IFV device suitable for phase change refrigerant

The IFV device is characterized in that a heat exchange cavity E1 section and a heat exchange cavity E2 section are arranged in a first shell, a heat exchange cavity E3 section is arranged in a second shell, the heat exchange cavity E1 section and the heat exchange cavity E2 section in the first shell are communicated through an E1/E2 shell pass, and a carbon dioxide liquefaction tube bundle and an LNG gasification tube bundle are arranged in the heat exchange cavity E1 section and the heat exchange cavity E2 section respectively; the LNG gasification tube bundle is located above the carbon dioxide liquefaction tube bundle, and an E3 shell pass in the heat exchange cavity E3 section communicates with the carbon dioxide liquefaction tube bundle; and a liquid collection bag is arranged between the first shell and the second shell. LNG cold energy is recycled in a stepped mode through intermediate media of a first-stage refrigerant and a second-stage refrigerant, cold energy of low-temperature NG at a shallow co