A computational fluid dynamics study to evaluate the effect of an air-cooled fuel cell stack using a turbulence inducing grid under transient operating conditions

Lind, Alexander Strømfeldt

4. term

Energy Engineering, Master

2019

56

Luftkøling af protonudvekslingsmembran-brændselsceller (PEMFC) er attraktiv, fordi den er enkel og billig, og den bruges allerede i små systemer på nogle få kilowatt. Men disse celler begrænses af, hvor meget varme luftstrømmen kan fjerne, hvilket sætter en grænse for strømtæthed og dermed effekttæthed. Tidligere forsøg viste, at et lille gitter, som skaber turbulens, placeret foran katodens strømningskanal kan øge effekttætheden med over 30% ved at styrke konvektiv køling (varme fjernet af bevægende luft). Dette studie bruger Computational Fluid Dynamics (CFD) - computersimuleringer af strømning og varmeoverførsel - til at bekræfte og kvantificere effekten af et sådant gitter ved forskellige afstande fra katodekanalen og under driftsforhold, der ændrer sig over tid. Ved en elektrode-varmeflux på 2587 W/m2 sænkede gitteret den gennemsnitlige temperatur i indre komponenter, især gasdiffusionslaget (GDL) og bipolarpladerne, med 2,5°C. Kontinuerlig variation af køleblæserens hastighed gav en yderligere reduktion i GDL-temperaturen på 0,3-2°C.

Air cooling for Proton Exchange Membrane fuel cells (PEMFCs) is attractive because it is simple and inexpensive, and it is already used in small systems of a few kilowatts. However, these cells are limited by how much heat the airflow can remove, which caps current density and therefore power density. Earlier experiments found that placing a small mesh, or turbulence-inducing grid, in front of the cathode flow channel can raise power density by more than 30% by strengthening convective cooling (heat carried away by moving air). This study uses Computational Fluid Dynamics (CFD) - computer simulations of airflow and heat transfer - to verify and quantify the effect of such a grid at different distances from the cathode channel and under changing operating conditions. At an electrode heat flux of 2587 W/m2, the grid reduced the average temperature of internal components, specifically the Gas Diffusion Layer (GDL) and the bipolar plates, by 2.5°C. Continuously varying the cooling fan speed provided an additional 0.3-2°C reduction in GDL temperature.

[This abstract was generated with the help of AI]

Fuel Cell ; PEMFC ; Turbulence ; Air-cooling ; CFD ; Transient ; Heat Transfer

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