Patent Application
20130283585
Not applicable.
Not applicable.
Not applicable.
Microchannel tubes of heating, ventilation, and air conditioning (HVAC) heat exchangers may become damaged. Some microchannel tubes comprise materials that are not easily repaired using conventional techniques. Some microchannel tubes comprise features of such diminutive size that repair of such features using conventional techniques may not be predictably attainable.
In some embodiments, a method of repairing a microchannel heat exchanger is provided. The method may comprise identifying a damaged region of a microchannel tube, providing sealant to at least one of the microchannel tube and a patch, and disposing the patch relative to the microchannel tube so that the sealant forms a fluid tight boundary between the microchannel tube and the patch, wherein the fluid tight boundary circumscribes the damaged region.
In other embodiments, a method of repairing a refrigeration conduit is provided. The method may comprise identifying a damaged region of the refrigeration conduit and locating a patch configured to substantially cover and at least partially overlap the damaged region boundary an offset distance from the refrigeration conduit while the space between the patch and the damaged region boundary is filled with sealant.
In other embodiments, a repair kit for repairing a damaged microchannel tube is provided. The repair kit may comprise a patch configured to at least cover a damaged region of the microchannel tube and a sealant configured for filling a space between the patch and the microchannel tube.
For a more complete understanding of the present disclosure and the advantages thereof, reference is now made to the following brief description, taken in connection with the accompanying drawings and detailed description, wherein like reference numerals represent like parts.
In some cases, a microchannel tube of an HVAC heat exchanger may be damaged so that one or more microchannels in the microchannel tube are undesirably opened to the environment. In some cases, the damage may allow refrigerant to escape from an otherwise closed loop refrigerant circuit of an HVAC system. In some cases, repair of the damaged microchannel tube may be attempted by utilizing a brazing process in which operating temperatures may be as high as 1100-1200° F. At such high temperatures, there is a possibility of further damaging the microchannel tube and a highly skilled technician is needed to attempt the repair. In other cases, repair of the damaged microchannel tube may be attempted by utilizing a vacuum-epoxy process. In some cases, epoxy may be applied to the damaged portion of the tube comprising an opening to the environment and a vacuum pressure may be applied to the damaged microchannel tube to draw some epoxy into the damaged microchannel tube via the opening. Reliability of repairs using the vacuum-epoxy process is unpredictable because it is difficult to meter and/or monitor the amount of epoxy drawn into the microchannel tube. As a result, the repair may fail after thermal cycling of the microchannel tube and/or pressure cycling of the microchannel tube. Further, if residual compressor oil within the microchannel tube is not fully removed, successful bonding between the microchannel tube and the epoxy may be prevented. Accordingly, this disclosure provides systems and methods for repairing a damaged microchannel HVAC heat exchanger tube with greater reliability and lower skill level.
Referring now to
The microchannel heat exchanger 114 further comprises a divided header 306 and an undivided header 308. The divided header 306 is generally a tubular structure comprising an upper volume 310 and a lower volume 312. The upper volume 310 and the lower volume 312 are separated and prevented from directly communicating fluid between each other by a divider 314 disposed within the divided header 306. In alternative embodiments, the divided header 306 may be replaced by two physically separate headers. In this embodiment, the divider 314 is generally located a divider vertical offset distance 316 from the lower end 302. The undivided header 308 comprises a substantially similar tubular structure to that of the divided header 306, but the undivided header 308 comprises no internal structure analogous to the divider 314. Accordingly, the undivided header 308 comprises a substantially vertically continuous volume 318. The outdoor heat exchanger 114 further comprises a plurality of microchannel tubes 320 that extend horizontally between the divided header 306 and the undivided header 308. The microchannel tubes 320 join the divided header 306 and the undivided header 308 in fluid communication with each other.
Referring now to
Referring back to
Under normal and/or ideal operating conditions, the microchannel heat exchanger 114 may be generally described as comprising three refrigerant characteristic regions: a hot gas region 342, a two-phase (liquid and vapor) region 344, and a subcooled liquid region 346. Because, under ideal and/or normal conditions, refrigerant is introduced into the outdoor heat exchanger 114 as hot gas, the hot gas will normally fill the upper volume 310 of the divided header 306 and travel in parallel paths through the supply microchannel tubes 320′. As the hot gas is cooled by ambient outdoor air being forced into contact with the outdoor heat exchanger 114, some of the hot gas may cool and condense to liquid form. Most generally, such initial condensation and conversion to liquid may occur in the two-phase region 344. When the condensed liquid reaches the undivided header 308, the liquid refrigerant may fall into the continuous volume 318 of the undivided header and become distributed into the various return microchannel tubes 320″ before exiting the microchannel heat exchanger 114.
Referring now to
Referring now to
Referring now to
The repair kit 700 may further comprise an applicator tool 706, a cleaning pad 708, sandpaper 710, and a tube brush 712. In some embodiments, the applicator tool 706 may comprise a wooden stick such as, but not limited to, a tongue depressor, popsicle stick, or the like. In some embodiments, the cleaning pad 708 may comprise a cloth and/or paper material pre-moistened with a cleaning agent, such as, but not limited to, rubbing alcohol. The sandpaper 710 may comprise abrasives selected for abrading metals, such as abrasives suitable for abrading aluminum and/or copper. The tube brush 712 may comprise metal wire bristles, such as, but not limited to, steel or brass bristles. In some embodiments, one or more of the elements of the repair kit 700 may be utilized to repair a damaged microchannel heat exchanger such as damaged microchannel heat exchanger 600.
Referring now to
At block 804, the method 800 may continue by selectively removing damaged fins to create adequate access to a damaged microchannel tube, such as damaged microchannel tube 320″′. In some cases, pliers, a knife, and/or a razor blade box cutter may be used to separate damaged and/or adjacent fins 324 from the vicinity of the location of the damage to the microchannel tube. In some embodiments, approximately one inch of fin space centered left-right on the damaged portion of the microchannel tube may be removed/cleared on each of the upper and lower sides of the microchannel tube. In some cases, removing fins that are adjacent but not damaged may provide improved access to a damaged microchannel tube.
Referring now to
Referring back to
At block 808, the method may continue by applying a patch 704 and/or sealant 702 to the damaged microchannel tube. In some embodiments, sealant 702 may be applied to one or more of the surfaces of the damaged microchannel tube (see
With sufficient and suitable placement of sealant 702 on at least one of the damaged microchannel tube and a patch 704, the patch 704 may be applied to the damaged microchannel tube. In some embodiments, the patch 704 may be located so that a primary portion of the damage to the damaged microchannel tube is substantially centered left-right relative to the longitudinal length of the patch 704 (as opposed to circumferentially around a microchannel tube). After applying the patch 704 to the damaged microchannel tube, the method may progress to block 810.
At block 810, the method may progress by selectively applying heat and/or pressure. In some embodiments, pressure may be applied to the patch 704 using pliers 714 (see
In some embodiments, a patch 704 may comprise a solid sheet of material, such as aluminum, that is folded or bent along a middle portion into one or more opposing surfaces. In some embodiments, a patch 704 may be about 0.02 inches to about 0.03 inches thick, and may be formed form a flat sheet of material that is a rectangle of about 1 inch by about 2 inches. In some embodiments, the patch 704 may be dimensioned to allow about 0.005 to about 0.01 inches of space for receiving sealant 702 between the patch 704 and a damaged microchannel tube. In some embodiments, multiple patches 704 may be used and/or joined to each other and/or to a same damaged portion of a microchannel tube. In some embodiments, the sealant 702 may be cured using a temperature greater than a normal operating temperature of the damaged microchannel tube.
In some embodiments, the patch 704 may be made of a same material as the damaged microchannel tube. For example, the patch 704 and the damaged microchannel tube may both be made of aluminum or both be made of copper. In some cases, constructing the patch 704 out of the same material as the damaged microchannel tube ensures that the thermal expansion coefficients are the same thereby helping to prevent formation of leaks subsequent to repair due to thermal expansion. In some embodiments, the patch 704 may comprise a V-shape. In some embodiments, a larger patch 704 and/or larger surface area of patch-microchannel tube may be supplied sealant 702 so that greater HVAC system operating pressures may be withstood by the above-described repair. In some embodiments, the sealant 702 may comprise an epoxy capable of withstanding at least 3000 pounds per square inch (psi) of pressure, which may be more than sufficient in HVAC systems that use either R-410A refrigerant and operate at approximately 700 psi or HVAC systems that use carbon dioxide based refrigerant at pressures of about 1800 psi.
Referring now to
This disclosure further contemplates that a kit substantially similar to kit 700 and a method substantially similar to method 800 may be utilized to repair damage located substantially at a joint and/or interface between a microchannel tube and a header, damage located on a header, damage on a refrigerant tube that does not comprise microchannels, and/or any other refrigerant conduit. Of course, as described above, the patch may comprise a material having a coefficient of thermal expansion substantially similar to the damaged material and a kit may comprise a plurality of patches comprising different materials. In some cases, a repair person may select a patch from a kit based on the material that is damaged and may further trim or otherwise shape and/or customize the patch.
At least one embodiment is disclosed and variations, combinations, and/or modifications of the embodiment(s) and/or features of the embodiment(s) made by a person having ordinary skill in the art are within the scope of the disclosure. Alternative embodiments that result from combining, integrating, and/or omitting features of the embodiment(s) are also within the scope of the disclosure. Where numerical ranges or limitations are expressly stated, such express ranges or limitations should be understood to include iterative ranges or limitations of like magnitude falling within the expressly stated ranges or limitations (e.g., from about 1 to about 10 includes, 2, 3, 4, etc.; greater than 0.10 includes 0.11, 0.12, 0.13, etc.). For example, whenever a numerical range with a lower limit, RI, and an upper limit, Ru, is disclosed, any number falling within the range is specifically disclosed. In particular, the following numbers within the range are specifically disclosed: R=RI+k*(Ru−RI), wherein k is a variable ranging from 1 percent to 100 percent with a 1 percent increment, i.e., k is 1 percent, 2 percent, 3 percent, 4 percent, 5 percent, . . . 50 percent, 51 percent, 52 percent, . . . , 95 percent, 96 percent, 97 percent, 98 percent, 99 percent, or 100 percent. Moreover, any numerical range defined by two R numbers as defined in the above is also specifically disclosed. Use of the term “optionally” with respect to any element of a claim means that the element is required, or alternatively, the element is not required, both alternatives being within the scope of the claim. Use of broader terms such as comprises, includes, and having should be understood to provide support for narrower terms such as consisting of, consisting essentially of, and comprised substantially of. Accordingly, the scope of protection is not limited by the description set out above but is defined by the claims that follow, that scope including all equivalents of the subject matter of the claims. Each and every claim is incorporated as further disclosure into the specification and the claims are embodiment(s) of the present invention.
