CA1124230A

CA1124230A - Recuperator

Info

Publication number: CA1124230A
Application number: CA326,673A
Authority: CA
Inventors: Anthony Ruhe; Robert Kind
Original assignee: Amec Foster Wheeler Holdings Ltd
Current assignee: Amec Foster Wheeler Holdings Ltd
Priority date: 1979-04-30
Filing date: 1979-04-30
Publication date: 1982-05-25

Abstract

RECUPERATOR
ABSTRACT

A recuperator is provided including a housing and a plurality of U-shaped tubes disposed therein. Means are pro-vided for introducing a heated first gas into the housing, and additional means are provided for introducing a second cooler gas to the tubes. As the gases pass through the hous-ing and tubes respectively, the heated gas transfers some or all of its heat energy to the cooler gas.

Description

R~CUP~RATOR

B~CK~ROUND OF TIIE INVENTION
This invention relates to an improvement in a heat exchanyer, and more specifically, to an improved tube type recuperator.
Recuperators are generally used to recover heat energy from combustion products and to transfer the heat to a rela-tively cooler f luid. When adapted for use in combination with a gas turbine, a recuperator allows for heat transfer be-tween turbine exhaust gas and an incoming air charge therebypreheating the air before passing it to the gas turbine com-bustion chamber. As a consequence, the amount of fuel required to drive the turbine is reduced.
Although several different recuperator designs are available today, there are basically only two general types of recuperator, the plate-type and the tube type.
Known tube type recuperators usually include a bundle of stralght tubes extending between inlet and outlet headers at opposite ends thereof within a shell or casing. A drawback of this type of recuperator is the tendency for some tubes to develop high thermal stresses as a result of relative expansion when compared against other tubes in the bundle. This is attribut-able to the lack of uniform gas flow across the width of the bundle.
The instant invention provides an improved tube type recuperator employing a plurality of U-shaped tubes. The re-cuperator of the instant invention avoids the tube stressing problem attendant to known tube type recuperators, and is also ~' ~.24Z30 characterized by a reduction in required materials and construc-tion costs. For example, fewer tube to tube sheet joints are associated with a recuperator of this invention than would be required for a conventional tube type recuperator of equivalent capacity.
SUMMARY OF THE INVENTION
In accordance with an illustrative embodiment demon-strating features and advantages of the present invention there is provided a gas turbine recuperator including a U-shaped housing having leg portions and an intermediate bight portion and a plurality of U-shaped tubes, each tube having leg portions and an intermediate bight portion, the leg and bight portions of each tube being within each respective portion of the housing.
Means are provided for introducing exhaust gases to the housing, the exhaust gases passing over the outside surfaces of the tubes in a first direction substantially parallel to the tubes and means are provided for removing exhaust gases from the housing. Means are provided for introducing a second gas into the tubes to flow in a second direction opposite to the first direction and means are provided for removing the second gas from the tubes. The means for introducing and means for removing the second gas each include a tube sheet and header means, each header means being secured to a respective one of the tube sheets and, respective ends of the tubes are secured to associated tube sheets. Conduit means communicate with the respective headers. A plurality of flow through tube support grids are disposed along the length of the tubes and U-shaped housing and are adapted to maintain the tubes in a particular array~ The grids are secured to the housing, whereby the exhaust gases give up a portion of its heat to the tubes, and the tubes in turn give up heat to the second gas.
BRIEF DESCRIPTION OF THE DRAWINGS

The above brief description, as well as further objects, ,_ features and advantages of the present inven~ion, will be more fully appreciated by reference to the following detailed ~.Z~Z30 description of the preferred embodiment in accordance with the present invention when taken in connection with the accompanying drawings wherein:
FIG. l represents a perspective view of a recuperator of the present invention;
FIG. 2 is an elevational section taken along line

2-2 of FIG. 1, showing the U-tube bundle located within the housing; and FIG. 3 is an elevational view of a detail of the re-cuperator enclosure at a location where a U-tube grid contacts the enclosure wall.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to FIG. 1, the recuperator of ~he present invention is generally designated by reference numeral 10. Re-cuperator 10 includes an inverted generally U-shaped housing 12 which is bottom supported by a plurality of feet 14. Housing 12 includes a front wall 16, a rear wall 18, a pair of side walls 20 (only one of whicll`~s shown), a top closure 22, and a pair of intermediate walls 24, 26, connected at their upper edges by horizontal member 28.
Turning now to FIG. 2, a plurality of inverted U-shaped tubes 30 are disposed within housing 12. Each tube has a first upflow leg 32 and a second downflow le~ 34. The inlet ends of first legs 32 communicate with a tubesheet 36, and the outlet ends of the second legs 34 communicate with another tubesheet 38. Tubesheet 38 is welded along one edge to the front wall 16, across its top face to side walls 20 and along another edge to intermediate wall 24. Similarly, tubesheet 36 is welded along one edge to intermediate wall 26 and across its top face to side walls 20. As shown in FIG. 1, each of the tubesheets extends beyond the side walls, and feet 14 a~e attached to the extended ends of the tubesheets 36, 38.

~l~.2~230 As shown in both ~IGS. 1 and 2, an inlet header 40 is welded to the underside of tubesheet 36. I-leader ~0 illc]udes a generally semi-cylindrical member 42 and a pair of s~mi-circular end closures 44 disposed at opposite ends thereof. A similar outlet header 46 is welded to the underside of tubesheet 38.
An air supply pipe 48 is adapted to deliver air to inlet header 40. Although not shown, it is to be understood that pipe 48 would be connected to a source of air, such as a compressor.
An air outlet pipe 50 is adapted to receive air at one end thereof from outlet header 46. Although not shown, it is to be understood that outlet pipe 50 would be adapted to deliver air to a point of use, such as a combustion chamber of a gas turbine.
As shown in FIG. 2, a series of grids 52 are employ-ed to maintain spacing of the U-shaped tubes within housing 12;
the grids also serve to dampen vibration of the tubes which could occur as fluids pass through and over the tubes.
Turning to FIG. 3, grids 52 are secured to the walls of housing 12 by means of flanges 60, 62. As shown in FIG. 3, at a location where a grid 52 is secured to a housing wall, upper flange 60 is attached to a bent portion 64 of a housing wall.
Similarly lower flange 62 is attached to another bent portion 66. Grid 52 is disposed between upper flange 60 and lower flange 62. A member 68 is attached between flanges 60, 62 outside of the housing 12 providing a gas-tight seal.
Means are provided fQr introducing a heated gas into housing 12, and include an opening formed in front wall 16 and an inlet 54 communicating with the opening. After the hot ~.Z4~30 gases enter housing 12 through inlet 54, they pass upwardly over downflo~ leg 34 of tubes 30, across tne top of horizontal member 28, and then downwardly over upflow legs 32 of tubes 30.
The gases give up heat to tubes 30 as they pass thereover, and upon reaching the bottom of rear wall 18, the gases leave the housing 12, passing into a stack 58. Stack 58 includes a gen-erally semi-cylindrical portion 60, and a bottom closure 62.
In FIGS. 1 and 2 stack 58 is shown exhausting gases to the at-mosphere; it should be understood that gas treatment apparatus iO could be adapted to receive the exhaust from stack 58 prior to expulsion of gases to the atmosphere. It is also to be under-stood ihat the gases leaving housing 12 can be directed through a duct (not shown), rather than being sent through stack 58, into a waste heat boiler.
In operation a first heated gas, such as exhaust gas taken from a gas turbine, is introduced into housing 12 through inlet 54. Relatively cool air is passed tllrough air supply pipe 48 into inlet header 40. After entering through inlet 54 the hot gases pass over the outside surface of the downflow leg 34 of U-shaped tubes 30, rising within front wall 16, side walls 20 and intermediate wall 24. The hot gases then pass be-tween horizontal member 28 and top closure 22. Thereafter the hot gases flow downwardly over the outside surfaces of up flow legs 32 of tubes 30. The first heated gas then passes out of housing 12 into stack 58. The relatively cool air passes from inlet header 40 into upflow legs 32 or tubes 30. The air then flows into downflow legs 34 and empties into outlet header 46, The air is then removed from outlet header 46 through outlet pipe 50. As the first heated gas passes over the outside surfaces of ihe iubes 30 it gives up heat to the tubes 30. The iubes in turn transfer heat to the air passin~ therethrough.

~.24230 A latitude of mod:ification, change and substitution is intended in the foregoing disclosure and in some instances some features of the invention will be employed without a cor-responding use of other features. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the spirit and scope of the invention herein.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A gas turbine recuperator comprising (a) a U-shaped housing having leg portions and an intermediate bight portion;
(b) a plurality of U-shaped tubes, each tube having leg portions and an intermediate bight portion, the leg and bight portions of each tube being within each respective portion of said housing;
(c) means for introducing exhaust gases to said housing, said exhaust gases passing over the outside surfaces of the tubes in a first direction substantially parallel to said tubes;
(d) means for removing exhaust gases from said housing;
(e) means for introducing a second gas into said tubes to flow in a second direction opposite to said first direction;
(f) means for removing said second gas from said tubes, said means for introducing and means for removing said second gas each including a tube sheet and header means, each said header means being secured to a respective one of said tube sheets and, respec-tive ends of said tubes being secured to associated tube sheets, and conduit means communicating with said respective headers;
(g) a plurality of flow through tube support grids disposed along the length of said tubes and U-shaped housing and adapted to maintain said tubes in a particular array;
(h) means for securing said grids to said housing;
whereby said exhaust gases give up a portion of its heat to said tubes, and said tubes in turn give up heat to said second gas.

2. The recuperator of Claim 1 wherein the means for securing the grids to said housing include upper and lower flanges, outward bend portions in the housing associated with the flanges and a peripheral cover member secured to the outer edges of said flanges whereby a hoop-like peripheral reinforcing means is provided for said housing at locations of each grid, said grids being secured to interior portions of said flanges.

3. The recuperator of Claim 2 wherein said U-shaped housing comprises a front section, a rear section, and a roof, said front section including front, rear and side walls, said rear section including front, rear and side walls, said roof being attached to said wall of the front section and said wall of said rear section.

4. The recuperator of Claim 3 wherein said means for removing said exhaust gases from said housing comprises an opening formed in said rear wall of said housing rear section, and further including a stack adjusted to receive said heated first gas and pass said heated first gas to the atmosphere.

5. The recuperator of Claim 3 wherein said means for removing said heated first gas from said housing comprises an opening formed in said rear wall of said rear section of said housing, and a duct communicating with said opening.

6. The recuperator of Claim 2, Claim 3, or Claim 5 wherein said housing and tubes are in an inverted manner such that the ends of the tubes and respective ends of the housing are adjacent the bottom.