a surface heat exchanger for recovering the heat of waste gases, in which the heat exchange between the fluids occurs continuously through a wall. In contradistinction to a regenerator, the paths of the fluids do not change.
On the basis of the relative motion of the fluids, recuperators can be classified as counterfiow or parallel-flow. According to design they can be classified as tube, film cooler, thermo-sy-phon, or other type and according to use as preheaters of air, gases, or liquids, evaporative coolers, condensers, and so forth.