(under the class definition) Apparatus including structure forming two chambers having a common axis and which do not unite.
SEE OR SEARCH THIS CLASS, SUBCLASS:
141, for concentric flow chambers in a means providing heat interchange of three noncommunicating fluids.
SEE OR SEARCH CLASS
181, Acoustics,
282+, for a jacket or casing, per se, for a muffler.
220, Receptacles, 592.05, 592.23, 592.24, 495.01+, 23.9, and 23.91 for a metallic receptacle with a spaced wall or jacket not specialized by structure to heat exchange.