The problem of water management in an open-cathode direct methanol fuel cell (DMFC) is addressed in a quantitative fashion by introducing the definition of the scalar systemwide water management parameter, that characterizes whether at a given steady state the system is effectively losing water (hence operating under a water-discharge mode), preserving its water (water-balance mode), or gaining water (water-recovery mode). The identification of one of these three possible modes is reduced to analyzing the sign of the water balance parameter. A nonlinear DMFC system model is used to characterize the set of steady-state points that define a feasible region of operation where the system is under a water balance mode. Numerical-search algorithms are invoked to identify the boundaries of the feasible region. It is found that the systemwide water balance parameter can be manipulated by adjusting the operating temperature of the DMFC or the current drawn through the system; however, the parameter shows the specific ranges of operating temperature and current density where it is impossible to attain water balance. The feasibility regions for the DMFC system are identified, and used to quantify the extent to which the ambient relative humidity affects the region boundaries.
['Goutham Kotamreddy', 'S.P. Mudiraj', 'Enea Martinoli', 'Oscar D. Crisalle']
Water management in an open-cathode direct methanol fuel cell system