Patent Publication Number: US-2023134928-A1

Title: Electronic actuator for working fluid flow control

Description:
FIELD 
     This disclosure is directed to electronic actuators for controlling flow of working fluid, particularly for use as expanders in fluid circuits in heating, ventilation, air conditioning, and refrigeration (HVACR) systems. 
     BACKGROUND 
     Expanders in fluid circuits allow the expansion of a working fluid as part of the refrigeration cycle. Typical expanders include many fixed devices such as orifice plates, which do not offer controllability of the orifice size or other aspects of their function. Fixed expanders thus are not able to adapt to different flow levels or flow rates. Orifice plates can be installed in piping in fluid circuits. 
     SUMMARY 
     This disclosure is directed to electronic actuators for controlling flow of working fluid, particularly for use as expanders in fluid circuits in heating, ventilation, air conditioning, and refrigeration (HVACR) systems. 
     By providing a controllable in-line valve using a plate with a relatively small thickness, width, or height to be disposed between ends of pipes, electronic actuators according to embodiments can provide simple installation or retrofitting options allowing the introduction of a controllable expander into a fluid circuit. Electronic actuators according to embodiments can be readily substituted in place of an orifice plate or other fixed expander. The use of these actuators over fixed expanders can in turn offer improvements to flow control and efficiency of the fluid circuit by allowing the expander to be controlled in response to various operating conditions. 
     In an embodiment, a fluid circuit includes a compressor, a first heat exchanger, a second heat exchanger, and an expander located along a pipe extending from the first heat exchanger to the second heat exchanger. The expander includes an actuator configured to modify a proportion of opening of the expander. 
     In an embodiment, the expander includes a valve seat providing a first orifice, a valve stem configured to obstruct the first orifice when in a first position and to allow flow through the first orifice when the valve stem is in a second position and a plate surrounding the valve seat, the plate including a second orifice. The actuator is configured to move the valve stem such that the valve stem can be moved between the first position and the second position, the actuator and the valve stem each located entirely within the pipe. 
     In an embodiment, the expander includes a fixed plate including a first aperture and a first rotating plate including a second aperture, and the actuator is configured to rotate the first rotating plate such that alignment of the first aperture with the second aperture is adjustable. 
     In an embodiment, the expander further includes a second rotating plate, the second rotating plate including a third aperture, and wherein the actuator is further configured to rotate the second rotating plate such that alignment of the third aperture with the first aperture and the second aperture is adjustable. 
     In an embodiment, the pipe includes a first pipe section joined to a first side of the expander and a second pipe section joined to a second side of the expander, the second side of the expander opposite the first side of the expander. 
     In an embodiment, the fluid circuit further includes a power connection located on an outer surface of the expander, the outer surface of the expander being outside the pipe, wherein the power connection is configured to allow a supply of power to the actuator. 
     In an embodiment, the fluid circuit further includes a housing configured to direct fluid flow around the actuator, the housing being located entirely within the pipe. 
     In an embodiment, the fluid circuit is configured to circulate a low pressure working fluid. 
     In an embodiment, a center of the actuator is offset from a center of the plate. 
     In an embodiment, heating, ventilation, air conditioning, and refrigeration (HVACR) system comprising the fluid circuit as described above. 
     In an embodiment, a method of retrofitting an existing heating, ventilation, air conditioning, and refrigeration (HVACR) system, includes removing an existing expander from a fluid circuit of the HVACR system and installing a controllable expander into the fluid circuit of the HVACR system, the controllable expander including an actuator configured to modify a proportion of opening of the expander. 
     In an embodiment, the controllable expander further includes a valve seat providing a first orifice, a valve stem configured to obstruct the first orifice when in a first position and to allow flow through the first orifice when in a second position, and a plate surrounding the valve seat, the plate including a second orifice. The actuator is configured to move the valve stem such that the valve stem can be moved between the first position and the second position, wherein a perimeter of the plate extends outwards beyond a perimeter of the actuator. 
     In an embodiment, the expander includes a fixed plate including a first aperture and a first rotating plate including a second aperture. In this embodiment, the actuator is configured to rotate the first rotating plate such that alignment of the first aperture with the second aperture is adjustable. 
     In an embodiment, the existing expander is an orifice plate. 
     In an embodiment, installing the controllable expander includes connecting a first pipe segment to a first side of the plate and connecting a second pipe segment to a second side of the plate, the second side opposite the first, such that the actuator is contained within one of the first pipe segment or the second pipe segment. 
     In an embodiment, an expander for use in a fluid circuit includes a valve seat providing a first orifice, a valve stem configured to obstruct the first orifice when in a first position and to allow flow through the first orifice when in a second position, a plate surrounding the valve seat, the plate including a second orifice, and an actuator configured to move the valve stem such that the valve stem can be moved between the first position and the second position. A perimeter of the plate extends outwards beyond a perimeter of the actuator. 
     In an embodiment, the plate includes a first pipe connection point on a first side of the plate and a second pipe connection point on a second side of the plate, the second side opposite the first. 
     In an embodiment, the expander further includes a power connection located on an outer surface at a perimeter of the plate. 
     In an embodiment, the expander further includes a housing configured to direct fluid flow around the actuator, the housing being located within a cylinder defined by the perimeter of the plate. 
     In an embodiment, a center of the valve seat is offset from a center of the plate. 
    
    
     
       DRAWINGS 
         FIG.  1    shows a schematic of a fluid circuit according to an embodiment. 
         FIG.  2    shows a perspective view of an expander according to an embodiment. 
         FIG.  3    shows a sectional view of an expander according to an embodiment. 
         FIG.  4    shows a flowchart of a method for retrofitting a heating, ventilation, air conditioning, and refrigeration (HVACR) system. 
         FIG.  5    shows a perspective view of an expander according to an embodiment. 
         FIG.  6    shows a chiller according to an embodiment. 
         FIG.  7    shows a front view of an expander according to an embodiment. 
         FIG.  8    shows a side view of the expander of  FIG.  7   . 
     
    
    
     DETAILED DESCRIPTION 
     This disclosure is directed to electronic actuators for controlling flow of working fluid, particularly for use as expanders in fluid circuits in heating, ventilation, air conditioning, and refrigeration (HVACR) systems. 
       FIG.  1    shows a schematic of a fluid circuit according to an embodiment. Fluid circuit  100  includes compressor  102 , first heat exchanger  104 , first pipe section  106 , expander  108 , second pipe section  110 , and second heat exchanger  112 . 
     Fluid circuit  100  is configured to circulate a working fluid. The working fluid can be any suitable working fluid for use in a fluid circuit, such as for example a refrigerant. In an embodiment, the working fluid can be a low pressure working fluid. The low pressure working fluid can be a refrigerant capable of being used in a system where the working fluid is at a pressure less than atmospheric pressure during at least a portion of the refrigeration cycle. Non-limiting examples of low pressure working fluid include R11, R123, R514a and R1233zd(E), or the like. 
     Compressor  102  is a compressor configured to compress the working fluid that is circulated in fluid circuit  100 . Compressor  102  can be any suitable compressor, such as, as non-limiting examples, a screw compressor, a centrifugal compressor such as a multi-stage centrifugal compressor, a scroll compressor, or the like. Working fluid compressed by the compressor  102  then moves to first heat exchanger  104 , which serves as a condenser where the working fluid rejects heat. The rejection of heat can be to, for example, a source fluid, an ambient environment, or any other suitable acceptor of heat from the working fluid. The working fluid from first heat exchanger  104  then passes to expander  108 . The working fluid passes from first heat exchanger  104  to expander  108  by way of a flow path including first pipe section  106 . First pipe section  106  is a segment of pipe connected to expander  108  such that the expander  108  can receive working fluid. 
     Expander  108  is configured to expand the working fluid received by way of first pipe section  106 . The expander  108  can be a controllable expander configured to vary the orifice or orifices used in expansion of the working fluid. The expander  108  can be an in-line expander located within one or both of first pipe section  106  and second pipe section  110 . Non-limiting examples of expander  108  are described below and shown in  FIGS.  2 - 4   . After passing through expander  108 , working fluid passes through a fluid pathway including second pipe section  110  to second heat exchanger  112 . Second heat exchanger  112  can serve as an evaporator where the working fluid absorbs heat, thus cooling a process fluid such as for example, water, air, glycol, or the like being conditioned to provide cooling. 
     While fluid circuit  100  is shown as including compressor  102 , first heat exchanger  104 , expander  108 , and second heat exchanger  112 , it is understood that fluid circuits according to embodiments can include further additional components including flow reversers or other flow controls, additional heat exchanger, economizers, and other such suitable components for inclusion in fluid circuits. The working fluid can then pass from second heat exchanger  112  to compressor  102  to continue circulation through fluid circuit  100 . 
       FIG.  2    shows a perspective view of an expander according to an embodiment. Expander  200  includes a housing  202 , a valve stem  204 , a valve seat  206 , and a plate  208 . Plate  208  includes orifices  210 . Power connection  212  is provided on a side surface  214  of plate  208 . Plate  208  further includes fixation features  216 . Optionally, expander  200  can further include a pressure relief line  218 . 
     Expander  200  is a flow control configured to be used in a working fluid circuit to expand the working fluid. In an embodiment, the expander  200  can be included in a working fluid circuit between a first heat exchanger of the working fluid circuit and a second heat exchanger of the working fluid circuit, for example as described above and shown in  FIG.  1   . Expander  200  is configured to control a flow through the expander  200  such that the working fluid is expanded. Expander  200  can provide a flow, the flow including a flow component passing through the orifices  210  and a controllable component that can selectively be provided through the valve seat  206 . In an embodiment, expander  200  can be used to control flow of a low pressure working fluid. The low pressure working fluid can be a refrigerant capable of being used in a system where the working fluid is at a pressure less than atmospheric pressure during at least a portion of the refrigeration cycle. Non-limiting examples of low pressure working fluid include R11, R123, R514a and R1233zd(E). 
     Housing  202  can surround an actuator (not shown, visible in  FIG.  3   ) such that the housing  202  directs flow through a pipe into which expander  200  is installed around the actuator. Housing  202  can be shaped such that flow around it is less turbulent compared to flow over and around the actuator would be. Housing  202  can include tapered or curved portions to direct the flow around the actuator. Housing  202  can include a cavity configured to accommodate the actuator and at least part of valve stem  204 . Housing  202  can have a closed end facing towards a direction of flow in the pipe into which expander  200  is installed. Housing  200  can have an open end from which valve stem  204  can protrude. 
     Valve stem  204  is a valve stem connected to an actuator (not shown, described below and shown in  FIG.  3   ). The valve stem  204  is configured to be moved by the actuator between a first position where it interfaces with valve seat  206  to obstruct flow through the orifice  220  of the valve seat  206  and a second position where the orifice  220  of valve seat  206  is exposed. In an embodiment, the valve stem  204  has a major axis generally parallel to a flow of fluid through a pipe into which the expander  200  is installed. In an embodiment, the valve stem  204  is moved by the actuator in a direction generally perpendicular to a plane of the valve seat  206  and/or plate  208 . In an embodiment, the valve stem  204  is moved by the actuator in a direction generally parallel to the pipe into which the expander  200  is installed. In an embodiment, the major axis of the valve stem  204  is generally parallel to the direction of movement of the valve stem  204  provided by the actuator. 
     Valve seat  206  includes an orifice  220  configured to allow flow of fluid through said orifice  220 . Valve seat  206  is configured to receive valve stem  204 , such that valve stem  204  can obstruct flow of fluid through the orifice  220  included in valve seat  206  when valve stem  204  is in the first position. Valve seat  206  is surrounded by plate  208 . In an embodiment, valve seat  206  is centered with respect to the projection of plate  208 . The orifice  220  through valve seat  206  can selectively allow flow through the valve seat  206  based on the position of valve stem  204 , thus providing a controllable orifice in expander  200 . Control of orifice  220  can allow changes to the proportion of opening of the expander  200  by affecting whether and how much of orifice  220  can permit flow, in addition to the one or more orifices  210  provided in plate  208 . 
     Plate  208  extends outwards from the valve seat  206 . In an embodiment, plate  208  extends outwards to at least a diameter of a pipe into which expander  200  is to be installed. In an embodiment, plate  208  has a thickness selected such that the thickness is similar to or the same as an existing orifice plate used in the pipe into which expander  200  is to be installed. Plate  208  includes one or more orifices  210 . The one or more orifices  210  allow flow through plate  208 . Flow through the one or more orifices  210  can combine with the flow through the orifice  220  included in valve seat  206  that is controlled by the position of valve stem  204 . The one or more orifices  210  can provide a baseline orifice size for the expander  200 , which can be supplemented by a variable orifice provided by valve seat  206  and valve stem  204 . A thickness of plate  208  can be sufficient to accommodate power connection  212  on an outer surface of plate  208 , where the power connection  212  can be presented outside a pipe that expander  200  is installed into. 
     Power connection  212  can be provided on plate  208 . The position of power connection  212  on plate  208  can be located such that the power connection  212  is provided outside a pipe when expander  200  is installed into that pipe. In an embodiment, power connection  212  can be provided on a side surface  214  of the plate  208 , the side surface  214  being an outer surface of the plate  208  between opposing first and second sides of the plate  208 . In an embodiment, the side surface  214  can be at the outer perimeter of the plate  208 . Power connection  212  provides a connection for a power supply, which can in turn supply power received at the power connection  212  to the actuator located within housing  202 . 
     Fixation features  216  can be provided in or on plate  208 . Fixation features  216  can be any suitable mechanical feature allowing one or more pipes to be joined to plate  208 . In an embodiment, fixation features  216  are one or more holes configured to allow fasteners such as screws to be inserted through the plate  208 . In this embodiment, the fasteners can be used to secure one or more pipes to the first and/or second sides of the plate  208 . In an embodiment, when a pipe is secured to the plate  208  using the fixation features, the pipe can surround the housing  202 , actuator, valve stem  204 , and valve seat  206 . Flow through a pipe connected to fixation features  216  can pass through expander  200  by way of the one or more orifices  210  provided in the plate  208  and can further selectively be allowed to pass through the orifice  220  provided in valve seat  206 . 
       FIG.  3    shows a sectional view of an expander according to an embodiment. Expander  300  includes housing  302 , actuator  304 , valve stem  306 , valve seat  308 , and plate  310 . Expander  300  includes a power connection  312  and a power line  314 . Expander  300  can be installed into a pipe  320 . 
     Housing  302  is a housing configured to direct flow of fluid around the actuator  304 . Housing  302  is configured to accommodate at least a portion of actuator  304 , and optionally further accommodate at least a portion of valve stem  306 . Housing  302  can be closed at an end  316  facing a direction from which flow comes towards the expander  300 . The housing  302  can have an open end  318  allowing a portion of actuator  304  and/or valve stem  306  to protrude outwards. The open end  318  can be opposite the closed end  316 . 
     Actuator  304  is an actuator configured to move valve stem  306  along a direction of travel between at least a closed position and an open position. The direction of travel is such that valve stem  306  meets valve seat  308  when it is moved to the closed position. Then the valve stem  306  is in the closed position, flow through an orifice  324  provided in the valve seat  308  is obstructed. The direction of travel can be parallel or substantially parallel to a direction of fluid flow through the pipe  320  including expander  300 . In an embodiment, the direction of travel can be generally perpendicular to the plate  310 . The actuator  304  can be an electrically powered actuator, for example receiving power supplied to the power connection  312  by way of the power line  314 . The actuator  304  can be any suitable actuator for controlling the position of valve stem  306 . In an embodiment, the actuator  304  includes a stepper motor  326 . 
     Valve stem  306  is a valve stem connected to actuator  304  such that the valve stem  306  can be moved by the actuator  304  between a first position where it interfaces with valve seat  308  to obstruct flow through the orifice  324  of the valve seat  308  and a second position where an orifice  324  in valve seat  308  is exposed. In an embodiment, the valve stem  306  has a major axis generally parallel to a flow of fluid through a pipe  320  into which the expander  300  is installed. In an embodiment, the valve stem  306  is moved by the actuator  304  in a direction perpendicular to a plane of the valve seat  308  and/or plate  310 . In an embodiment, the valve stem  306  is moved by the actuator  304  in a direction generally parallel to the pipe  320  into which the expander  300  is installed. In an embodiment, the major axis of the valve stem  306  is generally parallel to the direction of movement of the valve stem  306  provided by the actuator  304 . 
     Valve seat  308  includes an orifice  324  configured to allow flow of fluid through said orifice  324 . Valve seat  308  is configured to receive valve stem  306 , such that valve stem  306  can obstruct flow of fluid through the orifice  324  included in valve seat  308  when valve stem  306  is in the first position. The orifice  324  through valve seat  308  can selectively allow flow through the valve seat  308  based on the position of valve stem  306 , thus providing a controllable orifice  324  in expander  300 . The extent to which valve seat  308  and orifice  324  permit flow can effectively change a proportion of opening of the expander  300  by increasing or decreasing the area through which fluid can pass through expander  300  at orifice  324  in addition to other openings in plate  310 . 
     Plate  310  extends outwards from the valve seat  308 . In an embodiment, plate  310  extends outwards to at least a diameter of a pipe  320  into which expander  300  is to be installed. In an embodiment, plate  310  has a thickness selected such that the thickness is similar to or the same as an existing orifice  324  plate used in the pipe  320  into which expander  300  is to be installed. The thickness (width or height) in an embodiment refers to the longitudinal direction of the pipe  320  or existing orifice  324  plate or expander, for example along the direction of working fluid flow. While not visible in the section taken in  FIG.  3   , it is understood that the plate  310  can include orifice  324   s  such as the orifice  324   s    210  described above and shown in  FIG.  2   . While not visible in the section taken in  FIG.  3   , it is understood that the plate  310  can include fixation features such as the orifice  324   s  fixation features  216  above and shown in  FIG.  2   . 
     Power connection  312  is provided on plate  310  such that it can be provided outside of the one or more pipes  320  to which expander  300  is connected. Power connection  312  is configured to allow connection to a power supply. In an embodiment, the power connection is provided on an outer surface of the plate  310 . Power line  314  extends from plate  310  in a position that can be inside at least one pipe to which expander  300  is connected. Power line  314  extends to housing  302  or actuator  304  such that the power line  314  can convey power received at power connection  312  to the actuator  304 . In an embodiment, power line  314  can further be configured to convey a control signal to actuator  304 . The control signal can direct the actuator  304  to move valve stem  306  to a particular position, for example to obstruct or permit flow through the orifice  324  included in valve seat  308 . One or more pressure taps  322  can be installed along the outer surface of the plate  310 . 
       FIG.  4    shows a flowchart of a method for retrofitting a heating, ventilation, air conditioning, and refrigeration (HVACR) system. Method  400  includes removing an existing expander from a fluid circuit of the HVACR system  402 . The method  400  also includes installing a controllable expander into the fluid circuit of the HVACR system  404 . Optionally, method  400  can include operating the HVACR system  406 , including expanding a working fluid by way of the controllable expander. Method  400  can be used to retrofit an HVACR system to add the functionality of the controllable expander, for example by replacing an existing fixed size expander with the controllable expander. In an embodiment, the HVACR system being retrofitted according to method  400  can be an HVACR system configured to circulate a low pressure working fluid. The low pressure working fluid can be a refrigerant capable of being used in a system where the working fluid is at a pressure less than atmospheric pressure during at least a portion of the refrigeration cycle. Non-limiting examples of low pressure working fluid include R11, R123, R514a, and R1233zd(E), and the like, and combinations thereof. 
     An existing expander is removed from a fluid circuit of the HVACR system at  402 . The existing expander can be any suitable expander, such as an orifice, an expansion valve, or the like. In an embodiment, the existing expander removed at  402  is a fixed size expander. In an embodiment, the existing expander removed at  402  is an orifice plate. The orifice plate can be installed into the HVACR system along a pipe connecting a first heat exchanger and a second heat exchanger. In an embodiment, the orifice plate can be removed by removing pipe segments from either side of the orifice plate. 
     A controllable expander can be installed into the HVACR system at  404 . The controllable expander can be a controllable expander such as expanders  200 ,  300 ,  400  shown in  FIGS.  2 - 4   . The controllable expander can be configured to be located within one or more pipes of the HVACR system extending from a first heat exchanger to a second heat exchanger. The controllable expander can be installed into the HVACR system by joining a first pipe section of the HVACR system to a first side of the controllable expander and joining a second pipe section of the HVACR system to a second side of the controllable expander. In an embodiment, a thickness of the plate is similar to or the same as a thickness of the expander removed at  402 , such that the controllable expander can be installed in the same location the existing expander was removed from with minimal or no modification to the pipes of the HVACR system. In an embodiment, installation of the controllable expander  404  can further include connecting a power source to a power connection provided on the controllable valve. 
     In an embodiment, the HVACR system can be operated when including the controllable expander at  406 . In operation, working fluid of the HVACR system can be expanded as it flows through the controllable expander. The controllable expander can be controlled to adjust flow suitable to the operation of the HVACR system by controlling a variable portion of flow by positioning the valve stem using the actuator. In an embodiment, an actuator of the controllable valve can be used to move the valve stem to obstruct flow or permit flow through the orifice provided in the valve seat to control the variable portion of the flow. There can also be fixed flow through one or more orifices provided on the plate that can provide a baseline flow when flow through the orifice in the valve seat is obstructed or supplementing the variable portion of the flow. The flow through the controllable expander can be controlled and varied throughout operation of the HVACR system. 
       FIG.  5    shows a perspective view of an expander according to an embodiment. Expander  500  includes housing  502  surrounding an actuator (not shown), valve stem  504 , valve seat  506 , plate  508 , and orifices  510  formed in the plate  508 . Plate  508  further includes power connection  512  formed on an outer surface  514  of plate  508 . 
     Expander  500  is a flow control configured to be used in a working fluid circuit to expand the working fluid. In an embodiment, the expander  500  can be included in a working fluid circuit between a first heat exchanger of the working fluid circuit and a second heat exchanger of the working fluid circuit, for example as described above and shown in  FIG.  1   . Expander  500  is configured to control a flow through the expander  500  such that the working fluid is expanded. Expander  500  can provide a flow including a component through the orifices  510  and a controllable component that can selectively be provided through the valve seat  506 . In an embodiment, expander  500  can be used to control flow of a low pressure working fluid. The low pressure working fluid can be a refrigerant capable of being used in a system where the working fluid is at a pressure less than atmospheric pressure during at least a portion of the refrigeration cycle. Non-limiting examples of low pressure working fluid include R11, R123, R514a, and R1233zd(E), and the like, and combinations thereof. 
     Housing  502  is a housing configured to direct fluid flow around an actuator (not shown). The actuator can be an actuator as discussed above and shown in  FIG.  3   . Housing  502  can be shaped such that flow around it is less turbulent compared to flow over and around the actuator would be. Housing  502  can include tapered or curved portions to direct the flow around the actuator. Housing  502  can include a cavity configured to accommodate the actuator and at least part of valve stem  504 . Housing  502  can have a closed end facing towards a direction of flow in the pipe into which expander  500  is installed. Housing  502  can have an open end from which valve stem  504  can protrude. 
     Valve stem  504  is a valve stem connected to the actuator. The valve stem  504  is configured to be moved by the actuator between a first position where it interfaces with valve seat  506  to obstruct flow through the orifice of the valve seat  506  and a second position where an orifice of valve seat  506  is exposed. In an embodiment, the valve stem  504  has a major axis generally parallel to a flow of fluid through a pipe into which the expander  500  is installed. In an embodiment, the valve stem  504  is moved by the actuator in a direction generally perpendicular to a plane of the valve seat  506  and/or plate  508 . In an embodiment, the valve stem  504  is moved by the actuator in a direction generally parallel to the pipe into which the expander  500  is installed. In an embodiment, the major axis of the valve stem  504  is generally parallel to the direction of movement of the valve stem  204  provided by the actuator. 
     Valve seat  506  includes an orifice configured to allow flow of fluid through said orifice. Valve seat  506  is configured to receive valve stem  504 , such that valve stem  504  can obstruct flow of fluid through the orifice included in valve seat  506  when valve stem  504  is in the first position. Valve seat  506  is surrounded by plate  508 . The orifice through valve seat  506  can selectively allow flow through the valve seat  506  based on the position of valve stem  504 , thus providing a controllable orifice in expander  500 . 
     Plate  508  surrounds the valve seat  506 . In an embodiment, plate  508  has a diameter at least equal to a diameter of a pipe into which expander  500  is to be installed. In an embodiment, plate  508  has a thickness selected such that the thickness is similar to or the same as an existing orifice plate used in the pipe into which expander  500  is to be installed. A thickness of plate  508  can be sufficient to accommodate power connection  512  on an outer surface  514  of plate  508  that can be presented outside a pipe that expander  500  is installed into. 
     Housing  502 , valve stem  504 , and valve seat  506  can be positioned offset from a center of plate  508  as shown in  FIG.  5   . Housing  502 , valve stem  504 , and valve seat  506  can be positioned such that a central axis of each or all of housing  502 , valve stem  506  and valve seat  506  is not collinear with a central axis of the plate  508 . 
     Orifices  510  are distributed on plate  508 , apart from valve seat  506 . Orifices  510  are openings through plate  508  each having a fixed size. Orifices  510  can provide a fixed flow of fluid through expander  500  that can optionally be supplemented by flow through valve seat  506  based on a position of valve stem  504 . In an embodiment, the orifices  510  can each be holes drilled or otherwise machined in the plate  508 . In an embodiment, one orifice  510  can be provided on plate  508 . In an embodiment, a plurality of orifices  510  can be provided on plate  508 . While orifices  510  are shown as circular in the embodiment shown in  FIG.  5   , it is understood that the orifices  510  can have any suitable shape or size based on the desired flow characteristics, manufacturability, and the like for expander  500 . 
     Plate  508  further includes power connection  512  provided on an outer surface  514  of plate  508 . Power connection  512  is a connection point for a power supply, which can in turn supply power received at the power connection  512  to the actuator located within housing  502 . Power connection  512  can be presented outside of the pipe that expander  500  is installed into when the expander  500  is installed into said pipe. 
       FIG.  6    shows a chiller according to an embodiment. Chiller  600  includes compressor  602 , condenser  604 , and evaporator  606 , fluidly connected to one another to form a fluid circuit. The connections of the fluid circuit of chiller  600  can be according to the schematic shown in  FIG.  1   . An expander such as expander  108  as described above and shown in  FIG.  1    can be included in the fluid connection between condenser  604  and evaporator  606 . The expander can be an expander  200 , expander  300 , expander  500 , or expander  700  as shown in  FIG.  2 ,  3   , or  5  and described above or as shown in  FIGS.  7  and  8    and described below. The compressor  602  can be, as a non-limiting example, a centrifugal compressor as shown in  FIG.  6   . Compressor  602  can be a single- or multi-stage centrifugal compressor. It is understood that any suitable compressor such as, for example, scroll or screw compressors can be used as the compressor  602 . 
       FIG.  7    shows a front view of an expander according to an embodiment. Expander  700  includes fixed plate  702  including first apertures  704 . Expander  700  further includes first rotating plate  706  including second apertures  708  and first rotating plate teeth  710 . Expander  700  also includes second rotating plate  712 , including third apertures  714  and second rotating plate teeth  716 . Expander  700  additionally includes drive gear  718 , with drive gear  718  including first drive teeth  720  and second drive teeth  722 . 
     Expander  700  is a variable-orifice expander configured to be installed into a fluid circuit such as fluid circuit  100  described above and shown in  FIG.  1   . In an embodiment, the expander  700  can be configured to replace an orifice plate used in an expander of a fluid circuit. 
     Fixed plate  702  is a plate configured to fill an entire fluid line into which it is installed. In an embodiment, fixed plate  702  can include an outer section including a plurality of fixation features, such as the fixation features  216  described above and shown in  FIG.  2   . In an embodiment, fixed plate  702  can have a thickness selected to correspond to a thickness of an orifice plate that is being replaced by the expander  700 . Fixed plate  702  includes one or more apertures  704 . The apertures  704  are openings extending through fixed plate  702 . The alignment of the first apertures  704  with the second apertures  708  and the third apertures  714  can define the existence and/or size of orifices allowing flow of fluid through the expander  700 . 
     First rotating plate  706  is a plate having a size smaller than fixed plate  702 . First rotating plate  706  includes second apertures  708 . Second apertures  708  are openings through the first rotating plate  706 . That can be placed in or out of alignment with first apertures  704  and third apertures  714 . The alignment of the first, second, and third apertures  704 ,  708 ,  714  can affect a size of orifices through the expander  700  based on the extent of the alignment. First rotating plate  706  can include first rotating plate teeth  710 , configured to engage with drive gear  718  such that a rotational position of the first rotating plate  706  can be controlled by an actuator, such as actuator  724  as shown in  FIG.  8    and described below. 
     Second rotating plate  712  is a plate having a smaller size than fixed plate  702 . The second rotating plate can further have a smaller size than first rotating plate  706 . In an embodiment, second rotating plate  712  can have an axis of rotation that is collinear with the axis of rotation of first rotating plate  706 . Second rotating plate  712  includes third apertures  714 , which are apertures through the second rotating plate  712  that can be placed in or out of alignment with first and second apertures  704 ,  708 . In an embodiment, the third apertures  714  have the same size and general shape as at least one of the first apertures  704  or the second apertures  708 . Second rotating plate  712  further includes second rotating plate teeth  716 . The second rotating plate teeth  716  are configured to interface with teeth on drive gear  718  such that second rotating plate  712  can be rotated with respect to fixed plate  702 . 
     Drive gear  718  is configured to control the rotational positions of first rotating plate  706  and second rotating plate  712  relative to the fixed plate  702 . Drive gear  718  includes first drive teeth  720  and second drive teeth  722 . First drive teeth  720  are configured to engage with the first rotating plate teeth  710  of first rotating plate  706 , such that first rotating plate  706  can be rotated relative to fixed plate  702 . Second drive teeth  722  are configured to engage second rotating plate teeth  716  such that second rotating plate  712  can be rotated relative to fixed plate  702 . The size and spacing of the first drive teeth  720  and the second drive teeth  722  can be selected such that the relative rotation of first and second rotating plates  706 ,  712  with respect to fixed plate  702  affects the alignment of first apertures  704  with second apertures  708  and third apertures  714  such that a size of one or more orifices allowing fluid flow through the expander  700  can be controlled by operation of an actuator, such as actuator  724  shown in  FIG.  8    and discussed below. The alignment of first apertures  704 , second apertures  708 , and third apertures  714  can adjust the proportion of opening of the expander, effectively changing the size of the opening permitting flow compared to the area covered by the expander. It is understood that the size, shape and number of each of the first apertures  704 , second apertures,  708 , and/or third apertures  714  can be any suitable configuration allowing the proportion of opening to be changed by rotation of one or more of first rotating plate  706  and/or second rotating plate  712  relative to the fixed plate  702 . While first rotating plate  706  and second rotating plate  712  are shown in the embodiment shown in  FIG.  7   , it is understood that a single rotating plate or any number of additional rotating plates could be provided to control the proportion of opening of expander  700  by way of rotation of the rotating plate or plates. 
       FIG.  8    shows a side view of the expander of  FIG.  7   . In the side view of  FIG.  8   , the fixed plate  702 , first rotating plate  706 , second rotating plate  712 , and drive gear  718  can be seen as discussed above and shown in  FIG.  7   . Additionally, actuator  724  can be seen on a side of fixed plate  702  opposite the first rotating plate  706 , second rotating plate  712 , and drive gear  718 . In an embodiment, the actuator  724  can be positioned such that it is on a downstream side of expander  700 . In an embodiment, actuator  724  is positioned away from the aperture defined by the fixed plate  702 , first rotating plate  706  and second rotating plate  712  such that it is substantially out of the flow path for fluid passing through expander  700 . Actuator  724  can be any suitable actuator for controlling the drive gear  718  to rotate and thus control the relative rotational positions of first rotating plate  706  and second rotating plate  712  with respect to fixed plate  702 , such that an effective size of the apertures provided by expander  700  can be controlled. In an embodiment, actuator  724  is an electric motor, such as a stepper motor. 
     Aspects: 
     It is understood that any of aspects 1-10 can be combined with any of 11-15 or 16-20. It is understood that aspects 11-15 can be combined with any of aspects 16-20. 
     Aspect 1. A fluid circuit comprising: 
     a compressor;
 
a first heat exchanger;
 
a second heat exchanger; and
 
an expander located along a pipe extending from the first heat exchanger to the second heat exchanger,
 
wherein the expander includes an actuator configured to modify a proportion of opening of the expander.
 
     Aspect 2. The fluid circuit according to aspect 1, wherein the expander further comprises: 
     a valve seat providing a first orifice; 
     a valve stem configured to obstruct the first orifice when in a first position and to allow flow through the first orifice when the valve stem is in a second position; 
     a plate surrounding the valve seat, the plate including a second orifice; and 
     wherein the actuator is configured to move the valve stem such that the valve stem can be moved between the first position and the second position, the actuator and the valve stem each located entirely within the pipe. 
     Aspect 3. The fluid circuit according to aspect 1, wherein the expander includes a fixed plate including a first aperture and a first rotating plate including a second aperture, and wherein the actuator is configured to rotate the first rotating plate such that alignment of the first aperture with the second aperture is adjustable. 
     Aspect 4. The fluid circuit according to aspect 3, wherein the expander further comprises a second rotating plate, the second rotating plate including a third aperture, and wherein the actuator is further configured to rotate the second rotating plate such that alignment of the third aperture with the first aperture and the second aperture is adjustable. 
     Aspect 5. The fluid circuit according to any of aspects 1-4, wherein the pipe includes a first pipe section joined to a first side of the expander and a second pipe section joined to a second side of the expander, the second side of the expander opposite the first side of the expander. 
     Aspect 6. The fluid circuit according to any of aspects 1-5, further comprising a power connection located on an outer surface of the expander, the outer surface of the expander being outside the pipe, wherein the power connection is configured to allow a supply of power to the actuator. 
     Aspect 7. The fluid circuit according to any of aspects 1-6, further comprising a housing configured to direct fluid flow around the actuator, the housing being located entirely within the pipe. 
     Aspect 8. The fluid circuit according to any of aspects 1-7, wherein the fluid circuit is configured to circulate a low pressure working fluid. 
     Aspect 9. The fluid circuit according to any of aspects 1-8, wherein a center of the actuator is offset from a center of the plate. 
     Aspect 10. A heating, ventilation, air conditioning, and refrigeration (HVACR) system comprising the fluid circuit according to any of aspects 1-9. 
     Aspect 11. A method of retrofitting an existing heating, ventilation, air conditioning, and refrigeration (HVACR) system, comprising: 
     removing an existing expander from a fluid circuit of the HVACR system; and 
     installing a controllable expander into the fluid circuit of the HVACR system, the controllable expander including an actuator configured to modify a proportion of opening of the expander. 
     Aspect 12. The method according to aspect 11, wherein the controllable expander further comprises: 
     a valve seat providing a first orifice;
 
a valve stem configured to obstruct the first orifice when in a first position and to allow flow through the first orifice when in a second position; and
 
a plate surrounding the valve seat, the plate including a second orifice;
 
wherein the actuator is configured to move the valve stem such that the valve stem can be moved between the first position and the second position, wherein a perimeter of the plate extends outwards beyond a perimeter of the actuator.
 
     Aspect 13. The method according to aspect 11, wherein the expander includes a fixed plate including a first aperture and a first rotating plate including a second aperture, and wherein the actuator is configured to rotate the first rotating plate such that alignment of the first aperture with the second aperture is adjustable. 
     Aspect 14. The method according to any of aspects 11-13, wherein the existing expander is an orifice plate. 
     Aspect 15. The method according to any of aspects 11-14, wherein installing the controllable expander includes connecting a first pipe segment to a first side of the plate and connecting a second pipe segment to a second side of the plate, the second side opposite the first, such that the actuator is contained within one of the first pipe segment or the second pipe segment. 
     Aspect 16. An expander for use in a fluid circuit, comprising: 
     a valve seat providing a first orifice;
 
a valve stem configured to obstruct the first orifice when in a first position and to allow flow through the first orifice when in a second position;
 
a plate surrounding the valve seat, the plate including a second orifice; and
 
an actuator configured to move the valve stem such that the valve stem can be moved between the first position and the second position, wherein a perimeter of the plate extends outwards beyond a perimeter of the actuator.
 
     Aspect 17. The expander according to aspect 16, wherein the plate includes a first pipe connection point on a first side of the plate and a second pipe connection point on a second side of the plate, the second side opposite the first. 
     Aspect 18. The expander according to any of aspects 16-17, further comprising a power connection located on an outer surface at a perimeter of the plate. 
     Aspect 19. The expander according to any of aspects 16-18, further comprising a housing configured to direct fluid flow around the actuator, the housing being located within a cylinder defined by the perimeter of the plate. 
     Aspect 20. The expander according to any of aspects 16-19, wherein a center of the valve seat is offset from a center of the plate. 
     The examples disclosed in this application are to be considered in all respects as illustrative and not limitative. The scope of the invention is indicated by the appended claims rather than by the foregoing description; and all changes which come within the meaning and range of equivalency of the claims are intended to be embraced therein.