Abstract:
A refrigerant system is provided where the functions of an economizer heat exchanger and liquid-suction heat exchanger are combined. The two configurations are disclosed with a single common heat exchanger construction. In a first configuration, a series of valves selectively routes only one of two possible refrigerant flows through a common heat exchanger such that a control can selectively activate either an economizer heat exchanger circuit or a liquid-suction heat exchanger function. In a second configuration, both refrigerant flows are passed to the common heat exchanger through separate fluid lines and are selectively activated by the control. Variations of the second configuration are also disclosed.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     This invention relates to a refrigerant system that incorporates an economizer heat exchanger and liquid-suction heat exchanger within a single common heat exchanger construction.  
         [0002]     Refrigerant systems are utilized in applications to change the temperature and humidity or otherwise condition the environment. In a standard refrigerant system, a compressor delivers a compressed refrigerant to an outdoor heat exchanger, known as a condenser. From the condenser, the refrigerant passes through an expansion device, and then to an indoor heat exchanger, known as an evaporator. In the evaporator, moisture may be removed from the air, and the temperature of air blown over the evaporator coil is lowered. From the evaporator, the refrigerant returns to the compressor. Of course, basic refrigerant systems are utilized in combination with many configuration variations and optional features. However, the above provides a brief understanding of the fundamental concept.  
         [0003]     An enhancement technique known as an economizer cycle has been utilized in refrigerant systems. The economizer circuit increases the capacity and efficiency of a refrigerant system. When the economizer circuit is functioning, a refrigerant is tapped from a main liquid refrigerant line at the position downstream of the condenser. This tapped refrigerant is expanded to a lower pressure and temperature and then passed through a heat exchanger where it exchanges heat to cool the main refrigerant flow. This tapped refrigerant is then returned to the compressor through the intermediate compression port. The main refrigerant flow having been cooled in the economizer heat exchanger has a greater cooling capacity when it reaches the evaporator.  
         [0004]     Another way to increase refrigerant system performance is to use a liquid-suction heat exchanger. In such an arrangement, refrigerant downstream of the evaporator is passed through a heat exchanger where it subcools liquid refrigerant flowing from the condenser to the expansion device. This scheme provides additional cooling capacity when the refrigerant reaches the evaporator, but at the expense of having higher temperature and lower density refrigerant reaching the compressor.  
         [0005]     The use of the economizer heat exchanger option would provide the most benefits under some operating conditions, while the use of the liquid-suction heat exchanger would provide the most benefits under other operating conditions. In the past, the designer had to choose between using either one option or the other. Providing both options has been expensive and somewhat cumbersome as two separate heat exchangers were required.  
       SUMMARY OF THE INVENTION  
       [0006]     In the disclosed embodiment of this invention, the functions of the economizer heat exchanger and liquid-suction heat exchanger are provided within a refrigerant system, utilizing a single common heat exchanger construction. In a first schematic, a tap downstream of the condenser provides two refrigerant flows through a common heat exchanger. Another tap downstream of the evaporator selectively routes the refrigerant through the same common heat exchanger. A plurality of flow control devices such as valves are placed across the system to allow control and proper routing of refrigerant flow in various modes of operation. By selectively opening and closing these valves, the system can provide an economizer function, or the liquid-suction heat exchanger function, utilizing a single, common heat exchanger construction.  
         [0007]     In a second schematic, the refrigerant downstream of the evaporator always passes through a common heat exchanger to provide the liquid-suction heat exchanger function. The economizer function is achieved selectively by activating an economizer circuit to pass tapped refrigerant through the common heat exchanger. In another variation of the second schematic, a bypass can allow at least a portion of refrigerant downstream of the evaporator to bypass this common heat exchanger, thus effectively disengaging a liquid-suction heat exchanger section (partially or entirely) from the active refrigerant circuit. In yet another variation of the second schematic, a flow control device selectively routes the refrigerant to a liquid-suction heat exchanger, or directly to the evaporator, while an economizer function and a liquid-suction heat exchanger function may be provided by separate units.  
         [0008]     These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]      FIG. 1  is a first schematic of the present invention.  
         [0010]      FIG. 2A  is a second schematic of the present invention.  
         [0011]      FIG. 2B  shows an option that may be incorporated into the  FIG. 2A  schematic.  
         [0012]      FIG. 2C  shows a variation of the  FIG. 2B  schematic.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0013]     A refrigerant system  20  is illustrated in  FIG. 1 , having a compressor  22  compressing refrigerant and delivering it downstream to a condenser  24 . An expansion device  26  is positioned downstream of condenser  24 , and an evaporator  28  is located downstream of the expansion device  26 . An economizer tap  30  taps a portion of refrigerant through an economizer expansion device  32 , and then through a common heat exchanger  31 . Refrigerant also passes through the common heat exchanger  31  from a main liquid refrigerant line  36  downstream of the condenser  24 . A supply line  48  delivers refrigerant from tap  30  through the common heat exchanger  31  when a valve  46  is open. Thus, to provide an economizer function, refrigerant passes through the economizer expansion device  32 , and through the opened valve  46  into the common heat exchanger  31 . It should be noted that the valve  46  may not be needed in case the economizer expansion device  32  can be controlled to an entirely closed position.  
         [0014]     Another tap  40  is tapped from a point  42  downstream of the evaporator  28 . The tap  40  also communicates with the supply line  48  passing through the common heat exchanger  31 . A valve  54  downstream of the evaporator  28  is closed and a valve  56  is opened to deliver the refrigerant through the tap  40  to the common heat exchanger  31 .  
         [0015]     In addition, a valve  50  is placed on an economizer return line  34  delivering refrigerant back to the compressor  22  at some intermediate (between suction and discharge) pressure. Another valve  52  is placed on a bypass line  38  communicating refrigerant flowing in the return line  34  back to a point  44  and then returning it through a suction line  45  to the suction port of the compressor  22 .  
         [0016]     The refrigerant system can operate in a conventional non-economized mode, and without a liquid-suction heat exchanger function by closing the valves  46  and  56  and opening the valve  54 . Also, at least one of the valves  50  or  52  has to be closed to prevent the refrigerant bypass flow from an intermediate compressor port back to suction. Refrigerant will then flow through a basic conventional cycle.  
         [0017]     If an unloader function is desired, the valves  50 ,  52  and  54  are opened and the valves  46  and  56  are closed.  
         [0018]     If an evaporator bypass function is desired, the valves  46 ,  54  and  56  are opened with the valves  50  and  52  are closed.  
         [0019]     If an economizer function is desired, the valves  46 ,  50  and  54  are opened and the valves  52  and  56  are closed.  
         [0020]     In case an unloader function is desired in the economized mode of operation, the valves  46 ,  50 ,  52  and  54  are opened and the valve  56  is closed.  
         [0021]     If instead of an economizer function, a liquid-suction heat exchanger function is desired, the valves  46 ,  50  and  54  are closed and the valves  52  and  56  are opened. Refrigerant will now flow through the tap line  40 , into the supply line  48 , through the common heat exchanger  31 , and will subcool the refrigerant in a main line  36 . That refrigerant will pass back through the return line  34 , through the bypass line  38 , and return to the point  44  in the suction line  45  leading back to the suction port of the compressor  22 .  
         [0022]     The unloader function can also be achieved in combination with the liquid-suction heat exchanger function by opening the valve  50 .  
         [0023]     The above embodiment utilizes a single common heat exchanger to provide the function of either an economizer heat exchanger, or a liquid-suction heat exchanger. Thus, more flexibility is given to the refrigerant system designer, without the requirement of two distinct auxiliary heat exchangers. Of course, an appropriate control with the appropriate programming to actuate the proper flow control devices to achieve desired operating conditions in a desired mode of operation is to be included.  
         [0024]     Also, a combination of the operating modes described above can be executed by opening and closing appropriate flow control devices. For instance, an evaporator bypass may be simultaneously provided with the economizer function, if desired. Furthermore, as known, the economizer tap can be located downstream of the heat exchanger  31  providing identical benefits to a system designer. It should also be pointed out that a function of two separate valves adjacent to a common piping junction can be substituted by a single multi-functional valve that can route the flow of refrigerant through the junction in the appropriate directions.  
         [0025]      FIG. 2A  shows another embodiment  60  with the economized compressor  62 . Refrigerant downstream of the compressor  62  passes through a condenser  68 , a main expansion device  70 , and an evaporator  72 . A common heat exchanger  74  receives refrigerant from an economizer circuit tap line  76  through an economizer expansion device  78 . The tapped refrigerant would flow through an economizer circuit return line  80  back to the economizer port of the compressor  62  at some intermediate pressure. The main liquid refrigerant line  82  downstream of the condenser also passes through the common heat exchanger  74 . A line  84  downstream of the evaporator  72  passes through the common heat exchanger  74  as well, and then back to a suction line  86  that returns refrigerant to the suction port of the compressor  62 . This schematic selectively provides an economizer function by opening or closing the economizer expansion device  78 . In case the economizer expansion device  78  is not equipped with a shutoff capability, a separate shutoff valve is needed. The liquid-suction heat exchanger function will always take place, as the line  84  is a dedicated line passing through the common heat exchanger  74 . In the common three-stream heat exchanger  74 , heat transfer interaction occurs between liquid refrigerant in the line  82 , a two-phase refrigerant in the line  76  (when the valve  76  is open) and a vapor refrigerant in line  84 . As a result, liquid refrigerant is subcooled and system performance is enhanced. Furthermore, the economizer function may be only activated when an additional performance boost is desired.  
         [0026]      FIG. 2B  shows an option wherein a valve  89  (when closed) forces vapor refrigerant flow through a bypass line  88  to the suction line  84 . This causes the refrigerant to bypass the common heat exchanger  74  when the liquid-suction heat exchanger function is not desired. That is, when the liquid-suction heat exchanger function is desired, a valve  90  is closed and a valve  89  is opened. On the other hand, when the liquid-suction heat exchanger function is not desired, the valve  89  is closed and the valve  90  is opened. It should be understood that a function of the two valves  89  and  90  can be combined into a single three-way valve that would selectively route the refrigerant into the line  88  by-passing the common heat exchanger  74 , or block the refrigerant from entering the line  88  to route it through the common heat exchanger  74 .  
         [0027]     Another embodiment  100  shown in  FIG. 2C  is a variation of the configuration presented in  FIG. 2B . In this embodiment, an economizer function and a liquid-suction heat exchanger function are provided by separate units,  112  and  124  respectively, while a three-way valve  114  selectively routes the refrigerant through or around the liquid-suction heat exchanger  124 .  
         [0028]     An economized compressor  102  delivers refrigerant to a downstream condenser  104 . A tap  106  from a main liquid refrigerant line  108  passes through an economizer expansion device  110 , which is also utilized as a shut-off valve in this schematic. The refrigerant from both the tap  106  and main liquid refrigerant line  108  flows through the economizer heat exchanger  112 . In fact, while the two are shown flowing in the same direction, in practice, it would be preferable if they were in a counter-flow relationship. If no economizer function is desired, then valve  110  is shut. The three-way valve  114  receives the refrigerant downstream of the economizer heat exchanger  112 . The three-way valve  114  directs the refrigerant to a line  116 , and then to a line  118  leading to a main expansion device  120 , and an evaporator  122 . The flow position of the three-way valve  114  for the line  116  is selected when no liquid-suction heat exchanger function is desired. Downstream of the evaporator  122 , refrigerant passes through a liquid-suction heat exchanger  124 , to a suction line  126 , and then back to the compressor  102 . Since there is no other refrigerant flow passing through the liquid-suction heat exchanger  124 , no liquid-suction heat exchanger function is achieved when the valve  114  is in this position.  
         [0029]     When a liquid-suction heat exchanger function is desired, the valve  114  directs the refrigerant into a line  128 . The line  128  directs the refrigerant through the liquid-suction heat exchanger  124  for the heat transfer interaction with the refrigerant exiting the evaporator  122 . The refrigerant having passed through the line  128 , through the liquid-suction heat exchanger  124 , then passes into the line  118 , through the main expansion device  120 , and then to the evaporator  122 . As was mentioned above, the refrigerant downstream of the evaporator  122  flows through the liquid-suction heat exchanger  124  once again and then returns to the suction port of the compressor  102 . As in previous embodiments, this schematic achieves the benefits of an economizer function and a liquid-suction heat exchanger function.  
         [0030]     In all the embodiments, the economizer flow can be tapped downstream of the common/economizer heat exchanger, not altering any of the benefits of the invention. Also, it is well understood by a person ordinarily skilled in the art that a single economized compressor can be replaced by a compound compressor or a two-stage compression system that would provide the same benefits as described above.  
         [0031]     The present invention provides a few schematics that would achieve the function of both a liquid-suction heat exchanger and an economizer heat exchanger with a single common heat exchanger. Obviously, a worker of ordinary skill in the art would recognize that many schematics would also be able to provide the function, as long as a single heat exchanger provides both functions, it would be within the scope of this invention.