• 설비공학논문집
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• 제28권7호
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• pp.283-287
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• 2016

One of the most important factors for determining the thermal performance of an evaporative cooling system is the wettability of the evaporative heat exchanger surface. Evaporation of a widely spread water film on the heat exchanger surface promotes heat transfer between the "dry" air and "wet" air passages. Hydrophilic coating is generally applied on the heat exchanger surfaces to increase the wettability of the heat exchanger surface and the COP of the evaporative cooling system. In this paper, a simple lamellar patterned structure is suggested to maximize the spreading of a water film on the vertically oriented walls. The capillary height of the lamellar structured grooves is analyzed through a theoretical model, and the results are compared with the numerical analysis through a finite element analysis tool, SE-FIT. A good agreement between the theoretical model and the numerical analysis can be observed as long as the channel depth is comparable to or larger than the channel width of the lamellar structure.

• Advances in concrete construction
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• 제9권5호
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• pp.437-448
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• 2020

In high rise buildings that utilize precast large panel system for construction, the shear wall provides strength and stiffness during earthquakes. The performance of a wall panel system depends mainly on the type of connection used to transfer the forces from one wall element to another wall element. This paper presents an experimental investigation on different types of construction detailing of the precast wall to wall vertical connections under reverse cyclic loading. One of the commonly used connections in India to connect wall to wall panel is the loop bar connection. Hence for this study, three types of wet connections and one type of dry connection namely: Staggered loop bar connection, Equally spaced loop bar connection, U-Hook connection, and Channel connection respectively were used to connect the precast walls. One third scale model of the wall was used for this study. The main objective of the experimental work is to evaluate the performance of the wall to wall connections in terms of hysteretic behaviour, ultimate load carrying capacity, energy dissipation capacity, stiffness degradation, ductility, viscous damping ratio, and crack pattern. All the connections exhibited similar load carrying capacity. The U-Hook connection exhibited higher ductility and energy dissipation when compared to the other three connections.

• 한국산업융합학회 논문집
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• 제11권4호
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• pp.157-163
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• 2008

The present study investigated the pressure drop and the total frost mass of the louvered fin type heat exchanger, which is widely used at the air-conditioning system. The pressure drop due to the frosting phenomenon and the total frost mass were investigated by changing the wet bulb temperature condition of the inlet air. Hence the brain of 55wt% was used as a cooling solution instead of a common refrigerant. The temperature difference between the brine and the tube outside wall at the outlet of heat exchanger was $10^{\circ}C$, at maximum, higher than that at the inlet of heat exchanger. As the wet bulb temperatures were increased, the pressure drop was linearly increased due to the increment of frost mass. And the increment of heat exchange rate was smaller than that of inlet air enthalpy due to the increment of frost mass. The pressure drop of air side was rapidly increased due to the progress of frosting phenomena. The run time that the pressure drop occurred rapidly was decreased by the growth of frost.

• 한국지열·수열에너지학회논문집
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• 제7권2호
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• pp.51-59
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• 2011

Storage and transfer heat in soils are governed by the soil thermal properties and these properties are therefore needed in many engineering applications, including horizontal ground heat exchanger for ground-coupled heat pumps. This paper presents the measured results of the thermal diffusivity of soils(silica, quartzite, limestone, sandstone, and masonry soils) used for the trench backfilling materials of the horizontal ground heat exchanger. To assess this thermal property, we (i) measure the soil thermal conductivities and volumetric heat capacities using dual-probe method and (ii) compare the estimates from the de Vries method of summing the heat capacities of the soil constituents. The results show that the thermal diffusivity tends to increase as dry soil begins to wet, but it approaches a constant value or even decreases as the soil continues to wet. Measurements made by using the dual-probe method agreed well with independent estimates obtained using the single-probe method.

• Elastomers and Composites
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• 제55권3호
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• pp.167-175
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• 2020

Various studies have been conducted to improve silica dispersion of silica filled tire tread compounds; among them, silica wet masterbatch (WMB) technology is known to be suitable for manufacturing silica filled compounds that have high silica content and high dispersibility. Till now, the WMB study is focused on the natural rubber (NR) or emulsion styrene-butadiene rubber (ESBR) that does not have a silica-affinity functional group, and a study of NR or ESBR having a silica-affinity functional group is still not well known. Unlike the dry masterbatch technology, the WMB technology can solve the problems associated with the high Mooney viscosity when applied to silica-friendly rubber. However, a coagulant suitable for each functional group has not yet been determined. Therefore, in this study, different coagulant applied silica WMB was prepared by applying calcium chloride, sulfuric acid, acetic acid, and propionic acid by using a carboxyl group functionalized reversible addition fragmentation chain transfer ESBR. The evaluation of the WMB compounds revealed that the calcium chloride added WMB compound showed excellent silica dispersion, abrasion resistance, and rolling resistance.

• Nuclear Engineering and Technology
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• 제27권3호
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• pp.281-291
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• 1995

이 연구의 목적은 수동형 격납용기 냉각계통의 용기 바깥표면이 건조 및 습한 조건일때 격납용기 내, 외벽에서 일어나는 열전달과정에 대한 실험적 자료를 얻는데 있다. 시험모델은 AP 600구조에 근거하여 격납용기의 둘레중 60$^{\circ}$부분만을 취하였다. 시험모델의 주요치수는 원형의 값을 대략 10분의 1로 축소한 것이다. 붕괴열을 모의하기 위하여 전기적으로 가열되는 증기발생기를 시험모델내에 설치하였다. 최대열유속은 8.91 kW/$m^2$ 이었다. 두 가지 형식의 시험이 수행되었다. 하나는 수막유동없이 공기만의 자연대류에 관한 시험이고 다른 하나는 수막유동과 공기의 자연대류가 동반된 증발열전달 시험이다. 시험결과 수막유동이 없는 경우 공기만의 자연대류 열전달 능력은 약 1.48 kW/$m^2$ 열유속에서 제한되고 있음을 알게 되었다 또한 수막유동과 공기의 자연대류가 동시에 일어나는 시험에서 열제거 능력은 현저히 향상됨을 알게 되었다 이들 열전달 측정치들을 기존 관계식들과 비교하였다.

• 한국환경과학회지
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• 제14권2호
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• pp.221-230
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• 2005

Catalytic wet oxidation of trichloroethylene (TCE) in water has been conducted using $TiO_2-supported$ cobalt oxides at $36^{\circ}C$ with a weight hourly space velocity of $7,500\;h^{-1}.\;5\%\;CoO_x/TiO_2$, prepared by using an incipient wetness technique, might be the most promising catalyst for the wet oxidation although it exhibited a transient behavior in time on-stream activity. Not only could the bare support be inactive for the wet decomposition reaction, but no TCE removal also occurred by the process of adsorption on $TiO_2$ surface. The catalytic activity was independent of all particle sizes used, thereby representing no mass transfer limitation in intraparticle diffusion. XPS spectra of both fresh and used Co surfaces gave different surface spectral features for each $CoO_x,\;Co\;2P_{3/2}$ binding energy for Co species in the fresh catalyst appeared at 781.3 eV, which is very similar to the chemical states of $CoTiO_x$ such as $CO_2TiO_4\;and\;CoTiO_3$. The used catalyst exhibited a 780.3-eV main peak with a satellite structure at 795.8 eV. Based on XPS spectra of reference Co compound, the TCE-exposed Co surfaces could be assigned to be in the form of mainly $Co_3O_4$. XRD patterns for $5\%\;CoO_x/TiO_2$ catalyst indicated that the phase structure of Co species in the catalyst even before reaction is quite comparable to the diffraction lines of external $Co_3O_4$ standard. A model structure of $CoO_x$ present predominantly on titania surfaces would be $Co_3O_4$, encapsulated in thin-film $CoTiO_x$ species consisting of $Co_2TiO_4$ and $CoTiO_3$, which may be active for the decomposition of TCE in a flow of water.

• 한국구조물진단유지관리공학회 논문집
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• 제22권4호
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• pp.10-18
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• 2018

본 연구는 시멘트 모르타르속에 매입된 철근주위가 건조될 때 불안정한 전류분포의 영향을 측정하고, 교류 임피던스 특성변화에 대한 영향을 고찰하는 것을 목적으로 한다. 건조과정중 철근의 전기화학적 반응을 측정하기 위해, 두 개의 철근이 매입된 3개의 시멘트 모르타르가 실험을 위해 준비되었다. 주요 변수는 20mm 모르타르 두께를 동일하게 가지도록 하여, 두 철근사이의 간격이 10, 20과 30mm가 되도록 하였다. 해양환경에서 콘크리트 구조물속의 철근 부식속도를 가정하기 위해서, 3개의 모르타르 시험체는 15 사이클의 침지-건조환경(해수에서 24시간 침지와 48시간 실온 건조)에 노출되었다. 부식전위의 변화는 건조중에 용존산소의 확산속도 증가로 인해 귀한 방향으로 이동하는 것이 관찰되었다. 침지-건조환경에서 교류 임피던스는 100kHz에서 1mHz까지 측정되었다. 철근과 모르타르사이의 계면상태를 설명하기 위해 이론적 모델이 제안되었으며, 그것은 용액저항, 전하이동저항과 CPE로 구성된 등가회로를 사용하였다. 철근의 부식이 진행됨에 따라, 저주파수 영역에서 확산 임피던스가 나타났다. 침지-건조 환경중 건조과정에서 이송차가 $45^{\circ}$에 가까워지는 현상으로써 전류분포가 불균일해지는 경향을 보였다.

• 한국산학기술학회논문지
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• 제16권4호
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• pp.2415-2423
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• 2015

본 논문은 12.7mm 원관을 변형하여 만든 세장비 0.6(짧은 직경 10.0mm, 긴 직경 16.5mm)의 타원관이 적용된 사인 웨이브 핀-관 열교환기의 습표면 공기측 성능실험에 관한 것이다. 핀 핏치와 열 수를 변화시켜 총 12개의 시료에 대하여 실험을 수행하였다. 타원관에서 핀 핏치 변화에 따른 j, f 인자의 영향은 미미 하였으나, 열수에 따라서는 1row에서 j인자가 가장 낮았다 (가장 높은 2row의 81%). 하지만 원관에서는 1row에서 가장 높게 나타나는 차이점을 보였다. 이는 타원관에 적용된 사인 웨이브 채널의 유동 특성에 기인한 것으로 판단된다. 원관 열교환기와 $j/f^{1/3}$값을 비교한 결과 1열을 제외하고는 타원관 열교환기의 전열성능이 우수함을 알 수 있다. 즉, 타원관 열교환기의 $j/f^{1/3}$값이 원관의 값보다 2열에서 1.6~2.5 배, 3열에서 1.4~2.4 배, 4열에서 1.2~1.8배 크게 나타났다.

• 한국콘텐츠학회논문지
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• 제18권7호
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• pp.245-252
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• 2018

상이동 촉매기법을 기반으로 한 rose bengal 시약은 중성이나 염기성 용액에서 녹지 않는 난용성 염을 형성하는 칼슘을 타겟팅하는 시약으로, 물에 젖은 검체에서 잠재지문 현출시 효과적일 것으로 기대되어 최근 연구가 이루어지고 있다. 그러나 그 동안 선행연구에서는 rose bengal 시약으로 현출된 지문의 형광 특성을 관찰하지 않았을 뿐만 아니라 제시된 시약의 제조법 또한 최적 현출 조건인지 검토되지 않았다. 이에 본 연구는 rose bengal 염료의 최대방출형광을 바탕으로 rose bengal염료와 상이동촉매제(Tetrabutylammonium)의 농도를 달리하여 최적의 시약 조성을 찾고자 하였다. 그 결과 rose bengal과 상이동촉매제의 농도가 각 0.01 M: 0.008 M일 때 가장 효과적인 것을 확인할 수 있었다.