In the past decades, numerous resea

In the past decades, numerous researches have been conducted to investigate the heat and mass transport processes inside fuel cell. Experimental studies are mainly focused on effects of operating conditions [18e22] and optimization of structural designs [23e26].To capture the water formation and transport processes, novel visualization techniques such as scanning electron microscopy [27], neutron imaging [28], X-ray radiation [29] and other methods [30,31] have been adopted. Owing to the limitation of experimental measurement, a large number of numerical models have been developed to supplement the parameter distribution such as gas concentrations [32,33], liquid water removal process [34], membrane hydration level [35], and ice volume fraction during the cold start process [36,37]. When single cells are scaled up to stacks, the uniform reactants flow distribution among individual fuel cells becomes an important issue [15,38]. As mentioned above, theoperating conditions of stack (e.g. reactant mass flow rate, pressure, temperature) are actually decided by associate auxiliary subsystems. However, much less attention has been paid to auxiliary subsystems compared with fuel cell studies.