Patent Publication Number: US-2023160613-A1

Title: Multiple expansion device evaporators and hvac systems

Description:
CROSS-REFERENCED TO RELATED APPLICATION 
     This application claims priority to U.S. Provisional Application No. 63/281,955, which was filed on Nov. 22, 2021, and U.S. Provisional Application No. 63/289,386, which was filed on Dec. 14, 2021. 
    
    
     BACKGROUND 
     Vehicles may have a HVAC (Heating, ventilation, and air conditioning) climate control system located within an instrument panel which provides conditioned air, such as by heating or cooling or dehumidifying, through various outlets to occupants in the vehicle cabin. 
     SUMMARY 
     An HVAC system according to an example of this disclosure includes an evaporator, a condenser, a compressor. A first refrigerant path flows through a first expansion valve, first evaporator inlet, within the evaporator, and out of the evaporator through a first evaporator outlet. A second refrigerant path flows through a second expansion valve, a second evaporator inlet, within the evaporator, and out of the evaporator through a second evaporator outlet. Refrigerant flows from the condenser to the first refrigerant path and the second refrigerant path, and from the first refrigerant path and the second refrigerant path to the compressor. 
     In a further example of the foregoing, a receiver drier is fluidly between, with respect to the flow of refrigerant, the condenser and the first and second expansion valves. 
     In a further example of any of the foregoing, the evaporator includes a first tube row, which includes a first plurality of evaporator tubes spaced apart from one another in a lengthwise direction and extending in a heightwise direction. A second tube row includes a second plurality of evaporator tubes spaced apart from one another in the lengthwise direction and extending in a heightwise direction. The first plurality of evaporator tubes are spaced from the second plurality of evaporator tubes in a widthwise direction. 
     In a further example of any of the foregoing, a first tank at a first end of the first tube row and the second tube row, and a second tank at a second end of the first tube row and the second tube row and opposite the first end. 
     In a further example of any of the foregoing, the first evaporator inlet and the second evaporator inlet are disposed at the second tank. 
     In a further example of any of the foregoing, the first evaporator outlet and the second evaporator outlet are disposed at the second tank. 
     In a further example of any of the foregoing, a fan is configured to move air in the widthwise direction across the evaporator. The second tube row is an air on tube row with respect to the airflow of the fan. 
     In a further example of any of the foregoing, the first tube row is an air off tube row with respect to the airflow of the fan. 
     In a further example of any of the foregoing, a plurality of partitions within the first and second tanks are configured to direct refrigerant flow within the evaporator and to keep the first refrigerant path and the second refrigerant path fluidly separate within the evaporator. 
     In a further example of any of the foregoing, the first refrigerant path is configured flows to enter one of the first and second tank through the first evaporator inlet, through a first subsection of the first plurality of evaporator tubes in the heightwise direction to the other of the first and second tank, through a first subsection of the second plurality of evaporator tubes in an opposite heightwise direction back to the one of the first and second tank, and exits the evaporator through the first evaporator outlet on the of the first and second tank. 
     In a further example of any of the foregoing, the second refrigerant path is flows to enter the of the first and second tank through the second evaporator inlet, through a second subsection of the first plurality of evaporator tubes in the heightwise direction to other of the first and second tank, then through a second subsection of the second plurality of evaporator tubes in the opposite heightwise direction back to the one of the first and second tank, and exits the evaporator through the second evaporator outlet on one of the first and second tank. 
     In a further example of any of the foregoing, a plurality of partitions within the first and second tanks direct refrigerant flow within the evaporator and keep the first refrigerant path and the second refrigerant path fluidly separate within the evaporator. 
     In a further example of any of the foregoing, the first tube row, the second tube row, the first tank, and the second tank, are brazed together. 
     In a further example of any of the foregoing, the first refrigerant path and the second refrigerant path have a mirrored relationship within the evaporator relative to a plane, which extends widthwise and heightwise through central portions of the first and second tube row. 
     In a further example of any of the foregoing, the opposite heightwise direction is a downward direction. 
     In a further example of any of the foregoing, the opposite heightwise direction is an upward direction. 
     In a further example of any of the foregoing, at least one of the first and second expansion valves are in communication with a controller to vary refrigerant flow through the at least one of the first and second expansion valves. 
     In a further example of any of the foregoing, the first tube row, the second tube row, the first tank, and the second tank, are brazed together. 
     In a further example of any of the foregoing, a plurality of fins extend in the lengthwise direction between adjacent ones of the first and second plurality of evaporator tubes and in the widthwise direction from the second tube row to the first tube row. 
     In a further example of any of the foregoing, the first evaporator inlet and the second evaporator inlet are disposed at the second tank, and the first evaporator outlet and the second evaporator outlet are disposed at the second tank. 
     These and other features may be best understood from the following specification and drawings, the following of which is a brief description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    schematically illustrates an example HVAC system in a vehicle. 
         FIG.  2    schematically illustrates the example HVAC system of  FIG.  1   . 
         FIG.  3    schematically illustrates an example evaporator of the example HVAC system of  FIGS.  1  and  2   . 
         FIG.  4    schematically illustrates the example evaporator of  FIG.  3   . 
         FIG.  5    illustrates a cross-sectional view of the example evaporator of  FIGS.  3 - 4   . 
         FIG.  6    illustrates another cross-sectional view of the example evaporator of  FIGS.  3 - 5   . 
         FIG.  7    illustrates another cross-sectional view of the example evaporator of  FIGS.  3 - 6   . 
         FIG.  8    schematically illustrates a section of another example HVAC system. 
         FIG.  9 A  schematically illustrates a section of another example HVAC system. 
         FIG.  9 B  schematically illustrates a section of another example HVAC system. 
         FIG.  10    schematically illustrates a section of another example HVAC system. 
         FIG.  11    shows a sectional view of an example evaporator. 
     
    
    
     DETAILED DESCRIPTION 
     This disclosure is related to HVAC systems, and more particularly to an evaporator having two or more refrigerant paths. 
       FIG.  1    illustrates a vehicle  10  including an example HVAC system  20  for providing conditioned air to a vehicle cabin  12 . In some examples, the vehicle  10  may include any of automobiles, heavy trucks, agricultural vehicles, or commercial vehicles. 
       FIG.  2    schematically illustrates the example HVAC system  20  of  FIG.  1   . The example HVAC system  20  includes a compressor  22 , condenser  24 , evaporator  30  and two expansion valves  38 ,  42 . In some examples, as shown, the HVAC system  20  includes a receiver drier  28 . Refrigerant enters the compressor  22  as low-pressure, low-temperature gas, and leaves the compressor  22  as a high-pressure, high-temperature gas, flowing to the condenser  24 . The condenser  24  is supplied with high-temperature high-pressure, vaporized refrigerant coming off the compressor  22  and removes heat from the hot refrigerant vapor until it condenses into a saturated liquid state. The expansion devices  38 ,  42  each create a drop in pressure after the refrigerant leaves the condenser  24  and before refrigerant enters the evaporator  30 . 
     As shown, the refrigerant splits into a first path  62  flowing across the expansion valve  38  and entering the evaporator  30  at a first evaporator inlet  48  and a second, separate path  64  flowing across the expansion valve  42  and entering the evaporator  30  at a second evaporator inlet  50 . The example expansion valves  38 ,  42  as shown are electronic expansion valves; however, in some examples, other valves, including mechanical expansion valves, may be utilized. Refrigerant enters the evaporator  30  as a low temperature liquid at low pressure, and a fan  52  forces air across the evaporator  30 , cooling the air by absorbing the heat from the space in question into the refrigerant. The refrigerant entering the evaporator  30  through the evaporator inlet  48  exits through an evaporator outlet  54  and flows back to the compressor  22  through a first exit path  56 , and the refrigerant entering the evaporator  30  through the evaporator inlet  50  exits through an evaporator outlet  58  and flows back to the compressor  22  through a second exit path  60 . In some examples, as shown, a receiver drier  28  is fluidly between, with respect to the flow of refrigerant, the condenser  24  and evaporator  30 , to clean and remove moisture from the system. 
     The system  20  therefore includes a first refrigerant path  62  including flow through the first expansion valve  38 , the first evaporator inlet  48 , within the evaporator  30 , and exiting the evaporator  30  through the first evaporator outlet  54 . The system further includes a second refrigerant path  64  including flow through a second expansion valve  42 , a second evaporator inlet  50 , within the evaporator  30 , and exiting the evaporator  30  through a second evaporator outlet  58 . Refrigerant flows from the condenser  24  to the first refrigerant path  62  and the second refrigerant path  64 , and from the first refrigerant path  62  and the second refrigerant path  64  to the compressor  22 . In some examples, the paths  62  and  64 , via their respective exit paths  56  and  60 , connect to the compressor  22  at different stages of compression from one another. In some examples, the paths  62  and  64 , via their respective exit paths  56  and  60 , connect to the compressor  22  at the same stage of compression. 
     One or both of the first and second expansion valves  38 ,  42  may be selectively controllable to vary refrigerant flow therethrough. In some examples, as shown, one or both of the first and second expansion valves  38 ,  42  may be in communication with one or more controllers  65  to control the flow of refrigerant therethrough. The one or more controllers  65 , in some examples, may include one or more computing devices, each having one or more of a computer processor, memory, storage means, network device and input and/or output devices and/or interfaces. The memory may, for example, include UVPROM, EEPROM, FLASH, RAM, ROM, DVD, CD, a hard drive, or other computer readable medium which may store data and/or the algorithms corresponding to the various functions of this disclosure. Although one controller  65  is schematically illustrated for discussion purposes, multiple controllers, including a controller at each expansion valve  38 ,  42 , which may be separate from or integrated with the expansion valves  38 ,  42 , may be utilized in some examples. Those skilled in the art who have the benefit of this description will realize that combination of hardware, software or firmware will best suit their particular needs. In some examples, flow through each expansion valve  38 ,  42  can be independently varied to achieve desired temperatures, pressures, and/or efficiency within the system. 
     In some examples, independent control may allow for closing or adjusting one expansion valve  38 ,  42  to prevent or reduce flow on one side of the evaporator. This would allow the pumping power of the compressor to be less overall with half the evaporator being utilized. Half mass flow of the refrigerant would be pumped through half of the evaporator. This condition may be for dehumidifying and or cooling air for only the driver side of the vehicle while not dehumidifying or cooling the passenger side, as an example. This would allow for reduction in compressor power when the passenger is not present. Further, independent control may allow for increase in the heat exchange from air to refrigerant within the same package envelope, as well as improvement of the temperature uniformity of the air exiting the evaporator. 
     Refrigerant properties in the saturation range are such that at a given pressure, there is a single associated refrigerant temperature, such that, as the pressure increases within the saturation zone, the temperature also increases. More heat is absorbed from the air as the refrigerant temperature lowers. At the refrigerant exit of the evaporator, the pressure is set by system conditions, including compressor RPM, condenser heat exchange, refrigerant charge amount, condenser subcool, and evaporator superheat. At the refrigerant inlet of the evaporator, the pressure equals the exit pressure plus the refrigerant pressure drop within the evaporator. By reducing the refrigerant pressure drop within the evaporator, the inlet pressure drop will be less, if all other conditions are being held constant. Since pressure determines the temperature when the refrigerant is saturated, the temperature of the refrigerant will also be lower at the refrigerant inlet. The lower refrigerant temperature will increase the temperature differential between the heat exchange media and increase the heat transfer. Increasing the temperature differential increases heat exchange rates in both conduction and convection. This in turn results in more heat exchange in the heat exchanger. 
     Although  FIG.  2    is shown as an example HVAC system configuration, the evaporators disclosed herein could be utilized in other configurations in some examples. 
       FIG.  3    schematically illustrates the example evaporator  30  including a first tube row  32  and a second tube row  34  spaced widthwise w from the first tube row  32 . Each tube row  32 ,  34  includes a plurality of evaporator tubes  33  positioned adjacent one another in a lengthwise  1  direction and extending in a heightwise h direction. A plurality of fins  35  spaced apart in a heightwise h direction may extend lengthwise between adjacent tubes  33  and widthwise across both the first tube row  32  and the second tube row  34 , as shown in  FIG.  11   . Referring back to  FIG.  3   , the evaporator  30  includes a first tank  66  at a first end  68  of the first tube row  32  and the second tube row  34 , and a second tank  70  at a second end  72  of the first tube row  32  and the second tube row  34  and opposite the first end  68  in the heightwise direction. The first tank  66  provides internal fluid paths and is in fluid communication with the evaporator tubes  33  of each of the first tube row  32  and a second tube row  34 . The second tank  70  provides internal fluid paths and is in fluid communication with the evaporator tubes  33  of each of the first tube row  32  and a second tube row  34 . 
     In the example evaporator  30 , the first evaporator inlet  48  and the first evaporator outlet  54  are disposed at a first lengthwise tank end  74  of the second tank  70 . The second evaporator inlet  50  and the second evaporator outlet  58  are disposed at a second lengthwise tank end  76  of the second tank  70  opposite the tank from the first end  74 . 
     In the example evaporator  30 , the first tube row  32 , the second tube row  34 , the first tank  66 , and the second tank  70  are joined together as one evaporator  30 . In some examples, the example evaporator  30  the first tube row  32 , the second tube row  34 , the first tank  66 , and the second tank  70  are joined together by brazing. 
     In some examples, air flow across the evaporator  30  is substantially in the widthwise direction and perpendicular to the evaporator tubes  33 , such that one of the first and second tube rows  32 ,  34  is an “air on” tube row and the other of the first and second tube rows is an “air off” tube row. The “air on” tube row is upstream of the “air off” tube row with respect to the direction of fan airflow. As shown with respect to the example evaporator  30 , the fan  52  is positioned nearest the second tube row  34 , such that the second tube row  34  is the “air on” tube row, and the first tube row  32  is the “air off” tube row. 
       FIG.  4    schematically illustrates the refrigerant flow path through the example evaporator  30 . In the path  62 , refrigerant enters the second tank  70  through the first evaporator inlet  48 , flows through a subsection  78  (See  FIG.  5   ) of the evaporator tubes  33  of the first tube row  32  in a heightwise direction to the first tank  66 , then through a subsection  80  (See  FIG.  5   ) of the evaporator tubes  33  of the second tube row  34  in an opposite heightwise direction back to the second tank  70 , and exits the evaporator  30  through the first evaporator outlet  54  on the second tank  70 . In some examples, each subsection  78 ,  80 ,  82 ,  84  extends approximately half the length of the evaporator  30 . 
     As shown in  FIGS.  4  and  5   , in the path  64 , refrigerant may also enter the second tank  70  through the second evaporator inlet  50 , flow through a subsection  82  (See  FIG.  5   ) of the evaporator tubes  33  of the first tube row  32  in a heightwise direction to the first tank  66 , then through a subsection  84  (see  FIG.  5   ) of the evaporator tubes  33  of the second tube row  34  in an opposite heightwise direction back to the second tank  70 , and exits the evaporator  30  through the second evaporator outlet  58  on the second tank  70 . 
     Referring to  FIG.  4   , in some examples, the refrigerant paths  62  and  64  within the evaporator  30  may be configured in a mirrored relationship to one another relative to a plane P 1  extending heightwise and widthwise through the center of the tube rows  32 ,  34  as shown. In some examples, as shown, in each refrigerant path  62 ,  64  refrigerant enters the evaporator  30  through the “air off” tube row and exits through the “air on” tube row. In such configurations, the temperature difference between air flowing across evaporator  30  and the refrigerant throughout the flow paths  62 ,  64  is maximized such that the “air off” tube row will be a desirably low temperature. In this configuration, the refrigerant may be a superheated vapor when it is located on the “air on” side, making the temperature higher than when it was previously a saturated mixture of vapor and liquid at the “air off” side, resulting in air exiting the evaporator  30  at the lowest refrigerant temperature side. 
     As shown in  FIG.  6   , the tanks  66 ,  70  may include one or more partitions to direct refrigerant flow within the evaporator and keep the first refrigerant path  62  and the second refrigerant path  64  (reference  FIG.  2   ) fluidly separate within the evaporator  30 . As shown in  FIG.  6   , the first tank  66  includes a first tank subsection  86  in fluid communication with the subsection  78  of evaporator tubes  33  (See  FIG.  5   ) and a second tank subsection  88  in fluid communication with the subsection  82  of evaporator tubes  33  (See  FIG.  5   ), and a partition  90  extending widthwise and heightwise fluidly separates the first tank subsection  86  from the second tank subsection  88 . A partition  91  substantially aligned lengthwise with the partition  90  extends widthwise and heightwise and fluidly separates a third tank subsection  92  (in fluid communication with tube subsection  80 ) from the second tank subsection  93  (in fluid communication with tube subsection  84 ). In some examples, each subsection  86 ,  88 ,  92 ,  93  extends approximately half the length of the evaporator  30 . 
       FIG.  7    shows a cross section through the second tank  70 . A partition  94  extending lengthwise and heightwise and aligned widthwise between the first and second tube rows  32 ,  34  (see  FIG.  4   ) fluidly separates a first tube row side of the second tank  70  from a second tube row side of the second tank  70  in order to achieve the flow paths shown in  FIG.  4   . Partitions  95  and  96  are also provided and positioned similarly to partitions  90 ,  91  of the first tank  66  shown in  FIG.  6   . 
     Although an example refrigerant pass configuration is shown in  FIGS.  2 - 7   , pass configurations through each tube row could be varied to achieve desired performance 
       FIG.  8    illustrates another example evaporator  130  substantially similar to the example evaporator  30 , except that both refrigerant paths  162 ,  164  enter and exit the evaporator  130  through the tank  166  instead of the tank  170 . It should be understood that like reference numerals identify corresponding or similar elements throughout the several drawings. The evaporator  130  may be utilized in an HVAC system similar or identical to the system  20  shown in  FIG.  2    in some examples. In some examples, with respect to  FIG.  1   , the tanks  66 / 166  are upper tanks with respect to the normal orientation of the vehicle  10 , and the tanks  70 / 270  are lower tanks with respect to the normal orientation of the vehicle  10 . Similar to the configuration of the evaporator  30 , both refrigerant paths enter the example evaporator  130  on the “air off” side and exit the evaporator  130  on the “air on” side. 
     In the path  162 , refrigerant enters the first tank  166  through the first evaporator inlet  148 , flows through a subsection (the subsections may be configured the same or similar as in  FIG.  5    in some examples) of the evaporator tubes of first tube row  132  in a heightwise direction to the second tank  170 , then through a subsection of the evaporator tubes of the second tube row  134  in an opposite heightwise direction back to the first tank  166 , and exits the evaporator  130  through the first evaporator outlet  154  on the first tank  166 . The inlet  148  and outlet  166  are at the same lengthwise side of the tank  166  as one another. 
     In the path  164 , refrigerant may also enter the first tank  166  through the second evaporator inlet  150 , flow through a subsection of the evaporator tubes of the first tube row  32  in a heightwise direction to the second tank  170 , then through a subsection of the evaporator tubes of the second tube row  134  in an opposite heightwise direction back to the first tank  166 , and exits the evaporator  130  through the second evaporator outlet  158  on the first tank  166 . The inlet  150  and outlet  158  are at the same lengthwise side of the tank  166  as one another. 
     In this example, the refrigerant in each path  162 ,  164  flows in the upward heightwise direction through the second tube row  134 , with respect to the normal orientation of the vehicle  10 , as it nears the outlets  154 / 158 . Further, the refrigerant flows in the downward heightwise direction through the tube row  132  with respect to the normal orientation of the vehicle  10 . When in the tube row  132 , the refrigerant is in a liquid state, such that gravity aids the refrigerant&#39;s downward flow path, and, in the second tube row  134 , the refrigerant is becoming more gaseous such that gravity has a minimal effect on the refrigerant&#39;s upward flow path. That is, gravity provides buoyancy to the vapor, helping separate liquid from vapor, and preventing liquid from exiting the evaporator. 
       FIG.  9 A  illustrates another example refrigerant flow path through another example evaporator  230  in a section of an example HVAC system  220 . A first path  262  flows through the expansion valve  238 , enters the evaporator  230  through the second tank  270 , flows in a heightwise direction through the first rube row  232  to the first tank  266 , in an opposite heightwise direction back through the first tube row  232  (in some examples, through a different subsection of the first tube row  232 ) to the second tank  270  and exits the evaporator  230  from the second tank  270  at a tank end opposite lengthwise from the tank end at which it entered the second tank  270 . A second path  264  flows through the expansion valve  242 , enters the evaporator  230  through the second tank  270 , flows in a heightwise direction through the second rube row  234  to the first tank  266 , back in an opposite heightwise direction through the second tube row  234  (in some examples, through a different subsection of the second tube row  234 ) to the second tank  270 , and exits the evaporator  230  from the second tank  270  at a tank end opposite lengthwise from the tank end at which it entered the second tank  270 . In some examples, as shown, the paths  262 ,  264  enter and exit the tank  270  at different tank ends from one another. In some examples, this arrangement creates a relatively uniform temperature within the evaporator. In some examples, as shown, the paths  262  and  264  connect to the compressor  222  at different stages of compression. In some examples, as shown schematically, the path  262  may connect to the compressor at an inlet  299 A and the path  264  may connect to the compressor  222  at a mid-cycle compression inlet  299 B downstream on the inlet  299 A with respect to the refrigerant path. In these examples, the expansion valves  238 ,  242  could be adjusted to vary the flow such that more refrigerant flow is allowed through the “air off” tube row  232  than the “air on” tube row  234 . In some examples, more flow on the air off slab allows for better temperature uniformity, such as by providing a flooded core when refrigerant flows through the core as saturated liquid/vapor and never reaches a superheated state which maintains an equal temperature of the refrigerant at all locations in the core, leading to better temperature uniformity (assuming minimal pressure drop throughout the core because changing pressure changes refrigerant temperature). Further higher flow rate conditions may lead to better temperature uniformity. 
     In other examples, the paths  262  and  264  may connect to the compressor  222  at the same stage. In some examples, the other HVAC systems  20 / 120 / 320 / 420  disclosed herein could have similar compressor connections to those disclosed with this embodiment. 
     A pressure and temperature sensor  297  may be provided near the evaporator outlet  254  of the path  262  and in communication with the expansion valve  238  to communicate pressure and/or temperature parameters of the refrigeration near the evaporator outlet  254 . In some examples, this communication may be either through a controller or one or more other intermediaries or directly, as shown schematically. A pressure and temperature sensor  298  may be provided near the evaporator outlet  258  of the path  264  and in communication with the expansion valve  242  to communicate pressure and/or temperature parameters of the refrigeration near the evaporator outlet  258 , either through a controller or one or more other intermediaries or directly, as shown schematically. In some examples, the expansion valves  238 / 242  may be adjusted, such as to vary flow, in response to feedback from the respective sensors  297 / 298 . In some examples, these adjustments may be automatic, such as by one or more controllers. The other HVAC systems disclosed herein may include pressure and temperature sensors arranged similarly to those disclosed in this embodiment. 
       FIG.  9 B  schematically illustrates another example evaporator  430  in a section of an example HVAC system  420  and substantially identical to the evaporator  230  shown in  FIG.  9 A , except that mechanical expansion valves  438 ,  442  are utilized, such that the paths  262 ,  264  flow through their respective expansion valves  438 ,  442  both before entering the evaporator  430  and after exiting the evaporator  430 . In some examples, such as those using mechanical valves, pressure and temperature sensors at the evaporator outlets are therefore not utilized. 
       FIG.  10    schematically illustrates another example refrigerant flow path through another example evaporator  330  at a section of an example HVAC system  320 . A first path  362  flows through the expansion valve  338 , enters the evaporator  330  through the second tank  370 , flows in a heightwise direction through the first rube row  332  to the first tank  366 , and exits the evaporator  330  from the first tank  366 . A second path  364  flows through the expansion valve  342 , enters the evaporator  330  through the second tank  370 , flows in a heightwise direction through the second rube row  334  to the first tank  366 , and exits the evaporator from the first tank  366 . The first path  362  enters the tank  370  at a tank end opposite lengthwise from the tank end where the second path  364  enters the tank  370 . The first path  362  exits the tank  366  at a tank end opposite from the tank end where the second path  364  exits the tank  366 . As discussed above, various partitions may be arranged in the respective tanks to achieve the flow paths shown. 
     Although the different examples are illustrated as having specific components, the examples of this disclosure are not limited to those particular combinations. It is possible to use some of the components or features from any of the embodiments in combination with features or components from any of the other embodiments. 
     The foregoing description shall be interpreted as illustrative and not in any limiting sense. A worker of ordinary skill in the art would understand that certain modifications could come within the scope of this disclosure. For these reasons, the following claims should be studied to determine the true scope and content of this disclosure.