• Journal of Mechanical Science and Technology
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• 제20권11호
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• pp.1942-1949
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• 2006

Typically, condensate forms as droplets on the fin surfaces and may bridge the space between the fin surfaces. This is due to the dry characteristics inherent to the fin surface. The droplets increase the air-side pressure drop. In the case of high air velocities, these droplets may be blown off the fins and entrained in the air stream. To minimize the formation of condensate droplet, the wet ability of the fins must be improved. The carry-over velocity is affected by fin surface characteristics. To avoid carry-over in the air conditioner having the highest air velocity of 1.5 m/sec, the dynamic contact angle (DCA) should be at least lowly under $60^{\circ}$.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.7-12
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• 2000

The purpose of this study is to develop heat transfer analysis program of heat pipe elements and design a revolving heat pipe exchanger by the performance experiment of hot air production by means of middle-temperature waste heat. Experimental variables are the revolution per minute, normal velocity of inlet air and the temperature of waste heat. The revolving heat exchanger has designed as $2^{\circ}$ in inclination angle of heat pipe bundle and as 20% in working fluid quantity and as water in working fluid. Experimental value of the total heat transfer coefficient was $20w/m^2-^{\circ}C$

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.7-12
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• 2003

heat pipe with screen meshed wick. The heat pipe was designed in 200 screen meshs, 500 mm length and 12mm O.D tube of copper, water as working fluid and nitrogen as non-condensible gas. Heat pipe used in this study has evaporator, condenser and adiabatic section, respectively. Experimental data of wall temperature distribution along axial length is presented for heat transport capacity, condensor cooling water temperature change, degrees of an inclination angle, and operating temperature.

• Journal of Chest Surgery
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• 제26권12호
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• pp.969-971
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• 1993

The sternal turnover has a limited use in an asymmetrical funnel chest. However we tried `One-half sternal turnover` as a new operative approach for an asymmetrical funnel chest. Through the bilateral submammary skin incision, median sternotomy was made from xiphoid process to midsternum and extended horizontally. The segment of ribs were cut at the angle of depression. The en-bloc resected chest wall segment contained one-half sternum as well as a part of ribs and left half of rectus muscle. After turning over the en-bloc segment, reapproximation with wiring was done. Sternotomy wound was closed in layer after placing of substernal drainage tube. Postoperatively, the chest wall was stable and the recovery course was uneventful except left-sided minimal pneumothorax which was cured spontaneaously. The patient was discharged on postoperative 14th day.

• Design & Manufacturing
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• 제2권2호
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• pp.43-47
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• 2008

This paper is concerned with the analysis of material flow characteristics of stepped rod forming. The analysis in this paper concentrated on the evaluation of the design parameters for deformation patterns of tube forming, load characteristics, extruded length, and die pressure. The design factors such as punch nose radius, die corner radius, friction factor, and punch face angle are involved in the simulation. The stepped rod forming is analyzed by using a commercial finite element code. This simulation makes use of stepped rod material and punch geometry on the basis of punch geometry recommended by International Cold Forging Group. As radius ratio is large, forming load was reduced but extruded length ratio was increased.

• 한국수정란이식학회지
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• 제33권1호
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• pp.13-16
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• 2018

We observed the external genitalia and uterus of a 24-month-old freemartin Hanwoo. The vulva was smaller than observed in a normal female Hanwoo, while the clitoris was larger in the freemartin. The angle between the external genitalia and the perineum also varied. Upon internal genital examination, the uterus of the freemartin was a thin tube approximately 18 cm in size and had not differentiated into a normal uterus and uterine horns.

• 설비공학논문집
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• 제14권6호
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• pp.485-492
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• 2002

Heat transfer and pressure drop on the air side of a plate-louvered fin heat exchanger with new shape of louver fin have been investigated experimentally. Water is employed inside the flat tube to transfer heat with air for convenience. This problem is of particular interest in the design of a plate-louvered heat exchanger. The effect of air flow rate, water flow rate and water temperature on pressure drop as well as heat transfer in air side are studied in detail. The present results showed a good agreement qualitatively with the previous results in general. Based on the experimental data, f-factor and j -factor correlations of the present louvered-fin are suggested. It is also found that heat transfer could be enhanced with new shape of louver fin, compared with the conventional louvered-fin, while the f-factor remains unchanged.

• 설비공학논문집
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• 제13권10호
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• pp.1017-1024
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• 2001

The optimum shape of header part in a PFHE (parallel-flow heat exchanger) is studied. The optimal values of each geometric parameter are proposed according to their order of influence with varying the four important parameters (the injection angle of working fluid ($\Theta$), the shape of inlet(S), the location of inlet ($y_c/D_{in}$) and the height of the protruding flat tube ( $y_{b/}$ $D_{in}$ )). The optimal geometric parameters are as follows:$\Theta= -21^{\circ}C,\; S=Type\; A \;an\;y_b/D_{in}$/=0. The heat transfer rate of the optimum model, compared to that of the reference model, is increased by about 55%. The optimal geometric parameters ran be applicable to the Reynolds number ranging from 5,000 to 20,000.0.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2009년도 춘계학술대회 논문집
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• pp.199-202
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• 2009

In roll forming process, a sheet metal is continuously progressively formed into a product with required cross-section and longitudinal shape, such as a circular tube with required diameter, wall-thickness and straightness, by passing through a series of forming rolls in arranged in tandem. Tn this process, each pair of forming rolls installed in a forming machine play a particular role in making up the required cross-section and longitudinal shape of the product. In recent years, that process is often applied to the bumper rail in the automotive industries. In this study, a optimal Front Bumper Beam manufacturing technology, model deign and proper roll-pass sequences can be suggested by forming number of roll-pass and bending angle. And also effects of the process parameters on the final shape formed by roll forming defects were evaluated.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 추계학술대회 논문집
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• pp.285-288
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• 2007

In the recent years the using of low-density material such as high-strength Al alloy on the various industries is becoming light-weight. High strength and hollow Al alloy is good material for stiffness and recycling. Therefore the advanced manufacturing technology with Al alloy is continuously required in many industrial fields. In this study simplified hallow rectangular section of Al alloy is analyzed by FE analysis. Bending stress is affected punching and rotating of wing-die. The analysis of press bending is preformed at first. The elastic recovery value of component and stress distribution acting from the result of the bending angle of three types were obtained. The designed precesses were analyzed by the commercial FE code, Deform-3D. Forming dies for each process were designed and prototypes were manufactured by the verified forming process. Some of the important features of design parameters in the press bending were reviewed.