Abstract:
A refrigerant cycle is provided with a compressor system, capable of simultaneously delivering refrigerant to multiple condensers operating at different temperature levels. A single evaporator communicates with these condensers. One of the condensers receives fully compressed refrigerant while the others receives refrigerant at an intermediate pressure. A control can optionally direct refrigerant to only one of these condensers to achieve desired heat rejection and other operational characteristics. Various system configurations with multiple compressors and condensers are also disclosed.

Description:
BACKGROUND OF THE INVENTION 
   This application relates to a refrigerant cycle having a common evaporator, but separate condensers, where one of the condensers is connected to an intermediate pressure compression stage, while the other condenser is connected to the high pressure compression stage. 
   Refrigerant cycles 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 a heat exchanger, known as a condenser, which is typically located outside. From the condenser, the refrigerant passes through an expansion device, and then to an indoor heat exchanger known as an evaporator. At 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 cycles are utilized in combination with many configuration variations and optional features. However, the above provides a brief understanding of the fundamental concept. 
   Refrigerant cycles are known, wherein a so-called economizer circuit is incorporated. In an economizer circuit, a first refrigerant line is tapped from a main refrigerant line downstream of the condenser. The tapped refrigerant line is passed through an expansion device, and then the tapped refrigerant and the main refrigerant both flow through an economizer heat exchanger. The tapped refrigerant subcools the main refrigerant, such that when the main refrigerant reaches an evaporator, it will have a greater cooling potential. The tapped refrigerant, having subcooled the main refrigerant, is returned to the compressor at an intermediate compression point. 
   The present invention redirects the flow of refrigerant from an intermediate compression point in a compressor to selectively provide refrigerant to at least one of a plurality of condensers, where each of the condensers operate at different temperature levels. In this manner, the heat rejection characteristics of the refrigerant cycle can be controlled to provide a variety of options to a refrigerant cycle designer and to satisfy a wide spectrum of applications. 
   SUMMARY OF THE INVENTION 
   In the proposed system design, a portion of the refrigerant, compressed to some intermediate pressure, leaves a compressor at an intermediate port, while the rest of the refrigerant vapor continues through the compression process to a main discharge port and then to a first (main) condenser. The refrigerant that leaves the intermediate discharge port is connected to another (second) condenser. Consequently, for this system an additional temperature level of heat rejection is available. Such heat rejection capability at various temperature levels can be utilized in multiple industry applications where condensers are located within different environments. For example, for cooling applications, where the evaporator is located indoors, the main condenser can be located outdoors, while the second condenser is located indoors. Another application would be for heat pump heating installations, where there are two environmental chambers each requiring a different amount of heating. In this case, one chamber will be heated by air passing over first condenser, while the other chamber will be heated by air passing over the other condenser. The amount of refrigerant flowing through each condenser can be regulated by the respective expansion devices, as explained below. In the present invention, a refrigerant cycle is provided with a common evaporator receiving refrigerant from at least two condensers. 
   In several embodiments, there may be more than one compressor connected in series, or a single compressor with the intermediate compression ports can selectively deliver refrigerant to at least two condensers. Also, multiple compressors may be connected in banks to provide more flexibility in the refrigerant flow control and system performance. Moreover, a compressor can have several intermediate compression ports, each connected to a separate condenser. 
   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 
       FIG. 1  is a first schematic. 
       FIG. 2  is a second schematic. 
       FIG. 3  is a third schematic. 
       FIG. 4  is a fourth schematic. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1  shows a refrigerant cycle  20  having a single compressor  22  delivering compressed refrigerant to a discharge line  24 . Discharge line  24  communicates with a first condenser  26 . Refrigerant passes through the condenser  26  and then to an expansion device  30 . At connection  34 , refrigerant is received downstream of the expansion device  30 , and delivered to an evaporator  32 . The refrigerant from the evaporator  32  returns to the compressor  22 . An intermediate pressure tap line  36  passes through an optional shut-off valve  28 , and delivers a refrigerant vapor compressed to an intermediate pressure level (between suction pressure and discharge pressure) to a second condenser  40 . The shut-off valve  28  can be closed if under some operating conditions there is a need to route all of the refrigerant entering the compressor  22  through a discharge line  24 . Otherwise, the shut-off valve  24  would normally be open. An expansion device  42  is positioned downstream of condenser  40 . The refrigerant in the condensers  40  and  26  would be at a distinct temperature and pressure. The two condensers can be utilized to provide more effective control over the overall operation of the refrigerant cycle. As mentioned above, there would be reasons why a worker of ordinary skill in the art would want to have greater control over the heat rejection characteristics of the refrigerant cycle  20 . This two-condenser system provides greater system control and flexibility as well as covers an extended range of various applications. It should also be obvious to a worker of ordinary skill in the art to extend this arrangement to a compressor that will have several staged intermediate ports, as described in U.S. Pat. No. 6,694,750. In this case, each of those intermediate ports can be connected to a separate condenser. 
   A control  37  controls the various devices and components in the refrigerant cycle  30  to achieve the desired characteristics. 
     FIG. 2  shows a more complicated refrigerant cycle  50 . As shown, a discharge manifold  52  is positioned to be downstream of a first compressor bank  54  and a second compressor bank  56 . As should be understood, the compressor banks  54  and  56  are each tandem compressors that receive refrigerant from a common evaporator  32  and deliver the refrigerant to a common condenser  26 . 
   The refrigerant downstream of the condenser  26  passes through an expansion device  30 , into a line  34 , and then to the evaporator  32 , as in the previous embodiment. 
   A tap line  62  from an intermediate compression point associated with one of the compressors in the bank  54  passes refrigerant through an optional shut-off valve  64 , and through an optional shut-off valve  66 , to a second condenser  40 . An expansion device  42  is positioned downstream of the condenser  40 . A second tap line  67  taps refrigerant from a second of the compressors in the compressor bank  54 , again at an intermediate pressure. The shut-off valves  28 ,  64  and  66 , as explained above, would block the flow from the compressor banks to each of the condensers  26  and  40 . The location of the shut-off valves is provided for illustration purpose, as other locations are possible as long as they provide a function of blocking the flow out of the intermediate compression ports. 
   The refrigerant cycle  50  operates in a similar fashion as a refrigerant cycle  20 . Refrigerant is tapped to the condenser  40  when heat rejection at a lower temperature is desired. Thus, a designer is provided with the options of greater control over the heat rejection characteristics and overall operation of the refrigerant cycle  50 . 
     FIG. 3  shows yet another schematic  100 , wherein there are serially connected compressors  102  and  104 . A tap  106  downstream of the second stage compressor  104  delivers refrigerant to a condenser  108 . A tap  110  downstream of the first stage compressor  102  delivers refrigerant to another condenser  112 . For purposes of this application, this embodiment  100  would be delivering a refrigerant at an “intermediate” pressure (tap  106 ) to the condenser  112 . 
     FIG. 4  shows an embodiment  150 , having a compressor  152 , such as mentioned above, wherein there are plural intermediate taps  154  and  156 . Each of these intermediate taps selectively delivers a refrigerant to one of the condensers  155 . As shown, the discharge line  160  leads to its own condenser  162 . Thus, the embodiment  150  has three condensers. Of course, more condensers operating at different temperature levels can be utilized as desired. 
   Furthermore, other multiples of compressors and compressor banks can be utilized within the scope of this invention. As known in the art, multiple tandem compressors provide more flexibility in the refrigerant flow control and system performance characteristics. 
   Obviously, more than two or three condensers may be utilized within a single system to allow heat rejection at more than two or three temperature levels. Furthermore, these condensers can be supplied with the refrigerant by a compression system with either multiple intermediate compression ports or multiple compressors connected in series. 
   Although preferred embodiments of this invention have been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.