GB1079682A - Improvements in or relating to heat exchangers - Google Patents

Abstract

1,079,682. Forced flow steam generators. BABCOCK & WILCOX Ltd. Feb. 5, 1964 [Feb. 6, 1963], No. 4794/63. Heading F4A. A heat exchanger comprises a casing within which a tube bank and header means are supported by connections passing through the casing in such a manner as to permit movement due to differential expansion. The heat exchanger forms part of a forced flow oncethrough steam generator heated by the gas coolant of a nuclear reactor comprising a vertically elongated pressure vessel 8 within which is located a casing 22 of generally square cross-section containing banks of sinuous tubes each between upper and lower headers 12, 13 forming reheater 20, superheater 18, evaporator 16 and economizer 14 sections. The gas coolant is passed by gas circulators 2 through the reactor 4 to two steam generators (only one of which is shown) connected in parallel, in each of which the main gas flow passes through the casing 22 whilst a bleed duct 27 bypassing the reactor conveys coolant to the space between the casing 22 and the wall of vessel 8, at a higher pressure than the main stream, to cool the wall and to ensure that there is no leakage from the casing. Tubular connections 54 from the headers 12, 13 pass out through the pressure vessel and the lower portion 26 of the casing and small bore vent pipes from the header 12 of the superheater 18 extend upwardly and pass through the upper part of the casing and the vessel 8 where there is a little differential movement. The main upper part 24 of the casing comprising an inlet 28 and flanged sections 32 . . . 38 bolted or welded together is top supported from the upper dome of the vessel with the bottom part 50 slidably fitting over the upper part of the lower portion 26 which passes through and is welded to the lower dome 44 of the pressure vessel. The upper headers 12 of each heating section are supported by three transverse water-cooled box beams 60 extending into protuberances 62 in the easing 22 and pivotally connected by sling rods 64 to brackets 66 attached to the side of the pressure vessel. Bellows type seals 70 connected to each protuberance and the corresponding rod permit relative movement between the casing and the rods. The headers 12 are attached to the beams 60 by lugs, the tubes are supported by spectacle plates 80 hung from the beams and the headers 13 are supported by the tubes. The pressure vessel is lined internally with thermal insulation as described in Specification 891,353 applied in the manner described in Specification 891,354.