• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.10
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• pp.6445-6452
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• 2015

The surface of the cooling coil becomes dry, wet or partially wet depending on the operating condition. Thus, a proper design of the cooling coil should include a heat transfer analysis on dry, wet or partially wet surfaces. In this study, an elementary model, which analyzes the cooling on an elementaty basis, is proposed. Comparison of the predictions of the model with experimental data of the cooling coil revealed that heat transfer rates were predicted within 10.1%, airside pressure drop within 11.1% and sensible heat ratio within 5.7%. The model was used to investigate the effect of water circuitory on cooling coil performance.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.12
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• pp.8165-8175
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• 2015

In Korea, summer is hot and humid, and air-conditioners consume lots of electricity. In such case, simultaneous usage of indirect evaporative cooler may reduce the sensible heat and save the electricity. In this study, heat transfer and pressure drop characteristics of indirect evaporative cooler made of aluminum, plastic, plastic/paper are investigated both under dry or wet condition. Results show that indirect evaporation efficiencies of the plastic/paper sample (38.5% ~ 51.4%) are approximately the same as those of the aluminum sample (41.9% ~ 47.5%), and are larger than those of the plastic sample (29.0% ~ 37.4%). This suggests that the plastic/paper sample could be a good substitute to the aluminum sample. However, the pressure drops across the paper channel are 92% ~ 106% larger than those across the aluminum channel. The heat transfer coefficients of the paper channel under dry condition are 15% ~ 44% larger than those of the plastic channel. The increases are 185% ~ 203% for the aluminum channel. The pressure drops of the paper channel are 34% ~ 48% larger than those of the plastic channel and 93% ~ 106% larger than those of the aluminum channel. Rigorous heat transfer analysis reveals that, for the plastic sample, 30% ~ 37% of the wet channels remain dry, whereas all the channels are wet for plastic/paper sample. For aluminum sample, the ratio is 17% ~ 23%.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.3
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• pp.218-229
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• 2004

In this study, dry and wet surface pressure drop and heat transfer characteristics of heat exchangers having plain fins were investigated. Nine samples having different fin pitches and rows were tested. The wet surface heat transfer coefficient was reduced from experimental data using enthalpy-potential method. The wet surface heat transfer coefficients were approximately equal to the dry surface values except for one row configuration. For one row configuration, the wet surface heat transfer coefficients were approximately 30% lower than the dry surface values. For the pressure drop, the wet surface yielded approximately 30% higher values compared with the dry surface counterpart. Data were compared with existing correlations.

• Journal of Energy Engineering
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• v.16 no.1 s.49
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• pp.7-14
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• 2007

An experimental study is performed to investigate the effect of air-side heat transfer and friction on characteristics of finned tube heat exchanger under dry surface and wet surface conditions (RH 50%, 70%). Air enthalpy calorimeter is used to obtain the performance evaluation and analysis of a fined tube heat exchanger. Four finned tube heat exchangers with slit fin or plain fin are tested. The number of tube rows are 2 and 3, and the tube diameter is 7 mm. Air-side heat transfer and friction are presented in terms of j factor and friction factor. At dry surface condition, j factor decreases with increasing Re and j factor of 3 row is lower than that of 2 row. Also, the friction factor of a slit fin is larger than that of a plain fin. At wet surface condition, the heat transfer effect is more significant in the case of the slit fin than the plain fin and 2 row than 3 row. The j factor and friction factor are affected by humidity, tube row and fin configuration.

• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.2
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• pp.244-250
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• 2019

We investigated the relationship between morphological characteristics and individual dry weight to develop a method for estimating the individual dry weight of sheet form macroalgae: Ulva australis, Ulva linza, Pachymeniopsis lanceolata, and Pyropia yezoensis. In Total, 319 thalli of various sizes were collected at six sites from February 2017 to December 2018. An interspecific allometric exponent of 0.28 was found for length-biomass allometry in four sheet form macroalgae, corresponding to a 1/4-power law for primary producers. The relationships between surface area and individual dry weight, as well as between individual fresh weight and individual dry weight, were found to fit significantly using linear regression equations. This explained 94-99 % of individual dry weight, indicating that surface area and individual fresh weight can be used to accurately estimate individual dry weight. We propose the use of this method when experimental processes do not allow individual dry weight to be measured directly, so researchers can save both time and expense.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.10
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• pp.781-785
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• 2002

The effects of different surfaces on dry and wet frosting test were experimentally investigated. The results of experiment were compared by the performance evaluation coefficient (PEC). Results showed that the air-side pressure drop of lacquer coated evaporator increased by 5% as compared to the plasma treated one. It was also found that the Plasma coated evaporator is lower than lacquer coated one in the PEC ratio.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2001.06a
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• pp.54-54
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• 2001

End hall type 이온건을 이용하여 다층 다이아몬드상 차본(DLC) 필름을 M2 steel 기판 위에 합성하였다. 다충 다이아몬드상 카본 필름은 순수 DLC 필름과 실라콘 함유 D DLC 필름의 조합으로 구성되어 있으며, $C_6H_6$ 및 수소 희석된 30% 를 사용하여 증착 하였다. 생성된 DLC 박막의 조성은 $C_6H_6$과 $SiH_4$ 가스의 비를 조절함으로써 변화시켰으며, 250 kHz의 고주파 전원을 바이어스 전원으로 사용하여 박막의 물성을 변화시켰다. DLC 박막의 두께와 다층의 구조 및 종류(2충, 4충)는 코팅 공정의 실험 변수로서 변화시켰다. 직경 3 mm의 루비볼을 사용하여 ball-on-disk 방식으로 마모 시험을 행하였으며, 하중은 490 g, 500 rpm에서 상대습도를 5 % 이하와 80 % 이상으로 변화시켜가며 시행하였다. 100,000 cycle 회전 후 측정된 시편의 마모상태는 5 % 이하의 습 도에서 4층 구조의 박막이 2충 구조의 박막보다 2배 이상 낮은 마모률을 보였으며 그 값은 각각 $2~3{\times}\;10^{-8}\;\textrm{mm}^3/rev$와 $1~2{\times}\;10^{-7}\;\textrm{mm}^3/rev$로 나타내었다. 80% 이상의 습도에서도 마모률의 변화는 저습에서의 경우와 유사하였다. 또한 Si함유 DLC 다층 박막이 저습 및 고습에서 더욱 안정한 마찰 마모 거동을 보였다.

• Journal of the Korean Society of Clothing and Textiles
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• v.33 no.12
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• pp.1873-1882
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• 2009

Hospital patient clothing material was treated with a mixture of chitosan in order to enhance functionality, such as the durability and dimensional stability of the cotton fabric used. Chitosan is a natural polymer with excellent biocompatibility, however there is a deteriorating adherence efficiency. The addition of a nanosilver colloidal solution in accordance with a prescribed ratio can further increase the performance of chitosan. Changes in the structural characteristics and physical properties of the chitosan/nanosilver treated fabric were observed in a comparison with fabric treated only with chitosan. The add-on ratio increased when the mixing ratio of nanosilver colloidal solution was higher; however, the crystalline structure of the treated fabric remains similar. In the case of CH3/NS1 treated fabric (where the mixing ratio of chitosan and nanosilver solution was 3:1) the K/S value, whiteness index, wet tensile strength, and wrinkle recovery angle were superior. The dimension stability, pilling resistance, and abrasion resistance of the fabric treated with a mixed solution increased in comparison to the fabric treated only with chitosan. The chitosan/nanosilver treated cotton fabric used for patient clothing material has excellent physical properties.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.21 no.1
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• pp.11-15
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• 1988

Square slices of sea tangle was dried in constant condition of thickness (1.54mm), air temperature $(50^{\circ}C)$, relative humidity $(30\%)$ and air velocity (0.4m/s). The shrunk surface area and the shrinking rate were investigated. The results obtained are summarized as follows : 1) Comparing the shrinking of transverse section with that of vertical section, the transverse section was proceeded more double shrinkage than vertical section. 2) The shrunk surface area curve showed nearly a linear shrinkage up to 90min of drying time. 3) The shrinking rate was rapidly increased in first falling rate period, and was largest in the early period of second falling rate period.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.65-65
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• 2018

갈바륨 도금강판은 알루미늄의 우수한 차폐 특성과 내열성, 열 반사성을 가지며 아연의 희생방식 특성을 겸비하여 동일 부착량의 용융 아연도금 및 알루미늄 도금강판에 비해 우수한 내식성을 나타낸다고 알려져 있다. 또한 이것은 표면이 미려하고 경제성이 높아 건자재 용도로 현재까지도 세계적으로 널리 이용되고 있다. 여기서 지칭하는 바륨 도금강판(galvalume steel)은 아연과 알루미늄 도금강판의 장점을 접목하기 위해 55 Al-43.4 Zn-1.6 Si (wt.%)로 구성되어 개발된 3원계 성분의 합금도금강판이다. 한편, 최근에는 강재의 내식성을 향상시키기 위한 다양한 연구 결과에 의해 Zn-Al-Mg의 3원계 합금도금강판도 개발되어 사용되고 있다. 이것은 기존의 아연도금 강판 보다 10배 정도의 우수한 내식성을 나타내는 것으로 보고되고 있다. 특히, 이것은 도금된 평판부의 내식성은 물론 절단된 도금 단면부의 내식성도 매우 우수하다고 알려져 있다. 그러나 상기한 갈바륨 도금강판의 경우에는 도금된 표면부에 비해 단면부의 내식성이 상대적으로 취약한 것으로 알려져 있다. 따라서 본 연구에서는 갈바륨 도금강판의 내식성을 종합적으로 향상시키기 위하여 이 갈바륨 도금강판 상에 PVD 스퍼터링법에 의해 Mg 코팅막의 제작을 시도하였다. 여기서 Mg 코팅막은 후처리 된 갈바륨 도금강판 상에 Ar 공정압력 2 및 20 mTorr 조건 중 1.5 및 $3{\mu}m$ 두께로 제작하였다. 또한 제작한 코팅막에 대해서는 모폴로지 관찰(SEM) 및 결정구조 분석(XRD)을 하였고, 분극측정, 염수분무 시험(SST) 및 복합부식 시험(CCT)에 의해 표면 및 단면부의 내식성평가를 수행하였다. 또한 여기서는 염수분무 및 복합부식 시험 후의 시험편도 채취 하여 표면 및 단면부위에 대한 원소조성 분석(EPMA)과 결정구조 분석(XRD)을 실시하였다. 이상의 실험 결과에 의하면, 본 실험에서 제작한 Mg 코팅막은 그 두께가 두꺼울수록 표면 Mg 결정립의 크기가 증가하였고, 그 부식속도가 증가하는 경향을 나타내었다. 또한 여기서는 공정압력이 높은 조건에서 제작한 막일수록 Mg(002)면 피크 강도가 감소하고 Mg(101)면 피크의 배향성이 증가하였다. 그때 그 막의 내식성은 향상되는 경향을 나타내었다. 그리고 종합적으로 염수분무 및 복합부식 시험 결과에 의하면 Mg이 코팅된 갈바륨 도금강판은 기존 갈바륨 도금강판 보다 내식성이 현저히 향상되었다. 특히, 단면부 내식성의 경우에는 기존 대비 5배 이상 향상되는 경향을 나타내었다. 여기서 단면부 내식특성 분석을 위한 EPMA 원소조성 분석 결과에 의거하면, 부식 초기에는 마그네슘의 부식생성물에 의해 단면부가 치밀하게 보호되고 있음을 확인할 수 있었다. 그 이후에는 부식이 지속적으로 진행됨에 따라 갈바륨 도금층에서 용출된 알루미늄 및 아연 성분이 마그네슘과 함께 치밀한 부식생성물을 형성하여 단면부를 차폐함에 따라 단면부의 내식성이 크게 향상된 것으로 생각된다. 이러한 부식생성물의 결정구조 분석 결과에 따르면, 염수분무와 복합부식 시험에서는 공통적으로 MgO, $Mg(OH)_2$ 이외에도 Simonkolleite상 등이 형성되었다. 또한 건-습 반복 부식시험인 복합부식시험 후에는 $Mg_5(CO_3)_4(OH)_24H_2O$(Hydromagnesite)상 등이 형성됨을 확인할 수 있었다. 즉, 본 실험에서 후처리된 갈바륨 도금강판 상에 제작한 마그네슘 코팅막의 경우에는 상기와 같은 다양한 부식반응에 의해 표면 및 단면부에 형성된 Mg계 부식생성물과 $Zn_5(OH)_8Cl_2H_2O$(Simonkolleite)상에 의해서 표면은 물론 단면부 내식성이 크게 향상된 것으로 사료된다.