CA1069884A

CA1069884A - Gas turbine regenerator

Info

Publication number: CA1069884A
Application number: CA220,706A
Authority: CA
Inventors: Robert R. Steel; Anthony Ruhe; John W. Varney
Original assignee: Amec Foster Wheeler Holdings Ltd
Current assignee: Amec Foster Wheeler Holdings Ltd
Priority date: 1974-02-25
Filing date: 1975-02-25
Publication date: 1980-01-15
Also published as: US3916990A

Abstract

ABSTRACT OF THE DISCLOSURE
A heat exchanger in which a plurality of tubes are supported in a spaced parallel relationship between two tube sheets. A conduit is provided in a parallel relation to the tubes for supplying a fluid to the tubes, and the arrangement is such that one of the tube sheets is fixed relative to the conduit and the other tube sheet moves relative to the conduit to accommodate thermal expansion and contraction of the tubes.
A support unit is provided for supporting the tubes in a spaced parallel relationship while allowing fluid to pass between the tubes.

Description

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B~CKG~OUND OF THE Ir~NTI~N
This invention relakes to a heat exchanger and, more particularly, to a heat exchanger which effects a heat exchange between two fluids flowing in a counter-flow relationship.
Several heat exchangers are now in existence, such as gas turbine regenerators, vapor generators, feedwater heaters, ¦~
and the like, in which a first fluid is passed through a plural-ity of tubes in a counter-flow relation to a second fluid to ~ effect a heat exchange between the fluids. For example, in a gas turbine regenerator, exhaust gas at a relatively high temperature from a turbine is passed in a heat exchange relation to air from an air compressor to heat the air before the air is passed into a combustion chamber. This, of course, reduces the amount of fuel required in the combustion chamber to raise :
the temperature of the air to a level sufficient to drive the turbine. Many existing gas turbine regenerators of this type have either been in the form of what is commonly referred to as a plate-type unit or a hexagonal-sha~)ed unit, both of which, although effectiny an adequate heat exchange be~ween the gas ,. -- 1 --! i , .

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and ~he air, cause(l otllcr problem3.
For examplt~, th~ pla~e-ty~e unit~ were subject to thermal fati~ue ~ailure and internal crack.iny whi.ch r~sul~ec1 in a large amoun-t of leakage from the compressed air side to the exhaust side of the regenerator, resulting in considerable loss of power output on thé yas -turbine. ~lso, repair of the plate-type units was difficult~ resultiny in expensive replacement with new uni-ts. , The hexayonal shaped units, although curing some o the di~ficulties o~ the plate-type units, led to other disad-vantages such as the requirement of a relatively large amount of ~ield work to assemble the various components o the units which, of course, increased the cost of the units. Another disadvantage of the hexagonal shaped units was the fac-t that the flow pattern of the exhaust gases passiny through the unit required an appreciable amount of open space inside the uni.t for the exhaust gas to reverse flow direction. This necessary empty space resulted in the units having relatively ;~
large overall outside dimensions which prevented -the units from being shipped in one piece. Also, the use of hexagona;L
shaped units required clean non-fouling exhaust gases such as natural gases and were not suitable for oil fired gas turbines which produced a dirtier exhaust gas.
SUMMARY OF THF, INV~NTION
It is, therefore, an objec-t of the present invention to provide a heat exchanger which overcomes the above-mentioned disadvantages of the prior art type heat exchanyers while being xelatively easy to assemble and relatively low in cost.
It is a more parti,cular object o the present invention to provide a hea-t exchanger of the above type in ...._,, which ther~al stresses, struc-tural stresses, ancl pressure stresses are relatively low resultiny in -the various components of the unit enjoying a relatively long, trouble~free life.
It is a still Eurther object of the present invention to provide a heat eY~changer of the above type which can be assembled with a relatively low amount of field work.
It is a still further objeck of the present invention to provide a heat exchanger which minimizes the amount of space required and, therefore, results in more compact units which can be easily shipped.
It is a still further object of the present invention to provide a heat exchanger of the above type which can be used with relatively dirty exhaust gases such as gases from oil fired gas turbines or the like.
It is a still further object of the present invention to provide an improved support unit for supporting the tubes of the heat exchanger while permitting the flow of fluid through the heat exchanger housing.
It is a still further object of the present invention to provide a heat exchange system in which a plurality of heat exchangers are connected to a common fluid inlet conduit, a common fluid outlet conduit and a supply and exhaust manifold for an additional fluid.
Toward the fulfillment of these and other objects, the heat exchanger unit of the present invention comprises a plurality of tubes which are supported in a spaced parallel relationship between two spaced tube sheets. ~ conduit is provided for supplying ~fluid to the tubes and one of the tube sheets is fixed relative to the conduit while the other tube sheet moves relative to the conduit to accommodate thermal expans:ion allcl contraction o~ -the ~ubes. ~he suppor~ uni~
formed by a plural.i.t.y of interconnected strips ormed into a grid pattern de~ining a first series of openings for receiving the tubes and a second series oE openings or permitting the -.
passage of a heat exchange fluid therethrough.
BRIEF DESCRIPTION OF THE D~INGS
FIG. 1 is a vertical sectional view of a gas turbine regenerator incorporating features of the present invention; ..
FIG. 2 is an enlarged cross-sectional view taken along the line 2-2 of FIG. 1;
FIGs. 3 and 4 are views similar to FIG. 2 but depic-ting alternate embodiments of the support unit of the present ~
invention; - ' ! .
FIG. 5 is a front elevational view depicting a gas turbine.regenerator system incorporating four of the units of FIG. l; and .
FIG. 6 is a plan view of the system of FIG. 5.
DESCRIPTION OF THE PREF13RR~D E~IBODIM~NTS
Referring specifically to FIG. 1, the reference . :
numeral 10 refers in general to a gas turbine regenerator incorporating features of the present invention. ~he regener- :.
ator 10 comprises an outer tubular housing 12 partially enclosing an air conduit 14 extending coaxially with the . :.
housing with an annular space 16 being defined between the conduit and the housing.
A plurality of spaced parallel tubes 18 extend in the annular space 16 with both ends of ea.ch tube projecting from the housing 12. ~n upper tube sheet 20 and a lower tube sheet 22 receive the tubes with the ends of the tubes being mechanically expanded and we].ded in the sheets in a conventional manner.

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Both ends o the conclu:i.t 14 projec-t ou-twardly from ~he housiny 12 and extend throu;!l) a central openiny ormed in ~he ~uhe sheets 20 and 22, respectively.
An upper header 2~ is secured to the outer circumer-ence of the upper tube shee-t 20 and receives the upper end portion of the conduit 14; which has a plurality of slots 14a extending therethrough for reasons that will be explained in detail later. The upper tube sheet 20 is attached t,o the conduit 14 and the upper header 24 is attached to the upper tube sheet in any conventional manner.
A lower header 2 6 is attached to the lower tube sheet 22 and the latter in turn is attached to a slee~e 28 which extends within the lower header and over a lower portion of the conduit 14. It is noted that the diameter of the sleeve 28 is slightly greater than the diameter of the conduit 14 to permit relative movement therebetween for reasons that will be discussed later.
The lower tube sheet 22 may be attached relative to the sleeve 28, and the lower header 26 may be attached relative to the lower tube sheet in a conventional manner such as by welding or the like.
A conical base 30 is provided which is attached to the lower end of the conduit 14 by welding or the like and which thus supports the entire structure. ~he base 30 is provided with an air inlet 32 which registers with the conduit 14. As a result, air entering the inlet 32 passes upwardly through the conduit 14 before discharging through the slots 14a into the upper header 24, from which it passes into the upper ends of the tubes 18. An air outlet 34 is provided through the lower header 2~ to permit discharg~ o~ the air .. .. .

after it has passed throucJh -the tuhes 1~.
~ ot CJaSes are introduced into the lower ~nd o~ the housing 12 and pass upwardly between the tubes 18 in the space 16 before exiting ~rom the upper end of the housing, ~or reasons to be described later.
A plurality of annular support units 40 are disposed at spaced intervals throùghout the length of the tubes 18 for supporting same wlth a portion of one o~ the support units 40 being shown in detail in FIG. 2.
In particular, each support unit 40 is formed bv a plurality of metal strips 42 which are generally octagonally shaped with one series of alternating sides 42a of each strip being curved inwardly and the other series of alternating sides 42b being straight. Each straight side 42b of each strip 42 is connected to a corresponding side 42b of another strip by welding or the like as shown by the reference numeral 44, to form a grid pattern with the curved sides 42a defining a plural-ity of openings for receiving the tubes 18. The remaining .
openings defined by the grid pattern provide a free flow area for the gases passing through the housing with a minimum of resistance.
In operation, air from an air compressor or the like is introduced into the conical base 30 through the inlet 32 and passes upwardly through the conduit 14 whereby it discharges into the upper header 24, as shown by the solid flow arrows in FIG. 1. From the header 24 the air passes do~nwardly through the tubes 18 and exits through the outlet 34 formed through the lower header 26 for further passage to a combustion chamber for the turbine. Gases from the turbine exhaust at a relatively high temperatwre aré passed into the lower end of . ~
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the hous1ncJ 12 and pass upwardly through the annular space 16 and be-tween the various tubes 18, as shown by the dashed arrows, whereby they exit throuyh the upper end of the housing 12 and are directed to an exhaust stack, or escape freel,v into the atmosphere from each individual regenerator. As a result of the above counter-flow between the gases and the air, a heat exchange is effected therebetween to raise the temperature of the air and thus reduce the fuel requirements in the combus-tion chambers of the turbine.
It can be appreciated that thermal expansion of the tubes 18 in a longitudinal direction is accommodated by movement of.the lower tube sheet 22, and therefore the sleeve 28 and the lower header 26, relative to the conduit 14 which is fixed relative to the upper tube sheet 20 and the upper header 24.
A first alternate form of the support unit is shown in general by the reference numeral 50 in FIG. 3 and comprises a plurality of strips 52 which have a series of alternating curved sides 52a and straight sides 52b, similar to the strips 42 of the previous embodiment. The straight side 52b of-each strip 52 is interlaced with a straight side of another strip with one or both of the strips being slotted to provide an interlock between the strips before they are welded together at an area shown by the reference numeral 54. As in the previous embodiment, the strips 52 define a grid pattern including a plurality of openings for receiving the tubes 18, with the remaining portion of the grid pattern permitting a relatively unimpeded flow of gases through the housing 12.
~ second alternate form of the support unit is shown in general by the referenc.e numeral 56 in FI~.,. 4 and is 7 ~
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desi~ned to accommodate a series of row.s o~ tubes 1~ in an offset, or staggere~, relationship. Each unit 56 cornprises a plurality of strip~ 58 in hexayonal form and having a series of alterna-ting curved sides 5~a and straighk sides 58b. Eaeh straight side 58b of each strip 58 is connected to a straight side of an adjacent strip by welding, or the like, with the adjacent curved sides 58a defining a plurality of openings for receiving the tubes 18 and the remaining portion of the grid pattern permitting a relatively unimpeded flow o gases through the housing 12.
Referring specificall~ to FIGs. 5 and 6, a regenerator system is shown which consists of four regenerators 10 whieh are connected to a common air inlet, air outlet, gas inlet and gas outlet, and are thus able to service a relatively large gas turbine.
In particular, the regenerators lO are disposed in two spaced rows of two regenerators per row and a horizontally extending air inlet conduit 60 is provided between the two rows which is eonnected to the air inlet 32 of eaeh regenerator 10 by means of branch conduits 62.
In a similar manner, a common air outlet conduit 64 is provided which e~tends horizontally between the two rows and which is connected to the air outlets 34 of each regenerator lO by means of branch conduits 66. In this manner, air introduced into the air inlet eonduit 60 from the air compressor is routed into the air eonduit 14 of each regenerator lO
through the branch conduits 62 and the air inlets 32 o each regenerator, before passing u~wardly through the respeetive eonduits 14 of each regenerator. ~s cliseussed in conneetion with the previous embodiments, the air collects in the upper .

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header 2~ of each recJenerator 10 and passes ~ownwardly through the respective tuber, ~8 before exitiny through the respective air outlets 34 and, through the branch conduits 66, to the air outlet conduit 64 for passage to the combustion chambers of the turbine.
A supply manifold 70 is provided which surrounds the gas inlet area between the housing 12 and the lower header 26 of each regenerator 10. As a result, gases introduced from the turbine exhaust into the inlet 70a of the manifold 70 are passed into the lower end of the housing 12 of each of the regenerators lO, from which they pass upwardly through the annular space 16 in each regenerator 10 and exhaust through an upper manifold 72 having an outlet 72a or escape freely into the atmosphere from each individual regenerator.
Although not shown in the drawings, it is understood that an access opening may be provided in the base 30 and that an internal rung ladder may be provided along the conduit 14 to provide access to the upper header 24.
It can be appreciated that, as a result of the . 20 foregoing arrangement, the compactness of each individual regenerator can be maintained while the regenerators can be adapted for much larger capacity in order to service a relatively large type gas turbines. Of course, the regenerators lO can be connected in a different manner than that shown in FIGs. S and 6, such as, for example, in one row of several regenerators, or the like.
It is understood that several variations may be made in the foregoing without departing from the scope of the present invention. For example, the features of the present invention are not limited to the use of gas turbine regenerators i ~ ~
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bu-t can be equally applicable -to other heat exchanyers, such as vapor generator.s, ~eedwater heaters, waste heat boilers, air hea-ters, nuclear s-team yenerators, fossil ~ired steam generators, and the li]ce.
of course, other variations of the specific construction and arrangement of the heat exchanyer disclosed above can be made by those skilled in the art without departing from the invention as defined in the appended claims.

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SUPP~EMENTARY DISCLOSURE

FIG. 7 ls an enlarged, partial vertical sectiorl of an alternate embodiment of a gas turbine regenerator incorporat-ing features of the present invention.
~ ccording to the regenrator embodied in FIG. 7, a cooling fluicl is injected into the air stream passing through the regenerator. Since the regenerator of FIG. 7 is otherwise similar to that of FIG. 1, identical portions thereof will be referred to by the same reference numerals. In particular, an inlet pipe 72 extends through the base 30 of the regenerator of FIG. 7 and into the conduit 14, and is connected at one end to a multinozzle toroidal spray ring 74 supported within the conduit 14 by a bracket assembly 76. The other end of the pipe 72 is coupled to a suitable source of fluid, preferably demineralized water. As a result, the spray water is dis-charged through the ring 74 and into the conduit 14 where it mixes with the air entering the regenerator 10 through the inlet 32 which, for the purposes o~ this embodiment, does not extend into the conduit 14. The resulting air-water mixture ~0 passes upwardly through the conduit 14 and into the upper header 24, where its flow direction is reversed before it passes downwardly through the tubes 18 as discussed in connection with the regenerator of FIG. 1~ This relatively long flow path permits the total vaporization of the water and provides several benefits.
For example, when the inlet 32 of the regenerator of FIG. 7 is coupled to the output of an air compressor preceding the turbine, and the hot gases passed through the housing 12 in the spaces between the tubes 18 are from the turblne exhaust, the compressed air is generally at a relatively low .`, i.~ ,~.
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temperature compared to the turbine exhaust gases but still at a substantially hiyh temperature, such as 500-600F. By virtue of the air being cooled by the liquid prior to its heat exchange with the turbine exhaust gases while beiny maintained at the same pressure, more heat is absorbed from the turbine exhaust gases and therefore a more cfficient cycle to the turbine is achieved. Furthermore, the vaporization of the liquid added to the air stream provides an improved heat exchange and if the air-liquid mixture at the outlet 34 is directed to the input of a gas turbine, a higher mass flow is provided. As a result, a greater amount o fuel consumption is required in order to maintain the temperature profile of the turbine exhaust temperature, which substantially increases the horse-power generated by the turbine relative to the fuel consumption.
It is noted that the embodiment of FIG. 7 also avoids one of the main disadvantages normally associated with fluid injection in this type of environment, which is the possibility that the injected fluid may not sufficiently vaporize resulting in the fluid droplets entering the turbine causing severe damage. In order to remedy this situation, man~ prior art arrangements have included long heated inlet pipes to insure that the injected fluid is fully vaporized.
The regenerator of the present invention has the inherent benefit that the distance between inlet 32 and outlet 34 is sufficiently long to insure full vaporiz-ation under controlled fluid injection and temperature conditions. This construction therefore eliminates construction o costly auxiliary equip-ment for the injection o ~luids.

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~'3~4 It is emphasized tha-t, althouyh the 1uid injected into the conduit 14 is preferably water because of its high latent heat value, other fluids may be injected, such as waste products from other processes and the like which could contain' a combustible material artd thus serve as a suppl~mentary fuel as well as a cooling agent.
It should be understood that the fluid injection system illustrated in FIG. 7 may be adapted for any of the different embodiments described herein.

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Claims

WHAT IS CLAIMED IS:

1. A heat exchanger comprising a conduit having an inlet for receiving a first heat exchange fluid, a plurality of spaced tubes extending parallel to said conduit, means for passing said first heat exchange fluid from said conduit to said tubes, means for securing one end portion of each of said tubes relative to said conduit, means for supporting the other end portion of each of said tubes relative to said conduit in a manner to permit relative movement between said other end portion of said tubes and said conduit, means for passing a second heat exchange fluid in a counterflow relation to said first heat exchange fluid passing through said tubes, and a support unit for supporting said tubes, said unit including a plurality of interconnected strips formed into a grid pattern defining a first series of openings for receiving said tubes and a second series of openings for permitting the passage of said other heat exchange fluid therethrough, said strips being generally octagonal shaped with one series of alternating sides being curved inwardly to define said first series of openings and with another series of alternating sides being connected to corresponding sides of an adjacent strip, said connected sides of said strips being interlaced with at least one side being slotted to facilitate said connection.

CLAIMS SUPPORTED BY SUPPLEMENTAL DISCLOSURE

2. The heat exchanger of claim 1 further comprising fluid injection means for injecting a cooling fluid into said conduit near the inlet thereof for mixing with said first fluid.

3. The heat exchanger of claim 2 wherein said means for securing one end portion of said tubes relative to said conduit comprises a tubesheet connected to said conduit, said means for passing said heat exchange fluid from said conduit to said tubes comprises a header connected to said tubesheet, whereby said header reverses the fluid flow from said conduit and passes said fluid into said tubes, said means for support-ing the other end portion of each of said tubes relative to said conduit in a manner to permit relative movement between said other end portion of said tubes and said conduit compris-in an additional tubesheet attached to said other ends of said tubes, and further including a sleeve connected to said addi-tional tubesheet and surrounding said conduit with the inner wall of said sleeve extending in a spaced relation relative to the outer surface of said conduit.

4. The heat exchanger of claim 2 or claim 3 wherein said cooling fluid comprises a liquid and wherein the heat ex-change between said first and second fluids is sufficient to heat said first fluid and vaporize said cooling fluid.

5. The heat exchanger of claim 2 wherein said fluid injection means comprises a toroidal spray nozzle having a plurality of holes, and an inlet for communicating a fluid supply to said nozzle for injection into said conduit.

6. The heat exchanger of claim 5 further comprising bracket means for supporting said toroidal spray nozzle within said conduit.

7. The heat exchanger of claim 2 wherein said fluid injection means comprises means for injecting water to said conduit.

8. The heat exchanger of claim 2 wherein said cooling fluid comprises a liquid, at least a portion of which is combustible.