Effect of operating parameters on dynamic response of water-to-gas membrane humidifier for proton exchange membrane fuel cell vehicle

•A membrane humidifier model is developed with a pseudo-multi-dimensional concept.•Time constants for mass transfer mechanisms in the humidifier are compared.•The dynamic behavior is mainly due to the thermal resistance and heat capacity.•The performances of sub-systems are closely related in the PEMFC system.

An analytic multi-dimensional dynamic model of a membrane type humidifier has been developed for the study of transient responses of the humidifier under proton exchange membrane fuel cell vehicle operating conditions. The dynamic responses of heat and mass transfer and fluid flow in a membrane humidifier are mathematically formulated and modeled with a newly developed pseudo-multi-dimensional concept. The model is used to analyze the performance of the humidifier under various operating conditions and the dynamic response of the humidifier under transient operating conditions. The simulation results show that, in the case of the water-to-gas type membrane humidifier modeled in this study, the time constant of water diffusion in the membrane is less than 1 s. Thus, the delay of the response of the humidifier induced by the vapor diffusion in the membrane is not significant in vehicle operation. However, it is also found that the dynamic behavior is mainly due to the thermal resistance and heat capacity of the membrane humidifier.