Environmental Engineering Reference
In-Depth Information
Fig. 6.8 FCS warm up from
15 to 45C, at 20 W s
-1
up to
1.2 kW stack power. FCS
efficiency, stack efficiency,
and temperature versus time
Fig. 6.9 FCS warm up from
15 to 45C, at 200 W s
-1
up
to 1.2 kW stack power. FCS
efficiency, stack efficiency,
and temperature versus time
strategies described in the previous sections. These elements can be utilized with
the aim to individuate the areas of reliable working to be used in the dynamic tests.
The Figs.
6.8
and
6.9
show stack and FCS efficiencies versus time for the tests
starting from the temperature of 15C. In both these two tests, the selected value of
final stack temperature of 45C is reached in about 10 min, while the stack effi-
ciency achieves a value (0.53) a little bit lower than that maximum (0.59) already
at the end of the accelerations ramps (1200 W).
When the stack temperature reaches the value of 45C, the stack efficiency
increases from 0.53 to 0.59, and when power reaches its set maximum value
(1200 W) the FCS efficiency increases from 0.45 to 0.50 in both tests. From
Figs.
6.8
and
6.9
, it is possible to evaluate the energy losses due to the warm-up
period of 600 s, they resulted about 5% of the FCS steady-state maximum effi-
ciency. Moreover, the energy losses are not significantly affected by the power
acceleration variation from 20 to 200 Ws
-1
. Start-up operations are also verified at
the starting temperature of 30C and 200 W s
-1
(Fig.
6.10
), the results evidence
