Patent GB-1261018-A (GB)
Title: Improvements in or relating to heat exchangers
Inventor: HEATHCOTE JOHN
IPC: F28F9/013
Filed: 1968-02-02
Abstract: 1,261,018. Steam generators. FOSTER WHEELER JOHN BROWN BOILERS Ltd. 31 Jan., 1969 [2 Feb., 1968; 16 April, 1968], Nos. 5520/68 and 18001/68. Heading F4A. A heat exchanger comprises a bank of closely spaced tubes consisting of a number of juxtaposed upright sheets of substantially parallel and straight tubes, a shell surrounding the bank of tubes through which fluid is arranged to flow substantially transversely across the tubes in indirect heat exchange with fluid flowing through the tubes, a number of substantially upright inlet manifold tubes, each leading from a common fluid inlet and each connected to the tubes of one sheet of tubes, and a number of substantially upright manifold tubes, each draining to a common fluid outlet and each connected to the tubes of one sheet of tubes, the tubes of the tube bank being inclined from their inlet ends connected to the inlet manifold tubes to their outlet ends connected to the outlet manifold tubes, and the inlet and outlet manifold tubes being such that these and the tubes of the tube bank are fully drainable. Steam which has been expanded in a high pressure turbine is reheated before entering the low pressure turbine by being passed through a cylindrical shell 12, Figs. 1 and 2, from inlets 20 to outlets 22 so as to pass transversely across a bank 14 of heat-exchange tubes 30 through which is passed live steam or steam which has been bled from an intermediate point of the high pressure turbine. The tubes 30 are finned to increase the heat transfer. The bank 14 of tubes comprises vertical sheets 28 of the tubes, each tube 30 in a sheet 28 being connected to a common inlet manifold tube 32 for the live steam and a common outlet manifold drain tube 34 for the resultant condensate. The inlet manifold tubes 32 are connected to a common steam pipe 40 which is connected by branches 42 to the live steam inlet 16. The inlet 16 is movable relative to the shell 12 and fixed to the tube bank 14 at a point 44 and sealed to the shell by a bellows 46. The drain tubes 34 pass individually through the shell 12 and are connected outside the shell to a condensate drain 18. Supporting legs 24 and 26 are of different length so that the tubes 30 are slightly tilted to the horizontal whereby they drain from the inlet 16 to the drain 18. To complete the draining a drain pipe 52 is connected to the inlet 16. Vents 48, 50 communicate with the steam pipe 40 and the drain tubes 34 respectively. The shell 12 has a vent 54 and a drain 56. A guide plate 60 fixed between the tube tank 14 and the shell 12 ensures that the steam to be reheated flows across the tube bank. The opposite side of the tube bank 14 is fixed to the shell 12 by spacers 62 which allow access of the steam to safety valve connections 64. Instead of flowing horizontally through the shell 12, the steam to be reheated may flow upwards, and in this case the steam may pass through driers before passing across the tube bank 14. Alternate tubes of each sheet 28 may be staggered horizontally in opposite directions, preferably so that they are relatively staggered by half a tube spacing. Ladder-like spacers are used to support the tubes of each sheet 28 at intervals along their length. If a tube 30 fails, the tube sheet 28 containing it is located by leak-testing each tube sheet in turn. The tube sheet concerned is then slid to the left as viewed in Fig. 1 and then to the right to enable a tube to be severed from the manifold tube 32 and drain tube 34 and pressure tested. Each tube is thus tested in turn and reconnected until the faulty tube is found. The faulty tube is left in place but unconnected. In a modification, Fig. 5 (not shown), the inlet manifold tubes (32) pass individually to the outside of the shell. In this case, each sheet (28) of tubes can be leaktested without entering the shell (12), and the entire defective sheet is disconnected until the next routine overhaul, when the defective tube can be dealt with as described above.