• 설비공학논문집
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• 제14권4호
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• pp.293-303
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• 2002

For successful design of component, performances of one-tank plate type evaporator, gas-liquid separation type condenser, swash plate type compressor and thermostatic expansion valve for automotive air conditioner are investigated experimentally. Heat transfer characteristics in the evaporator are examined by means of air temperature, relative humidity, air volume flow, outlet refrigerant pressure and superheat, and heat transfer characteristics in the condenser are examined by means of air temperature, air velocity and inlet refrigerant pressure. Pressure drops for both evaporator and condenser are measured arid empirical correlations are derived. Volumetric efficiencies and isentropic efficiencies for trio types of compressors with different capacity are measured and compared. Thermostatic expansion valve is tested to investigate the pressure variation according to temperature changes.

• 한국정밀공학회지
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• 제14권8호
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• pp.146-154
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• 1997

Solenoid-folw control type ABS is used with a 'dump and reapply' pressure control arrangement instead of using 2/2 (normal open/close) solenoid valves in convensional systems(sol. -sol. control type), a flow control valve is used which replaces the (no) inlet valve. The flow control valve controls fluid flow providing a nearly constant reapply rate( .theta. ) after the dump plase of ABS operation. In this study, to investigate a characteristics of brake pressure by PWM control, test rig was consisted of ABS hydraulic modulator, digital controller, pneumatic power supply and brake master cylinder. For comparison with experi- mental results, system modelling and computer simulation were performed. As a result, experiment results showed fairly agreement with the simulation. Also, it is shown that the pressure gradient (tan .theta. ) is affected by pressure, frequency, duty ratio and expressed with an exponential funtion.

• 동력기계공학회지
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• 제14권4호
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• pp.43-49
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• 2010

In the present study, optimization of throttle margin for high pressure turbine to be retrofitted or partially modified for power uprating or life extension in nuclear power plant, has been performed to increase the electrical output. Throttle margin for high pressure turbine is required to maintain all the time the rated power by opening more of governor valves whenever inlet pressure is decreased due to the tube plugging of steam generator. If throttle margin of high pressure turbine is too much compared to remaining lifetime, loss of electrical output due to pressure drop of governor valves is inevitable. On the contrary, if it is too little, the rated power operation can not be accomplished when inlet pressure of high pressure turbine is dropped after many years operation. So, throttle margin for high pressure turbine in nuclear power plant is compromised considering for the degradation of steam generator, governor valve capacity, manufacturing tolerance of high pressure turbine, future plan of power uprating, and remaining lifetime of power plant.

• 상하수도학회지
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• 제29권5호
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• pp.559-564
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• 2015

Distribution basins are used widely in the water treatment process. Uniform distribution at the distribution basin is an important because it affect precipitation efficiency of sedimentation basin. Generally distribution basin has a free surface water and is consisted of a weir. Study result, when inflow of distribution basin is less, amount of overflow is much at the nearest weir from the inlet. But when inflow is much, amount of overflow is much at the far weir from the inlet. The difference of distribution amount at the pipe is affected by the curvature and length of the pipe. The magnitude of the effect is determined by the relative energy loss and the flow state of the distribution basin. Optimization of the response surface method for minimizing an amount of deviation of the distribution is a very useful technique to determine the optimal ratio of the valve opening.

• 동력기계공학회지
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• 제14권5호
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• pp.36-40
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• 2010

The ultrasonic guided wave propagates along with the given structure's wall direction. Because of this specific character, the ultrasonic guided waves arc used in many other fields. Especially, it can be readily utilized for nondestructive inspection of various structures that are made up of gas pipes, heat exchanger tubes, and thin plates. Further, the guided wave technology can be readily utilized when inspecting pipes or thin plates which pose high risk of the accident but for which the nondestructive inspection itself is impossible because it is difficult to get to them since they are coated or buried underground. In the other hand, conventional ultrasonic testing such as thickness gauging uses bulk waves and only tests the region of structure immediately below the transducer. As a result of the application about inlet and outlet cooling water line using guided wave test, we conformed that the overall corrosions were in the lower side of the 304.8 mm inlet valve and these corrosions were engaged in not locally but through the lower side of the valve line. In the near future, we can expect that the detectable defect size is smaller than before along with the development of the sensing technology.

• 설비공학논문집
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• 제20권5호
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• pp.295-303
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• 2008

The objectives of this study are to predict actual system performance and effective operating range of the 2-stage compression heat pump system using river water. An electronic expansion valve was applied to the simulation to analyze the effects of operating conditions on the system performance. The developed program was verified by comparing the predictions with the measured data. The results from the present model showed a good agreement with the measured data. In addition, the heat pump simulation was conducted by increasing condenser reservoir inlet temperature to investigate the benefits of the 2-stage compression over the 1-stage compression in the heating mode. The performance of the 2-stage compression cycle was better than that of the 1-stage compression when the inlet temperature of the condenser reservoir was higher than $40^{\circ}C$.

• Nuclear Engineering and Technology
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• 제56권5호
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• pp.1902-1912
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• 2024

This paper presents results from system-level modeling of a water-based reactor cavity cooling system using RELAP5-3D. The computational model is benchmarked with experimental data from a half-scale RCCS test facility at Argonne National Laboratory. The model prediction is first compared with a two-phase oscillatory baseline experimental case where mixed accuracy is obtained. The model shows reasonable prediction of mass flow rate, pressure, and temperature but significant overprediction of void fraction. The model prediction is then compared with a fault case where the inlet of the risers is gradually reduced using a throttling valve. As the valve is closed, the model is able to predict some major flow phenomena observed in the experiment such as the dampening of oscillations, the reintroduction of oscillations, as well as boiling, flashing, and geysering in the risers. However, the timeline of these events are not well captured by the model. The model is also used to investigate the evolution of flow regime in the chimney. This work highlights that the semi-empirical constitutive relations used in RELAP-3D could have a strong influence on the accuracy of the model in two-phase oscillatory flows.

• 한국기계가공학회지
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• 제14권5호
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• pp.42-49
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• 2015

In this study, the multi-disk of a high-pressure drop control valve is designed and manufactured. Then, the flow rate and high-pressure drop of fluids flowing in the high-pressure drop control valve is CAE/CFD. This study involves numerical analysis for the Zambil offshore project of a high-pressure drop control valve. ANSYS used a solver for offshore structures analysis. A high-pressure drop control valve, which transforms the power transfer of a system by reducing the inlet pressure of 345bar to the outlet pressure of 112bar, is a fundamental component in the offshore process. This study not only analyzes the relation between pressure drop and fluid velocity in a trim by using fluid analysis, but also examines the possibility of cavitation in a valve in addition to the plot for the extension of lifespan. It is demonstrated that the pressure drop from 345bar to 112bar is more feasible in the presence of the trim, which can induce a continuous and diminutive pressure drop in order to prevent cavitation in a high-pressure drop control valve.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.243-247
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• 2004

The dynamometers which had made in a long time ago could not control the input/output quantity of water minutely and was sensitive to a noise since it was controlled by an analog control method. Therefore, a fully digital controlled system was urgently required to be robust against various noises. In this paper, the new system which can control the amount of circulated water in dynamometer was developed. This system is consisted of an industrial digital type controller and a servo motor. The industrial PLC was used as a main controller for the developed system, and the actuator and servo motor were used to control the inlet and outlet valve independently. The torque signal of load cell was fed back to the main controller to regulate the diesel engines load. Generally, an input/output valve position of the old dynamometer was fixed with a proper situation for an engine output test and the torque was changed according to the time interval. However, the torque value for the dynamometer could not be constantly kept because of the variation of the input water flow and fluid characteristic. Therefore, the automatic control of an inlet and outlet valve should be performed to keep the constant torque. So, the PID control method was applied to solve this problem. Also, the development of a web-based remote control system was described in this paper. This software will give us the convenience of operation, the more efficient operations, and the reduced operator workload for operation of the dynamometer. The application results of the system have been verified at actual diesel engine field.

• Journal of Chest Surgery
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• 제30권7호
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• pp.719-723
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• 1997

저자들은 대동맥 판막치환술 후 생긴 대동맥 판막 주위 누출과 관련된 대동맥동류의 심실 중격 박리를 경험하였다. 37세 남자 환자가 호흡 곤란의 증가를 주소로 응급실을 통하여 입원하였다. 그는 6년전 대동맥판 폐쇄 부전과 승모판 폐쇄 부전으로 인공 기계 판막(Carbomedic 23mm와 31mm)으로 치환 수술을 받고 정기적으로 추적 검진 중이었다. 진단은 경흉부및 경식도 심초음파로 이루어졌고, 대동맥 조영술로 확인되었다. 폐동맥판 동종이식편(Pulmonary homoyaft)를 사용하여 대동맥 판막 치환술을 다시 시행하였다. 심실중격내의 낭 입구에서 3-0 prolene을 사용하여 심근 내막, 외막과 homograft muscle shoulder를 한꺼번에 연속 봉합하였다. 술후 경과는 양호하여 환자는 수술 후 11일째 퇴원하였다.