Patent Abstract:
A serpentine, multiple pass heat exchanger includes at least one flattened, multiple port tube in serpentine configuration with a plurality of general parallel runs defining at least three hydraulically separate flow paths fins. Fins extend between and are in thermal conducting relation with adjacent ones of the runs and an inlet manifold is located on one end of the tubes with an outlet manifold located on the other. A baffle is located in the outlet manifold and the inlet manifold includes a partition which extends both longitudinally and transversely within the inlet manifold to hydraulically separate one flow path from the inlet port while connecting other flow paths to each other to provide for multiple passes.

Full Description:
FIELD OF THE INVENTION 
   This invention relates to heat exchangers, and more particularly, to a serpentine heat exchanger having multiple passes. 
   BACKGROUND OF THE INVENTION 
   Serpentine heating exchangers are well known and typically include at least one flattened, multiple port tube, usually of extruded configuration, bent into a serpentine configuration to have a plurality of parallel runs where fins, generally serpentine fins, extend between adjacent ones of the parallel runs. These serpentine heat exchangers are most typically employed in two phase heating exchange as, for example, in refrigeration systems (including air conditioning systems) wherein a refrigerant passing through the tube changes phase. When used as an evaporator, the refrigerant evaporates from the liquid phase to the gaseous phase and where employed as a condenser or gas cooler, the refrigerant changes from the gaseous phase to or toward the liquid phase. Typical examples are illustrated in U.S. Pat. Nos. 5,368,097 and 5,036,909. Examples may also be seen in Japanese patent document 6-317363 of Nov. 15, 1994 and German patent document DE10049256A1. Reference may also be made to Japanese patent document JP06317363A. 
   In the German heat exchanger, special flow guiding locations are provided to convey the internal heat transfer medium from a rear cooling branch to a front cooling branch, the guiding configurations being individual tubes into which the ends of two cooling branches or sections constructed from two multiple channel flat tubes communicate. A gaseous heat exchange medium flows through several of the cooling branches arranged one behind the other in the same direction and while the construction works well for its intended purpose, manufacture can be difficult in terms of fitting the components that provide the guiding function to the apparatus. 
   The heat exchanger shown in U.S. Pat. No. 5,036,909 is intended for use as an evaporator in an air conditioner. This heat exchanger utilizes a separate tube to guide the refrigerant from a cooling branch in the inlet side to two subsequent cooling branches and is supposed to simultaneously serve as a mixing chamber for the equalization of the temperature of the internal heat exchange fluid. Another heat exchanger of this general type is shown in Japanese patent document JP06317363A. Both of these designs also work well for their intended purpose but may be difficult to manufacture for the reasons above stated. 
   The present invention is intended to overcome one or more of the above problems. 
   SUMMARY OF THE INVENTION 
   It is the principal object of the invention to provide a new and improved serpentine, multiple pass heat exchanger. More specifically, it is an object of the invention to provide such a heat exchanger that provides counter-cross current flow of one heat exchange medium in relation to the flow of the other and which employs simple and inexpensive means to guide the fluid through multiple passes within the heat exchanger. 
   An exemplary embodiment of the invention achieves the foregoing object in a serpentine, multiple pass heat exchanger that include at least one flattened multiple port tube in serpentine configuration with a plurality of generally parallel runs to define at least three hydraulically separate flow paths. Fins extend between and are in thermal conducting relation with adjacent ones of the runs for each flow path. An inlet manifold is disposed on one end of the tube or tubes and is in fluid communication with the ports therein. An outlet manifold is on the opposite end of the tube or tubes and in fluid communication with the ports therein. One of the flow paths is adjacent to the back side of the heat exchanger through which a gas may exit and another of the flow paths is adjacent a front of side of the heat exchanger through which a gas may enter. A baffle is disposed in the outlet manifold and separates another flow path and one of the other flow paths from the remaining flow paths. The inlet manifold has an inlet port through which a fluid may enter the inlet manifold and is located adjacent the front side the heat exchanger. A partition extends both longitudinally and transversely within the inlet manifold to hydraulically separate the one flow path from the inlet port while connecting another flow path to at least one other flow path other than the one flow path. 
   As a consequence, a multiple pass, counter-cross current flow is provided in a structure wherein flow guidance within the heat exchanger is readily and inexpensively achieved through the use of a simple baffle and a simple partition. 
   In a preferred embodiment, the cross sectional area of the one flow path is different or greater than the cross sectional area of the other flow path. 
   In one embodiment, at least one other flow path is the another flow path. 
   One embodiment contemplates that at least one of the other flow paths comprises at least two said other flow paths and one of said other flow paths is the another flow path. The partition serves to connect the other flow path to the inlet port and connect, within the inlet manifold, the one of the other flow paths to at least the remaining flow paths. 
   Preferably, the remaining flow paths includes the other flow path. 
   In a preferred embodiment, the partition is defined by a longitudinal partition section extending longitudinally within the inlet manifold and terminating in a transverse partition section ending transversely within the inlet manifold and to the longitudinal partition at a location within the inlet manifold between the ends thereof. 
   In a preferred embodiment, the fins are common to all of the flow paths. 
   In one embodiment, each of the flow paths is defined by individual multiple port tubes aligned, in side by side relation. In another of the contemplated embodiments, each of the flow paths is defined by one or more ports in a single multiple port tube. 
   Other objects and advantages will become apparent from the following specification taken in connection with the accompanied drawings. 

   
     DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a front elevational view of an exemplary embodiment of the heat exchanger; 
       FIG. 2  is a plan view of the heat exchanger; 
       FIG. 3  is a side elevation of the exchanger; 
       FIG. 4  is a perspective view of a modified embodiment of the invention; 
       FIG. 5  is a side elevation of the heat exchanger illustrated in  FIG. 4 ; 
       FIG. 6  is a schematic view of the heat exchanger showing flow there through; 
       FIG. 7  is a somewhat schematic, sectional view of a multiple port, flat tube used in the heat exchanger; 
       FIG. 8  is a perspective view of the embodiment illustrated in  FIGS. 1–3 ; and 
       FIG. 9  is a sectional view of a multiple port, flattened tube. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Exemplary embodiments of a heat exchanger made according to the invention are shown in the drawings and will be described herein in the context of two phase heat exchange, specifically, as a condenser for a refrigerant which may be employed in refrigeration systems (which include air conditioning systems). However, it is to be expressly understood that the invention is not so limited. For example, it can be used as an evaporator rather than as a condenser or even as a gas cooler in so called transcritical refrigerant systems. Further, the heat exchanger can be used in single phase systems where, for example, the heat exchange is gas/gas or gas/liquid with a gas or liquid flowing through the tubes of the heat exchanger and a gas, either for heating or cooling, flows in heat exchange relation through the heat exchanger from its front to its back. Consequently, no limitation to specific usages or specific heat exchange mediums are intended except in as so far as specified in the appended claims. 
   With the foregoing in mind, attention will now be directed to  FIGS. 1–3  and  6  where a first embodiment of the invention is illustrated. 
   As seen in  FIG. 1 , the heat exchanger includes an elongated, flattened, multi-port tube, generally designated  10 , folded upon itself in serpentine fashion to provide a plurality of generally parallel runs  12  which are connected by bends  14 . At one end  16  of the tube  10 , a cylindrical tube  18  is provided. The tube  18  is an inlet manifold and has an elongated slit  19  in it to receive the end  16  thereby establish fluid communication between the ports in the tube  10  and the interior of the inlet manifold  18 . At one end, a fitting block  20  by which the heat exchanger may be connected into a system handling a fluid to be heated or cooled within the heat exchanger. 
   Between adjacent runs  12  of the tube, conventional serpentine fins  24  are located. The fins  24  are bonded as by brazing or soldering to adjacent ones of the runs  12 . 
   At the end  26  of the tube  10 , a slotted, cylindrical tubular outlet manifold  28  is located. The end  26  is received in the slot (not shown) of the outlet manifold  28 . At one end, the outlet manifold  28  may have a fitting block  30  provided with an outlet port  32 . 
   Desirably, at various ones of the bends  14 , elastomeric grommets  34  having through holes  36  are provided. By providing fasteners extending through the through holes  36 , the heat exchanger may be mounted as desired. 
   As best seen in  FIGS. 2 and 3 , the heat exchanger includes a front side  38  and rear side  40 . The direction of gas flow through the heat exchanger, typically air, is indicated by an arrow  42 . 
   As is apparent from  FIGS. 2 and 3 , the embodiment of  FIGS. 1–3  employs a single multi-port tube  10  that extends between the front and back  38  and  40 , respectively. 
   With reference to  FIGS. 2 and 3 , a baffle  44  extends across and blocks the outlet manifold  28  at a location to be described in greater detail hereinafter. 
   In addition, a partition, generally designated  46 , is located within the inlet manifold  18 . The partition  46  includes a longitudinal partition section  48  and transverse partition section  50  at one or both ends of the longitudinal partition section  28 . The longitudinal partition section  48  extends longitudinally within the inlet manifold  18  and terminates in one of the transverse partition sections  50  located at a position between the ends of the inlet manifold  18 . All of the foregoing components are brazed or soldered together. In the case of the serpentine fins  24 , this promotes good heat transfer contact between the fins and the tube  10  as is well known. It also provides for sealing of the ends  16 ,  26  in the respective manifolds  18 ,  28 , and specifically the slots therein to prevent leakage. Furthermore, it provides that the baffle  44  will completely block flow through the outlet manifold  28  at the location at which the baffle  44  is located. Similarly, it assures that the partition  46 , and sections  48  and  50  thereof, provide a space  52  that isolates the flow through the inlet port  22  from flow through the ports of the multi-port tube  10  that are closest to the front  38  of the heat exchanger. 
   In the embodiment illustrated in  FIGS. 1–3 , provision is made for three passes. Referring to  FIG. 6 , a first pass  54  is located immediately adjacent the back or rear  40  of the heat exchanger while a last path  56  is located immediately adjacent the front  38  of the heat exchanger. An intermediate path  60  is located between the first path  54  and the last path  58 . The baffle  44  and partition  48  serve to define the passes. As seen in  FIG. 6 , the transverse partition  50  located between the ends of the inlet manifold  18  is located at the boundary shown schematically at  62  between the first path  54  and the intermediate path  60  while the baffle  44  is located at the boundary shown schematically at  64  between the intermediate path  60  and the last path  58 . These locations are selected to be at the space between adjacent ports of the multi-port tube  10  and as a consequence, flow entering the inlet port  22  flows in the direction of an arrow  66  past the partition  46  to the first path  50  where at it will flow to the outlet manifold  32 . However, it will be blocked from flowing to the outlet port  32  by the baffle  40  and thus be directed through the intermediate path  60  as shown by an arrow  68 . The flow will emerge from the intermediate path  60  to be directed against the partition section  48  which confines the same and redirects it as shown by an arrow  70  to the last path  58 . From there, flow reenters the outlet manifold  28  and travels to the outlet port  32  as indicated by an arrow  72 . 
   That is to say, flow is directed through the first, intermediate and last passes  54 ,  60 , and  58  in that sequence to provide three passes with a first pass being at the rear  40  of the heat exchanger and the last pass being at the front  38  of the heat exchanger. Thus, the back to front flow of the fluid within the tube  10  is counter to the flow of gas indicated by the arrow  42  from the front  38  to the back  40  of the heat exchanger. In addition, because the flow of within the tube  10  is crossing the path of air flow, a cross flow is established, thereby providing a counter-cross flow pattern which those skilled in the art will immediate recognize as maximizing heat exchange efficiency in this type of heat exchanger. It will be particularly observed that the partition  46  is easily inserted in the manifold  18  prior to the application of the fitting block  20  as a simple operation. The longitudinal partition section  48  has the same dimension from side to side as the internal diameter of the manifold  18  while the transverse section  50  may be semi-circular having a radius equal to the internal radius of the manifold  18 . Thus, is only necessary to provide appropriate braze clad or solder clad material on the partition  46  and insert the same to the desired location within the manifold  18  to achieve this desired flow pattern. 
   A perspective view of the embodiment of  FIGS. 1–3  is illustrated in  FIG. 8 .  FIG. 9  illustrates a preferred cross section of the tube  10  used in the embodiment of  FIGS. 1–3 . Various ports  90  are shown as being separated by internal walls  92  of relatively minimal thickness. On the other hand, relatively thick walls  94  may be employed as the boundaries  62 ,  64  separating the various passes. The use of relatively thick walls is preferred at these locations to ensure that a good seal with the baffle  44  or the partition  46  is achieved. Elsewhere, the partitions  92  need only be of sufficient thickness as to provide the desired pressure resistance and transfer of heat to the exterior walls of the tube  10 . Generally speaking, it will be desirable to make the walls as thin as possible commensurate with these goals to minimize weight and realize a material savings. 
   From the foregoing, those skilled in the art will appreciate that a highly efficient multi-pass serpentine heat exchanger with the efficient counter-cross flow feature is provided. Manufacture is simple, particularly in terms of defining the space  52  which isolates the last two passes in the embodiments illustrated from fluid entering the inlet port  22 . Of course, more than three passes may be employed simply by utilizing an additional one or ones of the baffles  44  at the desired locations and by placing one or more additional transverse partition sections  50  at a desired location between the two positions illustrated in  FIG. 2 .

Technology Classification (CPC): 5