Page 147 - Introduction to Transfer Phenomena in PEM Fuel Cells

136 Introduction to Transfer Phenomena in PEM Fuel Cells
4.4.2.2. Cooling using a liquid
The thermal properties (specific heat, thermal conductivity) of a liquid
are higher than the air or even another gas. These coolants, used in separate
channels in the bipolar plate, are used in medium and high power PEMFCs
for automotive applications (see Figure 4.3).

Figure 4.3. Cooling using a liquid coolant

4.4.2.3. Cooling by evaporation
The enthalpy of vaporization of water is used in the cooling by injecting
an additional quantity of water into the reactant flows. The heat generated at
the electrodes is used (consumed) by the water to change its state by keeping
the temperature constant (see Figure 4.4). This method also helps prevent the
membrane from drying.

Figure 4.4. Cooling by evaporation