Note: Descriptions are shown in the official language in which they were submitted.
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
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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
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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.
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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
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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.
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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.
