Patent Publication Number: US-2023143887-A1

Title: Water box mixing manifold

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority from and the benefit of U.S. Provisional Application Ser. No. 62/982,582, entitled “WATER BOX MIXING MANIFOLD,” filed Feb. 27, 2020, which is hereby incorporated by reference in its entirety for all purposes. 
    
    
     BACKGROUND 
     This disclosure relates generally to vapor compression systems, and more particularly, to a system for measuring a fluid temperature in vapor compression systems. 
     This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art. 
     Vapor compression systems, such as chiller systems, utilize a working fluid (e.g., a refrigerant) that changes phases between vapor, liquid, and combinations thereof, in response to exposure to different temperatures and pressures within components of the vapor compression system. The chiller system may place a working fluid in a heat exchange relationship with a conditioning fluid and may deliver the conditioning fluid to conditioning equipment and/or a conditioned environment serviced by the chiller system. In some cases, a heating, ventilation, air conditioning, and/or refrigeration (HVAC&amp;R) system may include multiple chiller systems, and each chiller system may circulate a respective working fluid. Each working fluid may remove heat from a flow of conditioning fluid that is placed in a heat exchange relationship with the respective working fluid via a component (e.g., an evaporator) of the chiller system. In such embodiments, each chiller system may also have a condenser configured to cool heated working fluid. For example, a cooling fluid, such as a water or air flow, may be directed through or across the respective condenser of each chiller system to cool the respective working fluid. The various components of each chiller system may be controlled individually to balance or distribute a load shared by the chiller systems. Unfortunately, variations in the working fluids and/or conditioning fluids at different locations within the chiller systems may complicate effective balancing of the load. 
     SUMMARY 
     In an embodiment of the present disclosure, a heating, ventilation, air conditioning, and refrigeration (HVAC&amp;R) system includes a heat exchanger with a shell having a first pass configured to place a fluid in a heat exchange relationship with a first refrigerant and a second pass configured to place the fluid in a heat exchange relationship with a second refrigerant. The heat exchanger also includes a water box coupled to the shell and configured to direct the fluid from the first pass to the second pass. The HVAC&amp;R system also includes a fluid mixing manifold disposed within the water box, where the fluid mixing manifold is configured to collect and mix a plurality of flows of the fluid from within the water box to generate a mixed fluid, and a sensor coupled to the fluid mixing manifold, where the sensor is configured to measure a parameter of the mixed fluid. 
     In another embodiment, a heat exchanger includes a water box configured to direct a fluid from a first pass of the heat exchanger to a second pass of the heat exchanger and a fluid mixing manifold disposed within the water box. The fluid mixing manifold includes a plurality of sampling conduits configured to collect and mix a plurality of flows of the fluid from a respective plurality of locations within the water box, a mixing junction fluidly coupled to each sampling conduit of the plurality of sampling conduits, where the mixing junction is configured to mix the plurality of flows of the fluid to generate a mixed fluid, and a discharge port fluidly coupled to the mixing junction and configured to discharge the mixed fluid into the water box. 
     In a further embodiment, a heating, ventilation, air conditioning, and refrigeration (HVAC&amp;R) system includes a heat exchanger having a shell, a water box coupled to the shell, a partition disposed within the shell to define a first volume within the shell and a second volume within the shell, a first subset of tubes disposed within the first volume and configured to direct a fluid into the water box, and a second subset of tubes disposed within the second volume and configured to receive the fluid from the water box. The HVAC&amp;R system also includes a fluid mixing manifold disposed within the water box. The fluid mixing manifold is configured to collect a plurality of flows of the fluid from a respective plurality of locations arrayed along a height of the water box and configured to mix the plurality of flows to generate a mixed fluid. The HVAC&amp;R system further includes a temperature sensor disposed within the fluid mixing manifold and configured to detect a temperature of the mixed fluid. 
    
    
     
       DRAWINGS 
       Various aspects of this disclosure may be better understood upon reading the following detailed description and upon reference to the drawings in which: 
         FIG.  1    is a perspective view of an embodiment of a building that may utilize a heating, ventilation, air conditioning, and refrigeration (HVAC&amp;R) system in a commercial setting, in accordance with an aspect of the present disclosure; 
         FIG.  2    is a perspective view of an embodiment of a vapor compression system, in accordance with an aspect of the present disclosure; 
         FIG.  3    is a schematic of an embodiment of a vapor compression system, in accordance with an aspect of the present disclosure; 
         FIG.  4    is a schematic of an embodiment of a vapor compression system of, in accordance with an aspect of the present disclosure; 
         FIG.  5    is a schematic of an embodiment of a vapor compression system having multiple refrigerant circuits in a series counter-flow arrangement, in accordance with an aspect of the present disclosure; 
         FIG.  6    is a schematic side view of an embodiment of a heat exchanger implemented with two refrigerant circuits of an HVAC&amp;R system, in accordance with an aspect of the present disclosure; 
         FIG.  7    is a schematic axial view of an embodiment of a heat exchanger implemented with two refrigerant circuits of an HVAC&amp;R system, in accordance with an aspect of the present disclosure; 
         FIG.  8    is a perspective view of an embodiment of a water box having a fluid mixing manifold, in accordance with an aspect of the present disclosure; and 
         FIG.  9    is a schematic of an embodiment of a control system for an HVAC&amp;R system having two refrigerant circuits and a fluid mixing manifold, in accordance with an aspect of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     One or more specific embodiments of the present disclosure will be described below. These described embodiments are examples of the presently disclosed techniques. Additionally, in an effort to provide a concise description of these embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers&#39; specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure. 
     When introducing elements of various embodiments of the present disclosure, the articles “a,” “an,” and “the” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. Additionally, it should be understood that references to “one embodiment” or “an embodiment” of the present disclosure are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. 
     Embodiments of the present disclosure are directed towards a fluid mixing manifold that may be utilized in a heat exchanger of a vapor compression system, such as a heating, ventilation, air conditioning, and refrigeration (HVAC&amp;R) system. More specifically, present embodiments include a fluid mixing manifold configured to sample fluid from different locations within a heat exchanger and mix the sampled fluids to generate a mixed fluid. The temperature of the mixed fluid may be measured for use in controlling operation of the vapor compression system or other system utilized with the vapor compression system and the heat exchanger. 
     For example, the heat exchanger may include a shell and a plurality of tubes disposed within the shell that is configured to direct a cooling fluid or conditioning fluid (e.g., water) therethrough. As the cooling or conditioning fluid is directed through the plurality of tubes, a working fluid (e.g., refrigerant) may be directed through the shell of the heat exchanger, such that heat is transferred between the cooling or conditioning fluid and the working fluid. In some embodiments, the heat exchanger may be a multi-pass heat exchanger. That is, the heat exchanger may be configured to direct the cooling or conditioning fluid along a first pass of the heat exchanger to exchange heat with refrigerant (e.g., a first refrigerant) and to subsequently direct the cooling or conditioning fluid along a second pass of the heat exchanger to exchange heat with refrigerant (e.g., a second refrigerant). To this end, the heat exchanger may include a water box (e.g., cooling fluid box, conditioning fluid box, etc.) that is coupled to the shell and is configured to re-direct the cooling or conditioning fluid from the first pass of the heat exchanger to the second pass of the heat exchanger. The plurality of tubes disposed within the shell may be divided into a first subset of tubes that define the first pass and a second subset of tubes that define the second pass. In operation, cooling or conditioning fluid is directed through the first subset of tubes and into the water box, and the water box directs the cooling or conditioning fluid into the second subset of tubes. In some embodiments, the first subset of tubes may be disposed within a first portion of the shell associated with a first refrigerant circuit of the vapor compression system, and the second subset of tubes may be disposed within a second portion of the shell, fluidly separate from the first portion, associated with a second refrigerant circuit of the vapor compression system. As will be appreciated, it may be desirable to control the vapor compression system based on a temperature of the cooling or conditioning fluid within the water box between the first pass and the second pass. 
     The plurality of tubes may be arranged in bundles within the shell such that the tubes are positioned at different locations (e.g., heights) within the shell. Due to variances in individual heat transfer performance of the tubes (e.g., based on a respective location of each tube within the shell), the cooling or conditioning fluid flowing through the tubes may not be homogeneous in temperature. In other words, the cooling or conditioning fluid exiting one tube of the plurality of tubes may have a different temperature than the cooling or conditioning fluid exiting another tube of the plurality of tubes. For example, the cooling or conditioning fluid directed into the water box via a first tube of the first subset of tubes may have a different temperature than the cooling or conditioning fluid directed into the water box via a second tube of the first subset of tubes. In order to determine an average temperature of the cooling or conditioning fluid within the water box, present embodiments are directed to a fluid mixing manifold configured to sample fluid at different locations within the water box and mix the sampled fluids to generate a mixed fluid. The temperature of the mixed fluid may be measured and may be used to control operation of the vapor compression system. Further, as discussed in detail below, the configuration of the fluid mixing manifold enables more accurate temperature measurements of the fluid for use in controlling operation of the vapor compression system and also enables a reduction in pressure drop of the fluid within the water box compared to traditional systems that are configured to generate a mixed fluid within the water box, such as via baffles disposed within the water box. 
     Turning now to the drawings,  FIG.  1    is a perspective view of an embodiment of an environment for a heating, ventilation, air conditioning, and refrigeration (HVAC&amp;R) system  10  in a building  12  for a typical commercial setting. The HVAC&amp;R system  10  may include a vapor compression system  14  that supplies a chilled liquid, which may be used to cool the building  12 . The HVAC&amp;R system  10  may also include a boiler  16  to supply warm liquid to heat the building  12  and an air distribution system which circulates air through the building  12 . The air distribution system can also include an air return duct  18 , an air supply duct  20 , and/or an air handler  22 . In some embodiments, the air handler  22  may include a heat exchanger that is connected to the boiler  16  and the vapor compression system  14  by conduits  24 . The heat exchanger in the air handler  22  may receive either heated liquid from the boiler  16  or chilled liquid from the vapor compression system  14 , depending on the mode of operation of the HVAC&amp;R system  10 . The HVAC&amp;R system  10  is shown with a separate air handler on each floor of building  12 , but in other embodiments, the HVAC&amp;R system  10  may include air handlers  22  and/or other components that may be shared between or among floors. 
       FIGS.  2  and  3    illustrate embodiments of the vapor compression system  14  that can be used in the HVAC&amp;R system  10 . The vapor compression system  14  may circulate a refrigerant through a circuit starting with a compressor  32 . The circuit may also include a condenser  34 , an expansion valve(s) or device(s)  36 , and a liquid chiller or an evaporator  38 . The vapor compression system  14  may further include a control panel  40  that has an analog to digital (A/D) converter  42 , a microprocessor  44 , a non-volatile memory  46 , and/or an interface board  48 . 
     Some examples of fluids that may be used as refrigerants in the vapor compression system  14  are hydrofluorocarbon (HFC) based refrigerants, for example, R-410A, R-407, R-134a, hydrofluoro olefin (HFO), “natural” refrigerants like ammonia (NH3), R-717, carbon dioxide (CO2), R-744, or hydrocarbon based refrigerants, water vapor, or any other suitable refrigerant. In some embodiments, the vapor compression system  14  may be configured to efficiently utilize refrigerants having a normal boiling point of about 19 degrees Celsius (66 degrees Fahrenheit) at one atmosphere of pressure, also referred to as low pressure refrigerants, versus a medium pressure refrigerant, such as R-134a. As used herein, “normal boiling point” may refer to a boiling point temperature measured at one atmosphere of pressure. 
     In some embodiments, the vapor compression system  14  may use one or more of a variable speed drive (VSDs)  52 , a motor  50 , the compressor  32 , the condenser  34 , the expansion valve or device  36 , and/or the evaporator  38 . The motor  50  may drive the compressor  32  and may be powered by a variable speed drive (VSD)  52 . The VSD  52  receives alternating current (AC) power having a particular fixed line voltage and fixed line frequency from an AC power source, and provides power having a variable voltage and frequency to the motor  50 . In other embodiments, the motor  50  may be powered directly from an AC or direct current (DC) power source. The motor  50  may include any type of electric motor that can be powered by a VSD or directly from an AC or DC power source, such as a switched reluctance motor, an induction motor, an electronically commutated permanent magnet motor, or another suitable motor. 
     The compressor  32  compresses a refrigerant vapor and delivers the vapor to the condenser  34  through a discharge passage. In some embodiments, the compressor  32  may be a centrifugal compressor. The refrigerant vapor delivered by the compressor  32  to the condenser  34  may transfer heat to a cooling fluid (e.g., water or air) in the condenser  34 . The refrigerant vapor may condense to a refrigerant liquid in the condenser  34  as a result of thermal heat transfer with the cooling fluid. The liquid refrigerant from the condenser  34  may flow through the expansion device  36  to the evaporator  38 . In the illustrated embodiment of  FIG.  3   , the condenser  34  is water cooled and includes a tube bundle  54  connected to a cooling tower  56 , which supplies the cooling fluid to the condenser  34 . 
     The liquid refrigerant delivered to the evaporator  38  may absorb heat from another cooling fluid (e.g., a conditioning fluid), which may or may not be the same cooling fluid used in the condenser  34 . The liquid refrigerant in the evaporator  38  may undergo a phase change from the liquid refrigerant to a refrigerant vapor. As shown in the illustrated embodiment of  FIG.  3   , the evaporator  38  may include a tube bundle  58  having a supply line  60 S and a return line  60 R connected to a cooling load  62 . The conditioning fluid of the evaporator  38  (e.g., water, ethylene glycol, calcium chloride brine, sodium chloride brine, or any other suitable fluid) enters the evaporator  38  via return line  60 R and exits the evaporator  38  via supply line  60 S. The evaporator  38  may reduce the temperature of the conditioning fluid in the tube bundle  58  via thermal heat transfer with the refrigerant. The tube bundle  58  in the evaporator  38  can include a plurality of tubes and/or a plurality of tube bundles. In any case, the vapor refrigerant exits the evaporator  38  and returns to the compressor  32  by a suction line to complete the cycle. 
       FIG.  4    is a schematic of an embodiment of the vapor compression system  14  with an intermediate circuit  64  incorporated between condenser  34  and the expansion device  36 . The intermediate circuit  64  may have an inlet line  68  that is directly fluidly connected to the condenser  34 . In other embodiments, the inlet line  68  may be indirectly fluidly coupled to the condenser  34 . As shown in the illustrated embodiment of  FIG.  4   , the inlet line  68  includes a first expansion device  66  positioned upstream of an intermediate vessel  70 . In some embodiments, the intermediate vessel  70  may be a flash tank (e.g., a flash intercooler). In other embodiments, the intermediate vessel  70  may be configured as a heat exchanger or a “surface economizer.” In the illustrated embodiment of  FIG.  4   , the intermediate vessel  70  is used as a flash tank, and the first expansion device  66  is configured to lower the pressure of (e.g., expand) the liquid refrigerant received from the condenser  34 . During the expansion process, a portion of the liquid may vaporize, and thus, the intermediate vessel  70  may be used to separate the vapor from the liquid received from the first expansion device  66 . Additionally, the intermediate vessel  70  may provide for further expansion of the liquid refrigerant due to a pressure drop experienced by the liquid refrigerant when entering the intermediate vessel  70  (e.g., due to a rapid increase in volume experienced when entering the intermediate vessel  70 ). The vapor in the intermediate vessel  70  may be drawn by the compressor  32  through a suction line  74  of the compressor  32 . In other embodiments, the vapor in the intermediate vessel may be drawn to an intermediate stage of the compressor  32  (e.g., not the suction stage). The liquid that collects in the intermediate vessel  70  may be at a lower enthalpy than the liquid refrigerant exiting the condenser  34  due to the expansion in the expansion device  66  and/or the intermediate vessel  70 . The liquid from intermediate vessel  70  may then flow in line  72  through a second expansion device  36  to the evaporator  38 . 
     As mentioned above, a heat exchanger of the vapor compression system  14  may include a shell having a plurality of tubes disposed therein, where the plurality of tubes is configured to direct a cooling fluid or conditioning fluid (e.g., water) therethrough, and the shell is configured to direct a working fluid (e.g., refrigerant) therethrough to enable heat transfer between the cooling or conditioning fluid and the working fluid. In some embodiments, the heat exchanger may be a multi-pass heat exchanger configured to direct the cooling or conditioning fluid through multiple passes that are defined by different subsets of tubes. In some multi-pass heat exchanger embodiments, each pass of the heat exchanger may be associated with a separate refrigerant circuit that circulates a respective refrigerant therethrough. For example, the vapor compression system  14  may include multiple refrigerant circuits, and condensers of the multiple refrigerant circuits may be packaged together in a common heat exchanger shell and/or evaporators of the multiple refrigerant circuits may be packaged together in a common heat exchanger shell. The heat exchanger further includes a water box configured to direct the cooling or conditioning fluid from the tubes of the first pass to the tubes of the second pass. 
       FIG.  5    is a schematic of an embodiment of the vapor compression system  14  with multiple refrigerant circuits  80  (e.g., refrigerant loops). In particular, the illustrated embodiment includes a first refrigerant circuit  82  and a second refrigerant circuit  84  arranged in a series counter-flow arrangement. The first refrigerant circuit  82  includes a first compressor  32 A, a first condenser  34 A, a first expansion device  36 A, and a first evaporator  38 A. The second refrigerant circuit  84  includes a second compressor  32 B, a second condenser  34 B, a second expansion device  36 B, and a second evaporator  38 B. Each of the refrigerant circuits  80  is configured to circulate a respective refrigerant therethrough and is configured to operate in a manner similar to that described above with reference to the vapor compression system  14  shown in  FIGS.  2 - 4   . It should be noted that each of the refrigerant circuits  80  may also include components in addition to those shown in  FIGS.  2 - 4   . 
     In the illustrated embodiment, the first and second refrigerant circuits  82  and  84  of the vapor compression system  14  are arranged in a series counter-flow arrangement. Specifically, the first and second evaporators  38 A and  38 B define a portion of a conditioning fluid flow path or circuit  86  that extends from a cooling load  88  (e.g., air handlers  22 ), sequentially through the second evaporator  38 B and the first evaporator  38 A, and back to the cooling load  88 . Similarly, the first and second condensers  34 A and  34 B define a portion of a cooling fluid flow path or circuit  90  that extends from a cooling fluid source  92  (e.g., cooling tower  56 ), sequentially through the first condenser  34 A and the second condenser  34 B, and back to the cooling fluid source  92 . Thus, conditioning fluid is directed through the vapor compression system  14  first through the second evaporator  38 B and then through the first evaporator  38 A, while cooling fluid is directed through the vapor compression system  14  first through the first condenser  34 A and then through the second condenser  34 B, thereby providing the series counter-flow arrangement. 
     As mentioned above, heat exchangers of the multiple refrigerant circuits  80  may be packaged together in a common heat exchanger shell. For example, in some embodiments, the first and second condensers  34 A and  34 B may be packaged in a common heat exchanger shell and/or first and second evaporators  38 A and  38 B may be packaged in a common heat exchanger shell. The common heat exchanger shell may be divided into a first pass and a second pass that are each associated with a respective heat exchanger of one of the refrigerant circuits  80 . The first and second passes of the common heat exchanger shell may direct a cooling fluid or a conditioning fluid sequentially through tubes disposed within the first pass and tubes disposed within the second pass. To this end, the common heat exchanger shell may include a water box configured to re-direct a flow of the conditioning fluid from the tubes of the first pass to tubes of the second pass. 
     For example,  FIG.  6    is a cross-sectional schematic of a heat exchanger  100  (e.g., packaged heat exchanger, dual circuit heat exchanger, evaporator, condenser, etc.) that may be included in the vapor compression system  14 . The heat exchanger  100  includes a first water box  102  and a second water box  104 . The first water box  102  and the second water box  104  are coupled to a shell  106  of the heat exchanger  100  that has a plurality of tubes  108  disposed therein. The plurality of tubes  108  may be arranged and/or divided into tube bundles. The shell  106 , the first water box  102 , and the second water box  104  may be secured to one another via flanges  110 . While the illustrated embodiment of  FIG.  6    shows the flanges  110  having a larger diameter than the shell  106 , the first water box  102 , and/or the second water box  104 , in other embodiments, the flanges  110  may include the same diameter as each of the shell  106 , first water box  102 , and/or second water box  104 . Further, in other embodiments, the shell  106 , the first water box  102 , and/or the second water box  104  may be coupled to one another using another suitable technique (e.g., welding). Additionally, in some embodiments, each of the shell  106 , the first water box  102 , and/or the second water box  104  may be separate components that may be interchanged by coupling and/or removing such components from one another. 
     As mentioned above, the plurality of tubes  108  is arranged in one or more tube bundles  112  within the shell  106 . In embodiments of the heat exchanger  100  configured as one or more flooded evaporators, a conditioning fluid (e.g., water, chilled fluid, etc.) is circulated through the plurality of tubes  108 , and heat is transferred from the conditioning fluid to a refrigerant  114  that enters the shell  106  through an inlet  116  at a bottom of the shell  106 . As heat is transferred from the conditioning fluid within the tubes  108  to the refrigerant  114 , the refrigerant  114  evaporates and ultimately exits the shell  106  via an outlet  118  positioned at a top of the shell  106 . It should be appreciated that the techniques disclosed herein may be utilized with heat exchangers  100  having other configurations. For example, the heat exchanger  100  may be a falling film evaporator, a hybrid falling film evaporator, a condenser, or other type of heat exchanger, and thus, the refrigerant  114  may enter and exit the shell  106  of the heat exchanger  100  at locations of the shell  106  other than those shown in  FIG.  6   . For example, in an embodiment of the heat exchanger  100  configured as a falling film evaporator, the inlet  116  and the outlet  118  may be positioned at a top of the shell  106 . 
     In accordance with present techniques, the heat exchanger  100  may be configured as a multi-pass heat exchanger. More specifically, the plurality of tubes  108  within the shell  106  may be divided into a first subset of tubes and a second subset of tubes, where each subset of tubes is associated with a separate pass of the heat exchanger  100 . In the illustrated embodiment, conditioning fluid  120  (e.g., water) enters the heat exchanger  100  via an inlet  122  of the first water box  102 . However, in other embodiments, a cooling fluid, process fluid, or other fluid may enter the heat exchanger  100  via the inlet  102 . The conditioning fluid  120  is directed from the first water box  102  to a first subset of the plurality of tubes  108 , such that the conditioning fluid  120  flows through a first pass of the heat exchanger  100 , as indicated by arrow  124 . The conditioning fluid  120  exits the first subset of the plurality of tubes  108  and enters the second water box  104 , which directs and/or redirects the conditioning fluid  120  to a second subset of the plurality of tubes  108 , as indicated by arrow  126 . The second subset of the plurality of tubes  108  defines a second pass of the heat exchanger  100 . After the conditioning fluid  120  exits the second subset of the plurality of tubes  108 , the conditioning fluid  120  may flow into the first water box  102  and may exit the first water box  102  via an outlet (not shown). To this end, the first water box  102  may include a partition plate configured to separate the conditioning fluid  120  flowing through the first water box  102  from the inlet  122  to the first subset of the plurality of tubes  108  and the conditioning fluid  120  flowing through the first water box  102  from the second subset of the plurality of tubes  108  to the outlet. The first and second passes of the heat exchanger  100  and the first and second subsets of the plurality of tubes  108  are shown in greater detail in  FIG.  7   . 
     As mentioned above, embodiments of the present disclosure are directed to a fluid mixing manifold  128  configured to sample and mix fluid flowing through the heat exchanger  100 . More specifically, in the illustrated embodiment, the fluid mixing manifold  128  is positioned within the second water box  104  and is configured to sample conditioning fluid  120  flowing through the second water box  104  at different locations within the second water box  104 . The fluid mixing manifold  128  is further configured to mix the sampled conditioning fluid  120  to generate mixed conditioning fluid  120 . As noted above, the conditioning fluid  120  exiting each tube  108  in the first pass of the heat exchanger  100  may vary in temperature, for example, due to the individual heat transfer efficiency of each tube  108 , among other factors. Thus, by sampling the conditioning fluid  120  at different locations within the second water box  104  and mixing the sampled conditioning fluid  120  to generate the mixed conditioning fluid  120 , the fluid mixing manifold  128  enables efficient detection of an average temperature of the conditioning fluid  120  within the second water box  104  (e.g., between the first pass and the second pass of the heat exchanger  100 ). The detected average temperature of the conditioning fluid  120  within the second water box  104  and between the first and second passes of the heat exchanger  100  may be used as feedback to regulate operation of components of a system having the heat exchanger  100 , such as the vapor compression system  14 . 
       FIG.  7    is a schematic axial view of the heat exchanger  100 , illustrating a first pass  140  and a second pass  142  of the heat exchanger  100 . As mentioned above, the plurality of tubes  108  disposed within the shell  106  may be divided into a first subset  144  and a second subset  146 . In the illustrated embodiment, the first subset  144  of tubes  108  defines the first pass  140  of the heat exchanger  100 , and the second subset  146  of tubes  108  defines the second pass  142  of the heat exchanger  100 . The first subset  144  of tubes  108  is positioned within a first volume  148  of the shell  106 , and the second subset  146  of tubes  108  is positioned within a second volume  150  of the shell  106 , whereby the first and second volumes  148  and  150  are divided or separated by a partition plate  152  disposed within the shell  106 . 
     In some embodiments, the first and second passes  140  and  142  may each be associated with a respective refrigerant circuit configured to circulate a respective refrigerant. Thus, the heat exchanger  100  may be a component of a multi-circuit system (e.g., a two refrigerant circuit chiller). For example, the first pass  140  and the first volume  148  of the shell  106  may be components of the second evaporator  38 B of the second refrigerant circuit  84  shown in  FIG.  5   , and the second pass  142  and the second volume  150  of the shell  106  may be components of the first evaporator  38 A of the first refrigerant circuit  82  shown in  FIG.  5   . In some embodiments, the first pass  140  and the first volume  148  of the shell  106  may be components of the first condenser  34 A of the first refrigerant circuit  82 , and the second pass  142  and the second volume  150  of the shell  106  may be components of the second condenser  34 B of the second refrigerant circuit  84 . Thus, the heat exchanger  100  of the illustrated embodiment may include two heat exchangers (e.g., two evaporators, two condensers) packaged together in the shell  106 . The following discussion describes operation of the heat exchanger  100  as including two evaporators packaged together in the shell  106 , but it should be appreciated that other embodiments of the heat exchanger  100  may include two condensers packaged together. 
     As shown, a first refrigerant  154  is directed into the first volume  148  of the heat exchanger  100  via an inlet  156  of the shell  106 . As described above, conditioning fluid  120  enters the first subset  144  of tubes  108  via the first water box  102 . As the conditioning fluid  120  flows through the first subset  144  of tubes  108  in the first volume  148  (e.g. the first pass  140 ), heat is transferred from the conditioning fluid  120  to the first refrigerant  154 , which may cool the conditioning fluid  120  and cause the first refrigerant  154  to evaporate. The evaporated first refrigerant  154  may then exit the first volume  148  of the shell  106  via an outlet  158  of the shell  106  and continue circulating through the refrigerant circuit associated with the first volume  148  and first pass  140  (e.g., second refrigerant circuit  84 ). 
     Similarly, a second refrigerant  160  is directed into the second volume  150  of the heat exchanger  100  via an inlet  162  of the shell  106 . As mentioned above, the second refrigerant  160  and the first refrigerant  154  may be directed via separate refrigerant circuits (e.g., first and second refrigerant circuits  82  and  84 ). Conditioning fluid  120  is directed into the second subset  146  of tubes  108  from the second water box  104 , as described above. As the conditioning fluid  120  flows through the second subset  146  of tubes  108  in the second volume  150  (e.g. the second pass  142 ), heat is transferred from the conditioning fluid  120  to the second refrigerant  160 , which may further cool the conditioning fluid  120  and cause the second refrigerant  160  to evaporate. The evaporated second refrigerant  160  may then exit the second volume  150  of the shell  106  via an outlet  164  of the shell  106  continue circulating through the refrigerant circuit associated with the second volume  150  and second pass  142  (e.g., first refrigerant circuit  82 ). 
     As will be appreciated, it may be desirable to divide or balance a cooling load of the heat exchanger  100  between the two refrigerant circuits. To this end, respective components of the multiple refrigerant circuits may be individually operated to achieve a desired balance of the cooling load between the refrigerant circuits, and operation of the respective components of the multiple refrigerant circuits may be based, at least in part, on an average temperature of the conditioning fluid  120  within the second water box  104  (e.g., the conditioning fluid  120  between the first and second passes  140  and  142 ). Thus, present embodiments are directed to the fluid mixing manifold  128 , which enables measurement of an average temperature of the conditioning fluid  120  within the second water box  104  while also mitigating pressure drop of the conditioning fluid  120  within the second water box  104 . As discussed in further detail below, the fluid mixing manifold  128  is configured to sample conditioning fluid  120  within the second water box  104  at different locations (e.g., relative to a height  166  of the heat exchanger  100 ) within the second water box  104 . In this way, the fluid mixing manifold  128  is configured to mix portions the conditioning fluid  120  within the second water box  104  to generate mixed conditioning fluid  120 , the temperature of which may be measured to obtain and/or approximate an average temperature of the conditioning fluid  120  within the second water box  104 . 
       FIG.  8    is a perspective view of an embodiment of the second water box  104 , illustrating an embodiment of the fluid mixing manifold  128  disposed therein. The second water box  104  has a main body  180  (e.g., dome-shaped main body) and an outer flange  182 , which may be configured to couple to one of the flanges  110  of the shell  106  of the heat exchanger  100 . In an installed configuration, an inner volume  184  of the second water box  104 , which is generally defined by the main body  180 , receives the conditioning fluid  120  from the first subset  144  of tubes  108 , and the main body  180  directs the conditioning fluid  120  to the second subset  146  of tubes  108 . The main body  180  includes an inner surface  186  to which the fluid mixing manifold  128  is coupled (e.g., secured, mounted, affixed, etc.). 
     In the illustrated embodiment, the fluid mixing manifold  128  includes a mixing junction  188  and a plurality of sampling conduits  190  that extend from and are fluidly coupled to the mixing junction  188 . Each sampling conduit  190  is configured to receive a flow of the conditioning fluid  120  within the second water box  104  and direct the flow of conditioning fluid  120  to the mixing junction  188  where the different sampled flows of conditioning fluid  120  are mixed to generate mixed conditioning fluid  120 . More specifically, each sampling conduit  190  is configured to sample conditioning fluid  120  at a different location within the second water box  104 , such as at different locations relative to the height  166  of the heat exchanger  100 . For example, a first sampling conduit  192  is configured to receive a first flow of the conditioning fluid  120 , as indicated by arrow  194 , at a first location or height within the second water box  104 , a second sampling conduit  196  is configured to receive a second flow of the conditioning fluid  120 , as indicated by arrow  198 , at a second location or height within the second water box  104 , and a third sampling conduit  200  is configured to receive a third flow of the conditioning fluid  120 , as indicated by arrow  202 , at a third location or height within the second water box  104 . The first, second, and third flows of conditioning fluid  120  mix within the mixing junction  188  to form the mixed conditioning fluid  120 , and the mixed conditioning fluid  120  may be discharged from the fluid mixing manifold  188  via a discharge port  204  of the fluid mixing manifold  128 , as indicated by arrow  206 , that extends from and is fluidly coupled to the mixing junction  188 . 
     Each sampling conduit  190  includes a respective inlet port  208  generally facing a first direction  210  (e.g., first lateral direction, first side of the second water box  104 ). The inlet ports  208  facing the first direction  210  also face a portion (e.g., a portion of the inner volume  184 ) of the second water box  104  that is generally aligned (e.g., relative to a longitudinal axis or length of the heat exchanger  100 ) with the first pass  140  and the first subset  144  of tubes  108 . Thus, each sampling conduit  190  is arranged to effectively receive conditioning fluid  120  entering the second water box  104  from the first subset  144  of tubes  108  within the heat exchanger  100 . The discharge port  204 , on the other hand, includes an outlet  212  generally facing a second direction  214  (e.g., second lateral direction, second side of the second water box  104 ) opposite the first direction  210 . The discharge port  212  facing the second direction  214  faces a portion (e.g., a portion of the inner volume  184 ) of the second water box  104  that is generally aligned (e.g., relative to a longitudinal axis or length of the heat exchanger  100 ) with the second pass  142  and the second subset  146  of tubes  108 . Thus, the discharge port  204  effectively directs the mixed conditioning fluid  120  from the fluid mixing manifold  128  towards the second subset  146  of tubes  108  within the heat exchanger  100 . 
     The fluid mixing manifold  128  further includes a sensor port  216  extending from the mixing junction  188 . The sensor port  216  is fluidly coupled to the mixing junction  188  and extends through the main body  180  of the second water box  104  to an outer surface  218  of the main body  180 . Accordingly, a sensor (e.g., a temperature sensor) may be inserted into the sensor port  216 , and therefore into the mixing junction  188 , from an exterior of the second water box  104 . In this way, a sensor may be used to detect a temperature or other property of the mixed conditioning fluid  120  within the mixing junction  188 . 
     In the illustrated embodiment, the fluid mixing manifold  128  includes generally tubular structures (e.g., sampling conduits  190 ) coupled to the second water box  104 . In some embodiments, components of the fluid mixing manifold  128  may be formed from a metallic material, such as carbon steel, a polymeric material, or other suitable material. The mixing junction  188  is coupled to the second water box  104  via the sensor port  216 , and the sampling conduits  190  are coupled to the second water box  104  via support extensions  220 . Thus, the fluid mixing manifold  128  is offset from the inner surface  186  of the second water box  104 . However, other embodiments of the fluid mixing manifold  128  may have other configurations. For example, the fluid mixing manifold  128  may have components directly fixed to the inner surface  186  of the main body  180  to form conduits or channels between the components and the inner surface  186  that are configured to receive flows of the conditioning fluid  120 . In other embodiments, the fluid mixing manifold  128  may be disposed external to the inner volume  184  of the second water box  104  and may have conduits extending through the main body  180  to fluidly couple with the inner volume  184  and receive and/or discharge samples or flows of the conditioning fluid  120  at various locations within the second water box  104 . In any case, the fluid mixing manifold  128  is configured to sample different portions or flows of the conditioning fluid  120  within the second water box  104  (e.g., from various locations along the height  166 ) and generate mixed conditioning fluid  120 , the temperature of which may be measured to determine and/or approximate an average temperature of the conditioning fluid  120  within the second water box  104 . Further, embodiments of the fluid mixing manifold  128  may reduce a pressure drop of the conditioning fluid  120  within the second water box  104  compared to traditional components configured to mix the conditioning fluid  120  within water boxes, such as baffles disposed therein. Indeed, as shown in the illustrated embodiment of  FIG.  8   , the fluid mixing manifold  128  occupies a relatively small amount of space within the inner volume  184 , which does not impose significant flow restrictions on conditioning fluid  120  within the second water box  104  compared to traditional baffles and other mixing systems. 
       FIG.  9    is a schematic of an embodiment of a control system  240  configured to measure and/or approximate an average temperature of the conditioning fluid  120  and control operation of an HVAC&amp;R system (e.g., HVAC&amp;R system  10 , vapor compression system  14 , etc.) based on the determined average temperature. For example, the control system  240  may configured to determine and/or approximate an average temperature of the conditioning fluid  120  within the heat exchanger  100  (e.g., within the second water box  104 ) discussed above. The control system  240  may be configured to regulate operation of various components of a first refrigerant circuit  242  (e.g., first refrigerant circuit  82 ) and a second refrigerant circuit  244  (e.g., second refrigerant circuit  84 ) that are used in conjunction with the heat exchanger  100 . 
     The control system  240  includes a controller  246  having a memory  248  and processing circuitry  250 , such as a microprocessor. The memory  248  may include volatile memory, such as random-access memory (RAM), and/or non-volatile memory, such as read-only memory (ROM), optical drives, hard disc drives, solid-state drives, or any other tangible, non-transitory computer-readable medium that includes (e.g., stores) instructions executable by the processing circuitry  250  to operate the HVAC&amp;R system  10 . The processing circuitry  250  may include one or more application specific integrated circuits (ASICs), one or more field programmable gate arrays (FPGAs), one or more general purpose processors, or any combination thereof, configured to execute the instructions stored in the memory  248  to operate the HVAC&amp;R system  10 . 
     The controller  246  is configured to receive feedback from one or more sensors  252 . For example, one of the sensors  252  may be used with the fluid mixing manifold  128 . As discussed above, the sensor  252  may be a temperature sensor configured to measure a temperature of mixed conditioning fluid  120  (e.g., within the mixing junction  188  of the fluid mixing manifold  128 ). Based on the measured temperature of the mixed conditioning fluid  120 , the controller  246  may adjust operation of one or more components of the first refrigerant circuit  242  and/or the second refrigerant circuit  244  (e.g., any components of the first refrigerant circuit  82  and the second refrigerant circuit  84 ). In one embodiment, the controller  246  may adjust operation of the HVAC&amp;R system  10  to balance a cooling load of the HVAC&amp;R system  10  between the first refrigerant circuit  242  and the second refrigerant circuit  244 . As an example, one or more of the sensors  252  may be configured to detect a temperature of the conditioning fluid  120  entering the heat exchanger  100  (e.g., entering the first water box  102  and directed to the first subset  144  of tubes  108 ) and to detect a temperature of the conditioning fluid  120  exiting the heat exchanger  100  (e.g., exiting the first water box  102  after flowing through the heat exchanger  100 ). Based on the detected temperatures of the conditioning fluid  120  entering and exiting the heat exchanger  100  and the temperature of the mixed conditioning fluid  120  within the second water box  104 , the controller  246  may determine respective temperature differentials of the conditioning fluid across the first pass  140  and second pass  142  of the heat exchanger  100 . The calculated temperature differentials may then be used to adjust operation of components (e.g., compressors, expansion devices, etc.) of the first refrigerant circuit  242  and/or the second refrigerant circuit  244  in order to achieve a desired balance of a cooling load (e.g., cooling load  88 ) on the HVAC&amp;R system  10  having the heat exchanger  100 . The controller  246  may also adjust operation of first refrigerant circuit  242 , the second refrigerant circuit  244 , and/or other components of the HVAC&amp;R system  10  to load and/or unload the HVAC&amp;R system  10  in a desirable manner. 
     As discussed above, present embodiments are directed to a fluid mixing manifold configured to sample fluid, such as cooling or conditioning fluid, at different locations within a water box of a heat exchanger, such as a heat exchanger incorporated with multiple refrigerant circuits. The fluid mixing manifold mixes the sampled fluids to generate a mixed fluid. The temperature of the mixed fluid may be measured and may be used to control operation of a vapor compression system having the heat exchanger, such as to balance a load shared by the multiple refrigerant circuits. The configuration of the fluid mixing manifold enables more accurate temperature measurements of the fluid for use in controlling operation of the vapor compression system and also enables a reduction in pressure drop of the fluid within the water box compared to traditional systems that are configured to generate a mixed fluid within the water box. 
     While only certain features and embodiments of the disclosure have been illustrated and described, many modifications and changes may occur to those skilled in the art, such as variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, including temperatures and pressures, mounting arrangements, use of materials, colors, orientations, and so forth without materially departing from the novel teachings and advantages of the subject matter recited in the claims. The order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the disclosure. Furthermore, in an effort to provide a concise description of the exemplary embodiments, all features of an actual implementation may not have been described, such as those unrelated to the presently contemplated best mode of carrying out the disclosure, or those unrelated to enabling the claimed disclosure. It should be noted that in the development of any such actual implementation, as in any engineering or design project, numerous implementation specific decisions may be made. Such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure, without undue experimentation. 
     The techniques presented and claimed herein are referenced and applied to material objects and concrete examples of a practical nature that demonstrably improve the present technical field and, as such, are not abstract, intangible or purely theoretical. Further, if any claims appended to the end of this specification contain one or more elements designated as “means for [perform]ing [a function] . . . ” or “step for [perform]ing [a function] . . . ”, it is intended that such elements are to be interpreted under 35 U.S.C. 112(f). However, for any claims containing elements designated in any other manner, it is intended that such elements are not to be interpreted under 35 U.S.C. 112(f).