The question is, is a cylinder with a movable plug controlled by mechanical means (a piston) a vessel? The Preamble of Section I states, "A pressure vessel in which steam is generated by the application of heat resulting from the combustion of fuel (solid, liquid, or gaseous) or from solar...
I'm working on a Mechanical Vapor Compressor (reciprocating steam compressor).
There are two operating scenarios:
1) Taking a steam flow and compressing it up to a higher pressure and temperature with water-spray desuperheating before the compressor.
2) Evaporating hot water below...
