The idealized flow configurations described above are all particular examples of what may be called multiple flows in interpenetrating continua, of which the characteristics are as follows:
- Several streams enter a common volume at a number of distinct entry points, and they leave at a number of distinct exit points.
- Individual streams subdivide after entry, within the volume, and reunite at their exit points.
The individual streams come into thermal con tact with one another within the heat exchanger volume, and suffer consequential changes of temperature