Patent Publication Number: US-2019178580-A1

Title: Multiple tube bank heat exchange unit with manifold assembly

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of U.S. application Ser. No. 14/763,557 filed Jul. 27, 2015, which is a National Stage Application of PCT/US2013/071644, filed Nov. 25, 2013, which claims the benefit of U.S. Provisional Application No. 61/757,273 filed Jan. 28, 2013, all of which are incorporated herein by reference in their entirety. 
    
    
     BACKGROUND 
     This invention relates generally to heat exchangers and, more particularly, to multiple tube bank heat exchange unit incorporating a manifold assembly. 
     Heat exchangers have long been used as evaporators and condensers in heating, ventilation, air conditioning and refrigeration (HVACR) applications. Historically, these heat exchangers have been round tube and plate fin (RTPF) heat exchangers. However, all aluminum flattened tube serpentine fin heat exchangers are finding increasingly wider use in industry, including the HVACR industry, due to their compactness, thermal-hydraulic performance, structural rigidity, lower weight and reduced refrigerant charge, in comparison to conventional RTPF heat exchangers. Flattened tubes commonly used in HVACR applications typically have an interior subdivided into a plurality of parallel flow channels. Such flattened tubes are commonly referred to in the art as multi-channel tubes, mini-channel tubes or micro-channel tubes. 
     A typical flattened tube serpentine fin heat exchanger includes a first manifold, a second manifold, and a single tube bank formed of a plurality of longitudinally extending flattened heat exchange tubes disposed in spaced parallel relationship and extending between the first manifold and the second manifold. The first manifold, second manifold and tube bank assembly is commonly referred to in the heat exchanger art as a slab. Additionally, a plurality of fins are disposed between the neighboring pairs of heat exchange tubes for increasing heat transfer between a fluid, commonly air in HVACR applications, flowing over the outside surfaces of the flattened tubes and along the fin surfaces and a fluid, commonly refrigerant in HVACR applications, flowing inside the flattened tubes. Such single tube bank heat exchangers, also known as single slab heat exchangers, have a pure cross-flow configuration. 
     Double bank flattened tube and serpentine fin heat exchangers are also known in the art. Conventional double bank flattened tube and serpentine fin heat exchangers are typically formed of two conventional fin and tube slabs, one spaced behind the other, with fluid communication between the manifolds accomplished through external piping. However, to connect the two slabs in fluid flow communication in other than a parallel cross-flow arrangement requires complex external piping. For example, U.S. Pat. No. 6,964,296 B2 and U.S. Patent Application Publication 2009/0025914 A1 disclose embodiments of double bank, multichannel flattened tube heat exchanger. 
     BRIEF DESCRIPTION 
     In an aspect, a multiple bank, flattened tube heat exchange unit includes a first tube bank including a plurality of flattened tube segments extending longitudinally in spaced parallel relationship between a first manifold and a second manifold and a second tube bank including a plurality of flattened tube segments extending longitudinally in spaced parallel relationship between a first manifold and a second manifold, the second tube bank disposed behind the first tube bank. The second manifold of the first tube bank and the second manifold of the second tube bank form a manifold assembly wherein an interior volume of the second manifold of the first tube bank and an interior volume of the second manifold of the second tube bank of the manifold assembly are connected in fluid communication internally, that is not through external piping. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For further understanding of the disclosure, reference will be made to the following detailed description which is to be read in connection with the accompanying drawing, where: 
         FIG. 1  is a diagrammatic illustration of an embodiment of a multiple tube bank, flattened tube finned heat exchange unit as disclosed herein; 
         FIG. 2  is a side elevation view, partly in section, illustrating an embodiment of a fin and a set of integral flattened tube segment assemblies of the heat exchange unit of  FIG. 1 ; 
         FIG. 3  is a top plan view of an embodiment single pass, multiple pass counter crossflow embodiment of the heat exchange unit of  FIG. 1 ; 
         FIG. 4  is a top plan view of an embodiment single pass, single pass counter crossflow embodiment of the heat exchange unit of  FIG. 1 ; 
         FIG. 5  is a sectioned plan view of an embodiment of a manifold assembly of paired generally D-shaped tubular manifolds at the intermediate side of the heat exchanger unit of  FIG. 1  connected in fluid communication through a block insert disposed therebetween; 
         FIG. 6  is a sectioned plan view of an embodiment of a manifold assembly of paired generally cylindrical tubular manifolds at the intermediate side of the heat exchanger unit of  FIG. 1  connected in fluid communication through a block insert disposed therebetween; 
         FIG. 7  is a sectioned plan view of an embodiment of a manifold assembly of paired generally cylindrical tubular manifolds at the intermediate side of the heat exchanger unit of  FIG. 1  connected in fluid communication through a plurality of individual tubular members extending therebetween; 
         FIG. 8  is a sectioned plan view of another embodiment of a manifold assembly of paired generally tubular manifolds at the intermediate side of the heat exchanger unit of  FIG. 1  connected in fluid communication through a plurality of individual tubular members extending therebetween; 
         FIG. 9  is a sectioned plan view of another embodiment of a manifold assembly of a full tubular manifold and a partially open tubular manifold disposed in interfacing abutting relationship at the intermediate side of the heat exchanger unit of  FIG. 1 ; 
         FIGS. 10A and 10B  are sectioned plan views of alternate embodiments of a manifold assembly of paired partially open tubular manifolds joined in engaging relationship at the intermediate side of the heat exchanger unit of  FIG. 1 ; 
         FIG. 11  is a sectioned plan view of another embodiment of a manifold assembly of paired partially open tubular manifolds joined in interfacing abutting relationship at the intermediate side of the heat exchanger unit of  FIG. 1 ; 
         FIG. 12  is a sectioned plan view of an embodiment of a manifold assembly of paired partially open tubular manifolds interconnected in fluid communication through a flow passage through a single block insert disposed between the manifolds; 
         FIG. 13  is a sectioned plan view of an embodiment of a manifold assembly of paired partially open tubular manifolds interconnected in fluid communication through a flow passage formed by two block inserts; 
         FIG. 14  is a sectioned plan view of an embodiment of a manifold assembly of paired partially open tubular manifolds interconnected in fluid communication through a flow passage through a block insert disposed internally at the interface between the manifolds; 
         FIG. 15  is a perspective view of a cladded sheet from which an integral folded manifold assembly may be formed; 
         FIG. 16  is a sectioned plan view of an embodiment of a generally tubular integral folded manifold assembly formed of a single folded sheet; 
         FIG. 17  is a sectioned plan view of another embodiment of a generally tubular integral folded manifold assembly formed of a single folded sheet; 
         FIG. 18  is a sectioned plan view of another embodiment of a generally tubular integral folded manifold assembly formed of a single folded sheet; 
         FIG. 19  is a sectioned plan view of an embodiment of an extruded dual-barrel embodiment of an integral manifold assembly; 
         FIG. 20  is a sectioned plan view of an embodiment of a fabricated flat integral manifold assembly defining a single fluid chamber; 
         FIG. 21  is a sectioned plan view of an embodiment of a fabricated flat integral manifold assembly defining a pair of fluid chambers; and 
         FIGS. 22A-D  are sectioned plan views of various exemplary embodiments of a fabricated flat integral assembly formed from a single folded sheet. 
     
    
    
     DETAILED DESCRIPTION 
     An exemplary embodiment of a multiple bank flattened tube finned heat exchanger unit in accordance with the disclosure, generally designated  10 , is depicted in perspective illustration in  FIG. 1 . As depicted therein, the multiple bank flattened tube finned heat exchanger  10  includes a first tube bank  100  and a second tube bank  200  that is disposed behind the first tube bank  100 , that is downstream with respect to air flow, A, through the heat exchanger. The first tube bank  100  may also be referred to herein as the front heat exchanger slab  100  and the second tube bank  200  may also be referred to herein as the rear heat exchanger slab  200 . 
     The first tube bank  100  includes a first manifold  102 , a second manifold  104  spaced apart from the first manifold  102 , and a plurality of heat exchange tube segments  106 , including at least a first and a second tube segment, extending longitudinally in spaced parallel relationship between and connecting the first manifold  102  and the second manifold  104  in fluid communication. The second tube bank  200  includes a first manifold  202 , a second manifold  204  spaced apart from the first manifold  202 , and a plurality of heat exchange tube segments  206 , including at least a first and a second tube segment, extending longitudinally in spaced parallel relationship between and connecting the first manifold  202  and the second manifold  204  in fluid communication. As will be described in further detail herein later, each set of manifolds  102 ,  202  and  104 ,  204  disposed at either side of the dual bank heat exchanger  10  may comprise separate paired manifolds, may comprise separate chambers within an integral one-piece folded manifold assembly or may comprise separate chambers within an integral fabricated (e.g. extruded, drawn, rolled and welded) manifold assembly. Each tube bank  100 ,  200  may further include “dummy” tubes (not shown) extending between its first and second manifolds at the top of the tube bank and at the bottom of the tube bank. These “dummy” tubes do not convey refrigerant flow, but add structural support to the tube bank and protect the uppermost and lowermost fins. 
     Referring now to  FIG. 2 , each of the heat exchange tube segments  106 ,  206  comprises a flattened heat exchange tube having a leading edge  108 ,  208 , a trailing edge  110 ,  210 , an upper surface  112 ,  212 , and a lower surface  114 ,  214 . The leading edge  108 ,  208  of each heat exchange tube segment  106 ,  206  is upstream of its respective trailing edge  110 ,  210  with respect to airflow through the heat exchanger  10 . In the embodiment depicted in  FIG. 2 , the respective leading and trailing portions of the flattened tube segments  106 ,  206  are rounded thereby providing blunt leading edges  108 ,  208  and trailing edges  110 ,  210 . However, it is to be understood that the respective leading and trailing portions of the flattened tube segments  106 ,  206  may be formed in other configurations. 
     The interior flow passage of each of the heat exchange tube segments  106 ,  206  of the first and second tube banks  100 ,  200 , respectively, may be divided by interior walls into a plurality of discrete flow channels  120 ,  220  that extend longitudinally the length of the tube from an inlet end of the tube to an outlet end of the tube and establish fluid communication between the respective headers of the first and the second tube banks  100 ,  200 . In the embodiment of the multi-channel heat exchange tube segments  106 ,  206  depicted in  FIG. 2 , the heat exchange tube segments  206  of the second tube bank  200  have a greater width than the heat exchange tube segments  106  of the first tube bank  100 . Also, the interior flow passages of the wider heat exchange tube segments  206  may be divided into a greater number of discrete flow channels  220  than the number of discrete flow channels  120  into which the interior flow passages of the heat exchange tube segments  106  are divided. The flow channels  120 ,  220  may have a circular cross-section, a rectangular cross-section or other non-circular cross-section. 
     The second tube bank  200 , i.e. the rear heat exchanger slab, is disposed behind the first tube bank  100 , i.e. the front heat exchanger slab, with respect to the airflow direction, with each heat exchange tube segment  106  directly aligned with a respective heat exchange tube segment  206  and with the leading edges  208  of the heat exchange tube segments  206  of the second tube bank  200  spaced from the trailing edges  110  of the heat exchange tube segments of the first tube bank  100  by a desired spacing, G. A spacer or a plurality of spacers disposed at longitudinally spaced intervals may be provided between the trailing edges  110  of the heat exchange tube segments  106  and the leading edges  208  of the heat exchange tube segments  206  to maintain the desired spacing, G, during brazing of the preassembled heat exchanger unit  10  in a brazing furnace. 
     In the embodiment depicted in  FIG. 2 , an elongated web  40  or a plurality of spaced web members  40  span the desired spacing, G, along at least of portion of the length of each aligned set of heat exchange tube segments  106 ,  206 . For a further description of a dual bank, flattened tube finned heat exchanger unit wherein the heat exchange tubes  106  of the first tube bank  100  and the heat exchange tubes  206  of the second tube bank  200  are connected by an elongated web or a plurality of web members, reference is made to U.S. provisional application Ser. No. 61/593,979, filed Feb. 2, 2012, the entire disclosure of which is hereby incorporated herein by reference. 
     Referring still to  FIGS. 1 and 2 , the flattened tube finned heat exchanger  10  disclosed herein further includes a plurality of folded fins  320 . Each folded fin  320  is formed of a single continuous strip of fin material tightly folded in a ribbon-like serpentine fashion thereby providing a plurality of closely spaced fins  322  that extend generally orthogonal to the flattened heat exchange tubes  106 ,  206 . Typically, the fin density of the closely spaced fins  322  of each continuous folded fin  320  may be about 16 to 25 fins per inch, but higher or lower fin densities may also be used. Heat exchange between the refrigerant flow, R, and air flow, A, occurs through the outside surfaces  112 ,  114  and  212 ,  214 , respectively, of the heat exchange tube segments  106 ,  206 , collectively forming the primary heat exchange surface, and also through the heat exchange surface of the fins  322  of the folded fin  320 , which forms the secondary heat exchange surface. 
     In the depicted embodiment, the depth of each of the ribbon-like folded fin  320  extends at least from the leading edge  108  of the first tube bank  100  to the trailing edge of  210  of the second bank  200 , and may overhang the leading edge  108  of the first tube bank  100  or/and trailing edge  208  of the second tube bank  200  as desired. Thus, when a folded fin  320  is installed between a set of adjacent multiple tube, flattened heat exchange tube assemblies  240  in the array of tube assemblies of the assembled heat exchanger  10 , a first section  324  of each fin  322  is disposed within the first tube bank  100 , a second section  326  of each fin  322  spans the spacing, G, between the trailing edge  110  of the first tube bank  100  and the leading edge  208  of the second tube bank  200 , and a third section  328  of each fin  322  is disposed within the second tube bank  200 . In an embodiment, each fin  322  of the folded fin  320  may be provided with louvers  330 ,  332  formed in the first and third sections, respectively, of each fin  322 . 
     The multiple bank, flattened tube heat exchange unit  10  disclosed herein is depicted in a cross-counterflow arrangement wherein refrigerant (labeled “R”) from a refrigerant circuit (not shown) of a refrigerant vapor compression system (not shown) passes through the manifolds and heat exchange tube segments of the tube banks  100 ,  200 , in a manner to be described in further detail hereinafter, in heat exchange relationship with a cooling media, most commonly ambient air, flowing through the airside of the heat exchanger  10  in the direction indicated by the arrow labeled “A” that passes over the outside surfaces of the heat exchange tube segments  106 ,  206  and the surfaces of the folded fin strips  320 . The air flow first passes transversely across the upper and lower horizontal surfaces  112 ,  114  of the heat exchange tube segments  106  of the first tube bank, and then passes transversely across the upper and lower horizontal surfaces  212 ,  214  of the heat exchange tube segments  206  of the second tube bank  200 . The refrigerant passes in cross-counterflow arrangement to the airflow, in that the refrigerant flow passes first through the second tube bank  200  and then through the first tube bank  100 . The multiple tube bank, flattened tube finned heat exchanger  10  having a cross-counterflow circuit arrangement yields superior heat exchange performance, as compared to the crossflow or cross-parallel flow circuit arrangements, as well as allows for flexibility to manage the refrigerant side pressure drop via implementation of tubes of various widths within the first tube bank  100  and the second tube bank  200 . 
     In the embodiment depicted in  FIGS. 1 and 3 , the second tube bank  200 , i.e. the rear heat exchanger slab with respect to air flow, has a single-pass refrigerant circuit configuration and the first tube bank  100 , i.e. the front heat exchanger slab with respect to air flow, has a two pass configuration. Refrigerant flow passes from a refrigerant circuit (not shown) into the first manifold  202  of the second tube bank  200  through at least one refrigerant inlet  222  ( FIG. 3 ), passes through the heat exchange tube segments  206  into the second manifold  204  of the second tube bank  200 , then passes into the second manifold  104  of the first tube bank  100 , thence through a lower set of the heat exchange segments  106  into the first manifold  102  of the first tube bank  100 , thence back to the second manifold  104  through an upper set of the heat exchange tubes  106 , and thence passes back to the refrigerant circuit through at least one refrigerant outlet  122 . 
     In the embodiment depicted in  FIG. 4 , the second tube bank  200 , i.e., the rear heat exchanger slab with respect to air flow, has a single-pass refrigerant circuit configuration and the first tube bank  100 , i.e. the front heat exchanger slab with respect to air flow, also has a single pass configuration. Refrigerant flow passes from a refrigerant circuit (not shown) into the first manifold  202  of the second tube bank  200  through at least one refrigerant inlet  222 , passes through the heat exchange tube segments  206  into the second manifold  204  of the second tube bank  200 , then passes into the second manifold  104  of the first tube bank  100 , thence passes through the heat exchange segments  106  into the first manifold  102  of the first tube bank  100 , and thence passes back to the refrigerant circuit through at least one refrigerant outlet  122 . 
     In the embodiments depicted in  FIGS. 1, 3 and 4 , the neighboring second manifolds  104  and  204  are connected in fluid flow communication such that refrigerant may flow from the interior of the second manifold  204  of the second tube bank  200  into the interior of the second manifold  104  of the first tube bank  100 . In an embodiment, the second manifold  104  of the first tube bank  100  has a plurality of longitudinally aligned ports, e.g., holes  244  ( FIG. 5 ), drilled, milled or punched through the wall thereof and disposed at longitudinally spaced intervals. Similarly, the second manifold  204  of the second tube bank  200  has a plurality of longitudinally aligned ports, e.g., holes  246  ( FIG. 5 ), equal in number to the plurality of holes  244  in the second manifold  104  of the first tube bank  100 , drilled, milled or punched through the wall thereof and disposed at longitudinally spaced intervals. Each port  244  forms a flow passage through the wall of the second manifold  104  and each port  246  forms a flow passage through the wall of the second manifold  204 . When the heat exchanger unit  10  is assembled, each flow passage, i.e. port  246 , in the second manifold  204  aligns with a respective one of the flow passages, i.e. port  244 , of the first manifold  104 . It should be understood that the ports  244 ,  246  may be holes of the same size, however certain design configuration may benefit of the holes being of different sizes. 
     In the embodiment depicted in  FIG. 5 , a block insert  240  having a central passage  242  extending longitudinally therethrough is positioned between the manifolds  104  and  204  is positioned such that the central passage  242  aligns with ports  244  and  246  formed through the respective walls of the manifolds  104  and  204 , respectively, and spans the longitudinally expanse of the longitudinally spaced ports  244  and  246 . So assembled, a plurality of continuous flow passages are established through which refrigerant may pass from the interior of the second manifold  204  of the second tube bank  200  through the port  246 , thence through the central passage  242  of the block insert  240 , and thence through the port  244  into the interior of the second manifold  104  of the first tube bank  100 . In this embodiment, the block insert  240  may comprise a longitudinally elongated block having a single longitudinally extending slot forming a longitudinally elongated central passage  242  that interfaces with all of the plurality of ports  244  and  246 . Alternatively, a longitudinally elongated central passage  242  that interfaces with ports  244  and  246  may be represented by a plurality of slots, each slot spanning only a portion of the aligned ports  244  and  246 . In the embodiment depicted in  FIG. 5 , the first and second manifolds  104 ,  204  are both generally D-shaped manifolds disposed in back-to-back spaced relationship with a generally rectangular block insert  242  disposed between the first and second manifolds  104 ,  204 . 
     In the embodiment depicted in  FIG. 6 , the first and second manifolds  104 ,  106  are both cylindrical manifolds disposed in side-to-side spaced relationship with a contoured block insert  240 . In this embodiment, the side faces  248  of the block insert  240  are contoured concave inwardly to match and mate with the contour of the external surface of the respective abutting second manifolds. In this embodiment, the block insert  240  may comprise a longitudinally elongated block having a pair of laterally spaced, longitudinally extending slots forming longitudinally elongated flow passages  248  and having a plurality of longitudinally spaced bores  245  interconnecting the laterally spaced flow passages  248  in fluid communication. The bores  245  may be disposed in alignment with the ports  244  and  246  in the first and second manifolds  104 ,  204 , respectively. In either of the embodiments depicted in  FIGS. 5 and 6 , the block insert  240  is metallurgically bonded, for example by brazing or welding, to each of the second manifolds  104  and  204 . It should be understood that brazing can be accomplished during furnace brazing of the entire heat exchanger construction. 
     In the embodiments depicted in  FIGS. 7 and 8 , the second manifolds  104  and  204  are connected in fluid communication through a plurality of individual tubular members  250  interconnecting the plurality of aligned pairs of ports  244  and  246  in the first and second manifolds  104 ,  204 , respectively. Each tubular member  250  extends through a respective one of the plurality of longitudinally spaced sets of aligned ports  244  and  246 , whereby each tubular member forms a flow passage  252  between the interior of the second manifold  204  of the second tube bank  200  and the interior of the second manifold  104  of the first tube bank  100 . In the embodiments as depicted in  FIGS. 7 and 8 , the tubular member  250  has a tubular first end  256  and a tubular second end  258  and a radially outwardly directed flange  260  extending circumferentially about a mid-portion of the tubular member  250  between the first end  256  and the second end  258 . In the embodiment as depicted in  FIG. 7 , the first end  256  extends through a port  244  in the manifold  104  and the second end  258  extends through a port  246  in the manifold  24  and each tubular member  250  may be metallurgically bonded to the manifolds  104  and  204 , for example by brazing during brazing of the entire heat exchanger assembly in a brazing furnace. Additionally, the thickness of the flange  260  may be sized to ensure a desired spacing between the second manifolds  104  and  204 . 
     In the embodiment depicted in  FIG. 8 , the first end  256  of each tubular member  250  is threaded and is inserted into a respective one of a plurality of threaded sockets provided in a longitudinally extending block  254 . Each socket is aligned with a respective one of the ports  244  in the manifold  104 . The second end  258  of each tubular member  250  is inserted into a respective one of the ports  246  in the manifold  204 . The block  254  and the second end  258  are metallurgically bonded to the manifold  104  and the manifold  204 , respectively, for example by brazing during brazing of the entire heat exchanger assembly in a brazing furnace. In this embodiment, the flange  260  may be hexagonal, octagonal or otherwise shaped to accommodate a wrench or other tool by which the tubular member  250  may be screwed into a respective one of the threaded holes of the longitudinally extended block  254 . 
     In each of the embodiments depicted in  FIGS. 5-8 , the paired tubular manifolds  104  and  204  in fluid communication through the plurality of longitudinally spaced, aligned and interfacing sets of ports  244  and  246  that are connected through a passage or passages provided in one or more inserts  240 ,  260  disposed between and brazed to the paired manifolds  104 ,  204 , rather than being connected via external piping. The size, number and spacing of the ports  244 ,  246 , as well as the thickness of the wall of the tubular manifolds  104 ,  204 , may be selected to satisfy structural considerations. The cross-sectional area of the ports  244 ,  246  may be sized to satisfy thermo-hydraulic considerations. 
     Referring now to  FIG. 9 , there is depicted an embodiment of a fabricated integral manifold assembly  270  wherein one of the second manifolds  104 ,  204  is a full tubular manifold and the other of the second manifolds  104 ,  204  is a partially tubular manifold being open longitudinally along its entire length over a sector of the circumference of the manifold. The fully tubular manifold, shown in  FIG. 9  as being the second manifold  204  of the second manifold  200 , has a plurality of longitudinally aligned holes or slots  274  drilled, milled or punched through the wall thereof and disposed at longitudinally spaced intervals. The partially tubular manifold, shown in  FIG. 9  as being the second manifold  104  of the first manifold  100 , is disposed side-by-side along the fully tubular manifold  204  with the longitudinally open sector straddling the plurality of holes or slots  274  machined through the wall of the second manifold  204  there by establishing fluid flow communication between the respective interior chambers of the second manifolds  104  and  204 . 
     The partially tubular manifold and the fully tubular manifold are metallurgically bonded, such as by brazing or welding, along the interfaces of the partially tubular manifold with the fully tubular manifold to form the integral manifold assembly  270 . A conventional roll and weld process may be used for both the fully tubular manifold and the partially tubular manifold. The longitudinal sides  276  extending along the open sector of the partially tubular manifold may be flared outwardly and contoured to provide a mating interface with the fully tubular manifold. 
     Referring now to  FIGS. 10-11 , there are depicted various exemplary embodiments of a fabricated integral manifold assembly  270  wherein at least one or both of the second manifolds  104 ,  204  comprises a partially tubular manifold being open longitudinally along its entire length or a portion of the entire length over a sector of the circumference/perimeter of the manifold. The two manifolds  104 ,  204 , which may be formed by extrusion, are metallurgically bonded together along a brazing joint  275  to form the fabricated integral manifold assembly  270 . In the embodiments shown in  FIGS. 10A and 10B , the manifolds  104  and  204  are extruded with flanges  272  and  276 , respectively, flanking their respective longitudinally extending open portions. The manifolds  104  and  204  are assembled together with the flanges of one of the manifolds  104 ,  204  inserted within the flanges of the other of the manifolds  104 ,  204  to interface along a joint  275  and to form a flow passage  274  interconnecting the respective interiors of the manifolds  104 ,  204 . The manifolds  104 ,  204  can be metallurgically bonded together along the joint  275  by brazing during brazing of the entire heat exchanger assembly in a brazing furnace. In an embodiment, both of the manifolds  104 ,  204  are extruded as partially tubular manifolds being open longitudinally along its entire length over a sector of the circumference/perimeter of the manifold. In an embodiment, one of the manifolds, i.e. the manifold  104  in  FIG. 10A  and the manifold  204  in  FIG. 10B , is extruded as a circumferentially closed tubular member having a plurality of longitudinally spaced, aligned holes that are disposed in fluid communication with the open sector of the other manifold when the heat exchanger is assembled prior to brazing the entire heat exchanger assembly. 
     In the embodiment of the fabricated integral manifold assembly  270  depicted in  FIG. 11 , the two manifolds  104 ,  204  are assembled in abutting relationship with their respective open portions facing each other to form a flow passage  274  and with their wall portions flanking their respective open portions interfacing along joints  275  along which the manifolds  104 ,  204  are metallurgically bonded together along the joint  275  by brazing during brazing of the entire heat exchanger assembly in a brazing furnace. In another embodiment of the fabricated integral manifold assembly depicted in  FIG. 11 , one or both of the manifolds  104 ,  204  may be formed as a fully closed tubular member having a plurality of longitudinally spaced, aligned holes instead of being a partially open tubular manifold having a open sector extending the length thereof. 
     Referring now to  FIGS. 12-14 , there are depicted embodiments of a fabricated integral manifold assembly  270  wherein both of the manifolds  104 ,  204  are formed as partially open tubular manifolds being open longitudinally along its entire length over a sector of the circumference/perimeter of the manifold. In the embodiment of the fabricated integral manifold assembly  270  depicted in  FIGS. 12 and 13 , the two manifolds  104 ,  204  are assembled in spaced relationship with their respective open portions facing each other. In the embodiment depicted in  FIG. 12 , a longitudinally extending block insert  278  having a plurality of bores  277  extending transversely therethrough is disposed between the two manifolds  104 ,  204  to form a plurality of flow passages  274  between the interiors of the manifolds  104 ,  204 . The block insert  278  is brazed to the interfacing outer wall portions of the manifolds  104 ,  204  to form joints  275 . In the embodiment of the fabricated integral manifold assembly  270  depicted in  FIG. 13 , a pair of longitudinally extending block inserts  279  is disposed in spaced relationship between the spaced open manifolds  104 ,  204  so as to form a flow passage  274  between the interiors of the manifolds  104 ,  204 . The block inserts  279  are brazed to the interfacing wall portions of the manifolds  104 ,  204  to form joints  275 . In the embodiment depicted in  FIG. 14 , a longitudinally extending block insert  278  having a plurality of longitudinally spaced bores  277  extending transversely therethrough is disposed internally between the respective flanges  272 ,  276  of the two manifolds  104 ,  204  to form a plurality of flow passages  274  between the interiors of the manifolds  104 ,  204 . The block insert  278  is brazed to the interfacing inner wall portion of the flanges of the manifolds  104 ,  204 . 
     The manifold assembly disclosed herein may also be formed from a single metal sheet as an integral folded manifold assembly. Referring to a  FIG. 15 , the single sheet  286  of aluminum alloy from which the integral folded manifold assembly is formed is clad with a layer  285  of suitable brazing alloy and provided with a plurality of first ports  281  and a plurality of second ports  283 . The ports  281  and  283  may comprise pre-drilled, pre-milled or pre-punched round holes or pre-fabricated elliptical, racetrack, rectangular, triangular or any other cross-section suitable for a particular manufacturing process and heat exchanger design configuration. To form the integral folded manifold assembly  280 , the sheet  286  is folded upon itself such as the wall portions  282 ,  284  interface in side-by-side relationship such as illustrated in  FIG. 10  or in  FIG. 11 , whereby each one of the plurality of first ports  281  registers with a corresponding one of the plurality of second ports  283 . The interfacing surfaces of the cladded wall portions  282  and  284  are metallurgically bonded together when the assembled heat exchanger unit  10  is brazed in the brazing furnace, for example a controlled atmosphere brazing furnace. 
     Referring now to  FIGS. 16, 17 and 18 , there are depicted various exemplary embodiments of an integral folded manifold assembly  280  formed from a single folded sheet  286 . The first manifold  104  and the second manifold  204  are formed in an integral folded manifold assembly  280  with respective wall portions  282 ,  284  of the manifolds  104 ,  204  disposed in interfacing side-by-side abutting relationship with a plurality of first ports  281  formed in the wall portion  282  being in registration with a similar plurality of second ports  283  formed in the interfacing wall portion  284 . The respective pairs of aligned ports  281  and  283  form flow passages establishing internal fluid flow communication through which refrigerant may pass from the second manifold  204  into the first manifold  104 . In each embodiment depicted in  FIGS. 16, 17 and 18 , the integral folded manifold assembly  280  is formed by folding a single sheet  286  of clad aluminum alloy onto itself and metallurgically bonding the overlapping or abutting portions of the folded sheet to each other along a brazing joint  275 . This allows for a single braze operation of the manifold and heat exchanger core during the furnace braze process. Furthermore, one set of the first ports  281  or second ports  283  can be slightly oversized in comparison to the other of the first ports  281  or the second ports  283  for easier alignment during the manifold forming process. 
     The manifold assembly disclosed herein may also be formed as an extruded integral dual barrel tubular manifold assembly  290 , for example as depicted in  FIG. 19 . The extruded manifold assembly  290  includes a first tubular barrel forming the manifold  104 , a second tubular barrel forming the manifold  204 , and a central web portion  292  joining the tubular barrels along the longitudinal extent of the assembly. A plurality of longitudinally spaced bores  295  extend transversely through the central web portion  292  to provide a plurality of flow passages  274  connecting the respective interiors of the manifolds  104 ,  204 . The bores  295  may be drilled through the central web portion  292  of the extruded manifold assembly  290  by first providing a series of longitudinal spaced holes  294 , for example by punching, drilling or milling, in the wall of one of the manifolds  104 ,  204  opposite the central web portion  292 . A drill bit is then inserted through each hole  294  and a bore  295  is drilled through the central web portion  292 . Each of the holes  294  is then closed by inserting a plug  296  into each hole  294 . The inserted plugs  296  are metallurgically bonded to the manifold assembly during the brazing of the heat exchanger assembly in a brazing furnace. 
     The manifold assembly disclosed herein may also be fabricated as a flat manifold rather than as paired tubular manifolds as in the previously described embodiments. Referring to  FIGS. 20 and 21 , the manifold assembly  380  depicted therein comprises a stamped cover plate  382  metallurically bonded at brazed joints  385  to a flat base plate  384 . Flat manifolds have a reduced interior volume as compared to comparable paired tubular manifolds. In refrigeration applications wherein the flat manifold is associated with a condenser heat exchanger, the reduced volume as compared to a comparable paired tubular manifold assembly can reduce refrigerant charge requirements up to 50%. 
     In the embodiment depicted in  FIG. 20 , the cover plate  382  is stamped to define when joined to the flat base plate  384  a single longitudinally extending chamber into which both the plurality of heat exchange tube segments  106  and the plurality of heat exchange tube segments  206  open so that refrigerant may flow from the heat exchange tube segments  106  into the heat exchange tube segments  206 . In the embodiment depicted in  FIG. 21 , the cover plate  382  is stamped to define when joined to the flat base plate  384  a pair of longitudinally extending chambers  387  and  388  extending in parallel spaced relationship. In this embodiment, the heat exchange tube segments  106  open into chamber  387  and the heat exchange tube segments  206  open into chamber  388 . Cross-over flow passages  389  may be stamped in the cover plate  382  at one or more locations along the length of the longitudinally extending cover plate  382  as desired to provide flow communication between chamber  387  and chamber  388 . The location of the cross-over passages  389  determines the flow circuitry of the refrigerant passing between the chambers  387  and  388 . 
     As depicted in  FIGS. 22A-D , the flat manifold  380  may also be formed integrally from a single metal plate  386  folded into a desired shape with overlapping ends which are metallurgically bonded along a brazed joint  385 . Openings for receiving the heat exchange tube segments  106  and  206  may be punched or otherwise formed through the single plate  386  prior to or after folding the plate  386  into the desired shape. The single metal plate  386  may comprise an aluminum alloy plate clad with a suitable cladding material to facilitate brazing the overlapping end portions of the plate  386  together and also brazing the heat exchange tube segments  106  and  206  to the folded plate manifold. 
     Although described herein in application to the second manifolds  104 ,  204 , it is to be understood that in some embodiments of the multiple bank heat exchanger  10 , the first manifolds  102  and  202  may also be formed as an integral manifold having a chamber defining the first manifold  102  and a chamber forming the first manifold  202 . 
     While the present invention has been particularly shown and described with reference to the exemplary embodiments as illustrated in the drawing, it will be recognized by those skilled in the art that various modifications may be made without departing from the spirit and scope of the invention. Therefore, it is intended that the present disclosure not be limited to the particular embodiment(s) disclosed as, but that the disclosure will include all embodiments falling within the scope of the appended claims.