Patent Application
20130008185
The present embodiment relates to heat transfer cryogen storage for refrigerating spaces such as for example spaces that are in transit.
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 CO2 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.
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:
Referring to
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.
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 30A-30D arranged in the space 16 above the surface 20 of the liquid cryogen 18. The plates 30A-30D may be manufactured from stainless steel. The construction and arrangement of the plates 30A-30D 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 30A-30D and guided upward in a flow as indicated generally by arrows 34 proceeding along the passageway to the vent pipe 26.
The plates 30A-30D 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 30A-30D create the passageway 32 to provide for increased residence time of the cryogen vapor 24 in the passageway to provide for the necessary chilling.
Referring to
Each one of the plates 30A-30D is spaced apart from the plate below it, with the plate 30D, 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 30A-30D 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 30A-30D 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 30A-30D 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.
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.
