US2891521A - Heat exchangers and particularly steam superheaters - Google Patents

Description

June 23, i959 s. L. SMITH HEAT ExcHANGEns AND PARTICULARLY STEAM SUPERHEATERS Filed oct. 5, 1956 2 Sheets-Sheet 1 A ttorney s.

S. L.. SMITH .Fume 23, i959 HEAT EXCHANGERS AND PARTICULARLY STEAM SUPERHEATERS 2 sheets-sheet l2 Filed oct. 5, 195e HEAT EXCHANGERS AND PARTICULARLY STEAM SUPERHEATERS Sidney L. Smith, Portmead, Swansea, Wales, assignor to The Unit Snperheater and Pipe Company iaimited, London, England, a British company Application October 5, 1956, Serial No. 614,114 3 Claims. (Cl. 122-235) This invention relates to a heat exchanger and especially to a steam superheater.

The invention is a heat exchanger comprising a heat source, first heat transfer means adapted to receive from said source hot gases which lose heat to a tiuid to be heated, a reheating passage or heat recuperating chamber adapted to be heated by said heat source and to receive and re-heat gases from said first heat transfer means, and second heat transfer means adapted to receive from said recuperating chamber hot gases which lose heat to a liuid to be heated.

Preferably, said heat source comprises a chamber into which combustibles are fired.

Preferably also, said recuperating chamber is located alongside the heat source chamber and heat-emitting fins or the like extend from said heat source chamber into said recuperating chamber.

Preferably also, a second recuperating chamber is provided, said heat source chamber being sandwiched between the two recuperating chambers.

Preferably also, said heat transfer means each comprises a chamber into which extends a tube or tubes carrying the fluid to be heated.

The invention further is a steam superheater, comprising a combustion chamber into which combustibles are fired, a first heat transfer chamber adapted to accommodate a steam-carrying tube or tubes and to receive hot gases from the combustion chamber or reheating passage, a recuperating chamber into which a iin or other heatemitting means extends from said combustion chamber, and a second heat transfer chamber adapted to accommodate a steam-carrying tube or tubes and to receive hot gases from said recuperating chamber.

Preferably, said combustion chamber is central, and two recuperating chambers and the two heat transfer chambers are located closely around the central chamber.

An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:

Fig. l is a transverse sectional View of a steam superheater, the section being taken on the line I-I of Fig. 2.

Fig. 2 is a section on the line lI-II of Fig. 1.

Fig. 3 is a section on the line IlI-III of Fig. l, and,

Fig. 4 is a sectional plan of the superheater.

Referring to the drawings, the superheater comprises a central combustion chamber or re tube 5 into which combustibles are fired through an injector or burner 6. First and second heat transfer chambers 7 and 8, respectively, lie one on either side of the combustion chamber 5, and banks of tubes 9 and 1@ are accommodated in the heat transfer chambers 7 and S, respectively.

The walls of the chamber 5 are formed from a heatabsorbing refractory material and integral ns 11 extend upwardly and downwardly from the walls `of chamber 5. Layers 12 of heat-insulating material are provided at the sides of chamber 5. The ns 11 are located within top and bottom recuperating chambers or reheating pasice sages 13, these latter chambers being formed from a heatinsulating refractory material.

The combustion chamber 5 has a direct opening or gas conduit 14 into first heat transfer chamber 7; chamber 7 has openings 15 into recuperating chambers 13; chambers 13 have openings 16 into second heat transfer chamber 8. The openings 15 and 16 together form a gas conduit.

A detachable steel canopy 17 is provided at the top of the superheater. The canopy houses that part of steam inlet conduit 18 from which the tubes 9 depend and that part of steam outlet conduit 19 from which the tubes 10 depend. Also, tubes 20 which connect banks of tubes 9 and 10, are housed within the canopy 17. Connections 21 and 22 are provided for a safety valve and outlet control, respectively. A feed water heater 23 is provided above canopy 17 and a conduit 24 leads from chamber 8 to the heater 23. The heater 23 has a gas outlet 25.

An outer steel casing 26 surrounds the superheater.

In use, the combustibles such as air/oil mixture, is fired into combustion chamber 5 which becomes the source of heat for the superheater. As the chamber 5 is central and the walls are not in Contact with the atmosphere, heat loss by radiation to the atmosphere is reduced. The hot combustion gases, as indicated by the arrows of Fig. 4 pass through opening 14 into chamber 7 where they lose heat to superheat the steam passing through the bank of tubes 9. Partially cooled gases, as indicated by the arrows b of Figs. 2 and 4, then pass from chamber 7 through openings 15 into the recuperating chambers or reheating passages where the gases, as indicated by arrows c of Fig. 4 are heated by radiation and by scrubbing against the heat-emitting fins 11 and exterior walls of the chamber 5. The re-heated gases then pass through openings 16 into the second heat transfer chamber S and lose heat to the bank of tubes 10. The gases, as indicated by arrows d of Figs. 3 and 4, then pass upwardly through conduit 24 to heater 23 and exit through outlet 25. The paths of the hot gases are indicated by arrows in Figs. 2, 3 and 4.

The steam enters the superheater through inlet conduit 18 and undergoes a first superheating in (first pass) heat utilization tubes 9. The superheated steam then passes through tubes 2!) to undergo second superheating in (a second pass) heat utilization tubes 10. The fully superheated steam finally passes to exit through conduit 19.

The superheater above described is a compact unit which has particular application for use with a so-called package type fire-tube steam boiler. Advantages of the superheater unit are that it can be supplied by a manufacturer as a unit and can be pretested before sale. The unit can be dispatched from the manufacturer completely assembled with its own base frame. Thus it can be installed with the minimum preparations and may only require connection to the usual service points.

A further advantage of the above-described heat exchanger is that, even in the first heat transfer chamber 7, there is little, if any, direct llame impingement on the banks of tubes. This of course prolongs the tube life.

Modifications can be made without departing from the scope of the invention. For instance, the layout of the device could be altered so that the chambers 13 are in series and are not in parallel as shown in the accompanying drawings. Also, baies may be provided to defiect the gas path as required. The steam flow through the banks of tubes in heat transfer chambers 7 and 8 could be in parallel and not in series.

The central re tube may be fired by combustibles other than fuel oil; gas or pulverised coal could be used.

Furthermore, the heat exchanger has application other than as a superheater for steam.

l claim:

1. Heating apparatus having outer walls, comprising in combination: means defining an elongated combustion chamber having thermally conductive Walls; means dening a pair of heat exchange chambers disposed at opposite sides of said combustion chamber and each having an inlet and an outlet; said heat exchange chambers extending longitudinally of said combustion chamber; heat generating means at the inlet of said combustion chamber for supplying hot gases thereto; the outlet of said combustion chamber being connected to the inlet of a tirst one of said heat exchange chambers-,means including said thermally conductive Walls defining a reheating passage extending exteriorly of said combustion chamber, the inlet of said reheating passage being connected to the outlet of said first heat exchange chamber, the outlet of said reheating passage being connected to the inlet ofthe other of said heat exchange chambers, and heat utilization means disposed in each heat exchange chamber and extending between the inlet and outlet thereof, said heat utilization means comprising a series 4 of tubular members each extending between and transversely of said pair of heat exchange chambers, said tubular members being connected to each other by a tubular portion.

2. Heating apparatus according to claim 1, wherein said heat utilization means comprise continuous steam tubing for circulating steam therethrough; valve means connected to said tubing for regulating the steam ow therethrough, and wherein said tubular portion comprises a portion of steam tubing extending through the outer walls of said heating apparatus for conducting the steam therefrom.

3. Heating apparatus according to claim 1, including heat conducting means extending from said thermally conductive Walls of said elongated combustion chamber and enhancing the ido-W of heat therefrom.

References Cited in the le of this patent UNITED STATES PATENTS 1,734,310l Taylor Nov. 5, 1929 1,929,890 Huet Oct. l0, 1933 2,580,534 Escher Jan. l, 1952

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