A modulator in a coolant recirculation line for a refrigerating apparatus. The modulator is used for storing an excess amount of the coolant recirculated in the system. The modulator has a space extending vertically, upward and a bottom end connected to the recirculating line at a position downstream of a condenser, in such a manner that only a part of the coolant passed through the condenser is introduced into the modulator to compensate for variations in the amount of coolant needed for recirculation in the system. The modulator can be arranged in the middle of the heat exchanger, and defines therein a boundary between the liquid phase and the gas phase, for a separation of the gas from the coolant, so that the portion of the heat exchanger downstream of the modulator can operate as a super cooler.