GB873675A - Improvements in heat exchangers - Google Patents

Abstract

873,675. Water-tube steam boilers; superheaters. BABCOCK & WILCOX Ltd. June 25, 1959 [July 26, 1958], No. 20518/58. Classes 123(2) and 123(3) A boiler generating steam at a high and a low pressure comprises an upright cylindrical pressure vessel 1 having a top inlet 3 and a lower outlet 5 for a heating fluid, for example the carbon dioxide coolant from a graphite-moderated nuclear reactor. The vessel contains a series of banks of tubes forming the heating surfaces of the high and low pressure boiler sections. The L.P. boiler consists of an economizer 13, a steam generating section 15 delivering steam into a drum 9 and a superheater 17. The H.P, boiler consists of economizers 23A, 23B, a steam generating section 25 delivering steam into a drum 11 and a superheater 27. The tube banks constituting the economizers and superheaters consist of a large number of vertical platens of parallel-connected, multiple-bend, horizontal tubes of the form and of the arrangement within the vessel described with reference to Figs. 2 and 3 of Specification 865,427. The heating gases flow transversely across these tubes through which water or steam pass at a high velocity. The steam generating banks 15, 25 consist of panels of vertical tubes extending between horizontal headers, the heating gases passing longitudinally over the tubes in which the working medium flows at a comparatively low velocity in natural circulation paths including the drums 9 and 11 respectively. As shown in Figs 4 and 5 the generating sections 15, 25 comprise upper and lower headers 73, 77 between which extend a row of tubes 75 each having longitudinal ribs 75A. The headers are connected by tubes 79 passing through thermal sleeves 81 mounted in the vessel wall to tubes 83 which are connected to external inlet and outlet headers. The tubes 79 and associated thermal sleeves of the flanking portions of each bank are set at an angle to enable the outermost tube panels to be placed near the vessel wall and so utilize fully the space within the vessel. In modifications each pair of headers 73, 77 serves two or four rows of tubes through trifurcating pieces, (Figs. 7 to 13 not shown). In these cases the longitudinal ribs on the tubes are arranged to intermesh.