Patent Application
20190257595
The present invention generally relates to heat exchangers and, more particularly, to apparatus and methods for fabricating heat exchangers.
Plate-fin heat exchangers can be brazed to form a core that is a monolithic structure where the sandwiched layers include a top side plate, a hot fin, a tube sheet, a cold fin, and bottom plate. The core may also be welded around a perimeter of the core layers which is referred to as a “butter-pass weld”.
As an example, as shown in
However, the fabrication of plate-fin heat exchangers can include problems of distortion due to heat treatment, shrinkage during brazing, deformation due to “butter-passing”, as well as others.
As can be seen, there is a need for improved apparatus and methods to fabricate plate-fin heat exchangers.
In one aspect of the present invention, a heat exchanger core comprises a first fin passage; and a first frame surrounding a perimeter of the first fin passage; wherein the first frame includes a plurality of bars integrally configured to be removable from the first frame.
In another aspect of the present invention, a method of making a heat exchanger core comprises surrounding a first passage with a first frame; brazing the core; and after brazing, removing a side bar from the first frame to enable air to flow in or out of the first passage.
In a further aspect of the present invention, a method of making a heat exchanger core comprises surrounding a hot fin passage with a hot frame; surrounding a cold fin passage with a cold frame; brazing the core; after brazing, removing at least one of a support bar and a side bar from at least one of the hot and cold frames; after brazing, leaving a main bar as part of at least one of the hot and cold frames; after brazing, leaving the core devoid of a butter-pass weld.
These and other features, aspects and advantages of the present invention will become better understood with reference to the following drawings, description and claims.
The following detailed description is of the best currently contemplated modes of carrying out the invention. The description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the invention, since the scope of the invention is best defined by the appended claims.
Various inventive features are described below that can each be used independently of one another or in combination with other features. However, any single inventive feature may not address any of the problems discussed above or may only address one of the problems discussed above. Further, one or more of the problems discussed above may not be fully addressed by any of the features described below.
Broadly, the present invention provides apparatus and methods of fabricating heat exchangers while eliminating past problems relating to, among other things, shrinkage variation during brazing, deformation of the core from welding (i.e., butter-passing), distortion due to heat treatment, and collapsing of fin passages.
Generally, the present invention enables a heat exchanger core to be stacked quickly and simplifies alignment prior to brazing. The present invention provides the ability to withstand greater force from stacking and brazing, thus reducing gaps between fins and tube sheets, resulting in a stronger braze joint. The heat exchanger core can be easily cut to a consistent size, be ready for next assembly, and eliminates the need for additional welding preparation. In particular, the present invention eliminates the need to build up next assembly faying surfaces created from welding.
The heat exchanger core of the present invention can be fabricated with frame bars manufactured by extruded, machined, forged, 3D printed, casting, stamp or any other method. After brazing, the bars can be contoured by cutting off support material to expose finned passages. The frame bar materials could include aluminum, cooper, titanium, and nickel-based alloys.
In an exemplary embodiment of the present invention, as depicted in
The heat exchanger core 30 can generally be constructed in a stacked, plate fin design. A first or top side plate 36 may be on one side of the core 30 and a second or bottom side plate 37 may be on an opposite side of the core 30. Between the first and second side plates 36, 37, first or hot fin passages 31 may run perpendicular to second or cold fin passages 32. A tube sheet 33 can be interposed between the first and second fin passages 31, 32. A perimeter configuration of the tube sheet 33 can match a combined perimeter configuration of both first and second frames described below.
In embodiments, a first or hot frame 34 may frame or surround a perimeter of the first or hot passages 31. A second or cold frame 35, similar in design and construction to the first frame 34, may frame or surround a perimeter of the second or cold passages 32. A corner portion 38 of the core 30 may extend from a corner of the top plate 36, through the frames 34, 35, and to a corner of the bottom plate 37. The corner portion 38 may correspond to the corner portion 23 in
Although
In embodiments, the frame 40 may include, at a perimeter thereof, a pair of main bars 41a, b which are on a pair opposite sides of the perimeter. In embodiments, one or both of the main bars 41a, b are configured to permanently remain as part of the frame 40 and, thus, not removable from the frame 40. One or both of the main bars 41a, b can have a respective corner portion 41a-1, b-1. The corner portions 41a-1, b-1 may be disposed to correspond in location and configuration to the corner portion 38 depicted in
The frame 40, according to embodiments, may further include a pair of support bars 42a, b that are respectively paired with the main bars 41a, b. So paired, the support bars 42a, b may extend parallel to the main bars 41a, b. The support bars 42a, b may also be spaced apart from the main bars 41a, b whereby the support bars 42a, b can be disposed outside of the main bars 41a, b. In other words, the support bars 42a, b are further from a center area of the frame 40 than the main bars 41a, b.
With the support bars 42a, b spaced apart from the main bars 41a, b, a pair of slots 44a, b can be respectively formed between the support bars and the main bars. As described below, the slots 44a, b can provide for air passage.
According to embodiments, the frame 40 may further include a pair of side bars 43a, b disposed on another pair of opposite sides of the perimeter. In other words, the side bars 43a, b form one pair of opposite sides of the frame perimeter, and the main bars/support bars from another pair of opposite sides of the frame perimeter.
In embodiments, the frame 40 may be provided with one or more groove guides. In embodiments, a groove guide 45a, or 45b may be provided at one or both distal ends of the support bar 42a. Likewise, a groove guide 45c, or 45d may be provided at one or both distal ends of the support bar 42b. Similarly, groove guides 46a, b, c, d may be provided at one or both ends of the side bars 43a, b.
In embodiments, the frame 40 may be provided with one or more support tabs for alignment and extra support. In embodiments, a support tab 47a may be provided at one or both distal ends of the main bar 41a. Likewise, a support tab 47b may be provided at one or both distal ends of the main bar 41b.
As described below, one or more of the groove guides 45a, b, c, d and 46a, b, c, d can be used to guide a cut and then discard one or more of the support bars 42a, b and side bars 43a, b. Accordingly, one or more of the support bars 42a, b and/or one or more of the side bars 43a, b can be configured to be removable from the frame 40.
In embodiments, the side plate 50 may include a side or perimeter edge 51. At one or all corners thereof may be a corner edge 51a that may correspond in location and configuration to the corner portion 38 in
The side plate 50 may further include a cut line 53 that extends along all or a portion of the perimeter edge 51. The cut line 53 may correspond to the location of one or more of the slots 44a, b in the frame 40 in
As described below, the holes 52 may be used to evacuate air during brazing and/or heat treatment of the core. The cut line 53 may be used to guide cutting of the side plate 50 after brazing.
In the configuration shown in
Likewise, a second or hot fin passage 71 is shown with a side bar cut away from a hot frame 75. The hot fin passage 71 is open to air entering or existing the passage 71 because of the side bar removal. However, the main bar 75a remains as part of the hot frame 75 for structural support.
In embodiments, a corner portion 78 extends from a top plate 76 and through the cold and hot frames 74, 75. However, the corner portion 78 is devoid of a butter-pass weld yet ready for the next assembly.
From the foregoing, it can be seen that an exemplary method of the present invention can include surrounding a hot fin passage with a hot frame that has one or more removable bars. The method can further include surrounding a cold fin passage with a cold frame that has one or more removable bars. With side plates sandwiching the hot fin passage, hot frame, slotted tube sheet, cold fin passage, and cold frame, the core can be brazed.
During brazing, according to the exemplary method, one or more slots in the hot and cold frames may allow for the evacuation of air in the core. Holes in the side plates may assist in that evacuation.
After brazing, the exemplary method may include removing/cutting one or more of the removable bars from one or both of the hot and cold frames. The removable bars can include a pair of opposed support bars and a pair of opposed side bars. Cutting can be along groove guides in the removable bars. A main bar is left as part of at least one of the hot and cold frames. The exemplary method may additionally include cutting away a portion of the side plates after brazing.
Also after brazing, the core is left devoid of a butter-pass weld.
It should be understood, of course, that the foregoing relates to exemplary embodiments of the invention and that modifications may be made without departing from the spirit and scope of the invention as set forth in the following claims.
