• 한국기계가공학회지
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• 제11권2호
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• pp.159-164
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• 2012

The shell & tube heat exchanger is used throughout various industries because of its inexpensive cost and handiness when it comes to maintenance. However, it has many design elements such as the location and the shape of inlet and outlet, the numbers of tubes and baffles, etc. Also, the flow within the shell and the heat transfer are complex. This paper is performed numerical analysis to evaluate capabilities of difference in temperature and pressure drop, which are the performance of channel heat exchanger, one of different types of shell & tube exchanger. Also, factors that affect the performance of channel heat exchanger were selected through design of experiment along with key factors.

• 드라이브 ㆍ 컨트롤
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• 제18권3호
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• pp.23-29
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• 2021

Hydrogen energy is the clean energy source of the future. Ultra-high-pressure hydrogen is used in hydrogen stations, with its parts being developed. On the other hand, ultra-high-pressure ball valve, which is one of its parts, depends on overseas, with the level of domestic research on this being only about 10% of advanced technology research on this abroad. In this study, the shape of an ultra-high-pressure ball valve for a hydrogen station was designed to improve its structural strength. The valve body was designed according to distance between both processed body holes along inlet and outlet ports. The designed vale body was then analyzed using ANSYS to check whether points with stress were concentrated. In addition, the valve with improved body was analyzed to confirm that the valve satisfied the design condition.

• International Journal of Fluid Machinery and Systems
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• 제2권4호
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• pp.439-448
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• 2009

Three inducers were designed to avoid cavitation instabilities. This was accomplished by avoiding the interaction of tip cavity with the leading edge of the next blade. The first one was designed with extremely larger leading edge sweep, the second and third ones were designed with smaller incidence angle by reducing the inlet blade angle or increasing the design flow rate, respectively. The inducer with larger design flow rate has larger outlet blade angle to obtain sufficient pressure rise. The inducer with larger sweep could suppress the cavitation instabilities in higher flow rates more than 95% of design flow coefficient, owing to weaker tip leakage vortex cavity with stronger disturbance by backflow vortices. The inducer with larger outlet blade angle could avoid the cavitation instabilities at higher flow rates, owing to the extension of the tip cavity along the suction surface of the blade. The inducer with smaller inlet blade angle could avoid the cavitation instabilities at higher flow rates, owing to the occurrence of the cavity first in the blade passage and its extension upstream. The cavity shape and suction performance were reasonably simulated by three dimensional CFD computations under the steady cavitating condition, except for the backflow vortex cavity. The difference in the growth of cavity for each inducer is explained from the difference of the pressure distribution on the suction side of the blades.

• 한국태양에너지학회 논문집
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• 제35권1호
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• pp.69-80
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• 2015

A series of numerical analyses was conducted to predict the thermal performance of a solar air heater depending on the hole configuration and geometry in the absorber plate. The planar dimensions of the prototype were 1 m (W) by 1.6 m (H), and the maximum air flow considered was $187m^3/h$. It was considered that protruding holes with a triangular opening in the absorber plate would invoke turbulence in the air flow to enhance the convection heat transfer. Six different hole configurations were investigated and compared with each other, while the hole opening height was considered as a design variable. Three-dimensional transient analyses were performed with a commercial software package on the airflow and heat transfer in the model. The numerical results were analyzed and compared from the view point of the outlet air temperature and its time response to derive the optimal hole pattern and hole opening height.

• 한국가시화정보학회지
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• 제20권3호
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• pp.86-93
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• 2022

An electrostatic precipitator (ESP) is an industrial post processing facility for high efficiency dust mitigation. Uniformity of the flow passing through the inlet duct leading into the main chamber is important for efficient reduction of dust. To examine flow uniformity, this study conducted a numerical analysis of the flow within a scale-down ESP inlet duct. Magnetic resonance velocimetry (MRV) results from a prior study were utilized to validate the Reynolds-averaged Navier-Stokes (RANS) numerical simulations. Both the experimental and computational results displayed a similar recirculation zone shape and normalized velocity profile near the duct outlet for the baseline geometry. To optimize the uniformity of the flow, the number of guide vanes was modified, and the guide vanes were partially extended straight upward. Design evaluation is done based on the outlet velocity distribution and mass flowrate balance between the two outlets. Simulation results indicate that the vane extension is critical for flow optimization in curved ESP ducts.

• International Journal of Human Ecology
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• 제8권2호
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• pp.29-46
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• 2007

The purpose of this study was to analyze characteristics of the bedroom environment of nursing homes for the elderly in Korea. Field case research was performed using a structured checklist and measurements, from Oct. 28th to Dec. 2nd, 2006. Collected data were analyzed for cognitive efficiency, privacy, safety, supportiveness and amenity. Based on nursing homes for the elderly nationwide (Ministry of Health and Welfare, 2006), we choose 43 facilities in which Seoul and six megalopolis areas that had answered our questionnaire in 2006. We then narrowed the list to 14 facilities, balanced them in terms of regional population. The contents of investigation consisted of eight categories: that general characteristics of the bedrooms (including number of residents per room, using a bed or floor mat, the size and shape of the chamber, space for wheelchair turning, signage), door of bedroom (including door, doorknob, door sill/level difference), windows in the bedroom(including type of window, window sill height, window treatment, window safety device/shape, view/daylight), furniture (including personal furniture and lock), finishes (material, character and color of wall, floor, ceiling), lighting (including types of lighting, night lighting, switch), bathroom in the bedroom (including signage, door size/type, doorknob shape, height of the washbowl, size of toilet bowl, handrail, finishes), and other facilities (including outlet and handrails).

• 대한기계학회논문집B
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• 제38권12호
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• pp.1065-1072
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• 2014

본 연구에서는 양흡입 원심블로어의 성능향상을 위하여 임펠러 스플리터의 형상 최적화 연구를 수행하였다. 두 개의 스플리터 형상 설계 변수(스플리터 코드 및 피치)를 선정하여 블로어 성능 및 내부 유동장 특성을 평가하였다. 수치해석에 의한 블로어 성능은 설계유량 조건에서 실험결과와 최대 4 % 이내로 잘 일치하였다. 스플리터 형상 최적화를 통하여 설계조건에서의 블로어 효율 및 압력은 기준 블로어 보다 3.65 % 및 1.14 % 각각 향상되었다. 스플리터 최적설계로 임펠러 날개 부압면의 유동박리를 억제시켜 익간 저속 유동에 의한 압력손실을 줄임으로써 블로어 전체의 성능이 향상되었다. 익간 내부유동 균일화는 임펠러 출구속도 분포에도 영향을 주어 볼류트케이싱 출구압력도 향상되었다.

• 대한기계학회논문집B
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• 제37권4호
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• pp.415-421
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• 2013

본 논문은 두산중공업(주)에서 개발 중인 소형 가스터빈의 축류 터빈 설계 과정을 기술하였다. 축류터빈의 설계 과정은 크게 유로설계, 익형설계, 3D 성능 계산의 세 단계로 구성되며. 최적의 유로를 설계하기 위해 자오면의 형상, 평균 반경, 블레이드간 간격, 유로 형상각 등 여러 형상 변수에 대해 통과유동계산 및 손실계산을 수행한다. 익형 설계는 유로 설계시 스팬 방향으로 계산된 입출구 유동각을 기준으로 실험상관식을 적용하여 최적의 블레이드 개수를 결정한 후 2D 익형 단면을 설계하며 2D NS 계산을 통해 캐스케이드 유동구조를 검토하여 설계한 단면의 설계적정성을 평가한다. 설계된 2D 익형 단면을 스팬방향으로 적층하여 3D 익형을 생성하고, 다단 Euler 계산, 단익렬, 다단 NS 계산을 수행하여 3D 유동 특성을 고찰한다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2011년도 제36회 춘계학술대회논문집
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• pp.61-65
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• 2011

본 연구에서는 초음속 충동형 터빈의 노즐에서 나타나는 유동의 과소 과대팽창 문제를 최적화 기법을 이용하여 비대칭형상을 포함해 설계함으로써 개선시키고자 하였다. 노즐 형상 설계를 위해 8개의 설계변수를 설정하였으며 목적함수로는 후류 영역 출구까지의 정효율이 최대가 되도록 하였다. 최적화에는 iSIGHT-FD가 사용되었으며 근사최적화를 위한 방법으로는 Radial Basis Function을 이용하였다. 노즐유동의 계산에는 상용 코드인 FLUENT 6.3을 사용하였으며 개선된 노즐의 정효율은 기존 대비 1.35% 증가하였고 손실계수는 19.85% 감소하였다.

• Tribology and Lubricants
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• 제38권5호
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• pp.213-221
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• 2022

This paper presents performance measurements of pressure drop and leakage flow rate of test flat seals with asymmetric inclined grooves. This study aims to reveal the influence of groove shapes, often machined in radial film riding-face seals, in forming a hydrodynamic wedge on leakage performance. A test facility was developed, and test seals were manufactured to study the effects of the inlet pressure level, ratio of inlet to outlet pressure, seal groove length, and seal groove height on the steady-state pressure drop and leakage performance. A series of tests were conducted, and the test data were compared to the predictions from a simple and efficient mathematical model using a one-dimensional Reynolds equation. The test results revealed that an increase in the inlet pressure increased the pressure drop through the test seals. The leakage flow rate increased significantly as the inlet pressure and ratio of the inlet to outlet pressure increased. The groove shape also affects seal performance. An increase in the groove length and height resulted in an evident increase in the leakage flow rate. The simple model predictions underestimated the leakage flow rates but showed good agreement with the trend in the measurements for all test operating conditions and changes in the groove shape.