Abstract:
A flow device for a refrigerant/compressor system is installed between the outlet of an evaporator and the suction port of a compressor. The device includes a floating element that helps inhibit liquid refrigerant from entering the compressor. Under certain conditions where liquid refrigerant discharges from the evaporator, the floating element floats in the discharged liquid. Upon doing so, the float rises to a generally closed position where the float obstructs a main fluid outlet that leads to the compressor. In the closed position, refrigerant can still pass through the flow device, but through a more restricted outlet. To prevent the float from undesirably rising under the impetus of refrigerant vapor flowing at high flow rates, the floating element itself includes a flow-restricting passageway, radial guides, and/or a streamlined shape. The float can be incorporated within a manifold of a multi-coil or multi-circuited heat exchanger.

Description:
FIELD OF THE INVENTION 
       [0001]    The subject invention generally pertains to refrigerant systems and more specifically to a way of inhibiting liquid refrigerant from entering the suction inlet of a compressor. 
       Background of Related Art 
       [0002]    Typical refrigerant systems include a compressor that compresses gaseous refrigerant received from an evaporator. Under certain conditions, such as during startup or transient operation, refrigerant might not fully vaporize in the evaporator, and thus the refrigerant might enter the compressor as a liquid, which can damage a compressor, particularly if the compressor is a positive displacement one. 
         [0003]    To inhibit liquid refrigerant from entering a compressor, U.S. Pat. No. 3,412,574 suggests using a float valve between the evaporator and the compressor. The proposed valve includes a ball that is free to float loosely within a housing. When the housing is flooded with liquid refrigerant, the ball floats to block off a primary refrigerant outlet of the valve. In the absence of liquid, the intent is for the ball to fall back down away from the outlet to allow gaseous refrigerant to pass more freely through the housing. 
         [0004]    If, however, the flow rate of the gaseous refrigerant is too great for the valve of the &#39;574 patent, the gaseous refrigerant might create a velocity pressure sufficient to blow the ball upward until the ball blocks the outlet, even without liquid refrigerant. When the ball closes the outlet under such conditions, the gaseous flow becomes restricted, which could perhaps reduce the velocity pressure to a point where the ball falls back down. This would reopen the outlet, and the gaseous flow might once again blow the ball back up to obstruct the flow. If such a cycle were to repeat, the valve might begin hammering between open and closed positions. 
         [0005]    For the valve of the &#39;574 patent, it is also conceivable that once gaseous refrigerant blows the ball up against the outlet, the static pressure differential applied vertically across the ball might be sufficient to hold the ball in place. This might starve the compressor of refrigerant because only a restricted amount of gaseous refrigerant would be flowing through the small bypass opening of the valve. 
         [0006]    Although these problems could be avoided by simply limiting the maximum flow rate of gaseous refrigerant through the valve, such a solution would also limit the cooling capacity of the refrigerant system over all. Consequently, there is a need for a better way of inhibiting liquid refrigerant from entering the suction inlet of a compressor. 
       SUMMARY OF THE INVENTION 
       [0007]    It is an object of the invention to provide a float valve with ample space around its floating element to minimize gaseous pressure differentials that might adversely blow the floating element upward to its closed position. 
         [0008]    Another object of some embodiments to provide a float with a restricted passageway that is vertically long and narrow to draw liquid refrigerant up from the bottom of a pool of liquid refrigerant. Thus, the passageway can effectively drain the liquid up from the bottom of the pool rather than releasing gaseous refrigerant from above the surface of the liquid pool. 
         [0009]    Another object of some embodiments is to provide a float with guides that help maintain the float radially centered within a tubular housing. 
         [0010]    Another object of some embodiments is to provide a float with guides that help maintain the float&#39;s proper orientation within a tubular housing. 
         [0011]    Another object of some embodiments is to provide a floating element with a flow-restricting passageway therein for throttling the flow of refrigerant in the presence of liquid refrigerant. 
         [0012]    Another object of some embodiments is to provide a float with a streamlined shape that minimizes the gaseous pressure drop across the float. 
         [0013]    Another object of some embodiments is to incorporate a float within a manifold that is connected to a multi-coil heat exchanger. 
         [0014]    One or more of these and/or other objects of the invention are provided by a flow device that includes a float that responds to liquid refrigerant yet is generally unresponsive to relatively high flow rates of gaseous refrigerant. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  is a cross-sectional side view of a flow device that inhibits liquid refrigerant from entering a compressor. 
           [0016]      FIG. 2  is a cross-sectional view similar to  FIG. 1  but with the device&#39;s float in a raised position. 
           [0017]      FIG. 3  is a cross-sectional view taken along line  3 - 3  of  FIG. 1 . 
           [0018]      FIG. 4  is a schematic view of a refrigerant system incorporating the flow device of  FIGS. 1-3 . 
           [0019]      FIG. 5  is a schematic view of another refrigerant system incorporating the flow device of  FIGS. 1-3 . 
           [0020]      FIG. 6  is a cross-sectional view similar to  FIG. 2  but showing an alternate flow device. 
           [0021]      FIG. 7  is a cross-sectional view similar to  FIG. 1  but showing another flow device. 
           [0022]      FIG. 8  is a cross-sectional view similar to  FIG. 7  but with the device&#39;s float in a raised position. 
           [0023]      FIG. 9  is a cross-sectional view similar to  FIG. 1  but showing yet another flow device. 
           [0024]      FIG. 10  is a cross-sectional view similar to  FIG. 9  but with the device&#39;s float in a raised position. 
           [0025]      FIG. 11  is a perspective view of another flow device with a float. 
           [0026]      FIG. 12  is a cross-sectional view taken along line  12 - 12  of  FIG. 13 . 
           [0027]      FIG. 13  is a cross-sectional side view of the flow device of  FIG. 11  installed within a tubing assembly. 
           [0028]      FIG. 14  is a cross-sectional side view similar to  FIG. 13  but showing the float in a raised position rather than a lowered position. 
           [0029]      FIG. 15  is a cross-section side view of another flow device with its float in a lowered position. 
           [0030]      FIG. 16  is a cross-sectional side view similar to  FIG. 15  but showing the float in a raised position. 
           [0031]      FIG. 17  is a schematic view of a heat pump system with a flow device according to the subject invention. 
           [0032]      FIG. 18  is a cross-sectional side view of a float incorporated within a manifold of a multi-coil heat exchanger. 
           [0033]      FIG. 19  is a cross-sectional side view similar to  FIG. 18  but showing the float in a raised position rather than a lowered position. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0034]      FIGS. 1-3  illustrate a flow device  10  for virtually any refrigerant/compressor system, such as refrigerant system  12  of  FIG. 4  or system  14  of  FIG. 5 , wherein device  10  helps inhibit liquid refrigerant  16  from entering a suction port  18  of the system&#39;s compressor  20 . 
         [0035]    In  FIG. 4 , refrigerant system  12  is schematically illustrated to comprise compressor  20  for compressing a gaseous refrigerant  22 , a condenser  24  for cooling and condensing the refrigerant received from a discharge port  26  of compressor  20 , an expansion device  28  (e.g., thermal expansion valve, electronic expansion valve, orifice, capillary, etc.) for expanding and thus further cooling the refrigerant discharged from condenser  24 , an evaporator  30  for creating a cooling effect provided by the cooled refrigerant, and flow device  10  for returning refrigerant from evaporator  30  to suction port  18  of compressor  20 . In some cases, flow device  10  is connected to evaporator  30  and suction port  18  via conduits  32  and  34  respectively. 
         [0036]    Refrigerant system  14  of  FIG. 5  is similar to system  12 ; however, evaporator  30  is replaced by an evaporator  36  that includes a plurality of coils, such as coils  36   a ,  36   b  and  36   c . In this multi-coil example, expansion device  28  feeds refrigerant to each of coils  36   a ,  36   b  and  36   c . Before the refrigerant returns to suction port  18  from evaporator  36 , the refrigerant passes through a plurality of flow devices  10  corresponding to the plurality of coils  36   a ,  36   b  and  36   c . The plurality of flow devices  10  can operate independently of each other. One flow device  10 , for instance, might be freely conveying gaseous refrigerant from coil  36   a , while another flow device  10  is restricting liquid refrigerant from coil  36   c.    
         [0037]    The actual design of flow device  10  may vary. In  FIGS. 1-3 , for example, device  10  comprises a housing  38  with an inlet  40  connected to conduit  32  and an outlet  42  connected to conduit  34 . A float  44  is disposed within housing  38  such that float  44  can move between a lowered position ( FIG. 1 ) and a raised position ( FIG. 2 ). One or more guides  46  extending radially from float  44  can help maintain float  44  in its proper orientation within housing  38 . In the lowered position of  FIG. 1 , float  44  rests upon a cylindrical screen  48 . In the raised position, float  44  abuts a cylindrical valve seat  50 . 
         [0038]    Under normal operation, the refrigerant vaporizes completely within evaporator  30 , thus gaseous refrigerant  22  leaves evaporator  30  and flows to suction port  18 . This condition is illustrated in  FIG. 1 . The weight of float  44  causes float  44  to rest upon screen  48 , and gaseous refrigerant  22  flows generally upward from conduit  32 , outward through screen  48 , upward around float  44  and between guides  46 , and upward through seat  50  and conduit  34 . When float  44  is in the lowered position of  FIG. 1 , gaseous refrigerant  22  can flow freely through flow device  10 . 
         [0039]    During certain operating conditions, however, the refrigerant within evaporator  30  does not vaporize completely, so evaporator  30  begins discharging liquid refrigerant  16  into flow device  10 . This condition is illustrated in  FIG. 2 . When a certain amount of liquid refrigerant  16  enters housing  38 , the liquid refrigerant  16  causes float  44  to float. Buoyancy holds float  44  up against seat  50 , thereby partially obstructing the flow of refrigerant through device  10 . A flow-restricting passageway  52 , however, provides some restricted fluid communication between inlet  40  and outlet  42 . In some cases, passageway  52  is simply a narrow bore through float  44 . As liquid refrigerant  16  flows upward through passageway  52 , the flow restriction of passageway  52  produces a pressure drop that helps vaporize the liquid refrigerant before it returns to suction port  18  of compressor  20 . Thus, liquid refrigerant  16  is inhibited from entering compressor  20 , yet device  10  does not completely starve compressor  20  of refrigerant. 
         [0040]    In some embodiments, float  44  has a lower density than liquid refrigerant  16 . In other cases, however, a float  44 ′ has a greater density but can still float with the support of a spring  54  that helps offset the float&#39;s weight, as shown in  FIG. 6 . 
         [0041]    In another embodiment, shown in  FIGS. 7 and 8 , a flow device  56  includes a more streamlined float  58 . In the lowered position of  FIG. 7 , float  58  may provide less flow resistance to gaseous refrigerant  22 . In the raised position of  FIG. 8 , radial guides  60  abut seat  50 , and a tail section  62  of float  58  protrudes into seat  50  to create an appreciable flow-restricting annular passageway  64  between seat  50  and tail section  62 . Passageway  64  provides reduced refrigerant flow with a significant pressure drop that helps avoid conveying liquid refrigerant to suction port  18  of compressor  20 . 
         [0042]    In yet another embodiment, shown in  FIGS. 9 and 10 , a flow device  66  includes a float  68  that is situated within a housing  70  with a side inlet  72  so as to avoid obstructing the flow of gaseous refrigerant  22  flowing from inlet  72  to outlet  42  when float  68  is in the lowered position of  FIG. 9 . In the presence of liquid refrigerant  16 , as shown in  FIG. 10 , float  68  floats to a raised position to partially obstruct the flow of refrigerant through device  66 . A flow-restricting passageway  74  between float  68  and seat  50  produces a pressure drop that reduces the volumetric flow of liquid refrigerant and helps ensure the refrigerant vaporizes before it returns to suction port  18  of compressor  20 . 
         [0043]    With flow device  66 , the vertical movement of float  68  is guided by a central pin  76  that extends slidingly into a bore  78  of float  68 . To limit the upward movement of float  68  so as to create a properly sized passageway  74 , pin  76  includes a head  80  that can engage a shoulder  82  of bore  78 . 
         [0044]      FIGS. 11-14  show a flow device  84  comprising a float  86  that in the presence of liquid refrigerant  16  floats from a lowered position ( FIG. 13 ) to a raised position ( FIGS. 11 and 4 ). In the lowered position, refrigerant can flow freely around float  86  and up through a central opening  88  of an upper ring  90 . Upon floating to the raised position, float  86  in proximity with ring  90  creates a significant flow restriction at opening  88  (between float  86  and ring  88 ). The flow restriction reduces the volumetric flow of liquid refrigerant and helps ensure liquid refrigerant vaporizes before conduit  34  conveys the refrigerant to the suction port of a compressor. Fins  92  extending from float  86  and slidingly engaging a tube  94  help maintain float  86  in radial alignment with opening  88  of ring  90 . Fins  92  abutting the lower surface of ring  90  limits the upper travel of float  86 . A wire cage  96  extending from ring  90  provides a lower end stop for float  86 . 
         [0045]      FIGS. 15 and 16  show a flow device  98  comprising a tubular float  100  that in the presence of liquid refrigerant  16  floats from a lowered position ( FIG. 15 ) to a raised position ( FIG. 16 ). In the lowered position, refrigerant flows freely through a central bore  102  of float  100  and then flows upward through and around an orifice ring  104  that is held in place via radial fins  106 . In the raised position, float  100  obstructs the flow path around the outer perimeter of ring  104 , thereby leaving just a restricted flow path through a central aperture  108  of ring  104 . The restriction of ring  104  reduces the volumetric flow of liquid refrigerant and helps ensure liquid refrigerant vaporizes before a suction line  110  conveys the refrigerant to the suction port of a compressor. 
         [0046]    It should be noted that each of the aforementioned flow devices provides an open cross-sectional flow area when its float is in the lowered position and provides a restricted cross-sectional flow area when in the raised position. In currently preferred embodiments, a ratio of the open cross-sectional flow area to the restricted cross-sectional flow area is between three and seven. 
         [0047]      FIG. 17  shows how a flow device  112  (schematically representing any of the flow devices already disclosed herein) can be incorporated in a reversible heat pump system  114 . In this example, system  114  comprises refrigerant compressor  20 ; a multi-coil indoor heat exchanger  116  (evaporator or condenser); an expansion device  118 ; a multi-coil outdoor heat exchanger  120  (evaporator or condenser); and a conventional 4-way, 2-position reversing valve  122  for selective heating or cooling operation. The structure and function of heat pump systems for heating or cooling is well known to those of ordinary skill in the art. For the system illustrated in  FIG. 17 , flow device  112  helps prevent liquid refrigerant from entering suction port  18  of compressor  20  regardless of whether system  114  is operating in the cooling or heating mode. 
         [0048]      FIGS. 18 and 19  show an alternate location for float  44 . In this example, float  44  is installed within a manifold  124  connected to the downstream side of a multi-coil heat exchanger, such as heat exchanger  116  operating as an evaporator. A plurality of tubes  126  conveys refrigerant from the various coils of heat exchanger  116  and discharges the refrigerant into manifold  124 . From there the refrigerant flows to the suction port of a compressor. If one or more of the lower tubes  128  feed liquid refrigerant  16  into manifold  124 , float  44  floats upward from its lowered position of  FIG. 18  to its raised position of  FIG. 19 . Upon doing so, float  44  creates a flow restriction similar to that of  FIGS. 1 and 2 . Note, multiple floats  44  can be used in the multi-circuit configuration, only one is shown in  FIG. 19 . The flow restriction reduces the volumetric flow of liquid refrigerant and helps vaporize the liquid refrigerant before the refrigerant returns to compressor  20 . 
         [0049]    Although the invention is described with respect to a preferred embodiment, modifications thereto will be apparent to those of ordinary skill in the art. The scope of the invention, therefore, is to be determined by reference to the following claims: