Patent Publication Number: US-2009229799-A1

Title: Heat exchanger and airflow therethrough

Description:
RELATED APPLICATIONS 
     This application is a divisional of U.S. patent application Ser. No. 10/801,343 filed on Mar. 15, 2004, which is a continuation of U.S. patent application Ser. No. 10/078,242, filed on Feb. 19, 2002, each of which is expressly incorporated herein in its entirety by reference thereto. 
    
    
     TECHNICAL FIELD 
     The present invention relates to heat exchangers and, more particularly, relates to the flow of air therethrough. 
     BACKGROUND OF THE INVENTION 
     The vapor compression refrigeration cycle is the pattern cycle for a majority of the commercially available refrigeration systems. This thermal transfer cycle is typically accomplished by a compressor, condenser, throttling device and evaporator connected in serial fluid communication with one another. The system is charged with refrigerant which circulates through each of the components to remove heat from the evaporator and transfer heat to the condenser. Thus the evaporator and condenser are commonly referred to as heat exchangers. 
     There is a wide variety of heat exchangers available today. However, the shape and size of the heat exchangers often depends on how the refrigeration cycle is to be used as well as the type of refrigerant to be used. For example, the space where the refrigeration system is to be placed is often limited in size and there are often restraints on the available airflow. Also, the performance of the refrigeration system often limits the types of refrigeration systems which would be acceptable for a particular application. 
     Therefore, there is a need for a low profile heat exchanger which may be used in an economy of space. The new heat exchanger must also maximize the airflow therethrough to provide a more efficient heat exchange. 
     SUMMARY OF THE INVENTION 
     The present invention solves the above-identified problems by providing a low profile heat exchanger which provides a path of multidirectional airflow within the interior of the heat exchanger to provide more efficient heat exchange. 
     Generally described, the heat exchanger of the present invention includes a housing divided into first and second airflow plenums by a coil assembly. The airflow plenums are used to create a more desirable path of airflow. The path of airflow through the housing includes a first portion in a first direction in the first airflow plenum. The first portion of the airflow path defines a cross flow distributed over a portion of the coil assembly. A second portion of the path of airflow defines a flow in a second direction extending from the first airflow plenum, through the coil assembly, and down to the second airflow plenum. A third portion of the airflow path in the first direction defines a second cross flow distributed over a portion of the coil assembly in the second airflow plenum. 
     According to one aspect of the invention the coil assembly is oriented in an angular manner within the housing of the heat exchanger. When the coil assembly is mounted in an angular manner within the housing, the cross-sectional area of the first airflow plenum diminishes as the air flow is distributed in the first airflow plenum. Also, the cross-sectional area of the second airflow plenum increases as the airflow is distributed over the coil assembly toward an outlet in the housing. 
     The foregoing has broadly outlined some of the more pertinent aspects and features of the present invention. These should be construed to be merely illustrative of some of the more prominent features and applications of the invention. Other beneficial results can be obtained by applying the disclosed information in a different manner or by modifying the disclosed embodiments. Accordingly, other aspects and a more comprehensive understanding of the invention may be obtained by referring to the detailed description of the exemplary embodiments taken in conjunction with the accompanying drawings, in addition to the scope of the invention defined by the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         FIG. 1  illustrates a perspective view of a pair of evaporators utilized in combination with a pair of air movers.  FIG. 1  also illustrates a portion of one of the evaporators cut away to show a portion of the elongated segments of the coil assembly. 
         FIG. 2  illustrates a side view of the evaporators and air movers taken along line A-A of  FIG. 1 . 
         FIG. 3  illustrates a cross sectional view of the right evaporator of  FIG. 2 . 
         FIG. 4  illustrates a cross-sectional view of the right evaporator of  FIG. 2  with reversed airflow. 
     
    
    
     DETAILED DESCRIPTION  
     Referring now to the drawings in which like numerals indicate like elements throughout the several views,  FIG. 1  illustrates an exemplary embodiment of a refrigeration system utilizing one embodiment of j evaporators  10  of the present invention. While a particular embodiment of the present invention may be described with reference to a particular heat exchanger application such as an evaporator  10 , it is understood that the present invention may also be adapted for use in a condenser or in a variety of other applications requiring heat transfer. 
     In one embodiment of the present invention, as best shown in  FIG. 1 , a pair of evaporators  10  is positioned on opposite sides of a pair of adjacent air movers  12 . Each of the air movers  12  has a housing  14  mechanically coupled to a housing  20  of each evaporator  10 . Fasteners such as metal strap members  16  may be used to couple the evaporators  10  to the housings  14  of the air movers  12  as shown in  FIG. 2 .  FIG. 2  also illustrates a heater  18  on at least one of the air movers  12  for heating the airflow before the airflow passes through fan blades  19 . Although this particular embodiment includes a pair of air movers  12  in combination with a pair of evaporators  10 , it is within the scope of the present invention to include any number of air movers  12  with any number of evaporators  10 . Also, the orientation of the air movers  12  relative the evaporators  10  is preferably such that the axis of rotation of the air movers  12  is substantially perpendicular to the general direction of the airflow through the evaporators  10 . Moreover, the air movers  12  are preferably oriented relative to the evaporators  10  such that the airflow is first drawn through the evaporators  10 , and then directed downward as best shown in  FIG. 1 . However, the airflow drawn through the evaporators  10  may also be directed upward. 
     For example, the combination of the evaporators  10  and the air movers  12  shown in  FIG. 1  may be used with marine containers (not shown) which are typically used to transport fresh produce. However, fresh produce gives off a significant amount of heat while ripening and, therefore, during transit it is desirable to control the rate of ripening. As a result of the evaporators&#39;  10  extraction of heat and humidity from the airflow through the housings  20 , the downwardly directed airflow then permits cooler and dryer air to contact the fresh produce to prolong or stabilize the rate of ripening. In the event produce in to be transported through extremely cold climates, the heater  18  may instead be operated to warm the airflow through the air mover  12  so that warmer temperatures may be maintained. Thus, the heater  18  is preferably only operated when refrigeration is not needed. 
     As best shown in  FIG. 1 , each housing  20  of the evaporators  10  includes a top  22  and a bottom  24 , two sides  26  and  28 , respectively, and two ends  30  and  32 , respectively. The bottom  24  is preferably configured as a drain pan for condensation. Collectively, the top  22 , bottom  24 , sides  26  and  28 , and ends  30  and  32  define an interior  34  of the housings  20 . Within the interior  34  of each evaporator is a coil assembly  40  of a tubular body extending within each housing  20  for the purpose of providing a heat exchange surface. The coil assembly  40  of each evaporator  10  preferably extends in a serpentine manner the full length L and full width W of the evaporators  10 . Typically, the coil assembly  40  includes a plurality of elongated segments  42  and a plurality of bent end segments  44 .  FIG. 1  illustrates a portion of one of the evaporators  10  cut away to show a portion of the elongated segments  42  of the coil assembly  40  oriented in a transverse manner to the airflow entering and exiting the housing  20  described in greater detail below. 
     A group of elongated segments  42  and bent end segments  44  are combined to form at least one coil row which extends the full length L and width W of the housing  20 . However, it is common to included more than one coil row where one coil row is placed over the top of another coil row. Moreover, the elongated segments  42  and bent end segments  44  of each coil row may cross over one another such that neither of the coil rows has more of a heat load. In the present invention, however, the number of coil rows may be reduced to provide better airflow in the housing  20  without obstructions and to permit the evaporators  10  to be used in smaller spaces. As a result of the airflow through the evaporators  10  of the present invention, as described below, it is within the scope of the present invention to use only one coil row in the interior of each housing  20 . 
     In the preferred embodiment of the present invention, the coil assembly is tilted within the housing  20  as best shown in  FIGS. 2 and 3 . In other words, the coil assembly  40  with preferably only one coil row, or possibly with more than one coil row, is angularly misaligned with the interior surface of at least one of the top  22  or bottom  24  of the housing  20 . The coil assembly  40  in the housing  20  partially defines airflow plenums within the interior  34  of the housing  20 . In  FIG. 2 , on opposite sides of the coil assembly  40  is a first airflow plenum  50  and a second airflow plenum  52 . In the context of  FIGS. 2 and 3 , the first and second airflow plenums  50  ,  52  may be referred to as upper and lower airflow plenums  50 ,  52 , respectively. Portions of the inner surfaces of the sides  26 ,  28  and ends  30 ,  32 , along with either the top  22  or bottom  24 , define the remaining portion of each of the airflow plenums  50  and  52 . Preferably the airflow plenums  50 ,  52  are substantially prismatic where congruent polygons are portions of the ends  30 ,  32  and parallelograms are portions of the sides  26 ,  28 . However, the present invention also contemplates non-faceted surfaces. 
     As shown in  FIGS. 1 and 3 , the end  30  has an airflow inlet  56  to permit airflow into the evaporator  10 , and the end  32  has an airflow outlet  58  to permit airflow to be exhausted from the evaporator  10  and into the air mover. The inlet  56  and outlet  58  are disposed opposite one another on opposing ends of the housing  10 . As best shown in  FIG. 1 , the inlet  56  and outlet  58  are preferably rectangular in shape and extend substantially the full length L of the evaporator  10 . The inlet  56  communicates with the first airflow plenum  50  and the outlet  58  communicates with the second airflow plenum  52 . 
     As best shown in  FIG. 1 , the inlet  56  in the end  30  of the right evaporator  10  is defined by the edges of the top  22 , the two sides  26  and  28 , and an upper edge of the end  30 . Preferably, the outlet  58  is similarly defined by the two sides  26  and  28 , end  32  and the bottom  24 . Preferably, in order to direct the airflow into the first plenum  50  from the exterior, the inlet  56  on the end  30  is positioned closer to the top  22  than the bottom  24  and, in order to exhaust the airflow from the second airflow plenum  52 , the outlet  58  on the end  32  is positioned closer to the bottom  24  than the top  22 . Referring to  FIG. 3 , it can be seen that the inlet  56  and outlet  58  are substantially diagonally disposed to one another. 
       FIG. 3  also best depicts the changing cross section of the airflow plenums  50 ,  52 . The cross-sectional area of the top airflow plenum  50  diminishes as airflow is distributed from the inlet  56  and the cross-sectional area of the bottom airflow plenum  52  increases as the airflow is distributed over the coil assembly  40  toward the outlet  58 . The diminishing cross-sectional area of the top airflow plenum  50  helps to force airflow through the coil assembly as described below. 
     The present invention also includes a path of multi-directional airflow through the housing  20 . The airflow path includes a first portion  60  that begins at end  30  and extends through the first airflow plenum  50  in a first direction. The first portion  60  is a cross flow that is distributed over a portion of the coil assembly  40 . As shown in  FIG. 3 , the airflow in the first airflow plenum  50  is distributed across the upper surface of the coil assembly  40 . The airflow path also includes a second portion  64  defining a flow extending in a second direction through the coil assembly  40 . The second portion  64  of the airflow path begins in the top airflow plenum  50  and ends in the bottom airflow plenum  52 . Fins typically included on the tubular body of the coil assembly  40  may assist in directing the airflow into the second direction. Although the second portion  64  of the airflow path as shown in  FIG. 3  is directed downward, the second portion  64  is commonly referred to as a vertical portion of airflow. The airflow path also includes a third portion  66  which extends through the bottom airflow plenum  52  in the first direction to the opposite end  32  of the housing  20 . The third portion  66  of the airflow path is a second cross flow that is distributed over a portion of the coil assembly  40  through the second airflow plenum  52 . As shown in  FIG. 3 , the airflow is the second airflow plenum  52  is distributed across the underside of the coil assembly  40 . Both the first and third portions  60 ,  66  of the airflow path are commonly referred to as horizontal portions of airflow. Preferably, the horizontal portions of airflow pass over the elongated segments  42  of the coil assembly  40  in substantially a transverse manner. 
     Alternatively, the airflow may be reversed through the evaporator  10  as shown in  FIG. 4 . In such case, preferably the inlet  56  is near bottom  24  on end  32  and the outlet  58  is near the top  22  on end  30 . Also, in this embodiment, the bottom airflow plenum  52  and the top airflow plenum  50  are referred to as the first and second airflow plenums, respectively. Otherwise, evaporator  10  in  FIG. 3  is substantially structurally the same as the evaporator  10  of  FIG. 4 . In  FIG. 4 , the first portion  60  of the path of airflow begins at end  32  and extends through the airflow plenum  52  in a first direction. In this case, the first direction is oriented differently than in  FIG. 3 . The first portion  60  is a cross flow distributed across the bottom surface of the coil assembly  40 . The reversed airflow also includes a second portion  64  in a second direction through the coil assembly  40 . The reversed airflow also includes a third portion  66  which extends through the air plenum  50  in the first direction to the end  30  of the housing  20 . The third portion  66  is a second cross flow distributed over the top surface of the coil assembly  40 . 
     In either embodiment, the airflow in the first direction and the airflow in the second direction are preferably substantially perpendicular to one another. Thus, the coil assembly  40  within the housing  20  is oriented in an angular manner relative the airflow from the inlet  56  in the first direction as well as the airflow toward the outlet  58  in the first direction. The coil assembly  40  is also oriented in an angular manner relative the airflow in the second direction. The angular orientation of the coil assembly  40  is preferred in order to facilitate airflow through the coil assembly  40  and to place the heat load over a wider surface of the coil assembly  40  so that the heat is equally absorbed over the entire surface of the coil assembly  40 . 
     The use of the evaporator  10  as described above constitutes an inventive method of the present invention in addition to the evaporator  10  itself. In practicing the method of the present invention for transferring heat, the steps include receiving airflow into a first airflow plenum  50  as described above. The method then includes distributing the airflow in the first airflow plenum  50  across a portion of the coil assembly  40  in a first direction. The method also includes passing the airflow through the coil assembly  40 . The method then includes the step of distributing the airflow in the second airflow plenum  52  across a portion of the coil assembly  40  in the first direction. Next, the airflow is exhausted from the second airflow plenum  52  to the exterior of the housing  20 . The method of the present invention may also include the step of passing airflow through the heat exchanger  10  without passing refrigerant through the heat exchanger  10  to cool the airflow. In such case, the airflow from the heat exchanger  10  is then warmed such that warm airflow may be provided when warmer temperatures are desired in colder climates or as the process might require. 
     The present invention has been illustrated in relation to particular embodiments which are intended in all respects to be illustrative rather than restrictive. Those skilled in the art will recognize that the present invention is capable of many modifications and variations without departing from the scope of the invention. Accordingly, the scope of the present invention is described by the claims appended hereto and supported by the foregoing.