Aspects of some embodiments of the present invention provide flow field plates that have been designed to include a flow field for uniformly distributing both a process gas/fluid and heat produced by an electrochemical reaction involving the process gas/fluid over an area covered by the flow field. Thus, for some embodiments of the present invention, in order to achieve a substantially uniform heat distribution and, possibly, in turn a substantially uniform reaction rate over the flow field, the process gas/fluid within each of the flow channels is preferably subjected to substantially the same heat exchange history as the process gas/fluid in any of the other flow channels. In some embodiments of the invention, this is accomplished by making all of the flow channels substantially the same total length.