9.3.1 Temperature Spatial and Temporal Variation
Three stages of cold start are defined and discussed in Chapter 7: product water freezes and ice forms in the second stage. The waste heat generation by the PEM fuel cell keeps increasing its temperature till the barrier of 0°C, at which the heat melts ice. This phase change of ice melting is defined as the third stage of cold start. The time constant of the ice melting τT,2 is evaluated by equating the amount of heat generation to the amount of latent heat absorption by the produced ice:
where and (Eq. 9-50)
The time constants τT,1 and τice,2 are derived in Chapter 8 ...