Flow boiling CHF enhancement by wettability and flow conditions in a slug flow in the rectangular curved channel

Park, Hae Min,Jeong, Yong Hoon Elsevier 2018 Experimental thermal and fluid science Vol.91 No.-

<P><B>Abstract</B></P> <P>Critical heat flux (CHF) experiments are conducted to investigate the flow boiling CHF enhancement by additives and a heater material for a wide range of exit qualities and void fractions and for pressure conditions of 1 and 2 bar using the rectangular curved flow channel. For the wettability improvement to enhance the CHF, the additives of boric acid and tri-sodium phosphate (TSP, Na<SUB>3</SUB>PO<SUB>4</SUB> 12H<SUB>2</SUB>O) and the heater material of low alloy steel (SA508) are used. The trend of the CHF enhancement in terms of the flow conditions is discussed for the slug flow regime. The CHF is observed in the bubbly-slug and slug flow through flow visualization works. For each condition of pressure, the CHF is enhanced in most of the experimental cases under relatively high exit quality condition due to the improvement effect of surface wettability. The CHF is not enhanced under the relatively low exit quality condition, because the sufficient liquid supply outplays the difference of wettability. The relationship between CHF enhancement ratio and exit quality, which is observed in each pressure condition, is not effective in comparison with those for the different pressure condition. The void fraction is additionally considered to discuss the CHF enhancement according to void condition. The CHF enhancement ratio is clearly varied by the void fraction for all pressure conditions. The CHF enhancement ratio is proportional to the void fraction for the void fraction of ∼0.5 and above, and it is close to 1 in the void fraction of ∼0.5.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The CHF enhancement by the wettability improvement for the slug flow is studied. </LI> <LI> The wettability is improved by additive deposition and carbon steel oxidation. </LI> <LI> Under the pressurized condition, the CHF is enhanced by the good wettability. </LI> <LI> The effect of wettability is minimized in the low void condition. </LI> <LI> The void fraction is an important factor for the wettability effect. </LI> </UL> </P>

金春洙 詩에 나타난 濕潤性 想像力 考察

전명환 한국어문교육연구회 2022 어문연구(語文硏究) Vol.50 No.4

This article traced the wettability-imagination that appears in Kim Chun-su’s poetry based on his biography, starting from the problem that Kim’s attempts to explain poetry largely relied on the terms and theories suggested by the poet. Wettability is a property that allows a liquid to spread on a solid surface. In Kim’s poems, things are mainly expressed in a “wet” state. This water-based sense of wetness is related to weather phenomena and “Hallyeosudo,” a key poem, reveals his sea experiences. To analyze the sense of wetness and the wettability-imagination, this article borrowed Bachelard’s imagination theory of water and named the principle of composition of a poetic device that reveals a faint sense of connection and depression in Kim’s poems wettability-imagination. The concept of wettability-imagination has two implications and suggests follow-up research to reveal important aspects of Kim’s poetry. The first implication is that Kim created a channel to explain poetry besides the terms and theories planned by the poet. He pointed to the experience in Tongyeong, which connected his childhood and poetic imagination, and the (un)consciously emphasized the Sedagaya Police Station detention experience. The second implication is that the poet’s wettability-imagination was both an expression technique and a poetic subject used as an alibi to dilute desire in relationship and sexuality, creating a stance to avoid the problem of desire even though he continued to pursue the possibility of connection and communication. These findings would assist new research beyond the perspective of pure poetic expression or aestheticism in Kim Chun-su’s poetry. 전명환, 2022, 김춘수 시에 나타난 습윤성 상상력 고찰, 어문연구, 196 : 351~381 이 글은 김춘수의 시세계를 해명하는 연구가 대체로 시인 스스로 제시한 용어나 이론에 주로 의존하고 천착해왔다는 문제의식에서 출발해 시인의 전기적 생애를 바탕에 두고 시에 나타난 습윤성(濕潤性)의 상상력을 추적했다. 습윤성이란 고체 표면에 액체가 퍼질 수 있도록 하는 성질로, 김춘수의 시에서는 주로 사물이 ‘젖은’ 상태에서 발현된다. ‘수성(水性)’의 감각은 그의 바다 체험을 드러내는 핵심 시어인 한려수도뿐 아니라 기상 현상과도 연관된다. 수성의 감각과 습윤성의 상상력을 분석하고자 이 글은 바슐라르의 물에 대한 상상력 이론을 차용하여 김춘수 시에서 희미한 연결감과 우울의 정서를 드러내는 시적 장치의 구성 원리를 습윤성 상상력으로 명명하였다. 습윤성 상상력이라는 개념은 김춘수의 시세계를 밝혀나가는 데 도움이 되는 두 가지 시사점과 후속 연구의 가능성을 찾아내었다. 하나는 김춘수가 (무)의식적으로 강조하는 세다가야서 구금 경험 이외에 그의 유년과 시적 상상력을 연결할 통영에서의 실체험을 지목해 시인이 기획한 용어나 이론 이외의 시세계를 해명할 통로를 만들었다는 점이다. 또 하나는 시인의 습윤성 상상력이 단순히 표현 기법이 아니라 시적 주체가 관계성과 섹슈얼리티의 문제에서 욕망을 희석시키는 알리바이로 활용되어 그가 지속적으로 연결과 소통의 가능성을 추구하고 있음에도 이를 욕망의 문제에서 회피시키는 관조의 자세를 연출하고 있음을 발견했다는 점이다. 이러한 발견은 김춘수 시에 관한 순수시적, 유미주의적 관점을 넘어서는 새로운 연구 흐름에 기여할 것이다.

The effect of electrolyte wettability on reforming catalyst in direct ethanol MCFC

Hary Devianto,Zhenlan Li,윤성필,한종희,남석우,임태훈,이호인 한국물리학회 2010 Current Applied Physics Vol.10 No.2

To overcome the poisoning of reforming catalyst contacted with the electrolyte without degradations of performance and long-term stability, we proposed on the development of support which has low wettability to electrolyte, but still keeps high activity on steam reforming of bio-ethanol. To perform the wettability measurement, a couple of supports (MgO and PbO) were pressed to form disc-shaped specimen with relatively low porosity, and subjected to an on-line optical contact angle measurement device at MCFC operating condition. The results of wettability of the supports indicated that PbO showed low wettability to the carbonates melts giving high contact angle. The microstructure of unreacted PbO layer might be contributed to its low wettability. The highest activity was achieved with Ni/MgO, while the lowest wettability was attained with PbO as a support. Ni/1MgO·1PbO seemed to be the most promising candidate for avoiding the reforming catalyst from poisoning.

The effect of electrolyte wettability on reforming catalyst in direct ethanol MCFC

Devianto, H.,Li, Z.,Yoon, S.P.,Han, J.,Nam, S.W.,Lim, T.H.,Lee, H.I. Elsevier 2010 CURRENT APPLIED PHYSICS Vol.10 No.2

To overcome the poisoning of reforming catalyst contacted with the electrolyte without degradations of performance and long-term stability, we proposed on the development of support which has low wettability to electrolyte, but still keeps high activity on steam reforming of bio-ethanol. To perform the wettability measurement, a couple of supports (MgO and PbO) were pressed to form disc-shaped specimen with relatively low porosity, and subjected to an on-line optical contact angle measurement device at MCFC operating condition. The results of wettability of the supports indicated that PbO showed low wettability to the carbonates melts giving high contact angle. The microstructure of unreacted PbO layer might be contributed to its low wettability. The highest activity was achieved with Ni/MgO, while the lowest wettability was attained with PbO as a support. Ni/1MgO.1PbO seemed to be the most promising candidate for avoiding the reforming catalyst from poisoning.

Effect of asymmetric wettability in nanofiber membrane by electrospinning technique on separation of oil/water emulsion

Bae, Jiyeol,kim, Hayoung,Kim, Kwang Soo,Choi, Heechul Elsevier 2018 CHEMOSPHERE - Vol.204 No.-

<P><B>Abstract</B></P> <P>Oil/water separation is an important issue in the environmental field because of increasing worldwide oil pollution. In particular, emulsion under 20 μm in size causes a serious problem in water treatment. Thus, development of an effective oil/water emulsion separation membrane is required. Asymmetric wettability is one effective technique for emulsion separation due to its directional liquid transport property. In this research, wettability was controlled by adjusting the diameter of an electrospun nanofiber for a difference in surface roughness. Through analysis of the surface structure and contact angle of nanofibers with various diameters, the contact angles of fibers with different diameters were increased about 40° to confirm that surface structure affects surface wettability. Comparison of asymmetric wettability membranes (AwENMs) and a single membrane (ENM) for oil/water emulsion separation shows that AwENMs perform about two times faster and reject 10% of emulsion.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Asymmetric wettability membrane was fabricated by electrospinning. </LI> <LI> Wettability can be controlled by electrospinning parameter control. </LI> <LI> Oil/water separation process can be driven by gravity using AwENM. </LI> </UL> </P>

High-resolution conductive patterns fabricated by inkjet printing and spin coating on wettability-controlled surfaces

Lee, Changkyu,Kang, Byung Ju,Oh, Je Hoon Elsevier S.A. 2016 Thin Solid Films Vol.616 No.-

<P><B>Abstract</B></P> <P>In this study, we develop a simple and low-cost surface wettability patterning based on soft lithography processes such as nano-imprint lithography (NIL) and micro-contact printing (μCP) to fabricate high-resolution conductive patterns using two different solution processes: inkjet printing and spin coating. An epoxy-based photoresist layer was imprinted by an elastomeric stamp during the NIL process to produce negative micro-structures in the epoxy-based photoresist layer. To form surface wettability contrast, a hydrophobic fluorocarbon film was transferred onto the top surface of the imprinted epoxy-based photoresist layer using μCP. The epoxy-based photoresist layer was UV-treated before the μCP process in order to increase surface wettability contrast; the hydrophilic imprinted patterns surrounded by hydrophobic surfaces were fabricated in the epoxy-based photoresist layer. After printing Ag ink on the imprinted epoxy-based photoresist layer, high-resolution printed line array and square spiral patterns with line width and gap distance of several micrometers can be fabricated with an aid of high surface wettability contrast. Even though well-defined high-resolution conductive patterns with electrical resistivity lower than 6μΩcm can be obtained regardless of the solution processes, inkjet printing seems more efficient from the viewpoint of the amount of ink used in each solution process. The surface wettability patterning suggested in this study is expected to be used in the fabrication of high-resolution conductive patterns in printed electronics.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Surface wettability patterning was performed using soft lithography process. </LI> <LI> Thickness of fluorocarbon films should be controlled to fabricate well-defined patterns. </LI> <LI> Precise positioning of printed ink is not necessary due to the lift-off process. </LI> <LI> Both inkjet printing and spin coating can produce high-resolution patterns. </LI> <LI> Electrical resistivity of the ~7μm wide pattern is lower than 6μΩcm. </LI> </UL> </P>

표면 처리 방법에 따른 타이타늄의 미세 표면 거칠기, 표면 젖음성, fibronectin 흡착량에 미치는 영향

신화섭,김영수,신상완,Shin Hwa-Sub,Kim Young-Su,Shin Sang-Wan 대한치과보철학회 2006 대한치과보철학회지 Vol.44 No.4

Purpose: This study aims to get the fundamental data which is necessary to the development direction of implant surface treatment hereafter, based on the understanding the surface structure and properties of titanium which is suitable for the absorption of initial tissue fluid by researching effects of additional surface treatments fir sandblasted with large git and acid-etched(SLA) titanium on surface micro-roughness, static wettability, fibronectin adsorption Materials and Method: In the Control groups, the commercial pure titanium disks which is 10mm in diameter and 2mm in thickness were treated with HCI after sandblasting with 50$\mu$m $Al_2O_3$. The experiment groups were made an experiment each by being treated with 1) 22.5% nitric acid according to SLA+ASTM F86 protocol, 2) SLA+30% peroxide, 3) SLA+NaOH, 4) SLA+ Oxalic acid, and 5) SLA+600$^{\circ}C$ heating. In each group, the value of Ra and RMS which are the gauges of surface roughness was measured, surface wettability was measured by analyzing with Sessile drop method, and fibronectin adsorption was measured with immunological assay. The significance of each group was verified by (SPSS, ver.10.0 SPSS Inc.) Kruskal-Wallis Test. (α=0.05) And the correlation significance between Surface micro-roughness and surface wettability. surface roughness and fibronectin adsorption, and surface wettability and fibronectin adsorption was tested by Spearman's correlation analysis. Result: All measure groups showed the significant differences in surface micro-roughness, surface wettability, and fibronectin adsorption. (p<0.05) There was no significance in correlation among the surface micro-roughness, surface wettability, and fibronectin adsorption. (p>0.05) Conclusion: Surface micro-roughness and surface wettability rarely affected the absorption of initial tissue fluid on the surface of titanium.

Wettability and Adhesion performance of Urea-Formaldehyde Resins on Wood Surface Depending on Resin Properties

( Minjeong Kim ),( Byung-dae Park ) 한국목재공학회 2022 한국목재공학회 학술발표논문집 Vol.2022 No.1

It is well known that the resin properties such as viscosity, molecular weight (MW) and molecular weight which are also known to influence the adhesion can influence the wettability of a wood surface. However, the relationship between the molecular weight and wettability of UF resins is not completely explained. This study examines the effects of molecular weight on interphase adhesion, surface adhesion, and adhesion performance on wood as well as wettability. Low-MW (LMW), middle-MW (MMW), and high-MW (HMW) UF resins with two formaldehyde/urea (F/U) molar ratios (1.0 and 1.6) were employed for this study. As the MW increases, the 1.0 UF resins have stronger surface tension than 1.6 UF resins. The contact angle and surface adhesion of UF resins on earlywood (EW) and latewood (LW) from sapwood (SW) and heartwood (HW) before and after extractives removal were highly dependent on the surface roughness rather than on the surface tension. On the other hand, interphase adhesion is more affected by the F/U molar ratios than the surface properties due to the extractives. However, the 1.0 UF resins showed maximum interphase adhesion at HMW, whereas the 1.6 UF resins provided the strongest interphase adhesion at MMW.

유리섬유직물에 대한 수지의 젖음성 평가

한승욱 ( Seung Wook Han ),최낙삼 ( Nak Sam Choi ),이민수 ( Min Soo Lee ),안흥근 ( Hung Kun Ahn ) 한국복합재료학회 2011 Composites research Vol.24 No.2

에폭시 수지와 유리섬유직물 간의 젖음성을 분석하였다. 에폭시 수지와 산무수물 경화제의 혼합비는 당량비 1:0.5, 1:1, 1:1.2로 하였고, 촉매는 혼합된 수지의 0.1wt%로 첨가하였다. DSC 경화거동분석 결과 이 혼합 수지는 상온에서 함침이 가능하였다. 혼합 수지에 대해 유리평판에 놓여진 유리섬유직물 위에 수지 한 액적(방울)을 투하 후 시간에 따른 접촉각 변화를 측정하였다. 또한, 일정량의 에폭시 수지 액적을 투하시켜 시간에 따른 젖음면적 변화를 측정하였다. 접촉각, 액적높이, 순수 젖음면적, 젖음계수를 측정함으로써 유리섬유직물에 대한 에폭시 수지의 젖음성을 비교 평가하였다. 그 결과 당량비 1:1.2에서 유리섬유직물에 대한 젖음성이 가장 우수하였다. Analysis of wettability between epoxy resin and glass fabric was studied. The mixing ratios of epoxy resin and anhydride hardener were varied as 1:0.5, 1:1 and 1:1.2. Catalyst content was fixed as 0.1wt% of the mixed resin. A curing analysis by differential scanning calorimeter(DSC) showed a possible impregnation of the mixed resin at the room temperature. An effective contact angle of the mixed epoxy resin drop onto the glass fabric being preset on a flat glass plate was measured as a function of time. The wet area of the epoxy resin drop was also measured. Behaviors of the contact angle, the droplet height, the neat wet area and the coefficient of wettability were used to evaluate the wettability of the epoxy resin onto the glass fabric. It was concluded that the equivalent ratio of 1:1.2 was the most suitable for the wettability.

Effect of Pitch Wettability in the Impregnation Process

안정래,김병주,이상원 한국공업화학회 2020 한국공업화학회 연구논문 초록집 Vol.2020 No.-

In this study, the effect of the pitch wettability change with temperature during the carbon block impregnation process was studied. The upper chamber was heated above the softening point to melt the pitch and control the wettability. The lower chamber was kept at the same temperature as the upper chamber during the vacuum treatment and then at 340°C, 360°C and 380°C during impregnation. The impregnated carbon blocks were heat treated for 1 hour while maintaining the temperature at 1,100°C. in a nitrogen atmosphere. The element content of the pitch and the viscosity at each temperature were measured using an element analyzer and a viscometer. The internal shape, thermal conductivity and density of the carbon blocks were measured by scanning electron microscopy, hot disk method and Archimedes method. As a result of the experiment, the higher the wettability of the pitch, the higher the density and thermal conductivity of the carbon block and the denser the internal shape.