Abstract:
A refrigerated merchandiser includes a case defining a product display area and an air passage separate from the product display area. The case includes a rear wall separating in part the product display area from a vertical portion of the air passage. The rear wall includes apertures near a lower portion of the product display area. The apertures communicate between the vertical portion of the air passage and the lower portion of the product display area. The refrigerated merchandiser also includes a fan positioned in the air passage to generate an airflow through the passage and an evaporator positioned in the vertical portion of the air passage adjacent the rear wall and at an oblique angle to allow the airflow to pass through the evaporator, through the apertures, and into the lower portion of the product display area.

Description:
FIELD OF THE INVENTION  
       [0001]     This invention relates generally to refrigerated merchandisers, and more particularly to medium-temperature refrigerated merchandisers.  
       BACKGROUND OF THE INVENTION  
       [0002]     In conventional practice, supermarkets and convenience stores are equipped with refrigerated merchandisers, which may be open or provided with doors, for presenting fresh food or beverages to customers while maintaining the fresh food and beverages in a refrigerated environment. Typically, cold, moisture-bearing air is provided to a product display area of the merchandiser by passing an airflow over the heat exchange surface of an evaporator coil, or evaporator. A suitable refrigerant is passed through the evaporator, and as the refrigerant evaporates while passing through the evaporator, heat is absorbed from the air passing through the evaporator. As a result, the temperature of the air passing through the evaporator is lowered for introduction into the product display area of the merchandiser.  
         [0003]     Such a prior-art refrigerated merchandiser  10  is shown in  FIG. 1 . The merchandiser  10  includes a case  14  generally defining an interior bottom wall  18 , an interior rear wall  22 , and an interior top wall  26 . The area bounded by the interior bottom wall  18 , interior rear wall  22 , and the interior top wall  26  defines a product display area  30 , in which the fresh food and/or beverages are stored on one or more shelves  32 . The case  14  includes an open front face to allow customers access to the fresh food and/or beverages stored in the case  14 .  
         [0004]     The case  14  also generally defines an exterior bottom wall  34  adjacent the interior bottom wall  18 , an exterior rear wall  38  adjacent the interior rear wall  22 , and an exterior top wall  42  adjacent the interior top wall  26 . A lower flue  46  is defined between the interior and exterior bottom walls  18 ,  34  to allow for substantially horizontal airflow throughout the lower flue  46 . The interior bottom wall  18  includes an opening  50  to communicate with the lower flue  46  to allow surrounding air to be drawn into the lower flue  46 . A rear flue  54  is defined between the interior and exterior rear walls  22 ,  38  and is fluidly connected with and adjacent to the lower flue  46 . The rear flue  54  allows for substantially vertical airflow throughout the rear flue  54 . An upper flue  58  is defined between the interior and exterior top walls  26 ,  42  and is fluidly connected with and adjacent to the rear flue  54 . The upper flue  58  allows for substantially horizontal airflow throughout the upper flue  58 . The interior top wall  26  includes an opening  62  to communicate with the upper flue  58  to allow airflow in the upper flue  58  to be discharged from the upper flue  58 . When combined, the lower flue  46 , the rear flue  54 , and the upper flue  58  comprise an air passage separate from the product display area  30 .  
         [0005]     The refrigerated merchandiser  10  also includes some components of a refrigeration system (not entirely shown) therein. One or more fans  66  are located within the lower flue  46  toward the back of the case  14  to generate an airflow through the lower, rear, and upper flues  46 ,  54 ,  58 . A conventional round-tube plate-fin evaporator  70  is located within the rear flue  54  toward the bottom of the case  14 . The evaporator  70  is positioned downstream of the fans  66  such that the airflow generated by the fans  66  passes through the evaporator  70 . The fans  66  may also be positioned upstream of the evaporator  70 . The refrigeration system may also include other components (not shown), such as one or more compressors, one or more condensers, a receiver, and one or more expansion valves, all of which may be remotely located from the refrigerated merchandiser  10 .  
         [0006]     The evaporator  70  is configured to receive a liquid refrigerant from the receiver. As is known in the art, the liquid refrigerant is evaporated as it passes through the evaporator  70  as a result of absorbing heat from the airflow passing through the evaporator  70 . Consequently, the temperature of the airflow passing through the evaporator  70  decreases as it passes through the evaporator  70 . The heated, or gaseous refrigerant then exits the evaporator  70  and is pumped back to the remotely located compressor(s) for re-processing into the refrigeration system.  
         [0007]     With reference to  FIG. 1 , the interior rear wall  22  includes a plurality of apertures  74  formed therein. The apertures  74  are centrally located in the interior rear wall  22 , and fluidly connect the product display area  30  and the rear flue  54 . The apertures  74  allow some of the refrigerated air in the rear flue  54  to exit the rear flue  54  and enter the product display area  30 . Products located in the product display area  30  may then be cooled by the refrigerated air.  
         [0008]     The remaining portion of the refrigerated airflow that does not pass through the apertures  74  is routed vertically through the rear flue  54 , and horizontally through the upper flue  58  before being discharged from the upper flue  58  via the opening  62  in the interior top wall  26 . After being discharged from the opening  62  in the interior top wall  26 , the refrigerated airflow moves downwardly along the open front face of the refrigerated merchandiser  10  before being drawn back into the opening  50  in the interior bottom wall  18  for re-use by the fans  66 . This portion of the refrigerated airflow is known in the art as an air curtain  78 . The air curtain  78 , among other things, helps maintain the air temperature in the product display area  30  within a standard temperature range of 32° F. to 41° F. determined by the Food and Drug Administration (“FDA”) Food Code for potentially hazardous foods.  
         [0009]     As shown in  FIG. 1 , the size of the conventional round-tube plate-fin evaporator  70  often requires the fans  66  to be positioned in the lower flue  46  beneath the product display area  30 . As a result, the fans  66  occupy valuable space in the merchandiser  10  that could otherwise be used for storing additional food and/or beverage products. Further, spilled product from the product display area  30  may come into contact with the fans  66 , thus making cleanup of the merchandiser  10  more difficult.  
         [0010]     Also, in some prior-art refrigeration cases (not shown), the evaporator is located in the lower flue along with the fans beneath the product display area of the merchandiser. As a result, complex ducting structure is usually required in the rear flue to route the airflow passing through the evaporator to different regions within the product display area. Also, spilled products from the product display area may come into contact with the evaporator, thus making cleanup of the merchandiser more difficult.  
         [0011]     In conventional practice, evaporators  70  utilized in medium-temperature refrigeration merchandisers  10 , such as those commonly used for displaying produce, meats, milk and other dairy products, or beverages in general, generally operate with refrigerant temperatures well below the freezing point of water (i.e., 32° F.). Further, the airflow generally exits the evaporators  70  at a temperature below the freezing point of water. Thus, during operation of the merchandisers  10 , frost often forms on the evaporators  70  as a result of moisture in the air condensing onto the evaporator  70  and freezing.  
         [0012]     Such medium-temperature refrigerated merchandisers  10  operate in this manner because the refrigerated products, like produce, meats, and dairy products, must be maintained in an environment whereby the temperature is maintained in the 32° F. to 41° F. range determined by the FDA. For the prior-art merchandisers  10  to achieve these temperatures in their product display areas  30 , the refrigerant passing through the conventional round-tube plate-fin evaporators  70  is maintained at a saturation temperature of about 24° F. The resultant airflow passing through the evaporator  70  is cooled to about 31° F. At these outlet temperatures, moisture in the airflow will condense out of the airflow, settle on the evaporator  70 , and freeze since the evaporator  70  is maintained at a temperature below the freezing point of water, thus leading to the build-up of frost on the evaporator  70 . As frost builds up on the evaporator  70 , the performance of the evaporator  70  deteriorates, and the free flow of air through the evaporator  70  becomes restricted and in extreme cases halted.  
         [0013]     The conventional round-tube plate-fin evaporators  70  characteristically have a low fin density, typically in the range of 2 to 4 fins per inch. This practice arises in anticipation of the buildup of frost of the surface of the evaporator  70  and the desire to extend the period between required defrosting operations. As frost builds up, the effective flow space for air to pass between neighboring fins becomes progressively less and less until, in the extreme case, the space is bridged with frost. As a consequence of frost buildup, the evaporator&#39;s performance decreases, and the flow of adequately refrigerated air to the product display area  30  decreases, thus necessitating activation of a defrost operation. Typically, several defrost operations are required per day to eliminate the accumulated frost on the evaporator  70 . Performing the defrost operations may be detrimental to the food and/or beverage products, since the products may be allowed to warm-up to a temperature above the 32° F. to 41° F. temperature range determined by the FDA. Defrosting the evaporator  70  also typically results in increased energy expenditures, since a relatively large amount of energy is required to initially “pull down” the air temperature in the product display area  30  after a defrost operation to an acceptable temperature within the 32° F. to 41° F. range.  
         [0014]     As a result of their inherent inefficiencies, conventional round-tube plate-fin evaporators  70  are often physically large, and are often mounted in the merchandiser  10  such that the airflow passing through the evaporator  70  is required to pass through the evaporator  70  in a direction coinciding with a major dimension (i.e., the length or height) of the evaporator  70  to achieve the desired airflow temperature exiting the evaporator  70  and the desired air temperature in the product display area  30  of the merchandiser  10 . The airflow is passed through the evaporator  70  in a direction coinciding with the major dimension to allow the evaporator  70  sufficient time to remove enough heat from the airflow to cool the airflow to a temperature of about 31° F. Further, the apertures  74  in the interior rear wall  22  are required to be centrally located, since the height of the evaporator  70  dictates the location of the apertures  74 . This prevents refrigerated air from reaching products situated in a lower portion  80  of the product display area  30 .  
       SUMMARY OF THE INVENTION  
       [0015]     The present invention provides, in one aspect, a refrigerated merchandiser including a case defining a product display area and an air passage separate from the product display area. The case includes a rear wall separating in part the product display area from a vertical portion of the air passage. The rear wall includes apertures near a lower portion of the product display area. The apertures communicate between the vertical portion of the air passage and the lower portion of the product display area. The refrigerated merchandiser also includes a fan positioned in the air passage to generate an airflow through the passage, and an evaporator positioned in the vertical portion of the air passage adjacent the rear wall and at an oblique angle relative to a vertical axis defined by the vertical portion of the air passage to allow the airflow to pass through the evaporator, through the apertures, and into the lower portion of the product display area.  
         [0016]     The present invention provides, in another aspect, a refrigerated merchandiser including a case defining a product display area and an air passage separate from the product display area. The case includes a rear wall separating in part the product display area from the air passage. The refrigerated merchandiser also includes a fan positioned in the air passage to generate an airflow through the passage, and a flat-tube evaporator positioned in the passage to receive the airflow from the fan. The flat-tube evaporator is configured to cool the airflow.  
         [0017]     The present invention provides, in yet another aspect, a refrigerated merchandiser including a case defining a product display area and an air passage separate from the product display area. The case includes a rear wall separating in part the product display area from the air passage. The refrigerated merchandiser also includes a fan positioned in the air passage to generate an airflow through the air passage, and an evaporator defining a major dimension and a minor dimension. The evaporator is positioned in the air passage behind the rear wall such that the airflow passes through the evaporator in a direction coinciding with the minor dimension.  
         [0018]     Other features and aspects of the present invention will become apparent to those skilled in the art upon review of the following detailed description, claims and drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]     In the drawings, wherein like reference numerals indicate like parts:  
         [0020]      FIG. 1  is a cross-sectional side view of a prior-art refrigerated merchandiser, exposing a conventional round-tube plate-fin evaporator positioned in an air passage toward the rear of the merchandiser.  
         [0021]      FIG. 2  is a cross-sectional side view of a refrigerated merchandiser of the present invention, exposing an evaporator positioned in an air passage toward the rear of the merchandiser.  
         [0022]      FIG. 3  is a partial perspective view of the merchandiser of  FIG. 2 , with portions being cut away to view the evaporator in the air passage.  
         [0023]      FIG. 4  is an enlarged view of a portion of the evaporator.  
         [0024]      FIG. 5  is a partial section view of a portion of the evaporator of  FIG. 4 . 
     
    
       [0025]     Before any features of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangements of components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limited.  
       DETAILED DESCRIPTION  
       [0026]     With reference to  FIGS. 2-3 , a modified medium-temperature refrigerated merchandiser  82  is shown. Such a merchandiser  82  may be located in a supermarket or a convenience store for presenting fresh food and/or beverages to customers. Some of the components of the merchandiser  82  of  FIGS. 2-3  are similar to those of the merchandiser  10  of  FIG. 1 , as such, like components will be labeled with like reference numerals and will not be further discussed.  
         [0027]     The modified merchandiser  82  utilizes a flat-tube evaporator  86 , rather than the conventional round-tube plate-fin evaporator  70 . As used herein, the flat-tube evaporator  86  is not limited to using a two-phase refrigerant, such as ammonia. Further, the flat-tube evaporator  86  may also be used as a heat exchanger using a single-phase refrigerant, such as glycol, to absorb heat from the airflow passing through the evaporator  86 . The evaporator  86  can be a single evaporator extending the length of the merchandiser  82  or it can be multiple modular evaporators that are connected together to extend the length of the merchandiser  82  as described in Hussmann&#39;s U.S. Reissue Pat. No. RE37,630 (Entitled REFRIGERATED MERCHANDISER WITH MODULAR EVAPORATOR COILS AND EEPR CONTROL).  
         [0028]     Generally, the flat-tube evaporator  86  offers better performance than the conventional round-tube plate-fin evaporator  70 . For example, the flat-tube evaporator  86  can achieve a refrigerant-side pressure drop as low as about 0.67 psi, compared to the 2 psi refrigerant-side pressure drop of the conventional round-tube plate-fin evaporator  70 . A lower refrigerant-side pressure drop allows the refrigerant to more easily move throughout the evaporator  86 . Also, the flat-tube evaporator  86  can achieve an air-side pressure drop as low as about 0.03 inwg (inches of water column gauge), compared to the 0.07 inwg pressure drop of the conventional round-tube plate-fin evaporator  70 . A lower air-side pressure drop allows the velocity of the airflow passing through the evaporator  86  to be decreased. Further, the flat-tube evaporator  86  allows for an approach temperature as low as about 1° F. The approach temperature is defined as the difference between the temperature of the discharged airflow and the saturation temperature of the refrigerant passing through the evaporator  86 . A conventional round-tube plate-fin evaporator  70  may only allow for an approach temperature as low as 7° F. However, in other constructions of the merchandiser  82 , a high-performance round-tube plate-fin evaporator (e.g., an air conditioning coil, not shown) that matches the performance of the flat-tube evaporator  86  may also be used in the merchandiser  82 .  
         [0029]     As shown in  FIGS. 3-4 , the flat-tube evaporator  86  includes an inlet manifold  90  and an outlet manifold  94  fluidly connected by a plurality of flat tubes  98 . In a preferred construction of the merchandiser  82 , the flat-tube evaporator  86  is positioned in the rear flue  54  such that the inlet and outlet manifolds  90 ,  94  are substantially horizontally-oriented and the flat tubes  98  are substantially vertically-oriented. Refrigerant maldistribution problems, in addition to condensate removal problems, are substantially alleviated by positioning the evaporator  86  in the rear flue  54  in this manner. A distributor (not shown) may also be positioned inside the inlet manifold  90  to help alleviate the refrigerant maldistribution problems.  
         [0030]     The flat-tubes  98  may be formed to include a plurality of channels, or internal passageways  102  (see  FIG. 5 ) that are much smaller in size than the internal passageway of the coil in the conventional round-tube plate-fin evaporator  70 . As used herein, the flat tubes  98  may also comprise mini multi-port tubes, or micro multi-port tubes (otherwise known as microchannel tubes). However, in other constructions of the flat tubes  98 , the tubes  98  may include only one channel, or internal passageway  102 . In the illustrated construction, the flat tubes  98 , the inlet manifold  90 , and the outlet manifold  94  are made from a highly conductive metal such as aluminum, however other highly conductive metals may also be used. Further, the flat tubes  98  are coupled to the inlet manifold  90  and the outlet manifold  94  by a brazing process, however, a welding process may also be used.  
         [0031]     The small internal passageways  102  allow for more efficient heat transfer between the airflow passing over the flat-tubes  98  and the refrigerant carried within the internal passageways  102 , compared to the airflow passing over the coil of the conventional round-tube plate-fin evaporator  70 . In the illustrated construction, the internal passageways  102  are configured with rectangular cross-sections, although other constructions of the flat tubes  98  may have internal passageways  102  of other cross-sections. The flat tubes  98  are separated into about 12 to 15 passageways  102 , with each passageway  102  being about 1.5 mm in height and about 1.5 mm in width, compared to a diameter of about 9.5 mm (⅜″) to 12.7 mm (½″) for the internal passageway of a coil in a conventional round-tube plate-fin condenser coil. However, in other constructions of the flat tubes  98 , the internal passageways  102  may be as small as 0.5 mm by 0.5 mm, and as large as 4 mm by 4 mm. The flat tubes  98  may also be made from extruded aluminum to enhance the heat transfer capabilities of the flat tubes  98 . In the illustrated construction, the flat-tubes  98  are about 22 mm wide. However, in other constructions, the flat tubes  98  may be as wide as 26 mm, or as narrow as 18 mm. Further, the spacing between adjacent flat tubes  98  may be about 9.5 mm. However, in other constructions, the spacing between adjacent flat tubes  98  may be as much as 16 mm, or as little as 3 mm.  
         [0032]     As shown in  FIG. 4 , the flat-tube evaporator  86  includes a plurality of louver fins  106  coupled to and positioned along the flat tubes  98 . The fins  106  may be coupled between adjacent flat tubes  98  by a brazing or welding process. The fins  106  are made from a highly conductive metal such as aluminum, like the flat tubes  98  and the inlet and outlet manifolds  90 ,  94 . The brazed assembly including the flat tubes  98 , the inlet and outlet manifolds  90 ,  94 , and the fins  106  forms a brazed aluminum construction. In the illustrated construction, the louver fins  106  are configured in a V-shaped pattern and include a plurality of louvers  108  formed in the fins  106 . In the illustrated construction, the fin density along the flat tubes  98  is about 16 fins per inch. However, in other constructions, the fin density along the flat tubes  98  may be as low as 6 fins per inch, and as high as 18 fins per inch. In yet other constructions, the fin density along the flat tubes  98  may be as high as 25 fins per inch.  
         [0033]     Generally, the fins  106  aid in the heat transfer between the airflow passing through the flat-tube evaporator  86  and the refrigerant carried by the flat-tubes  98 . The increased efficiency of the flat-tube evaporator  86  is due in part to such a high fin density, compared to the fin density of 2 to 4 fins per inch of the conventional round-tube plate-fin evaporator  70 . The increased efficiency of the flat-tube evaporator  86  is also due in part to the louvers  108 , which provide a plurality of leading edges to redirect the airflow through and around the fins  106 . As a result, heat transfer between the fins  106  and the airflow is increased. Further, the high air-side heat transfer of the louver fins  106  and the high refrigerant-side heat transfer of the flat tubes  98 , along with minimal contact resistance of the brazed aluminum construction, yields the highly efficient, and high-performance flat-tube evaporator  86 .  
         [0034]     The increased efficiency of the flat-tube evaporator  86 , compared to the conventional round-tube plate-fin evaporator  70 , allows the flat-tube evaporator  86  to be physically much smaller than the round-tube plate-fin evaporator  70 . As a result, the flat-tube evaporator  86  is not nearly as tall, and is not nearly as wide (or thick) as the conventional round-tube plate-fin evaporator  70 . Further, apertures  110  may be formed in the interior rear wall  22  much closer to the lower portion  80  of the product display area  30 . The apertures  110  are located toward the bottom of the interior rear wall  22 , and fluidly connect the lower portion  80  of the product display area  30  with the rear flue  54 . The apertures  110  allow some of the refrigerated air in the rear flue  54  to exit the rear flue  54  and enter the lower portion  80  of the product display area  30 . Products situated in the lower portion  80  of the product display area  30 , that otherwise would not receive much of the refrigerated air in the prior-art merchandiser  10 , may then be cooled by the refrigerated air.  
         [0035]     As shown in  FIG. 2 , the evaporator  86  is positioned in the rear flue  54  and tilted at an oblique angle θ relative to a vertical axis  114  passing through the rear flue  54 . The evaporator  86  is able to be tilted because it is physically much smaller in size than the conventional round-tube plate-fin evaporator  70 , which is oriented an upright manner and occupies the entire width of the rear flue  54  of the prior-art merchandiser  10 . However, in other constructions, the evaporator  86  may be positioned in the rear flue  54  substantially vertically or parallel with the rear flue  54  such that the airflow passes substantially horizontally through the evaporator  86 .  
         [0036]     By tilting the evaporator  86  as shown in  FIG. 2 , a greater amount of refrigerated air may be allowed to exit the evaporator  86 , pass through the apertures  110 , and enter the lower portion  80  of the product display area  30  to cool products situated therein. As a result, complex ducting structure for redirecting the refrigerated airflow downwardly to the lower portion  80  of the product display area  30  that is normally associated with some conventional refrigerated merchandisers is no longer required. In the illustrated construction, the evaporator  86  is tilted at an angle θ relative to the vertical axis  114  about 11 degrees. However, in other constructions of the merchandiser  82 , the evaporator  86  may be tilted at an angle θ relative to the vertical axis  114  between about 5 degrees and 15 degrees. The portion of the refrigerated airflow that does not enter into the lower portion  80  of the product display area  30  moves upwardly to be discharged as the air curtain  78 , as previously discussed.  
         [0037]     As a result of using the flat-tube evaporator  86 , the fans  66  are allowed to be relocated from the lower flue  46  to the rear flue  54 . This is allowed because the height of the flat-tube evaporator  86  is much less than that of the conventional round-tube plate-fin evaporator  70 . By doing this, the space ordinarily occupied by the fans  66  may now be freed up to store more food and/or beverage products in the lower portion  80  of the product display area  30 . Further, relocating the fans  66  to the rear flue  54  substantially prevents spilled products from coming into contact with the fans  66 , thus simplifying cleanup of the merchandiser  82 . However, in other constructions of the merchandiser  82 , the fans  66  may remain in the lower flue  46  as shown in  FIG. 1 . As a result, the flat-tube evaporator  86  may be lowered even further such that the flat-tube evaporator  86  may be positioned directly behind the lowest food and/or beverage products in the lower portion  80  of the product display area  30 .  
         [0038]     The increased efficiency of the flat-tube evaporator  86  compared to a conventional round-tube plate-fin evaporator  70  also allows for “wet operation” of the evaporator, while maintaining the FDA standard 32° F. to 41° F. temperature range within the product display area  30 . Conventional round-tube plate-fin evaporators  70 , because of their relatively poor efficiency, only allow for “frosted operation,” in which the saturation temperature of the refrigerant passed through the round-tube plate-fin evaporator  70  is maintained at about 24° F. The airflow passing through the round-tube plate-fin evaporator  70  is cooled to about 31° F., which is below the freezing point of water. At these outlet temperatures, moisture in the airflow will condense out of the airflow, settle on the evaporator  70 , and freeze since the evaporator  70  is maintained at a temperature below the freezing point of water, thus leading to the build-up of frost on the evaporator  70 .  
         [0039]     The conventional round-tube plate-fin evaporators  70  often need to discharge the airflow at such low temperatures to maintain a temperature in the product display area  30  that is near the lower limit of the FDA determined 32° F. to 41° F. temperature range. This is to accommodate for the multiple defrost operations that occur during the course of the day. By providing refrigerated air to the product display area  30  at a temperature of about 31° F., more time is available to defrost the evaporator  70  while the product display area  30  warms up. Since the food and/or beverage products are maintained at a temperature at or near about 31° F., the defrost operation should be completed before the temperature of the food and/or beverage products warms up to about 41° F., which is the upper limit of the FDA determined temperature range.  
         [0040]     The increased efficiency of the flat-tube evaporator  86  allows for “wet operation,” in which the saturation temperature of the refrigerant passing through the flat-tube evaporator  86  is maintained at about 32° F. to cool the airflow passing through the flat-tube evaporator  86  to about 33° F., which is above the freezing point of water. This is allowed as a result of moving the airflow at a relatively low velocity, compared to conventional merchandisers  10 , over the large heat transfer surface or face of the flat-tube evaporator  86 .  
         [0041]     The saturation temperature of the refrigerant may also be lowered (to as low as 30° F., without frosting) to cool the airflow passing through the flat-tube evaporator  86  below 33° F. At these discharge temperatures, moisture in the airflow will condense out of the airflow, and settle on the evaporator  86  as water droplets. Since the water droplets will not freeze, frost build-up on the evaporator  86  will be substantially prevented, thus eliminating defrost operations entirely. Further, the performance of the evaporator  86  will not decrease during periods of operation. The water droplets may fall into and be collected in a drain (not shown) below the evaporator  86 , which would otherwise be used for collecting water droplets during a defrost operation.  
         [0042]     As previously described, some of the refrigerated airflow discharged from the flat-tube evaporator  86  is allowed directly into the product display area  30 . Since defrost operations are not required when using the flat-tube evaporator  86 , the refrigerated air exiting the evaporator  86  and entering the product display area  30  may be raised from 31° F. to 33° F. As such, the food and/or beverage products in the product display area  30  may be maintained well within the FDA determined 32° F. to 41° F. temperature range since temperature fluctuations due to defrost operations are eliminated. Further, increasing the saturation temperature of the refrigerant from 24° F. to 32° F. allows for a decreased energy consumption by the compressor, and eliminating the defrost operations allows for additional energy savings by eliminating the initial “pull down” loads after completing a defrost operation.  
         [0043]     The increased efficiency of the flat-tube evaporator  86  also allows the airflow to be directed over the minor dimension of the evaporator  86  (the width or thickness dimension) as opposed to the major dimension of the evaporator  86  (the height or length dimension). This is possible since the flat-tube evaporator  86  is allowed sufficient time to remove enough heat from the airflow to cool the airflow to the desired 33° F. discharge temperature.