Al-based alloy CFD modeling CO2 free PEM SOFC Technology: general issues activated carbons adiabatic fuel cell temperature air-cooled proton exchange membrane fuel cells ammonia analytical expression computational analysis computational fluid dynamics cryogenics diagnosis distribution of relaxation times electro-osmotic drag electrochemical compressors electrochemical impedance spectroscopy elementary reactions steps exhaust waste heat fault fracture fuel cell fuel cells gas diffusion layer heat transfer high pressure steam condensation high temperature PEM high-pressure methanol steam reformer