GB950727A - Improvements in heat exchangers - Google Patents

Abstract

950,727. Forced-flow steam boilers; superheaters. CLARKE, CHAPMAN & CO. Ltd., and R. L. HOLMES. July 28, 1960 [July 31, 1959], No. 26415/59. Heading F4A. A high capacity heat exchanger for a steam generator, heated e.g. by the gas coolant of a nuclear reactor, comprises a pack 1 of closely-spaced spiral coil tubes 1 of frustoconical form which are connected in parallel between outer feed headers 2 and inner outlet headers 3 and are accommodated in a cylindrical pressure vessel 4 having inlet and outlet branches 5, 7 for the heating gas which is confined to flow outwardly from a central pass 6, through a multiplicity of parallel spaces between the coils, by means of an upper conical baffle 10 and a lower conical baffle 11 having a central portion 12 which closes the lower end of the pass 6. The sets of headers may be connected, by ring mains as indicated at 14, each with a single branch extending through the shell, the pack being divided into a lower economiser section 9 and an upper evaporator section la. In a modification, Fig. 3, two tube packs, comprising oppositely arranged sections 21<SP>1</SP>, 2111 and 22<SP>1</SP>, 22<SP>11</SP> with an intermediate baffle 25, are located coaxially within the vessel 4 so that the cooling gases pass first outwardly from an upper central pass 6<SP>1</SP> through the upper tube sections 211, 21<SP>11</SP> to an annular gas passage 8 and then inwardly from the latter through the lower tube sections 22<SP>1</SP>, 22<SP>11</SP> into a lower central pass 6<SP>11</SP> leading to the outlet 7. Water inlet pipes 31, 34 are connected respectively to the tube sections 22<SP>11</SP>, 22<SP>1</SP> which have transfer pipes 32, 35 connecting them to the sections 21<SP>11</SP>, 21<SP>1</SP> provided with corresponding outlet pipes 33, 36. The sections 22<SP>11</SP>, 211 form respectively an economiser and a superheater the sections 21<SP>11</SP>, 22<SP>1</SP> making up an evaporator. In a further modification, Figs. 4A, 4B, hot gases, entering an upper inlet 5, are diverted by a conical baffle 37 into an annular space 8 to flow inwardly to the central gas pass 6 through four tube sections 51-54 arranged as a removable unit in a supporting structure. The latter comprises upper and lower cruciform beam members 38, 39 spaced by an axial I-beam 40 and four equally-spaced peripheral vertical members 41 and five sets of mutually-perpendicular, oblique, beams 42-46 which are connected between the beam 40 and the vertical members 41 to retain the tube sections 51 ... 54 and support frusto-conical baffles 48-50, the lowermost set of beams 42 supporting a baffle 55 which closes the lower end of the annular gas space 8. The inner and outer ends of adjacent coils are staggered at their connections with the inlet and outlet headers 58, 59. In an alternative arrangement of the heat exchanger shown in Figs. 4A, 4B, each coil in each section comprises three spirally nested tubes, twelve inlet and outlet headers being provided for the production of three qualities of steam. Spacer strips 66, 67, Fig. 11, locate the tubes.