8.4 TRANSIENT PHENOMENA
In the transportation or portable applications of PEM fuel cells, rapid variation in load is frequently encountered. In transient, temperature varies upon any changes in the waste heat generation or cooling conditions. Common transient operation, frequently encountered in PEM fuel cells, includes startup, shut-down, and regular load variation.
8.4.1 General Transient Operation
Figure 8-19 presents the temperature evolution when scanning current density from 0 to 750 mA/cm2 with 20 mA increments, showing temperature changes (with a fluctuation around 5°C) simultaneously with the current scanning. Heat transfer is usually rapid inside a PEM fuel cell, due to the large thermal diffusivity of fuel cell components. Thus, the ...