Patent Publication Number: US-2019168582-A1

Title: Multi-temperature transportation refrigeration system

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to U.S. Provisional Application No. 62/593,294 filed on Dec. 1, 2017. 
    
    
     BACKGROUND 
     This application relates to a multi-temperature transportation refrigeration system which cools two distinct environments to different temperatures and utilizes a common condenser. 
     Refrigeration systems are known. Generally, a compressor compresses a refrigerant and delivers it into a condenser. The refrigerant is cooled and passes through an expansion valve. The refrigerant is expanded and passes through an evaporator. The evaporator cools air to be delivered into an environment to be conditioned. 
     One application for such refrigeration systems is in a transportation refrigeration system. As an example, a truck may have a refrigerated trailer. It is known to provide distinct temperatures at distinct compartments within a common trailer. Individual refrigeration circuits are often utilized to provide the distinct temperatures. 
     SUMMARY 
     In a featured embodiment, a transportation refrigeration system includes an enclosure, and at least two compartments within the enclosure to be conditioned to two distinct temperatures. The system has at least two refrigeration circuits, with a refrigeration circuit associated with each of the at least two compartments. A first of the at least two refrigeration circuits includes a first compressor, a first evaporator, and a first expansion valve. A second of the at least two refrigeration circuits includes a second compressor, a second evaporator, and a second expansion valve. The first and second refrigerant circuits utilize a common condenser, with first inlets into the condenser from the first circuit connected to a first flow passage and second inlets from the second circuit connected to second flow passages. First and second outlets are connected to the first and second flow passages, respectively. The first and second flow passages are staggered in a direction perpendicular to a flow passage across the condenser. 
     In another featured embodiment, a heat exchanger has first refrigeration circuit inlets leading to a plurality of first flow passages across a dimension of the heat exchanger, and second refrigeration circuit inlets leading to a plurality of second flow passages across the dimension of the heat exchanger, with the first and second flow passages being staggered across a direction parallel to the dimension. 
     These and other features may be best understood from the following drawings and specification. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  schematically shows a refrigeration transportation system. 
         FIG. 2A  shows a first embodiment condenser that may be utilized in the  FIG. 1  environment. 
         FIG. 2B  shows a second embodiment condenser. 
         FIG. 2C  shows a third embodiment condenser. 
         FIG. 2D  shows a fourth embodiment condenser. 
     
    
    
     DETAILED DESCRIPTION 
     A refrigerated enclosure  20  is illustrated in  FIG. 1 . As known, the enclosure may be a refrigerated trailer associated with a truck. However, other applications for refrigerated enclosures may benefit from this disclosure. For purposes of this application, the term “enclosure” should extend to all enclosures, such as trailers, shipboard containers, etc. 
     Two distinct compartments  22  and  24  are illustrated. These two compartments are desirably cooled to distinct temperatures. As an example, one may be cooled to a lower temperature than the other. One may desirably maintain items stored within the compartment at a temperature below freezing, while the other may be at a higher, but still cooled, temperature. 
     The refrigeration circuit  26  is provided to maintain the compartment  22  at its temperature. A refrigeration circuit  28  is provided to maintain the compartment  24  at its temperature. 
     Refrigeration circuit  26  includes an evaporator  30 . As known, a fan pulls air across the evaporator  30  to cool the air to the desired temperature for the compartment  22 . 
     Downstream of the evaporator  30 , the refrigerant passes to a first compressor  32  and then into a line  34  leading to inlets  35  into a condenser  36 . Outlet lines  38  for the first circuit pass through an expansion valve  40  and back to the evaporator  30 . 
     The circuit  28  includes an evaporator  42 . Again, a fan will pull air across the evaporator  42  to cool it to the desired temperature for the compartment  24 . 
     Downstream of the evaporator  42 , the refrigerant passes to a second compressor  44  and then to a line  46  leading to inlet lines  48  into the condenser  36 . Outlet lines  50  pass through an expansion valve  52  and back to the evaporator  42 . 
     An engine or other power source  54  is shown to power both compressors  32  and  44 . 
     As shown in this Figure, the inlet lines  35  and  48  are staggered. That is, they are interspersed in a direction perpendicular to a flow direction through the condenser  36 . Notably,  FIG. 1  is a schematic view and the flow direction may actually be across the larger dimension of the condenser  36  (in this Figure between the left and right). 
       FIG. 2A  shows a first embodiment  36  of the condenser.  FIG. 2A  may be a multi-louver flat-tube heat exchanger (alternatively referred to as “microchannel heat exchanger”). As known, microchannel heat exchangers have a plurality of channels spaced into the plane of this Figure and which provide very efficient heat transfer. The line  34  leads to a plurality of inlets  35  and passes to outlets  38  at an opposed end of the heat exchanger  36 . Similarly, the line  46  leads to inlets  48  and outlets  50 . As can be appreciated, the inlets  35  and  48  of the two circuits are staggered or interspersed in a direction perpendicular to a flow direction across the heat exchanger  36 . The same is true of the outlets  38  and  50 . 
     Multi-louver fins F assist in cooling the refrigerant in the heat exchanger, which are brazed to the flat tube. 
       FIG. 2B  shows another embodiment  136 , which is also a microchannel heat exchanger but with two-slab arrangement. The two circuits  134  and  146  enter into the heat exchanger on a first end and the outlets  138  and  150  are also at the first end. The actual structure of the channels across the heat exchanger may be as shown at  158 . The first slab  162  passes across the dimension of the heat exchanger, reaches a turning elbow (which can be a folded unfinned flat tube)  160  and return back through the second slab  164  to the outlet. Although  FIG. 2B  only shows a 2-slab configuration, multi-slab (more than 3 slabs) configurations also belong to this scope of this invention. 
       FIG. 2C  shows an embodiment  236 . This embodiment may be a round tubes plate fin (P L ) heat exchanger. The inlet circuits  234  and  246  enter on one end to the circuits  235  and  248 . The refrigerant passes across the heat exchanger to the outlets  238  and  250 . 
       FIG. 2D  shows another embodiment  336 , which may be also a round tube plate fin heat exchanger. Here, the inlet circuits  334  and  346  enter at one end to inlets  335  and  348 . The outlets  338  and  350  are at the same end. 
     Again, a tube structure  358  is utilized. The inlets pass into a tube  362  to a turning elbow  360 , which may be a hairpin bend, and back to an outlet tube  364 . 
     In each of the  FIGS. 2A-D , first flow passages P 1  connect the first circuit inlets to first circuit outlets, and second flow passages P 2  connect the second circuit inlets to second circuit outlets. 
     While the embodiments in  FIGS. 2A-2D  are specifically disclosed as a condenser, a worker of ordinary skill in the art would recognize that other applications for the heat exchanger may benefit from this disclosure. As an example, the heat exchanger may be utilized in an evaporator, an economizer, etc. Generally, any refrigeration system having two refrigerant flows that desirably have cooling or heating may benefit from these several designs. 
     For purposes of this application, the term “staggered” can be taken to mean there is a first flow passage of a first circuit and a first flow passage of a second circuit spaced perpendicular to the first flow passage of the first circuit in a direction perpendicular to a flow direction across the heat exchanger. Further, there is a second flow passage of the first flow circuit spaced on an opposed side of the first flow passage of the second circuit from the first flow passage of the first circuit, and a second flow passage of the second circuit spaced on an opposed side of the second flow passage of the first circuit relative to the first flow passage of the second circuit. 
     The staggered arrangement provides valuable benefits to increase efficiency. As an example, should one of the two circuits  26  or  28  be stopped, the entire air side heat transfer surface area of the heat exchanger will still be utilized to cool the other circuit. In addition, it is known that the heat exchange capacity for a particular heat exchanger is dependent on the temperature of the refrigerant entering the heat exchanger. Thus, the heat exchanger will cool the refrigerant at a higher inlet temperature to a greater extent than the second refrigerant at the lower temperature and thus the automatic allocation of air-side heat transfer surface area is achieved 
     Although an embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this disclosure. For that reason, the following claims should be studied to determine the true scope and content of this disclosure.