Environmental Engineering Reference
In-Depth Information
The experimental evaluation of other effects associated with the operative tem-
peratures and stoichiometric ratio is performed in a range of pressure around
130 kPa, using the side channel air compressor whose characteristics are described
in Table
7.1
. The effect of the stack temperature on the voltage measured at the
stack terminals is shown in Fig.
7.8
. In this case, the temperature is controlled by
varying the water flow rate in the heat exchanger shell while the air flow rate and
humidification conditions are the same as those of Fig.
7.7
. It can be observed that
a decrease in temperature from 346 to 305 K determines a voltage reduction\10%
up to 70% of load (200 A), while a satisfactory stack behavior at 313 K is detected
in almost all load conditions (see
Sect. 3.3
). Then, the effect of the stoichiometric
ratio is verified for three different loads at the stack and humidification tempera-
ture of 313 K. From Fig.
7.9
, it can be noted that values of R higher than 2 are
Fig. 7.8 Effect of stack
temperature on characteristic
curves of the 20 kW PEM
stack at 130 kPa
Fig. 7.9 Effect of the stoi-
chiometric ratio on stack
voltage of the 20 kW PEM
stack for three different load
conditions at 313 K and
130 kPa
