연료전지 자동차 스택 냉각 시스템 성능 해석 및 평가

Analyses in stack cooling system 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 investigated stack cooling performance of FCEV by means of 3D thermal flow analytic software, UH3D, at the severe condition for cooling, such as high ambient temperature, low vehicle speed and up-hill mode. As a result of 3D simulation, it was estimated that applied FCEV stack cooling system required more heat rejection to cope with this simulation. To improve cooling capacity, several case studies, such as cooling module layout(up and down), a gap between a condenser and stack radiator, distance between stack radiator and fan, and stack location variation, were simulated. Consequently, it was found that cooling performance was improved by max. 1.2% for 20㎜ gap between a condenser and stack radiator. Cooling performance was influenced by the distance between cooling module and stack and BOP components because the recirculation of heated air through cooling module blocked the fresh air, so that cooling air temperature rised. Hence, when the case of no-stack behind cooling module was analyzed, cooling performance was elevated by about 4% because of no-recirculation and more cooling air flow rate. This simulation for no-stack case was considered by the current FCEV developing trend, which fuel cell system was located at under-floor.