HEAT EXCHANGER DRIP TUBE
A drip tube has a generally horizontal section, a generally vertical section and a drip loop connecting the sections. The drip loop is positioned so that its exterior surface is lower than the exterior surfaces of the generally horizontal section and the generally vertical section at the points where they meet the drip loop to provide a location where water may drip.
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This application claims priority from U.S. Provisional Application No. 61/127,513, filed on May 14, 2008 and entitled “Heat Exchanger Drip Tube.”
BACKGROUNDAdvances in microchannel heat exchanger technology have demonstrated its advantages over the previously more conventional round-tube plate-fin type heat exchanger. Some of the benefits provided by microchannel heat exchangers include a reduction in the amount of refrigerant required for operation, more efficient heat transfer, and a reduced footprint. Microchannel heat exchangers, once used primarily in automotive applications, are now also finding use in residential and commercial air conditioning and refrigeration applications. Microchannel heat exchangers generally use all aluminum coils. In many applications, however, refrigerant enters and leaves the coils via copper tubes. A heat exchange system with aluminum and copper surfaces may run into problems with galvanic corrosion.
Galvanic corrosion occurs when two dissimilar metals make contact with one another in the presence of an electrolyte thereby forming a galvanic couple. The more noble metal (higher on the galvanic series) provides the surface area for the reduction reaction and the less noble metal (lower on the galvanic series) corrodes in an oxidation process. The oxidation occurs in the greatest amount at the interface of the two metals but may also occur at some distance away from the actual interface. In coastal regions, the most common electrolyte is salt water in the air. A fine salt water mist may be blown inland for up to fifty miles from the coast. Sulfur dioxide from industrial pollution also creates an electrolyte when it combines with moisture in the air.
If the two dissimilar metals in a heat exchanger are physically separated from one another, no interface exists for corrosion to occur. However, water containing particles of copper may come into contact with aluminum surfaces of the heat exchanger and form a galvanic couple. In some residential and commercial refrigeration systems, for example, the condenser section(s) of the heat exchangers used in vapor compression refrigeration are located outdoors (e.g., outside the residence, on the rooftops of commercial buildings). These condensers can be exposed to rain, snow, sleet, and salt. The water or moisture present in the outdoor environment has the potential to carry copper particles into contact with aluminum surfaces of the condenser such as the coils or the manifolds. Galvanic corrosion can occur in the areas where copper and aluminum make contact.
SUMMARYExemplary embodiments of the invention include a system having a heat exchanger manifold and a drip tube in fluid communication with the manifold. The drip tube includes a generally horizontal section, a generally vertical section, and a drip loop connecting the horizontal and vertical sections. The horizontal section, vertical section, and drip loop each have an exterior surface. A portion of the drip loop exterior surface is positioned so that it is lower than the exterior surfaces of the horizontal and vertical sections where the horizontal and vertical sections meet the drip loop.
A further embodiment of the present invention includes a method for protecting aluminum surfaces of a heat exchanger. The method includes shaping a drip tube having a generally horizontal section, a generally vertical section, and a drip loop connection the horizontal and vertical sections. The drip tube is shaped so that an exterior surface of the drip loop is positioned lower than the exterior surfaces of the horizontal and vertical sections where the horizontal and vertical sections meet the drip loop. The method also includes connecting the horizontal section of the drip tube to a heat exchanger manifold and connecting the vertical section of the drip tube to a refrigerant line.
Illustrated in
Illustrated in
Attached to manifold 12 are inlet and outlet tubes. In the embodiment shown in
Drip tube 18 includes horizontal section 20, drip loop 22, and vertical section 24. As illustrated in
As illustrated by
In one exemplary embodiment of drip tube 18, drip tube 18 has an outer diameter of about 9.5 mm. The wall thickness of drip tube 18 is about 0.7 mm. Vertical section 24 of drip tube 18 is about 42 mm in length. The straight sloped portion of drip loop 22 (the portion between horizontal section 20 and the sharp bend in drip loop 22) is about 19 mm in length. Drip loop 22 slopes downward from horizontal section 20 at an angle of about 19° and the U-bend of drip loop 22 traverses an arc of about 109°. The distance between the centerpoint of manifold 12 and the centerpoint of vertical section 24 is about 76 mm. Horizontal section 20 connects with manifold 12 about 40 mm above heat exchanger bottom surface 30. The dimensions of other embodiments of drip tube 18 may vary. For example, the outer diameter of drip tube 18 may be between about 2.0 mm and about 25.4 mm. Wall thickness may be between about 0.1 mm to about 4 mm. The angles and lengths of the different portions of drip tube 18 may be adapted to the particular needs of the heat exchanger manifold and refrigerant lines. However, all embodiments will be configured so that the drip loop has an exterior surface lower than the exterior surfaces of the horizontal and vertical sections where they connect to the drip loop.
Water and moisture (from rain, snow, or condensation) that collect in heat exchanger section 10 may accumulate on exterior surfaces of refrigerant lines in fluid communication with drip tube 18. Water may travel down the exterior surfaces of the refrigerant lines towards the heat exchanger manifold 12. As refrigerant lines are often made of copper, this water may collect particles of copper as it travels along the exterior surfaces of the refrigerant lines. In a heat exchanger without a drip tube, the copper-containing water may travel to the area where the refrigerant line (inlet/outlet) connects with the aluminum heat exchanger manifold 12. The copper and aluminum may form a galvanic couple and galvanic corrosion may occur at or near the area where both copper and aluminum are present.
The drip tube 18 prevents copper-containing water from reaching the manifold 12. Water travels down the exterior surface of a refrigerant line and vertical section 24 of drip tube 18. The water then reaches drip loop 22 and continues to the lowest portion of bottom exterior surface 28. The water will drip from the lowest portion of bottom exterior surface 28 rather than continue along drip loop 22 to horizontal surface 20 and eventually to manifold 12. The water would need to travel “uphill” to reach horizontal surface 20 from drip loop 22. Gravity will cause the water to form droplets and drip from the lowest portion of bottom exterior surface 28 before it can reach horizontal surface 20.
While
Water drips from bottom exterior surface 28 of drip loop 22 onto heat exchanger bottom surface 30. In exemplary heat exchanger embodiments, bottom surface 30 directs collected water away from manifold 12. Bottom surface 30 may be sloped to facilitate collection of water in areas of heat exchanger section 10 away from manifold 12 where it is allowed to evaporate or drain out of heat exchanger section 10.
One embodiment of a connection between drip tube 18 and manifold 12 is illustrated in
Manifold 12 and belled section are typically similar metals in this construction. Belled section 26 and horizontal section 20 of drip tube 18 are typically dissimilar metals. To prevent galvanic corrosion between belled section 26 and drip tube 18, one or more barrier layers 34 may be employed. Barrier layer 34 is positioned around the joining area of belled section 26 and drip tube 18 to protect the area where dissimilar metals contact one another from water and oxygen, thereby preventing or reducing the opportunity for galvanic corrosion. Barrier layer 34 is generally placed around belled section 26 or drip tube 18 after connection with manifold 12. Barrier layer 34 may be a shrink wrap that seals around belled section 26 when heat is applied to the shrink wrap. Barrier layer 34 may be any material appropriate to protect metals from water and oxygen, such as rubber, neoprene, nylon, or latex.
While the invention has been described with reference to an exemplary embodiment(s), it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment(s) disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.
Claims
1. A system comprising:
- a heat exchanger manifold; and
- a drip tube in fluid communication with the heat exchanger manifold, the drip tube comprising: a generally horizontal section having an exterior surface; a generally vertical section having an exterior surface; and a drip loop having an exterior surface and connecting the horizontal section and the vertical section, wherein a lowest portion of the drip loop exterior surface is positioned lower than the horizontal section exterior surface where the horizontal section and drip loop meet and lower than the vertical section exterior surface where the vertical section and drip loop meet.
2. The system of claim 1, wherein the heat exchanger manifold and the drip tube are similar metals.
3. The system of claim 1, wherein the heat exchanger manifold and the drip tube are dissimilar metals.
4. The system of claim 3, wherein the heat exchanger manifold is aluminum and the drip tube is copper.
5. The system of claim 1, wherein the drip tube is an inlet or an outlet for the heat exchanger manifold.
6. The system of claim 1, wherein the horizontal section is generally perpendicular to the heat exchanger manifold.
7. The system of claim 1, wherein the horizontal section is connected to the heat exchanger manifold.
8. The system of claim 1 further comprising a belled section, wherein the belled section connects the heat exchanger manifold and the drip tube.
9. The system of claim 1 further comprising a barrier layer, wherein the barrier layer surrounds a portion of the heat exchanger manifold and a portion of the drip tube.
10. The system of claim 8, further comprising a barrier layer, wherein the barrier layer surrounds a portion of the belled section and a portion of the drip tube.
11. A heat exchanger section comprising:
- first and second manifolds;
- a plurality of flow paths extending between the first and second manifolds; and
- at least one drip tube in fluid communication with at least one manifold, the drip tube comprising: a generally horizontal section having an exterior surface; a generally vertical section having an exterior surface; and a drip loop having an exterior surface and connecting the horizontal section and the vertical section, wherein a lowest portion of the drip loop exterior surface is positioned lower than the horizontal section exterior surface where the horizontal section and drip loop meet and lower than the vertical section exterior surface where the vertical section and drip loop meet.
12. The heat exchanger section of claim 11, wherein the at least one drip tube and the at least one manifold in fluid communication with the at least one drip tube are dissimilar metals.
13. The heat exchanger section of claim 12, wherein the at least one drip tube is copper and the at least one manifold in fluid communication with the at least one drip tube is aluminum.
14. The heat exchanger section of claim 11, wherein the at least one drip tube is an inlet or an outlet for the at least one manifold in fluid communication with the at least one drip tube.
15. The heat exchanger section of claim 11, wherein the horizontal section is connected to the at least one manifold in fluid communication with the at least one drip tube.
16. The heat exchanger section of claim 11 further comprising a belled section, wherein the belled section connects the at least one drip tube and the at least one manifold in fluid communication with the at least one drip tube.
17. The heat exchanger section of claim 11 further comprising a barrier layer, wherein the barrier layer surrounds a portion of the at least one drip tube and a portion of the at least one manifold in fluid communication with the at least one drip tube.
18. The heat exchanger section of claim 11 further comprising a barrier layer, wherein the barrier layer surrounds a portion of the belled section and a portion of the at least one drip tube.
19. A method for protecting aluminum surfaces of a heat exchanger, the method comprising:
- shaping a drip tube comprising a generally horizontal section, a generally vertical section, and a drip loop connecting the horizontal and vertical sections, wherein the drip tube is shaped so that an exterior surface of the drip loop is positioned lower than an exterior surface of the horizontal section where the horizontal section and drip loop meet and lower than an exterior surface of the vertical section where the vertical section and drip loop meet;
- connecting the horizontal section of the drip tube to a heat exchanger manifold; and
- connecting the vertical section of the drip tube to a refrigerant line.
20. The method of claim 19 further comprising providing a barrier layer to a portion of the drip tube and a portion of the heat exchanger manifold.
21. The method of claim 19, wherein the step of connecting the horizontal section of the drip tube to a heat exchanger manifold further comprises:
- connecting a first end of a belled section to the heat exchanger manifold; and
- connecting the horizontal section of the drip tube to a second end of the belled section.
22. The method of claim 21 further comprising providing a barrier layer to a portion of the drip tube and a portion of the belled section.
Type: Application
Filed: May 14, 2009
Publication Date: Feb 24, 2011
Applicant: CARRIER CORPORATION (Farmington, CT)
Inventors: Andrew E. Karl (Greenwood, IN), Ron A. Wilson (Greenwood, IN)
Application Number: 12/922,389
International Classification: F28D 5/02 (20060101); F28F 9/02 (20060101); B21D 53/02 (20060101);