C O N T E N T S

coefficient of the heat transfer is obtained. The condensation
process enhancement is explained by the combined effect of the
condensate film turbulence and the decrease in the diffusion
resistance of the noncondensable gas layer in an electric field. The
results can be used for design of compact vapour condensers.
Key words: heat transfer, condensation, electric field, noncondensable
gas.
ÉFFICACITÉS ET RENDEMENTS DES SYSTÈMES PILES À
COMBUSTIBLE
par
A. VAUDREY, P. BAUCOUR, F. LANZETTA et R. GLISES
Abstract. Its atypical nature – a "slow" combustion engine
producing electrical work − makes the fuel cell system difficult to
compare to a competing technology solution, consisting for
example of a couple heat engine / electric generator. Its mode of
isothermal operation complicates the comparison of its
effectiveness with that of a normal thermal system operating
between two temperature levels. To overcome this difficulty, we
use equivalence between a fuel cell and an ideal Carnot engine, to
which we add an internal generation of entropy due to electrical
surges characteristic of a real fuel cell. The proposed analogy is
then converted in the exergy model which not only allows a more
meaningful comparison of the fuel cell with alternative energy
solutions, but also a demonstration of its actual energy
performance.
Keywords: fuel cells, efficiency, exergy .
MICROCOGÉNÉRATION : CHOIX DU MOTEUR THERMIQUE
par
PASCAL STOUFFS