Patent Publication Number: US-2013240177-A1

Title: Nested heat exchanger

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 61/610,269, filed Mar. 13, 2012, the contents of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention generally relates to heat exchangers. More particularly, this invention relates to a heat exchanger having coolant tubes that overlap. 
     Heat exchangers are widely used in various industries in the form of radiators for cooling motors, engines, and steering, transmission and hydraulic fluids, condensers and evaporators for use in air conditioning systems, and heaters. In their most simple form, heat exchangers include one or more passages through which a fluid flows while exchanging heat with the environment surrounding the passage. In order to efficiently maximize the amount of surface area available for transferring heat between the environment and fluid, the design of a heat exchanger is typically of a tube-and-fin type containing a number of tubes that thermally communicate with fins. The fins enhance the ability of the heat exchanger to transfer heat from the fluid to the environment, or vice versa. Various heat exchanger designs are known in the prior art. Design variations include the manner in which the fluid passage is constructed and the type of fin used. For example, the passage may be composed of one or more serpentine tubes that traverse the heat exchanger in a circuitous manner, or a number of discrete parallel tubes joined, typically brazed, to and between a pair of headers. The fins may be provided in the form of panels having apertures through which the tubes are inserted, or in the form of centers that can be positioned between adjacent pairs of tubes. 
     In traditional serpentine heat exchangers, a refrigerant flows up and down through a tube (coil) across the heat exchanger (the terms “up” and “down” are used herein to refer to the orientation of a heat exchanger to earth, are relative terms that indicate the construction, installation and use of a heat exchanger, and therefore help to define the scope of the invention). The effective rate of heat transfer between the fluid and the outside environment are limited by the amount of coils the are in the heat exchangers. Improvements to heat exchangers are continuously sought to increase the rate of heat transfer. 
     Accordingly, there is a need for a heat exchanger assembly adapted to promote an increased rate of heat transfer between the fluid and the environment surrounding the heat exchanger. 
     BRIEF DESCRIPTION OF THE INVENTION 
     The present invention provides heat exchangers having coils that are nested in order to increase the coolant tube density within the heat exchanger and thereby promote an increased rate of heat transfer between the fluid and the environment surrounding the coils. 
     According to a first aspect of the invention, a heat exchanger assembly includes at least first and second coils adapted to contain a fluid therein and at least two support members securing the coils to each other. Each of the first and second coils are individually formed of at least one tube comprising an inlet at an uppermost extent thereof and an outlet at a lowermost extent thereof and include a vertical column containing a plurality of horizontal rows and a plurality of bends at opposite ends of the horizontal rows and fluidically interconnecting the horizontal rows thereof in series to define a serpentine configuration. The first and second coils are adjacent each other and nested so that the horizontal rows of the first coil are parallel to the horizontal rows of the second coil and at least some of the horizontal rows of the first coil are disposed between adjacent pairs of the horizontal rows of the second coil. 
     According to a second aspect of the invention, a heat exchanger assembly includes at least first and second coils adapted to contain a fluid therein and at least two support members securing the first and second coils together. Each of the first and second coils are individually formed of at least one tube comprising an inlet at an uppermost extent thereof and an outlet at a lowermost extent thereof. Each of the first and second coils comprising a vertical column containing a plurality of horizontal rows and a plurality of bends at opposite ends of the horizontal rows and fluidically interconnecting the horizontal rows thereof in series to define a serpentine configuration through which the fluid flows downward from the inlet thereof to the outlet thereof. The first and second coils are adjacent each other and nested so that the horizontal rows of the first coil are parallel to the horizontal rows of the second coil and at least some of the horizontal rows of the first and second coils are interdigitated with each other. 
     According to a third aspect of the invention, a heat exchanger assembly includes at least first and second coils adapted to contain a fluid therein and at least two support members securing the first and second coils to each other. Each of the first and second coils are individually formed of at least one tube comprising an inlet at an uppermost extent thereof and an outlet at a lowermost extent thereof. Each of the first and second coils comprising a vertical column containing a plurality of horizontal rows and a plurality of bends at opposite ends of the horizontal rows and fluidically interconnecting the horizontal rows thereof in series to define a serpentine configuration through which the fluid flows downward from the inlet thereof to the outlet thereof. The first and second coils are adjacent each other and nested so that the horizontal rows of the first coil are parallel to the horizontal rows of the second coil and at least some of the horizontal rows of the first and second coils are interdigitated with each other. The heat exchanger assembly includes at least one vertical section fluidically connecting the outlet of the first coil to the inlet of the second coil, wherein the fluid flowing within the heat exchanger assembly travels from the outlet of the first coil, up through the vertical section, and into the inlet of the second coil. 
     A technical effect of the invention is the ability to provide an increased rate of heat transfer in a heat exchanger without increasing the size of the heat exchanger. In particular, it is believed that, by nesting the coils, the amount of coils within the heat exchanger may be increased without increasing the size of the heat exchanger thereby promoting an increased rate of heat transfer between the fluid and the environment surrounding the coils. 
     Other aspects and advantages of this invention will be better appreciated from the following detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  includes side and end views representing a coil in accordance with an aspect of the invention. 
         FIG. 2  is a perspective view representing a heat exchanger assembly in accordance with an aspect of the invention. 
         FIG. 3  is an end view representing the heat exchanger assembly of  FIG. 2 . 
         FIG. 4  is a bottom view representing the heat exchanger assembly of  FIG. 3 . 
         FIG. 5  is a perspective view representing a heat exchanger assembly in accordance with an aspect of the invention. 
         FIG. 6  is an end view representing the heat exchanger assembly of  FIG. 5 . 
         FIG. 7  is a bottom view representing the heat exchanger assembly of  FIG. 6 . 
         FIGS. 8 and 9  include top, end, and side views representing support members in accordance with an aspect of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIGS. 2 through 9  represent a nested heat exchanger assembly  10  according to non-limiting embodiments of the present invention. The heat exchanger assembly  10  is adapted to contain a fluid within coils  12  for promoting heat exchange between the fluid and the environment surrounding the coils  12 . Suitable fluids include, but are not limited to, CO 2 , propane, and other gasses and liquids commonly used for heat exchange. The heat exchanger assembly  10  may be formed of any suitable material, for example, ferris metal, non-ferris metal, plastic, and glass. For convenience, consistent reference numbers are used throughout the figures to identify the same or functionally equivalent elements. To facilitate the description of the heat exchanger assembly  10 , the terms “front,” “back,” “side,” “above,” “below,” etc., are used herein to refer to the orientation of a heat exchanger to earth, are relative terms that indicate the construction, installation and use of a heat exchanger, and therefore help to define the scope of the invention. 
     The heat exchanger assembly  10  is represented in  FIG. 2  as comprising four coils  12  connected by an inlet assembly  22  at the top of the heat exchanger assembly  10 , or uppermost extent of the coils  12 , and an outlet assembly  24  at the bottom of the heat exchanger assembly  10 , or lowermost extent of the coils  12 .  FIGS. 2 ,  3 , and  4  represent perspective, end, and bottom end views of a first embodiment of the heat exchanger assembly  10 , respectively. 
     Each of the coils  12  are individually formed of at least one tube  14  defining a serpentine pattern as represented in  FIG. 1 . Preferably, the coils  12  are each formed from a single continuous tube  14 . The tubes  14  comprise an inlet at an uppermost extent of the coils  12  and an outlet at a lowermost extent of the coils  12 . The coils  12  are defined by a vertical column containing a plurality of horizontal rows  15  spanning the length of the heat exchanger assembly  10  and a plurality of bends  16  at opposing ends of the heat exchanger assembly  10  and fluidically interconnecting the horizontal rows  15  thereof in series to define a serpentine configuration. The horizontal rows  15  and bends  16  form the serpentine pattern, as represented in  FIG. 1 , defined by an end of a first horizontal row spanning the length of the heat exchanger assembly  10  being fluidically connected to a first end of a second horizontal row by a first bend  16 . The second horizontal row  15  being closer to the lowermost extent of the coil  12  than the first horizontal row  15 . The serpentine pattern is continued by fluidically connecting a second end of the second horizontal row  15  to an end of a third horizontal row by a second bend  16 . The third horizontal row  15  being closer to the lowermost extent of the coil  12  than the second horizontal row  15 . The serpentine pattern is continued until reaching the outlet at the lowermost extent of the coil  12 . 
     The bends  16  on the ends of the coil  12  are arranged on opposite ends of the coil  12 . The bends  16  are angled down toward the lowermost extent of the coils  12 . Preferably, the bends  16  on opposite ends of the coil  12  are and are disposed in planes that are not horizontal and not parallel to each other to define an angle theta (θ) to one another, as represented in  FIG. 3 . Preferably, the angle theta (θ) is about 60 degrees. However, one skilled in the art will appreciate that the angle theta (θ) is dependent on the outside diameter, wall thickness, and formability of the tubes  14 . 
       FIGS. 2 and 3  represent the heat exchanger assembly  10  as comprising four coils  12  arranged in adjacent vertical columns. The horizontal rows  15  of each coil  12  are positioned parallel to the horizontal rows  15  of the other coils  12 . It will be appreciated that the heat exchanger assembly  10  may comprise any number of coils  12 . In operation, a fluid enters the inlet assembly  22  at the uppermost extent of the coils  12 , the fluid enters each of the four coils  12  generally simultaneously, and travels downward fluidically in parallel through the coils  12  to the outlet assembly  24  at the lowermost extent of the coils  12  where the fluid may exit the heat exchanger assembly  10 . A detailed bottom view of an end of the heat exchanger assembly  10  is represented in  FIG. 4 . The tubes  14  of the coils  12  are represented as being secured to each other by support members  18  at both ends of the heat exchanger assembly  10 . The support members  18  may comprise flanges  26  to secure the heat exchanger assembly to another structure, for example, to a frame of a motor vehicle. The flanges  26  may be constructed in any shape suitable for the intended application. 
       FIGS. 5 ,  6 , and  7  represent perspective, end, and bottom end views of an alternative embodiment of the heat exchanger assembly  10 , respectively. In this embodiment, the heat exchanger assembly  10  is represented as comprising three vertical sections  28  fluidically connecting the outlets of coils  12  at the lowermost extent of the coils  12  to the inlets of adjacent coils  12  at the uppermost extent of the adjacent coils  12 . In operation, the fluid travels through the entirety of one of the coils  12  prior to entering the next adjacent coil  12  and thereby traveling through the coils  12  fluidically in series rather than through all of the coils  12  at once fluidically in parallel, as was the case in the embodiment of  FIGS. 2-4 . The fluid enters the inlet assembly  22  at the uppermost extent of a first of the coils  12  and travels downward through the first coil  12 . Once the fluid reaches the lowermost extent of the first coil  12 , the fluid then travels from the outlet of the first coil  12  up through one of the vertical sections  28  into the inlet of a second coil  12 . This process is repeated until the fluid travels through the entirety of all of the coils  12 . The fluid can then exit a last of the coils  12  through the outlet assembly  24 . In addition to the two embodiments of the invention described above, it is foreseeable that the heat exchanger assembly  10  can comprise a combination of the above arrangements of the coils  12  wherein the fluid travels through some of the coils  12  in series, as in the embodiment of  FIGS. 5 through 7 , and through other coils  12  generally simultaneously, as in the embodiment of  FIGS. 2-4 . 
     In  FIGS. 3 and 6 , horizontal rows of the coils  12  are represented as being nested, that is, having at least some of the horizontal rows  15  on a first coil  12  disposed between adjacent pairs of the horizontal rows  15  of a second coil  12  adjacent to the first coil  12 . Preferably, a plurality of the horizontal rows  15  on the first coil  12  are interdigitated with the horizontal rows  15  of the second coil  12 . It is believed that fitting the coils  12  together in this manner allows more of the tubes  14  to fit in the same amount of space thereby promoting an increased rate of heat transfer between the fluid within the coils  12  and the environment surrounding the coils  12  relative to other heat exchangers of equal size. The heat exchanger assembly  10  may be used for both standard and high pressure applications having an appropriate tube wall material thickness. The tubes  14  can be made of any suitable material including, but not limited to, steel, stainless steel, copper, polymer, glass or aluminum tubes. The tubes  14  can be made to have a suitable outside diameter, for example, in a range of about 0.2 inch to about one inch (about 5 to about 25 millimeters), though other dimensions are foreseeable. As a non-limiting example, it is believed that a tube  14  formed of carbon steel having an outside diameter of about 0.375 inch (about 9.5 mm) and a wall thickness of about 0.028 inch (about 0.71 mm) can survive operating pressures up to about 2,200 psi (15.2 Mpa). Connectors (not shown) may be attached to the ends of the coils  14  (or inlet assembly  22  and outlet assembly  24 ), for example, copper connectors. The heat exchanger assembly  10  may further be modified for particular applications by selecting the number of tubes  14  in the coil  12 , selecting the number of columns of the tube  14  in the coil  12 , and/or selecting the radius and the degree of twist on the bends  16  of the tube  14 . 
     To improve heat transfer, one or more fins  20  may be attached to the coils  12 , as represented in  FIGS. 2 ,  5 , and  7 . Various shapes of the fins  20  may be used to increase performance of the heat exchanger assembly  10  including, but not limited to, straight, corrugated and lanced fin shapes. The fins  20  may be made of any suitable material such as steel, stainless steel, copper, aluminum, galvanized steel or a polymer material. Further, the fins  20  may have a finish coating such as a hydrophilic, latex, or electrodeposition coating. However, depending on the application, it may be desirable to limit the number of fins  20  attached to the coils  12 . It is believed that addition of the fins  20  to the heat exchanger assembly  10  increases the likelihood of debris from an outside environment accumulating around the coils  12  which may act to insulate the coils  12  reducing the rate of heat transfer of the heat exchanger assembly  10 . 
       FIGS. 7 and 8  include top, side, and back views representing various flange  26  arrangements of the support member  18 . As represented, the support member  18  may comprise extrusions  30  that encircle and contact the tubes  14  of the coils  12 . The extrusions  30  may also be formed on the fins  20  (not shown). The extrusions  30  allow for increased surface area contact between the tubes  14  and support member  18  thereby increasing thermal transfer. The extrusions  30  may further promote accurate fin spacing and support member alignment. 
     While the invention has been described in terms of specific embodiments, it is apparent that other forms could be adopted by one skilled in the art. For example, the physical configuration of the heat exchanger assembly  10  could differ from that shown, and materials and processes other than those noted could be used. Therefore, the scope of the invention is to be limited only by the following claims.