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조중원(Choong-Won Cho),원종필(Jongphil Won),이호성(Hoseong Lee),이동혁(Donghyuk Lee),오태성(Tae Sung Oh),박용선(Yong Sun Park) 한국자동차공학회 2009 한국자동차공학회 학술대회 및 전시회 Vol.2009 No.11
Ethylene glycol is generally mixed with water as antifreezing solution in a thermal management system for a fuel cell vehicle, but there are significant differences between ethylene glycol and water. For example, ethylene glycol has much higher viscosity than that of water. These differences in physical property lead to reduction in heat transfer rate of the thermal management system. this study describes the characteristics of heat transfer in a stack and a radiator respectively, because flows in the stack is laminar. Empirical correlation is used to calculate physical properties of antifreezing coolant. In this study, we show that use of the antifreezing solution causes increase in temperature difference between coolant input and coolant output of the stack. this temperature rise effects the performance of the fuel cell stack.
자동차용 대체냉매 직접팽창 시스템 성능 평가를 위한 실험적 연구
이호성(Hoseong Lee),원종필(Jongphil Won),조중원(Choongwon Cho),임택규(Taekkyu Lim),정영철(Youngchul Jung),김용찬(Yongchan Kim) 한국자동차공학회 2012 한국자동차공학회 부문종합 학술대회 Vol.2012 No.5
The aim of this study is to investigate the performance of air conditioning system for alternative refrigerants with the direct expansion system. Due to environmental regulation as a global issue, R-134a, present mobile A/C refrigerant, need to be substituted before long. Among possible alternative refrigerants, R-1234yf has been highly regarded in Mobile Air Conditioning System(MACS) because of similar operating pressure characteristic and technologies to apply have been studied. In this study, R-1234yf and R-744, which have direct expansion system like the present refrigerant, were analyzed on the performance, such as cooling capacity and coefficient of performance(COP), compared to R-134a. As the results of various experiments which were fulfilled like real operating conditions on the road, averaged cooling capacity of R-1234yf was about 96.0 % while that of R-744 was about 97.0 % compared to R-134a and in case of averaged COP, R-1234yf was about 92.0 % while R-744 was about 70 % . From this, R-1234yf and R-744 need additional technical developments to cope with insufficient performance, such as internal heat exchanger re-design and expansion valve"s set-up value. Further studies of improved alternative refrigerant A/C system with the direct expansion will be required to change a refrigerant for MACS.
고효율 자동차 전자장비 냉각 시스템 성능 향상을 위한 해석적 연구
이호성(Hoseong Lee),원종필(Jongphil Won),조중원(Choongwon Cho),임택규(Teakkyu Lim),이대웅(Daewoong Lee),권대복(Daebok Kwon) 한국자동차공학회 2010 한국자동차공학회 부문종합 학술대회 Vol.2010 No.5
The aim of this study is to investigate the performance and the fluid dynamic behavior of application of proto electric device’s cooling system for high efficient vehicle in severe driving condition in terms of engine and electric devices’ cooling. In this study, optimum layout of extra heat exchanger for electric device cooling has been simulated and analyzed by 3-D thermal flow analytic software, UH3D. In spite of extra cooling system for high efficient vehicle, cooling module layout is being considered as 2 column due to confined engine room and pedestrian’s protection. For this reason, unified heat exchangers with combination of two kinds of engine/electric device and condenser/electric device were studies to find out better solution in terms of cooling performance. As results of 3D analysis, combination of condenser/electric device cooling heat exchanger is considered as the effective way for a vehicle optimum cooling module because of less influence on condenser heat rejection and more heat transfer area for engine cooling system. From further studies, such as the variation of cooling module location and interval between 2 column of cooling module, additional performance improvement for electric device cooling system seems to be achieved.
연료전지 스택 배열을 활용한 CO₂ 난방 시스템 배열열교환기 성능 특성에 관한 실험적 연구
이호성(Hoseong Lee),원종필(Jongphil Won),조중원(Choongwon Cho),임택규(Taekkyu Lim),모지환(Jihwan Mo),김용찬(Yongchan Kim) 한국자동차공학회 2010 한국자동차공학회 학술대회 및 전시회 Vol.2010 No.11
The aim of this study is to investigate the performance characteristics of CO₂ Heat Pump(H/P) system using the stack cooling coolant / refrigerant heat exchanger for fuel cell electric vehicles(FCEV). The present heating system for FCEV uses PTC heater, which results in lower fuel efficiency and reduction of driving range. To cope with heating performance improvement without additional power consumption, one of possible methods is to use stack coolant heat for FCEV. Due to high pressure and temperature operating condition for CO₂, CO₂ heat pump has been concerned that it seems to cover heating capacity with the similar capacity of engine coolant heating system. Furthermore, CO₂ heating system is free of environmental regulations for a vehicle refrigerant. In this study, experiments to analyze heating performance characteristics using the coolant / refrigerant heat exchanger have been done with various operating conditions, which are likely to match the actual vehicle’s driving conditions under cold ambient conditions, such as variation of coolant flow rate and interior air temperature. Experimental results show that the heating capacity has Max. 9.5 ㎾ @ coolant temperature 60℃, interior air outlet temperature is up to 45℃ @ ambient temperature -20℃, and the capacity of the coolant / refrigerant heat exchanger is 6.5 ㎾ @ coolant temperature 60℃. From various experimental results, optimal coolant flow rate to have optimum heating performance seems to exist under a certain ambient temperature(5.0 LPM@ ambient temperature -20℃)
연료전지 자동차 열관리 시스템 상호 영향도 분석을 위한 실험적 연구
이호성(Hoseong Lee),원종필(Jongphil Won),조중원(Choongwon Cho),이무연(Mooyeon Lee),정영철(Youngchul Jung),김용찬(Yongchan Kim) 한국자동차공학회 2011 한국자동차공학회 학술대회 및 전시회 Vol.2011 No.11
Experiments of thermal management system(TMS) with the variation of operating conditions for fuel cell electric vehicle(FCEV) has been performed. The amount of heat discharge for FCEV stack cooling system is approximately up to 2 times more than that for conventional internal combustion vehicle due to low temperature difference between coolant inlet and air inlet. This paper studied stack cooling performance characteristics with TMS operating modes, such as stack cooling heat exchanger only(Mode 1), cooling system operation(Mode 2), and cooling and A/C system operation(Mode 3). As test modes are changed, heat load to stack cooling heat exchanger will increase due to the rise of ITD(Inlet temperature difference between cooling air and coolant). As results of various experiments, compared between mode 1 and mode 3, performance at the stack cooling viewpoint decreased up to 34.0 % with fixed operating conditions. As cooling air velocity rises, heat load increment gets less due to enough cooling air flow rate. Indoor and outdoor air conditions influence A/C system, which leads heat load change to stack cooling heat exchanger with the variation of heat rejection rate. In this study, as outdoor temperature increases, heat rejection rate from the condenser increases, which stack cooling performance decreases. To optimize the performance of TMS containing heat exchangers, the irreversibilities of individual heat exchangers must be minimized, Therefore, entropy change of stack cooling heat exchanger was analyzed and the relationship between entropy generation and cooling air velocity was studied.