Analysis of Surrogate Models for Vapour Transport and Distribution in a Hollow Fibre Membrane Humidifier

Abstract

To achieve high efficiency and low degradation of a polymer electrolyte fuel cell (PEMFC), it is necessary to maintain an appropriate level of humidification in the fuel cell membrane. Thus, membrane humidifiers are typically used in PEMFC systems. Parameter studies are important to evaluate membrane humidifiers under various operating conditions to reduce the amount of physical tests. However, simulative studies are computationally expensive when using detailed models. To reduce the computational cost, surrogate models are set up. In our study, a 3D computational fluid dynamics (CFD) model of a hollow fibre membrane humidifier is presented and validated using measurement data. Based on the results of the validated CFD model, a surrogate model of the humidifier is constructed using proper orthogonal decomposition (POD) in combination with different interpolation methods. To evaluate the surrogate models, their results are compared against reference solutions from the CFD model. Our results show that a Halton design combined with a thin-plate-spline interpolation results in the most accurate surrogate humidifier model. Its normalised mean absolute error for 18 test points when predicting the water mass fraction in the membrane humidifier is 0.58%. Furthermore, it is demonstrated that the solutions of the POD model can be used to initialise CFD calculations and thus accelerate the calculation of steady state CFD solutions.

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

“…Adopted from (Pollak et al 2023) investigated humidifier is available from the company Fumatech (FUMATECH BWT GmbH 2019) and was investigated using a CFD model and simulation in a previous study (Pollak et al 2023). The material of the hollow fiber membranes is undisclosed by the manufacturer (Pollak et al 2023). The relevant geometrical data of the fibers and the housing are given in Table 1.…”

“…Since the membrane permeability is not disclosed by the manufacturer it is considered to be a calibration parameter of the humidifier model that must be identified by a calibration process using the measurement data. This calibration result is than compared to a fitting result of a previous study that used a CFD model (Pollak et al 2023).…”

“…Most of the studies in the literature focus on steady state operating conditions when assessing membrane humidifiers, e.g. (Cahalan et al 2017;Nguyen, Vu, and Yu 2021;Pollak et al 2023). 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.…”

“…(Cahalan et al 2017;Nguyen, Vu, and Yu 2021;Pollak et al 2023). 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).…”

“…We use measurement data from a test rig to calibrate and validate the model for steady state and transient operating conditions. Furthermore, the calibration results of the model are compared to the results of a computational fluid dynamics (CFD) model of the same humidifier that was developed in a previous study (Pollak et al 2023). The motivation for using Modelica to develop the humidifier model is the possibility to describe the humidifier model in an object-oriented way.…”