Patent Publication Number: US-2007107886-A1

Title: Evaporator for a refrigeration system

Description:
TECHNICAL FIELD  
      The present invention relates to refrigeration systems. More particularly, the present invention relates to evaporators for centrifugal compressor refrigeration systems.  
     BACKGROUND OF THE INVENTION  
      Centrifugal chillers, which are the workhorses of the comfort cooling industry, have very few moving parts (Prior Art  FIG. 1 ). Therefore, they usually offer high reliability and low maintenance requirements. A centrifugal compressor of the centrifugal chiller acts very much like a centrifugal fan, compressing the vapor flowing through it by spinning it from the center of an impeller wheel radially outward, allowing centrifugal forces to compress the vapor. Some machines use multiple impellers to compress the refrigerant in stages.  
      The compressor is in fluid communication with an evaporator, as depicted in prior art  FIG. 2 . The evaporator acts to change the state of a refrigerant from a liquid to a vapor by warming the refrigerant. The refrigerant vapor exits the evaporator at a suction nozzle under the motive force of a suction applied thereto by the compressor. It is important for the operating life of the compressor that an liquid refrigerant passing out through the suction nozzle be absolutely minimized, such liquid having a deleterious effect on compressor components.  
      There is a need in the industry to make a more tolerated evaporator for liquid carry-over and less pressure drop in the waterside. Liquid carry-over, as noted above, has the potential for damaging or reducing the life of centrifugal compressors. Further, liquid carry-over reduces the cooling capacity and efficiency of the refrigeration system.  
     SUMMARY OF THE INVENTION  
      The present invention substantially meets the aforementioned needs of the industry. The present invention affords the following advantages as compared to prior art refrigeration systems:  
      Less pressure drop;  
      Reduced liquid carry-over;  
      More efficient evaporator and tolerated evaporator for carry-over; and  
      Utilizes fewer tubes for the same shell length.  
      Further potential advantages include:  
      The drop liquid may heated near the shell support plate by water under the baffle plate; and  
      The shell head near the suction nozzle may not be needed.  
      The present invention is an evaporator for a refrigeration system, including a baffle plate extending over a portion of a tube bundle assembly, the baffle plate preventing liquid refrigerant carried over by suction nozzle above, the baffle plate assisting in directing a fluid flow from a tube first portion to a tube second portion. The present invention is further a method of forming an evaporator. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a partially cut away depiction of a prior art centrifugal compressor refrigeration system;  
       FIG. 2  is perspective view of a cut away prior art evaporator; and  
       FIG. 3  is a cut away perspective view of an evaporator of the present invention.  
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS  
      The evaporator of the present invention is shown generally at  10  in  FIG. 2 . Evaporator  10  is intended to be employed in a refrigeration system such as depicted in Prior Art  FIG. 1 . Such refrigeration system can be configured to employ the present invention simply by replacing the evaporator depicted in  FIG. 1  with the evaporator  10  of the present invention.  
      The evaporator  10  has two major subcomponents: shell assembly  12  and tube bundle assembly  14 .  
      The shell assembly  12  of the evaporator  10  includes a cylindrical shell  16 . Typically, the shell assembly  12  is 9 to 16 feet in length. The cylindrical shell  16  is sealingly capped at either end by a shell head  68 . The shell support plate  18  of  FIG. 3  is the leftmost shell support plate  18  of the evaporator  10 , the rightmost shell support plate  18  not be depicted. Each of the shell support plates  18  is a solid rectangular plate for fluidly sealing the interior cavity  22  defined with the cylindrical shell  16 . A plurality of bores  20  are defined in shell support plate  18  for bolting the shell support plate  18  to the respective end of the cylindrical shell  16 . A refrigerant suction nozzle  24  is disposed on the upper surface of the cylindrical shell  16  proximate the leftmost shell support plate  18 . The refrigerant inlet  78  is at the bottom of the shell  16 .  
      The second subcomponent of the evaporator  10  is the tube bundle assembly  14 . The tube bundle assembly  14  includes lower portion tubes  26  and upper portion tubes  28 . The tube ends  30  of the tubes  26 ,  28  are expanded and sealed at tube sheet  32 . The tube sheet  32  is spaced apart from the inner margin of the shell support plate  18 . A plurality of spaced apart tube supports  34  extend the length of the shell assembly  12  to support the tube bundle assembly  14 .  
      A water pass vane  36  is disposed leftward of the tube sheet  32 . The water pass vane  36  provides for the demarcation between the lower portion tubes  26  and the upper portion tubes  28  in an evaporator in which the liquid refrigerant flows in at the bottom and refrigerant vapor flows out at the top, as depicted in  FIG. 1 . It is understood that the configuration of the present invention can be rotated 90 degrees to define a side to side type evaporator. The water pass vane is then positioned vertically so that the water passage is from side to side.  
      The water pass vane  36  is generally rectangular and has spaced apart parallel side margins  38 . Each of the two side margins  38  is sealingly coupled to the interior margin of the cylindrical shell  16 . The distal margin  40  of the water pass vane  36  is fixedly coupled to the tube sheet  32 . The proximal margin  42  of the water pass vane  36  extends leftward therefrom and is spaced apart from the interior margin of the shell support plate  18 . The proximal margin  42  in cooperation with the interior margin of the shell support plate  18  in part define a water passageway  44  between the lower portion tubes  26  and the upper portion tubes  28 .  
      Two sides of the baffle plate are welded on the inside surface of the shell. The bottom surface of the baffle plate  46  is welded on the top of the tube sheet  32 . The front edge of the baffle plate is welded on the shell support plate  18 . The end of tubes are expanded to seal in the tube sheet  32 . Water passage can be used side by side also. A baffle plate  46  is disposed at the leftmost portion of the cylindrical shell  16 . The baffle plate  46  overlies the uppermost layer of tubes of the upper portion tubes  28 .  
      The baffle plate  46  is generally rectangular in shape and has opposed, spaced apart side margins  48  that extend to and are sealingly coupled with the interior margin of the cylindrical shell  16 . The distal end  50  of the baffle plate  46  extends rightward a portion of the length of the cylindrical shell  16 . Preferably, the distal end  50  is located between a ¼ and a ⅓ of the length of the cylindrical shell  16 . Accordingly, in an evaporator that is 9 to 16 feet long, the length dimension of the baffle plate  46  is preferably 3 to 4 feet. The proximal end  52  of the baffle plate  46  is sealingly coupled to the interior margin of the leftmost shell support plate  18 .  
      In operation, the interior cavity  22  of the shell assembly  12  is flooded with refrigerant. Chilled water is introduced to the lower portion tubes  26  of the tube bundle assembly  14  proximate the rightmost shell support plate  18 . The chilled water makes a first pass through the lower portion tubes  26  as indicated by the arrow  54 , cooling the water and evaporating the refrigerant. Upon passing through the tube ends  30  of the lower portion tubes  26 , the water passes around the proximal end  42  of the water pass vane  36  through the water passage  44 , as indicated by the arrow  58 . The now somewhat warmed water enters the tube ends  30  of the upper portion tubes  28  and makes a second pass through the upper portion tubes  28  as indicated by the arrow  58  and is then extracted from the evaporator  10 . This pass further cools the water. The baffle plate  48  acts to keep the water below the baffle plate  48  in its transition from the lower portion tubes  26  to the upper portion tubes  28 . Refrigerant vapor passes leftward through the upper portion of the interior cavity  22  and is drawn out of the suction nozzle  24 .  
      The above disclosure is not intended as limiting. Those skilled in the art will readily observe that numerous modifications and alterations of the device may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the restrictions of the appended claims.