• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.194-195
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• 2013

초음속 공기 플라즈마 환경을 모사할 수 있는 0.4 MW급 Enhanced Huels형 초음속 공기 플라즈마 발생 장비가 2012년에 전북대학교에 설치 완료되었다. 초음속 공기 플라즈마 시험장비는 대기권으로 reentry 할 수 있는 비행체의 열차폐체 시험평가를 주목적으로 개발되었으며, 핵융합장치용 고온 내열체 소재개발에도 활용될 예정이다. 분절형 아크 플라즈마 토치는 전극부식에 의한 오염도를 적으면서 고출력의 안정적인 플라즈마를 발생시키며, 일반적인 직류 토치로는 얻을 수 없는 초고엔탈피 플라즈마 열유동을 얻을 수 있는 특징이 있다. 구축된 장비는 최대 직류 출력 1,200 kW의 DC 전원공급장치, 0.4 MW급의 분절형 아크 플라즈마 토치, ${\phi}1.5m{\times}2m$ 크기의 진공쳄버, 1 MW의 냉각 능력을 갖춘 디퓨저와 열교환기, 진공 용량 $100m^3$/min의 진공펌프 9대, 88 g/s의 공기유량에서 NOx를 50,000 ppm에서 100 ppm으로 저감할 수 있는 후처리 시스템, 4 bar 15 g/s의 공기를 공급할 수 있는 가스 공급장치, 30 bar 600 lpm의 저전도수와 4 bar 560 lpm의 일반수를 공급할 수 있는 냉각수 공급장치로 구성되어 있다. 초음속 공기 플라즈마의 발생 특성을 시험하기 위해 플라즈마 발생 조건으로 토치공급전력 350 kW와 410 kW, 토치 공기 공급 유량 16.3 g/s, 토치 내부압력 3.9~4.2 bar, 챔버압력 40 mbar으로 시험을 수행하였다. 발생된 플라즈마 상태를 진단하기 위해 속도는 쇄기 탐침기, 열유속은 Gardon 게이지, 엔탈피와 토치 효율은 토치의 공급전력과 냉각수에 의한 손실 전력으로 각각 측정하였다.

• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.1
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• pp.64-70
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• 2008

Temperatures of engine head and liner depend on many factors such as spray and combustion process, coolant passage flow and engine related structures. To estimate the temperature distribution of engine structure, multi-dimensional computational fluid dynamics (CFD) codes have been mainly adopted. In this case, it is of great importance to obtain the realistic wall temperature distribution of entire engine structure. In the present work, a CFD-FEM coupling methodology was presented to address this demand. This approach was applied to a real large-size marine diesel engine. CFD combustion and coolant flow simulations were coupled to FEM temperature analysis. Wall heat flux and wall temperature data were interfaced between combustion simulation and solid component temperature analysis via translator by a commercial CFD package named FIRE by AVL. Heat transfer coefficient and surface temperature data were exchanged and mapped between coolant flow simulation and FEM temperature analysis. Results indicate that there exists the optimum cell thickness near combustion chamber wall to reasonably predict the wall heat flux during combustion period. The present study also shows that the effect of cell refining on predicting in-cylinder pressure during combustion is negligible. Hence, the basic guidance on obtaining the wall heat flux needed for the reasonable CFD-FEM coupling analysis has been established. It is expected that this coupling methodology is a robust tool for practical engine design and can be applied to further assessment of the temperature distribution of other engine components.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.18 no.1
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• pp.47-53
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• 1982

An analysis of convection, in a fully developed laminar steady flow through the vertical square duct under the condition of variational symmetric heat flux, is considered. Finite element solution algorithm by Galerkin's method with triangular elements and linear interpolation polynominals for the temperature and velocity profiles are derived for the vertical square duct. The comparison of temperature distribution due to variational symmetric heat flux in the duct were made with available the other data when the condition of peripheral heat flux were uniform and zero. Numerical values for the dimensionless temperatures and Nusselt numbers at selected Rayleigh numbers and pressure gradient parameters were obtained at a few nodal points for the vertical square ducts and effects of corner in the duct were investigated.

• Journal of the Korean Society of Propulsion Engineers
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• v.14 no.5
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• pp.45-50
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• 2010

Thermal analyses have been performed to study the effect of location of fuel ring and thermal barrier coatings in regenerative cooling channels in a full-scale combustor. For the effective cooling, the fuel ring has better be installed near axial location of the low expansion ratio and low heat flux, and branching of cooling channels is preferable. Also, the radiative cooled nozzle extension is thought to be reasonable for the cooling of combustor walls. Among the possible coatings, $Y_2O_3$ stabilized $ZrO_2$ coating and Ni/Cr coating have been adopted. Compared with Ni/Cr coating which has high oxidation resistance, $Y_2O_3$ stabilized $ZrO_2$ coating, one of ceramic coatings is found to be much effective to sustain the thermal survivability of combustion walls.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.1 no.2
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• pp.46-58
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• 1991

The synthesized ZnO powder was prepared by spray pyrolysis method using ultrasonic vibrator. The starting solutons were the aqueous solution of $Zn(NO_3)_2\cdot6H_2O$. The concentration was prepared 1M, O.5M, O.25M, and O.lM. The Nz carrier gas was 2.3cm$\cdot{sec}^{-1}$. The prepared powder from the $Zn(NO_3)_2{\cdot}6H_2O$ aqueous solution was Zine oxide with hexagonal structure. The shape of prepared powder was fine size, narrow size distribution, agglomerate-free, nearly sphere particle. Also, the particle size was about $ 0.28-0.61\mum$.

• Journal of the Korean Institute of Gas
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• v.13 no.3
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• pp.49-53
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• 2009

Relief systems can improve the process safety because it has the function for the prevention of overpressure. Flare stacks is necessary to avoid explosion, radiation, or toxicity by waste-gas emitted from relief system. Safe combustion is one of the important factors to improve safety and the quantity and velocity emitted is ruled in the API code 521. Due to the pressure of released gas and mass flow, a flame from flare stack is similar to jet fire. In this study, we have investigated the effect of flame form on complete combustion and heat emission. API code was similar to jet fire model in flame length, the flame had an effect on the ground.

• Transactions of the KSME C: Technology and Education
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• v.1 no.2
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• pp.179-186
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• 2013

Far-infrared radiation therapies are becoming more popular for blood circulation disorders, cardiovascular disease, skin diseases, inhibit cancer cell, etc replacing conventional operations. In this research, thermal characteristics of heating part in panel radiators, which is effective on the blood circulation disorders were experimentally analyzed. The heating line supplies heat energy to insulation coatings with heat flux of $150mW/m^2$ in normal status and as a result the coatings reached 20% of the heating line temperature. In other words, the insulation itself could increase surface temperature of heating plates by 20% and raise thermal time constant promote blood circulation effect. We also found that space arrangement of the heating lines was an important factor in designing heating parts and both coefficient of heat conduction and density of the heating plate should be also considered for superimpose of thermal diffusion.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2011.04a
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• pp.180-187
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• 2011

본 논문은 다중이용업소와 목조건축물에 자주 사용되는 미송합판에 방염처리를 하여 유사 화재를 구현하고, 그 화염 세기에 따른 방염의 실효성을 실험한 것이다. 방염처리를 하면 화재 시 가연물의 초기착화시간을 지연시켜 화재성장속도를 늦출 수 있고, 원활한 소화활동을 가능하게 해준다. 하지만 어느 정도 화재가 진행되어 화염이 거세지면, 45도 연소시험을 통한 방염기준을 충족하여도 그 성능을 기대하기 어렵다고 한다. 따라서 45도 연소시험 시 사용되는 65mm의 불꽃보다 큰 화염상태(초기착화 이후의 상태)에서 방염처리한 내장재(미송합판)의 방염성능이 유지되는지의 여부를 실제로 입증하고 그 근거를 뒷받침하기 위하여 본 연구를 시작하게 되었다. 실험에서는 화재의 규모(화염의 세기)를 달리하여 각기 다른 종류의 방염제로 방염 처리한 미송합판의 착화 시 화염온도, 복사열 유속 그리고 착화지연시간을 파악하였으며, 45도 연소시험과 관련하여 방염성능을 분석하였다. 45도 연소시험의 경우 실험에 사용한 방염 처리 합판은 방염성능 기준을 만족하는 것으로 나타났으며, 소규모 유사 화재로 직경 10cm 연소용기를 사용한 연소실험에서는 방염 처리한 합판의 착화지연시간이 평균적으로 대규모 유사 화재실험보다 길어 어느 정도는 방염효과를 갖는 것으로 나타났다. 하지만 대규모 유사 화재로 1단위 유류화재 연소용기를 사용한 연소실험의 경우 열방출율이 커 형성된 탄화막이 무분별하게 박리되고 발화가 일어나 착화지연시간의 차이를 구별하기 어려웠기 때문에 방염효과를 기대할 수 없었다.

• Solar Energy
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• v.18 no.3
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• pp.89-94
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• 1998

The heat transfer characteristics of a fluidized bed latent heat storage system using encapsulated PCM was investigated. The cylindrical test section has the dimension of 50 mm I.D. and 40 cm in height. The phase change material(PCM) was the sodium acetate and was encapsulated by the multiple layers of PMMA and paraffin wax. The size of encapsulated PCM was $2{\sim}3mm$ and melting point was $58^{\circ}C$. The instantaneous heat storage and heat release rates were determined and the instantaneous heat transfer coefficient based on the fluidized bed volume was also determined. The effect of inlet temperature and velocity of heat transfer fluid on the heat transfer coefficient was also investigated.

• Fire Science and Engineering
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• v.25 no.6
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• pp.127-135
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• 2011

In this study, we assumed the kitchen fire raising the highest fire rate in apt. and analyzed the fire risk to use CFD in order to estimate the problem of evacuation equipment and the fire vulnerability of 16 or fewer storey apartment. Fire occurring in the kitchen is expended to the livingroom and other rooms. We analyzed that the temperature effected by heat was more than $60^{\circ}C$ after 90 sec in the entrance of apartment unit. If fire is early recognized by men and men don't escape in time, it have too huge demage to block the exit. When the evacuation equipment suggested in this study was installed in order to solve the problem of evacuation equipment, we analyzed that it was estimated more than safe in safety evaluation by heat and heat flux.