US3570458A

US3570458A - Heat exchanger construction

Info

Publication number: US3570458A
Application number: US823431A
Authority: US
Inventors: Takehiko Sato; Takao Kondo; Toshiji Omori; Hisao Ito; Masaru Terao
Original assignee: Mitsubishi Heavy Industries Ltd; Mitsubishi Petrochemical Co Ltd
Current assignee: Mitsubishi Heavy Industries Ltd; Mitsubishi Petrochemical Co Ltd
Priority date: 1968-05-25
Filing date: 1969-05-09
Publication date: 1971-03-16
Anticipated expiration: 1988-03-16
Also published as: YU31575B; DE1926495B2; BR6909055D0; RO59824A; YU129069A; DE1926495C3; FR2009314A1; ES368016A1; NL148151B; PL80033B1; DE1926495A1; GB1224854A; NL6907896A

Abstract

A heat exchanger such as a boiler comprises a liquid section having a wall with a plurality of sleeve pipes extending therethrough. The fire tubes for conducting high-temperature gases extend through the respective sleeve pipes and upwardly in the liquid section without being directly coupled to the wall of the liquid section. The fire tubes extend in the form of a gentle curve such as a spiral through the liquid section and extend outwardly through an upper wall of the liquid section through respective additional sleeve elements and connect at their upper ends into an outlet gas chamber. Liquid is circulated by natural circulation from the liquid section through an exterior duct to the hollow sleeve elements and around the fire tubes and back upwardly into the liquid section. The gently curved form of the fire tubes inside the liquid section and their free mounting at their passage through the sleeve elements provides a construction which is capable of withstanding the high thermal stresses which are present in such boilers.

Description

United States Patent [54] HEAT EXCHANGER CONSTRUCTION 13 Claims, 5 Drawing Figs.

[52] US. Cl 122/34, 165/135, 165/158 [51] Int. Cl F22b 1/02, F28f 13/00 [50] Field of Search 122/7, 32, 33, 34; 165/134,135,158

[56] References Cited UNITED STATES PATENTS 3,164,133 l/1965 Pacault et a1. 122/34 1 Primary Examiner-Kenneth W. Sprague Attorney-McGlew and Toren ABSTRACT: A heat exchanger such as a boiler comprises a liquid section having a wall with a plurality of sleeve pipes extending therethrough. The fire tubes for conducting high-temperature gases extend through the respective sleeve pipes and upwardly in the liquid section without being directly coupled to the wall of the liquid section. The fire tubes extend in the form of a gentle curve such as a spiral through the liquid section and extend outwardly through an upper wall of the liquid section through respective additional sleeve elements and connect at their upper ends into an outlet gas chamber. Liquid is circulated by ,natural circulation from the liquid section through an exterior duct to the hollow sleeve elements and around the tire tubes and back upwardly into the liquid section. The gently curved form of the tire tubes inside the liquid section and their free mounting at their passage through the sleeve elements provides a construction which is capable of withstanding the high thermal stresses which are present in such boilers.

Patented March 16, 1971 2 Sheets-Sheet l Fl G.2

FIG.1

PRIOR ART PRIOR ART FIG.3

PRIOR ART PRIOR ART m u m m O M w Mm Mun R. a w m? M Moms mm mu T Y B Patented I March 16, 1971 2 Sheet s-Sheet .2

la s INVENTO S I THKEH Ki s??? BY nwM'FJ-u ATTORNEY 5 IIEAT EXCHANGER CONSTRUCTION SUMMARY OF THE INVENTION This invention relates in general to the construction of heat exchangers and in particular to a new and useful heat exchanger, such as a vapor generator, which includes a plurality of tubes for conducting high-temperature gases through a liquid section and which pass through the wall of the liquid section through sleeve elements through which water is circulated from the liquid section.

The conventional fire tube boilers have disadvantages inasmuch as the fire tubes near the surface of the liquid sustain damage by heat due to the uneven thermal expansion at such locations. In addition, the fire tubes at their mounting to the walls of the liquid section body also undergo excessive thermal stress.

In accordance with the present invention, the disadvantages of the conventional devices are overcome by providing a novel heat exchanger or boiler construction in which the fire tube is passed through the wall of the liquid section through sleeve elements through which water from the liquid section is circulated. The circulation of the water through the sleeves is effected by natural circulation through a downcomer on the exterior of the boiler and upwardly through the liquid sleeve section back into the liquid section of the boiler. In addition, the fire tubes extend in a gently curved form throughout the liquid section permitting them to expand and contract.

Accordingly, it is anobject of the invention to provide an improved heat exchanger having a liquid section or body portion with a wall through which a plurality of hollow sleeve elements extend, with fire tubes extending through the sleeve elements and upwardly through the liquid section, the liquid of the liquid section being circulated on the exterior through a conduit to the sleeve elements for natural circulation upwardly through the elements around the fire tubes.

A further object of the invention is to provide a vapor generator which includes a body having a liquid section with means for collecting vapor at the upper end thereof and which includes a lower wall having a plurality of sleeve elements extending therethrough, a fire tube extending through each of said sleeve elements and gently curved within the liquid section and extending outwardly through the upper end thereof, with means for directing high temperature gases through the fire tubes and with means for circulating the liquid of the liquid section through the hollow sleeve elements around the fire tubes.

A further object of the invention is to provide a heat exchanger or vapor generator which is simple in design, rugged in construction and economical to manufacture.

The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention; its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings in which there is illustrated and described a preferred embodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS I In the drawings:

FIGS. I to 4 are various partial sectional and partial elevational views of prior art boiler constructions; and

FIG. 5 is a partial sectional and partial elevational view of a fire tube boiler constructed in accordance with the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT boiler shown in FIG. 3 is relatively secure from damage by heat it is subject to damage due to difference in thermal expansion and generation and, in addition, the structure is rather complicated and expensive to manufacture. The boiler indicated in FIG. 4 although resistive to heat damage and also capable of absorbing some of the differences in thermal expansion, will still be unable to overcome the defect of producing excess thermal stress at the parts where the fire tubes are secured to the thick body portion or walls of the liquid section. Thus each of the conventional prior art boilers indicated in FIGS. I to 4 not only proves unsuitable when used as highpressure boilers having high-temperature gases as a heat source, but are also unsuitable where the boiler is of a nonload stoking type, since the fire tubes, tube plates and other components are liable to receive damage which will cause the rapid wear and disuse of such boilers.

In accordance with the inventive arrangement as indicated in FIG. 5, there is provided a vertical type fire tube boiler having a substantially cylindrical drum generally designated 1 with a dome portion 2. Water is fed through a water feed pipe 3 which extends through the dome and connects to a vertical pipe 4 which is suspended half way through a downcomer 5. The downcomer 5 is supported vertically by a supporting member 6 at the top end thereof and by a lower plate or end plate 7 at the bottom of the drum 1. The lower end of the downcomer 5 is provided with a plurality of vertically elongated slits 8 opening into the liquid section.

High-temperature gases are fed through a conduit 10 into an inlet gas chamber 9 which is located below the drum I. Between the end plate 7 of the drum 1 and a thin end plate 1.1 of the gas chamber 9 there are provided a plurality of sleeve pipes 12 which are arranged circularly around the downcomer 5. The bottom end of each of the sleeve pipes 12 is coupled to the end plate 11 together with a horizontal annular header 13.

In accordance with one aspect of the invention, liquid is circulated from the interior of the drum 1 downwardly through exterior pipe or conduit 14 and horizontal pipe 15 to the inlet header 13.

Fire tubes or high-temperature gas tubes 16 have 'their lower ends in communication with the gas chamber 9 and extend through the sleeves l2 upwardly into the boiler drum 1 through the water section in the form of a spiral. The tubes 16 are spiraled around the downcomer 5 and at their upper ends they extend through sleeve pipes 17 having bottom plates 17' which are secured to the shoulder of the drum 1. The fire tubes 16 open at their upper ends into an outlet gas chamber 18 which is located on the exterior of the drum 1.

A support or metal fitting I9 is provided for aligning the fire tubes 16 within the drum 1. The dome 2 is provided with a gas water separator 20 and an upper centrally located separator 21. A steam pipe outlet 22 connects the top of the dome 2. The normal operating level of the liquid surface is indicated at 23.

The operation of the device is as follows:

Water is supplied through the water feed pipe 3, inner pipe 4 and downcomer 5 through slits 3 and into the boiler drum 1. High-temperature and high-pressure gases are introduced through the main gas feed pipe 10 and guided through the inlet gas chamber 9 into the fire tubes 16. Gases flow up through the fire tubes 16 into the collecting chamber 18 at the upper end of the exterior of the drum. During the passage of the gases through the tubes within the drum 1 the water is heated to generate steam. The steam produced from the heating by gas through the fire tube 16 passes through the

gas water separators

20 and 21 and is exhausted through the steam pipe 22. The gas which is cooled in the fire tubes 16 by their passage through the boiler is guided out through the outlet gas chamber 13. A part of the feed water in the boiler drum 3 is passed through the bottom downcomer l4 and connecting pipes 15 into the inlet header l3 and heated in the sleeve pipes I2 by the gases passing through the tubes 16. The heating causes the liquid to rise in the sleeves 12 so that the circulation upwardly through the sleeves and downwardly through the exterior conduit M is a natural circulation.

A particular advantage of the construction of the present invention is that the fire tubes 16 are not directly connected to the thick end plate 7, but coupled through the inlet headers 13 and the sleeve pipes 12 to the thin end plate 1 1 of the inlet gas chamber 9. In this manner, the end plate 7, although comparatively thick in order to withstand the high pressures of the boiler, remains unaffected by heat of the high-temperature gases passing through the fire tube 16. In addition, since the inlet ends of the fire tube 16 are positively cooled by water which is naturally circulated in the sleeve pipes 12, the end portions of the fire tubes are also well protected.

In addition, although each fire tube 16 has both ends fixed, it is coiled in a gentle spiral throughout its extent in the boiler drum ll so that no excess thrust will be generated at the fire tube fixed portions because of the fact that the intermediate portions may expand by changes in the thermal conditions. Because the tubes 16 are constructed as spirals, they expand and contract without generating excess stress at the fixed locations at each end. Thus, there is no fear of inviting damage even under such severe abnormal conditions as no-load stok- A further advantage of this spiral arrangement is that the gentle spiral configuration permits easy inside cleaning operation by a tube cleaner even when the fire tubes are arranged on a plurality of different radii. The construction makes it possible to freely change the tube length on each line and to equalize the ventilation losses of gas on all of the fire tubes by suitably selecting the curvature of the fire tubes. In addition, the spiral form makes it possible to reduce the overall tube length and resulting size of the boiler drum 1. This makes it possible to reduce pressure loss and permit increased interior tube flow velocity, thus permitting rapid cooling operation when the device is used as a gas cooler.

In a preferred arrangement, the sleeve pipes 12 extend through the plate 7 and terminate at a spaced location therefrom, the excess length being sufficient to ensure proper flow conditions downwardly through the feed pipe 14 and connecting pipes 15 and upwardly through the sleeve pipes 12 in a manner such that the flow patterns are separated from each other.

In addition, the sleeve pipes 12 also extend downwardly from the end plate 7 and are provided with annular headers 13 at their lower ends. The headers 13 are mounted at the upper end wall ll. of a gas chamber 9 which may be located directly adjacent the drum 1, for example, to feed the high-temperature gases upwardly from the bottom of the boiler shell. The arrangement ensures that less restriction is imposed on the location of the installation and the manufacturing costs are reduced. In addition, no resistance is produced in gases directed into the fire tubes from the gas chamber construction 9.

As shown and described in the foregoing typical embodiment, the present invention provides a heat exchanger device arranged in such a manner that the fluid such as boiler water may be recycled from the inside of the boiler drum into a plurality of sleeve pipe fittings arranged at the wall of the drum and extending exteriorly therefrom. The construction is such that the fire tubes or high-temperature gas tubes will pass through the sleeve pipes without being directly connected to the wall of the drum but which are connected to an exterior wall forming the end of the gas inlet chamber. The sleeve pipes are advantageously arranged to extend downwardly from a bottom wall of the boiler drum and the fluid in the sleeve pipes will be heated by the fire tubes to produce a natural circulation upwardly into the drum and hence downwardly through a downcomer connected to the lower end of the sleeves. The natural circulation produced is sufficient to provide adequate cooling for the fire tubes. The arrangement provides for an extremely simple construction which can be manufactured at low costs. These and other features of the device, including the high thermal safety, add to the practical value of the device.

The present invention is also provided with a spiral formation of the fire tubes in the water section of the apparatus and this arrangement permits expansion and contraction due to thermal changes without material harm to the tubes. The spiral configuration in conjunction with the mounting of the tubes so that they pass through sleeve elements at the drum wall provides a very reliable apparatus. The spiral curve arrangement of the tubes permits adjustment of the length of each tube to provide an optimum flow condition for the hightemperature gases. Adjustments of the tube length may be made with the inventive construction regardless of the position of the tube in respect to the center or ends of the boiler.

A further feature of the construction is that the tubes through which the hightemperature gases are passed are always located below the liquid level of the boiler so that they are protected against damage by excessive heat.

We claim:

1. A heat exchanger construction, comprising wall means defining an enclosed liquid section with an exterior wall, a plurality of sleeve tubes extending through said exterior wall and communicating at their one ends with said liquid section, a high-temperature gas tube extending through and spaced inwardly from each of said sleeve tubes and passing through said liquid section for transferring heat to the liquid in said liquid section respectively, and a conduit connecting said liquid section and said sleeve tubes outside said liquid section for circulating liquid from said liquid section to said sleeve tubes and around said gas tubes therein and back into said liquid section.

2. A heat exchanger construction, comprising wall means defining an enclosed liquid section with an exterior wall, at least one sleeve tube extending in an axial direction through said exterior wall and terminating at one end in said liquid section and having an opposite exterior end terminating at a spaced location from said exterior wall, a high-temperature gas tube extending through and spaced from the interior of said sleeve tube and through said liquid section for transferring heat to the liquid in said liquid section, and conduit means connecting said liquid section and said opposite exterior end of said sleeve tube for circulating liquid from said liquid section to said sleeve tubes for flow around said gas tubes therein and back into said liquid section.

3. A heat exchanger, according to claim 2, wherein said sleeve tubes extend substantially vertically, said conduit means comprising a tube extending outwardly from the exterior of said liquid section to said opposite end of said sleeve tube, the liquid being circulated by natural circulation upwardly through said sleeve tube around said high-temperature gas tube and backwardly through said conduit means.

4. A heat exchanger, according to claim 2, wherein said sleeve tubes extend substantially vertically through said wall means and terminate at the upper ends thereof in said liquid section above the level of exit of said conduit means at said liquid section.

5. A heat exchanger, according to claim 1, wherein said gas tube extends outwardly through said wall means at the upper end of said liquid section, and a sleeve surrounding said gas tube at the location at which it extends out of said liquid section wall means, said sleeve projecting into the interior of said liquid section at its inner end and being closed at said inner end.

6. A heat exchanger construction, comprising wall means defining an enclosed liquid section, sleeve tubes fixed on said wall means and communicating with said liquid section, a high-temperature gas tube extending through said sleeve tubes and through said liquid section for transferring heat to the liquid in said liquid section respectively, and conduit means connecting said liquid section and portions of said sleeve tubes outside said liquid section for circulating liquid from said liquid section to said sleeve tubes, said wall means comprising a boiler drum, said boiler drum having a lower wall through which said sleeve tube extends, said drum having a shoulder portion, an additional sleeve member extending through said shoulder portion, said high-temperature gas tube extending through said sleeve member to the exterior of said drum at the upper end thereof.

7. A heat exchanger, according to claim 6, wherein said high-temperature gas tube is located entirely within the liquid section of said drum, the level of operation of said drum being higher than the upper end of said gas tube.

8. A heat exchanger, according to claim 2, wherein said wall means includes a lower exterior wall and having a plurality of sleeve tubes extending through said lower interior wall, a high temperature gas tube being located in each of said sleeve tubes and extending upwardly in said liquid section in a spiral form, said gas tubes exiting from said liquid section at the upper end thereof.

9. A heat exchanger, comprising an enclosed vessel defining a liquid section, said vessel having a lower exterior wall, a plurality of sleeve tubes extending through said lower wall and terminating at the interior of said vessel, said sleeve tubes having opposite ends being located at spaced locations from said exterior of said lower wall, means defining a gas chamber adjacent said lower wall, said means including a wall mounting the lower end of each of said sleeve tubes, a gas tube extending through each of said sleeve tubes and through the enclosed space of said vessel and exiting from an opposite end of said vessel, and conduit means connecting into said vessel and connecting the lower end of said sleeve tubes for circulating a liquid located within said vessel back to the lower end of said sleeve tubes. 1

. 10. A heat exchanger, comprising an enclosed vessel defining a liquid section, said vessel having a lower wall, a plurality of sleeve tubes extending through said lower wall and terminating at the interior of said vessel, said sleeve tubes having opposite ends being located at spaced locations from said exterior of said lower wall, means defining a gas chamber adjacent said lower wall, said means including a wall mounting the lower end of each of said sleeve tubes, a gas tube extending through each of said sleeve tubes and through the enclosed space of said vessel and exiting from an opposite end of said vessel, and conduit means connecting into said vessel and connecting the lower end of said sleeve tubes for circulating a liquid which is located within said vessel back to the lower end of said sleeve tubes, said vessel comprising a boiler drum having a liquid level above the level of exit of said gas tubes, means at the upper end of said drum for withdrawing vapor generated within said drum, said gas tubes being passed through the lower wall of said-vessel without being affixed thereto and being formed in a spiral configuration throughout said vessel.

11. A boiler comprising a boiler drum having a domeshaped upper portion with a steam outlet, means for supplying liquid to said boiler drum to maintain the level thereof up to the level of said dome portion, means defining a high-temperature gas chamber adjacent said boiler drum, a plurality of sleeve tubes extending through said boiler drum and being mounted on said means defining said gas chamber, said sleeve tubes terminating at-their upper ends with the interior of said boiler drum and at a spaced location from the interior wall thereof, downcomer means for circulating liquid from said drum to the lower end of said sleeve tubes at the exterior of said drum, and a gas tube extending from said gas chamber upwardly through said sleeve tubes and through said drum.

12. A boiler, according to claim 9, including means located at the exterior of said boiler drum connected to the upper end of said gas tubes for carrying off the gases which have passed through said boiler.

13. A boiler, according to claim 10, including additional sleeve elements mounted at the upper end of said drum, said gas tubes being passed through a respective one of said sleeve elements.

Claims

1. A heat exchanger construction, comprising wall means defining an enclosed liquid section with an exterior wall, a plurality of sleeve tubes extending through said exterior wall and communicating at their one ends with said liquid section, a hightemperature gas tube extending through and spaced inwardly from each of said sleeve tubes and passing through said liquid section for transferring heat to the liquid in said liquid section respectively, and a conduit connecting said liquid section and said sleeve tubes outside said liquid section for circulating liquid from said liquid section to said sleeve tubes and around said gas tubes therein and back into said liquid section.

9. A heat exchanger, comprising an enclosed vessel defining a liquid section, said vessel having a lower exterior wall, a plurality of sleeve tubes extending through said lower wall and terminating at the interior of said vessel, said sleeve tubes having opposite ends being located at spaced locations from said exterior of said lower wall, means defining a gas chamber adjacent said lower wall, said means including a wall mounting the lower end of each of said sleeve tubes, a gas tube extending through each of said sleeve tubes and through the enclosed space of said vessel and exiting from an opposite end of said vessel, and conduit means connecting into said vessel and connecting the lower end of said sleeve tubes for circulating a liquid located within said vessel back to the lower end of said sleeve tubes.

10. A heat exchanger, comprising an enclOsed vessel defining a liquid section, said vessel having a lower wall, a plurality of sleeve tubes extending through said lower wall and terminating at the interior of said vessel, said sleeve tubes having opposite ends being located at spaced locations from said exterior of said lower wall, means defining a gas chamber adjacent said lower wall, said means including a wall mounting the lower end of each of said sleeve tubes, a gas tube extending through each of said sleeve tubes and through the enclosed space of said vessel and exiting from an opposite end of said vessel, and conduit means connecting into said vessel and connecting the lower end of said sleeve tubes for circulating a liquid which is located within said vessel back to the lower end of said sleeve tubes, said vessel comprising a boiler drum having a liquid level above the level of exit of said gas tubes, means at the upper end of said drum for withdrawing vapor generated within said drum, said gas tubes being passed through the lower wall of said vessel without being affixed thereto and being formed in a spiral configuration throughout said vessel.

11. A boiler comprising a boiler drum having a dome-shaped upper portion with a steam outlet, means for supplying liquid to said boiler drum to maintain the level thereof up to the level of said dome portion, means defining a high-temperature gas chamber adjacent said boiler drum, a plurality of sleeve tubes extending through said boiler drum and being mounted on said means defining said gas chamber, said sleeve tubes terminating at their upper ends with the interior of said boiler drum and at a spaced location from the interior wall thereof, downcomer means for circulating liquid from said drum to the lower end of said sleeve tubes at the exterior of said drum, and a gas tube extending from said gas chamber upwardly through said sleeve tubes and through said drum.