Patent Publication Number: US-7908883-B2

Title: Refrigerator accelerated heat exchanger

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application represents a continuation-in-part of U.S. patent application Ser. No. 11/644,558 entitled “Accelerated Heat Exchanger” filed Dec. 22, 2006, pending. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention pertains to the art of refrigerators and, more specifically, to tube and fin-type heat exchangers used in domestic refrigerators. 
     2. Description of the Related Art 
     Refrigerators typically include one or more enclosures or chambers for storing food or other articles to be cooled or frozen. The refrigerator housing about these enclosures includes two intersecting fluid circuits: a refrigerant circuit and a cooling air circuit. The refrigerant circuit generally includes a compressor, a condenser and an evaporator with tubing between these elements to permit the flow of the refrigerating fluid. The condenser essentially exchanges heat from the refrigerator interior to the outside air. The cooling air circuit typically includes passageways for air to travel between the enclosures, the evaporator and an impeller, such as a fan, for causing air to flow within the air circuit. These two circuits intersect at the evaporator, which enables the transfer of heat from the cooling air to the refrigerating fluid. 
     Evaporators for refrigerators typically include a tube and fin-type arrangement wherein a serpentine tube containing the refrigerating fluid passes through the evaporator, with air paths over the serpentine tube defined by the longitudinal length of these fins. One example of such a tube and fin-type evaporator is shown in U.S. Pat. No. 3,745,786, issued Jul. 17, 1978. 
     It has been found to be desirable to increase the efficiency of such tube and fin-type evaporators and to decrease the size of the evaporator. An evaporator can be made more compact by, for example, increasing the density of the fins and/or by increasing the inlet flow velocity of the cooling air. However, if fin density is increased, the normal frost build-up on the fins can clog and close the flow passages for cooling air. With such an arrangement, more frequent defrosting is required, which significantly increasing energy consumption of the appliance. Similarly, increasing the flow velocity of the cooling air into the evaporator, such as by increasing the fan speed, results in more energy consumption and increases the overall noise level of the appliance. 
     Other previous heat transfer enhancement methods have been found to be disadvantageous when applied to refrigerators. For example, louvered or lanced fins are considered less effective than needed because of the relatively low flow velocities of cooling air in refrigerators and the frost build-up on the louvers. Additionally, evaporators having trapezoidally shaped fins, such as the evaporator shown in U.S. Pat. No. 5,157,941 issued Oct. 27, 1992, have been found difficult to manufacture. 
     In a manner directly analogous to evaporators, condensers in refrigerators also function to perform heat exchange operations. With respect to refrigerator condenser heat exchangers, efforts to improve heat transfer include extending secondary heat transfer surfaces as set forth in U.S. Pat. Nos. 3,785,168 and 2,359,926, for example. Additionally, it is known to provide a refrigerator with a condenser having a folded condenser tube and wire fins as seen in U.S. Pat. No. 5,502,983. However, as with fin-type evaporators, a more compact design closes the flow passages and slows the flow of cooling air through the condenser. 
     Therefore, there exists a need for heat exchanger for a refrigerator evaporator or condenser having an improved efficiency which is simple and inexpensive to manufacture. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a refrigerator tube and fin-type accelerated airflow heat exchanger having a dividing wall that bifurcates the heat exchanger into first and second air flow passages. Fins on the heat exchanger include apertures therein, allowing for both horizontal and vertical movement of air through the air flow passages. The dividing wall extends through the heat exchanger at an angle, decreasing the cross-sectional diameter of both the first and second airflow passages and resulting in accelerated movement of air through the air flow passages. The heat exchanger may be utilized in a condenser assembly and/or an evaporator assembly. The evaporator assembly may be situated along the back, bottom, top or sidewalls of the freezer compartment of the refrigerator, and preferably includes a fan to aid in air flow through the refrigerator&#39;s cooling air circuit. The condenser assembly is situated within a machine compartment of the refrigerator and includes a fan to aid in air flow through condenser coils. 
     In use, air from either or both of the fresh food or freezer compartments is directed into the first air flow passage of the heat exchanger for cooling, and upon exiting, is directed by curved baffles into the second airflow passage for further cooling. Cooled air exiting the second airflow passage is then directed into either or both of the fresh food or freezer compartments. 
     Additional objects, features and advantages of the present invention will become more readily apparent from the following detailed description of preferred embodiments when taken in conjunction with the drawings wherein like reference numerals refer to corresponding parts in the several views. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a cross-sectional right side view of a refrigerator including a first arrangement of an evaporator assembly of the present invention; 
         FIG. 2  shows a cross-sectional front side view of the refrigerator of  FIG. 1 ; 
         FIG. 3  shows a partial perspective view of an accelerated heat exchanger of the present invention; 
         FIG. 4  shows a cross-sectional right side view of a refrigerator including a second arrangement of the evaporator assembly of the present invention; 
         FIG. 5  shows a cross-sectional front side view of the refrigerator of  FIG. 4 ; 
         FIG. 6  shows a cross-sectional top side view of the refrigerator of  FIG. 4 ; 
         FIG. 7  shows a cross-sectional right side view of a refrigerator including a third arrangement of the evaporator assembly of the present invention; 
         FIG. 8  shows a cross-sectional front side view of the refrigerator of  FIG. 7 ; 
         FIG. 9  shows a cross-sectional top side view of the refrigerator of  FIG. 7 ; 
         FIG. 10  shows a cross-sectional right side view of a refrigerator including a fourth arrangement of the evaporator assembly of the present invention including an alternative heat exchanger; 
         FIG. 11  shows a partial perspective view of the heat exchanger of  FIG. 10 ; 
         FIG. 12  shows a partial cross-sectional view of a heat exchanger of the present invention including a divider wall comprised of flexible polymer tubes; 
         FIG. 13  shows a cross-sectional top view of an alternative heat exchanger having two dividing walls; and 
         FIG. 14  shows a cross-sectional right side view of a refrigerator including a heat exchanger having a front-to-back flow arrangement. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     With initial reference to  FIG. 1 , a refrigerator  2  includes a cabinet  4  housing two food storage cavities, a first upper cavity  6  and a second lower cavity  8 , for storing food or other articles to be cooled or frozen. Cavities  6  and  8  are closed by doors  12  and  14 , respectively. In a preferred embodiment, upper cavity  6  constitutes a freezer compartment and lower cavity  8  defines a fresh food compartment. Refrigerator  2  includes an air flow circuit having a condenser assembly  16 , a compressor  18 , an evaporator assembly  22  and a sealed refrigerant system including tube  26  for connecting these elements. In a manner known in the art, tube  26  contains a refrigerant fluid. Additionally, the air flow circuit preferably includes a condenser fan  28 . In accordance with the invention, evaporator assembly  22  includes a tube and fin-type accelerated heat exchanger  29  which will be detailed more fully below. 
     In a first arrangement shown in  FIGS. 1 and 2 , cooled air circulates from evaporator assembly  22  through an air flow channel  30  to vents  32 - 34 . More specifically, a portion of air circulating from evaporator assembly  22  flows through air flow supply channel  30  to vent  33 , and through vent  33  into fresh food compartment  8 . The remaining portion of air flows through vent  34  to an air flow channel  36  in door  12 , and out a top vent  38  in freezer compartment  6 . As best seen in  FIG. 2 , air circulates through freezer compartment  6  before exiting via vents  32  into air flow return channel  30 . A fan  40  is employed to cause movement of the cooling air within the circuit. Although depicted as being directly adjacent evaporator assembly  22 , fan  40  may be located anywhere within the air flow circuit, as long as it is effective in directing air through the system. 
     As can be seen in  FIG. 2 , air exits fresh food compartment  8  through a vent  42  into airflow return channel  31 , and then through vent openings  43  in order to circulate through heat exchanger  29  of evaporator assembly  22 . The air is cooled by heat exchanger  29  before exiting through vents  32  into air flow supply channel  30  as described above. Preferably, curved baffles  44  direct circulating air cooled from a first air flow passage  46  of heat exchanger  29  into a second air flow passage  48  of heat exchanger  29 . The passageways between heat exchanger  29  and the vents of the cooling air circuit can be located and dimensioned according to the specific configuration desired for refrigerator  2 . Controls, such as damper valve  49 , may be utilized to permit control of the temperature conditions within cavities  6  and  8  as is well known in the art. 
       FIG. 3  will now be referenced in detailing the structure of heat exchanger  29 . Heat exchanger  29  includes a plurality of cooling fins  50  through which a serpentine tube portion  51  of refrigerant tube  26  repeatedly passes. This tube and fin arrangement is preferably mounted in a close fitting housing  52  (shown partially removed) which is open at either end to the cooling air circuit passageway or conduit. It should be understood that housing  52  may be comprised, all or in part, by a refrigerator liner or refrigerator walls. In the embodiment shown, fins  50  are rectangular in shape, equally spaced apart and parallel. However, it should be understood that various types and spacing of fins may be utilized within the context of the present invention, such as split fins, circular fins, spinal fins, spiral fins, etc. Additionally, fins  50  are preferably constructed from a heat conducting metal, such as aluminum, and are relatively thin compared to the length and width of tube  26  in heat exchanger  29 . 
     Housing  52  includes apertures  54  therein for receiving serpentine tube  51  and may additionally include collars  56  projecting from the periphery of apertures  54 . Fins  50  are formed with slots  58  therein for receiving serpentine tube  51 . In addition to retaining tube  51 , slots  58  serve the purpose of allowing for horizontal or lateral air flow within heat exchanger  29 . In preferred embodiments, serpentine tube  51  is inserted into slots  58  such that a single length of serpentine tube  51  may be employed in evaporator assembly  22 . Alternatively, multiple lengths of tubes may be utilized and connected by return bends at each end (not shown). Other types of apertures, such as perforations  60 , may be utilized in addition to slots  58  to further facilitate lateral movement of air within heat exchanger  29 . 
     A stepped dividing wall  70  partitions heat exchanger  29  into first and second air flow passages  46  and  48  and creates gradually narrowing passageways. In passing through first and second air flow passages  46  and  48 , the velocity of cooling air increases as the dimensions of the enclosures, as determined by the dividing wall  70 , decrease. More specifically, dividing wall  70  is positioned at an angle with respect to fins  50 . The resultant gradual narrowing of first air flow passage  46  in the lateral direction accelerates air flow in the vertical or y direction through heat exchanger  29 . Slots  58  and perforations  60  allow for passage of air within heat exchanger  29  in the horizontal or x direction. Likewise, the gradual narrowing of the second air flow passage  48  accelerates air flow in the y′ direction, while slots  58  and  60  allow for passage of air within the x′ direction. Although shown as stepped, dividing wall  70  may be straight or may be in any other form, so long as divider wall  70  narrows the first and second air flow passages sufficient to cause acceleration of air there through. The length and angle of divider wall  70  may be chosen to obtain the air flow desired within a particular refrigerator system. In one embodiment shown in  FIG. 12 , dividing wall  70  is comprised of flexible polymer tubes  71 , each containing a thermal mass, such as iron filings or a water and alcohol mixture, to provide thermal storage with or without phase change. In this configuration, dividing wall  70  may be arranged parallel to the air flow through heat exchanger  29 . 
     In the arrangement shown in  FIG. 1 , evaporator assembly  22  is located behind a back wall  72  of enclosure  6 , and preferably extends substantially the full width of back wall  72 . In this arrangement, the fan  40  is mounted directly adjacent an end portion of dividing wall  70  between the first and second air flow passages  46  and  48 . However, it should be understood that the location of evaporator assembly  22 , as well as fan  40  and baffles  44 , may be altered without departing from the current invention. In an alternative arrangement shown in  FIGS. 4-6 , a refrigerator  102  includes two food storage cavities, a freezer compartment  106  and a fresh food compartment  108 , which are closed by doors  112  and  114 , respectively. Refrigerator  102  includes an air flow circuit having a condenser  116 , a compressor  118 , an evaporator assembly  122 , a sealed refrigerant system including fluid tube  126  for connecting these elements, and a condenser fan  128 . In accordance with the invention, evaporator assembly  122  also includes heat exchanger  29  located adjacent a bottom wall  130  of freezer compartment  106 , and preferably extending substantially the full width of bottom wall  130 . 
     In the air flow circuit depicted in  FIGS. 4-6 , cooled air circulates from evaporator assembly  122  through vents  132 - 134 . More specifically, a portion of air circulating from evaporator assembly  122  flows through vent  133  into fresh food compartment  108 . The remaining portion of air flows through vent  134  to an air flow channel  136  in door  112 , and out a top vent  138  in freezer compartment  106 . Air circulates through freezer compartment  106  before exiting via vent  132 . A fan  140  is employed to cause movement of the cooling air within the circuit. As best seen in  FIG. 5 , air exits fresh food compartment  108  through a vent  142 , and circulates through heat exchanger  29  where it is cooled before exiting through vents  133  and  134  as described above. Preferably, curved baffles  144  direct circulating air cooled from the first air flow passage  46  of heat exchanger  29  into the second air flow passage  48  of heat exchanger  29 . 
     In a third arrangement shown in  FIGS. 7-9 , a refrigerator  202  includes two food storage cavities, a freezer compartment  206  and a fresh food compartment  208 , which are closed by doors  212  and  214 , respectively. Refrigerator  202  includes an air flow circuit having a condenser  216 , a compressor  218 , an evaporator assembly  222 , a sealed refrigerant system including fluid tube  226  for connecting these elements, and a condenser fan  228 . In accordance with the invention, evaporator assembly  222  also includes heat exchanger  29  located adjacent a back wall  230  of freezer compartment  206 , and preferably extending substantially the full width of back wall  230 . As best seen in  FIGS. 7 and 8 , air exits fresh food compartment  208  through a vent  233  and enters an intake channel  234 . Air is then directed by channel  234  to a vent  238  where it is directed through heat exchanger  29 . A fan  240  is employed to cause movement of the cooling air within the circuit. Preferably, curved baffles  244  direct circulating air cooled from a first air flow passage  46  of heat exchanger  29  into a second air flow passage  48  of heat exchanger  29 . A portion of the cooled air from heat exchanger  29  exits through an exhaust channel  246 , where the air is directed through a vent  248  into fresh food compartment  208 . The remaining air from heat exchanger  29  exits through a vent  250  and circulates through freezer compartment  206 . 
     In a fourth arrangement shown in  FIG. 10 , a refrigerator  302  having freezer and fresh food compartments  306  and  308  includes an evaporator assembly  322 . Evaporator assembly  322  utilizes a second embodiment of the heat exchanger of the present invention indicated at  29 ′, having first and second air flow passages  46 ′ and  48 ′. Heat exchanger  29 ′ includes a plurality of cooling fins  50 ′ through which a serpentine tube portion  51 ′ repeatedly passes. As seen clearly in  FIG. 11 , a planar dividing wall  70 ′ bifurcates heat exchanger  29 ′ and creates gradually narrowing passageways that serve to accelerate air flow within heat exchanger  29 ′. Preferably, a fan  340  and curved baffles  344  aid in circulating air within evaporator assembly  322 . A side wall  350  extending from divider wall  70 ′ partially defines both an inflow channel  352  and an exhaust channel  354 . The length and angle of divider wall  70 ′, as well as the length of side wall  350 , may be chosen to obtain the air flow desired within a particular refrigerator system. 
     In a fifth alternative arrangement shown in  FIG. 13 , a refrigerator  404  having a freezer compartment  406  closed by a door  412  includes an alternative evaporator assembly  422  extending substantially the entire width of a top wall of freezer compartment  406 . Evaporator assembly  422  includes a heat exchanger  429  having first and second dividing walls  470 ,  471  for partitioning heat exchanger  429  into first and second inflow passageways  474 ,  475  and an exhaust passageway  476 . With this configuration, air flowing into freezer compartment  406  is directed through first and second inflow passageways  474  and  475  to exhaust passageway  476 , and subsequently directed out of freezer compartment  406 . 
     In a sixth arrangement depicted in  FIG. 14 , a refrigerator  504  includes a freezer compartment  506  and a fresh food compartment  508  which are closed by doors  512  and  514 , respectively. Refrigerator  504  includes an air flow circuit having a condenser  516 , a compressor  518 , an evaporator assembly  522 , a sealed refrigerant system including fluid tube  526  for connecting these elements, and a condenser fan  528 . In accordance with the invention, evaporator assembly  522  also includes a heat exchanger  529  located adjacent a back wall  530  of freezer compartment  506 . In this configuration, heat exchanger  529  includes longitudinally extending first and second airflow passageways  544  and  546  created by a dividing wall  570 . This longitudinally extending dividing wall  570  creates a front-to-back air flow configuration whereby inlet air and outlet air are in-line with one another. 
     At this point, it should be understood that the present invention is not limited to any particular air flow circuit arrangement, but instead enables the efficient circulation of air within many different types of systems. Additionally, although described with reference to refrigerator evaporator assemblies, it should be readily understood that the heat exchanger of the present invention could be equally applied to condenser assemblies. Furthermore, it should be readily understood that various changes and/or modifications can be made to the invention without departing from the spirit thereof. For instance, the invention is not limited to the fin arrangements shown, but can incorporate many different fin arrangements, so long as the air flow within the heat exchanger is not wholly restricted by the fins in the horizontal and vertical directions. In general, the invention is only intended to be limited by the scope of the following claims.