Abstract:
A cooling system for appliances, air conditioners, and other spaces includes a compressor, and a condenser that receives refrigerant from the compressor. The system also includes an evaporator that receives refrigerant from the condenser. Refrigerant received from the condenser flows through an upstream portion of the evaporator. A first portion of the refrigerant flows to the compressor without passing through a downstream portion of the evaporator, and a second portion of the refrigerant from the upstream portion of the condenser flows through the downstream portion of the evaporator after passing through the upstream portion of the evaporator. The second portion of the refrigerant flows to the compressor after passing through the downstream portion of the evaporator. The refrigeration system may be configured to cool an appliance such as a refrigerator and/or freezer, or it may be utilized in air conditioners for buildings, motor vehicles, or other such spaces.

Description:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT 
     This invention was made with government support under Award No. DE-EE0003910, awarded by the U.S. Department of Energy. The government has certain rights in the invention. 
    
    
     BACKGROUND OF THE INVENTION 
     Known cooling systems for refrigerators, freezers, air conditioners and the like include a compressor, a condenser, and expander such as a capillary tube, and an evaporator. These components are interconnected utilizing elongated conduits, whereby compressed refrigerant flows from the compressor through the condenser, the expander, the evaporator, and then into the compressor. Known systems commonly include a single fluid conduit forming a loop whereby the refrigerant flows in a single stream through the various components of the system. 
     However, known systems suffer from various drawbacks, and may not provide optimum efficiency. 
     BRIEF SUMMARY OF THE INVENTION 
     One aspect of the present invention is a cooling system configured so as to cool a space. The space may comprise an insulated space in a refrigerator or other such appliance. The cooling system includes a compressor, and a condenser that receives refrigerant flowing from the compressor. The system further includes an evaporator that receives refrigerant flowing from the condenser. The evaporator defines upstream and downstream portions, and refrigerant received from the condenser flows through the upstream portion of the evaporator. A first portion of the refrigerant flows to the compressor without passing through the downstream portion of the evaporator, and a second portion of the refrigerant from the upstream portion of the condenser flows through the downstream portion of the evaporator after passing through the upstream portion of the evaporator. The second portion of the refrigerant flows to the compressor after passing through the downstream portion of the evaporator. 
     The compressor may include first and second suction ports that receive the first and second portions, respectively, of the refrigerant. The first suction port may comprise a high suction port of the compressor, and the second suction port may comprise a low pressure suction port. The high pressure suction port of the compressor pulls the refrigerant vapor out of the evaporator and into the compressor, and the remaining liquid refrigerant passes through a downstream portion of the evaporator. A second expander such as a capillary tube may be utilized to expand the liquid refrigerant that has passed through the upstream portion of the evaporator prior to passing the refrigerant through the downstream portion of the evaporator. 
     The evaporator may comprise to separate units with a conduit extending between the two units, and wherein a T-junction splits the conduit between the upper and lower evaporator units. Alternately, the upstream and downstream portions of the evaporator may be interconnected by a rigid structure whereby the upstream and downstream portions of the evaporator form a single unit that can be moved prior to mounting the evaporator unit to a refrigerator, freezer, or the like. 
     These and other features, advantages, and objects of the present invention will be further understood and appreciated by those skilled in the art by reference to the following specification, claims, and appended drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of a cooling system according to one aspect of the present invention; 
         FIG. 2  shows a cooling system according to another aspect of the present invention; and; 
         FIG. 3  is a partially fragmentary view of an evaporator according to another aspect of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     For purposes of description herein, the terms “upper,” “lower,” “right,” “left,” “rear,” “front,” “vertical,” “horizontal,” and derivatives thereof shall relate to the invention as oriented in the drawing. However, it is to be understood that the invention may assume various alternative orientations, except where expressly specified to the contrary. It is also to be understood that the specific devices and processes illustrated in the attached drawing, and described in the following specifications are simply exemplary embodiments of the inventive concepts defined in the appended claims. Hence, specific dimensions and other physical characteristics relating to the embodiments disclosed herein are not to be considered as limiting, unless the claims expressly state otherwise. 
     With reference to the drawing, a cooling system  1  according to one aspect of the present invention includes a compressor  5 , a condenser  10 , and an evaporator  20 . Compressor  5  includes an exit port  5  that is fluidly connected to condenser  10  by a conduit  7 . Compressed refrigerant “CR” flows from the compressor  5  to the condenser  10 , and then flows through a conduit  8  to an expander such as capillary tube  9 . The capillary tube  9  and condenser  10  may comprise known units of a conventional construction as required for a particular application. The capillary tube  9  may also comprise a valve, or other device that lowers pressure of the refrigerant in a known manner. 
     The lower pressure refrigerant (“LPR”) flows from capillary tube  9  to an inlet  14  of evaporator  20  through a conduit  12 . Evaporator  20  includes an upstream portion  22  and a downstream portion  24 . A conduit  26  provides for flow of refrigerant through the upstream and downstream portions  22  and  24 , respectively, of evaporator  20 . Conduit  26  includes an upstream portion  28  and a downstream portion  30 . A T-joint in conduit  26  splits the stream of refrigerant into a first portion  1 R that flows through a conduit  34 , and a second portion “ 2 R” that flows through downstream portion  30  of conduit  26 . The second portion  2 R of the coolant flows through an optional second expander such as a capillary tube  19 , and then through downstream portion  30  of conduit  26  of downstream portion  24  of evaporator  20 . The refrigerant then flows from outlet  40  of downstream portion  24  of evaporator  20  through conduit  42 . Compressor  5  includes first and second suction or inlet ports  36  and  38  that draw refrigerant from evaporator  20  through conduits  34  and  42 , respectively. First and second valves  44  and  46  in conduits  34  and  42 , respectively are connected to a controller  50 . Compressor  5  and controller  50  may be operably connected to an electrical power source  52 . 
     In the illustrated example, the upstream and downstream portions  22  and  24 , respectively, of evaporator  20  are interconnected by a structure  48  that may comprise a plurality of heat exchanger fins or other heat exchanger surface or feature. Structure  48  may be configured such that evaporator  20  forms a single unit that can be installed to a refrigerator  18  or other appliance to cool an insulated space  17 . However, in most applications the heat exchanger fins  48  are not designed to structurally support the evaporator  20  or to structurally interconnect parts of the evaporator  20 . A fan  16  generates an airstream A 1  that flows over both the upstream and downstream portions  22  and  24 , respectively. Alternately, the upstream and downstream portions  22  and  24 , respectively, of evaporator  22  may comprise separate evaporator structures that are separated as shown schematically by the line “D.” The upstream and downstream portions  22  and  24  may be located in two separated insulated spaces  17 A and  17 B, respectively, that are separated by an insulated wall. Line D could comprise an insulated wall if configured in this way. A second fan  16 A may be utilized to generate a second stream of air that flows over downstream portion  24  of evaporator  20  in space  17 B. 
     In use, refrigerant from expander/capillary tube  9  enters the upstream portion  28  of conduit  26  as a single stream of refrigerant. As the refrigerant flows through the upstream portion  22  of evaporator  20 , the vapor quantity of the refrigerant increases as it absorbs heat. The conduit  26  thus becomes less and less flooded with liquid refrigerant along the refrigerant flow path of upstream portion  28  of conduit  26 . Because the internal surface of conduit  26  is in contact with less fluid as the amount of vapor increases, the amount of heat transferred into the refrigerant is reduced along the upstream portion  28  of conduit  26 . 
     In order to improve the transfer of heat, T-joint  32  is utilized to separate the refrigerant vapor, which is pulled into first inlet port  36  of compressor  5 . The first port  36  comprises a high pressure suction port of the compressor that provides greater vacuum relative to second inlet port  38 . 
     The refrigerant that is not split off at T-joint  32  flows through downstream portion  24  of evaporator  20  through downstream portion  30  of conduit  26 . Because much of the refrigerant in vapor form is separated at T-joint  32 , the second stream of refrigerant  2 R contains a higher percentage of liquid refrigerant than the refrigerant “RE” entering T-joint  32 . The second stream  2 R of refrigerant may pass through a second expander such as capillary tube  19  before passing through the downstream portion  30  of conduit  26 . This reduces the pressure of the refrigerant such that the refrigerant in downstream portion  30  of conduit  26  has a lower pressure than refrigerant in upstream portion  28  of conduit  26 . The second portion  2 R of the stream of refrigerant exits the downstream portion  24  of evaporator  20  at exit  40 , and flows into low pressure second inlet port  38  of compressor  5 . 
     Compressor  5  is configured to provide different pressure levels between the inlet ports  36  and  38  as required for a particular application. The suction ports  36  and  38  can preferably open and close independently and operate at different pressure levels. Valves  54  and  56  may be positioned at ports  36  and  38 , respectively, and valve  58  may be positioned at outlet port  6  of compressor  5 . Valves  54  and  56  may comprise spring-biased valves that open if a predefined vacuum level (pressure differential) exists between internal space  4  of compressor  5  and conduits  34  and  42 . Similarly, valve  58  may be configured to open and allow flow into conduit  7  if sufficient pressure is developed in internal space  4  of compressor  5 . The spring constants, valve sizes, and other factors can be varied such that valves  54 ,  56 , and  58  open at the required predefined vacuums. Also, valves  54 ,  56 , and  58  may be operably connected to controller  50  such that the opening vacuum and/or timing of valves  54 ,  56 , and  58  can be controlled during operation to account for varying operating conditions. Valves  44  and  46  can also be utilized to control the flow of refrigerant into first and second ports  36  and  38  of compressor  5 . 
     With further reference to  FIG. 2 , port  38 A may comprise a single port that is connected to a three-way valve  60  by a conduit or line  62 . Three-way valve  60  includes first and second input ports  64  and  66 , respectively, that are connected to conduits  34  and  42 , respectively. Output port  68  of three-way valve  60  is connected to conduit  62 . The three-way valve  60  comprises a powered solenoid valve that is operably coupled to controller  50 . 
     In use, three-way valve  60  is controlled to provide the required amount of suction on conduits  34  and  42  at the proper times. It will be understood that the operation of three-way valve  60  may be controlled based, at least in part, on a measured temperature inside appliance  18 , a measured ambient temperature, measured temperatures at various points, of refrigerant in the system and/or the vacuum/pressure levels within the system, as well as a desired (preset) target temperature for the space inside of appliance  18 . 
     In the illustrated example, the evaporator  20  includes an upstream portion  22  and a downstream portion  24 . It will be understood, however, that three or more portions may be utilized in conjunction with a compressor having three or more suction ports if required for a particular application. Furthermore, as discussed above, the upstream and downstream portions  22  and  24  of evaporator  20  may be rigidly interconnected by a structure  48  to form a single unit whereby the upstream and downstream portions  22  and  24  can be simultaneously installed or secured to a refrigerator  18  or other component. Alternately, the upstream and downstream portions  22  and  24  of evaporator  20  may comprise separate units that are fluidly interconnected by conduit  26  in operation, but may comprise structurally separate units that can be moved and installed separately. 
     With further reference to  FIG. 3 , a cooling system  1 A according to another aspect of the present invention includes an evaporator  20 A having an upstream or front conduit  28 A and a downstream or rear conduit  30 A. The conduits  28 A and  30 A are connected to cooling fins  48 A. Low pressure refrigerant “LPR” from a condenser  10  (not shown in  FIG. 3 ) flows into evaporator  20 A along a conduit  12 A corresponding to the conduit  12  described in more detail above in connection with  FIG. 1 . Refrigerant “RE” flows to a T-shaped joint  32 A and a portion of the refrigerant splits off and flows through conduit  34 A to form a stream  1 R that flows to compressor  5  (not shown in  FIG. 3 ). As discussed in more detail above in connection with  FIGS. 1 and 2 , the compressor may comprise a multi port unit ( FIG. 1 ) or a single port unit having an inlet fluidly connected to a 3-way valve ( FIG. 2 ). A second stream or portion “ 2 R” of the refrigerant passes through an optional capillary tube  19 A, and then through downstream conduit  30 A. Refrigerant flowing out of conduit  30 A flows through a conduit  42 A back to the compressor as described in more detail above. 
     Airflow “A 2 ” passes over the fins  48 A such that the air is cooled. The evaporator  20 A operates in substantially the same manner as the evaporator  20  described in more detail above in connection with  FIG. 1 . However, evaporator  20 A has a configuration that is suitable for use if the cooling system comprises an air conditioning unit. Accordingly, the space  17 A of  FIG. 3  may comprise an interior space of a building, vehicle, or other space to be cooled. 
     It is to be understood that variations and modifications can be made on the aforementioned structure without departing from the concepts of the present invention, and further it is to be understood that such concepts are intended to be covered by the following claims unless these claims by their language expressly state otherwise.