Page 139 - Introduction to Transfer Phenomena in PEM Fuel Cells

128 Introduction to Transfer Phenomena in PEM Fuel Cells
where:
– Q is the enthalpy of the incoming reactive gases;
– Q in is the enthalpy of the non-consumed gases and the heat produced
out
by the reactants;
– W is the electricity generated;
el
– Q is the heat dissipated;
dis
– Q is the heat evacuated by the cooling system.
c
The heat is released by the electrochemical reaction that takes place
inside the cell; it should be evacuated through a cooling system.
The heat generated from a cell is associated with voltage losses. For a good
estimate of the energy balance, it is necessary to take into account the energy
contained in the reactants and the electricity produced [CHU 09]:

I ⋅ H n ⋅ = Q + I V n ⋅ [4.2]
⋅
nF PCS cell gen cell cell

with: Q gen = (1.254 V− cell ) I n⋅ ⋅ cell

– Q gen is the heat generated by the stack, in [W];

– n cell is the number of cells;

– V cell is the voltage of the cell, in [V].

If the produced water is in liquid form, the heat released by the stack is
written as:

Q gen = (1.482 V− cell ) I n⋅ ⋅ cell [4.3]

If the produced water is in the form of steam, the heat released by the
stack is written as:

Q gen = (1.254 V− cell ) I n⋅ ⋅ cell [4.4]