JP2012002498A - Fin and tube heat exchanger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a smaller and inexpensive heat exchanger with lower energy loss and lower overall life cycle costs.SOLUTION: The fin and tube heat exchanger 210 includes: a plurality of tubes 220 with a plurality of fins 230 positioned on each of the tubes 220. The tubes 220 include a first set of tubes 240 and a second set of tubes 250, the first set of tubes 240 having an offset position 305 as compared to the second set of tubes 250. The first set of tubes 240 may include a first row of tubes 260 and a second row of tubes 270.

Description

  The present invention relates generally to finned-tube heat exchangers, and more particularly to a semi-twisted arrangement small finned-tube heat with rectangular fins and vortex generators to maximize heat transfer while minimizing pressure loss. Regarding the exchanger.

  Various finned tube heat exchangers and similar structures are commercially available. One of the main design goals of the finned tube heat exchanger structure focuses on maximizing heat transfer while minimizing pressure loss. In general, it can be said that the range of pressure loss is directly related to the operation and maintenance costs of the heat exchanger and its utilization and the overall energy loss and efficiency.

  One example of a known finned tube heat exchanger design is the utilization of a bundle of tubes with circular fins that are closely spaced and helically twisted. However, the use of such circular fins results in a relatively large bypass flow, wake region, and low heat transfer coefficient due to the generally reduced airflow velocity therethrough. Furthermore, the bypass flow not only exacerbates the fouling problem with fins and the spacing between them, but also reduces the heat transfer coefficient. Circular fins also limit the fin spacing and thus the total effective surface area per tube.

  Continuous plate fins and generally square fins were also used. Such continuous plate fins tend to have lower pressure losses per unit of heat transferred compared to typical circular fins. Continuous plate fins have been used to produce very small and efficient heat exchangers, but continuous plate fins and square fins are generally large heat transfer areas, tubes with large diameters, and / or steel. It has generally not been suitable for large-scale power plant applications such as heat recovery steam generators or similar types of equipment that require made fins.

  Known tube bundle arrangements typically consist of a series or twisted arrangement. A torsional arrangement is generally particularly advantageous because such an arrangement exhibits a high heat transfer coefficient with a somewhat reduced bypass flow compared to a series arrangement. However, the pressure loss of such a twisted arrangement is relatively high due to the shape drag caused by the tube. The series arrangement places each tube following the previous tube so as to reduce the overall drag. Oval and elliptical shaped tubes and fins have also been used to reduce drag and pressure loss, but such tubes generally cannot withstand the ultra-high pressures normally found in power plant equipment.

  Various techniques are used to enhance heat transfer on the fin surface, including the use of louvers, corrugations (undulations), undulations (swells), serrations, winglet vortex generators, etc. Being explored. Most of these improved techniques are used in continuous fin heat exchangers, whereas dimples and serrations are used in individual circular fins. Some of these improved techniques may be combined on a given fin or series of fins.

US Pat. No. 6,578,627 B1

  Thus, in order to provide a small and inexpensive heat exchanger with low energy loss and low overall life cycle cost, the small finned tube heat system improved to increase the heat transfer rate per unit pressure loss. An exchanger is desired. Such a finned-tube heat exchanger is preferably used for heat transfer from various gases to liquids or gas to steam, and specifically used for power plant operations and the like.

  Accordingly, the present invention provides a finned tube heat exchanger. The finned tube heat exchanger includes a plurality of tubes with a plurality of fins disposed on each tube. The tubes include a first set of tubes and a second set of tubes, the first set of tubes having an offset position relative to the second set of tubes.

  The present invention further provides a finned tube heat exchanger. The finned tube heat exchanger includes a plurality of tubes with a plurality of rectangular fins disposed on each tube. The rectangular fin includes one or more vortex generating pieces thereon.

  The present invention further provides a finned tube heat exchanger. The finned tube heat exchanger includes a plurality of tubes with a first set of tubes having offset positions relative to the second set of tubes, and a plurality of rectangular fins disposed on each tube. The rectangular fin includes a plurality of vortex generating pieces.

  These and other features and improvements of the present invention will become apparent to those of ordinary skill in the art upon review of the following detailed description, taken in conjunction with the drawings and the appended claims.

1 is a schematic view of a gas turbine engine. 1 is a perspective view of a portion of a semi-twisted finned-tube heat exchanger described herein. FIG. FIG. 3 is a perspective view of individual rectangular plate fins with vortex generating pieces used in the semi-twisted finned tube heat exchanger of FIG. 2.

  Referring now to the drawings wherein like numerals refer to like elements throughout, FIG. 1 shows a schematic diagram of a gas turbine engine 100 as described herein. The gas turbine engine 100 includes a compressor 110. The compressor 110 compresses the incoming air stream 120. The compressor 110 feeds the compressed air stream 120 into the combustor 130. Combustor 130 mixes compressed air stream 120 with compressed fuel stream 140 and ignites the mixture to produce combustion gas stream 150. Although only a single combustor 130 is shown, the gas turbine engine 100 may include multiple combustors 130.

  The combustion gas stream 150 is then fed into the turbine 160. Combustion gas stream 150 drives turbine 160 to create a mechanical action by rotation of turbine rotor 170. The mechanical action generated in the turbine 160 drives the compressor 110 and an external load such as the generator 180 via the turbine rotor 170.

  The spent combustion gas stream 150 is then fed into a heat recovery steam generator 190 or other type of heat exchanger. The spent combustion gas stream 150 to the heat recovery steam generator 190 heats the steam stream 200 used, for example, for steam turbines, fuel preheaters, and / or other types of operations. Thereafter, the combustion gas stream 150 is evacuated or otherwise processed.

  The gas turbine engine 100 may use natural gas, various types of syngas, and other types of fuel. The gas turbine engine 100 may or may not be any number of different turbines provided by General Electric Company of Schenectady, NY. The gas turbine engine 100 may have other configurations and may use other types of components. Other types of gas turbine engines can also be used herein. Multiple gas turbine engines 100, other types of turbines, and other types of power generation equipment may be used in combination.

  Generally, the heat recovery steam generator 190 is a non-contact heat exchanger that can heat feed water for a steam generation process or the like with a spent combustion gas stream 150 that is otherwise wasted. I can say that. The heat recovery steam generator 190 is a large duct with a bundle of tubes interposed therein, and is heated until the water becomes steam when the combustion gas stream 150 passes through the duct. . Other heat recovery steam generator configurations and other types of heat exchange devices may be used herein.

  FIG. 2 illustrates a portion of the semi-twisted finned-tube heat exchanger 210 described herein. The semi-twisted finned-tube heat exchanger 210 can be used as part of the heat recovery steam generator 190 or for any type of heat exchange device or heat exchange purposes.

  Semi-twisted finned tube heat exchanger 210 includes a plurality of tubes 220 projecting therethrough with a plurality of fins 230 disposed thereon. (For clarity, only one protruding tube 220 is shown.) Any number of tubes 220 and fins 230 may be used herein. The semi-twisted finned-tube heat exchanger 210 is relatively small compared to existing finned-tube heat exchangers, but may have a desired size, shape, and / or configuration.

  Semi-twisted finned tube heat exchanger 210 includes tubes 220 arranged in a twisted relationship. Specifically, the first set 240 of tubes 220 is twisted or offset from the second set 250 of tubes 220. The first set 240 of tubes 220 includes a first row 260 and a second row 270 with tubes 220 having a series position 275 relative to the air flow 280 therethrough. The second set 250 of tubes 220 includes a third row 290 and a fourth row 300 with tubes 220 also having a series position 275 therein. Although pairs of tubes 220 are shown in first set 240 and second set 250, any number of rows 260, 270 and 290,300 with any number of tubes 220 therein are shown herein. May be used. The first set 240 and the second set 250 have an offset position 305 with respect to each other to form a semi-twisted relationship. The offset position 305 is approximately half of the lateral spacing of the fins 230. Other types of offsets, gaps, and configurations may be used herein.

  As shown in FIGS. 2 and 3, the fins 230 of the semi-twisted finned-tube heat exchanger 210 are substantially rectangular fins 310. Each rectangular fin 310 has a plurality of vortex generating pieces 320 arranged at its corners. In this example, the vortex generating piece 320 has a substantially triangular shape 330. Further, one opposing pair of vortex generating pieces 320 has an upward angle 340 and another opposing pair of vortex generating pieces 320 has a downward angle 350. Any number of vortex generators 320 of other dimensions, configurations, and / or angles may be used herein.

  The rectangular fin 310 also has a generally eccentric position 360 around each tube 220. As a result, the distance between rows 260, 270 and 290, 300 of each set 240, 250 is minimized (thus the distance between the tubes 220 of each set 240, 250 is increased). Other types of arrangements may be used herein. There is a gap 370 between each rectangular fin 310. The size and shape of the gap 370 may vary. The gap 370 is dimensioned so that the rectangular fin 310 acts as a generally continuous fin when in use.

  As described above, the series tube arrangement has the advantage of generally low pressure loss, while the twisted arrangement generally provides higher heat transfer. Thus, in use, the semi-twisted finned tube heat exchanger 210 described herein combines the advantages of both arrangements. 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 in the first row 260 of the first set 240 and the third row 290 of the second set 250, respectively. It is arranged next. Thus, this twist or offset position 305 compares the distance between the series rows 260, 270 and 290, 300 of the tube 220, in particular based in part on the eccentric position 360 of the fins 230 of the rows 260, 270 and 290, 300. To reduce the aerodynamic shape drag, which is part of the pressure loss. Similarly, shifting the first set 240 and the second set 250 of tubes 220 creates or enhances horseshoe vortices and wake vortices to enhance heat transfer on the fins 230.

  The rectangular fins 310 of the semi-twisted finned-tube heat exchanger 210 are mainly continuous so that narrow fin spacing is possible without changing the flow field or creating too much or little bypass flow. Acts as a plate fin. The size of the gap 370 between the rectangular fins 310 allows, for example, less bypass flow than the circular fins and tube bundles described above, and allows attachment of individual tubes 220 to a small bundle. Specifically, gap 370 is small enough to form a semi-continuous plate fin, but is large enough to substantially remove the boundary layer. Thus, the gap 370 can be partially mixed and boundary layer broken between the fins 310 to have a positive impact on heat transfer performance.

  The triangular end 330 of the vortex generating piece 320 of the semi-twisted finned-tube heat exchanger 210 also generates and / or enhances horseshoe vortices and / or wake vortices for the twist sets 240,250. Longitudinal vortices and other types of vortices can also be generated. These vortices tend to increase the overall heat transfer on the rectangular fins 310. By using alternate upward and downward angles 340, 350, the flow direction can be changed to collide with the upper and lower fins 310, respectively. Such a flow can also remove the boundary layer while strengthening the longitudinal vortex to further increase heat transfer.

  Thus, the semi-twisted finned tube heat exchanger 210 provides a twisted set 240,250 of tubes 220 having offset positions 305. Each tube 220 has a plurality of rectangular fins 310 with a plurality of vortex generating pieces 320 thereon. While fin 310 includes an eccentric position 360 to minimize the distance between rows 260, 270 and 290, 300 of each set 240, 250, fin 310 also has a minimum gap 370 therebetween. Thus, the semi-twisted finned tube heat exchanger 210 results in a lower pressure loss compared to conventional finned tube designs with high heat transfer per tube. The semi-twisted finned-tube heat exchanger 210 is also small and has low operation and maintenance costs for a given job and few tube rows.

  Therefore, the semi-twisted finned-tube heat exchanger 210 is used for heat transfer from various gases to liquids or gas to steam, and can be used specifically for power plant operations. Smaller, better and cheaper heat exchangers generally provide an inexpensive energy system with a small footprint and low operating and maintenance costs.

  The above description relates only to the preferred embodiments of the present invention, and those skilled in the art without departing from the general technical idea and scope of the present invention defined by the claims and their equivalents. It should be understood that many changes and modifications can be made herein.

DESCRIPTION OF SYMBOLS 100 Gas turbine engine 110 Compressor 120 Air flow 130 Combustor 140 Fuel flow 150 Combustion gas flow 160 Turbine 170 Rotor 180 Generator 190 Heat recovery steam generator 200 Steam flow 210 Semi-twisted finned pipe heat exchanger 220 Pipe 230 Fin 240 1st set 250 2nd set 260 1st row 270 2nd row 275 Series position 280 Air flow 290 3rd row 300 4th row 305 Offset position 310 Rectangular fin 320 Vortex generating piece 330 Triangular shape 340 Upward angle 350 Downward angle 360 Eccentric position 370 Gap

Claims (12)

A plurality of tubes (220), said plurality of tubes (220) including a first set of tubes (240) and a second set of tubes (250);
A plurality of fins (230) disposed on each of the plurality of tubes (220);
The finned tube heat exchanger (210), wherein the first set of tubes (240) has an offset position (305) relative to the second set of tubes (250).   The finned tube heat exchanger (210) of claim 1, wherein the first set of tubes (240) comprises a first row of tubes (260) and a second row of tubes (270).   The first row of tubes (260) and the second row of tubes (270) are in series with the flow (280) across the first row of tubes (260) and the second row of tubes (270). The finned tube heat exchanger (210) of claim 2 having a position (275).   The finned tube heat exchanger (210) of claim 2, wherein the second set (250) of tubes comprises a third row of tubes (290) and a fourth row of tubes (300).   The finned tube heat exchanger (210) of claim 1, wherein the offset position (305) is approximately half the length of the fin (230).   The finned tube heat exchanger (210) of claim 1, wherein the plurality of fins (230) comprises a plurality of rectangular fins (310).   The finned tube heat exchanger (210) of claim 1, wherein the plurality of fins (230) includes a plurality of vortex generating pieces (320) thereon.   The finned tube heat exchanger (210) according to claim 7, wherein the plurality of vortex generating pieces (320) have a substantially triangular shape (330).   The finned tube heat exchanger (210) of claim 7, wherein the plurality of vortex generating pieces (320) have one or more upward angles (340) and one or more downward angles (350).   The finned tube heat exchanger (210) of claim 1, wherein the plurality of fins (230) have a substantially eccentric position (360) around each tube (220).   A first plurality of fins (230) disposed on the first tube (220) and a second plurality of fins (230) disposed on the second tube (220) have a gap therebetween. The finned-tube heat exchanger (210) of claim 1 having (370).   The finned-tube heat exchanger (210) of claim 1, comprising a heat recovery steam generator (190).