Abstract:
An air conditioning or refrigeration system includes an attached refrigerant receptacle associated with the system. During shipment or storage, the pressure within the system may exceed a selected threshold for the low pressure side. Under such circumstances, a pressure relief device automatically allows refrigerant to flow from the system into the attached receptacle, which brings the pressure within the system back to an acceptable level for the low pressure side. Various optional shutoff devices are disclosed that can be incorporated into the design to simplify receptacle removal or recycling.

Description:
FIELD OF THE INVENTION 
   This invention generally relates to refrigerant systems. More particularly, this invention relates to controlling pressure within an air conditioning or refrigeration system during storage or transportation. 
   DESCRIPTION OF THE RELATED ART 
   Air conditioning systems typically utilize a refrigerant to achieve a desired amount of cooling within a building, for example. Systems typically are charged at a factory with an amount of refrigerant to provide adequate system performance for expected operating conditions. 
   The refrigerant system can be divided into low and high pressure sides. The low pressure side is the system side that is exposed to lower, suction pressure during operation. The high pressure side is the system side that is exposed to higher, discharge pressure during operation. During operation the discharge pressure is normally several times higher than suction pressure. However, when the system is shutdown, both suction and discharge pressure equal each other soon after shutdown. 
   The low pressure side of the system reaches the highest pressure during system transportation or storage. The pressure in the low pressure side during transportation or storage can be several times higher than the maximum pressure the low side of the system experiences during normal system operation. The system components typically must be designed with a safety margin sufficient to withstand such pressure. The associated increases in component strength cause increased component cost and weight. 
   With the introduction of higher pressure refrigerants, such as R410A, the above concerns are increased. Additionally, certain governing bodies are introducing new, more stringent high pressure strength requirements. It is desirable to provide a cost-effective way to deal with this situation. 
   This invention provides a way to manage the pressure within the refrigerant system during transportation or storage that avoids the shortcomings and drawbacks described above. 
   SUMMARY OF THE INVENTION 
   In general terms, this invention is a unique way of managing the pressure within a refrigerant system during transportation or storage. 
   One example system designed according to an embodiment of this invention includes a refrigerant receptacle and a pressure relief device that couples the receptacle to the system. The pressure relief device operates responsive to a pressure in the system that exceeds a selected threshold. Accordingly, refrigerant from the system can flow into the refrigerant receptacle whenever the pressure in the system exceeds the threshold. 
   In one example, the pressure relief device includes a valve that will automatically open responsive to an undesirably high pressure in the system and release the refrigerant into the receptacle. The receptacle provides additional volume within which the refrigerant can be contained, which reduces the pressure in the system. This approach avoids the necessity of over-designing the air conditioning system low pressure side components, such as a compressor and an evaporator, and, therefore, provides an associated cost savings. Various shutoff and recovery valves and devices can be added to the receptacle for convenience, as well. 
   The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the currently preferred embodiment. The drawings that accompany the detailed description can be briefly described as follows. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  schematically illustrates a refrigerant system including a refrigerant receptacle for managing a pressure within the system during transportation or storage, for example. 
       FIG. 2  schematically illustrates another example arrangement of a system designed according to this invention. 
       FIG. 3  schematically illustrates another example arrangement of a system designed according to this invention. 
       FIG. 4  schematically illustrates another example arrangement of a system designed according to this invention. 
       FIG. 5  schematically illustrates another example arrangement of a system designed according to this invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1  schematically shows a refrigerant system  20  that may be used as a refrigeration system, a heat pump or an air conditioning system. In a cooling mode, a compressor  22  draws refrigerant from a suction port  24  and provides a compressed gas under pressure to a compressor discharge port  26 . The high temperature, pressurized gas flows through a conduit  28  to a condenser  30  where the gas dissipates heat and condenses into a liquid as known. The liquid refrigerant flows through a conduit  32  to an expansion device  34 . In one example, the expansion device  34  is a valve that operates in a known manner to allow the liquid refrigerant to expand and to partially evaporate and flow into a conduit  36  in the form of a cold, low pressure refrigerant. This refrigerant then flows through an evaporator  38  where the refrigerant absorbs heat from air that flows across the evaporator coils, which provides cooled air to the air conditioned space as known. The refrigerant exiting the evaporator  38  flows through a conduit  40  to the suction port  24  of the compressor  22  where the cycle continues. As known, during a heating mode, the refrigerant flows are reversed. 
   The system  20  has a high pressure side, in which the components are exposed to discharge pressure, between the discharge section of the compressor  22  and the entrance to the expansion device  34 . A low pressure side, in which the components are exposed to suction pressures, exists between the exit from the expansion device  34  and the suction section of the compressor  22 . 
   The illustrated example includes an external refrigerant receptacle  50  that is coupled to the system for selective fluid communication. In this example, a pressure relief device  52  selectively allows refrigerant to flow from the system into the receptacle  50  whenever the pressure in the system exceeds a selected threshold. By coupling the receptacle  50  to the system, the example arrangement effectively increases the volume within which the refrigerant can be contained, which reduces the pressure. Accordingly, whenever the pressure in the system exceeds a selected threshold for the low pressure side, adding the volume of the external receptacle  50  to the system volume allows the pressure in the system to be brought back down to an acceptable level. 
   In one example, the threshold is dictated by the chosen refrigerant, system component strength on the system low pressure side or the limits set by an appropriate regulatory or governing body. Those skilled in the art who have the benefit of this description will be able to select an appropriate threshold to suit their particular situation. 
   In another example as shown in  FIG. 2 , an optional valve  54  is provided. The flow control valve  54  is a shut-off valve that allows for selectively isolating the receptacle  50  from the relief device  52 , which in this example is a rupture disk, or the system. In this example, the valve  54  is utilized in case the receptacle  50  is removed from the system and needs to be installed once again in other units for same purpose during transportation or storage. It also can be used if the rupture disk  52  was ruptured due to pressure in the system  20  exceeding the allowable pressure threshold and just the receptacle needs to be removed to be reused, for example. 
   Another example designed according to the embodiment of  FIG. 2  has a flow control valve  54  that operates as a check valve to allow flow of refrigerant in only one direction from the system to the receptacle  50 . 
   In another example shown in  FIG. 3 , an optional valve  56  is provided to selectively isolate the rupture disk  52  along with the receptacle  50  from the rest of the system  20  for recycling or any other purpose. Although the receptacle  50  and the rupture disk  52  are shown associated with the conduit  40 , a connection to any appropriate part of the system is within the scope of this invention. 
     FIG. 4  illustrates another example embodiment that includes both optional valves  54  and  56 . 
   The example of  FIG. 5  includes an optional access valve  58  that allows for reclaiming refrigerant from the receptacle  50  or initially pressurizing the receptacle  50  with a selected amount of refrigerant to a specified pressure. 
   The receptacle  50  may be at vacuum or contain a small amount of refrigerant during system assembly and charging with the refrigerant, at a factory, for example. Any refrigerant within the receptacle  50  preferably is kept at a pressure well below the pressure of the non-operating system to maximize the amount of refrigerant that can flow into the receptacle  50  in the event that the pressure in the system exceeds the selected threshold. 
   When refrigerant is released into receptacle  50 , preferably there is a visible indication of when the refrigerant release has occurred. This allows a technician to have a visual confirmation that refrigerant was released into the receptacle  50 . If that did occur, a technician can add charge to the system to account for any refrigerant that was transferred into the receptacle during shipping or storage. In most probable scenario, the pressure relief device will not have been activated and the technician can proceed with system installation as normal. 
   In some of the illustrated examples, the external receptacle  50  may be selectively removed from the system once the system is installed at the selected site so that the receptacle can be reused with another system that will be charged in a factory. Alternatively, if the receptacle  50  is connected to low pressure side of the system, it may be left in place and the pressure relief device  52  set for activation in the unlikely event that the low pressure side becomes over-pressurized during system operation. 
   The illustrated examples provide cost effective ways to handle low side system over-pressure during shipment or storage to prevent overpressurisation above an established, acceptable limit. 
   The preceding description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the essence of this invention. The scope of legal protection given to this invention can only be determined by studying the following claims.