• Journal of Biosystems Engineering
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• 제41권2호
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• pp.108-115
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• 2016

Purpose: Radio frequency (RF) heating is a promising thawing method, but it frequently causes undesirable problems such as non-uniform heating. This can occur because of the food shape, component distribution, and initial temperature differences between food parts. In this study, RF heating was applied to the thawing of cylindrically shaped pork sirloin by changing the shape of electrodes and the surrounding temperature. Methods: Curved electrodes were utilized to increase the thawing uniformity of cylindrically shaped frozen meat. Pork sirloin in the shape of a half-circle column was frozen in a deep freezer at $-70^{\circ}C$ and then thawed by RF heating with flat and curved electrodes. In order to prevent fast defrosting of the food surface by heat transfer from air to the food, the temperature of the thawing chamber was varied by -5, -10, and $-20^{\circ}C$. The temperature values of the frozen pork sirloin during RF thawing were measured using fiber-optic thermo sensors. Results: After multiple applications of curved electrodes resembling the food shape, and a cooled chamber at $-20^{\circ}C$ the half-cylindrically shaped meat was thawed without surface burning, and the temperature values of each point were similarly increased. However, with the parallel electrode, the frozen meat was partially burned by RF heating and the temperature values of center were overheated. The uniform heating rate and heat transfer prevention from air to the food were crucial factors for RF thawing. In this study, these crucial factors were accomplished by using a curved electrode and lowering the chamber temperature. Conclusions: The curved shape of the electrode and the equipotential surface calculated from the modeling of the parallel capacitor showed the effect of uniform heating of cylindrically shaped frozen food. Moreover, the low chamber temperature was effective on the prevention of the surface burning during RF thawing.

• 에너지공학
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• 제17권3호
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• pp.153-160
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• 2008

유연탄, 무연탄, 그리고 두 탄종의 혼합 비율을 달리한 혼합탄에 대한 열중량 분석을 수행하여 연소반응성을 평가하였다. 무연탄과 유연탄의 혼합탄에 대한 무게 감소율이나 반응속도의 모양을 살펴볼 때 반응시 두 탄종간에 서로 영향을 미치지 않고 혼합 비율에 비례하여 두 탄종이 독립적으로 반응하는 것을 알 수 있었다. 그리고A화력 발전소에서 유, 무연탄을 50% : 50%의 비율로 혼합하고 보일러 출력을 정격대비 약 65%인 134 MW부터 정격부하인 197 MW까지 증대시키면서 보일러 내의 연소상태, 운전특성을 분석하였다. A화력발전소의 연소시험 결과 출력에 따른 보일러내의 연소상태는 전체적으로 양호한 것으로 나타났으며 출력이 증가함에 따라 공기예열기 출구의 배기가스 온도가 설계치인 $430^{\circ}C$를 훨씬 상회하여 연소용 공기의 흡인방법을 변경하여 출구 가스 온도를 조절할 수 있었다.

• 한국진공학회지
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• 제17권3호
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• pp.189-194
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• 2008

플라즈마 진단법 중 손쉽고 구동이 용이한 장점으로 인해 범용 플라즈마 진단 장치로 사용되는 랑뮤어 (Langmuir) 탐침법은 탐침이 직접 플라즈마 내에 삽입됨으로써 플라즈마를 간섭하기 때문에 플라즈마 고유의 특성을 변형시키는 약점이 있다. 본 연구에서는 대기압 아르곤 자유 연소 아크 (free-burning arc)에 삽입된 랑뮤어 탐침에 의한 교란 영향을 고찰하기 위하여 탐침 유무에 따른 열플라즈마 상태를 수치계산 하였고, 온도장과 속도장이 왜곡된 정도를 비교 분석하였다. 열플라즈마를 모델링하기 위하여 열유동장과 전자기장에 관한 두 종류의 지배방정식을 상용 CFD 프로그램과 자체 제작한 서브루틴을 이용하여 연계 계산하였다. 삽입된 탐침에 의해 열플라즈마 온도장은 탐침의 앞뒤에서 모두 플라즈마 축의 수직 방향으로 큰 변화를 나타내는 열적 교란이 발생되었다. 속도장에서는 탐침 선단의 정체 영역과 후단 후류 영역에서 유동 교란이 발생되었으며, 삽입 된 탐침의 영향이 국부적인 것이 아닌 플라즈마 유동장 대부분 영역에 영향을 미침을 확인할 수 있었다. 따라서 탐침법의 신뢰성을 높이기 위해서는 탐침 삽입에 의한 플라즈마의 열유체역학적 교란을 고려해야 한다.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2004년도 제29회 KOSCI SYMPOSIUM 논문집
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• pp.225-230
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• 2004

Volatile organic compounds (VOCs) are low calorific value gases (LCVG) emitted from chemical processes such as painting booth, dye works and drying processes etc. Characteristics of VOCs are low calorific values less than 150 kcal/$m^3$, high activation energy for ignition and low energy output. These characteristics usually make combustion unstable and its treatment processes needs high-energy consumption, The cyclone combustion system is suitable for LCVG burning because it can recirculate energy through a high swirling flow to supply the activation energy for ignition, increases energy density to make a combustion temperature higher than usual swirl combustor and also increases mixing intensity, This research was conducted to develop optimized cyclone combustion system for thermal oxidation of VOCs. This research was executed to establish the effect of swirl number with respect to the combustion temperature and composition of exhausted gas in the specific combustor design.

• 태양에너지
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• 제18권1호
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• pp.81-89
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• 1998

In this paper an experimental was done to design combustion chambers which is required radiation strength of high temperature generator of absorption rigerator. Partiqularly, in combustion chamber radiative mediums were set and basic experiments were done according to its size by radiation strength and effects of heat transfer promotion. The results are as follows : 1) When radiative mediums were set in small combustion furnace burning nonframely radiative heat transfer was effected. 2) In case that area ratio($A/A_o$) of radiative medium is 0.82 or over, temperature fluctuation effects of furnace inside were not nearly. 3) In experimental boundary heat transfer effects were 1.8 times by setting up radiative medium. Specially, $q/{\Delta}T$ values of furnace inside were uniformed nearly by setting up radiative mediums.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 춘계학술대회 논문집
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• pp.1527-1532
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• 2007

We have evaluated the toxicity of interior materials for the railway passenger car by checking the release of $CO_2$, CO, NOx, SO2, HCl, HF, HBr, HCN. The NOx is one of the most effective for the determination of Toxic Index R value. It is generally known that the mechanism of thermal NOx generation without the Interior Material nitrogen source. This study started from the idea to check the NOx difference according to the furnace temperature. But from the results, it was revealed that NOx is not so sensitive for the furnace temperature in case of solid burning. Other gases such as HCN, CO were more changeable to the furnace Temp. We reported the test result as for toxicity index r(x).

• 한국연소학회지
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• 제8권3호
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• pp.1-7
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• 2003

Combustion using oxygen enriched air is an energy saving technology that can increase thermal efficiency by the improvement of burning rate and by the high temperature flame. Flame figures, OH radical intensities, temperature distributions and emission concentrations were measured according to oxygen enriched concentration and swirl number in a turbulent diffusion flat flame. It appeared that flame figure became flat and NO concentration decreased with increase of swirl number, and that the flame temperature increased high with increase of oxygen enriched concentration. In particular, it was most significant between oxygen concentration $40{\sim}60%$.

• Bulletin of the Korean Chemical Society
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• 제30권10호
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• pp.2245-2248
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• 2009

This paper demonstrates room temperature chemical vapor deposition (RTCVD) for fabricating titania inverse opals. The colloidal crystals of monodisperse polymer latex spheres were used as a sacrificial template. Titania was deposited into the interstices between the colloidal spheres by altermate exposures to water and titanium tetrachloride (Ti$Cl_4$) vapors. The deposition was achieved under atmospheric pressure and at room temperature. Titania inverse opals were obtained by burning out the colloidal template at high temperatures. The filling fraction of titania was controlled by the number of deposition of Ti$Cl_4$ vapor. The morphology of inverse opals of titania were investigated. The optical reflection spectra revealed a photonic band gap and was used to estimate the refractive index of titania.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2015년도 제51회 KOSCO SYMPOSIUM 초록집
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• pp.209-211
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• 2015

Evaporation characteristics of a single droplet of carbon nanofluids were investigated in a rapid compression machine(RCM). n-Heptane and carbon black N990 were used to synthesize the carbon nanofluids. RCM is an experimental set-up to simulate a single compression stroke of reciprocating engine. Temperature and pressure in a reaction chamber were measured during the compression stroke. After the piston reaches top dead center(TDC), temperature and pressure decreased due to the heat loss at wall. In that process, a single droplet of carbon nanofluids underwent unsteady condition. A single droplet was put at the center of reaction chamber. Thermocouple whose tip is $50{\mu}m$ was used not only to measure transient bulk temperature, but also to suspend the droplet. The picture of single droplet was taken using high speed camera with a frame rate of 500 fps. From those pictures, the droplet diameter was measured by visual basic program.

• 조명전기설비학회논문지
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• 제30권1호
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• pp.44-48
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• 2016

In this paper, we analyzed the operating characteristics of a ventilating fan due to overload and overheating. The experiment assumed the forcible restraint of the blade due to external objects and the aging process. We analyzed the experimental temperature and operating characteristics of the three places in the interior of the ventilating fan. As a result of the analysis, the temperature distribution was highest to lowest in the following order: the thermal fuse, the motor inside, and the above winding. There was smell of burning enamel in the restraint experiment. Following the thermal fuse operation, the insulation of motor winding was good. In the case of rated voltage and new ventilating fan restrained for about 4hours, and the results of restraint experiments in the presence or absence of the thermal fuse, no risk of deformation or fire due to overheating was identified. Henceforward, ignition hazard experiments will be required for additional factors of aging, pollution, and defective insulation.