3-D dimpled heat exchanger
A heat exchanger apparatus comprising a frame, a tube coupled to the frame, and turbulating structure disposed within the tube and extending into an inner hollow space thereof for promoting turbulent fluid flow within the tube. The turbulating structure comprises elements located arcuately around an inner periphery of the tube at approximately 120° increments. A method of manufacturing and a heating system is also provided.
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The present invention is directed, in general, to heat exchange apparatus and, more specifically, to a design for heat exchanger tubes.
BACKGROUND OF THE INVENTIONHeat exchange tubes are used to transfer heat between two media by using, for example, a so-called “tube-in-tube” design or a “shell-in-tube” design. In a “tube-in-tube” design the fluid product to be heated or cooled flows through a product tube or series of product tubes and the heating or cooling media flows through an outer media tube or series of media tubes usually in a countercurrent fashion with respect to the product flow. Thus, heat is transferred between the media flowing in the inner space between the walls of the media and product tubes and the fluid product flowing through the product tubes or tubes. In a “shell-in-tube” design the product tubes are disposed within a container referred to as a shell and within which the heating or cooling media flows over all of the product tubes from an inlet to an outlet thereof to transfer heat between the media and the product.
To improve heat transfer efficiency the product tubes in either a tube-in-tube design or shell-in-tube design have included turbulating structure of various configurations to promote flow within the tube at a Reynolds number between 8,000 and 10,000, approaching turbulent flow. Generally stated, turbulent flow increases the heat transfer efficiency of the tube by distributing the core fluid flowing therethrough across the entire diameter of the tube and not in streams flowing generally parallel to the axis of the tube in substantially laminar flow. Since a higher rate of heat transfer occurs adjacent the wall of the product tube, ideally a flow pattern is created which eliminates a temperature gradient within the fluid at any cross section taken through the tube.
One method of inducing turbulent flow that has been used with some success is the formation of paired dimples in an outer surface of the heat exchange tube. In many cases, the pairs of dimples are diametrically opposite on the surface of the tube. In some cases, the dimples are co-linear along a line parallel to the axis of the tube. In other cases, successive dimple pairs are non-co-linear, being positioned axially by a set number of degrees, e.g., 30° or 40°, from the previous pair so as to induce an additional rotational effect to the fluid flow.
Nonetheless, there is continual emphasis in most industries to make ever more efficient units in ever more restricted space. This is particularly true in the heating and air conditioning industry where reducing the heat exchanger cabinet size for a given tonnage is always a design objective. As a result, conventional approaches to increasing efficiency and therefore increasing Reynolds number are limited by the geometry of the system.
Accordingly, what is needed in the art is an improved design for turbulating mechanisms in heat exchanger tubes to improve efficiency within a given tube length.
SUMMARY OF THE INVENTIONTo address the above-discussed deficiencies of the prior art, the present invention provides a heat exchanger apparatus comprising a frame, a tube coupled to the frame, and turbulating structure disposed within the tube and extending into an inner hollow space thereof for promoting turbulent fluid flow within the tube. The turbulating structure comprises elements located arcuately around an inner periphery of the tube at approximately 120° increments. A method of manufacturing and a heating system is also provided.
The foregoing has outlined preferred and alternative features of the present invention so that those skilled in the art may better understand the detailed description of the invention that follows. Additional features of the invention will be described hereinafter that form the subject of the claims of the invention. Those skilled in the art should appreciate that they can readily use the disclosed conception and specific embodiment as a basis for designing or modifying other structures for carrying out the same purposes of the present invention. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the invention.
BRIEF DESCRIPTION OF THE DRAWINGSFor a more complete understanding of the present invention, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:
FIGS. 6A--6C illustrate sectional views of the heat exchanger tube of
Referring initially to
Referring now to
As an example, a reference radius 215 may be drawn from the centerline 112 through a center 221a-221c of one 225a of the dimples 225a-225c. The significance of this reference radius 215 will be discussed below. In a typical heat exchanger tube 100 formed from 2 inch tubing and using a 1 inch diameter hemispherical tool end, the dimple depth d can be adjusted up to a maximum dimple depth d of about 0.867″. The dimple depth d and tubing size can be adjusted to achieve a desired Reynolds Number. In a preferred embodiment, internal area of ⅝-inch tubing at the dimples may be sized to produce a Reynolds Number from about 8,000 to about 10,000 with about a 400° F. to about a 450° F. flue temperature. In a like manner, using ½-inch tubing produces a Reynolds Number of about 12,000 under the same conditions. It should be noted that tubing of any appropriate diameter and wall thickness can be used. Also, the dimple depth can be controlled down to the limit wherein a set of dimples touch at the centerline within the tubing. In one embodiment, the first dimple trio 122 may have a first dimple depth and the second dimple trio 123 may have a second dimple depth wherein the second dimple depth is not equal to the first dimple depth. One who is of skill in the art will recognize that this variation of dimple depth may be applied to vary from one set of dimples to the next all along the tubing. Additionally, the diameter of the hemispherical tool end can be increased or decreased in order to change the size of the dimples and correspondingly the Reynolds number. In a preferred embodiment, the heat exchanger tube 100 comprises a path 230 for off-cycle or off-season condensate.
Referring now to
Referring now to
Referring now to
Referring now to
Referring now to
Referring now to
Referring now to
Referring now to
Referring now to
Specifically, the dimpled third section 1130 of the heat exchanger tube 1100 of
Referring now to
Referring now to
Thus, a heat exchanger apparatus has been described comprising a heat exchanger tube having turbulating structure in the form of trios of elements disposed within the heat exchanger tube. The advantages of the present invention include reducing residual stress within the heat exchanger tube while minimizing overall cabinet size and increased Reynolds number for flue products. The resultant increased pressure drop increases overall efficiency accordingly. An unobstructed path is also provided for the drain of condensate during off-season and off cycle operation.
Although the present invention has been described in detail, those skilled in the art should understand that they can make various changes, substitutions and alterations herein without departing from the spirit and scope of the invention in its broadest form.
Claims
1. A heat exchanger apparatus, comprising:
- a frame;
- a tube coupled to said frame; and
- turbulating structure disposed within said tube and extending into an inner hollow space thereof for promoting turbulent fluid flow within said tube, said turbulating structure comprising elements located arcuately around an inner periphery of said tube at approximately 120° increments.
2. The apparatus of claim 1 wherein said elements comprise dimples formed in said tube.
3. The apparatus of claim 1 wherein said tube has a longitudinal axis and wherein said turbulating structure comprises a first dimple trio formed in said tube and having a first trio of centers, said first trio of centers substantially coplanar with a plane normal to said longitudinal axis.
4. The apparatus of claim 3 wherein said turbulating structure comprises a second dimple trio spaced apart from said first dimple trio along said longitudinal axis, and wherein said tube has:
- a first reference radius from said longitudinal axis and through a center of one of said elements of said first dimple trio; and
- a second reference radius from said longitudinal axis and through a center of one of said elements of said second dimple trio; and wherein said first and second reference radii are coplanar.
5. The apparatus of claim 4 wherein said first dimple trio has a first dimple depth and said second dimple trio has a second dimple depth not equal to said first dimple depth.
6. The apparatus of claim 3 wherein said turbulating structure comprises a second dimple trio spaced apart from said first dimple trio along said longitudinal axis, and wherein said tube has:
- a first reference radius from said longitudinal axis and through a center of one of said elements of said first dimple trio;
- a second reference radius from said longitudinal axis and through a center of one of said elements of said second dimple trio; and wherein said first and second reference radii are non-coplanar.
7. The apparatus of claim 6 wherein said second reference radius arcuately differs from said first reference radius by an angle between about ±5° and about ±30°.
8. The apparatus of claim 7 wherein said turbulating structure comprises a third dimple trio spaced apart from said second dimple trio along said longitudinal axis, and wherein said tube has a third reference radius from said longitudinal axis and through a one of said elements of said third dimple trio wherein said third reference radius arcuately differs from said second reference radius by an angle between about ±5° and about ±30°.
9. The apparatus of claim 1 wherein said turbulating structure comprise said dimples including smoothly curving surfaces in said tube.
10. The apparatus of claim 1 wherein said tube has a weld parallel said longitudinal axis.
11. The apparatus of claim 10 wherein a one of said elements is diametrically opposed said weld.
12. The apparatus of claim 1 wherein said tube has a path for off-cycle or off-season condensate.
13. A method of manufacturing a heat exchanger apparatus, comprising:
- providing a frame;
- coupling a tube to said frame; and
- disposing turbulating structure within said tube and extending into an inner hollow space thereof for promoting turbulent fluid flow within said tube, said turbulating structure comprising elements located arcuately around an inner periphery of said tube at approximately 120° increments.
14. The method of claim 13 wherein disposing includes forming dimples in said tube.
15. The method of claim 13 wherein said tube has a longitudinal axis and wherein disposing includes forming a first dimple trio in said tube, said first dimple trio substantially coplanar with a plane normal to said longitudinal axis.
16. The method of claim 15 wherein disposing includes forming a second dimple trio spaced apart from said first dimple trio along said longitudinal axis, and wherein said tube has:
- a first reference radius from said longitudinal axis and through a one of said elements of said first dimple trio; and
- a second reference radius from said longitudinal axis and through a one of said elements of said second dimple trio; and wherein said first and second reference radii are coplanar.
17. The method of claim 16 wherein disposing includes forming said first dimple trio having a first dimple depth and forming said second dimple trio having a second dimple depth not equal to said first dimple depth.
18. The method of claim 15 wherein disposing includes forming a second dimple trio spaced apart from said first dimple trio along said longitudinal axis, and wherein said tube has:
- a first reference radius from said longitudinal axis and through a one of said elements of said first dimple trio; and
- a second reference radius from said longitudinal axis and through a one of said elements of said second dimple trio; and wherein said first and second reference radii are non-coplanar.
19. The method of claim 16 wherein disposing includes forming said second dimple such that said second reference radius arcuately differs from said first reference radius by an angle between about ±5° and about ±30°.
20. The method of claim 19 wherein disposing includes forming a third dimple trio spaced apart from said second dimple trio along said longitudinal axis, and wherein said tube has a third reference radius from said longitudinal axis and through a one of said elements of said third dimple trio wherein said third reference radius arcuately differs from said second reference radius by an angle between about ±5° and about ±30°.
21. The method of claim 13 wherein disposing includes forming said dimples including smoothly curving surfaces in said tube.
22. The method of claim 13 wherein coupling includes coupling a tube having a weld parallel said longitudinal axis.
23. The method of claim 22 wherein coupling includes coupling wherein a one of said elements is diametrically opposed said weld.
24. A heating system, comprising:
- a cabinet;
- a frame coupled to said cabinet;
- a heat exchanger having at least one tube coupled to said frame; and
- turbulating structure disposed within said tube and extending into an inner hollow space thereof for promoting turbulent fluid flow within said tube, said turbulating structure comprising elements located arcuately around an inner periphery of said tube at approximately 120° increments.
25. The heating system of claim 24 wherein said elements comprise dimples formed in said tube.
26. The heating system of claim 24 wherein said tube has a longitudinal axis and wherein said turbulating structure comprises a first dimple trio formed in said tube, said first dimple trio substantially coplanar with a plane normal to said longitudinal axis.
27. The heating system of claim 26 wherein said turbulating structure comprises a second dimple trio spaced apart from said first dimple trio along said longitudinal axis, and wherein said tube has:
- a first reference radius from said longitudinal axis and through a one of said elements of said first dimple trio;
- a second reference radius from said longitudinal axis and through a one of said elements of said second dimple trio; and wherein said first and second reference radii are coplanar.
28. The heating system of claim 27 wherein said first dimple trio has a first dimple depth and said second dimple trio has a second dimple depth not equal to said first dimple depth.
29. The heating system of claim 26 wherein said turbulating structure comprises a second dimple trio spaced apart from said first dimple trio along said longitudinal axis, and wherein said tube has:
- a first reference radius from said longitudinal axis and through a one of said elements of said first dimple trio;
- a second reference radius from said longitudinal axis and through a one of said elements of said second dimple trio; and wherein said first and second reference radii are non-coplanar.
30. The heating system of claim 29 wherein said second reference radius arcuately differs from said first reference radius by about +30°.
31. The heating system of claim 30 wherein said turbulating structure comprises a third dimple trio spaced apart from said second dimple trio along said longitudinal axis, and wherein said tube has a third reference radius from said longitudinal axis and through a one of said elements of said third dimple trio wherein said third reference radius arcuately differs from said second reference radius by about −30°.
32. The heating system of claim 24 wherein said turbulating structure comprises said dimples including curving surfaces in said tube.
33. The heating system of claim 24 wherein said tube has a weld parallel said longitudinal axis.
34. The heating system of claim 33 wherein a one of said elements is diametrically opposed said weld.
Type: Application
Filed: Oct 24, 2005
Publication Date: Apr 26, 2007
Applicant: Lennox Manufacturing Inc. (Richardson, TX)
Inventors: Mark Beste (Grapevine, TX), David Wynnick (Frisco, TX)
Application Number: 11/256,783
International Classification: F28F 1/00 (20060101);