US20110308228A1

US20110308228A1 - Fin and Tube Heat Exchanger

Info

Publication number: US20110308228A1
Application number: US12/818,218
Authority: US
Inventors: Sebastian W. Freund
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 2010-06-18
Filing date: 2010-06-18
Publication date: 2011-12-22
Also published as: KR101795039B1; DE102011050865A8; KR20110138179A; JP6050567B2; GB201109855D0; DE102011050865A1; JP2012002498A; GB2481296A; GB2481296B

Abstract

The present application provides a fin and tube heat exchanger. The fin and tube heat exchanger may include a number of tubes with a number of fins positioned on each of the tubes. The tubes may include a first set of tubes and a second set of tubes with the first set of tubes including an offset position as compared to the second set of tubes.

Description

TECHNICAL FIELD

The present application relates generally to fin and tube heat exchangers and more particularly relates to a semi-staggered arranged compact fin and tube heat exchanger with rectangular fins and vortex generators so as to maximize heat transfer while minimizing the pressure loss therethrough.

BACKGROUND OF THE INVENTION

A broad variety of fin and tube type heat exchangers and similar structures are commercially available. One of the main design goals in the construction of fin and tube type heat exchangers focuses on maximizing heat transfer while minimizing the pressure loss therethrough. Generally described, the extent of the pressure loss may be directly related to the operating costs and the overall energy losses and efficiency of the heat exchanger and its use.
One example of known fin and tube heat exchanger designs includes the use of tube bundles with densely-spaced and spirally-wound circular fins. The use of such circular fins, however, may cause relatively large bypass flows, wake regions, and lower heat transfer coefficients because of the generally reduced air velocity therethrough. Moreover, the bypass flow may exacerbate fouling problems about the fins and the spaces therebetween as well as depress the heat transfer coefficiences. The circular fins also may limit the fin spacing and hence the overall useful surface area per tube.
Continuous plate fins and substantially square fins also have been used. Such continuous plate fins tend to have a lower pressure loss per unit of transferred heat as compared to typical circular fins. Continuous plate fins have been used to make very compact and efficient heat exchangers, but the continuous plate fins and the square fins generally have not been adapted for large scale power plant applications such as heat recovery steam generators or similar types of equipment that generally require large heat transfer areas, tubes with larger diameters, and/or fins made of steel.
Known tube bundle arrangements generally are configured either in an in-line or a staggered alignment. The staggered arrangement generally may be favored as such an arrangement gives a higher heat transfer coefficient with somewhat less bypass flow as compared to an in-line arrangement. The pressure loss of such a staggered arrangement, however, may be relatively high due to profile drag caused by the tubes. The in-line arrangement places each tube in the wake of the preceding tube so as to lower the overall drag. Oval and elliptical shaped tubes and fins also have been used to reduce drag and pressure losses, but such tubes generally cannot withstand the very high pressures usually found in power plant equipment.
Various techniques have been explored to enhance the heat transfer on a fin surface, including the use of louvers, corrugations, undulations, serrations, winglet vortex generators, and the like. Most of these enhancement technologies are used on continuous fin heat exchangers while dimples and serrations may be used on individual circular fins. Several of these enhancement technologies also may be combined on a given fin or a set of fins.
There is thus a desire therefore for an improved compact fin and tube heat exchanger to increase the heat transfer rate per unit pressure loss so as to provide a smaller and less expensive heat exchanger with lower energy losses and lower overall life cycle costs. Such a fin and tube heat exchanger preferably may be used for a variety of gas to liquid or gas to steam heat transfer applications and specifically may be used for power plant operations and the like.

SUMMARY OF THE INVENTION

The present application thus provides a fin and tube heat exchanger. The fin and tube heat exchanger may include a number of tubes with a number of fins positioned on each of the tubes. The tubes may include a first set of tubes and a second set of tubes with the first set of tubes including an offset position as compared to the second set of tubes.
The present application further provides a fin and tube heat exchanger. The fin and tube heat exchanger may include a number of tubes with a number of rectangular fins positioned on each of the tubes. The rectangular fins may include one or more vortex generators thereon.
The present application further provides a fin and tube heat exchanger. The fin and tube heat exchanger may include a number of tubes with a first set of tubes having an offset position as compared to a second set of tubes and a number of rectangular fins positioned on each of the tubes. The rectangular fins may include a number of vortex generators thereon.
These and other features and improvements of the present application will become apparent to one of ordinary skill in the art upon review of the following detailed description when taken in conjunction with the several drawings and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a gas turbine engine.

FIG. 2 is a perspective view of a portion of a semi-staggered fin and tube heat exchanger as may be described herein.

FIG. 3 is a perspective view of an individual rectangular plate fin with vortex generators as may be used with the semi-staggered fin and tube heat exchanger of FIG. 2.

DETAILED DESCRIPTION

Referring now to the drawings, in which like numerals refer to like elements through out the several views, FIG. 1 shows a schematic view of a gas turbine engine 100 as may be described herein. The gas turbine engine 100 may include a compressor 110. The compressor 110 compresses an incoming flow of air 120. The compressor 110 delivers the compressed flow of air 120 to a combustor 130. The combustor 130 mixes the compressed flow of air 120 with a compressed flow of fuel 140 and ignites the mixture to create a flow of combustion gases 150. Although only a single combustor 130 is shown, the gas turbine engine 100 may include a number of combustors 130.
The flow of combustion gases 150 are in turn delivered to a turbine 160. The flow of combustion gases 150 drives the turbine 160 so as to produce mechanical work via the turning of a turbine rotor 170. The mechanical work produced in the turbine 160 drives the compressor 110 and an external load such as an electrical generator 180 and the like via the turbine rotor 170.
The flow of now spent combustion gases 150 then may be delivered to a heat recovery steam generator 190 or other types of heat exchanges. The flow of the spent combustion gases 150 to the heat recovery steam generator 190 may heat a flow of steam 200 therethrough for use in, for example, a steam turbine, a fuel preheater, and/or for other types of work. The flow of the combustion gases 150 then may be vented or otherwise disposed.
The gas turbine engine 100 may use natural gas, various types of syngas, and other types of fuels. The gas turbine engine 100 may be any number of different turbines offered by General Electric Company of Schenectady, N.Y. or otherwise. The gas turbine engine 100 may have other configurations and may use other types of components. Other types of gas turbine engines also may be used herein. Multiple gas turbine engines 100, other types of turbines, and other types of power generation equipment may be used herein together.
Generally described, the heat recovery steam generator 190 may be a non-contact heat exchanger that allows feed water for the steam generation process and the like to be heated by the otherwise wasted flow of the spent combustion gases 150. The heat recovery steam generator 190 may be a large duct with tube bundles interposed therein such that water is heated to steam as the flow of combustion gases 150 pass through the duct. Other heat recovery steam generator configurations and other types of heat exchange devices may be used herein.
FIG. 2 shows a portion of a semi-staggered fin and tube heat exchanger 210 as may be described herein. The semi-staggered fin and tube heat exchanger 210 may be used as part of the heat recovery steam generator 190 or for any type of heat exchange device or purpose.
The semi-staggered fin and tube heat exchanger 210 includes a number of tubes 220 protruding therethrough with a number of fins 230 positioned thereon. (Only one protruding tube 220 is shown in FIG. 2 for clarity.) Any number of tubes 220 and fins 230 may be used herein. The semi-staggered fin and tube heat exchanger 210 may be relatively compact as compared to existing fin and tube heat exchanges but may have any desired size, shape, and/or configuration.
The semi-staggered fin and tube heat exchanger 210 may include the tubes 220 positioned in a staggered relationship. Specifically, a first set 240 of tubes 220 may be staggered or offset from a second set 250 of tubes 220. The first set 240 of tubes 220 may include a first row 260 and a second row 270 with the tubes 220 having an in-line position 275 with respect to a flow of air 280 therethrough. The second set 250 of tubes 220 may include a third row 290 and a fourth row 300 with the tubes 220 therein also having the in-line position 275. Although pairs of tubes 220 are shown in the first set 240 and the second set 250, any number of rows 260, 270 and 290, 300 may be used herein with any number of tubes 220 therein. The first set 240 and the second set 250 may have an offset position 305 with respect to each other to form the semi-staggered relationship. The offset position 305 may be about of half of the transverse spacing of a fin 230. Other types of offsets, spacings, and configurations may be used herein.
As is shown in FIGS. 2 and 3, the fins 230 of the semi-staggered fin and tube heat exchanger 210 may be in the form of substantially rectangular fins 310. Each rectangular fin 310 may have a number of vortex generators 320 positioned on a corner thereof. In this example, the vortex generators 320 may have a substantially triangular shape 330. Further, an opposed pair of the vortex generators 320 may have an upward angle 340 and an opposed pair of vortex generators 320 may have a downward angle 350. Any number of vortex generators 320 in other sizes, configurations, and/or angles may be used herein.
The rectangular fins 310 also may have a substantially eccentric position 360 about each tube 220. As a result, the distance between the rows 260, 270 and 290, 300 of each set 240, 250 may be minimized (and hence the distance between the tubes 220 of each set 240, 250 may be increased.) Other types of positionings may be used herein. A gap 370 may exist between each rectangular fin 310. The size and shape of the gap 370 may vary. The gap 370 may be sized such that the rectangular fins 310 act as a substantially continuous fin in use.
As described above, an in-line tube arrangement generally has the benefit of a lower pressure loss while a staggered arrangement generally leads to higher heat transfer. In use, the semi-staggered fin and tube heat exchanger 210 described herein thus combines the advantages of both positionings. Specifically in this example, the second row 270 of the first set 240 and the fourth row 300 of the second set 250 are generally positioned in the wake of the first row 260 of the first set 240 and the third row 290 of the second set 250, respectively. This staggered or off-set position 305 thus reduces the aerodynamic profile drag that may account for part of the pressure loss, particularly given the relatively small distances between the in- line rows 260, 270 and 290, 300 of the tubes 220 based in part on the eccentric position 360 of the fins 230 of the rows 260, 270 and 290, 300. Similarly, staggering the first set 240 and the second set 250 of the tubes 220 may generate or enhance horseshoe and wake vortices so as to enhance heat transfer on the fins 230.
The rectangular fins 310 of the semi-staggered fin and tube heat exchanger 210 act largely as a continuous plate fin so as to allow for tight fin spacing without altering the flow field or creating much or any of a bypass flow. The size of the gap 370 between the rectangular fins 310 may enable the installation of the individual tubes 220 into a compact bundle while permitting much less bypass flow as compared to, for example, the circular fin and tube bundles described above. Specifically, the gap 370 may be small enough so as to form semi-continuous plate fins but large enough to defuse substantially the boundary layers. The gap 370 thus allows for some mixing and boundary layer destruction between the fins 310 so as to have positive effect on heat transfer performance.
The triangular tips 330 of the vortex generators 320 of the semi-staggered fin and tube heat exchanger 210 also create and/or enhance horseshoe and/or wake-like vortices with respect to the staggered sets 240, 250. Longitudinal and other types of vortices also may be generated. These vortices tend to enhance the overall heat transfer on the rectangular fins 310. The use of the alternating upward and downward angles 340, 350 may redirect the flow to impinge on the upper and lower fins 310 respectively. Such a flow also may defuse the boundary layers while enhancing the longitudinal vortices and further intensifying the heat transfer.
The semi-staggered fin and tube heat exchanger 210 thus provides the staggered sets 240, 250 of the tubes 220 with the offset position 305. Each tube 220 may have the number of rectangular fins 310 with a number of the vortex generators 320 thereon. The fins 310 may include an eccentric position 360 so as to minimize the distance between the rows, 260, 270 and 290, 300 of each set 240, 250 while the fins 210 also have small gaps 370 therebetween. The semi-staggered fin and tube heat exchanger 210 thus provides a lower pressure loss as compared to conventional fin and tube designs with a higher heat transfer per tube. The semi-staggered fin and tube heat exchanger 210 also may be more compact with lower operating costs and fewer tube rows for a given duty.
The semi-staggered fin and tube heat exchanger 210 thus may be used for a variety of gas to liquid or gas to steam heat transfer applications and specifically may be used for power plant operations and the like. Smaller, better, and cheaper heat exchangers generally provide for a less expensive energy system with a smaller footprint and lower operating costs.
It should be understood that the foregoing relates only to the preferred embodiments of the present application and that numerous changes and modifications may be made herein by one of ordinary skill in the art without departing from the general spirit and scope of the invention as defined by the following claims and the equivalents thereof.

Claims

1. A fin and tube heat exchanger, comprising:

a plurality of tubes; and

a plurality of fins positioned on each of the plurality of tubes;

the plurality of tubes comprising a first set of tubes and a second set of tubes;

wherein the first set of tubes comprises an offset position as compared to the second set of tubes.

2. The fin and tube heat exchanger of claim 1, wherein the first set of tubes comprises a first row of tubes and a second row of tubes.

3. The fin and tube heat exchanger of claim 2, wherein the first row of tubes and the second row of tubes comprise an inline position relative to a flow across the first row of tubes and the second row of tubes.

4. The fin and tube heat exchanger of claim 2, wherein the second set of tubes comprises a third row of tubes and a fourth row of tubes.

5. The fin and tube heat exchanger of claim 1, wherein the offset position comprises about a half of a fin length

6. The fin and tube heat exchanger of claim 1, wherein the plurality of fins comprises a plurality of rectangular fins.

7. The fin and tube heat exchanger of claim 1, wherein the plurality of fins comprises a plurality of vortex generators thereon.

8. The fin and tube heat exchanger of claim 7, wherein the plurality of vortex generators comprises a substantially triangular shape.

9. The fin and tube heat exchanger of claim 7, wherein the plurality of vortex generators comprises one or more upward angles and one or more downward angles.

10. The fin and tube heat exchanger of claim 1, wherein the plurality of fins comprises a substantially eccentric position about each tube.

11. The fin and tube heat exchanger of claim 1, wherein a first plurality of fins positioned on a first tube and a second plurality of fins positioned on a second tube comprise a gap therebetween.

12. The fin and tube heat exchanger of claim 1, wherein the fin and tube heat exchanger comprises a heat recovery steam generator.

13. A fin and tube heat exchanger, comprising:

a plurality of tubes; and

a plurality of rectangular fins positioned on each of the plurality of tubes;

wherein the plurality of rectangular fins comprises one or more vortex generators thereon.

14. The fin and tube heat exchanger of claim 13, wherein the one or more vortex generators comprise a substantially triangular shape.

15. The fin and tube heat exchanger of claim 13, wherein the one or more vortex generators comprise one or more upward angles and one or more downward angles.

16. The fin and tube heat exchanger of claim 13, wherein the one or more vortex generators comprise an opposed pair of upward angles and an opposed pair downward angles.

17. The fin and tube heat exchanger of claim 13, wherein the plurality of rectangular fins comprises a substantially eccentric position about each tube.

18. The fin and tube heat exchanger of claim 13, wherein a first plurality of rectangular fins positioned on a first tube and a second plurality of rectangular fins positioned on a second tube comprise a gap therebetween.

19. The fin and tube heat exchanger of claim 13, wherein the plurality of tubes comprises a first set of tubes and a second set of tubes and wherein the first set of tubes comprises an offset position as compared to the second set of tubes.

20. A fin and tube heat exchanger, comprising:

a plurality of tubes

wherein the first set of tubes comprises an offset position as compared to the second set of tubes; and

a plurality of rectangular fins positioned on each of the plurality of tubes;

wherein the plurality of rectangular fins comprises a plurality of vortex generators thereon.