• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.8
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• pp.855-860
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• 2011

We numerically simulated a dissolved air flotation (DAF) tank to predict the performance of the pilot facility. The flow was assumed to be two-dimensional and two-phase. The velocity distributions in the separation zones of differently shaped DAFs were compared to find the effect of the shape on the performance. The results showed that the typical flow pattern that appeared in a well-designed DAF-tank was generated in the separation zone of the base model. This flow pattern could be maintained while the baffle height was sufficiently tall regardless of the other geometric parameters. However, the baffle height and angle, the contact zone width, and the perforated plate affected the uniformity of the downward flow in the separation zone. Except for the baffle height, the base model used in this study showed a better uniformity of downward flow than did other models with different geometric parameters.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.05a
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• pp.1467-1468
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• 2010

• Journal of the KSME
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• v.26 no.1
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• pp.31-35
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• 1986

물질전달이 포함되는 교환기의 설계목표도 단순열교환기의 경우와 마찬가지로 여러 가지 주어진 제약조건(constraints; 예를들면 교환기의 제원이나 유체유동에 필요한 압력부하등)을 만족시키 면서 전달능력의 단위(number of transfer units, 이하 $N_{tu}$ 로 약함)를 최대로 해 주는데 있다. 그러나 교환장치들의 유형이나 형상에 따라 이같은 동일 목적을 위한 과정은 각양각색 이다. 본장에서는 직접 접촉식 교환기의 많은 종류중 물의 직접증발을 이용한 단열가습장치와 고체건조제 단열제습장치등 두가지의 해석과정을 예시하려고 한다.

• Journal of Energy Engineering
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• v.23 no.4
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• pp.189-195
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• 2014

The use of solar energy among renewable energy tends to increase because of its infinity and cleanness of resources. Even though the consumption rate of solar energy in our country is still low, however, in recent years, the research for solar energy have been widely conducted due to policy support of government. This study was performed to investigate the efficiency of heat collection using solar collector with single evacuated tube-type. As the results, the temperature of radiation fin for solar collector with single evacuated tube-type was lower in spite of high temperature of heat pipe compared that of double evacuated tube-type. In order to increase the efficiency of heat collection, it was confirmed that the loss of heat collection due to contact resistance as well as performance improvement for solar collector should be decreased.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.10
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• pp.1297-1303
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• 2013

A nonlinear finite element analysis is performed to evaluate the sealing capability and stress of dust covers for the ball joint of an automotive steering system. The analysis is performed for two types of dust covers: wrinkle type and pot type. The assembly condition and operation condition are analyzed, and the maximum stress and contact normal stress at the ribs are evaluated. It is confirmed that the sealing capability of both types is fairly good, but the wrinkle type is better than the pot type in terms of the maximum stress.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.05a
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• pp.73-79
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• 2002

Fretting wear test in room temperature air was performed to evaluate the wear mechanism of fuel rod using a fretting wear tester, which has been developed for experimental study. The main focus was to compare the wear behaviors of fuel rod against support springs at different contact geometries (i.e. concave and convex) and slip directions (axial and transverse). The wear on the tube was examined by the surface roughness tester, which measures the volume. The result indicated that with change of contact geometry from 5N of normal load to 0.1mm gap, wear volume of tube Increased in the condition of concave spring, but slowly decreased in convex spring. From the results of SEM observation, wear mechanism of each test condition was also depend on the above contact parameters. The wear mechanism of each test condition in room temperature air is discussed.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1994.06a
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• pp.56-64
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• 1994

탄성유체윤활 (elastohydrodynamic lubrication : EHL)이론은 구름 베어링, 기어 및 캠기구 등과 같이 집중 하중을 받는 기계 요소에서의 윤활 현상을 설명하는 이론으로서, 윤활부분에서 금속 접촉이 발생하지 않도록 기계요소를 설계하기 위하여 필요한 최소유막두께를 결정하는 데 사용된다. 그리이스는 대표적인 윤활제로서 구름 베어링의 윤활에 있어서 중요한 위치를 점하고 있다. 현재 집중 하중을 받는 기계 요소의 윤활에는 윤활 구조의 간편화, 보수의 용이성, 먼지나 이물의 침입 방지 등에 유리한 그리이스 윤활의 사용이 확대되고 있다. 현재 전동기, 가정용 전기기기, 측정기 등에 쓰이는 구름 베어링의 경우는 거의 전량 그리이스 윤활이 사용되고 있다. 지금까지의 연구는 유동특성상의 복잡성 때문에 무한장 선접촉 등온 EHL 문제에 대한 해석이었고, 아직까지는 그리이스 윤활 TEHL 해석에 관한 연구는 발표된 바 없다. 본 연구에는 Herschel-Bulkley 모델 그리이스 EHL문제를 열탄성유체윤활해석하여 보다 정확한 접촉부의 압력분포와 유막형상을 예측하고자 한다.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.144-150
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• 2001

Considered is non-symmetric contact traction induced by the tilting of a contact body and/or by a far field bulk tensile load to the other body. The problem is under the regime of plane strain. General profile of the contact end is incorporated and partial slip condition is supposed. As an example contact configuration, an indentation of a punch with rounded corners onto a half plane is studied. The variation of the internal stress field due to the tilting and the bulk tension is investigated. An edge crack problem is analyzed to examine the influence of the non-symmetric traction. It is shown that the tilting of a punch does not influence the behaviour of the crack. Rather, the effect of the bulk tension on the cracking behaviour is found considerable.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1068-1073
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• 2003

Method for contact failure mitigation is studied in this paper. The focus is laid on the contact shape that eventually influences the internal stresses. Contact mechanics is consulted within the frame of plane problem. Hertzian contact, rounded punch and uniform traction profiles are considered. Frictional as well as frictionless contact is also considered. As results, the higher traction profile induced by the rounded punch reveals the greatest among the considered shapes. Therefore, it is suggested to increase the edge radius as large as possible if a contact body of punch shape needs to be designed. It is also found that uniform traction cannot always provide the solution of contact failure mitigation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.12
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• pp.4715-4720
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• 2010

In this study, we developed new tapered rolling type strip pressure key for the prevention of scratch in sheet metal forming line. The developed pressure key is equipped with two tapered rollers inside a conventional block pressure key. Through the scratch test, for the case of transversal movement the tapered rolling type pressure key reduces both friction and depth of scratch by the effect of tapered shape which decreases the pressure spike on edge, and for longitudinal movement the scratch on the sheet metal surface is certainly removed by the rolling contact.