Disclosed are cascaded refrigeration systems, comprising: a plurality of refrigeration units, each refrigeration unit containing a first refrigeration circuit, each first refrigeration circuit comprising an evaporator and a heat exchanger, and a second refrigeration circuit; wherein each first circuit heat exchanger is arranged to transfer heat energy between its respective first refrigeration circuit and the second refrigeration circuit.

This cooling device is equipped with a tank, a pump, an evaporator, and a condenser. The gas phase portion of the tank is filled with a filler gas and is equipped with a volume-changing unit. The volume-changing unit is configured to adjust an evaporation temperature of the refrigerant by changing a pressure of the refrigerant, which is achieved by changing a volume of the gas phase portion to change a pressure of the filler gas.