발포금속을 이용한 고분자 전해질 연료전지용 막가습기의 열·물질전달 특성에 관한 연구

Abstract

Polymer electrolyte membrane fuel cell (PEMFC) are being explored as a potential replacement for propulsion systems for mobile applications, given that they can increase a system's fuel efficiency, prevent environmental pollution, and help to downsize engine systems.

Humidity control inside the PEMFC stack can greatly affect the performance of the PEMFC. If the humidity level is low, the membrane can dry to decrease the hydrogen ion conductivity. Conversely, if the humidity is high, the water overflows and can interfere with the chemical reaction. Therefore, a humidifier must be precisely designed to control humidity, while a high efficiency must be obtained for miniaturization.

In this study, we suggest filling the gas channel of the humidifier with porous metal foam to increase the efficiency of the humidifier. This material has a high porosity and surface area density, making it ideal to prevent pressure drops and increase the efficiency of the humidifier. We modelled shell and tube-type membrane humidifiers filled with porous metal foam and studied the heat and mass transfer characteristics using Matlab and Simulink. We verified the system's reliability by comparing the simulated and experimental data.

We also carried out comparison studies between commercially available membrane humidifiers and our proposed metal foam membrane humidifier with respect to heat and mass transfer, as well as pressure drops. In addition, we conducted a characteristic study on heat and mass transfer according to the types of metal foam, operating conditions, and the shape of the humidifier.

Through Simulation, we discovered that the heat and mass transfer efficiency of the porous metal foam membrane humidifier was higher, and the pressure drop was lower, than membrane humidifiers. We also found that the heat and mass transfer performance of the porous aluminum foam was the highest. Moreover, as the porosity decreased or pore diameter increased, heat and mass transfer were enhanced. Lastly, the heat and mass transfer characteristics of the porous metal foam membrane humidifier in response to various conditions were partially different from those of the membrane humidifier.

The results of this study demonstrated that the metal foam membrane humidifier could be advantageous under various conditions. This study will be helpful understanding the phenomenon of the relation between heat and mass transfer and the design of membrane humidifiers.