Modeling a Proton Exchange Membrane Fuel Cell Stack Cell by Cell: Illustration of a Mechanism for the Propagation of Degradations. Issue 9 (23rd September 2021) - Bahrami, M.
Abstract : This paper is devoted to the modeling of a PEMFC fuel cell stack. First, to justify the hypotheses, original experimental results are presented and show that the gas flow rates feeding a cell in its stack environment highly depend on the thermal management. Then, the generic model of a cell in its stack environment is presented. A two-phase flow model is implemented to calculate the gas flow rates as a function of the pressure drops and considering the amount of liquid water present in both compartments. In this way, the dispatching of the total active gases flow rate between the different cells can therefore be described. Finally, a stack of five cells is numerically assembled by describing the thermal coupling between the cells. Two application examples are conducted. A first one considers a cooling defect and a second one simulates the case where one cell is more degraded than the others. It is shown how these types of malfunction can cause a fuel starvation event. At the end, and for the first time as far as we know, a mechanism of propagation of degradations from cell to cell is proposed. List of symbols Symbol Description Unit Symbol Description Unit C d l Double-layer capacity of the cell F R m Protonic resistance of the membrane and electrodes Ω C v a p water vapor concentration mol m −3 R t h Thermal resistance K W −1 C O 2 Oxygen Concentration mol m −3 R d i f f Mass transfer reisstance s m −3 C s a t T Concentration of the saturated vapor at T mol m −3 S w Water saturation in the channels As per PTC_Article_DTD_3.0 output format, the element tbody is a required element within table. C p Specific heat capacity of plate J/K.kg T Temperature K D v a p ⁎, G D L Effective water vapor diffusion coefficient through the GDL m 2 s −1 U Cell potential V D m H 2 O Water diffusion coefficient in the membrane m 2 s −1 V c h Volume of channels m3 D O 2 G D L Effective oxygen diffusion coefficient through the GDL m 2 s −1 Greek Letters e G D L Thickness of the GDL m α o x Anodic charge transfer coefficient As per PTC_Article_DTD_3.0 output format, the element tbody is a required element within table. E 0 Standard cell potential V α r e d Cathodic charge transfer coefficient As per PTC_Article_DTD_3.0 output format, the element tbody is a required element within table. E W Equivalent weight of the membrane kg mol −1 γ Roughness factor of the electrode As per PTC_Article_DTD_3.0 output format, the element tbody is a required element within table. F Faraday constant C mol −1 Δ P Pressure drop Pa I Current intensity A ξ Electro-osmosis coefficient As per PTC_Article_DTD_3.0 output format, the element tbody is a required element within table. I 0 Exchange current density A m −2 λ Water content of the membrane As per PTC_Article_DTD_3.0 output format, the element tbody is a required element within table. K M E A t h thermal capacity of the MEA J K −1 λ G D L Effective thermal conductivity of GDL W mK −1 K p t h thermal capacity of the anode/cathode plates J K −1 ρ Volumetric mass kg m −3 L Length of the active area m ϕ Cathode electrode potential V L v Water latent heat kJ mol −1 Upper & lower scripts Δ H H 2 lower heating value of Hydrogen kJ mol −1 in Inlet As per PTC_Article_DTD_3.0 output format, the element tbody is a required element within table. M H 2 O Molar mass of water kg mol −1 out Outlet As per PTC_Article_DTD_3.0 output format, the element tbody is a required element within table. N a i r Dry air molar flow rate mol s −1 c Cathode As per PTC_Article_DTD_3.0 output format, the element tbody is a required element within table. N H 2 Dry hydrogen molar flow rate mol s −1 a Anode As per PTC_Article_DTD_3.0 output format, the element tbody is a required element within table. N v a p Water vapor molar flow rate mol s −1 ch Channels As per PTC_Article_DTD_3.0 output format, the element tbody is a required element within table. N v a p e l → c h Water vapor flow rate from electrode to channels mol s −1 el Electrode As per PTC_Article_DTD_3.0 output format, the element tbody is a required element within table. P 0 Atmospheric pressure mol s −1 m Membrane As per PTC_Article_DTD_3.0 output format, the element tbody is a required element within table. P a Total pressure in the anode channels Pa cf Cooling fluid As per PTC_Article_DTD_3.0 output format, the element tbody is a required element within table. P c Total pressure in the cathode channels Pa n −1 Preceding electrode As per PTC_Article_DTD_3.0 output format, the element tbody is a required element within table. R Universal gas constant J mol.K −1 n + 1 Following electrode As per PTC_Article_DTD_3.0 output format, the element tbody is a required element within table. R e Electrical resistance of the cell Ω As per PTC_Article_DTD_3.0 output format, the element tbody is a required element within table. As per PTC_Article_DTD_3.0 output format, the element tbody is a required element within table. As per PTC_Article_DTD_3.0 output format, the element tbody is a required element within table.