A Lumped-Mass Model of Membrane Humidifier for PEMFC

Abstract

Maintaining the performance of a fuel cell stack requires appropriate management of water in the membrane electrode. One solution is to apply an external humidifier to the supply gases. However, the operating conditions change continuously, which significantly affects the humidifier performance and supply gas characteristics. A straightforward humidifier module is needed for integration with the fuel cell system model. In this study, a lumped-mass model was used to simulate a hollow-fiber membrane humidifier and investigate the effects of various input conditions on the humidifier performance. The lumped-mass model can account for heat transfer and vapor transport in the membrane bundle without losing simplicity. The humidifier module was divided into three parts: a heat and mass exchanger in the middle and two manifolds at the ends of the exchanger. These components were modeled separately and linked to each other according to the flow characteristics. Simulations were performed to determine the humidifier response under both steady-state and transient conditions, and water saturation was observed in the outlet manifold that may affect the humidifier performance. The findings on the effects of the operating conditions and humidifier dimensions on the cathode gas can be used to improve humidifier design and control.

Steady State and Dynamic Simulation of a Small-Scale Hollow Fiber Membrane Humidifier

“…This correlation is also used by Vu, Nguyen, and Yu (2022) to model the shell side convective mass transfer of a hollow fiber humidifier. The packing density is defined as ratio of shell cross sectional area to the cross sectional area occupied by the fibers:…”

“…A previous study (Pollak et al 2023) investigated the same type of humidifier as discussed in our work, but focuses on detailed CFD model that is not suitable for system simulations with transient operation due to its long calculation times. Only few studies discuss transient operation of membrane humidifiers (Chen, Li, and Peng 2008;Park, Choe, and Choi 2008;Yun et al 2018;Vu, Nguyen, and Yu 2022). Three of them do not compare their simulation results to experimental data (Park, Choe, and Choi 2008;Yun et al 2018;Vu, Nguyen, and Yu 2022) and the fourth uses liquid water instead of a wet air flow as humidity source (Chen, Li, and Peng 2008).…”

“…Only few studies discuss transient operation of membrane humidifiers (Chen, Li, and Peng 2008;Park, Choe, and Choi 2008;Yun et al 2018;Vu, Nguyen, and Yu 2022). Three of them do not compare their simulation results to experimental data (Park, Choe, and Choi 2008;Yun et al 2018;Vu, Nguyen, and Yu 2022) and the fourth uses liquid water instead of a wet air flow as humidity source (Chen, Li, and Peng 2008).…”

Bypass Configurations of Membrane Humidifiers for Water Management in PEM Fuel Cells

“…Calculation of the number of transfer units can be carried out using the overall heat transfer coefficient and overall mass transfer coefficient. The coefficients were computed based on the heat conduction and convection for heat transfer, and the mass diffusion and convection for vapor transport at the two surfaces and inside the membranes [18].…”