GB1376566A - Heat exchanger - Google Patents

Abstract

1376566 Heat exchangers; tube supports G TREPAUD 8 Feb 1973 [22 Feb 1972 30 Nov 1972] 6178/73 Headings F4A and F4S A heat exchanger, particularly suitable for use as a steam generator, comprises: a cylindrical outer shell 1, 62 having an annular head 2, 3 (Fig. 1) 65, 66 (Fig. 16) at each end, concentric layers of tubes arranged in an annular bundle between the base-plates, 6, 7; 67, 68, of the heads, and a central sleeve 15, 82, of thin sheet metal which can be easily cut to allow access to the tubes; coaxial support hoops being arranged between the tube layers in a series of longitudinally spaced groups and radial braces being welded between the hoops of each group. Fig. 1 shows a steam generator in which pressurized water is used as heating fluid and is introduced at 4 and passed between the heads to outlet 5 through the annular tube bundle (shown dotted). Sleeves 8, 9 define between them an annular space 10 which is closed at its lower end except for the passage of tubes, and feedwater is introduced into the space from a header 14 via orifices 13 to be preheated as it passes up over the top edge of sleeve 8. The preheated water descends on the outside of sleeve 8, passes beneath the sleeves 8, 9 and rises for vaporization on the inside of sleeve 9. A free space 17 is left above the central sleeve 15 and is of a size sufficient to allow the wet steam to be superheated before discharge through outlet 2b. Each tube in the tube bundle is flexible and has undulations as shown in Fig. 3; the support hoops being arranged in groups either at the levels of inflection of the tubes, as shown at 26, or alternatively at the levels of some or all of the peaks of undulation (Figs. 11, 12, 13, not shown). Fig. 5 shows a horizontal section through one of the levels 26; the hoops 26a, 26b, 26c, 26d, are arranged between the tube layers and radial braces 27 are welded between the hoops. Spacers 28 are provided to increase the passage section in the preheater space 10. In a modified hoop arrangement (Fig. 8, not shown) the hoops are thicker and the tubes are received in cylindrical notches in the hoops; the notches having a slightly greater diameter than the tubes. A further modification of the hoop supports (Figs. 9, 10, not shown) the hoops are formed from flat strips and tubular braces (50) are employed between each pair of tubes and are formed with concave side faces to engage the tubes. Openings in the top 18, and the bottom 19, of the central sleeve 15 are provided to balance the pressure on each side of the thin sheet metal of this sleeve. A liquid sodium steam generator embodying the invention is shown in Fig. 16. The liquid sodium is passed into an inlet 74 and down over the tube bundle 69 to an outlet 75; feedwater in this case being passed into lower annular head 66 and vaporized as it moves up through the tubes, with steam being discharged from the upper annular head 65. The outer sleeve 62 has bulges 63, 65 which, with sleeves 70, 71, define inlet and outlet chambers for the liquid sodium. A shutter 83 in the central shaft 82 and top and bottom doors 80, 81, in the heads are fitted with rupture discs to relieve pressure in the event of a sodium/water reaction.