the conical orifices used in Kwang-yang Iron & Steel Company. The flow field with water used as a working fluid was the turbulent flow for Reynolds number of 2$\times$10$^4$. The effective parameters fur the pressure drop and the recirculation region were the conical orifice\`s inclined angle ($\theta$) against the wall, the interval(S) between orifices, the relative angle of rotation($\alpha$) of the orifices, the shape of the orifice's hole(circle, rectangle, triangle) having the same area, the number(N) of the orifice's holes having the same mass flow rate, and the thickness(t) of the orifices. It was fecund that the shape of the orifice's hole, the number of the orifice's holes and the thickness of the orifice affected the total pressure drop a lot and that the conical orifice's inclined angle against the wall, the relative angle of rotation of the orifices, the number of the orifice's holes and the thickness of the orifices affected the center location of the recirculation region. The PISO algorithm with FLUENT code was employed to analyze the flow field.

• 한국분무공학회지
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• 제7권4호
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• pp.32-41
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• 2002

The breakup characteristics of liquid sheets formed by like-doublet injector were investigated in the cold-flow and atmospheric ambient pressure condition. The sheet breakup wavelength, which induces the sheet to be broken into ligaments, as well as the sheet breakup length, which is important for the flame location, was measured using a stroboscopic light. The liquid ligaments are formed intermittently after the breakup of sheet, and the wavelength of ligaments has been believed to have a relation to the combustion instability of liquid rocket engine. Therefore, the wavelength of ligaments and the breakup length of ligaments into fine drops were also measured. Since these spray characteristics are affected by the flow characteristics of two liquid jets before they impinge on each other, we focused on the effects of orifice internal flow such as the cavitation phenomenon that occurs inside the sharp-edged orifice. From the experimental results, we found that the liquid jet turbulence delays the sheet breakup and makes shorter wavelengths for both sheets and ligaments. Since the turbulent strength of sharp-edged orifice is stronger than that of round-edged orifice, the shape of orifice entrance results in large differences in the spray characteristics. Using these results, we proposed empirical models on the spray characteristics of the like-doublet injector, and these models are believed to provide some useful and actual data for designing liquid rocket combustors.

• 한국기계가공학회지
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• 제20권8호
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• pp.107-114
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• 2021

Butterfly valves are used in various industries to control the flow rate, flow direction, pressure, and temperature. These are gaining popularity in the field of plant industry to enable high-differential pressure because of their low maintenance costs and ease of installation. This study presents a numerical analysis method to analyze changes in the flow characteristics of a high-differential pressure control butterfly valve based on the location and shape of the orifice. The numerical analysis was conducted using a commercial CFD program. The analysis results show a correlation between the orifice shape and cavitation phenomenon.

• Restorative Dentistry and Endodontics
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• 제45권4호
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• pp.46.1-46.8
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• 2020

Objectives: This study aimed to investigate the incidence and location of the second mesiobuccal root (MB2) canal in maxillary molars with the aid of various measuring points and lines using cone-beam computed tomography (CT). Materials and Methods: A total of 205 images of patients who underwent cone-beam CT examinations between 2011 and 2015 as part of their dental diagnosis and treatment were included. There were 76 images of the maxillary first molar and 135 images of the maxillary second molar. Canal orifices were detected at -1 mm from the top of the pulpal floor on cone-beam CT images. Image assessment was performed by 2 observers in reformatted image planes using software. Assessments included measurement of the distance between the MB1 and MB2 canals, and the angles between the lines connecting the MB1-MB2 and distobuccal (DB)-palatal (P) canals. The data were analyzed using the student's t-test. Results: The prevalence of the MB2 canal was 86.8% in the first molar and 28.9% in the second molar. The angle between the lines connecting the MB1-MB2 and DB-P canals was 2.3° ± 5.7° in the first molar and -3.95° ± 7.73° in the second molar. The distance between the MB1 and MB2 canals was 2.1 ± 0.44 mm in the first molar and 1.98 ± 0.42 mm in the second molar. Conclusions: The angles between the lines connecting the MB1-MB2 and DB-P canals was almost parallel. These findings may aid in the prediction of the location of the MB2 canal orifice.

• 대한기계학회논문집B
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• 제20권3호
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• pp.1061-1073
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• 1996

Vortex tube is a simple device which splits a compressed gas stream into a cold stream and a hot stream without any chemical reactions. The phenomena of energy separation taking place in a vortex tube has been investigated experimentally. Recently, vortex tube is widely used to local cooler of industrial equipments and air conditioner of special purpose. In this study, experimental study on vortex tube efficiency was performed with various cold end orifices and nozzles type. The experimental results indicate that there is an optimum diameter of cold end orifice and nozzle type for the best cooling performance. The variation of the maximum wall temperature along the vortex tube surface provides useful information about the location of the stagnation point of the flow field at the axis of the vortex tube. The similarity relation for the prediction of the temperature of the cold exit air was obtained.

• 한국임상수의학회지
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• 제26권2호
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• pp.185-188
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• 2009

6개월령의 보스톤 테리어가 미측 음경 돌출과 불완전 형성된 포피, 이분화된 음낭, 잠복고환과 음경골 이형성을 나타내었다. 신체검사상, 요도구멍은 회음부 표면에 위치하였고 섬유성 띠는 귀두로부터 회음부에 있는 요도구멍까지 연결되어 있었다. 또한, 잘못 위치한 요도구멍을 통한 상행성 감염에 의하여 요도염을 나타내었다. 교정수술은 외부생식기 전체와 잠복고환을 절제하기 위하여 시행되었다. 포피, 음경 그리고 잠복고환은 성공적으로 절제되었다. 수술 후 요도구멍을 주기적으로 세척하고 항생제를 투여한 이후, 재발성 요도염은 사라졌다. 만약, 요도구멍의 위치가 재발성 요도염의 원인과 요실금의 주요 원인이 아니라면, 요도구멍을 재형성할 필요가 없는 이 치료법을 이용할 것을 제안한다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.358-363
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• 2008

The spray cross-section characteristics of two-phase spray that using external-mixing nozzle injected into a subsonic cross flow were experimentally studied with various ALR ratio that is $0{\sim}59.4%$. Suction type wind tunnel was used and experiments were conducted to ambient environment. Several plain orifice nozzles with L/d of 30 and orifice diameter of 0.5 mm and orifice length 1.5 mm were tested. Free stream velocity profiles at the injection location were measured using hot wire. Spray images were captured to study collision point and column trajectory. Phase Doppler particle analyzer(PDPA) was utilized to quantitatively measuring droplet SMD, volume flux. Measuring probe of PDPA positions was moved 3-way transverse machine. SMD distributions were layered structure and peaked at the top of the spray plume and low value at bottom of the spray. Volume flux of spray was distributed to the two side region and volume flux quantity decreased when ALR ratio increased. It was found that the perpendicularly injected two-phase spray jet of external mixing into a cross flow showing that mistlike spray moved away from the test section bottom region.