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배석정,이정희,최영기 대한설비공학회 2003 설비공학 논문집 Vol.15 No.11
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.
응축기 전면의 유동 불균일도를 고려한 자동차용 에어컨시스템 해석 프로그램 개발
배석정(Sukjung Bae),허형석(Hyungseok Heo),송경석(Kyungsuk Song) 한국자동차공학회 2006 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
Recently, circumstances for heat exchanger (condenser) in automotive air conditioning system to work have become worse due to curtailment of engine room to enlarge cabin space, abridgement of grille opening to enhance aerodynamic efficiency and diversification of heat source for future fuel cell vehicles. The periods to develope the new cars have become increasingly shorter. These situations have brought the need of performance prediction technique for air conditioning system on board at design stage. This study has developed simulation program for air conditioning system with inlet air flow maldistribution of condenser. The program takes inputs such as air inlet velocity and temperature distribution of condenser and geometries of system components and gives various outputs such as temperatures, velocities and pressures of both fluids - air and refrigerant. Experiments utilizing environmental wind tunnel have been conducted for various working conditions of air conditioning system. The results from program analyses have good agreements with that from experiments. The flow maldistribution in air temperature and/or velocity deteriorates the system performance up to 5%.
엔진 냉각수 제어 시스템의 제어 성능 및 연비 배출 가스 성능 평가
배석정(Sukjung Bae),김현철(Hyunchul Kim),김명곤(Myonggon Kim),허형석(Hyungseok Heo),이기수(Geesoo Lee),이헌균(Heonkyun Lee),홍성훈(Sunghoon Hong) 한국자동차공학회 2008 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
To achieve the goal to meet the worldwide demand for the improvement of fuel efficiency and the reduction of exhaust, the thermal management system of vehicle adopts an adjustable electronic thermostat to vary the valve-open temperature and full-open lift with the operating condition of the vehicle in this study. The control temperature of the engine coolant of the system has been lifted 20℃ than conventional mechanical system so as to improve the fuel efficiency 2% or more. This study describes the procedure of assessment of performance of thermal management system and compares the results of CVS-75 chassis dynamometer tests lor the vehicle ill which mechanical or electronic thermal management system installed.
엔진 폐열 회수 시스템 저온 응축기의 성능 향상을 위한 해석적 접근
배석정(Sukjung Bae),허형석(Hyungseok Heo),조성일(Seongil Jo),박정상(Jeongsang Park),이홍열(Hongyeol Lee) 한국자동차공학회 2012 한국자동차공학회 학술대회 및 전시회 Vol.2012 No.11
The optimum design of the low-temperature condenser of a dual-loop waste heat recovery system with Rankine steam cycles for improving the fuel efficiency of gasoline automobiles has been investigated. The waste heat recovery system consists of a high-temperature (HT) loop in which water as the HT working fluid recovers waste heat only from the exhaust gas of about 700℃ and a low-temperature (LT) loop in which a refrigerant as the LT working fluid recovers heat dissipation from the HT loop, and waste heat from the engine coolant of relatively low temperature. The low temperature condenser plays a role to dissipate heat from the system by condensing the low temperature loop working fluid sufficiently. However, the refrigerant has low evaporation temperature enough to recover the waste from engine coolant but has small saturation enthalpy so that excessive mass flow rate of the LT working fluid, e.g., over 150 g/s, causes the enormously large pressure drop of the working fluid to maintain the heat dissipation performance of more than 20 kW. This paper has dealt with the scheme to design the low temperature condenser that has reduced pressure drop while ensuring the required thermal performance from the waste heat recovery system. For the purpose of the performance predictions and the parametric study for the LT condenser, we have developed a 1-dimensional user-friendly performance prediction program that calculates feasibly the phase change of the working fluid in the tubes. Sustaining the scale of the existing vehicle refrigerant condenser, the number of pass, arrangement of the tubes of each pass and the structural design to enhance the flow uniformity through all the tubes of the multi-flow type low temperature condenser were analytically investigated.
배기 폐열 회수 시스템의 고온 열교환기 설계 및 성능 평가
배석정(Sukjung Bae),허형석(Hyungseok Heo),이동혁(Donghyuk Lee),강태구(Taegu Kang),김태진(Taejin Kim) 한국자동차공학회 2012 한국자동차공학회 부문종합 학술대회 Vol.2012 No.5
A dual loop waste heat recovery system with Rankine steam cycles for the improvement of fuel efficiency has been investigated. This paper deals with performance analysis and evaluation of heat exchangers on the exhaust gas side for the design of them. The HT boiler and the HT superheater are placed along the exhaust line. In the HT boiler, the working fluid compressed by the pump becomes saturated by the recovery of heat of exhaust gas. On the other hand, in the HT superheater, the working fluid becomes superheated as it recovers heat of upstream exhaust gas coming out from the exhaust manifold. An analysis program was developed to design the HT superheater and the HT boiler. For the performance evaluation of each component, inlet temperature was set 5℃ of sub-cool and 5℃ of super-heat at the high pressure on the condition of designed evaporating pressure. The predictive value and the result of thermal performance evaluation was consistent on the average value within 5%. In addition, the another experiments were performed with the HT superheater and the HT boiler connected in series. The inlet temperature was set 5℃ of sub-cool at the low pressure of the system and outlet temperature was set the degree of 300℃.Using the result of this paper, the design criteria of a high temperature heat exchanger will be established for the exhaust heat recovery system.
전기자동차용 6 ㎾급 CNT 히터의 내열 구조강도 해석 설계
배석정(Sukjung Bae),이현석(Hyunseok Lee),이준용(Junyong Lee),허형석(Hyungseok Heo),이병호(Byongho Lee),김영삼(Youngsam Kim) 한국자동차공학회 2021 한국자동차공학회 부문종합 학술대회 Vol.2021 No.6
Since electric vehicles lack of heat source as engine of internal combustion vehicles, additional electric heaters have to be used for cabin heating in winter. Thus PTC heaters, which heat air entering cabin by electric heating, are generally used in electric vehicles. However, the existing type of heaters require so high power consumption that the mileages of electric vehicles significantly decreases. Carbon nano tube heating elements generates heat to distribute temperature uniformly in their film geometries and improves heat-up rate compared to conventional PTC elements with their high thermal conductivity as described in our previous study dealt with performance assessment of the heaters. In this study, CNT heater alone model and controller integrated model with an additional controller part on the heater have been modeled and thermal stress analysis has been performed to ensure stability against thermal stress caused by temperature differences in comparison. The controller integrated model shows slightly lower maximum stress than heater alone model, which both model have the maximum values within the ranges of yield strength of the materials.
전자빔 합성 방식 연료전지 촉매 반응기의 냉각 성능 설계
배석정(Sukjung Bae),허형석(Hyungseok Heo),양대수(Daesoo Yang),윤영철(Yeongcheol Yoon) 한국자동차공학회 2022 한국자동차공학회 부문종합 학술대회 Vol.2022 No.6
For the purpose of reduction of fossil fuel-based energy share and ultimately taking it over, researches on fuel cells that convert chemical energy into electrical energy have been actively conducted over the past few decades. Catalyst used to activate the oxygen reduction reaction in the reduction electrode of the fuel cell is a core material that determines the power generation efficiency by allowing the chemical reaction rate to be adjusted. Hydrated electrons accelerated close to a light speed having a powerful reducing force among various chemical species generated by water decomposition are able to reduce metal ions in a short time by irradiating electron beams to an aqueous solution including a metal precursor, thereby uniformly producing nanometer-sized catalyst particles on the surface of carbon carriers. In this study, reactor cooling performance has been designed to remove the heat generated inside the reactor. Cooling performance characteristics of precursor sample of catalyst have been analyzed according to several reactor models. The performance analysis has been performed according to coolant inlet conditions and mixer geometries.