• 설비공학논문집
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• 제15권11호
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• pp.943-956
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• 2003

A numerical program has been developed for the simulation of automotive engine cooling system. The program determines the mass flow rate of engine coolant circulating the engine cooling system and radiator cooling air when the engine speed is adopted by appropriate empirical correlation. The program used the method of thermal balance at individual element through the model for radiator component in radiator analysis. This study has developed the program that predicts the coolant mass flow rate, inlet and outlet temperatures of each component in the engine cooling system (engine, transmission, radiator and oil cooler) in its state of thermal equilibrium. This study also combined the individual programs and united into the total performance analysis program of the engine cooling system operating at a constant vehicle speed. An air conditioner system is also included in this engine cooling system so that the condenser of the air conditioner faces the radiator. The effect of air conditioner to the cooling performance, e.g., radiator inlet temperature, of the radiator and engine system was examined. This study could make standards of design of radiator capacity using heat rejection with respect to the mass flow rate of cooling air. This study is intended to predict the performance of each component at design step or to simulate the system when specification of the component is modified, and to analyze the performance of the total vehicle engine cooling system.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.811-814
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• 2001

Warpage analysis of bobbin, molded by injection molding process was performed. Concerned with a mold design, cooling system was designed based on Taguchi method, the distance between cavity wall and cooling channel was most influent factor amongst four design variables like an inlet temperature of coolant, a coolant flow rate, a diameter of cooling channel, and the distance between cavity wall and cooling channel. Optimal packing processes to reduce the warpage of molded part was analyzed based on the response surface method by considering holding pressure. Their optimal processing conditions were 9.4 seconds, 5.3 seconds, 15.2 seconds, and 85MPa, respectively.

• 설비공학논문집
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• 제13권5호
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• pp.398-410
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• 2001

The flow and heat transfer characteristics for three-dimensional mixed convection flows in a radiator flat tube with U--shaped grooves are analyzed numerically. The flow and temperature fields are calculated by using the modified SIMPLE algorithm for irregular geometry. One tube specification among the various flat tube exchangers is recommended by considering the heat transfer and pressure drop. The effects of variation of coolant flow conditions and external air conditions on the flow and the thermal characteristics for the selected tube are investigated. the results show that inlet velocity of coolant flow is the very important factor in heat transfer and pressure drop, and top side is better position than the others as fin cleave to tube.

• 한국자동차공학회논문집
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• 제16권1호
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• pp.37-44
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• 2008

The global warming potential (GWP) of $CO_2$ refrigerant is 1/1300 times lower than that of R134a. Furthermore, the size and weight of the automotive heat pump system can decrease because $CO_2$ operates at high pressure with significantly higher discharge temperature and larger temperature change. The presented $CO_2$ heat pump system was designed for both cooling and heating in fuel cell vehicles. In this study, the performance characteristics of the heat pump system were analyzed for heating, and results for performance were provided for operating conditions when using recovered heat from the stack coolant. The performance of the heat pump system with heater core was compared with that of the conventional heating system with heater core and that of the heat pump system without heater core, and thus the heat pump system with heater core showed the best performance among the selected heating systems. On the other hand, the heating performance of two different types of coolant/air heat pump systems with heater core was compared each other at various coolant inlet temperatures. Furthermore, to use exhausted thermal energy through the radiator, experiments were carried out by changing the arrangement of a radiator and an outdoor evaporator, and quantified the heating effectiveness.

• 오토저널
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• 제9권3호
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• pp.55-65
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• 1987

This paper presents the method of piston temperature measurement and its data under various engine operating conditions. In case of high speed engine, the thermocouple wires must be guided from moving piston to stationary place with carful attention. for this purpose L_LINK SYSTEM was made and assembled to a passenger car engine on the test bench and then the piston temperature was successfully measured. The tested engine speed ranged from 1,000 to 4,000 rpm with 500 rpm increments. Not only the effects of engine speed and load on the piston temperature but those of spark timing, detonation, coolant temperature and Reynolds number based on inlet air condition were studied form the measurement obtained by this L_LINK SYSTEM.

• Nuclear Engineering and Technology
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• 제53권10호
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• pp.3275-3285
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• 2021

A Nuclear Power Plant (NPP) is a complex dynamic system-of-systems with highly nonlinear behaviors. In order to control the plant operation under both normal and abnormal conditions, the different systems in NPPs (e.g., the reactor core components, primary and secondary coolant systems) are usually monitored continuously, resulting in very large amounts of data. This situation makes it possible to integrate relevant qualitative and quantitative knowledge with artificial intelligence techniques to provide faster and more accurate behavior predictions, leading to more rapid decisions, based on actual NPP operation data. Data-driven models (DDM) rely on artificial intelligence to learn autonomously based on patterns in data, and they represent alternatives to physics-based models that typically require significant computational resources and might not fully represent the actual operation conditions of an NPP. In this study, a feed-forward backpropagation artificial neural network (ANN) model was trained to simulate the interaction between the reactor core and the primary and secondary coolant systems in a pressurized water reactor. The transients used for model training included perturbations in reactivity, steam valve coefficient, reactor core inlet temperature, and steam generator inlet temperature. Uncertainties of the plant physical parameters and operating conditions were also incorporated in these transients. Eight training functions were adopted during the training stage to develop the most efficient network. The developed ANN model predictions were subsequently tested successfully considering different new transients. Overall, through prompt prediction of NPP behavior under different transients, the study aims at demonstrating the potential of artificial intelligence to empower rapid emergency response planning and risk mitigation strategies.

• KSBB Journal
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• 제18권5호
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• pp.418-423
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• 2003

발효조의 냉각수 공급 제어 신호와 냉각수의 유출입 지점의 온도를 온라인으로 측정하여 이 값들로부터 냉각량을 추정할 수 있는 실험식을 얻었다. 회분식 배양을 통하여 냉각량이 온라인으로 측정될 수 있음을 확인하였고 기질의 재투입시 냉각량의 변화를 통하여 유가배양의 제어변수로 활용할 수 있음을 점검하였다. 미리 프로그램된 목표 냉각량의 증가곡선에 따라 냉각량이 증가되면서 세포가 자라도록 유가배양을 실시하였다. 본 연구를 통하여 냉각량의 온라인 측정방법을 제시하였고 이를 유가배양 제어변수로 활용하여 세포의 성장속도를 조절할 수 있음을 보였다.

• 한국자동차공학회논문집
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• 제15권3호
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• pp.10-17
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• 2007

Design of experiments (DOE) technique has been used to design an exhaust heat exchanger to reduce the exhaust gas temperature under high load conditions in a spark-ignition engine. The DOE evaluates the influence and the interaction of a selected eight design parameters of the heat exchanger affecting the cooling performance of the exhaust gas through a limited number of experiments. The heat exchanger was installed between the exhaust manifold and the inlet of the close-coupled catalytic converter (CCC) to reduce thermal aging. To maximize the heat transfer between exhaust gas and coolant, fins were implemented at the inner surface of the heat exchanger. The design parameters consist of the fin geometry (length, thickness, arrangement, and number of fin), coolant direction, heat exchanger wall thickness, and the length of the heat exchanger. The acceptable range of each design parameter is discussed by analyzing the DOE results.

• Nuclear Engineering and Technology
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• 제55권4호
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• pp.1448-1459
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• 2023

A key element of the safety analysis is Loss of Coolant Analysis (LOCA) which must be performed using system thermal-hydraulic codes. These codes are extensively validated against separate effect and integral experiments. RELAP/SCDAPSIM is one such code that may be used to predict LBLOCA response in a CANDU reactor. The RD-14M experiment selected for the Best Estimate Plus Uncertainty study is a 44 mm (22.7%) inlet header break test with no Emergency Coolant Injection. This work has two objectives first is to simulate pipe break with RELAP and compare these results to those available from experiment and from comparable TRACE calculations. The second objective is to quantify uncertainty in the fuel element sheath (FES) temperature arising from model coefficient as well as input parameter uncertainties using Integrated Uncertainty Analysis package. RELAP calculated results are found to be in good agreement with those of TRACE and with those of experiments. The base case maximum FES temperature is 335.5 ℃ while that of 95% confidence 95^th percentile is 407.41 ℃ for the first order Wilk's formula. The experimental measurements fall within the predicted band and the trends and sensitivities are similar to those reported for the TRACE code.

• 한국압력기기공학회 논문집
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• 제19권2호
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• pp.109-116
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• 2023

This study presents a CRUD modelling to simulate the thermal resistance behavior of CRUD, deposited on the surface of a cladding tube of a fuel assembly. When heat produced from fuels transfers to a coolant through a cladding tube, the CRUD acting as an additional thermal resistance is expressed as two layers, i.e., a solid oxide layer and an imaginary fluid layer, which are added to the experimental tube's heat structure of the MARS-KS input data. The validation calculation for the experiments performed in UNIST-DISNY facility showed that the center and surface temperatures of the cladding tube increased as the porosity and the steam amount inside pores of the CRUD got higher. In addition, the temperature gradient in the imaginary fluid layer was calculated to be larger than that in the solid oxide part, indicating that the steam amount inside the layer acted more largely as thermal resistance. It was also evaluated through sensitivity calculations that the cladding tube temperature was more sensitive to the CRUD porosity and the steam amount in pores than to the inlet flow rate of the coolant.