CFD investigation of a fast-response humidifier for high-power PEMFC test stations.

Unlike operating PEMFC systems with internal humidification from hydrogen recirculation, fuel cell stack test stations mainly rely on external humidification. Response time in the order of 10s and power over 100 kW are crucial requirements for test stations for vehicle fuel cell stacks. In the present study, a 3D computational fluid dynamics (CFD) model of a swirl spray humidifier is developed to simulate the conjugated heat and mass transfer in such a humidifier. In the model, hot, dry air enters from the bottom portion of the humidifier tangentially and mixes with liquid droplets from a nozzle placed near the middle. A discrete phase model (DPM) is employed to model the atomized droplets. Time variations of the flow structure and humidity distribution are studied. A parametric study with the nozzle parameters on humidifier performance is carried out, showing that optimal humidifier performance can be obtained with a single nozzle and spray temperature at 300 K. The humidity response at the humidifier exit subject to a load change is investigated. The simulation results show that the humidifier's dynamic response time for the baseline case is about 32s, with a steady relative humidity of 95.25% and an evaporation rate of 98.4% at the exit. The present model can guide the future design of fast-response, high-power humidifiers for fuel cell stack test stations. [Display omitted] • A CFD model of a fast-response humidifier for PEMFC test stations is developed. • The flow structure and capabilities of the humidifier are studied. • A parametric study and an investigation of the humidifier's dynamic response are carried out. [ABSTRACT FROM AUTHOR]