Ejector refrigeration circuit

1. A method of operating an ejector refrigeration circuit with

at least two controllable ejectors connected in parallel and respectively comprising a controllable motive nozzle, a primary high pressure input port forming an inlet to the controllable motive nozzle, a secondary low pressure input port and an output port,

a heat rejecting heat exchanger/gas cooler having an inlet side and an outlet side, the outlet side of the heat rejecting heat exchanger/gas cooler being fluidly connected to the primary high pressure input ports of the ejectors;

a receiver, having a liquid outlet, a gas outlet and an inlet, which is fluidly connected to the outlet ports of the controllable ejectors; and

at least one compressor having an inlet side and an outlet side, the inlet side of the at least one compressor being fluidly connected to the gas outlet of the receiver, and the outlet side of the at least one compressor being fluidly connected to the inlet side of the heat rejecting heat exchanger/gas cooler;

wherein the method comprises:

a) operating a first ejector of the at least two controllable ejectors by controlling the opening degree of its primary high pressure input port until the maximum efficiency of said first ejector has been reached or the actual refrigeration demands are met;

b) operating a second ejector of the at least two controllable ejectors by gradually opening its primary high pressure input port for increasing the refrigeration capacity of the ejector refrigeration circuit in case the actual refrigeration demands are not met by operating the first ejector alone.

2. The method of claim 1 , wherein the ejector refrigeration circuit further comprises:

at least one refrigeration expansion device having an inlet side, which is fluidly connected to the liquid outlet of the receiver, and an outlet side; and

at least one refrigeration evaporator fluidly connected between the outlet side of the at least one refrigeration expansion device and the secondary low pressure input ports of the controllable ejectors.

3. The method of claim 1 , wherein the method includes operating at least one of the controllable ejectors with its secondary low pressure input port being closed.

4. The method of claim 3 including opening the secondary low pressure input port of the at least one controllable ejector which has been operated with its secondary low pressure input port being closed.

5. The method of claim 4 wherein the secondary low pressure input port is opened gradually.

6. The method of claim 1 including closing the secondary low pressure input port of the first ejector.

7. The method of claim 1 including closing the primary high pressure input port of the first ejector.

8. The method of claim 7 including closing the secondary low pressure input port of the first ejector.

9. The method of claim 1 including using carbon dioxide as refrigerant.

10. An ejector refrigeration circuit, which is configured for circulating a refrigerant and comprises:

at least two controllable ejectors connected in parallel and respectively comprising a controllable motive nozzle, a primary high pressure input port forming an inlet to the controllable motive nozzle, a secondary low pressure input port and an output port;

a heat rejecting heat exchanger/gas cooler having an inlet side and an outlet side, the outlet side of the heat rejecting heat exchanger/gas cooler being fluidly connected to the primary high pressure input ports of the ejectors;

a receiver, having a liquid outlet, a gas outlet and an inlet, which is fluidly connected to the outlet ports of the controllable ejectors;

at least one compressor having an inlet side and an outlet side, the inlet side of the at least one compressor being fluidly connected to the gas outlet of the receiver, and the outlet side of the at least one compressor being fluidly connected to the inlet side of the heat rejecting heat exchanger/gas cooler; and

a control unit, which is configured for operating the ejector refrigeration circuit employing a method comprising:

a) operating a first ejector of the at least two controllable ejectors by controlling the opening degree of its high pressure port until the maximum efficiency of said first ejector has been reached or the actual refrigeration demands are met;

b) operating a second ejector of the at least two controllable ejectors by gradually opening its primary high pressure input port for increasing the refrigeration capacity of the ejector refrigeration circuit in case the actual refrigeration demands are not met by operating the first ejector alone.

11. The ejector refrigeration circuit of claim 10 further comprising:

at least one refrigeration expansion device having an inlet side, which is fluidly connected to the liquid outlet of the receiver, and outlet side; and

at least one refrigeration evaporator fluidly connected between the outlet side of the at least one refrigeration expansion device and the secondary low pressure input ports of the controllable ejectors.

12. The ejector refrigeration circuit of claim 10 , wherein the controllable ejectors are provided with the same capacity.

13. The ejector refrigeration circuit of claim 10 , wherein the controllable ejectors are provided with different capacities.

14. The ejector refrigeration circuit of claim 10 , wherein a controllable valve is provided upstream the secondary low pressure input port of at least one/each of the controllable ejectors.

15. The ejector refrigeration circuit of claim 10 , wherein at least one sensor, which is configured for measuring the pressure and/or the temperature of the refrigerant, is provided in at least one of a high pressure input line fluidly connected to the primary high pressure input ports, a low pressure input line fluidly connected to the secondary low pressure input ports and an ejector output line fluidly connected to the output ports of the controllable ejectors, respectively.

16. The ejector refrigeration circuit of claim 10 , wherein at least one service valve is provided upstream of the controllable ejectors' primary high pressure input ports.

17. The ejector refrigeration circuit of claim 16 further comprising at least one low temperature circuit which is connected between the liquid outlet of the receiver and the inlet side of the at least one compressor and comprises in the direction of flow of the refrigerant:

at least one low temperature expansion device;

at least one low temperature evaporator; and

at least one low temperature compressor.

18. The ejector refrigeration circuit of claim 10 , wherein the refrigerant comprises carbon dioxide.