Heat exchange type cascade refrigeration system, refrigeration method, cryogenic method and refrigeration equipment

The invention relates to the technical field of refrigerating systems, and provides an interchanging heat type cascade refrigerating system which comprises a freezing and refrigerating subsystem, a refrigerating and refrigerating subsystem, a refrigerating and refrigerating subsystem and a refrigerating and refrigerating subsystem. The refrigerating and freezing condenser is connected with the refrigerating evaporator and the freezing evaporator in parallel; a refrigeration air return pipe of the refrigeration evaporator and a freezing air return pipe of the freezing evaporator are connected with an air suction port of the first compressor; the variable temperature subsystem is provided with a second compressor, a heat exchange condenser and a variable temperature evaporator; the heat exchange condenser is in heat exchange connection with the refrigeration evaporator, and the refrigerant outlet pipe is in heat exchange connection with the freezing air return pipe. Therefore, through heat exchange of the two s