HEAT EXCHANGER AND METHOD
A shell and tube heat exchanger includes a plurality of tubes having non-circular cross sectional shapes to improve heat transfer. The tubes may have central portions having an oblong cross-sectional shape with generally flat opposite side faces. The side faces may include raised portions to increase heat transfer. Alternatively, the tubes may have a C-shape in cross section. The shape of the tubes promotes thin film boiling of the fluid in the tubes to improve heat transfer.
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This application claims the benefit of U.S. Provisional Application No. 61/738,080 filed on Dec. 17, 2012, entitled, “HEAT EXCHANGER AND METHOD”, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTIONVarious types of shell and tube heat exchangers have been developed. Known heat exchangers may include a shell having fluid inlets and outlets to provide for circulation of fluid through the shell. A plurality of smaller tubes are disposed within the shell. The smaller tubes have inlets and outlets disposed outside the shell whereby fluid can flow through the tubes. Heat is thereby exchanged between the fluid flowing through the shell and the fluid flowing through the tubes.
With reference to
With reference to
The tube assembly 18 includes a plurality of boiler tubes 24 having opposite ends 30 and 32 that are connected to end plates 34 and 36, respectively. End plate 36 is fluidly connected to a fluid inlet 38 that receives inlet or tap water 40. The water 40 flows upwardly through the boiler tubes 24, and enters space 42 above plate 34 in the form of steam or vapor. The steam/vapor 46 exits space 42, and flows to a blower or compressor (not shown). Waste water and particulate matter 48 flows out of an outlet 50 of shell 16. The heat exchanger 15 may include a flow straightener 52 positioned on or adjacent plate 36 to direct the flow of water from inlet 38 through end plate 36 into tubes 24. As discussed in more detail below, tubes 24 include end portions 54 having a circular cross sectional shape enabling the ends to be connected to circular openings 56 in end plates 34 and 36. The tubes 24 also include flattened central portions 58 forming an elongated/flat passageway 60 to promote heat transfer between fluid flowing through tubes 24 and fluid flowing through cavity 20 of shell 16. As discussed in more detail below, the tubes 24 provide increased heat transfer, such that the length “L” of the tubes 24 and length “L1” of the heat exchanger 15 can be significantly reduced relative to known configurations.
During fabrication (
Referring to
With further reference to
With further reference to
It will be understood that the flattened central portions 58 may, in some cases, be formed after the tubes 12 are connected to the end plates 34 and 36. For example, the ends 54 of a tube 12 may be positioned in openings 76, and a single forming member or “bullet” may be drawn or pushed through the length of tube 12 to thereby expand the tube 12 along its entire length. This expansion causes a tight mechanical fit between ends 54 of a tube 12 and end plates 34 and 36. Soldering or brazing may also be utilized to secure the joints between tubes 12 and end plates 34 and 36. The individual tubes 12 may then be flattened utilizing forming members or dies 14 after the tubes 12 are connected to the end plates 34 and 36.
In
The boiler tubes 24 may be formed of copper, aluminum, or other suitable material. If the tubes 12 comprise aluminum or other material that degrades when exposed to heat, steam, boiling water, etc., the tubes 24 may be coated with an epoxy material or other suitable coating to insure that the tubes 24 can withstand the adverse conditions experienced during operation of heat exchanger 15.
After subassembly 80 (
The flattened central portions 58 of tubes 24 promote thin film boiling of water passing through the tubes 24 to thereby provide for efficient transfer of heat between fluid passing through tubes 24 and fluid circulating through cavity 20 of shell 16. The passageways 60 formed by flattened central portions 58 have an oblong cross sectional shape with an internal dimension of about 0.2 by about 1.5 inches. It will be understood that the specific dimensions of the flattened portions 58 of tubes 24 and the internal passageways 60 may vary depending upon the requirements of a particular application. In contrast to known tubes with internal rods (e.g.
With further reference to
Tubes 24A may be formed from extruded aluminum or other suitable material as shown in
Alternatively, tubes 24A may be formed from sheet metal or the like as shown in
The folding operations of
The tubes 24A form elongated passageways 86A, 86B, and 86C (
(
End plates 34A and 36A of heat exchanger 15 (
The transfer of heat into passageway 86 (or passageways 86A, 86B, and 86C) through side walls 88 and 90 on both sides of the internal passageways 86 promotes thin film boiling of water flowing through tubes 24A. This increases heat transfer between material flowing through tubes 24A and fluid flowing through shell 16A of heat exchanger 15A. Similarly, heat is transferred through both side walls 68 of tubes 24 (
As discussed above, the tubes 24 and 24A, and end plates 34, 36, 34A, and 36A may be formed from a suitable metal material such as copper or aluminum. Alternatively, one or more of these components may be formed from polymer materials having the required strength and durability required to withstand the operating conditions of the heat exchangers 15, 15A.
A heat exchanger according to the present invention as described above in connection with
Claims
1. A heat exchanger, comprising:
- a shell defining a cavity and including fluid inlets and outlets to permit flow of a first fluid through the cavity;
- an inner tube assembly comprising at least one elongated tube and fluid conduits connected to opposite ends of the tube, the fluid conduits extending outside the shell to permit flow of a second fluid through the inner tube assembly; and wherein:
- the at least one tube includes an elongated internal passageway, wherein at least a portion of the elongated internal passageway of the tube has an oblong shape in cross section to promote thin film boiling of fluid flowing through the elongated internal passageway to thereby provide increased heat transfer from the first fluid to the second fluid.
2. The heat exchanger of claim 1, wherein:
- the tube comprises a plurality of tubes having elongated internal passageways, wherein at least a portion of the elongated passageways have oblong shapes in cross section.
3. The heat exchanger of claim 2, wherein:
- each tube has opposite ends, each opposite end defining a substantially circular opening.
4. The heat exchanger of claim 3, wherein:
- each tube includes transition sections extending between the substantially circular openings and the portion of each tube having an oblong shape in cross section.
5. The heat exchanger of claim 4, wherein:
- each tube includes an elongated central portion having an oblong cross sectional shape.
6. The heat exchanger of claim 5, wherein:
- the elongated central portion of each tube includes a pair of generally planar side wall portions that are spaced apart, and a pair of curved sidewall end portions interconnecting the generally planar side wall portions.
7. The heat exchanger of claim 6, wherein:
- the generally planar side wall portions have a substantially uniform thickness.
8. The heat exchanger of claim 7, wherein:
- at least a portion of each generally planar side wall portion includes a plurality of raised portions forming protrusions on outer surfaces of each generally planar side wall portion.
9. The heat exchanger of claim 8, wherein:
- the protrusions comprise elongated ridges extending along the tubes.
10. The heat exchanger of claim 8, wherein:
- the protrusions comprise a plurality of generally circular bulges.
11. The heat exchanger of claim 1, wherein:
- the at least one tube comprises sheet metal having a substantially uniform thickness.
12. A tube assembly for a shell and tube heat exchanger, the tube assembly comprising:
- first and second end plates having a plurality of generally circular openings therethrough;
- a plurality of tubes extending between the first and second end plates, each tube having opposite end portions with outer surfaces that have a generally circular cross sectional shape, wherein the opposite end portions are received in the openings of the first and second end plates and being connected thereto; and wherein:
- the tubes have flattened central portions forming fluid passageways having oblong cross sectional shapes to thereby provide improved heat transfer.
13. The tube assembly of claim 12, wherein:
- the flattened central portions of each tube includes a pair of spaced apart side wall portions that are generally planar.
14. The tube assembly of claim 13, wherein:
- each tube includes curved side wall portions extending between and interconnecting the generally planar side wall portions.
15. The tube assembly of claim 13, wherein:
- the generally planar side wall portions include a plurality of raised portions forming protrusions on outer surfaces of each generally planar side wall portion.
16. The heat exchanger of claim 15, wherein:
- the protrusions comprise elongated ridges extending along the tubes.
17. The heat exchanger of claim 15, wherein:
- the protrusions comprise a plurality of generally circular bulges.
18. A tube for shell and tube heat exchangers, the tube comprising:
- an elongated tubular structure having spaced apart inner and outer side walls that are generally C-shaped in cross section, wherein the inner and outer side walls are interconnected by transverse end wall portions to form an internal passageway that is generally C-shaped.
19. The tube of claim 18, wherein:
- the inner and outer side walls define outer surfaces that are generally cylindrical in shape.
20. The tube of claim 18, wherein:
- the tube comprises sheet metal having elongated opposite edge portions that are interconnected to form a tube.
21. The tube of claim 20, wherein:
- the opposite edge portions are interconnected by folds to form a first transverse end wall portion.
22. The tube of claim 21, wherein:
- the tube comprises a single piece of sheet metal that is deformed to define a second transverse end wall portion.
Type: Application
Filed: Nov 20, 2013
Publication Date: Jun 19, 2014
Applicant: Whirlpool Corporation (Benton Harbor, MI)
Inventors: NIHAT O. CUR (St. Joseph, MI), NORMAN G. BEATY (Smyrna, TN)
Application Number: 14/084,671
International Classification: F28D 3/02 (20060101);