• Transactions of the Korean Society of Automotive Engineers
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• v.25 no.3
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• pp.297-308
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• 2017

One of the major engine thermal management system(TMS) strategies for improving fuel economy is to operate the engine in high temperatures. Therefore, this work performed a numerical and experimental study to examine the effect of several different STOs(Starting Temperature of Opening) of wax-thermostat, ranging from $85^{\circ}C$ to $105^{\circ}C$, of gasoline engine on fuel economy and emission characteristics. In this study, a gasoline car equipped with waxthermostat was tested and simulated under FTP-75 and HWFET mode. CRUISE $M^{TM}$ was used to simulate vehicle dynamics, transient engine performance and TMS. The test results showed fuel savings for both drive cycles due to higher STO of $100^{\circ}C$, which is slightly worse than that of $90^{\circ}C$ and amounts between 0.34 and 0.475 %. These controversial results are attributed to experimental errors and uncertainty. The computational results for three STOs, $85^{\circ}C$, $95^{\circ}C$ and $105^{\circ}C$, showed that fuel savings attributed to the application of higher STOs of $95^{\circ}C$ and $105^{\circ}C$ are relatively small and range from 0.306 to 0.363 %. It is also found that the amount of HC and CO emissions from the tailpipe tends to decrease with higher engine coolant temperature because of faster catalyst light-off and improved combustion.

• Journal of the Korean Society of Propulsion Engineers
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• v.19 no.4
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• pp.69-76
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• 2015

Recently, environmental sustainability of the transitional explosives and propellants is an issue of growing importance in energetic materials. For examples, ammonium perchlorate(AP) as an solid propellants oxidizer could create a poisonous gas and atmospheric pollutions, such as HCl. Among the several oxidizers, hydrazinium nitroformate(HNF) is an effective candidate substance for eco-friendly oxidizer, which has high density, pressure index, and less smog generating property during combustion for the Divert and Attitude Control System(DACS). This study was confirmed a synthesis through various conditions, was performed for the essential data of solubility the crystallization process. Also, crystallization process such as cooling, drowning-out and sonication were performed.

• Journal of the Society of Naval Architects of Korea
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• v.39 no.1
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• pp.49-60
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• 2002

Welding is essential in ship production since welding is very popular method for joining two or more metals. However, welding causes residual stress and distortion and these give a bad influence to the structure strength and assembly of ship blocks. Therefore, prediction and treatment of residual stress and distortion is a key to accuracy control in shipyard. In this paper, a computational procedure, based on thermal-elastic-plastic 3-dimensional FEA, has been suggested to simulate butt and fillet welding process. In the simulation process, temperature distribution at each time step is obtained by heat transfer analysis and then thermal deformation analysis is done with obtained temperature distributions to find the residual stress and distortion. In heat transfer analysis, enthalpy method is used to realize phase change at melting temperature. Also element birth and death method is used to simulate adding of weld metal in both heat transfer analysis and thermal elastic plastic analysis. The proposed procedure is verified by related researches and the results show good agreement with those of related researches.

• Nuclear industry
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• v.27 no.4 s.290
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• pp.46-50
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• 2007

고리 1호기는 한국에서 최초로 규제 기관에 계속운전을 신청한 원전이다. 2007년 6월에 설계 수명 기간 만료가 되는 고리 1호기는 규제 기관으로부터 계속운전(Continued Operation)에 대한 안전성 심사를 받고 있다. 한수원은 고리 1호기 계속운전 승인을 금년 12월에 받기 위해 최선을 다하고 있으며 지역 주민의 사회적 수용성 확보를 위해 노력중이다. 고리 1호기의 계속운전 기간 동안 안전성을 평가하고 정리한 안전성평가보고서를 한수원은 2006년 6월에 정부에 제출하였다. 고리 1호기는 웨스팅하우스의 2루프 가압경수로이다. 이와 동일한 원전인 일본의 미하마 1,2호기와 겐까이1호기가 계속운전중이며, 미국의 기네이와 포인트 비치 1,2호기가 계속운전 승인을 받았다. 제출한 안전성평가보고서에 대해 한국원자력안전기술원이 심사중이며, 해외 원전과 같이 계속운전을 할 수 있을 것으로 예상하고 있다. 또한 계속운전을 위한 사회적 수용성(Public Acceptance) 확보는 설비의 철저한 안전성 확보 및 지역 주민의 공감대 형성을 통해서 이루어질 것이다. 설계 수명 이후 원자력발전소를 계속 운전하는 것은 이미 선진국에서 시행되고 있다. 2007년 3월 기준으로 미국에서 48기가 운영 허가 갱신 승인을 받았고, 영국은 8기, 일본은 12기가 계속운전중이다. 고리 1호기 성능 지표를 개선시키기 위해서 한수원은 증기발생기, 저압 터빈, 원자로 냉각재 펌프 내장품, 주변압기, 주발전기 등을 교체하였으며, 수명관리 연구, 주기적안전성 평가, 환경 영향 평가를 수행하였다. 2005년 9월에는 미국의 운영 허가 갱신 제도를 참조하여 원자력법이 개정되었다. 이에 한수원은 개정된 원자력법에 맞추어 주기적 안전성평가, 주요 기기에 대한 수명 평가 및 방사능 환경 영향평가를 하였다. 이 세가지 보고서들로 구성된 안전성평가보고서를 2006년 6월에 규제 기관에 제출하였다. 계속운전은 한국을 비롯하여 부존 자원이 부족한 국가들에게는 에너지 자원의 효율적 활용 및 온실 가스 배출을 고려할 때 반드시 필요한 것이다.

• Transactions of the Korean hydrogen and new energy society
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• v.31 no.5
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• pp.429-435
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• 2020

This paper describes the experimental study of reverse-Brayton refrigeration system for application to high temperature superconductivity electric devices and LNG re-liquefaction. The reverse-Brayton refrigeration cycle is designed with operating pressure of 0.5 and 1.0 MPa, cooling capacity of 2 kW at 77 K, and neon as a working fluid. The refrigeration system is developed with multi scroll compressor, turbo expander and plate heat exchanger. From experiments, the performance characteristics of used components is measured and discussed for 77-120 K of operating temperature. The developed refrigeration system shows the cooling capacity of 1.23 kW at 77 K and 1.64 kW at 110 K.

• Journal of Advanced Marine Engineering and Technology
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• v.28 no.3
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• pp.500-508
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• 2004

The heat transfer coefficients during gas cooling process of carbon dioxide in a horizontal tube were investigated. The experiments are conducted without oil in the refrigerant loop. The main components of the refrigerant loop are a receiver, a variable-speed pump, a mass flow meter, a pre-heater, and a gas cooler(test section). The water loop consists of a variable-speed pump, an isothermal tank, and a flow meter. The gas cooler is a counterflow heat exchanger by cooled water flowing in the annulus. The $CO_2$ flows in the horizontal stainless steel tube. which is 9.53mm in O.D. and 7.75mm in I.D. The gas cooler is 6 [m] in length. which is divided into 12 subsections, respectively. The experimental conditions considered in the study are following range of variables : refrigerant temperature is between 20 and $100^{\circ}C$. mass fluxes ranged from 200 to 400kg/($m^2$.s), average pressure varied from 7.5 to 10.0MPa. The main results were summarized as follows : The friction factors of $CO_2$ in the gas cooler show a relatively good agreement with those predicted by Blasius' correlation. The local heat transfer coefficient in the gas cooler has compared with most of correlations, which are the famous ones for forced convection heat transfer of turbulent flow. The results show that the local heat transfer coefficient of gas cooler agrees well with the correlation by Bringer-Smith except that at the region near pseudo critical temperature. while that at the near pseudo critical temperature is higher than the correlation.

• Journal of Advanced Marine Engineering and Technology
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• v.31 no.6
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• pp.707-714
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• 2007

The heat transfer coefficient and Pressure drop during gas cooling process of $CO_2$ (R-744) in inclined helical coil copper tubes were investigated experimentally. The main components of the refrigerant loop are a receiver. a variable-speed pump. a mass flow meter, a pre-heater and a inclined helical coil type gas cooler (test section). The test section consists of a smooth copper tube of 2.45mm inner diameter. The refrigerant mass fluxes were varied from 200 to $600[kg/m^2s]$ and the inlet Pressures of gas cooler were 7.5 to 10.0 [MPa]. The heat transfer coefficients of $CO_2$ in the inclined helical coil tubes increases with the increase of mass flux and gas cooling pressure of $CO_2$. The pressure drop of $CO_2$ in the gas cooler shows a relatively good agreement with those Predicted by Ito's correlation developed for single-phase in a helical coil tube. The local heat transfer coefficient of $CO_2$ agrees well with the correlation by Pitla et al. However, at the region near pseudo-critical temperature. the experiments indicate higher values than the Pitla et al. correlation. Therefore. various experiments in the inclined helical coil tubes have to be conducted and it is necessary to develop the reliable and accurate prediction determining the heat transfer and pressure drop of $CO_2$ in the inclined helical coil tubes.

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.5
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• pp.828-836
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• 1987

The inclusion of thermophoresis in particle deposition studies has often been treated separately from deposition due to flow characteristics. Also previously reported experimental results on thermophoresis have been studied in the regions of relatively small temperature gradients. In this study, using real-time laser light reflectivity method, we measured the angular dependence of the deposition rates of particles of the cylindrical collector surface, which immerged in laminar flow of a hot gas suspension of small particles. And we extended the previous narrowband results of thermophoretic deposition rates to the regions of large temperature gradients between the hot gas stream and the collector surface. Based on the obtained data, the cylinder's forward stagnation-point region is considerably enriched in particle 'phase' density owing to the compressibility effect, which leads to locally enhanced deposition while the downstream region from the stagnation point inertial force acts in the opposite direction, which tends to centrifuge particles away from the wall, thus the local deposition rates by thermophoresis are reduced.

• Journal of Energy Engineering
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• v.5 no.1
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• pp.50-55
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• 1996

A numerical simulation on a primary calcinator of porcelain was performed with using Fluent to calculate the heat efficiency by studying velocity vector and temperature profile according to variables such as the location of outlet and porcelain. Control-Volume based Finite Difference Method and Up-wind scheme are used for discretization of differential equation. SIMPLEC Algorithm and standard k-$\varepsilon$ turbulent model are selected to resolve the pressure-velocity coupling and the turbulent. The result of simulation showed that the whole velocity vector field in a calcinator was varied greatly according to the location of outlet. But the whole temperature profile at each zone was still high regardless of the location of outlet because of the radiation. But the temperature of a case with a outlet at sidepart of preheating or cooling zone was little high compared to the case with a outlet on the top of preheating zone. The velocity vector field and temperature profile in a calcinator were almost not affected by the location of porcelain, but the temperature inside a porcelain was much affected according to the place where it was located. The heat efficiency in a calcinator was 44.6% and the gas temperature in the outlet was about 1000 K.

• Proceedings of the Korean Society of Embryo Transfer Conference
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• 2002.11a
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• pp.93-93
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• 2002

싸움소(투우)는 1999년 문화관광부지정‘한국의 10대 지역문화 관광축제’로 선정되어, 청도군 투우대회가 한국을 대표하는 축제가 되었고, 상설투우장의 건설로 새로운 레져 산업으로 부상하고 있다. 그러나 싸움소 생산에 소요되는 유전인자 보존 및 생산기반은 전무한 실증이며, 본 연구는 청도군내 우수 종모우을 선별하여 정액채취 및 동결정액을 생산하여 군내 한우번식 농가에서 인공수정을 실시하고 계절별 수태율과 송아지의 성비를 조사하였다. 종모우 번개(나이6세, 체중850kg, 97, 98년 우승)와 사자(나이6세, 체중870kg 98, 99년 준우승) 2두로부터 일반적인 방법으로 인공질을 이용하여 1999년 10월에 정액을 채취하였다. 채취된 정액은 35$^{\circ}C$에서 3~5배정도로 희석하여 정자농도와 활력을 평가하였다. 희석정액은 90분간에 걸처 5$^{\circ}C$ 까지 냉각하면서 글리세롤을 첨가한 난황구염산나트륨액으로 여러번 나누어 희석하여 정자의 충격을 피하였다. 글리세롤평형 2시간 후 0.5$m\ell$스트로에 정자수가 3500만/스트로의 분주.봉인하여, 정액의 동결은 액체질소상에서 4~5cm 위에 스트로를 평행으로 놓아 액체질소 가스로 10~15분간 예비동결한 다음, -8$0^{\circ}C$의 초저온 냉장고에서 케니스터에 넣어 -196$^{\circ}C$ 액체질소에 보관하였다. 인공수정을 실시하고 40일 전후에 직장검사를 통해 임신율과 수태율을 조사하고 분만한 송아지의 성비를 기록하였다. 채취한 싸움소의 정액량은 번개와 사자가 각각 평균 4.6$m\ell$와 3.8$m\ell$이고, 동결전의 정자의 활력은 번개와 사자의 정액이 각각 70.3 vs 75.3%, 동결후의 활력은 37.3 vs 40.3%로 유의한 차이는 없었다. 번개와 사자의 동결정액으로 각각 44두와 127두를 인공 수정하였고, 40일 전후의 임신율은 26두 vs 80두(59.1 vs 63.0% )였으며, 수태율은 26두 vs 66두(59.1 vs 52.0% )로 이들간의 유의한 차이는 없었다. 번개와 사자의 수송아지의 성비는 각각 65.3 vs 42.4%로 유의한 차이가 있었다. 싸움소 정액 동결보존과 인공수정으로 싸움소 혈통을 가진 송아지가 생산되었다. 그러나 생산된 송아지가 싸움소의 능력을 가진 것을 선별하여 혈통을 고정시키고, 훈련으로 싸움소의 제질을 발굴하는 것이 앞으로의 연구과제이다.