Overlapping refrigeration system

Provided is a freezing (b) (b) the system of overlapping, including high temperature level circulation circuit, low temperature level circulation circuit, with the evaporation-condensation ware that high temperature level circulation circuit is connected with low temperature level circulation circuit, the evaporation-condensation ware includes the low temperature level condenser that lies in one side, lies in the high temperature level evaporimeter of opposite side, and low temperature level condenser is connected in low temperature level circulation circuit, and high temperature level evaporimeter is connected in high temperature level circulation circuit, is connected with the precooler among the low temperature level circulation circuit, and the precooler lies in before the evaporation-condensation ware the utility model discloses be provided with the precooler in low temperature level circulation system and before the evaporation-condensation ware, can make low temperature level refrigerant cool off the uniform temperature like this before the low temperature level condenser that gets into the evaporation-condensation ware to reduce the difference in temperature between high temperature level evaporimeter and the low temperature level condenser, increase the reliability, increase of service life, and the difference in temperature is more little, and irreversible heat loss is more little, also can improve heat exchange efficiency, improves the performance of unit (B, )