Abstract:
A suction accumulator for a refrigeration system includes a pair of closed shells arranged in spaced relation one within the other to define a space therebetween effective to prevent sweating of the inner shell during performance of its normal suction accumulator function. The space is connected between the condenser and the expansion valve of the system to function as a receiver for warm refrigerant thereby creating heat exchange through the wall of the inner shell.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates generally to a suction accumulator for a refrigeration system and, in particular, to a suction accumulator that also functions as a receiver and a heat exchanger. 
     It is known in the art to which this invention pertains to provide a suction accumulator between the evaporator and compressor of a refrigeration system in order to protect the compressor from possible damage. Vaporized refrigerant is received from the evaporator and passed on through the suction accumulator to the compressor. Any raw liquid is metered back to the compressor at a rate that will not result in damage to the compressor. 
     In recent years, primarily for reasons of energy savings and improved efficiency, it has often become the practice to flood the evaporator, or “low side” of the refrigeration suction accumulator, wherein evaporation takes place, reducing the surface temperature of the accumulator below ambient dew point, which causes sweating of the accumulator surfaces. Sweating of the accumulator ultimately leads to rusting, and possible accumulation of water on surfaces beneath the accumulator. 
     One expedient that has been employed in an effort to eliminate the sweating and ultimate rusting problems has been to wrap or encase the suction accumulator with one or more layers of insulation. However, this is costly from a material and labor standpoint. Also, difficulty has been encountered in providing an airtight insulative seal, ultimately resulting in the described sweating and rusting problems. 
     It has further been proposed to position a suction accumulator within a receiver, and to admit into the space therebetween high temperature liquid refrigerant from the condenser. A structural arrangement of this character is shown in the U.S. Pat. No. 3,212,289. As is described herein, the relatively warm refrigerant prevents moisture in the atmosphere from condensing on the accumulator which contains relatively cold refrigerant. The patented arrangement also provides an efficient heat exchange between the relatively cold low pressure refrigerant in the accumulator and the relatively warm high pressure refrigerant in the receiver. 
     The provision of a dead air space between a suction accumulator and a surrounding sealed vessel or container is effective to a large degree in precluding sweating and subsequent rust formation upon the accumulator walls. The insulative property of the space provided by the novel structure of this invention may be further enhanced by evacuating the space. The structure resulting may be considered similar to that of a vacuum Thermos bottle. Additionally, enhancement of the novel purposes of this invention may be accomplished by provision of means effective to prevent sweating of the inlet and outlet connections to and from the suction accumulator. These concepts are shown in the U.S. Pat. No. 5,479,790. 
     SUMMARY OF THE INVENTION 
     Significant advantages result by combining into a single unit a suction accumulator and receiver, or even more advantageously, a suction accumulator, receiver and heat exchanger into a unitary structure. The functions of each are achieved in a single body, and thereby the costs of each as separate units are eliminated, with the further advantage of substantial space savings. 
     The suction accumulator, receiver and heat exchange apparatus according to the present invention is used in a refrigeration system having a condenser connected between an outlet of a compressor and an inlet of an expansion valve and an evaporator connected between an outlet of the expansion valve and an inlet of the compressor. The apparatus includes: a tubular outer shell having opposite ends closed by an upper closure and a lower closure and a pair of connector means extending through a side wall of the outer shell; a tubular inner shell positioned interiorly of the outer shell and having an upper end portion extending outside the outer shell through an opening formed in the upper closure, the inner shell having a closed lower end and an upper end having a pair of tube openings formed therein; a generally U-shaped outlet tube positioned interiorly of the inner shell and having one end extending through one of the tube openings; and an inlet tube positioned interiorly of the inner shell and having one end extending through another one of the tube openings. When the connector means are connected to the outlet of the condenser and the inlet of the expansion valve, the outer shell functions as a refrigeration system receiver receiving warm refrigerant from the condenser, and when the one end of the inlet tube is connected to an outlet of the evaporator and the one end of the outlet tube is connected to the inlet of the compressor, the inner shell functions as a suction accumulator receiving cool refrigerant from the evaporator, and heat exchange occurs between the warm refrigerant and the cool refrigerant through a side wall of the inner shell. The inner shell can be formed of a copper material to increase heat exchange. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above, as well as other advantages of the present invention, will become readily apparent to those skilled in the art from the following detailed description of a preferred embodiment when considered in the light of the accompanying drawings in which: 
     FIG. 1 is a schematic diagram of a conventional refrigeration system representing an illustrative environment for a suction accumulator in accordance with the present invention; 
     FIG. 2 is a side elevational view in cross section of a suction accumulator according to the present invention; and 
     FIG. 3 is a side elevational view in cross section of an alternate embodiment of the suction accumulator according to the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     There is shown in the FIG. 1 a conventional refrigeration system  10  charged with a refrigerant material. As is normal, a compressor  12  receives a gaseous refrigerant material through a suction conduit means  14  from an outlet of a suction accumulator  16 . The gaseous refrigerant is compressed and passes from the compressor  12  to a condenser  18 . The refrigerant is condensed to a liquid state at the condenser  18 , and passes through an expansion valve  20  whereat its temperature and pressure are reduced. The cooled refrigerant then passes to an evaporator  22 , wherein it is vaporized by absorbing heat, and then enters the suction accumulator  16  through a conduit means  24 . 
     In recent years, there is an increasing tendency, ascribed to energy savings and efficiency requirements, to flood the “low side” of the refrigeration system shown in the FIG. 1, and more particularly the evaporator  22  shown therein. This causes liquid refrigerant to almost continuously spill back into the suction accumulator  16 . Evaporation of this liquid in the accumulator  16  reduces its surface temperature often below the ambient dew point, causing constant sweating of the accumulator surface. This constant sweating ultimately results in rusting of the accumulator  16 , and further, the deposition of undesirable pools of water on the surface beneath the accumulator. 
     Applicants have discovered that these problems are effectively overcome, and other advantageous results achieved, by utilization of a suction accumulator assembly according to the present invention substantially as shown in FIG. 2 of the drawings. The accumulator assembly is designated generally therein by the numeral  30 , and comprises a tubular outer shell  31 , of generally cylindrical shape, sealed essentially hermetically at opposite ends by cap or closure means including an upper outer shell closure  32  and a lower outer shell closure  33 . The outer shell closures  32  and  33  are generally cup-shaped and have side walls engaging outer end surfaces of the shell  31 . The outer shell  31  functions in the nature of a receiver in the present invention, and may support a threaded mounting means  34  attached to the lower closure  33  as is conventional in the art. Provided on the outer shell  31 , at any desired location thereon, are a pair of passages or open-ended connector means  35  and  36 , constructed to be sealed or rendered airtight when required. The function of the connector means  35  and  36  is to connect the interior of the outer shell  31  between the condenser  18  and the expansion valve  20  of the system  10  shown in the FIG.  1 . 
     Located interiorly of the shell  31  is a suction accumulator  37  in the form of a tubular, generally cylindrical shell  38  having a hemispherical closed lower end  39  and a reduced diameter upper end  40  with a pair of tubular extension openings  41  and  42 . An upper end portion of the inner shell  38  extends through a central opening  32   a  formed in the upper outer shell closure  32  such that the reduced diameter upper end  40  is positioned outside the outer shell  31 . The inner shell  38  typically is of spun construction. As shown, the outer shell  31  and the inner shell  38  are coaxially spaced to provide an annular space  43  for fluid, which may be  25  vacuum, air, gas or liquid, depending upon the particular function or mode of operation selected for the suction accumulator assembly  30 . The relatively warm refrigerant leaving the condenser  18  is warmer than the surrounding atmosphere at ambient temperature and thereby prevents moisture in the air from condensing on the external surface of the outer shell  31 . There is heat exchange between the warm refrigerant in the space  43  and the cooler refrigerant in the inner shell  38  through the wall of the inner shell. The shells  31  and  38  are typically formed of a steel material. This heat exchange can be increased by forming the inner shell  38  of a material having higher heat conductivity such as, for example, a copper material. 
     Disposed within the inner shell  38  of the suction accumulator  37  and suitably supported therein is a generally U-shaped outlet tube  44 . One end of the tube  44  is mounted in and extends through the tube opening  42  for connection to the suction conduit means  14  leading to compressor  12  of the system  10 . Similarly, an inlet tube  45  is mounted in and extends through the tube opening  41  for connection to the conduit means  24  leading to the evaporator  22  of the system  10 . Thus, the suction accumulator  30  according to the present invention replaces the conventional suction accumulator  16  in the refrigeration system  10  shown in the FIG.  1 . As such, the suction accumulator assembly  30  as constructed in the manner shown in the FIG. 2 is effective to substantially entirely avoid the sweating problem of conventional suction accumulators earlier described. 
     A fuisible plug  46  can be mounted in an opening formed in the wall of the upper end  40  of the inner shell  38  and is useful for permitting the communication of gas from the interior of the inner shell to the atmosphere. The plug  46  has an internal wall (not shown) blocking such communication until the internal wall melts at a predetermined temperature to allow gas to escape and prevent an explosion. A similar fusible plug  47  can be mounted in an opening formed in the wall of the outer shell  31  and is useful for permitting the communication of gas from the space  43  to the atmosphere. 
     There is shown in the FIG. 3 of the drawings an alternate embodiment suction accumulator assembly  50  comprising a tubular, generally cylindrical outer shell  51 , sealed essentially hermetically at opposite ends by closure means including an upper outer shell closure  52  and a lower outer shell closure  53 . The closures  52  and  53  are generally cup-shaped and have side walls engaging outer end surfaces of the shell  51 . The outer shell  51  functions in the nature of a receiver in the present invention, and may support a threaded mounting means  54  attached to the lower closure  53 . Provided on the outer shell  51 , at any desired location thereon, are a pair of passages or open-ended connector means  55  and  56 , constructed to be sealed or rendered airtight when required. The function of the connector means  55  and  56  is to connect the interior of the outer shell  51  between the condenser  18  and the expansion valve  20  of the system  10  shown in the FIG.  1 . 
     Located interiorly of the shell  51  is a suction accumulator  57  of tube and cap construction. A tubular, generally cylindrical shell  58  has upper and lower end openings. The lower end opening is sealed by a cup-shaped lower inner shell closure  59  inverted and inserted into the opening with a side wall engaging an interior end surface of the inner shell  58 . The upper end opening is sealed by a cup-shaped upper inner shell closure  60  having a side wall engaging an outer end surface of the inner shell  58 . An upper end portion of the inner shell  58  extends through a central opening  52   a  formed in the upper outer shell closure  52  such that the upper inner shell closure  60  is positioned outside the outer shell  51 . A pair of tube openings  61  and  62  are formed in the upper inner shell closure  60 . As shown, the outer shell  51  and the inner shell  58  are coaxially spaced to provide an annular space  63  for fluid, which may be vacuum, air, gas or liquid, depending upon the particular function or mode of operation selected for the suction accumulator assembly  50 . 
     Disposed within the inner shell  58  of the suction accumulator  57  and suitably supported therein is a generally U-shaped outlet tube  64 . One end of the tube  64  is mounted in and extends through the tube opening  62  for connection to the suction conduit means  14  leading to compressor  12  of the system  10 . Similarly, an inlet tube  65  is mounted in and extends through the tube opening  61  for connection to the conduit means  24  leading to the evaporator  22  of the system  10 . Thus, the suction accumulator  50  according to the present invention replaces the conventional suction accumulator  16  in the refrigeration system  10  shown in the FIG.  1 . As such, the suction accumulator assembly  50  as constructed in the manner shown in the FIG. 3 is effective to substantially entirely avoid the sweating problem of conventional suction accumulators earlier described. 
     A fusible plug  66  can be mounted in an opening formed in the wall of the upper inner shell closure  60  and is useful for permitting the communication of gas from the interior of the inner shell  58  to the atmosphere. The plug  66  has an internal wall (not shown) blocking such communication until the internal wall melts at a predetermined temperature to allow gas to escape and prevent an explosion. A similar fusible plug  67  can be mounted in an opening formed in the wall of the outer shell  51  and is useful for permitting the communication of gas from the space  63  to the atmosphere. 
     The suction accumulator assemblies  30  and  50  each function as a suction accumulator, receiver and heat exchanger with high efficiency and non-drip operation. 
     In accordance with the provisions of the patent statutes, the present invention has been described in what is considered to represent its preferred embodiment. However, it should be noted that the invention can be practiced otherwise than as specifically illustrated and described without departing from its spirit or scope.