Ejector

1. A refrigerant ejector for a refrigerant system comprising:

a primary inlet;

a secondary inlet;

an outlet;

a primary flowpath from the primary inlet to the outlet;

a secondary flowpath from the secondary inlet to the outlet;

a motive nozzle surrounding the primary flowpath upstream of a junction with the secondary flowpath and having: a throat; and an exit; and

means for varying an effective area of the exit and an effective area of the throat oppositely to each other.

2. The refrigerant ejector of claim 1 wherein:

the means is means for simultaneously varying the effective area of the exit and the effective area of the throat.

3. The refrigerant ejector of claim 1 wherein:

the means comprises a needle mounted for reciprocal movement along the primary flowpath between a first position and a second position and, in at least one position, spanning at least from the throat to the exit.

4. A method for operating the refrigerant ejector of claim 1 , the method comprising:

passing a primary flow through the primary inlet;

passing a secondary flow through the secondary inlet to merge with the primary flow and exit the outlet; and

varying the effective area of the exit simultaneously with oppositely varying the effective area of the throat.

5. The method of claim 4 wherein:

the varying the effective area of the exit and the varying the effective area of the throat are performed by a respective downstream needle and upstream needle actuated independently.

6. The method of claim 4 wherein:

the varying comprises axially shifting a needle mounted for reciprocal movement along the primary flowpath between a first position and a second position and, in at least one position, spanning at least from the throat to the exit.

7. The refrigerant ejector of claim 1 , wherein the means comprises:

a first needle; and a second needle.

8. The refrigerant ejector of claim 7 , wherein the means further comprises:

a first actuator for controlling movement of the first needle; and

a second actuator for controlling movement of the second needle.

9. The refrigerant ejector of claim 7 , wherein:

the first needle has a downstream tip; and

the second needle has an upstream top.

10. The refrigerant ejector of claim 7 , wherein:

the first needle is positioned to vary the effective area of the throat; and

the second needle is positioned to vary the effective area of the exit.

11. The refrigerant ejector of claim 1 , wherein:

the means provides independent varying of the effective area of the exit and the effective area of the throat so as to also allow varying non-oppositely to each other.

12. The refrigerant ejector of claim 1 , wherein:

the means comprises a needle;

the means provides, over a first portion of a range of motion of the needle, said varying the effective area of the exit and the effective area of the throat oppositely to each other; and

the means provides, over a second portion of a range of motion of the needle, said varying the effective area of the exit and the effective area of the throat non-oppositely to each other.

13. The refrigerant ejector of claim 1 , wherein:

the means comprises a needle first downstream convergent portion and a needle second downstream divergent portion.

14. The refrigerant ejector of claim 13 , wherein:

the means comprises a needle third downstream convergent portion upstream of the second downstream divergent portion.

15. The refrigerant ejector of claim 13 , wherein:

the needle first downstream convergent portion and the needle second downstream divergent portion are on a single needle.

16. The refrigerant ejector of claim 1 , wherein:

the motive nozzle has a divergent section between the throat and the exit.

17. The refrigerant ejector of claim 1 wherein:

the junction is at the exit.

18. The refrigerant ejector of claim 1 further comprising:

a mixer upstream of the outlet.

19. The refrigerant ejector of claim 18 further comprising;

a diffuser between the mixer and the outlet.

20. The refrigerant ejector of claim 1 further comprising:

a diffuser upstream of the outlet.

21. A refrigeration system comprising;

a compressor;

a first heat exchanger downstream of the compressor along a refrigerant flowpath;

the refrigerant ejector of claim 1 having the primary net and the outlet along the flowpath; and

a second heat exchanger along a secondary loop of the flowpath passing to the secondary net of the ejector.

22. The method of claim 4 further comprising:

recovering pressure in a diffuser.