Dry ice rail car cooling system

In an insulated railcar or container having side walls, end walls, a floor, and an exhaust vent for maintaining cargo in a refrigerated condition by the use of carbon dioxide as an expendable refrigerant, wherein liquid or slush carbon dioxide is injected into a carbon dioxide bunker forming snow which remains in said bunker and car and vapor which exists said bunker through a vent(s) into a cargo compartment loaded with cargo, said cargo being arranged so that an open space is formed between said cargo and the bottom of said bunker and said vents, and then by said cargo and under said cargo to an exhaust vent to the outside wherein the improvement comprises a heat conducting material in thermal communication with said snow, one or more convectors in thermal communication with said heat conducting material, the thermal convector(s) being located near the side and or end walls of the railcar or container, a layer of insulation positioned in a bottom area of the bunker between the heat conducting material and the cargo volume free of vents and convectors thereby reducing the cooling by sublimation of said snow to said cargo directly below the snow.

In an insulated railcar or container, each having a pair of opposed side walls, and a pair of opposed end walls, for maintaining cargo in a near 0.degree. F. or lower temperature condition by use of solid carbon dioxide as an expendable refrigerant wherein liquid carbon dioxide is injected into a bunker located above a cargo compartment, creating vapor and solid phase (snow) carbon dioxide, the vapor created during such injection cooling portion of both the cargo and the cargo compartment prior to vent to the atmosphere, and said carbon dioxide subsequently cooling said cargo compartment, wherein the improvement comprises heat conducting material in thermal communication with said snow, convectors located near to the side and or end walls of the railcar or container, the convectors being in thermal communication with the heat conducting material, and a layer of insulation in a bottom area of the bunker between the heat conducting material and the cargo volume free of vents and convectors thereby reducing the cooling by sublimation of said snow to said cargo in the near 0.degree. F. or lower temperature condition positioned directly below the snow.

In an insulated railroad car or other cargo container for maintaining cargo in a near 0.degree. F. or lower condition by the use of carbon dioxide as an expendable refrigerant, the car or container having a top, a pair of opposed side walls, and a bunker having an insulated floor and vents for carbon dioxide vapor, the bunker positioned beneath the top and above a cargo volume, a manifold pipe positioned so as to provide a supply of carbon dioxide snow on the floor of the bunker, the bunker floor providing at least in part, a ceiling for the cargo volume, the improvement comprising said bunker vents positioned so that at least an opening in one vent communicates with a lower portion of the bunker and at least an opening in another vent communicates with a portion of the bunker above the lower portion of the bunker, whereby circulation of carbon dioxide vapor between said cargo volume and said bunker is enhanced because of height differences in positioning of the openings of the bunker vents and the cargo is maintained in a uniformly refrigerated state.

The method of maintaining cargo in a near 0.degree. F. or lower condition in an insulated railcar or container by use of carbon dioxide as an expendable refrigerant, wherein liquid or slush carbon dioxide is injected into a carbon dioxide bunker forming snow which remains in said bunker and vapor which exits said bunker through a vent(s) into a cargo compartment loaded with cargo, said cargo being arranged so that an open space is formed between said cargo and the bottom of said bunker and said vents and then said vapor passes by said cargo and under said cargo to an exhaust vent to the outside and said snow subsequently providing controlled uniform cooling from its sublimation to said cargo area substantially by controlling the quantity and direction of flow of the vapor from the cargo compartment rising into said bunker where it is cooled by contact with the snow and controlling the quantity and direction of flow of the vapor in the return of the cooled vapor uniformly to said cargo compartment through the vents.