Abstract:
A comfort system outdoor unit with a heat exchanger coil and a fan in its top opening has an orifice structure and an insert registerable with the orifice structure to streamline the inward flow of air that passes over a lower end of the orifice structure. The insert may be fastened directly to the orifice structure lower end, or it may be installed so as to extend substantially from an upper edge of the coil to the orifice structure lower end.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates generally to outdoor units for air conditioners/heat pumps and, more particularly, to a method and apparatus for adapting the orifice to reduce sound levels and flow losses. 
     Air cooled condensers, as commonly used in residential air conditioning systems, employ fin tube construction to transfer heat from the refrigerant to the outdoor air. As hot, high pressure refrigerant passes through the coil, heat from the compressed refrigerant is transferred through the tubes to the attached fins. An electrically powered fan is then used to draw large quantities of outside air across the fin heat transfer surfaces to remove heat from the refrigerant so that is will condensed and partially subcooled prior to its reaching the expansion valve. 
     In heat pump application, the same outdoor unit operates in much the same manner but the heat exchanger operates as an evaporator rather than a condenser. Air conditioners and heat pumps are sometime referred to generically as comfort systems. 
     The heat exchanger coil of an outdoor unit is usually round, rectangular, or square in form, and the compressor is normally disposed within the coil. A fan and its drive motor is commonly mounted above the heat exchanger coil such that the fan draws outdoor air inwardly through the coil and then upwardly to be discharged into the atmosphere. 
     In order to guide the airflow stream in the vicinity of the fan, i.e. particularly as it flows radially inwardly to the fan and as it is discharged to the atmosphere at the top of the fan, a so called orifice structure is included at the top of an outdoor unit to provide a smooth surface over which the air is caused to flow. Typically the orifice has a cross section that resembles an inverted U with an outer leg wrapped over the outer side of the coil and an inner leg which extends downwardly in the vicinity of the fan. At the lower end of the inner leg, there is a slight radially outward flare, but the inner leg normally protrudes into the airflow stream. 
     The applicants have recognized that the inner leg or orifice leading edge causes flow disturbances, thereby resulting in efficiency losses and increased sound levels. Ideally, the outwardly flaring portion of the inner leg would be extended to provide a smooth surface over which the air can flow rather than a sharp edge that disrupts the flow pattern. However, the normal process of forming the orifice structure from sheet metal does not allow such an approach because of splitting or tearing of the sheet metal material that tends to occur. 
     SUMMARY OF THE INVENTION 
     Briefly, in accordance with one aspect of the invention, an insert is installed near the orifice leading edge to thereby change the airflow pattern thereover in such a way as to reduce the sound level and increase the efficiency of the system by decreasing the flow losses that would otherwise occur. 
     By another aspect of the invention the insert is attached to and supported by the orifice leading edge. 
     By yet another aspect of the invention, the insert extends from a point near the orifice leading edge and extends upwardly and outwardly at an angle so as to interface with the outer edge of the orifice structure. 
     By still another aspect of the invention, the insert includes structure that engages an inner surface at the orifice structure. 
     In the drawings as hereinafter described, a preferred embodiment is depicted; however, various other modifications and alternate constructions can be made thereto without departing from the true spirit and scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an outdoor unit in accordance with the prior art. 
         FIG. 2  is a partial perspective view thereof showing the orifice structure in particular. 
         FIG. 3  is a schematic illustration thereof showing the pattern of the airflow over the orifice structure. 
         FIG. 4  is a schematic illustration of an installed insert in accordance with the present invention. 
         FIG. 5  is an alternative form thereof 
         FIG. 6  is yet another alternative embodiment thereof. 
         FIGS. 7A and 7   b  are is a perspective views of a typical orifice structure to which the present invention relates. 
         FIGS. 8A-8C  are perspective views of the insert in accordance with the present invention. 
         FIG. 9  is a perspective view of the orifice structure and insert in combination in accordance with the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Shown in  FIG. 1  is a conventional outdoor unit of an air conditioning system in accordance with the prior art. The heat exchanger coil  11  is shown as a cylindrical structure, although it may just as well be square or rectangular in shape. A compressor  12  is located within the coil  11  and is connected to pump refrigerant vapor through a vapor compression cycle. A fan  13  is centrally disposed within a top opening  14  and includes an electric drive motor  16  for rotating the fan  13 . 
     In operation, the fan  13  is rotated by the motor  16  to draw ambient air radially inwardly through the heat exchanger coil  11 , after which the warmer air is discharged upwardly through the top opening  14 . 
     At the top of the coil  11 , a so called top or orifice structure  17  is placed around the coil  11  so as to surround the opening  14 . As will be seen in  FIG. 2 , the top  17  is generally an inverted U-shaped member having an outer leg  18  which wraps around the upper edge surface of the coil  11  and an inner leg  19 . At the lower end of the inner leg  19  the structure flare radially outwardly to an orifice leading edge  21  as shown in  FIG. 2 . 
     Considering now the pattern of airflow as it flows radially inwardly, around the orifice leading edge  21  and then upwardly out the top opening  14 , it will be seen in  FIG. 3  that outside and above the orifice leading edge  21 , the air is drawn radially inwardly to a cavity  23 , and then downwardly from where it must then flow radially outwardly to get around the orifice leading edge  21 . Accordingly, it is caused to change directions at that point very quickly as shown. This phenomenon not only causes significant flow losses but also creates a significant amount of noise. Because of these flow losses a large separation bubble will be created at  15  when the resulting flow interacts with fan blades  13  thereby generating high noise levels. 
     As will be seen in  FIG. 4 , the applicants have addressed these problems by providing an insert  22  that extends between the outer leg  18  and the orifice leading edge  21  to thereby close the cavity  23  into which the airflow entered in accordance with the prior art embodiment of  FIG. 3 . The result is that the flow stream of air is much smoother and is not caused to reverse direction as will be seen in  FIG. 4 . In this way, both the flow losses and the noise are substantially reduced. Because the flow losses are reduced, the separation bubble  20  will be much smaller, and therefore the noise will be substantially reduced. 
     As an alternative approach, rather than the insert  22  extending the entire distance between the outer leg  18  and the orifice leading edge  21  as shown in  FIG. 4 , a modified insert  24  comprises a small curvilinear element as shown in  FIG. 5 . Such an insert may be attached to the inner leg  19 , near the orifice leading edge  21 , by way of a plurality of fasteners  26  or the like. As will be seen in  FIG. 5 , the resulting airflow stream will be drawn in slightly more radially than the  FIG. 4  embodiment but not nearly as much as the  FIG. 3  embodiment, and the flow stream around the orifice leading edge  21  is curved and smooth, such that very little losses and noise are created. Because the flow losses are reduced, the separation bubble  25  will be much smaller, and therefore the noise will be substantially reduced. 
     A similar modified insert is shown at  27  in  FIG. 6 . The insert  27  is substantially the same shape as the insert  24  of the  FIG. 5  embodiment, and the resulting airflow pattern is substantially the same. However, the means of attachment is modified such that rather than using fasteners  26  as shown in  FIG. 5  a clip arrangement  28  is provided at the lower end of the modified insert such that the two arms of the clip  28  are disposed on opposite sides of the orifice leading edge  21  as shown. 
     Referring now to  FIGS. 7A and 7B , the top  17  is shown in an upright and an inverted position, respectively. It will be seen that the cavity  23  between the outer leg  18  and inner leg  19  is adaptable for receiving the insert  22  therein. The insert is shown in  FIG. 8A-8C . 
     In  FIG. 8A  the insert  22  is shown in an upright position and includes three sides  29 ,  31  and  32  in a generally rectangular relationship. These three sides correspond with the three sides of the heat exchanger coil. The fourth side, which is open, corresponds to the side on which there is no coil and on which the controls and various attaching fixtures are located. It will, of course, be understood that the shape and configuration of this insert  22  can be varied to accommodate the particular configuration of the unit. For example, round or square units are a common configuration for outdoor units. 
     As will be seen in  FIGS. 8A and 8B , the insert  22  includes a planar, generally horizontally disposed, rim  33 , with an upstanding wall  34  extending upwardly from its inner edge. A plurality of stanchions  36  are disposed in spaced relationship on the upper surface of the planar rim  33 . The upstanding wall  34  and the stanchions  36  are adapted to register with the inner surface of the top  17  when the insert  22  is installed therein as shown in  FIG. 9 . 
     Referring back to  FIGS. 8A-8C , it will be seen that an oblique wall  37 , is attached to the inner edge of the planar rim  33  and extends downwardly and inwardly to an inner edge  38 . When installed in the top  17  the inner edge  38  is adapted to be in contact with, or in close proximity to, the orifice leading edge  21 . On the inner side of the oblique wall  22  a plurality of ribs  39  are provided in spaced relationship for the purpose of adding strength and rigidity to the insert  22 . Further, at each end of the insert  22  there is provided an end rib  41  for the purpose of adding strength and rigidity to the part. The insert  22  is adapted to rest on and be supported by the coil  11 , with the rim  33  resting on top of the coil  11 .