• Title/Summary/Keyword: Capillary performance

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Characteristics on Spray Cooling Performance on the Micro-Porous Coated Surfaces (마이크로다공성 발열체 표면에서의 액체분무 냉각성능 특성)

  • Kim Yoon-Ho;Choi Chi-Hwan;Lee Kyu-Jung
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.18 no.4
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    • pp.304-311
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    • 2006
  • Experiments on evaporative spray cooling on the square plate heaters with plain or micro-porous coated surfaces were performed in this study. Micro-porous coated surfaces were made by using DOM [Diamond particle, Omegabond 101, Methyl-Ethyl-Keton] method. In case of purely air-jet cooling, the micro-porous coating doesn't affect the cooling capacity. In spray cooling three different flow patterns (complete wetting, evaporative wetting, dryout) are observed on both plain and micro-porous coated surfaces. The effects of various operating conditions, such as water flow rate, particle size, and coating thickness were investigated on the micro-porous coated surfaces. It is found that the level of surface wetting is an important factor to determine the performance of spray cooling. It depends on the balance between absorbed liquid amount by capillary force over porosity and the evaporative amount. The micro-porous coated surface has largest cooling capacity, especially in the evaporative wetting zone. It is found that the effects of liquid flow rate and coating thickness are significant in evaporative wetting zone, but are not in complete wetting and dryout zones.

Effects of Accumulator Heat Exchanger on the Performance of a Refrigeration System (열교환기 내장형 어큐뮬레이터가 냉동시스템의 성능에 미치는 영향에 관한 연구)

  • Kang Hoon;Choi Kwang-Min;Park Cha-Sik;Kim Yong-Chan
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.18 no.5
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    • pp.418-425
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    • 2006
  • An AHX (Accumulator Heat exchanger) consists of a commercial accumulator and an inner heat exchanger located inside of the accumulator. The AHX is used in multi air-conditioners to assure that liquid-phase refrigerant enters into the expansion device. This purpose is achieved by heat transfer between the refrigerant leaving the evaporator and the refrigerant leaving the condenser. In this study, the effects of AHX on the performance of a refrigeration system using R-22 were measured and the test results were analyzed. The operating characteristics of the refrigeration system with the AHX are considerably different from those without the AHX. Therefore, it is required to determine optimum refrigerant charge and optimum operating conditions when the AHX is used in the refrigeration system having a constant flow-area expansion device such as capillary tube.

A Study of the Development of Liquid-liquid Static Contactor Using Capillary Phenomena Induced by Highly Packed Fiber Bundle and its Characteristics (고밀집 섬유 집합체에 의해 유도된 모세관 현상을 이용한 정적 액-액 접촉장치의 개발과 그 특성 연구)

  • Kim, Kwang-Wook;Byeon, Kee-Hoh;Lee, Eil-Hee;Yoo, Jae-Hyung;Park, Hyun-Soo
    • Applied Chemistry for Engineering
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    • v.7 no.4
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    • pp.743-749
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    • 1996
  • A new static contractor using capillary phenomena induced by a highly packed fiber bundle was developed for the solvent extraction. When two immiscible phases being cocurrently and forcedly fed into the packed fiber bundle, the contactor brings about a very large liquid-liquid contact area for mass transfer within a small definite space without any turbulence and drop phenomena. In order to test the characteristics and stability of the static contractor system, continuous extraction experiments of TBP-uranyl ion-nitric acid system were done and compared with the batch extraction experiment of the same chemical system. The performance of the static contractor were the same as that of the ideal batch extractor with the same extraction condition. For the increase of the extraction yield by the contactor, the increase of organic flow rate was required at a fixed aqueous flow rate, and a certain residence time of the aqueous phase flow within the contactor system had to be maintained to meet the performance of the batch system of the same phase ratio. The residence time in the case of TBP-uranyl ion-nitric acid system was about 1.9 minutes. This system was confirmed to be effective and stable enough for purposes of the kinetic study of solvent extraction as well as the mutual separation and purification of ordinary materials because of good reproducibility and the stable and large static liquid-liquid contact area.

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Autogenous Shrinkage of High-Performance Concrete Containing Mineral Admixture (광물질 혼화재를 함유한 고성능 콘크리트의 자기수축)

  • Lee, Chang-Soo;Park, Jong-Hyok;Kim, Yong-Hyok;Kim, Young-Ook
    • Journal of the Korean Society of Hazard Mitigation
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    • v.7 no.3
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    • pp.19-31
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    • 2007
  • Humidity and strain were estimated for understanding the relation between humidity change by self-desiccation and shrinkage in high-performance concrete with low water binder ratio and containing fly ash and blast furnace slag. Internal humidity change and shrinkage strain were about 10%, 10%, 7%, 11%, 11% and $320{\times}10^{-6}$, $270{\times}10^{-6}$, $231{\times}10^{-6}$, $371{\times}10^{-6}$, $350{\times}10^{-6}$ respectively on OPC30, O30F10, O30F20, O30G40, O30G50 and from the results, fly ash made humidity change and strain decrease but slag increase comparing with ordinary portland cement. Considering only relation internal humidity and shrinkage by self-desiccation, humidity change and shrinkage represented the strong linear relation regardless of mineral admixture. For specifying the relation on internal humidity change and autogenous shrinkage strain, shrinkage model was established which is driven by capillary pressure in pore water and surface energy in hydrates on the assumption of a single network and extended meniscus in pore system of concrete. This model and experimental results had a similar tendency so it would be concluded that the internal humidity change by self-desiccation in HPC originated in small pores less than 20nm, therefore controlling plan on autogenous shrinkage might be focused on surface tension of water and degree of saturation in small pore.

Manufacturing and Operating Performance of the Heat Pipe with Sintered Wick (소결윅 히트파이프의 제작 및 작동성능)

  • Yun, Ho-Gyeong;Moon, Seok-Hwan;Ko, Sang-Choon;Hwang, Gunn;Choy, Tae-Goo
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.26 no.9
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    • pp.1260-1266
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    • 2002
  • In this study, to make an excellent heat pipe, the manufacturing technology of a sintered wick was investigated. Making a sintered wick is known to be very difficult but it has many advantages. For example, the porosity and pore size can be controlled and the capillary force is great. The mixture of copper and pore former powder was used as a wick material and ceramic-coated stainless steel was used as a mandrel which is necessary for vapor flow. To analyze the feature of the manufactured wick, not only porosity and pore size were measured but also the sintered structure was observed. A heat pipe with sintered wick was manufactured and the performance test of the heat pipe was performed in order to review cooling performance. The performance test results for the 4mm diameter heat pipe with the sintered wick shows the stability since the temperature difference between a evaporator and a condenser of the heat pipe is less than 4.4$^{\circ}C$, and thermal resistance is less than 0.7$^{\circ}C$/W, In the meantime the composite wick that is composed with sintered and woven wire was also examined. The heat transfer limit of the heat pipe with composite wick was enhanced about 51%~60% compare to the one with sintered wick.

Performance Evaluation of HFO-1234yf as a substitute for R-134a in a Household Freezer/Refrigerator (HFO-1234yf를 적용한 가정용 냉동/냉장고의 성능평가)

  • Lee, Jang-Seok;Han, Jun-Soo;Lee, Myung-Ryul;Jeon, Si-Moon
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.35 no.7
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    • pp.743-748
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    • 2011
  • The performance of HFO-1234yf as a substitute for R-134a was evaluated in a household freezer/refrigerator. A series of tests such as 'refrigerant charging test, pull-down test, cooling speed test, and energy consumption test were carried out under the AHAM (Association of Home Appliance Manufacturers) standard. The results of a drop-in test were compared with those of a test conducted using R-134a. A test under a severe ambient air condition ($43^{\circ}C$) was also conducted. The result shows that the refrigeration cycle performance of HFO-1234yf is as good as that of R-134a ; however, the diameter of capillary tube should be increased in order to improve its performance in the cooling speed test.

Comparison of Dioxin Analytical Results Between SP-2331 and DB-5MS Capillary Columns in the HRGC/HRMS Analysis (HRGC/HRMS에 SP-2331 및 DB-5MS 컬럼 사용시 다이옥신 결과의 비교)

  • Hong, Jongki;Yang, Jeong-Soo;Shin, Jung-Hwa;Ahn, Yun-Gyong;Lee, Dai-Woon
    • Analytical Science and Technology
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    • v.17 no.2
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    • pp.184-191
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    • 2004
  • In this study, the separation of toxic dioxin 2,3,7,8-congeners by DB-5MS and SP-2331 GC columns which are widely used in HRGC/HRMS analysis was examined. Through the dioxin analysis of column performance check standard solution and fly ash sample, the isomer specific separation of 2,3,7,8-substituted dioxins from tetra to hexa-isomers on DB-5MS and SP-2331 columns were studied. The effect of I-TEQ value by these columns was also studied. The total concentrations of toxic dioxins for the column performance check standard solution were 508.4 ng/mL analyzed by DB-5MS and 515.8 ng/mL analyzed by SP-2331, respectively. The I-TEQ value obtained by both columns was shown to be almost equivalent for the column performance check standard solution and fly ash sample.

Heat Dissipation Trends in Semiconductors and Electronic Packaging (반도체 및 전자패키지의 방열기술 동향)

  • S.H. Moon;K.S. Choi;Y.S. Eom;H.G. Yun;J.H. Joo;G.M. Choi;J.H. Shin
    • Electronics and Telecommunications Trends
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    • v.38 no.6
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    • pp.41-51
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    • 2023
  • Heat dissipation technology for semiconductors and electronic packaging has a substantial impact on performance and lifespan, but efficient heat dissipation is currently facing limited improvement. Owing to the high integration density in electronic packaging, heat dissipation components must become thinner and increase their performance. Therefore, heat dissipation materials are being devised considering conductive heat transfer, carbon-based directional thermal conductivity improvements, functional heat dissipation composite materials with added fillers, and liquid-metal thermal interface materials. Additionally, in heat dissipation structure design, 3D printing-based complex heat dissipation fins, packages that expand the heat dissipation area, chip embedded structures that minimize contact thermal resistance, differential scanning calorimetry structures, and through-silicon-via technologies and their replacement technologies are being actively developed. Regarding dry cooling using single-phase and phase-change heat transfer, technologies for improving the vapor chamber performance and structural diversification are being investigated along with the miniaturization of heat pipes and high-performance capillary wicks. Meanwhile, in wet cooling with high heat flux, technologies for designing and manufacturing miniaturized flow paths, heat dissipating materials within flow paths, increasing heat dissipation area, and reducing pressure drops are being developed. We also analyze the development of direct cooling and immersion cooling technologies, which are gradually expanding to achieve near-junction cooling.

An Experimental Study on the Basic Properties of Penetrating repair material using Silicate-based Inorganic Materials (규산염계 무기 재료를 활용한 침투성 보수재의 기초 특성에 관한 실험적 연구)

  • Ha, Sang-Woo;Oh, Sung-Rok;Choi, Yung-Wang
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.18 no.7
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    • pp.39-45
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    • 2017
  • In this study, permeable repair materials mainly composed of silicate - based inorganic materials(SIM), which are easily available domestically, were prepared as a basic study for the development of permeable repair materials using SIM. SIM were compared and examined for their performance as repair materials by selecting a product group which has many cases of use in foreign countries. The SIM used were mainly composed of sodium, potassium and lithium silicate. Performance evaluation of SIM was performed by absorption and penetration, compression and adhesion, rapid chloride ion penetration, rapid freezing and thawing, and chemical resistance test. According to the test results, SIM showed effective performance in all areas, mainly because SIM permeates into the interior of the capillary and has a dense internal microstructure. Therefore, it can be used variously to improve the durability of concrete based on the results of this experiment.

Thermal Performance Evaluation Monitoring Study of Transparent Insulation Wall System (투명단열 축열벽 시스템의 열성능 평가 실험 연구)

  • Kim, B.S.;Yoon, J.H.;Yoon, Y.J.;Baek, N.C.;Lee, J.S.
    • Journal of the Korean Solar Energy Society
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    • v.23 no.1
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    • pp.1-8
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    • 2003
  • Various efforts to combine new high-tech materials with solar system have been progressed nowadays in order to improve the performance of the existing passive solar system. TIM(Transparent Insulation Material) replacing the conventional outer building envelope glazing as well as the wall is good example for this trend. TI integrated wall is a thermal mass wall with a special shaped TIM instead of using typical envelope materials The tested TIM type is a small(diameter 4mm and thickness 50mm) capillary tube of Okalux model and cement brick(density 1500kg/m3). The purpose of this study was to analyze the thermal performance through the actual measurements performed in a test cell. This study was carried out to justify the following issues. 1) the impact of Tl-wall over the temperature variations 2) the impact of mass wall surface absorptance over the transient thermal behavior and 3) the impact of thermal mass wall thickness over the temperature variations. Finally, as results indicated that the peak time of room temperature was shifted about one hour early when absorptance of thermal mass wall changed from 60% to 95% for the 190mm thickness thermal mass wall test case. the temperature difference of both surfaces of thermal mass wall surface showed about $23^{\circ}C$ during a day of March for the 380mm thickness thermal mass wall case. However, the thermal mass wall was over-heated by outside temperature and solar radiation in a day of May the temperature difference of both surfaces of thermal mass wall surface was indicated $10^{\circ}C$ and inside temperature was observed more than average 22C.