• 열처리공학회지
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• 제22권4호
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• pp.210-216
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• 2009

Stainless steel EGR cooler of diesel engine is widely used to prevent the corrosion due to the content of sulfur in diesel fuel. The strength of brazed joint between stainless steel materials is very important. It is essential to observe the spreading ratio of the filler metals under the condition of deoxidation or vacuum during heating process. In this experiment, spreading ratio was tested to find the optimum brazing condition for stainless steel using brazing filler metals of FP-613, BNi-2 and BNi-5 on sus304 and sus410. Anti-corrosion tests were also performed on the above filler metals with solution of 5% $H_2SO_4$, 65% $HNO_3$ and 5% $NH_4OH$. Consequently FP-613 has good ability for anti-corrosion with 30% of chromium content compared with other filler metals. The optimum brazing conditions are occurred at $960^{\circ}C$ for 90 min. and at $1090^{\circ}C$ for 50 min. at the same degree of vacuum, $2{\sim}3{\times}10^{-3}$ Torr.

• Journal of Advanced Marine Engineering and Technology
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• 제39권4호
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• pp.432-436
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• 2015

본 연구에서는 해수를 활용하여 수동적으로 냉각되는 폴리머 히트싱크의 열성능을 전산적으로 탐구한다. 폴리머 히트싱크는 폐열회수를 위한 열전생성기의 저온면의 냉각모듈로 제안되었고, 상세한 수치연구를 위해 3차원 전산유체역학 모델링이 수행되었다. 폴리머 히트싱크의 기본 소재로 polyphenylene sulfide (PPS)와 pyrolytic graphite (PG)가 선택되었고, 전산연구는 다양한 휜 수와 휜 두께에서 PPS와 PG 히트싱크의 성능을 결정하고, 이 결과는 알루미늄 (Al)과 티타늄 (Ti) 히트싱크와 비교된다. 연구결과는 PG 히트싱크가 Ti 히트싱크 보다 3~4배 열성능이 우수함을 보이는데, 이 결과는 Ti 히트싱크보다 더 우수한 PG 히트싱크의 열확산에 기인한 것으로 보인다. 연구결과에 의하면 PG 히트싱크의 열성능에 대한 휜 수 증가의 효과가 PPS와 Ti 히트싱크 경우와는 상반됨을 보이는데, 이는 휜 수 증가에 대한 열확산, 표면적 증대, 유동저항의 상관관계로 설명이 가능하다.

• Tribology and Lubricants
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• 제38권5호
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• pp.185-190
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• 2022

Among the operating limits of a heat pipe, the capillary limit is significantly affected by the characteristics of the wick, which is determined by the capillary performance. The major parameters for determining capillary performance are the maximum capillary pressure and the spreading characteristics that can be expected through the wick. A well-designed wick structure improves capillary performance and helps improve the stability of the heat pipe by enhancing the capillary limit. The capillary performance can be improved by forming a porous microstructure on the surface of the wick structure through surface modification techniques. In this study, a microstructure is formed on the surface of the wick by using a surface modification method (i.e., an electrochemical etching process). In the experiment, specimens are prepared using stainless-steel screen mesh wicks with various fabrication conditions. In addition, the spreading and capillary rise performances are observed with low-surface-tension fluid to quantify the capillary performance. In the experiments, the capillary performance, such as spreading characteristics, maximum capillary pressure, and capillary rise rate, improves in the specimens with microstructures formed through surface modification compared with the specimens without microstructures on the surface. The improved capillary performance can have a positive effect on the capillary limit of the heat pipe. It is believed that the surface microstructures can enhance the operational stability of heat pipes.

• 국제초고층학회논문집
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• 제7권4호
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• pp.389-396
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• 2018

This paper presents a numerical investigation on the structural response of a multi-story building subjected to spreading multi-compartment fires. A recently proposed simple fire model has been used to simulate two spreading multi-compartment fire scenarios in a 10-story steel-framed office building. By assuming simple temperature rising and distribution profiles in the fire exposed structural components (steel beams, steel column and concrete slabs), finite element simulations using a three-dimensional structural model has been carried out to study the failure behavior of the whole structure in two multi-compartment fire conditions and also in a standard fire condition. The structure survived the standard fire but failed in the multi-compartment fire. Whilst more accurate fire models and heat transfer models are needed to better predict the behaviors of structures in realistic fires, the current study based on very simple models has demonstrated the importance and necessity of considering spreadingmulti-compartment fires in fire resistance design of multi-story buildings.

• Nuclear Engineering and Technology
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• 제43권3호
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• pp.205-216
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• 2011

Recently, many research studies have investigated the enormous critical heat flux (CHF) enhancement caused by nanofluids during pool boiling and flow boiling. One of the main reasons for this enhancement is nanoparticle deposition on the heated surface. However, in real applications, nanofluids create many problems when used as working fluids because of sedimentation and aggregation. Therefore, artificial surfaces on silicon and metal have been developed to create an effect similar to that of nanoparticle deposition. These modified surfaces have proved capable of greatly increasing the CHF during pool boiling, and good results have also been observed during flow boiling. In this study, we demonstrate that the wetting ability of a surface, i.e., wettability, and the liquid spreading ability (hydrophilic surface property), are key parameters for increasing the CHF during both pool and flow boiling. We also demonstrate that when the fuel surface in nuclear power plants is modified in a similar manner, it has the same effect, producing a large CHF enhancement.

• 한국철도학회논문집
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• 제7권3호
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• pp.180-185
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• 2004

The present study investigates the effect of fire growth model on fire development characteristics in a carriage. The parallel processing version of FDS code is used to simulate the fire driven flow in a carriage and two types of fire growth model which are flame spread model and t$^2$ model are examined for the same geometrical condition. The heat release rates(HRR) of both model are similar each other until 30 s after ignition, but the flame spread model predicts 5 times higher than those of the t$^2$ fire model during the quasi-steady fire period. Maximum heat release rate in the case of flame spread model reaches about to 12 MW at 100 s after fire ignition. Also, various database of fire properties for combustible materials and more elaborate combustion model considering the flame spreading phenomena are required for better predictions of fire development characteristics using numerical simulation.

• Journal of Periodontal and Implant Science
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• 제47권3호
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• pp.174-181
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• 2017

Purpose: Epitope spreading is a phenomenon in which distinct subdominant epitopes become major targets of the immune response. Heat shock protein (HSP) 60 from Porphyromonas gingivalis (PgHSP60) and peptide 19 from PgHSP60 (Pep19) are immunodominant epitopes in autoimmune disease patients, including those with periodontitis. It remains unclear whether Pep19 is a dominant epitope in subjects without periodontitis or autoimmune disease. The purpose of this study was to determine the epitope spreading pattern and verify Pep19 as an immunodominant epitope in healthy teenagers using dot immunoblot analysis. The patterns of epitope spreading in age-matched patients with type 1 diabetes mellitus (type 1 DM) and healthy 20- to 29-year old subjects were compared with those of healthy teenagers. Methods: Peptide from PgHSP60, Mycobacterium tuberculosis HSP60 (MtHSP60), and Chlamydia pneumoniae HSP60 (CpHSP60) was synthesized for comparative recognition by sera from healthy subjects and patients with autoimmune disease (type 1 DM). Dot immunoblot analysis against a panel of peptides of PgHSP60 and human HSP60 (HuHSP60) was performed to identify epitope spreading, and a densitometric image analysis was conducted. Results: Of the peptide from PgHSP60, MtHSP60, and CpHSP60, PgHSP60 was the predominant epitope and was most consistently recognized by the serum samples of healthy teenagers. Most sera from healthy subjects and patients with type 1 DM reacted more strongly with PgHSP60 and Pep19 than the other peptides. The relative intensity of antibody reactivity to Pep19 was higher in the type 1 DM group than in the healthy groups. Conclusions: Pep19 is an immunodominant epitope, not only in autoimmune disease patients, but also in healthy young subjects, as evidenced by their robust immunoreactivity. This result suggests that the Pep19-specific immune response may be an initiator that triggers autoimmune diseases.

• 한국산학기술학회논문지
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• 제11권3호
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• pp.1108-1114
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• 2010

Nocolok 브레이징을 하기 위해서는 플럭스 용액을 접합부 표면에 도포해야 하는데 저농도 플럭스와는 달리 고농도 플럭스는 필요한 부분만 도포해야 한다. 보통 기존의 브레이징로에서는 고농도 플럭스 도포를 수작업으로 하고 있는데 작업의 비효율성을 초래하고 플럭스 분진 날림 및 열 등으로 인해 작업 환경을 악화시킨다. 그러므로 경제적이고 효율적인 고농도 플럭스 자동 도포 장치의 개발을 통한 품질 향상 및 생산 단가 저감 등이 절실한 실정이다. 따라서, 본 연구에서는 고농도 플럭스 자동 도포 시스템을 설계 및 제작하였고 이를 직접 브레이징로에 장착하여 자동화 공정으로 개선시켜 기피 작업 해소 및 생산성 향상을 이루었다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2286-2291
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• 2008

Some electronics component, which is adopted as components of antenna for radar or satellite system and used for amplifying signals to transmit, is accompanied by very significant heat dissipation levels because of the inefficiencies inherent in radio frequency wave generation. So, proper cooling performance for that system is base requirement for thermal design. On this paper, we applied heat spreading structures to reduce thermal density and find the optimum values of heat sink design factors through theoretically, numerically and evaluated by product test. As the results, the performance of the cooling system shows the propriety of cooling high density heat dissipation electronics components.

• 한국표면공학회지
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• 제48권6호
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• pp.297-302
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• 2015

Nanocrystalline diamond(NCD) coated aluminium plates were prepared and applied as heat sinks for LED modules. NCD films were deposited on 1 mm thick Al plates for times of 2 - 10 h in a microwave plasma chemical vapor deposition reactor. Deposition parameters were the microwave power of 1.2 kW, the working pressure of 90 Torr, the $CH_4/Ar$ gas ratio of 2/200 sccm. In order to enhance diamond nucleation, DC bias voltage of -90 V was applied to the substrate during deposition without external heating. NCD film was identified by X-ray diffraction and Raman spectroscopy. The Al plates with about 300 nm thick NCD film were attached to LED modules and thermal analysis was carried out using Thermal Transient Tester (T3ster) in a still air box. Thermal resistance of the module with NCD/Al plate was 3.88 K/W while that with Al plate was 5.55 K/W. The smaller the thermal resistance, the better the heat emission. From structure function analysis, the differences between junction and ambient temperatures were $12.1^{\circ}C$ for NCD/Al plate and $15.5^{\circ}C$ for Al plate. The hot spot size of infrared images was larger on NCD/Al than Al plate for a given period of LED operation. In conclusion, NCD coated Al plate exhibited better thermal spreading performance than conventional Al heat sink.