Control of supercritical refrigeration system

A refrigeration system, comprising:

• a refrigerant circuit that, in order to perform a vapor compression supercritical refrigeration cycle, includes
• a compression mechanism,
• a heat source side heat exchanger,
• an expansion mechanism, and
• a utilization side heat exchanger, wherein
• the expansion mechanism includes, for two-stage compression of refrigerant in the refrigerant circuit,
• a high pressure side throttle mechanism variable in the amount of throttling, and
• a low pressure side throttle mechanism variable in the amount of throttling;
• and
• an outlet temperature controller configured to
• for each temperature of a medium exchanging heat with refrigerant in the utilization side heat exchanger functioning as a heat dissipation unit, at the inlet of the utilization side heat exchanger, store a relationship between the temperature of refrigerant at the outlet of the utilization side heat exchanger and the pressure of high pressure refrigerant in the refrigerant circuit,
• for each temperature of the medium at the inlet of the utilization side heat exchanger, store a relationship between a COP and the temperature of refrigerant at the outlet of the utilization side heat exchanger and a relationship between the COP and the pressure of the high pressure refrigerant in the refrigerant circuit, and
• derive, in a heating operation mode of the refrigerant circuit, a target value, providing a maximum COP, for the temperature of refrigerant at the outlet of the utilization side heat exchanger based on
• i) the temperature of the medium at the inlet of the utilization side heat exchanger and
• ii) a preset pressure value for the pressure of high pressure refrigerant in the refrigerant circuit, and the outlet temperature controller further configured to adjust the amount of throttling of the expansion mechanism so that the outlet refrigerant temperature is controlled to the target value.

A refrigeration system, comprising:

• a refrigerant circuit that, in order to perform a vapor compression supercritical refrigeration cycle, includes
• a compression mechanism,
• a heat source side heat exchanger,
• an expansion mechanism, and
• a plurality of utilization side heat exchangers connected in parallel with each other, wherein
• the expansion mechanism includes, for two-stage compression of refrigerant in the refrigerant circuit,
• a heat source side throttle mechanism variable in the amount of throttling and associated with the heat source side heat exchanger, and
• a plurality of utilization side throttle mechanisms variable in the amount of throttling and associated respectively with the plurality of utilization side heat exchangers;
• a high pressure controller configured to
• for each temperature of a medium exchanging heat with refrigerant in the heat source side heat exchanger functioning as a heat dissipation unit, at the inlet of the heat source side heat exchanger, store a relationship between the temperature of refrigerant at the outlet of the heat source side heat exchanger and the pressure of high pressure refrigerant in the refrigerant circuit, and, for each temperature of the medium at the inlet of the heat source side heat exchanger, store a relationship between a COP and the temperature of refrigerant at the outlet of the heat source side heat exchanger and a relationship between the COP and the pressure of the high pressure refrigerant in the refrigerant circuit,
• for each temperature of a medium exchanging heat with refrigerant in the utilization side heat exchanger functioning as a heat dissipation unit, at the inlet of the utilization side heat exchanger, store a relationship between the temperature of refrigerant at the outlet of the utilization side heat exchanger and the pressure of the high pressure refrigerant in the refrigerant circuit, and, for each temperature of the medium at the inlet of the utilization side heat exchanger, store a relationship between the COP and the temperature of refrigerant at the outlet of the utilization side heat exchanger and a relationship between the COP and the pressure of the high pressure refrigerant in the refrigerant circuit, and
• derive, in a cooling operation mode of the refrigerant circuit, a target value, providing a maximum COP, for the pressure of high pressure refrigerant in the refrigerant circuit based on
• i) the temperature of the refrigerant at the outlet of the heat source side heat exchanger, and
• ii) the temperature of the medium at the inlet of the heat source side heat exchanger;
• and the high pressure controller further configured to adjust the amount of throttling of the expansion mechanism so that the high pressure refrigerant pressure is controlled to the target value;
• and
• an outlet temperature controller configured to derive, in a heating operation mode of the refrigerant circuit, a target value, providing a maximum COP, for the temperature of refrigerant at the outlet of the utilization side heat exchanger based on
• i) the temperature of the medium at the inlet of the utilization side heat exchanger and
• ii) a preset pressure value for the pressure of high pressure refrigerant in the refrigerant circuit, and the outlet temperature controller is configured to adjust the amount of throttling of the expansion mechanism so that the outlet refrigerant temperature is controlled to the target value.