• 대한조선학회논문집
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• 제44권2호
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• pp.55-63
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• 2007

Fins are widely used for roll stabilization of car ferries and passenger ships as well as high performance naval ships. In the present study, model experiments and numerical simulations are performed to investigate the influence of tail blades on the performance of a fin stabilizer for various angles of attack. It is found that a considerable improvement in performance of the fin stabilizer is achieved with adoption of the tail blades. The results can be utilized for the design of a high-lift control surfaces including fin stabilizers.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2001년도 추계학술대회 논문집
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• pp.86-90
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• 2001

Demand of good seakeeping perfomace is increasing for sea going vessels such as cruisers, naval ships and container ships. Especillay roll motion is one of major concerns in evaluation of seakeeping performance due to its large resonace motion. Since large roll resonance motion is mainly arised from inherent small damping. use of additional mechnism to provide roll damping can significantly reduce roll motion. In this paper, a reliable performace evaluation method of fin stabilizer, which is very useful for stabilizing roll motion of mid and high speed vessls, is described. Model test and time domain simulation methods are adopted for performance evaluation in which real operating situation of fin stabilizer can be exactly modelled. Model test and simulation results show good correlations between model test and simulation results.

• 대한설비공학회지:설비저널
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• 제29권10호
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• pp.47-51
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• 2000

최근 룸에어콘이나 패키지에어콘의 에너지 절약, 쾌척성 등에 대환 사용자나 회사로부터의 요구는 더더욱 높아지고 있다. 공조기의 중요한 구성요소 중 하나인 열교환기도 이러한 요구에 대응하여 기술개발이 계속해서 진행되고 있다. 공조용 열교환기를 설계할 때 가장 중요한 과체는 비용이냐 설치성 등의 제약조건올 만족하면서 필요한 교환열량을 달성하기 위해, 요구되는 열 전달계수(K)와 전열면적(A)의 곱인 KA값을 얼마나 확보하는가 하는 점에 있다. 그러나 이 외의 과제, 예를 들어 홴입력, 소음을 억제하기 위한 공기측 통풍저항의 감소, 증발온도에 영향을 마치는 관내압력손실의 감소 등도 중요한 과제이다. KA값 증대와 통풍저항억제를 동시에 판촉하기 위해 공조용 열교환기는 전면면적을 크게 하고 두께를 작게 하여 사용하는 것이 원칙이다. 또, 전열관의 관경도 관 둘레길이와 냉매분배성능 면에서 제약이 발생한다. 이와 같은 배경으로부터 공조용 열교환기는 판경 6~10 mm정도의 전열 관을 20~25mm길이로 배치한 핀튜브형 열교환기가 주류로 되어있다. 여기에서는 공조기에 널리 사용하고 있는 핀튜브형 열교환기에 대한 최근의 기술개발 사례를 소개하고자 한다.

• 설비공학논문집
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• 제15권2호
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• pp.87-94
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• 2003

To reduce the air side pressure drop in air-cooled heat exchanger, tow-in type winglet vortex generators are applied. A specially designed multiple-channel test core was used in the experiments for the various geometry of winglet vortex generators. The proposed tow-in type vortex generator gives significant separation delay, reduces form drag, and removes the zone of poor heat transfer from near-wake of the tubes. The results show the significant pressure drop reduction for the tow-in win91e1 vortex generators with the similar enhancement of the heat transfer as other vortex generator applications in heat exchanger. In the range of Reynolds number of 350 to 2100 the pressure drop decrease 8∼15% and 34∼55% for the in-line and staggered tube banks, respectively, compared to those without vortex generators.

• 설비공학논문집
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• 제8권2호
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• pp.299-306
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• 1996

This work presents an analytical model, so called modified LMTD method, to predict the thermal performance of finned-tube heat exchanger under frosting conditions. In this model, the total heat transfer coefficient and effective thermal conductivity of the frost layer were defined as a function of frost surface temperature. The surface temperature of the frost layer formed on the heat exchanger was calculated through the analysis of the heat and mass transfer process in the air and frost layer. To examine the validity of this analytical model, the computed results from the present model, such as heat transfer rate, frost mass and thickness of frost, were compared with the ones of the expermental work and LMED method.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2018년도 춘계학술대회 논문집
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• pp.123-123
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• 2018

최근 웨어러블 디바이스에 연구가 집중되면서 투명하고 유연한 마이크로 히터의 필요성이 증가되고 있다. 그럼에도 불구하고, 기존의 사용되는 마이크로 히터들은 딱딱하고 불투명하다. 게다가, 기존의 금속성의 마이크로 히터들의 경우 저항이 너무 작아 웨어러블 디바이스에 사용되는 에너지 하베스터로 구동되기에 효율이 떨어지는 경향이 있다. 이 논문에서 우리는 CVD 방식으로 성장된 그래핀으로 열 발생 라인을 패시베이션 레이어로 h-BN을 이용하여 투명하고 유연한 마이크로 히터를 제작하였다. 제작한 마이크로 히터는 균일한 온도 분포와 200도까지의 온도 상승에 걸리는 시간이 4초 정도로 굉장히 좋은 성능을 보유하고 있다. 또한 소비 전력은 39mW 이하로 효율적이다. 또한 기존의 메탈릭 히터에 비해 저항이 굉장히 높기 때문에 웨어러블 에너지 하베스터로 작동하기 적합하다. 또한 미래의 휴대용/웨어러블 개인 전자기기와 무선 헬스케어 제품, 휴대용 환경 센서에도 적용될 것으로 기대한다.

• 설비공학논문집
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• 제14권6호
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• pp.525-531
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• 2002

The effects of different surface hydrophilicity on frosting and defrosting characteristic were experimentally investigated. Mass of frost and water hold-up was measured. Results showed that no significant difference in the frost mass was found between the two different surfaces while the water hold-up of heat exchanger court be reduced by the enhancement of surface hydrophilicity. Also, the defrosting efficiency m hydrophilic surface was improved by 76%. It was expected that hydrophilic heat exchanger could provide the improvements in both thermal-hydraulic performances and system reliability during frost/defrost operating in refrigeration systems.

• 설비공학논문집
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• 제13권9호
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• pp.818-826
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• 2001

In this study, in-situ performance test of a wet surface finned-tube evaporator of an air source heat pump which has a rating capacity of 20RT is carried out. Since test conditions, such as indoor and outdoor air conditions cannot be controlled to satisfy the standard test conditions, experiments are done with the inlet air conditions as they exist, From the experimental data, air side heat and mass transfer coefficients were calculated by the well known heat and mass transfer analogy and tube-by-tube method. since current procedure underpredicted the experimental sensible heat factor(SHF), a proper empirical parameter was introduced to predict the experimental data with satisfactory results. This study provides the method of evaluating the heat and mass transfer coefficients of a wet surface finned-tube evaporator of which in-situ performance test in necessary.

• 설비공학논문집
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• 제26권8호
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• pp.381-387
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• 2014

The off-set strip fins (OSF) have been widely used to construct plate-fin heat exchangers. Conventional OSF is constructed in successive rows of fins. New OSF structure is suggested to have a gap between adjacent rows of fins. The gap is intended to reduce fouling by allowing small objects to flow through fins. The objective of this work is to investigate the performance of off-set strip fins with gap between successive rows. Results showed that the performance of OSF with gap can't be predicted by previous correlation.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2006년도 하계학술발표대회 논문집
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• pp.633-638
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• 2006

This study presents the air side heat transfer and friction characteristics of fin-tube heat exchangers with various fin types. A total of 8 samples of heat exchangers are tested. Fin patterns tested are slit, louver and plate fins. Each fin type has three cases of number of tube rows(N=1, 2, 3) and two different fin pitches. The results are plotted in terms of Colburn j-factor and friction factor f with respect to Reynolds number in the range of 200 to 510.