• Journal of Advanced Marine Engineering and Technology
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• v.30 no.1
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• pp.65-72
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• 2006

Heat transfer augmentation in heat exchangers has received much attention in recent years, mainly due to energy efficiency and environmental considerations. Many active and Passive techniques are currently being employed in heat exchangers, with some inserts providing a cost-effective and efficient means of augmenting heat transfer. The Purpose of this paper is to determine the pressure loss and heat transfer characteristics of a heat exchanger using static mixing technology. Experimental measurements were taken on two set-ups: a single tube heat exchanger and a shell-tube heat exchanger with two static mixing inserts. It was concluded that the static mixing inserts resulted in an increase in the pressure loss and heat transfer characteristics as can be expected.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.1046-1051
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• 2004

A plate-fin-tube heat exchanger used for a $SF_{6}$ gas-insulated transformer is extremely important since the dissipation of the heat generated from inside coils has a significant effect on the performance as well as the durability of the transformer. The heat exchanger consists of corrugated plate fins and staggered array tube bundles for coolant. In order to find out heat transfer and pressure drop characteristics, series of numerical analyses for plate fins with enhanced surface geometries were conducted. Based on the results of the numerical analyses, an improved model of the plate fin has been proposed.

• The Korean Journal of Rheology
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• v.9 no.2
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• pp.73-80
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• 1997

분말 입자 형태가 다른 2가지 스테인레스 강(SUS 316L)분말과 조성이 다른 2가지의 결합제를 이용하여 분말충전율의 변화를 가지도록 제조된 5가지 분말사출재에 대한 Bagley 보정 실험을 실시하여 Bagley 보정값에 대한 온도, 분말충전율, 분말 입자 형태 그리고 결 합제의 영향을 조사하였다. Bagley 보정값을 구하기 위한 자료 처리를 하는 과정에서 길이 가 긴 모세관(L/D=60) 의 압력손실이 Thixotropy에 의해서 감소한 현상을 발견하였다. 이는 모세관 점성측정기를 이용한 분말사출제의 점도 측정시 길이가 긴모세관의 사용이 바람직하 지 못하다는 것을 나타낸다. 분말사출재의 Bagley 보정값에 대한 온도와 결합제의 영향은 매우 미약하게 나타났는데 특히 결합제의 영향은 거의 나타나지 않는 것을 발견하였다. 분 말충전율과 분말 입자 형태의 Bagley 보정값에 대한 영향은 매우 크게 나타났으며 분말충 전율이 증가할수록 Bagley 보정값이 증가하고 분말 입자의 형태가 불규칙한 분말을 사용한 분말사출재의 보정값이 구형의 분말에 비해 높은 보정값을 나타냈다. 실험결과에 대한 고찰 결과, 분말사출재의 모세관 입출구에서 압력손실의 주 원인은 분말 이자간 마찰과 충돌이라 고 판단되었다.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.161-164
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• 2006

Three-dimensional flow and aerodynamic loss in the tip-leakage flow region of a high-turning first-stage turbine rotor blade with a squealer tip have been measured with a straight miniature five-hole probe for the tip gap-to-chord ratio, h/e, of 2,0%. This squealer tip has a indent-to-chord ratio, $h_{st}/c$, of 5.5%. The results are compared with those for a plane tip ($h_{st}/c\;=\;0.0%$). The squealer tip tends to reduce the mass flow through the tip gap and to suppress the development of the tip-leakage vortex. Therefore, it delivers lower aerodynamic loss in the near-tip region than the plane tip does. At the mid-span, however, the aerodynamic loss has nearly the same value for the two different tips.

• Journal of Advanced Marine Engineering and Technology
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• v.27 no.2
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• pp.299-304
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• 2003

Static mixer consists of a straight pipe of circular cross section into which individual elements are inserted to cut, fold, twist and re-combine the mixing fluid. The number of elements and their shape required in any application depend on the complexity of the mixing process. The objectives of this study are to develop a new static mixer and to perform the experimental investigation of pressure drop in order to evaluate the performance of the new one. The mixing fluid used is Glycerin. The pressure drop is measured using a hydraulic manometer and the correlation of Z-factor is suggested as a function of Re. The Z-factors of SSC and YNU mixer are about 40% lower than and 4% higher than that of the Sulzer one.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1566-1571
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• 2003

The cold plate used for a CEU(Control Electronics Unit) of an EV(Electric Vehicle) is extremely important since the dissipation of the heat generated from power devices like IGBT(Insulated Gate Bipolar Transistor) and diode has a significant effect on the performance as well as the durability of the CED. The cold plate consists of seven power devices, and coolant flows through the passage bonded to a groove of the cold plate. In order to find out heat transfer and pressure drop characteristics, series of numerical analyses for the cold plate with enhanced coolant passages were conducted. Based on results of the numerical analyses, an improved model of the cold plate has been proposed. The experiments under the various conditions have been conducted to compare the performance of the proposed cold plate to the present one. As a result of the numerical analyses together with the experiments, the ideal design of the cold plate could be offered.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2003.11a
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• pp.63-64
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• 2003

원심력집진기는 장치가 간단하지만 집진효율이 낮아 주로 여과포집진장치 및 전기집진장치의 전단에만 사용되는 단점을 가지고 있다. 여과포집진장치는 고효율의 집진성능을 가지고 있지만 유입되는 먼지의 농도를 감소시키기 위하여 전단에 원심력집진기를 설치하게 되므로 설치공간 및 동력비가 과다하게 소요되고 있으며, 높은 압력손실, 낮은 여과속도에 의한 장치면적 증가, 균일한 집진이 어려워 일부 여과포에 집중적인 부하가 걸리게 되는 단점 등을 가지고 있다. 전기집진장치의 경우 압력손실이 적고 대용량에 적용 가능하지만, 여과집진장치에 비해 집진효율이 낮고, 먼지의 종류 및 연료연소조건에 따라 집진효율이 크게 영향을 받는 단점을 가지고 있다. (중략)

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.786-791
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• 2003

We have studied on the main causes of pressure drop in the paint hose under the spraying with airless spray pump and suggest calculation method for selecting the optimum pressure drop during the spraying. Among many factors contributing the pressure drop during the airless spraying procedure of paint, some of the key factors and the correct method for checking pressure loss between airless pump and spray gun are addressed. We have developed pressure loss calculation method which depending on hose length and diameter, viscosity and flow rate in the painting hose during the spraying. also we have developed calculation equation for the expected spray tip flow rate which depending on pressure and specific gravity and tip size.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.9 s.252
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• pp.913-920
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• 2006

Three-dimensional flow and aerodynamic loss in the tip-leakage flow region of a high-turning first-stage turbine rotor blade with a squealer tip have been measured with a straight miniature five-hole probe for the tip gap-to-chord ratio, h/c, of 2.0%. This squealer tip has a indent-to-chord ratio, $h/{st}/c$, of 5.5%. The results are compared with those for a plane tip $(h_{st}/c=0.0%)$. The squealer tip tends to reduce the mass flow through the tip gap and to suppress the development of the tip-leakage vortex. Therefore, it delivers lower aerodynamic loss in the near-tip region than the plane tip does. At the mid-span, however, the aerodynamic loss has nearly the same value for the two different tips.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.973-974
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• 2014

대형 전동기의 주요 소음원은 전자기 소음과 냉각/통풍 시스템 소음이며, 이 중 냉각/통풍 시스템이 전체 소음에 큰 영향을 미친다. 본 논문에서는 대형 전동기의 저소음 냉각/통풍 시스템 개발을 위해 저소음 냉각 팬을 개발하고 팬 커버 내부의 유로를 개선하였다. 유동해석은 상용 CFD 소프트웨어를 이용하였으며 팬 커버 내의 scroll 형상 및 air guide, baffle 의 유무에 따라 팬 커버의 압력손실을 계산하였다. 해석을 통해 팬 커버 내부의 난류 유동과 압력손실이 가장 작은 팬 커버 형상을 도출하였으며 개선된 냉각/통풍 시스템이 기존 냉각/통풍 시스템보다 6.5dB 감소된 것을 확인하였다.