Flash tank design and control for heat pumps

1. In a heat pump system of the type which re-circulates refrigerant through a fluid circuit between a first heat exchanger and a second heat exchanger including a compressor coupled to the fluid circuit, a vapor injection system comprising a vessel fluidly coupled to the first and second heat exchangers and to a vapor injection port of the compressor and a control device operable to control vapor from said vessel to said compressor based on an outdoor ambient temperature, said vessel operable as a receiver in a cooling mode of the heat pump system and operable as a flash tank in a heating mode of the heat pump system, said vessel including a first port fluidly coupled to an entire interior volume of said vessel and to said first heat exchanger, said first port receiving fluid from said first heat exchanger and operable as an inlet in said heating mode and as an outlet in said cooling mode, said control device in a fully open position allowing said vapor from said vessel to said compressor when said outdoor ambient temperature is less than about twenty-five degrees Fahrenheit.

2. The vapor injection system of claim 1 , wherein said control device is a solenoid valve.

3. The vapor injection system of claim 1 , wherein said control device is controlled based on at least one of, a compressor discharge temperature, a thermostat stage demand, and a reversing valve signal.

4. The vapor injection system of claim 1 , wherein said vessel includes a second port receiving fluid from said second heat exchanger, said second port operable as an inlet in said cooling mode and as an outlet in said heating mode.

5. The vapor injection system of claim 4 , further comprising an expansion device disposed proximate to said second port.

6. The vapor injection system of claim 4 , further comprising a first control device disposed between said second port and said second heat exchanger.

7. The vapor injection system of claim 6 , wherein said first control device is selected from the group comprising: a thermal expansion valve, an electronic expansion valve, a fixed orifice, or a single, bi-directional electronic expansion valve.

8. The vapor injection system of claim 6 , further comprising a check valve disposed between said second port and said second heat exchanger and operable to allow fluid to bypass said first control device in said cooling mode and direct said fluid into said first control device in said heating mode.

9. The vapor injection system of claim 6 , further comprising a second control device disposed between said second port and said second heat exchanger.

10. The vapor injection system of claim 9 , wherein said second control device is selected from the group comprising: a thermal expansion valve, an electronic expansion valve, a fixed orifice, or a single, bi-directional electronic expansion valve.

11. The vapor injection system of claim 9 , further comprising a check valve disposed between said second port and said second heat exchanger and operable to allow fluid to bypass said second control device in said heating mode and direct said fluid into said second control device in said cooling mode.

12. The vapor injection system of claim 1 , further comprising an expansion device disposed proximate to said first port.

13. The vapor injection system of claim 1 , further comprising a third control device disposed between said first port and said first heat exchanger.

14. The vapor injection system of claim 13 , wherein said third control device is one of a thermal expansion valve, an electronic expansion valve, a fixed orifice, or a single, bi-directional electronic expansion valve.

15. The vapor injection system of claim 13 , further comprising a check valve disposed between said first port and said first heat exchanger and operable to allow fluid to bypass said third control device in said cooling mode and direct said fluid into said third control device in said heating mode.

16. The vapor injection system of claim 13 , further comprising a fourth control device disposed between said first port and said first heat exchanger.

17. The vapor injection system of claim 16 , wherein said fourth control device is selected from the group comprising: a thermal expansion valve, an electronic expansion valve, a fixed orifice, or a single, bi-directional electronic expansion valve.

18. The vapor injection system of claim 16 , further comprising a check valve disposed between said first port and said first heat exchanger and operable to allow fluid to bypass said fourth control device in said heating mode and direct said fluid into said fourth control device in said cooling mode.

19. The vapor injection system of claim 1 , wherein said control device is disposed on said vapor injection line and prevents fluid communication between said vapor injection line and said compressor in said cooling mode.

20. The vapor injection system of claim 1 , wherein said control device is in a closed position restricting said vapor from said vessel to said compressor when said outdoor ambient temperature is above about forty-five degrees Fahrenheit.

21. The vapor injection system of claim 1 , wherein said control device is pulse-width modulated when said outdoor ambient temperature is between about twenty-five degrees Fahrenheit and about forty-five degrees Fahrenheit.

22. In a heat pump system of the type which re-circulates refrigerant through a fluid circuit between a first heat exchanger and a second heat exchanger including a compressor coupled to the fluid circuit, a vapor injection system comprising a vessel fluidly coupled to the first and second heat exchangers and to a vapor injection port of the compressor and a control device operable to control vapor from said vessel to said compressor based on an outdoor ambient temperature, said vessel operable as a receiver in a cooling mode of the heat pump system and operable as a flash tank in a heating mode of the heat pump system, said vessel including a first port fluidly coupled to an entire interior volume of said vessel and to said first heat exchanger, said first port receiving fluid from said first heat exchanger and operable as an inlet in said heating mode and as an outlet in said cooling mode, said control device in a closed position restricting said vapor from said vessel to said compressor when said outdoor ambient temperature is above about forty-five degrees Fahrenheit.

23. The vapor injection system of claim 22 , wherein said control device is a solenoid valve.

24. The vapor injection system of claim 22 , wherein said control device is controlled based on at least one of a compressor discharge temperature, a thermostat stage demand, and a reversing valve signal.

25. The vapor injection system of claim 22 , wherein said vessel includes a second port receiving fluid from said second heat exchanger, said second port operable as an inlet in said cooling mode and as an outlet in said heating mode.

26. The vapor injection system of claim 25 , further comprising an expansion device disposed proximate to said second port.

27. The vapor injection system of claim 25 , further comprising a first control device disposed between said second port and said second heat exchanger.

28. The vapor injection system of claim 27 , wherein said first control device is selected from the group comprising: a thermal expansion valve, an electronic expansion valve, a fixed orifice, or a single, bi-directional electronic expansion valve.

29. The vapor injection system of claim 27 , further comprising a check valve disposed between said second port and said second heat exchanger and operable to allow fluid to bypass said first control device in said cooling mode and direct said fluid into said first control device in said heating mode.

30. The vapor injection system of claim 27 , further comprising a second control device disposed between said second port and said second heat exchanger.

31. The vapor injection system of claim 30 , wherein said second control device is selected from the group comprising: a thermal expansion valve, an electronic expansion valve, a fixed orifice, or a single, bi-directional electronic expansion valve.

32. The vapor injection system of claim 30 , further comprising a check valve disposed between said second port and said second heat exchanger and operable to allow fluid to bypass said second control device in said heating mode and direct said fluid into said second control device in said cooling mode.

33. The vapor injection system of claim 22 , further comprising an expansion device disposed proximate to said first port.

34. The vapor injection system of claim 22 , further comprising a third control device disposed between said first port and said first heat exchanger.

35. The vapor injection system of claim 34 , wherein said third control device is one of a thermal expansion valve, an electronic expansion valve, a fixed orifice, or a single, bi-directional electronic expansion valve.

36. The vapor injection system of claim 34 , further comprising a check valve disposed between said first port and said first heat exchanger and operable to allow fluid to bypass said third control device in said cooling mode and direct said fluid into said third control device in said heating mode.

37. The vapor injection system of claim 34 , further comprising a fourth control device disposed between said first port and said first heat exchanger.

38. The vapor injection system of claim 37 , wherein said fourth control device is selected from the group comprising: a thermal expansion valve, an electronic expansion valve, a fixed orifice, or a single, bi-directional electronic expansion valve.

39. The vapor injection system of claim 37 , further comprising a check valve disposed between said first port and said first heat exchanger and operable to allow fluid to bypass said fourth control device in said heating mode and direct said fluid into said fourth control device in said cooling mode.

40. The vapor injection system of claim 22 , wherein said control device is disposed on said vapor injection line and prevents fluid communication between said vapor injection line and said compressor in said cooling mode.

41. The vapor injection system of claim 22 , wherein said control device is pulse-width modulated when said outdoor ambient temperature is between about twenty-five degrees Fahrenheit and about forty-five degrees Fahrenheit.