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

Abstract

Membrane humidifiers are often used in mobile Proton Exchange Membrane (PEM) fuel cell systems to humidify the supply air of the fuel cell. The purpose of a humidifier in a PEM fuel cell system is to prevent a dry-out of the fuel cell membrane. In this paper, a humidifier model based on the number of transfer units (NTU) approach is set-up in Modelica, calibrated and validated using measurement of a test rig. In a first step, the model is evaluated for steady state operating conditions. Second the developed membrane humidifier model is simulated with dynamically changing operating conditions that are typical for mobile applications. Those simulation results are then compared to measurements. The aim of our study is to evaluate the accuracy of the NTU humidifier model under various operating scenarios. Our results indicate that the NTU model is suitable to predict the water transfer under steady state as well as dynamically changing operating conditions with low deviations to measurements.