Patent Publication Number: US-2019178540-A1

Title: Liquid chiller system with external expansion valve

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to non-provisional patent application U.S. Ser. No. 15/832,813, entitled LIQUID CHILLER SYSTEM, filed Dec. 6, 2017 as a Continuation in Part Application and to the non-provisional patent application U.S. Ser. No. 14/837,128, which is now the U.S. Pat. No. 9,869,496, entitled LIQUID CHILLER SYSTEM, filed Aug. 27, 2015 as a Continuation Application, which is relied upon and incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The invention relates in general to liquid chiller or refrigeration systems for cooling a liquid processed through the system, the chilled process liquid being utilized for example to maintain a storage room at a temperature well below ambient. The invention relates to such systems that utilize an expansion valve external to an evaporator. 
     Refrigeration is the lowering of the temperature of air or liquid within an enclosed space (kitchen refrigerators, store coolers, freezers, storage rooms, living quarters, etc.) by removing heat from the space and transferring it elsewhere. A typical refrigeration or chiller system utilizes a compressible refrigerant, such as for example ammonia, circulated through a closed loop assembly of interconnected devices. Refrigerant stored in a separator vessel in the gaseous or saturated vapor phase is delivered to a compressor for compression, which raises the temperature of the refrigerant. The compressed refrigerant is then passed to a condenser. A coolant liquid, such as for example water, is passed through plates, coils or tubes within the condenser to lower the temperature of the refrigerant gas such that it is condensed into a liquid refrigerant phase, the heat from the liquid refrigerant having been transferred to and removed by the coolant liquid. 
     The condensed liquid refrigerant is stored in a receiver vessel and then delivered by a flow control mechanism through an expansion valve that is located within an evaporator. The liquid refrigerant undergoes an abrupt reduction in pressure, resulting in evaporation of part of the refrigerant to further lower the temperature of the refrigerant. 
     A process liquid to be chilled, may include for example an industrial inhibited glycol and water mixture, such as one of ethylene or propylene. The process liquid, is passed through plate, coils or tubes within the evaporator such that heat from the process liquid transfers to the liquid/vapor refrigerant, causing evaporation of the liquid phase of the refrigerant and lowering the temperature of the process liquid, which is then delivered back to provide the desired cooling effect. The refrigerant vapor is passed from the evaporator into the separator vessel and the cycle is repeated. 
     It is an object of this invention to provide an improved chiller or refrigeration system that eliminates the need for an, which allows for an expansion valve to be located outside of the evaporator. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention provides a liquid chiller or refrigeration systems of the evaporator/compressor/condenser type with an expansion valve located external to an evaporator. In some embodiments, an included condenser may be an eccentric condenser wherein the plates, coils or tubes receiving the coolant liquid are positioned in the upper half of the condenser body such that the lower half of the condenser body acts as a reservoir for the condensed liquid refrigerant, and further wherein the internal volume of the condenser is sufficiently large so as to obviate the need for providing a separate, dedicated receiver vessel to retain the liquid refrigerant in line between the condenser and the evaporator. 
     Similarly, in some embodiments, an included evaporator may include an eccentric evaporator with plates, coils or tubes receiving a process liquid to be cooled located in a lower half of an evaporator body such that an upper half of the evaporator body acts as a reservoir for vaporized refrigerant. An internal volume of the evaporator may be sufficiently large so as to obviate a need for providing a separate, dedicated separator vessel to retain the vaporized refrigerant in line between the evaporator and the compressor. Preferably, the condenser is physically positioned above the evaporator such that liquid refrigerant may be gravity fed to the evaporator. 
     According to the present invention, an evaporator valve is located external to the evaporator and allows ease of access and additional efficiency. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a schematic representation of an embodiment of the chiller system. 
         FIG. 2  illustrates an alternative schematic of an embodiment of the chiller system, illustrating the eccentric evaporator and eccentric chiller. 
         FIG. 3  illustrates a block diagram of a chiller system with an expansion valve at the evaporator. 
         FIG. 4  illustrates a block diagram with an exemplary location of the expansion valve external to the evaporator with adjacent coolant piping storage. 
         FIG. 5  illustrates a block diagram of a liquid chiller system design with additional components. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to the drawings, embodiments of the invention will now be described in detail. In general, the invention is a refrigeration or liquid chiller system utilizing a refrigerant capable of possessing a liquid state and a gas/vapor state, the refrigerant being cycled through a closed loop assembly comprising a compressor, a condenser, an evaporator and an expansion valve external to the evaporator. Suitable known refrigerants include, for example, ammonia, carbon dioxide or hydrocarbons such as propane. In order to chill a process liquid, which then may be used for example to lower the temperature of an enclosed space or other gases or liquids, the refrigerant is compressed while in the vapor state and delivered to the condenser. A liquid coolant is passed through plates, coils or tubes in the condenser to lower the temperature of the refrigerant to convert the refrigerant from a compressed gas into a liquid, and the liquid refrigerant is then delivered into the evaporator and allowed to partially evaporate to a combined liquid/vapor state. The process liquid to be chilled is passed through plates, coils or tubes in the evaporator such that heat is transferred from the process liquid into the refrigerant, thereby evaporating the liquid phase of the refrigerant. The gas refrigerant is then delivered back to the compressor, and the cycle is repeated. The system is sized and structured so as not to require separate, dedicated separator (often referred to as a surge drum) or receiver vessels. 
       FIG. 1  shows a representative schematic of the chiller system. Compressor  40 , such as for example a screw or reciprocating type compressor, of suitable size and power to compress the chosen refrigerant, is operatively positioned in line and in fluid communication between the evaporator  30  and the condenser  10 . The system may utilize various known refrigerants suitable for the purpose, such as for example ammonia, CO 2  or hydrocarbons, which are capable of being compressed while in the vapor or gas phase and condensed into the liquid phase within suitable temperature and pressure ranges, for application in various commercial or residential refrigeration systems. The compressor  40  receives refrigerant in the gas phase from the evaporator  30 , compresses the gas refrigerant, and delivers the compressed gas refrigerant to the condenser  10 . A flow control mechanism  20 , comprising for example a float valve or any other suitable mechanical valve, is disposed in line between the condenser  10  and the evaporator  30  to control the flow of liquid refrigerant. Within the evaporator  30 , are conduits  32  for the process liquid flow circuit P, which portion consists of plates, coils or tubes that are the conduits  32  for the process liquid to flow through. Within the condenser, a portion of the coolant liquid flow circuit C consisting of plates, coils or tubes that are conduits  12  may be located. 
     The condenser  10  is an eccentric condenser, such as for example a plate and shell type condenser wherein the shell is oversized to increase the internal volume. The term “oversized” is used herein to define a shell having a greater capacity than required to perform the condensing operation. In the embodiment represented in  FIG. 2 , it is seen that the portion of the coolant liquid flow circuit C located internally within the condenser  10 , which portion consists of plates, coils or tubes that are conduits  12  for the coolant liquid into, through and from the condenser shell or body  11 , are positioned in the upper half of the condenser shell  11 . The conduits  12  segregate the coolant liquid from the refrigerant within the condenser  10  such that heat is transferred from the compressed gas refrigerant into the coolant liquid. The gas refrigerant thereupon condenses into its liquid phase and collects in the lower half of the condenser  10 , the lower half of the condenser defining a sump or reservoir R L . The internal volume of the oversized condenser shell  11  is sized so as to be sufficient to retain the minimum volume of liquid refrigerant necessary for continuous operation of the chiller system while simultaneously leaving room to receive the gas refrigerant from the compressor  40 . In this manner, a separate receiver vessel is not required downstream of the condenser  10  for storage of the liquid refrigerant after it has been condensed. The liquid refrigerant is then delivered from the condenser  10 , most preferably by gravity, to the evaporator  30 , the condenser  10  being positioned at a higher elevation than the evaporator  30 , as represented in  FIG. 2 . 
     A flow control mechanism  20 , comprising for example a float valve or any other suitable mechanical valve, is disposed in line between the condenser  10  and the evaporator  30  to control the flow of liquid refrigerant. 
     The evaporator  30  is an eccentric evaporator, such as for example a plate and shell type evaporator wherein the shell  31  is oversized to increase the internal volume. The term “oversized” is used herein to define a shell having a greater capacity than required to perform the evaporating operation. The liquid refrigerant is delivered from the condenser  10  through an expansion valve such that a portion of the refrigerant evaporates and creates a liquid/vapor mixture. In the embodiment represented in  FIG. 2 , it is seen that the portion of the process liquid flow circuit P located internally within the evaporator  30 , which portion consists of plates, coils or tubes that are conduits  32  for the process liquid into, through and from the evaporator shell or body  31 , are positioned in the lower half of the evaporator shell  31 . The conduits  32  segregate the process liquid from the refrigerant within the evaporator  30  such that heat is transferred from the process liquid into the liquid refrigerant, thereby lowering the temperature of the process liquid and converting the refrigerant from the liquid phase to the gas phase, which collects in the upper half of the evaporator  30 , the upper half of the condenser defining a reservoir R G . The internal volume of the oversized evaporator shell  31  is sized so as to be sufficient, if necessary, to retain the entire volume of liquid refrigerant from the condenser  10  below a high level cut-out point to insure that no liquid refrigerant passes to the compressor  40 , i.e., the evaporator shell  31  can handle a full surge volume of liquid refrigerant without allowing any liquid refrigerant to enter the conduits transporting the gas refrigerant to the compressor  40 . In this manner, a separate, dedicated separator vessel downstream from the evaporator  30  is not required for storage of the gas refrigerant after it has been evaporated. The gas refrigerant is then delivered from the evaporator  30  directly to the compressor  40  to complete the cycle. 
     With this structure the eccentric condenser  10  can be defined as having an integrated receiver vessel and the eccentric evaporator  30  can be defined as having an integrated separator vessel. Preferably, the capacity of the oversize shell  31  of the eccentric evaporator  30  is at least approximately 65% of the total volume of liquid refrigerant in the system and the capacity of the oversize shell of the eccentric condenser  10  is a least 10% of the total volume of liquid refrigerant in the system, the remaining volume of liquid refrigerant being retained in the condenser or transport piping or conduits. 
     In operation the gas refrigerant is compressed by the compressor  40  and delivered to the eccentric condenser  10 . A liquid coolant in the coolant liquid flow circuit C is passed through the plates, coils or tubes of conduits  12  in the eccentric condenser  10  to lower the temperature of the gas refrigerant to convert the refrigerant from a compressed gas into a liquid, which is retained in the liquid reservoir R L  within the eccentric condenser  10 . The liquid refrigerant is then delivered to the eccentric evaporator  30  without passage through or storage in a separate and distinct reservoir vessel. The liquid refrigerant is allowed to partially evaporate into a combined liquid/vapor state. The process liquid resident in the process liquid flow circuit P, i.e., the liquid to be chilled, is passed through the plates, coils or tubes of conduits  32  in the eccentric evaporator  30  such that heat is transferred from the process liquid into the liquid refrigerant, thereby evaporating the liquid phase of the refrigerant and cooling the process liquid. The gas refrigerant is retained in the gas reservoir R G  within the eccentric evaporator  30 , then delivered from the eccentric evaporator  30  back to the compressor  40  without passing through or storage in a separate and distinct separator vessel, and the cycle is repeated. 
     As a representative example not intending to limit the scope of the invention, the liquid chiller system may utilize ammonia as the refrigerant and glycol as the process liquid, a 529 horsepower screw compressor, an eccentric plate and shell condenser such as a Vahterus model PSHE 7/6HH-406, an eccentric evaporator such as a Vahterus model PSHE 8/6HH-438. Cooling water is provided at 82 degrees F. Such a system will cool 2,230 gpm of glycol from 33 degrees F. to 28 degrees F. while utilizing only 485 pounds of ammonia as liquid refrigerant for 446 TR (1.08 pounds/TR). During operation approximately 39 pounds (about 8% of the total volume) of the liquid refrigerant will be present in the condenser and approximately 281 pounds (about 58% of the total volume), with the remaining approximately 165 pounds (about 34% of the total volume) distributed elsewhere in the system. Such a system produces a cooling efficiency equal to or better than typical systems utilizing greater amounts of refrigerant and additional system operational components. 
     Liquid Chiller System Variations 
     There may be various system component and configuration modifications and enhancements that may be consistent with the examples as have been discussed. Referring to  FIG. 3 , a block diagram of a chiller system is illustrated including an expansion valve external to the evaporator. The liquid chiller system may include a compressor  310  that may include multiple stages such as a low stage compression ratio and a high stage compression ratio. The compressor may output to an oil separator  311  which may allow the compressed refrigerant to separate from compressor oils or other contaminants. The output of the compressor  310  may then be routed by one or a collection of pipes that may flow compressed refrigerant to a condenser  320 . Amongst various enhancements such as connections to purge systems and the like, a major connection to the unit may include treated water supply which may remove/exchange heat from the refrigerant while it is in the condenser  320 . 
     A treated water supply  321  may flow into the condenser and elements that allow the segregated flow of heat from the refrigerant to the treated water. The treated water may exit the condenser and flow through the treated water return  322 . Liquefied or partially liquefied refrigerant may flow from the condenser  320  towards the expansion valve  330  and may be stored in one or more accumulators  331  before the expansion valve  330 . Accordingly, to the present invention, the expansion valve  330  is located external to the evaporator  340 . 
     As has been described previously the refrigerant may flow in the evaporator and exchange heat with a chilled liquid such as glycol or other suitable thermal carrying liquids. A loop of the chilled liquid may deliver the chilled liquid to heat loads  342  of various types. The exchanger may also include an oil collection vessel or oil pot  341  to catch oil or other contaminants that settle out from the refrigerant. The refrigerant may then return back to the compressor  310  to be compressed and processed again as has been described. The entire system may include one or more autopurging devices  350  that may be used to remove dissolved gasses from the refrigerant in the various stages of processing. The various elements may be consistent with the eccentric components as have been described herein and their methods of operation. 
     Referring now to  FIG. 4 , a block diagram of an exemplary liquid chiller design illustrated with an expansion valve  430  is located in fluid communication with piping  431  containing a refrigerant. 
     Such an exemplary liquid chiller system may include a compressor  410  with multiple stages such as a low stage compression ratio and a high stage compression ratio. The compressor may output to an oil separator  411  which allows the compressed refrigerant to separate from compressor oils or other contaminants. The output of the compressor  410  may be routed by one or multiple pipes that flow compressed refrigerant to a condenser  420 . 
     Amongst various enhancements such as connections to purge systems and the like, a major connection to the unit may include treated water supply which may remove/exchange heat from the refrigerant while it is in the condenser  420 . A treated water supply  421  may flow into the condenser and elements that allow the segregated flow of heat from the refrigerant to the treated water. The treated water may exit the condenser and flow through the treated water return  422 . Liquefied or partially liquefied refrigerant may flow from the condenser  420  towards the expansion valve  430 . 
     In  FIG. 4 , the expansion valve  430  is located with fluid communication to piping elements  431  behind the expansion valve  430  which may be used to accumulate refrigerant in liquid and or liquid/gas mixture form. In some examples, piping elements  431  may be capable of containing an increased volume of refrigerant, such as portions or an entire length of piping with diameter that is greater than a diameter typical to a system that includes an accumulator or other refrigerant container. In preferred embodiments, piping elements  431  function as a storage of refrigerant in addition to communicating the refrigerant from a first area to a second area. 
     As has been described previously refrigerant may flow in an evaporator and exchange heat with a chilled liquid, such as glycol or other suitable thermal carrying liquids. Circulation of chilled liquid may deliver the chilled liquid to heat loads  442  of various types. An exchanger may also include an oil collection vessel such as an oil pot  441  to catch oil or other contaminants that settle out from the refrigerant. The refrigerant may be returned via additional piping back to compressor  410  where the refrigerant is compressed and processed again as described. 
     The system  400  may include one or more autopurging devices  450  that may be used to remove dissolved gasses from the refrigerant in the various stages of processing. Although the various elements may be consistent with the eccentric components as have been described herein and their methods of operation, the modified location of the expansion valve and the use of piping elements before the expansion valve in the dual purpose of storing refrigerant may also be utilized with non-eccentric components. When the expansion valve  430  is located in a location exterior to the evaporator  440 , there may be numerous types of valves that could be used for the control of the refrigerant including by way of non-limiting example, sense motorized valves and float type valves. Furthermore, types of refrigerant consistent with this design may include ammonia, but also non-ammonia type refrigerants such as HFC R134a, HFO, CO2, Hydrofluorocarbons and hydrocarbon-based refrigerants. 
     Advanced Liquid Chiller Design Aspects 
     Referring to  FIG. 5 , a liquid chiller system design is shown with additional components is illustrated. In some examples, a condenser  510  may include evaporative cooling. A multistage compressor  520 ,  521  and  522  may be included in a refrigerant loop provided by piping and components establishing fluid communication between the components of the system. 
     In some examples, a stage of a refrigerant loop may be a high compression stage in relation to an output of a low or lower compression stage. Variations may include incorporation of multiple loops of refrigerant into different stages, and an output of disparate stages may be routed to selected components within the liquid chiller system. Compressor outputs may be routed to low temperature accumulators  530  and high temperature accumulators  531  which may provide segregated loops to low temperature loads  570  and high temperature loads  580  respectively. In some embodiments, a single vessel accumulator  532  may include multiple chambers. Although the single vessel accumulator  532  is illustrated with two chambers, additional chambers are also within the scope of invention. For example, as illustrated a first chamber may be a low temperature chamber (LTA Chamber)  530 , and a second chamber may be a high temperature chamber (HTA chamber)  531 . The single vessel accumulator  532  may be divided into separate chambers by a plate between the chamber regions. Typically, a temperature of an accumulator chamber such as the low temperature chamber  530  or the high temperature chamber  531  will be dependent upon an amount of compression of the refrigerant as well as other factors. 
     Specialized components may be configured to control the transfer of liquids between various components such as the liquid transfer unit  540 . Secondary storage elements such as the high-pressure receiver  550  may give the system flexibility and ability to buffer various loading needs. In some examples, a heat exchanger  560 , may be used to exchange heat between the fluids stored in the low temperature chamber  530  and the high temperature chamber  531 . The system  500  may also include an autopurging system  590  to remove gasses from the refrigerant streams. 
     It is contemplated that equivalents and substitutions for elements and structures set forth, described and illustrated above may be obvious to those of ordinary skill in the art, and therefore the true scope and definition of the invention is to be as set forth in the following claims.