• KSTLE International Journal
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• 제7권2호
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• pp.35-44
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• 2006

Turbocharger bearings are under the circumstance of high temperature, moreover rotated at high speed. It is necessary to be designed overcoming the high temperature. So the type of oil inlet port, the inlet oil temperature and the sort of engine oil should be designed, controlled and selected carefully in order to reduce the bearing inside temperature. In this study, the influence of aerated oil on a high-speed journal bearing is also examined by using the classical thermohydrodynamic lubrication theory coupled with analytical models for viscosity and density of air-oil mixture in fluid-film bearing. Convection to the walls and mixing with supply oil and re-circulating oil are considered. The considered parameters for the study of bubbly lubrication are oil inlet port's type, oil aeration level and shaft speed. It is found that the type of oil inlet ports and shaft speed play important roles in determining the temperature and pressure, then the friction and load of journal bearing at high speed operation. Also, the results show that, under extremely high shaft speed, the high shear effects on aerated oil and the high temperature effects are canceled out each other. So, the bearing load and friction show almost no difference between the aerated oil and pure oil.

• Tribology and Lubricants
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• 제23권5호
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• pp.207-218
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• 2007

Turbocharger bearings are under the circumstance of high temperature, moreover rotated at high speed. It is necessary to be designed overcoming the high temperature. So the type of oil inlet port, the inlet oil temperature and the sort of engine oil should be designed, controlled and selected carefully in order to reduce the bearing inside temperature. In this study, the influence of aerated oil on a high-speed journal bearing is also examined by using the classical thermohydrodynamic lubrication theory coupled with analytical models for viscosity and density of air-oil mixture in fluid-film bearing. Convection to the walls and mixing with supply oil and re-circulating oil are considered. The considered parameters for the study of bubbly lubrication are oil inlet port's type, oil aeration level and shaft speed. It is found that the type of oil inlet ports and shaft speed play important roles in determining the temperature and pressure distribution, then the friction in a journal bearing at high speed operation. Also, the results show that, under extremely high shaft speed, the high shear effects on aerated oil and the high temperature effects are canceled out each other. So, the bearing load and friction show almost no difference between the aerated oil and pure oil.

• 설비공학논문집
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• 제15권6호
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• pp.495-501
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• 2003

Control algorithms for the absorption air conditioning system may be developed by using dynamic models of the system. The simplified effective dynamic models, which can predict the dynamic behaviors of the system, may help to develop effective control algorithms for the system. In this study, control algorithms for an absorption air conditioning system were developed by using a dynamic simulation program. A cooling water inlet temperature control algorithm, a chilled water outlet temperature control algorithm, and a supply air temperature control algorithm, were developed and analyzed. The steepest descent method was used as an optimal algorithm. The simulation results showed energy savings and the effective controls of an absorption air conditioning system.

• International Journal of Air-Conditioning and Refrigeration
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• 제12권3호
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• pp.123-130
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• 2004

Control algorithms for an absorption air conditioning system may be developed by using dynamic models of the system. The simplified effective dynamic models, which can predict the dynamic behaviors of the system, may help to develop effective control algorithms for the system. In this study, control algorithms for an absorption air conditioning system were developed by using a dynamic simulation program. A cooling water inlet temperature control algorithm, a chilled water outlet temperature control algorithm, and a supply air temperature control algorithm, were developed and analyzed. The steepest descent method was used as an optimal algorithm. Simulation results showed energy savings and the effective controls of an absorption air conditioning system.

• 한국화재소방학회논문지
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• 제31권4호
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• pp.26-34
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• 2017

본 논문은 거실제연설비의 인접구역 상호제연방식의 성능 확인 및 향상을 위한 논문으로써 국가화재안전기준(NFSC)과 NFPA 연기제어에 관한 규정을 비교 분석하였다. 분석방법은 화재 시뮬레이션(FDS)을 통해 모델링을 실시하여, 급기량 변화, 제연경계의 폭, 화재실내 가연물 변화, 유입공기의 풍속차이를 통해 이루어졌다. 그 결과 청결층 확보를 위해 급기량을 배출량 이하로 하였을때 화재실에서의 청결층 확보에 유리한 것으로 나타났으나 급기실에서는 급기량을 배출량 이상으로 하였을때 청결층 확보에 유리한 것으로 나타났으며, 제연경계의 폭이 길어질수록 성능 확보에 유리한 것으로 나타났다. 또한 가연물의 종류에 따라 급기량과 배출량을 고려해야 하며, 공기유입구 풍속은 급기량을 감소시킴과 동시에 공기유입구 풍속을 낮게 하므로써 화재실의 청결층 확보에 유리한 것으로 나타났다.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2005년도 후기학술대회논문집
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• pp.234-235
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• 2005

In this experiment study, to acquire elementary data for explaining to generate frost layer in the fin - tube evaporator. the experiment condition is to supply air on 0.3m/s, 0.6m/s, 0.9m/s and inlet air temperature is 15$^{circ}C$, 20$^{circ}C$, 25$^{circ}C$ , supplied air relative humidity is 70%, 80, 90%. And brine temperature in the copper tube was kept -15$^{circ}C$ because, generally cooling temperature range is constantly -15$^{circ}C$ in the heat exchanger for air conditioning system. in conclusion, through this experiment, we did compare with frost layer and frost thickness in each condition and examine these data

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2005년도 전기학술대회논문집
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• pp.166-171
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• 2005

In this experiment study, to acquire elementary data for explaining to generate frost layer in the fin - tube evaporator. the experiment condition is to supply air on 0.3m/s, 0.6m/s, 0.9m/s and inlet air temperature is kept constantly $20^{\circ}C$, supplied air relative humidity is 70%, 80, 90%. And brine temperature in the copper tube was kept $-15^{\circ}C$ because, generally cooling temperature range is constantly $-15^{\circ}C$ in the heat exchanger for air conditioning system. in conclusion, through this experiment, we did compare with frost layer and frost quantity in each condition and examine these data

• 한국산학기술학회논문지
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• 제21권4호
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• pp.324-329
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• 2020

비상피난 지원시스템은 화재 발생시 차연막이 형성되고 차연막 내부로 외기를 급기 가압을 해주어 연기의 유입을 막아주어 안전한 대피로를 제공한다. 본 연구에서는 수치해석을 통해 급기구 지름이 10, 15, 20, 30 mm로 변화 할 때 비상피난 지원시스템 차연막 내부에 급기구 크기가 유동에 미치는 영향을 분석하였다. 그 결과 급기구 지름이 감소할수록 비상피난지원 시스템 입구부터 출구 길이 방향으로 급기구를 통한 유량이 비교적 고르게 형성 되는 양상을 보였다. 또한 20 mm 이상으로 급기구를 타공 할 경우 출구부 근처에는 급기 유량이 거의 발생하지 않는 문제점이 발생 하므로 급기구 지름을 20 mm 보다 작게 타공 해야 할 것으로 판단된다. 차연막 내부 공간 압력은 20 mm 이하로 타공시 길이 방향으로 비교적 매우 균일한 분포를 보였다. 또한 수치해석 결과를 이용하여 급기구의 부차 손실계수을 산출 하였으며 약 K=1.5 으로 계산되었다. 따라서 향후 비상피난 지원 시스템 설계시 본 연구에서 도출한 급기구 지름에 따른 유동특성과 급기구의 부차손실을 적용하여 적절한 설계가 수행될 수 있을 것으로 판단된다.

• 한국분무공학회지
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• 제12권1호
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• pp.38-44
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• 2007

Since the Liquid Phase LPG injection (LPLI) system has Advantages in power generation and emission characteristics compared to the mixer-type fuel-supply system, a variety of studies regarding LPLi system has been conducted and its applications are made in automobile industry. However, the heat extraction due to the evaporation of liquid fuel, causes not only a post-accumulation of fuel but also an icing phenomenon which is a frost of moisture in the air around the nozzle tip. Since there exists a difficulty in the accurate control of air fuel ratio in both fuel supply systems, it can result in poor engine performance and a large amount of harmful emissions. This research examines the characteristics of icing phenomenon and develops anti-icing bushing to prevent an icing on the surface of the injection tip. It was found that n-butane, which has a relatively high boiling point ($-0.5^{\circ}C$), was a main species of post-accumulation. Also the results show that the post-accumulation problem was allevaited the utilization of a large inner to outer bore ratio and smooth surface roughness. In addition, an icing phenomenon and its formation process were found to be mainly affected by the humidity and the temperature of inlet air in an inlet duct. Also, it was observed that an icing phenomenon is lessened using aluminum bushing whose end coincides with the end of fuel injection tip in length.

• 한국산업융합학회 논문집
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• 제26권2_2호
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• pp.255-263
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• 2023

The shell and tube-type heat exchangers have been frequently used in many industrial field because of its simple structure and wide operation conditions and so on. The purpose of this study is to investigate the flow characteristics in single shell of shell and tube-type heat exchanger according to velocity and temperature of hot air released from heat exchanger simulator through numerical analysis. As the results, the temperature was decreased in almost quadratic curve from top to bottom in single shell of the shell and tube-type heat exchanger. Further the changes of pressure and velocity in outlet according to change of inlet temperature were not observed. The cost for operating the shell and tube-type heat exchanger should be compared the supply cost of hot air with that of velocity in order to make a economic decision.