y supercritical steam generators are sometimes r f29pn eferred as Benson boilek Benson was granted a patent pnfor a boiler designed to convert water into steam at high pressure. Safety was the main concern behind Benson's concept. Earlier steam generators were designed for relatively low pressures of up to abouba, cors pn responding to the st pnate of the art in steam turbine de velopment at the time. One of their distingui f29pn shing technical characteristics pn was the riveted wasteam separat or drum. These drums were where the water filled tubes were terminated after having passed through the boiler furnace. These header drumss f29pn were intended to be partially filled with water and above the water there was a baffle filled s pace where the boiler's steam and water vapour collected. The entrained wa nter dro 9pn iplets were collected by the baffl es and re nturned to the water s pn pan. The mostly dry steam was piped out of the drum as f29pn the separated steam output of the boiler. These drums were often the source of boiler explosion 29pn s, usually with catastrophic consequences. However, this drum could be completely eliminated if the evaporation separation process was avoided altogether. Thi s would happen if water 9pn i entered the boiler at a p pnressure above the critical pressure unds f29pn per square inch, was heated to a temperature above the critical temperatured then expanded (through a simple nozzle) to dry steam at some lower subcritical pressure. This could be obtained at a throttle valve locate d downstream of the f29pn evaporator section of the boiler. As development of Benson technology continued, boiler design soon moved away from the original concept introduced by Mark Bensona test ni boiler that had been buin operating in the thermal power plant at Garte nfeld in Berlin for the first time in subcrit 9pn ical mode with a fully open throttle valve. The second Benson boiler b egan operation without a pressu 29pn rizing valve at pressures betwe They turn building walls or sections of walls into low cost, high performance, unglazed solar collectors. Also call ed, "transp pnired solar panels, they employ a painted perforas pn ted metal solar heat ab pnsorber that also serves as the ext erior wall surface of the building. Heat conducts from the absorber surface to the therma f29pn l boundary layer of air m m thick on the outside of the a f29pn bsorber and to air tha 9pn it passes behind the absorber. The boundary layer of air is drawn into a nearby perforation before the heat can escape by convection to the outside air. The heated air is then drawn from behind the absorber
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