Abstract:
A fin has a substantially flat base plane with a first side facing a first direction and a second side facing a second direction. The fin also has a first louver with a leading edge closer to the base plane and a trailing edge offset from the base plane in the first direction, a second louver located at least partially downstream of the first louver, with a leading edge offset from the base plane in the second direction and a trailing edge offset from the base plane in the first direction, and a third louver located at least partially downstream of the second louver, the third louver having a leading edge offset from the base plane in the second direction and a trailing edge closer to the base plane than the third louver leading edge.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    Not Applicable. 
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not Applicable. 
       BACKGROUND 
       [0003]    Conventional air conditioning systems generally comprise a compressor, a condenser coil, a condenser fan for passing air through the condenser coil, a flow restriction device, an evaporator coil, and an evaporator blower for passing air through the evaporator coil. The condenser coil and the evaporator coil are each designed as heat exchangers with internal tubing for carrying refrigerant. Further, evaporator coils and condenser coils sometimes comprise a plurality of fins disposed along a length of the internal tubing so that the internal tubing passes through holes formed in the adjacent plate fins. 
         [0004]    The compressor operates to compress refrigerant into a hot and high pressure gas, which is passed through the internal tubing of the condenser coil. As the refrigerant is passed through the condenser coil, the condenser fan operates to pass ambient air across the condenser coil, thereby removing heat from the refrigerant and condensing the refrigerant into liquid form. The liquid refrigerant passes through a flow restriction device, which causes the refrigerant to transform into a colder and lower pressure liquid/gas mixture that proceeds to the evaporator. As the mixture is passed through the evaporator coil, the evaporator blower forces ambient air across the evaporator coil, thereby providing a cooling and dehumidifying effect to the ambient air, which is then distributed to the space to be temperature controlled. 
         [0005]    In some applications, heat exchangers (i.e., evaporator or condenser coils) comprise a plurality of fins that are arranged so that adjacent fins are substantially parallel to each other and offset by a fin pitch distance, and a plurality of refrigerant tubes disposed generally orthogonally to the plurality of fins. Most generally, a fin may be described as a thin plate constructed of metal or other materials suitable for conducting heat and comprising a series of holes formed therein that are suitable for receiving refrigerant tubing therethrough. A plurality of fins comprising substantially similar hole patterns may be arranged in a stack, in some embodiments with adjacent fins equally offset by the fin pitch distance, so that refrigerant tubes may each be received through corresponding holes in the plurality of fins. In other words, each refrigerant tube may be inserted substantially orthogonally through corresponding holes in the stack of fins so that the fins are disposed along the refrigerant tubing, thereby forming what may be referred to as a slab of the heat exchanger. 
       SUMMARY OF THE DISCLOSURE 
       [0006]    In some embodiments, this disclosure relates to a fin comprising a substantially flat base plane having a first side facing a first direction and a second side facing a second direction. The fin further comprises a first louver comprising a leading edge and a trailing edge, wherein the leading edge is closer to the base plane than the trailing edge and the trailing edge is offset from the base plane in the first direction; a second louver located at least partially downstream of the first louver, the second louver comprising a leading edge and a trailing edge, wherein the leading edge is offset from the base plane in the second direction and the trailing edge is offset from the base plane in the first direction; and a third louver located at least partially downstream of the second louver, the third louver comprising a leading edge and a trailing edge, wherein the leading edge is offset from the base plane in the second direction and the trailing edge is closer to the base plane than the leading edge. 
         [0007]    In some embodiments, the present disclosure relates to a fin comprising a substantially flat base plane having a first side facing a first direction and a second side facing a second direction. The fin further comprises a central louver comprising a leading edge and a trailing edge, wherein the leading edge and the trailing edge are offset from the base plane in the same one of the first direction and the second direction; and a nearest located louver located nearest the central louver, the nearest located louver comprising a nearest located edge located nearest the central louver, wherein the nearest located edge is nearer the base plane than any portion of the central louver. 
         [0008]    In some embodiments the present disclosure relates to a fin comprising a substantially flat base plane having a first side facing a first direction and a second side facing a second direction. The fin further comprises a first louver comprising a leading edge and a trailing edge, wherein the leading edge is closer to the base plane than the trailing edge, the trailing edge is offset from the base plane in the first direction, and the first louver is formed into a concave curve open toward the first direction; a second louver located at least partially downstream of the first louver, the second louver comprising a leading edge and a trailing edge, wherein the leading edge is offset from the base plane in the second direction, the trailing edge is offset from the base plane in the first direction, and is substantially flat; a third louver located at least partially downstream of the second louver, the third louver comprising a leading edge and a trailing edge, wherein the leading edge is offset from the base plane in the second direction, the trailing edge is closer to the base plane than the leading edge, and the third louver is formed into a concave curve open toward the second direction; a fourth louver located at least partially downstream of the third louver, the fourth louver comprising a leading edge and a trailing edge, wherein both the leading edge and the trailing edge are offset in the first direction, and wherein the fourth louver is substantially flat; a fifth louver located at least partially downstream of the fourth louver, the fifth louver comprising a leading edge and a trailing edge, wherein the trailing edge is offset from the base plane in the second direction, the leading edge is closer to the base plane than the trailing edge, and wherein the fourth louver is formed into a concave curve open toward the second direction; a sixth louver located at least partially downstream of the fifth louver, the sixth louver comprising a leading edge and a trailing edge, wherein the leading edge is offset from the base plane in the first direction, the trailing edge is offset from the base plane in the second direction, and wherein the sixth louver is substantially flat; and a seventh louver located at least partially downstream of the sixth louver, the seventh louver comprising a leading edge and a trailing edge, wherein the trailing edge is closer to the base plane than the leading edge, the leading edge is offset from the base plane in the first direction, and wherein the seventh louver is formed into a concave curve open toward the first direction. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    For a more detailed description of the various embodiments disclosed herein, reference will now be made to the accompanying drawings, wherein: 
           [0010]      FIG. 1  is an oblique view of the top side of an embodiment of a fin as seen from an upstream location; 
           [0011]      FIG. 2  is another oblique view of the top side of the fin of  FIG. 1  as seen from an upstream location; 
           [0012]      FIG. 3  is an oblique view of the top side of the fin of  FIG. 1  as seen from a downstream location; 
           [0013]      FIG. 4  is an oblique view of the bottom side of the fin of  FIG. 1  as seen from an upstream location; 
           [0014]      FIG. 5  is an oblique view of the bottom side of the fin of  FIG. 1  as seen from a downstream location; 
           [0015]      FIG. 6  is a simplified cross-sectional schematic view of a finstrip of the fin of  FIG. 1 ; and 
           [0016]      FIG. 7  is a simplified cross-sectional schematic view of a plurality of fins with parallel finstrips. 
       
    
    
     DETAILED DESCRIPTION 
       [0017]    Some fins of heat exchangers comprise forms and features that increase heat transfer between the fins and the airflow passing over the fins. For example, fins may be constructed of relatively inexpensive and flexible flat finstock which may be easily lanced (cut and offset) or louvered (cut and twist) through well known manufacturing processes using dies and presses to improve heat transfer performance. However, some fins may be constructed by forming a wavy finstock from relatively thicker and more expensive flat finstock. Wavy finstock demonstrates good heat transfer performance with less pressure drop than lanced and/or louvered flat finstock. To further improve heat transfer performance, lanced and/or louvered features may also be formed on the wavy finstock. While some features formed on a wavy finstock in combination with the wavy or curved nature of the wavy finstock may offer improved heat transfer, the dies needed to form the fins from wavy finstock are more complex and more expensive. Because the flat finstock used to form the wavy finstock is thicker and more expensive than the thinner finstock that may be used when the finstock need not be pressed into a wavy form, use of wavy finstock is sometimes avoided due to cost considerations. 
         [0018]    The present disclosure is directed to flat fins and methods of making the flat fins with features that provide the heat transfer and low pressure drop performance of some lanced and/or louvered wavy fins. Accordingly, the present disclosure provides fins formed from flat finstock and methods of making fins formed from flat finstock that comprise louvers that direct airflow in a manner substantially the same as some louvered wavy fins. In this disclosure, the terms “upstream” and “downstream” are intended to indicate relative positions as related to the general intended overall direction of airflow across a fin of the present disclosure. Accordingly, for example, where a feature of a fin of this disclosure is described as being upstream relative to another feature of the fin, the upstream feature of the fin can be understood as being generally disposed so that the upstream feature encounters a portion of airflow prior to the relative downstream feature encountering the same portion of airflow. Further, it will be understood that the term “leading” may also refer to a relatively upstream located feature. Similarly, it will be understood that the term “trailing” may also refer to a relatively downstream located feature. Such relative positional terminology is well known in the art of heat exchanger fins. 
         [0019]    Referring now to  FIGS. 1-5 , various oblique views of the top side  103  and bottom side  105  of a fin  100  are shown from upstream and downstream positions. Fin  100  generally comprises a plurality of substantially similar finstrips  102 . Each finstrip  102  comprises a plurality of non-louvered, generally flat, substantially oval-shaped base regions  104 . Each base region  104  carries a substantially annular collar  106  surrounding a hole formed in the finstrip  102 . The collars  106  serve to increase the mechanical strength of the joinder between the fin  100  and refrigerant tubes that may extend through the hole and be carried within the collar  106 . The collar  106  also serves to increase the heat conductivity between the tubes and the fin  100 . The fin  100 , tube, and collar  106  may each be constructed of a suitable thermally-conductive material, such as, but not limited to, copper, aluminum, and the like. In this embodiment, the fin  100  comprises aluminum. Some of the base regions  104  further comprise a bluff body  108  located upstream of the collar  106 . The bluff bodies  108  increase turbulence near the collars  106  and tubes and thereby increase heat transfer. 
         [0020]    It will be appreciated that the base regions  104  are substantially formed from unbent flat finstock while the plurality of louvers, described in detail below, are formed by cutting, displacing, and twisting the same flat finstock. The bluff bodies  108  are generally formed by pressing the flat finstock. In this embodiment, each finstrip  102  further comprises an upstream louver  110 , an upstream straight louver  112 , an upstream curved louver  114 , a central louver  116 , a downstream curved louver  118 , a downstream straight louver  120 , and a downstream louver  122 . Further, each finstrip  102  of a fin  100  may be described as having a base plane  124  from which the louvers  110 ,  112 ,  114 ,  116 ,  118 ,  120 ,  122  are originally part of and subsequently bent or otherwise deformed away from during their creation. In some embodiments, the base regions  104  remain substantially coplanar with the base plane  124 . 
         [0021]    Referring now also to  FIG. 6 , it is clear that the various louvers  110 ,  112 ,  114 ,  116 ,  118 ,  120 ,  122  comprise different cross-sectional shapes and are formed differently with respect to the base plane  124 . Upstream louver  110  comprises a cross-sectional area that extends downstream from its leading edge that is substantially coplanar with the base plane  124  and gradually curves in a generally upwardly concave manner away from the base plane  124 . The upstream straight louver  112  is located just downstream from the upstream louver  110  and extends downstream from its leading edge that is below the base plane  124 , through the base plane  124 , and in a manner so that its trailing edge is located above the base plane  124 . The upstream straight louver  112  is substantially planar, straight, flat, and/or linear between its leading edge and its trailing edge. In this embodiment, both of the leading edge and the trailing edge of the upstream straight louver  112  are located substantially equidistant from the base plane  124 . The upstream curved louver  114  is located just downstream from the upstream straight louver  112  and extends downstream from its leading edge that is below the base plane  124  and gradually curves upward toward the base plane  124  in a generally concave manner so that the concavity is open away from and below the base plane  124 . The trailing edge of the upstream curved louver  114  is substantially coplanar with the base plane  124 . The central louver  116  is located just downstream of the upstream curved louver  114  and is substantially straight, flat, and/or linear, is substantially parallel to the base plane  124 , and is located above the base plane  124  by an offset distance. 
         [0022]    A bisection plane  126  is substantially orthogonal to the base plane  124  and substantially bisects the finstrip  102  along its length. In this embodiment, it will be appreciated that the pairs of cross-sectional areas of louvers,  110  and  122 ,  112  and  120 , and  114  and  118 , are substantially mirror images of each other about the bisection plane  126 . The downstream curved louver  118  is located just downstream of the central louver  116  and extends from its leading edge that is substantially coplanar with the base plane  124  and curves downwardly away from the base plane  124  in a generally concave manner so that the concavity is open away from and below the base plane  124 . The downstream straight louver  120  is located just downstream from the downstream curved louver  118  and extends downstream from its leading edge that is above the base plane  124 , through the base plane  124 , and in a manner so that its trailing edge is located below the base plane  124 . The downstream straight louver  120  is substantially planar, straight, flat, and/or linear between its leading edge and its trailing edge. In this embodiment, both of the leading edge and the trailing edge of the downstream straight louver  120  are located substantially equidistant from the base plane  124 . Downstream louver  122  comprises a cross-sectional area that extends downstream from its leading edge that is above the base plane  124  and gradually curves in a generally concave manner toward the base plane  124  so that the trailing edge of the downstream louver  122  is substantially coplanar with the base plane  124 . 
         [0023]    Referring again to  FIGS. 1-5 , it will be appreciated that the various finstrips  102  of the fin  100  are joined to adjacent finstrips of the same fin  100  by tabs  170  and bridges  172 . The tabs  170  are generally flat portions of material that are substantially coplanar with base plane  124  and which, in a manner similar to base regions  104 , may be unbent portions of the flat finstock from which the fin  100  is produced. However, the bridges  172 , which are formed between some of the tabs  170  along the length of the fin  100 , are portions of the fin  100  that are substantially flat, parallel, and offset above the base plane  124  in substantially the same manner central louvers  116  are offset from the base plane  124 . Still further, it will be appreciated that the upstream louver  110 ′ of the most upstream located finstrip  102  of fin  100  may comprise a slightly different cross-sectional area than the other upstream louvers  110 . Specifically, the upstream louver  110 ′ may comprise a leading edge located below the base plane  124 . In this embodiment, the upstream louver  110 ′ extends below the base plane  124  approximately the same distance the leading edge of the upstream straight louvers  112  extend below the base plane  124 . Similarly, it will be appreciated that the downstream louver  122 ′ of the most downstream located finstrip  102  of fin  100  may comprise a slightly different cross-sectional area than the other downstream louvers  122 . Specifically, the downstream louver  122 ′ may comprise a trailing edge located below the base plane  124 . In this embodiment, the downstream louver  122 ′ extends below the base plane  124  approximately the same distance the trailing edge of the downstream straight louvers  120  extend below the base plane  124 . 
         [0024]    Referring now to  FIG. 7 , a simplified schematic cross-sectional diagram of a plurality of fins  100  with parallel finstrips  102 , designated  102   a ,  102   b,    102   c,  and  102   d,  respectively, are shown as arranged in a heat exchanger slab. More specifically, the multiple finstrips  102  are disposed so that the various base planes  124   a ,  124   b ,  124   c , and  124   d  of the individual finstrips are substantially parallel to each other and so that adjacent finstrips  102  are equally offset from each other according to the fin pitch of the heat exchanger. In some embodiments, a heat exchanger may comprise a fin pitch of about 10-18 fins per inch. Of course, in alternative embodiments, the fin pitch may be different.  FIG. 7  is particularly useful in illustrating the manner in which airflow may be passed through a heat exchanger comprising a plurality of fins  100 . While specific reference to each may not further be utilized, each airflow space  128 ,  130 ,  132 ,  134 ,  136 ,  138 ,  140 ,  142 ,  144 ,  146 ,  148 ,  150 ,  152 ,  154 ,  156 ,  158 ,  160 ,  162 ,  164 ,  166 , and  168  will be understood as pictorial representations of airflow between adjacent fins  100  and as bound by adjacent and offset pairs of substantially similar louvers. For example, airflow space  128  represents the airflow space between adjacent and offset substantially similar upstream louvers  110   a  and  110   b.    
         [0025]    Still referring to  FIG. 7 , airflow that enters airflow space  130  between upstream louvers  110   b  and  110   c  may transfer heat with louvers  110   b  and  110   c . However, as is well known, heat transfer boundary layers begin to form which decrease the efficiency with which heat may transfer between the airflow and the upstream louvers  110   b  and  110   c . Accordingly, as the airflow exits the airflow space  130 , the airflow may be substantially divided, and in this embodiment substantially bisected by the upstream straight louver  112   c,  thereby diverting the airflow in to the airflow spaces  136  and  138 . As the airflow enters the airflow spaces  136  and  138 , the airflow is mixed with airflows that originated from airflow spaces  128  and  132 , respectively. As the airflow in airflow space  136  moves downstream, boundary layers again begin to form which hinder efficient heat transfer. Accordingly, as the airflow exits the airflow space  136 , the airflow is substantially bisected by the upstream curved louver  114   c . Inspection of  FIG. 7  reveals that such dividing and mixing of airflows is repeated as the airflows exit the various airflow spaces. Of course, in heat exchanger slabs comprising a plurality of fins such as fin  100  that comprises a plurality of finstrips  102 , the airflow that exits airflow spaces  164 ,  166 ,  168  may not exit the fin  100  entirely but may be directed into airflow spaces between downstream finstrips that are integrally attached thereto. It will further be appreciated from inspection of  FIG. 7  that air flowing between the adjacent finstrips  102  will generally undulate according to a wavy path as it moves downstream. 
         [0026]    Further, it will be appreciated that the louvers  110 ,  112 ,  114 ,  116 ,  118 ,  120 ,  122  may be provided in alternative embodiments with different relative sizes, different curvatures, and/or in different numbers of louvers on a finstrip  102 . Nonetheless, the alternative embodiments of louvers may still provide the above-mentioned mixing of airflows, dividing or bisecting of airflows, and guiding of airflows along a generally wavy path. Further, in alternative embodiments, rather than locating adjacent louvers of the same finstrip  102  so that airflows are bisected, the adjacent louvers may be located so that the leading edges of subsequent downstream located louvers are offset from the trailing edges of the nearest upstream louvers by at least about 25% of the fin pitch distance of a heat exchanger. In other words, in some embodiments, an airflow may be divided into unequal portions as it exits an airflow space. Still further, the overall dimensions of louvers of the various embodiments disclosed may be chosen to minimize the occurrence of trapping water between the louvers and adjacent structures of the fins. 
         [0027]    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, R 1 , and an upper limit, R u , is disclosed, any number falling within the range is specifically disclosed. In particular, the following numbers within the range are specifically disclosed: R=R 1 +k*(R u −R 1 ), 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. The discussion of a reference in the disclosure is not an admission that it is prior art, especially any reference that has a publication date after the priority date of this application. The disclosure of all patents, patent applications, and publications cited in the disclosure are hereby incorporated by reference in their entireties.