Supermarket cold chain system

The utility model provides a supermarket cold chain system which comprises a high-temperature cold storage system, an intermediate-temperature cold storage system and a low-temperature cold storage system. A carbon dioxide direct expansion system is adopted as the low-temperature cold storage system which comprises a carbon dioxide gas compressor and a low-temperature evaporator. The intermediate-temperature cold storage system comprises an intermediate-temperature evaporator and a liquid storage tank. The high-temperature cold storage system comprises a high-temperature compressor, a condenser and a liquid supply/gas return plate type heat exchanger. A water cooling condensing system is adopted as the high-temperature cold storage system, a cascade plate type heat exchanger is arranged between the high-temperature cold storage system and the intermediate-temperature cold storage system, the intermediate-temperature cold storage system is further internally provided with a carbon diode pump which is communicated with the cascade plate type heat exchanger and the liquid storage tank. According to the supermarket cold chain system, a cascade type system and a pumping system are combined, the carbon dioxide direct expansion system is adopted as the low-temperature cold storage system, indirect cooling circulation for pumping carbon dioxide is adopted in the intermediate-temperature cold storage system, meanwhile, HFC type refrigerants in a cascade high-temperature-level system can only circulate in a machine room due to the water cooling condensing system, and the use amount of the HFC type refrigerants is greatly reduced.