Abstract:
A refrigerator condenser includes a spiraled tube and wire member construction to form a substantially longitudinal and rounded passage between a first end and a second end. The second end of the condenser is closed, thereby preventing longitudinal airflow through the passage and producing airflow into the passage in a substantially perpendicular direction to the condenser surface. Heat transfer to the air is thereby maximized and efficiency of the condenser is increased.

Description:
BACKGROUND OF THE INVENTION 
   This invention relates generally to refrigeration systems and, more particularly, to condensers for refrigerators. 
   Refrigeration systems typically include a compressor coupled to a condenser so that a compressed refrigerant flows to the condenser. See, for example, U.S. Pat. No. 5,711,159. A condenser fan circulates air over a surface of the condenser to cool the compressed refrigerant and is powered by a condenser fan motor. 
   Condenser surfaces for refrigerators are typically of tube and wire construction in which a refrigerant tube, or condenser coil, including a plurality of U-shaped segments is attached to a plurality of substantially parallel wires. In one type of condenser, a plurality of tube and wire members are placed in parallel rows underneath a refrigerator cabinet in an air flow path extending from a front of the refrigerator cabinet. See, for example, U.S. Pat. No. 5,592,829 However, this requires an increased distance between the refrigerator cabinet and a floor to provide adequate air access to the condenser surfaces, and, more importantly, suffers from reduced efficiency due to unevenly distributed airflow across the condenser surfaces and airflow parallel to the refrigerant tubes and/or wires. Air flowing through a relatively small air path through a lower front of the refrigerator produces relatively high air velocity and pressure drop of the air, which reduces an airflow rate across the condenser, increases noise, and reduces condenser efficiency. The reduced condenser efficiency results either in a decreased energy efficiency of the refrigerator or an increased cost in the condenser because of extra coil that is required to obtain a required heat transfer to the air. 
   Rectangular or cube shaped condensers have been developed to reduce the condenser volume and conserve space. See, for example. U.S. Pat. No. 5,685,166. However, these condensers also suffer efficiency losses due to uneven airflow over the condenser surfaces and airflow parallel to the condenser surfaces. Thus, extra coil is often required to achieve a desired heat transfer to the air. Also, a considerable number of U-shaped elbows with small radiuses are required to fabricate the rectangular condenser shape, which increases condenser cost and decreases condenser reliability. 
   Accordingly, it would be desirable to provide a refrigerator condenser that more effectively transfers heat to the air, promotes even air flow across the condenser surface, reduces the need for extra condenser coil, and avoids the need for U-shaped elbows of small radius that compromise condenser reliability and increases condenser cost. 
   BRIEF SUMMARY OF THE INVENTION 
   In an exemplary embodiment of the invention, a refrigerator condenser includes a longitudinal axis and a tube and wire member spiraled about the longitudinal axis. A passage extends through the tube and wire member between a first end and a second end. The second end is closed to prevent longitudinal air flow through the second end. Thus, when used with a condenser fan mounted in the first end, air is drawn into the passage substantially perpendicularly to an outside surface of the condenser and through the spiraled tube and wire member. The perpendicular airflow through the condenser surface maximizes heat transfer to the air, increases the efficiency of the condenser, and reduces the need for extra coil to achieve a selected heat transfer to the air. Moreover, the spiraled tube and wire member produces a compact condenser while avoiding the use of small radius elbows that increase the cost of the condenser and reduce condenser reliability. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a partial plan view of a known condenser tube and wire member; 
       FIG. 2  is an end view of the condenser tube and wire member formed into a condenser; 
       FIG. 3  is a perspective view of the condenser shown in  FIG. 2 ; and 
       FIG. 4  is a perspective view of a refrigerator condenser assembly. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  is a partial top plan view of a known condenser tube and wire member  10  fabricated from known methods and materials. Tube and wire member  10  includes an extended refrigerant tube  12 , or condenser coil, attached to a plurality of substantially parallel wires  14  extending from a first end  16  to a second end  18 . Tube  12  includes a plurality of U-shaped segments  20  extending substantially perpendicularly to wires  14  and joined to one another. The number of U-shaped segments  20  is selected to achieve a desired heat transfer rate to air flowing over a surface  20  of tube and wire member  10  without excessive pressure drop in refrigerant flowing inside refrigerant tube  12 . Tube and wire member  10  is substantially flat and rectangular, and includes an outer edge  26  and an inner edge  28  at a bend of each U-shaped segment  20  of tube  12 . Tube connector segments  30  extend from outer edge  26  for connection to a refrigerator circuit (not shown). It is recognized that other known configurations of tube and wire members could be used in alternative embodiments within the scope of the present invention. 
     FIG. 2  is an end view of tube and wire member  10  formed into a condenser  40 . Outer edge  26  is wrapped around inner edge  28  to form an extended rounded shape about a longitudinal axis  42  that is substantially parallel to inner edge  28  and outer edge  26 . An asymmetrically rounded opening  44  is formed between first end (not shown) and second end  18  and is substantially constant in cross sectional area between the first end and second end  18  of condenser  40 . Inner edge  28  is positioned a first radial distance R 1  from longitudinal axis, and outer edge  26  is positioned a second radial distance R 2  from longitudinal axis  42  that is greater than R 1 . Tube and wire member second end  18  forms a spiraled edge  46  including a number of wraps  48  of tube and wire member  10 . Each complete revolution, i.e., 360 degrees about longitudinal axis  42 , of refrigerant tube  12  form inner edge  28  constitutes one wrap  48 . In other words, a new wrap  48  begins when spiraled refrigerant tube  12  passes tube and wire member inner edge  28  and begins to overlap a portion of refrigerant tube  12  underneath. Thus, a layered condenser surface  24  is obtained. While  FIG. 2  illustrates about two whole wraps  48  of refrigerant tube  12 , other numbers of wraps, including partial wraps, could be used in alternative embodiments, such as three, four, or even more. Refrigerant tube  12  has an outer diameter  50 . 
   In one embodiment, wraps  48  are layered about longitudinal axis  42  in an Archimedes spiral defined by the relationship
 
 R=Aθ 
 
where A is a selected constant, θ is an angular distance from a beginning, or center, of the spiral, and R is a radial distance to a point in the spiral from the center of the spiral. Therefore, R constantly increases along each wrap  48 , and a distance between adjacent wraps  48  is approximately equal from one wrap to the next. In a further embodiment, each wrap includes segments of an Archimedes spiral having different center points to facilitate manufacturing of spiraled tube and wire member  10 . Other types of spirals, with or without multiple centers for the wraps, and with or without substantially uniform distance between the wraps, are employed in various alternative embodiments without departing from the scope of the invention.
 
     FIG. 3  is a perspective view of condenser  40  including rounded opening  44  about longitudinal axis  42  and illustrating air flow therethrough with arrows. Second end  18  of condenser  40  is closed to prevent air from flowing longitudinally through condenser opening second end  18 . A fan blade (not shown) is mounted at condenser opening first end  16  and driven by a motor (not shown) to draw air through condenser surface  24  and transfer heat from condenser surface  24  to the air. Because second end  18  is closed, air is drawn into condenser  40  substantially perpendicular to condenser surface  24 , i.e., substantially perpendicular to both refrigerant tube  12  wires  14 , of each wrap  48  to maximize heat transfer from condenser surface  24  to the air and increase the efficiency of condenser  40 . After flowing substantially perpendicularly past refrigerant tubes  12  and wires  14 , air converges inside opening  44  and is exhausted by the fan blade at first end  16  through opening  44  substantially perpendicular to longitudinal axis  42 . 
     FIG. 4  is a perspective view of a refrigerator condenser assembly  60 , including condenser  40 , fan blade  62  and compressor  64 . Compressor  64  compresses refrigerant supplied by an evaporator (not shown) through a suction line  66 . Compressor  64  adds work to the refrigerant, which heats the refrigerant before flowing into condenser  40 . High pressure and high temperature gaseous refrigerant leaves compressor  64  through a discharge port and flows to condenser  40 , where high pressure gaseous refrigerant is cooled to a saturation temperature, eventually condensing the refrigerant into a liquid state. 
   A baffle  68  is mounted at condenser second end  18  to prevent longitudinal air flow parallel to wires  14  that decreases heat transfer efficiency. Fan blade  62  is mounted at condenser first end  16  external of opening  44  and draws air through condenser  40  substantially perpendicular to condenser outer surface  24  and longitudinally after condenser  40  and toward compressor  64  to cool compressor  64  as well. In alternative embodiments, other closure members besides baffle  68  are used to close condenser second end. 
   Thus, a compact, energy efficient and inexpensive condenser  40  is provided. Condenser  40  is easily fabricated by bending flat tube and wire member  10  (shown in  FIG. 1 ) into a spiral shape about longitudinal axis  42 , and because air flow is directed substantially perpendicularly and evenly through condenser surface  24 , condenser outperforms condensers of the prior art and reduces the need for extra coil to achieve a desired heat transfer to the air. Furthermore, the compactness is achieved without the use of small radius elbows connecting evaporator tube segments that tend to increase condenser cost and decrease condenser reliability. 
   While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.