Experimental and simulative analysis of the dependence between liquid water amount and mass transfer in a planar membrane humidifier

Mull S, Weiß L, Wensing M (2024)

Publication Language: English

Publication Type: Conference contribution, Abstract of lecture

Publication year: 2024

Event location: Baden CH

Abstract

In the field of polymer electrolyte membrane fuel cell systems (PEMFCS), the literature currently distinguishes between two different operating modes for membrane humidifiers with perfluorosulfonic acid (PFSA) membranes. The first operating mode is the vapour transferred from gaseous stream to another, which is mainly used in automotive applications. The other operating mode is the exchange of water from a liquid to a gaseous aggregate state, which is mainly used in stationary test benches. Intermediate states of the humidifier, in which the membrane is partially covered or fully covered with a thin film of liquid water, are presently not part of the literature. These mixed states already occur in mobile PEMFCS in current applications, depending on the operating point and the architecture of the system, among other things. Fundamentally, due to the so-called Schröder's paradox, water transport through PFSA membranes is strongly improved if the water originates from the liquid state instead of the gaseous state [1]. Investigations by the author have recently indicated [2] that the humidifier can achieve maximum water transport at much lower water quantities compared to the boundary conditions currently used in stationary operation. Complete wetting of the membrane with a thin layer of water seems to be sufficient to maximize the performance of the humidifier. This means that the performance of the membrane humidifier can be optimized with the system water management enabling a more efficient use of water and thus a more efficient fuel cell system. This effect has been investigated using a specially developed, optically accessible single channel humidifier test stand. In addition, the author has already developed a simulation model in previous work, which is able to simulate these intermediate operating modes of the humidifier [2]. The investigations focus on the dependence of the minimum amount of liquid water required for the described effect on the possible thermodynamic boundary conditions of a humidifier for automotive PEMFCS, such as the temperature, the air and water flow rates and the pressure. Figure 1 shows an exemplary measurement in which the operating case of complete flooding by a water column is compared with an operating mode with a thin film of water on the membrane surface. The gas mass flow rate of the dry side is varied. Both operating modes achieve almost the same water transfer and therefore similar relative humidities (RH) at the outlet of the dry flow. This shows the effect described above that significantly less water is sufficient for the maximum water transfer ratio and therefore the maximum humidifier performance.

Authors with CRIS profile

Sophie Mull Professur für Fluidsystemtechnik Lukas Weiß Professur für Fluidsystemtechnik Michael Wensing Professur für Fluidsystemtechnik

How to cite

APA:

Mull, S., Weiß, L., & Wensing, M. (2024, March). Experimental and simulative analysis of the dependence between liquid water amount and mass transfer in a planar membrane humidifier. Paper presentation at 20th Symposium on Modeling and Experimental Validation of Electrochemical Energy Technologies (ModVal 2024), Baden, CH.

MLA:

Mull, Sophie, Lukas Weiß, and Michael Wensing. "Experimental and simulative analysis of the dependence between liquid water amount and mass transfer in a planar membrane humidifier." Presented at 20th Symposium on Modeling and Experimental Validation of Electrochemical Energy Technologies (ModVal 2024), Baden Ed. Sophie Mull, 2024.

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