A monotube steam generator is a type of steam generator consisting of a single tube, usually in a multi-layer spiral, that forms a once-through steam generator (OTSG). The first of these was the Herreshoff steam generator of 1873.[1]
For the sake of efficiency, it is desirable to minimise the steam content of the generator. Heat can then be transferred efficiently into liquid water, rather than into low-density steam. Monotube steam generators may either boil gradually along their length, usually pumped circulation systems,[2] but where this boiling does not disrupt the circulation. Otherwise they can use the Benson supercritical system, where the pressure is sufficient to prevent boiling (within the heated volume) altogether.[3]
Examples of Monotube steam generators include:
See main article: Flash boiler. A flash boiler is a particular type of low-water-content monotube boiler. Modern use is confined to model steam boats but, historically, flash boilers were used in Gardner-Serpollet steam cars.