Abstract:
A cryogen cylinder includes a tank having a side wall defining a chamber for containing a cryogenic substance in the tank; and a plate assembly mounted in the chamber, the plate assembly constructed and arranged to provide a passageway for vapor from the cryogenic substance to be introduced into the passageway.

Description:
BACKGROUND 
       [0001]    The present embodiment relates to heat transfer cryogen storage for refrigerating spaces such as for example spaces that are in transit. 
         [0002]    In transit refrigeration (ITR) systems are known and may include cryogenic ITR systems which use fin tube heat exchangers for liquid nitrogen and carbon dioxide chilled or frozen applications, or a snow bunker for solid CO 2  snow (or dry ice) chilled or frozen applications. Such known systems experience problems of safety, temperature control, cool down rates, dual temperature zone control, efficiency and fouling. For example, fins of a fin tube heat exchanger must be used in conjunction with a defrost cycle and related components in order to defrost frozen condensate which accumulates on the fins. Such defrost cycle requires downtime of the heat exchanger and therefore additional cost to such system, which is undesirable. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0003]    For a more complete understanding of the present embodiment, reference may be had to the following drawing figures taken in conjunction with the description of the embodiment, of which: 
           [0004]      FIG. 1  shows a side cross-section view of a cryogen cylinder embodiment for use to chill or freeze products such as food products for example; 
           [0005]      FIG. 2  shows an end view of the embodiment of  FIG. 1  taken along line  2 - 2  in  FIG. 1 ; 
           [0006]      FIG. 3  shows a top plan view of the embodiment of  FIG. 1  taken along line  3 - 3  in  FIG. 1 ; and 
           [0007]      FIG. 4  shows a top perspective isometric view of the embodiment in  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0008]    Referring to  FIGS. 1-4 , a cryogen cylinder of the present embodiment is shown generally at  10  and includes a tank  12  or pressure vessel having a side wall  14  which may be insulated. Such insulation is disposed substantially across the entire sidewall  14  and may be vacuum jacketed or formed of foam or polystyrene material. The side wall  14  defines a compartment having a space  16  therein for holding a cryogenic substance of either liquid nitrogen (N 2 ) or liquid carbon dioxide (CO 2 ) shown generally at  18 . A surface of the liquid cryogen  18  is shown generally at  20 . The liquid cryogen  18  will inevitably boil off as explained below and therefore, vapor  24  resulting from boil off of the liquid cryogen is exhausted from an atmosphere  22  above the surface  20  of the liquid cryogen  18  through a vent pipe  26  or outlet which vents the cryogen vapor to atmosphere external to the tank  12 . An inlet pipe  28  or inlet is provided above the surface  20  at one end of the tank  12  to replenish the liquid cryogen  18  in the space  16 . 
         [0009]    The tank  12  can be mounted or disposed for use with ITR systems. By way of example, the tank  12  may have dimensions of 1-3 meters in length with a volume of 300-1000 liters, although a tank having other volumes may be used. 
         [0010]    The tank  12  includes a labyrinth or alternating passageway formed by a plate assembly which can include at least one plate or alternatively a plurality of plates  30 A- 30 D arranged in the space  16  above the surface  20  of the liquid cryogen  18 . The plates  30 A- 30 D may be manufactured from stainless steel. The construction and arrangement of the plates  30 A- 30 D provides a continuous alternating or sinuous passageway  32  such that the cryogen vapor  24  from the liquid cryogen  18  is directed along the passageway  32  provided by the plates  30 A- 30 D and guided upward in a flow as indicated generally by arrows  34  proceeding along the passageway to the vent pipe  26 . 
         [0011]    The plates  30 A- 30 D do not contact the liquid cryogen  18 , but instead are disposed in the atmosphere  22  of the space  16  above the surface  20  of the liquid cryogen. The plurality of plates  30 A- 30 D create the passageway  32  to provide for increased residence time of the cryogen vapor  24  in the passageway to provide for the necessary chilling. 
         [0012]    Referring to  FIGS. 1 and 3 , the plates  30 A- 30 D are arranged in a staggered relationship in the space  16  to provide the passageway  32  as described below. A lowermost one of the plates  30 A is connected at three of its sides to an inner surface  36  of the tank  12 , while one side  38  of said plate  30 A extends toward but does not contact the opposed portion of the inner surface  36  of the tank  12 , as shown in  FIGS. 1 and 4 . An opening  40  is provided between the side  38  of the plate  30 A and the inner surface  36  of the tank  12 . The next plate  30 B positioned directly above and spaced apart from the lowermost plate  30 A has three of its sides attached to the inner surface  36  such that one side  42  is attached to the inner surface  36  at a position above the opening  40 , thereby providing entrance to a first portion  44  of the passageway  32 . A side  48  of plate  30 B extends toward but does not contact the opposed portion of the inner surface  36  of the tank  12  as shown in  FIG. 1 . This arrangement provides for a space  46  between the side  48  of the plate  30 B and the inner surface  36  of the tank  12 . The next successive plate upward,  30 C, is affixed to the inner surface  36  similar to the plate  30 A, and has a side  50  extending to but not contacting the inner surface  36  thereby, providing another opening  52  for the gas flow to continue along the passageway  32 . The plate  30 D is the uppermost plate in the space  16  and is mounted to the inner surface  36  similar to the plate  30 B, the plate  30 D having a side  54  extending to but not contacting the inner surface  36 , thereby providing an opening  56  through which the gas flow is directed to the vent pipe  26 . 
         [0013]    Each one of the plates  30 A- 30 D is spaced apart from the plate below it, with the plate  30 D, the uppermost plate in the space  16 , being spaced apart from the inner surface  36  at the roof of the side wall  14 . Each of the plates  30 A- 30 D has its corresponding three sides connected to, such as by welding, the inner surface  36  of the tank  12 , while one side of each one of the plates extends through the space  16  of the tank  12 , but does not contact the inner surface  36  at an opposed side of the tank  12 . The alternating or staggered arrangement of the plates  30 A- 30 D with respect to each other provides for the passageway  32  and the openings  40 , 46 , 52 , 56  to join all the pathways between the plates  30 A- 30 D to form the passageway  32 , in which the cryogen vapor has a residence time to reach a desired temperature for use after it is exhausted from the tank at the vent pipe  26 . 
         [0014]    It will be understood that the embodiments described herein are merely exemplary, and that one skilled in the art may make variations and modifications without departing from the spirit and scope of the invention. All such variations and modifications are intended to be included within the scope of the invention as described and claimed herein. Further, all embodiments disclosed are not necessarily in the alternative, as various embodiments of the invention may be combined to provide the desired result.