Abstract:
A system has a compressor ( 22, 412 ). A heat rejection heat exchanger ( 30 ) is coupled to the compressor to receive refrigerant compressed by the compressor. The system has a heat absorption heat exchanger ( 64 ). The system includes a separator ( 170 ) comprising a vessel having an interior. The separator has an inlet, a first outlet, and a second outlet. An inlet conduit may extend from the inlet and may have the conduit outlet positioned to discharge an inlet flow into the vessel interior to cause the inlet flow to hit a wall before passing to a liquid refrigerant accumulation in the vessel.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     Benefit is claimed of U.S. Patent Application Ser. No. 61/367,086, filed Jul. 23, 2010, and entitled “Ejector Cycle Refrigerant Separator”, the disclosure of which is incorporated by reference herein in its entirety as if set forth at length. 
    
    
     BACKGROUND 
     The present disclosure relates to refrigeration. More particularly, it relates to refrigerant separators. 
     Earlier proposals for ejector refrigeration systems are found in U.S. Pat. No. 1,836,318 and U.S. Pat. No. 3,277,660.  FIG. 1  shows one basic example of an ejector refrigeration system  20 . The system includes a compressor  22  having an inlet (suction port)  24  and an outlet (discharge port)  26 . The compressor and other system components are positioned along a refrigerant circuit or flowpath  27  and connected via various conduits (lines). A discharge line  28  extends from the outlet  26  to the inlet  32  of a heat exchanger (a heat rejection heat exchanger in a normal mode of system operation (e.g., a condenser or gas cooler))  30 . A line  36  extends from the outlet  34  of the heat rejection heat exchanger  30  to a primary inlet (liquid or supercritical or two-phase inlet)  40  of an ejector  38 . The ejector  38  also has a secondary inlet (saturated or superheated vapor or two-phase inlet)  42  and an outlet  44 . A line  46  extends from the ejector outlet  44  to an inlet  50  of a separator  48 . The separator has a liquid outlet  52  and a gas outlet  54 . A suction line  56  extends from the gas outlet  54  to the compressor suction port  24 . The lines  28 ,  36 ,  46 ,  56 , and components therebetween define a primary loop  60  of the refrigerant circuit  27 . A secondary loop  62  of the refrigerant circuit  27  includes a heat exchanger  64  (in a normal operational mode being a heat absorption heat exchanger (e.g., evaporator)). The evaporator  64  includes an inlet  66  and an outlet  68  along the secondary loop  62  and expansion device  70  is positioned in a line  72  which extends between the separator liquid outlet  52  and the evaporator inlet  66 . An ejector secondary inlet line  74  extends from the evaporator outlet  68  to the ejector secondary inlet  42 . 
     In the normal mode of operation, gaseous refrigerant is drawn by the compressor  22  through the suction line  56  and inlet  24  and compressed and discharged from the discharge port  26  into the discharge line  28 . In the heat rejection heat exchanger, the refrigerant loses/rejects heat to a heat transfer fluid (e.g., fan-forced air or water or other fluid). Cooled refrigerant exits the heat rejection heat exchanger via the outlet  34  and enters the ejector primary inlet  40  via the line  36 . 
     The exemplary ejector  38  ( FIG. 2 ) is formed as the combination of a motive (primary) nozzle  100  nested within an outer member  102 . The primary inlet  40  is the inlet to the motive nozzle  100 . The outlet  44  is the outlet of the outer member  102 . The primary refrigerant flow  103  enters the inlet  40  and then passes into a convergent section  104  of the motive nozzle  100 . It then passes through a throat section  106  and an expansion (divergent) section  108  through an outlet  110  of the motive nozzle  100 . The motive nozzle  100  accelerates the flow  103  and decreases the pressure of the flow. The secondary inlet  42  forms an inlet of the outer member  102 . The pressure reduction caused to the primary flow by the motive nozzle helps draw the secondary flow  112  into the outer member. The outer member includes a (mixer having a convergent) section  114  and an elongate throat or mixing section  116 . The outer member also has a divergent section or diffuser  118  downstream of the elongate throat or mixing section  116 . The motive nozzle outlet  110  is positioned within the secondary nozzle convergent section  114 . As the flow  103  exits the outlet  110 , it begins to mix with the flow  112  with further mixing occurring through the mixing section  116  which provides a mixing zone. In operation, the primary flow  103  may typically be supercritical upon entering the ejector and subcritical upon exiting the motive nozzle. The secondary flow  112  is gaseous (or a mixture of gas with a smaller amount of liquid) upon entering the secondary inlet port  42 . The resulting combined flow  120  is a liquid/vapor mixture and decelerates and recovers pressure in the diffuser  118  while remaining a mixture. Upon entering the separator, the flow  120  is separated back into the flows  103  and  112 . The flow  103  passes as a gas through the compressor suction line as discussed above. The flow  112  passes as a liquid to the expansion valve  70 . The flow  112  may be expanded by the valve  70  (e.g., to a low quality (two-phase with small amount of vapor)) and passed to the evaporator  64 . Within the evaporator  64 , the refrigerant absorbs heat from a heat transfer fluid (e.g., from a fan-forced air flow or water or other liquid) and is discharged from the outlet  68  to the line  74  as the aforementioned gas. 
     Use of an ejector serves to recover pressure/work. Work recovered from the expansion process is used to compress the gaseous refrigerant prior to entering the compressor. Accordingly, the pressure ratio of the compressor (and thus the power consumption) may be reduced for a given desired evaporator pressure. The quality of refrigerant entering the evaporator may also be reduced. Thus, the refrigeration effect per unit mass flow may be increased (relative to the non-ejector system). The distribution of fluid entering the evaporator is improved (thereby improving evaporator performance). Because the evaporator does not directly feed the compressor, the evaporator is not required to produce superheated refrigerant outflow. The use of an ejector cycle may thus allow reduction or elimination of the superheated zone of the evaporator. This may allow the evaporator to operate in a two-phase state which provides a higher heat transfer performance (e.g., facilitating reduction in the evaporator size for a given capability). 
     The exemplary ejector may be a fixed geometry ejector or may be a controllable ejector.  FIG. 2  shows controllability provided by a needle valve  130  having a needle  132  and an actuator  134 . The actuator  134  shifts a tip portion  136  of the needle into and out of the throat section  106  of the motive nozzle  100  to modulate flow through the motive nozzle and, in turn, the ejector overall. Exemplary actuators  134  are electric (e.g., solenoid or the like). The actuator  134  may be coupled to and controlled by a controller  140  which may receive user inputs from an input device  142  (e.g., switches, keyboard, or the like) and sensors (not shown). The controller  140  may be coupled to the actuator and other controllable system components (e.g., valves, the compressor motor, and the like) via control lines  144  (e.g., hardwired or wireless communication paths). The controller may include one or more: processors; memory (e.g., for storing program information for execution by the processor to perform the operational methods and for storing data used or generated by the program(s)); and hardware interface devices (e.g., ports) for interfacing with input/output devices and controllable system components. 
     Various modifications of such ejector systems have been proposed. One example in US20070028630 involves placing a second evaporator along the line  46 . US20040123624 discloses a system having two ejector/evaporator pairs. Another two-evaporator, single-ejector system is shown in US20080196446. 
     SUMMARY 
     One aspect of the disclosure involves a system having a compressor. A heat rejection heat exchanger is coupled to the compressor to receive refrigerant compressed by the compressor. The system has a heat absorption heat exchanger. The system includes a separator comprising a vessel having an interior. The separator has: an inlet; a first outlet; and a second outlet. An inlet conduit may extend from the inlet and may have the conduit outlet positioned to discharge an inlet flow into the vessel interior to cause the inlet flow to hit a wall before passing to a liquid refrigerant accumulation in the vessel. 
     In various implementations, an ejector may have: a primary inlet coupled to the heat rejection heat exchanger to receive refrigerant: a secondary inlet; and an outlet. The separator inlet may be coupled to an outlet of the ejector. An expansion device may be immediately upstream of the heat absorption heat exchanger. The refrigerant may comprise at least 50% carbon dioxide, by weight. The separator may also be used as a flash tank device for an economized cycle. 
     Other aspects of the disclosure involve methods for operating the system. 
     The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of a prior art ejector refrigeration system. 
         FIG. 2  is an axial sectional view of an ejector. 
         FIG. 3  is a schematic view of a first refrigeration system. 
         FIG. 4  is an enlarged view of a separator of the system of  FIG. 3 . 
         FIG. 5  is a partial, partially schematic, cutaway view of an alternate separator. 
         FIG. 6  is a partial, partially schematic, cutaway view of a second alternate separator. 
         FIG. 7  is a partial, partially schematic, cutaway view of a third alternate separator. 
         FIG. 8  is a partial, partially schematic, cutaway view of a fourth alternate separator. 
         FIG. 9  is a partial, partially schematic, cutaway view of a fifth alternate separator. 
         FIG. 10  is a partial, partially schematic, cutaway view of a sixth alternate separator. 
         FIG. 11  is a schematic view of a second refrigeration system. 
     
    
    
     Like reference numbers and designations in the various drawings indicate like elements. 
     DETAILED DESCRIPTION 
       FIG. 3  shows an ejector cycle vapor compression (refrigeration) system  160 . The system  160  may be made as a modification of the system  20  or of another system or as an original manufacture/configuration. In the exemplary embodiment, like components which may be preserved from the system  20  are shown with like reference numerals. Operation may be similar to that of the system  20  except as discussed below with the controller controlling operation responsive to inputs from various temperature sensors and pressure sensors. 
     The separator  48  of  FIG. 1  is replaced with a separator that may more resemble an existing accumulator (e.g., is made or designed as a modification of an existing accumulator). The modification may add an additional outlet to the existing/baseline accumulator to form a separator liquid outlet. It may be desirable to avoid high velocity impact of the inlet flow with the accumulation in the separator. Such impact might cause foaming which could provide undesirable introduction of vapor refrigerant into the accumulation and therefrom through the liquid outlet. As is discussed further below, means are provided for deflecting the inlet flow to reduce the velocity with which the inlet flow encounters the accumulation. 
     Nevertheless, it may be desirable to provide a controlled amount of mixed phase outlet flow (e.g., a slight amount of vapor discharged through the liquid outlet and/or a slight amount of liquid discharged through the vapor or gas outlet). Means for providing such mixed phase flow may also be provided if desired. For example, by feeding a two-phase mixture into the compressor, the discharge temperature of the compressor can be reduced if desired (thus extending the compressor system operating range). Feeding a suction line heat exchanger (SLHX) and/or compressor with small amount liquid are also expected to improve both SLHX and compressor efficiency. Exemplary refrigerant is delivered as 85-99% quality (vapor mass flow percentage), more narrowly, 90-98% or 94-98%. Also by feeding a two-phase mixture to the expansion valve upstream of the evaporator one can precisely control the system capacity, which can prevent unnecessary system shutdowns (comfort and improved reliability) and improve temperature control. This may help improve refrigerant distribution in the evaporator manifold and further improve evaporator performance Exemplary refrigerant is delivered as 1-10% quality (vapor mass flow percentage), more narrowly 2-6%. 
     The exemplary separator  170  ( FIG. 4 ) may be based upon a conventional accumulator. The modified accumulator has a tank or vessel  172 , an inlet  174 , a first outlet  176  for discharging the vapor (or high quality) refrigerant  177 , and a second outlet  178  for discharging the liquid (or low quality) refrigerant  179 . The baseline accumulator has an inlet conduit  180  which extends to a downstream end  182  which would otherwise form the outlet of the inlet conduit. The exemplary end  182  is within a headspace  194  which would be above the accumulation  200 . The baseline accumulator is modified by inserting an upper end  184  of a tube insert  185  into the inlet conduit (and securing via welding, clamping, or the like). The conduit  182  thus becomes a first member/portion of the resulting inlet conduit (assembly) while the insert  185  becomes the second member/portion. 
     A lower end  186  of the tube insert  185  is closed and sits on the bottom  187  of the vessel (e.g., for support so as to minimize stress on the joint with the inlet conduit  182 ). Along an intermediate portion (still above a surface of the accumulation  200 ) the tube insert  185  bears apertures (holes)  188 . The apertures  188  deflect the inlet flow  120  to reduce the velocity with which the inlet flow encounters the accumulation. For example, the apertures  188  may cause the inlet flow to deflect off the inner surface of the sidewall  189  of the vessel (e.g., flow down the sidewall to the accumulation). This deflection reduces foaming in the accumulation  200  and helps provide controlled balances of vapor and liquid in the flows  177  and  179 . 
     In one exemplary implementation, the inlet tube has an inner diameter (ID) of 15.9 mm which corresponds to a particular standard tube size. Other sizes may be used depending upon system requirements. 
     In the example, the holes  188  are grouped in two rows of five holes with each hole of one group diametrically opposite an associated hole of the other group. The exemplary holes are 0.25 inch (6.35 mm) in diameter. Other patterns of holes may be provided. For example, the patterns may be provided to create specific flow patterns, to accommodate other internal components, or the like. Similarly, hole orientation may be varied off radial or off horizontal. For example, angling of the holes upward at angles of up to 45° off horizontal/radial may allow the flows along the sidewall to use more of the sidewall. More broadly, an exemplary tube size for the inlet conduit or an insert therein is one eighth of an inch to two inches (3.2 mm-50.8 mm). Similarly, an exemplary range of hole sizes (especially for drilled holes) is 0.8 mm-20 mm in diameter depending upon the desired flow rate, conduit size, etc. Non-circular holes may have similar exemplary cross-sectional areas. An exemplary ratio of total hole area to local tube internal cross-sectional area is 0.5-20, more narrowly 1-5 or 1-2. 
     The exemplary first outlet  176  is at the downstream end of a U-tube (or J-tube)  190 . The U-tube extends to a second end (gas inlet end)  192  open to the headspace  194  of the tank for drawing a flow  196  of gas from the headspace. A lower portion (trough or base)  198  of the U-tube is immersed in the liquid refrigerant accumulation  200  in a lower portion of the tank, below the headspace. To entrain the desired amount of liquid  202  into the gas flow to form the high quality flow  177 , one or more holes  204  may be formed along the U-tube, including in the lower portion  198 . The hole sizing and locations are configured to provide the desired quality of two phase mixture entering the SLHX and/or compressor. An exemplary hole size for a drilled hole is 0.01 inch-0.5 inch (0.25 mm-12.7 mm), more narrowly 0.2-0.3 inch (5.1-7.6 mm). Multiple holes may be used and may be placed to achieve desired results. 
     To provide the small amount of gas in the low quality flow  179 , one or more vapor line tubes  220  may extend from a portion  222  having one or more gas inlets (holes)  224  in the headspace. An exemplary portion  222  is a closed end upper portion. A second portion  226  (a lower portion) has one or more holes  228  within the liquid accumulation  200 . The sizes of the holes  228  and  224  are selected so that a flow  230  of gaseous refrigerant is drawn through the holes  224  and becomes entrained in a flow of liquid refrigerant  232  drawn through the holes  228  to provide the desired composition of the low quality flow  179 . Exemplary size for the holes  224  is up to two inches (50 mm) in diameter for drilled holes or equivalent area for others, more narrowly, 0.1-0.5 inches (2.5-13 mm) or 0.1-0.3 inches (2.5-7.6 mm). Exemplary size for the holes  228  is 0.1-2 inches in diameter for drilled holes or equivalent area for others, more narrowly f 0.2-1.0 inches (5-25 mm) or 0.25-0.75 inches (6.35-19.1 mm). The ratio of hole sizes ( 224  vapor to  228  liquid) is 0 to 0.9; more narrowly 0.1 to 0.5; more narrowly 0.1 to 0.3. 
       FIGS. 5-10  show alternate separators which may otherwise be similar to the separator of  FIG. 4 . In  FIG. 5 , the flow  120  is directed directly to the vessel sidewall (e.g., via an elbow  300 ) having a first end  302  attached to the inlet conduit  180  and a second end  304  (forming an outlet  306  of the resulting inlet conduit) in close facing proximity to the sidewall to discharge the flow directly against the sidewall. The elbow  300  may be of an appropriate existing fitting type compatible with the inlet conduit. 
       FIG. 6  shows a diverter  320  having a plate  322  (e.g., a round flat metallic plate) held spaced apart from the inlet conduit end  182  (e.g., via a metal or other shaft  324 ) mounted to a spider or other spacer  326  which is mounted to the inlet conduit (e.g., via welding, brazing, or the like). The annular gap  328  between the rim/outlet  182  of the conduit first portion and the plate  322  thus becomes the outlet of the resulting conduit assembly. The exemplary inlet flow is deflected laterally by the plate to impact the sidewall. 
       FIG. 7  shows an alternate diverter  340  which may be otherwise similar to the alternate diverter  320 . However, the plate is replaced by a conical or otherwise upwardly concave structure  342 . Similar to the diverter  320 , the annular space/gap  344  becomes the effective outlet of the conduit assembly. This configuration deflects the inlet flow back upward to impact higher along the sidewall and at a lower angle of incidence to yet further reduce possibilities of entraining vapor during the impact. 
       FIG. 8  shows a helical baffle  360  inserted within the inlet conduit  182  and mounted thereto (e.g., via welding, brazing, or the like). The baffle may slow the flow and encourage separation of the vapor and liquid as the inlet flow flows along the baffle. The baffle may also cause a lateral discharge of the inlet flow to impact the sidewall as in other embodiments. For example, the positioning of a lower end portion  362  of the baffle  360  may provide an effective opening  364  below the conduit end  182  of the conduit first portion. 
       FIG. 9  shows the downstream end  380  of the inlet conduit closed off relative to the baseline end  182 . Holes  382  may be positioned along the inlet conduit and may function in a similar fashion to the holes  188 . Alternatively, the holes may be formed along an insert with the end being above the vessel bottom and not supported thereby. 
       FIG. 10  replaces the holes  382  with the apertures  394  of a foraminate member  390  (e.g., a mesh or perforated sheet) secured across a large lateral aperture/opening  392 . An exemplary foraminate member has an open area percentage of 10-95%, more narrowly, 20-80% or 50-70%. An exemplary pore size (e.g., a diameter of a circular pore or a length/width of a square mesh pore) is 0.01 inch-0.5 inch (0.25 mm-12.7 mm), more narrowly, 1.27-3.81 mm. The air ratio of total opening size to tube cross-sectional area may be so much of that discussed for the embodiment of  FIG. 4 . 
     The separators may also be used as flash tank economizers.  FIG. 11  shows an alternate refrigeration system  400  wherein the separator  170  is positioned between first and second expansion devices  402  and  404 . The first expansion device receives refrigerant from the gas cooler and expands the refrigerant. The inlet  174  receives the expanded refrigerant. The first outlet  176  is coupled via an economizer line  408  to the economizer port (intermediate port)  410  of the compressor  412  to deliver the high quality refrigerant. The second outlet  178  is coupled to the second expansion device to deliver the low quality refrigerant. The second expansion device expands the refrigerant for delivery to the evaporator and, thereafter, return to the compressor suction port. 
     The systems may be fabricated from conventional components using conventional techniques appropriate for the particular intended uses. 
     Although embodiments are described above in detail, such description is not intended for limiting the scope of the present disclosure. It will be understood that various modifications may be made without departing from the spirit and scope of the disclosure. For example, when implemented in the remanufacturing of an existing system or the reengineering of an existing system configuration, details of the existing configuration may influence or dictate details of any particular implementation. Accordingly, other embodiments are within the scope of the following claims.