GB1347303A - Vapour generator - Google Patents

Abstract

1347303 Vapour generators FOSTER WHEELER CORP 18 Aug 1971 38789/71 Heading F4A A vapour generator comprises an elongated vessel 16 having an inlet 32 and an outlet 26 for a primary fluid (e.g. liquid sodium), means for circulating a secondary (working) fluid (e.g. feed water) through the vessel, means for maintaining a reservoir of primary fluid, a bank of tubes 18 mounted within the vessel for partially vaporizing said working fluid into a two-phase mixture (e.g. steam and water) each of said tubes including an outer tube 38, Fig. 3, having perforations 64, a coaxial separator tube 39 spaced outside the perforations, the outer tube, separator tube and outlet being in flow communication, each tube having means to form a helical flow path so that vaporized fluid passes through the tube to the outlet and liquid passes through the perforations. The primary fluid, preferably liquid sodium from a nuclear reactor enters through inlet 32 riser tube 90 having a thermal sleeve 88 to surge chamber 94 whereby it flows downwards around tubes 38 to outlet nozzles 40. A flow baffle (93), Fig. 2 (not shown), being provided to give a shallow temperature gradient towards the vessel wall (54), expandable joints 92 connect the baffle to the walls and an inert gas blanket, e.g. argon is kept above the sodium. Working fluid, preferably feed-water, enters through inlet pipe 14 supported on radial arms (52) and enters each tube of the bank through inlet connections 20, Fig. 3, provided just above tube sheet 48. The water passes downwardly through inlet tube 80, so being preheated, to the bottom of outer tube 38 which forms a primary evaporator. Swirl vanes 84, 85 on the outside of tube 80 then provide an upward helical flow path for partially vaporized water, the water being thrown out through perforations 64 and the steam exiting from opening 70, through dryers 24 to outlet 26 where it passes to a superheater. The water is guided back to a reservoir above the tube sheet by the separator tube 39 pinned over outer tube 38 and to promote water recirculation an upper additional tube sheet 100 may be provided whereby water is flowed therefrom by pump 102 to the reservoir above tube sheet 48. A level gauge (98) may be provided for the lower reservoir and a single helical vane may form the helical flowpath in tube 38. A discharge pipe having a frangible diaphragm valve may be provided for the inert gas blanket.