• 말소리와 음성과학
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• 제15권2호
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• pp.31-40
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• 2023

목적: 물 속에서 튜브 발성은 semi-occluded vocal tract(SOVT) 연습 중 하나로 환자가 튜브를 물 속에 잠기게 하여 거품을 내면서 발성을 하는 것으로 음성 훈련에 널리 사용되어 왔다. 본 연구는 과기능성 음성장애 환자를 대상으로 물저항발성 동안 튜브 직경과 튜브를 담그는 물 깊이가 물거품 높이와 최대발성지속시간(maximum phonation time, MPT)에 미치는 영향을 조사하는 것을 목적으로 한다. 방법: 과기능성 음성장애 환자 17명에게 튜브 직경(5, 7, 10 mm), 튜브를 담그는 물 깊이(4, 7, 10 cm)에 따라 지속적인 /u/발성을 하면서 거품을 내도록 하였다. 물거품 높이 및 MPT 기록을 위해 수위 센서를 이용한 물저항발성 바이오피드백 시스템을 사용하였다. 결과: 물거품 높이는 튜브 직경에 의해 유의하게 변화한 반면 MPT는 튜브 직경과 깊이에 따라 유의하게 변화하였다. 직경이 더 넓을수록 주어진 깊이에 대해 유의하게 낮은 물거품 높이를 나타냈지만, 상대적으로 일관된 버블 높이가 유지되었다. 물의 깊이에 따라 주어진 튜브 직경에서 물거품 높이는 유의한 차이가 없었으나, 물의 깊이에 따라 MPT는 유의하게 감소하였고 튜브가 넓을수록 MPT가 유의하게 감소하였다. 결론: 수위 센서 방식의 물저항 바이오피드백 시스템은 튜브 직경 및 수심에 따른 기포 특성 및 성대 진동에 대해 유용한 정보를 제공하였다. 또한, 수위센서를 이용한 물저항발성 바이오시스템은 과기능적 음성장애가 있는 환자의 물저항 발성 중 호흡 지지를 모니터링하는 데 유용하게 사용될 수 있다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.1598-1603
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• 2004

This paper is an experimental study on the performance characteristic with a variation of capillary diameter and length. The performance characteristic of a refrigeration system is predicted that it is occurring changes of flow pattern and pressure drop in a capillary tube because of reduction of capillary diameter 0.74 to 0.6 mm. The difference between experimental results and analytical results is mainly caused by values of friction factor for using to calculate pressure drop through a small diameter capillary tube under 0.74mm. The experimental equation is derived from capillary tube test data using curve fitting method.

• 한국산학기술학회논문지
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• 제8권6호
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• pp.1307-1312
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• 2007

본 논문은 세관내 R-134a의 유동특성을 실험적으로 조사한 것이다. 이에 대한 실험장치는 마그네틱 기어 펌프, 증발기, 수액기, 사이트 글라스, 응축기 계측기로 구성된다. 유동양식을 관찰하기 위한 사이트 글라스는 증발기 입출구에 설치하였다. 실험은 세관내 R-22와 R-134a의 유동특성을 살펴보기 위해서 수행되었다. 이에 대한 실험변수인 냉매질량 유속은 100에서 1000 $kg/m^2s$이고, 포화온도는 $30^{\circ}C$이다. 증발과정 중의 유동양식에서 2 mm의 세관내 환상유동은 8 mm관의 대구경관에 비해 저건도와 저질량유속에서 발생하였다. 본 실헐 결과와 종래의 유동양식 선도와 비교한 결과, 2 mm의 세관내 증발 유동양식은 Baker, Mandhane, Taitel-Dukler의 유동양식 선도와는 큰 차이를 보였지만, Dobson의 유동양식 선도와는 좋은 일치를 보였다.

• 대한기계학회논문집B
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• 제24권7호
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• pp.930-937
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• 2000

A series of data sets for the heat transfer coefficient versus wall superheat has been obtained experimentally using various combinations of tube diameters ($9.7{\sim}25.5mm$), surface roughness ($15.1{\sim}60.9nm$), and tube orientations (horizontal and vertical) to obtain effects of tube diameters on nucleate pool boiling heat transfer for the saturated water at atmospheric pressure. In addition, the results are compared with the well known Cornwell and Houston's correlation for horizontal tubes to identify the deviation of the present experimental data from the correlation and the applicability of it to vertical tubes. The experimental results show that the heat transfer coefficient decreases as the tube diameter increases for both horizontal and vertical tubes and they are in good agreement with the Cornwell and Houston's correlation within ${\pm}20%$ scatter range.

• 한국안전학회지
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• 제30권4호
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• pp.168-173
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• 2015

A steam generator tubing is one of the main pressure boundary of the reactor coolant system in the nuclear power plants. Structural integrity refers to maintaining adequate margins against failure of the tubing. Burst pressure of a tube at tube support plate can be higher than that for a free-span tube because failure behaviors could be interfered from the tube support plate. Alternative repair criteria for out-diameter stress corrosion cracking indications in tubes to the drilled type tube support plate were developed, however, there are very limited information to the eggcrate type tube support plate. This paper discussed reinforcement effect of steam generator tube burst pressure with axial out-diameter stress corrosion cracking within an eggcrate type tube support plate. A series of tube burst tests were performed under the room temperature and it was found out that there is no significant but marginal effects.

• Journal of Advanced Marine Engineering and Technology
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• 제30권4호
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• pp.483-493
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• 2006

A model for a pressure drop of water vapor flow across tube banks in a horizontal tube absorber of an absorption chiller/heater using LiBr solution as a working fluid has been developed based on a commercial 20RT(70kW) absorption chiller/heater. The numerical results show that the characteristic of the pressure drop in the shell side of the horizontal tube absorber is completely different from that in a conventional shell and tube heat exchanger. Especially, solution film thickness has significant influence on the vapor pressure drop in the horizontal tube absorber. In addition, the effects by the tube diameters, the longitudinal pitch to diameter ratio, and Reynolds number of the vapor flow, on the vapor pressure drop have been studied to evaluate the compactness of tube absorber. It was found that the vapor pressure drop decreases as tube diameter increases, the longitudinal pitch to diameter ratio increases, and Reynolds number of the vapor flow decreases. A comparison of the present study results with well-established experimental and numerical results showed a good overall agreement.

• 수산해양교육연구
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• 제6권1호
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• pp.58-76
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• 1994

Heat transfer and pressure drop measurements are made on low integral-fin tubes in turbulent water flow condition. The integral-fin tubes investigated in this paper are nominally 19mm in diameter. Eight tubes have been used with trapezoidally shaped integral-fins having fin density from 748 to 1654 fpm and 10, 30 grooves. Plain tube having same diameter as finned tube is also tested for comparison. Experiments are carried out using R-11 as working fluid. The refrigerant condensates at a saturation state of $30^{\circ}C$ on the outside tube surface cooled by coolant. The amount of noncondensable gases present in the test loop is reduced to a negligible value by repeated purging. For a given heat input to the boiler and given cooling water flow rate, all test data are taken on steady state. The heat transfer loop is used for testing single long tubes and cooling water is pumped from a storage tank through filters and flowmeters to the horizontal test section where it is heated by steam condensing on the outside of the tube. The pressure drop across the test section is measured by means of pressure gauge and manometer. Each tube tested is cleaned with sodium dichromate pickling solution and well rinsed with water prior to installation in the test section. The results obtained in this study is as follows : 1. Based on inside diameter and nominal inside area, heat transfer of finned tube is enhanced up to 4 times as that of a plain tube at constant Reynolds number and up to 2 times at constant pumping power. 2. Friction factors are up to 1.6~2.1 times those of plain tube. 3. At a given Reynolds number, Nusselt number decrease with increasing pitch to diameter. 4. The constant pumping power ratio for low integral-fin tubes increase directly with the effective area to the nominal area ratio, and with the effective area diameter ratio.

• 한국압력기기공학회 논문집
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• 제19권1호
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• pp.27-35
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• 2023

Pressure tubes are the main components of PHWR core and serve as the pressure boundary of the primary heat transport system. However, because pressure tubes have changed their geometrical dimensions under the severe operating conditions of high temperature, high pressure and neutron irradiation according to the increase of operation time, all dimensional changes should be predicted to ensure that dimensions remain within the allowable design ranges during the operation. Among the deformations, the diameter expansion due to creep leads to the increase of bypass flow which may not contribute to the fuel cooling, the decrease of critical channel power and finally the deration of the power to maintain the operational safety margin. This study is focused on the modeling of the expansion of the pressure tube diameter based on the operating conditions and measured diameter data. The pressure tube diameter expansion was modeled using the neutron flux and temperature distributions of each fuel channel and each fuel bundle as well as the measured diameter data. Although the basic concept of the current modeling approach is simple, the diameter prediction results using the developed methodology showed very good agreement with the real data, compared to the existing methodology.

• 한국기계기술학회지
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• 제13권4호
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• pp.165-168
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• 2011

In this paper, the hybrid tube expander unit for fin and tube type heat exchanger are developed by means of enlarging and inserting the smooth tube with a small diameter to a finned tube having larger diameter. In other word, the tube expander tool that is easy to attach and remove from tube is developed. The hybrid tube expander unit developed in this study can move easily and enlarge the tube without fixing at tube sheet. Also, this unit has a function removing scales inside tube by replacing a tube expander ball.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2005년도 하계학술발표대회
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• pp.231-231
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• 2005