Thermodynamic heat recovery without an additional thermodynamic circuit

1. A refrigerant circuit, comprising:

a compressor operable to compress a refrigerant;

an expansion valve;

an outdoor heat exchanger;

an indoor heat exchanger in a fresh air inlet to a conditioned space;

a recovery heat exchanger in an extracted air outlet from the conditioned space;

a reversing valve operable to control a direction of refrigerant flow between a cooling mode and a heating mode;

wherein the outdoor heat exchanger and the recovery heat exchanger have a reverse refrigerant flow direction in the heating mode relative to the cooling mode; and

the outdoor heat exchanger and the recovery heat exchanger are both in counter-current flow in one of the heating mode and the cooling mode and in co-current flow in the other one of the heating mode and the cooling mode.

2. The refrigerant circuit of claim 1 , wherein the refrigerant circuit comprises a first refrigerant line extending from the outdoor heat exchanger and the recovery heat exchanger;

a second refrigerant line extending from the outdoor heat exchanger to the recovery heat exchanger; and

a first valve located in the first refrigerant line, in a closed position the first valve directing the refrigerant through the recovery heat exchanger.

3. The refrigerant circuit of claim 2 , wherein the expansion valve is in communication with the first refrigerant line between the first valve and the recovery heat exchanger.

4. The refrigerant circuit of claim 3 , further comprising a second valve in the second refrigerant line.

5. The refrigerant circuit of claim 1 , wherein the recovery heat exchanger is located in the refrigerant circuit between the outdoor heat exchanger and the indoor heat exchanger and in the cooling mode the refrigerant flows from the compressor through the reversing valve to the outdoor heat exchanger, from the outdoor heat exchanger to the recovery heat exchanger, from the recovery heat exchanger through the expansion valve to the indoor heat exchanger, and from the indoor heat exchanger to the compressor.

6. The refrigerant circuit of claim 1 , wherein the recovery heat exchanger is located in the refrigerant circuit between the outdoor heat exchanger and the indoor heat exchanger and in the heating mode the refrigerant flows from the compressor through the reversing valve to the indoor heat exchanger, from the indoor heat exchanger through the expansion valve to the recovery heat exchanger, from the recovery heat exchanger to the outdoor heat exchanger, and from the outdoor heat exchanger to the compressor.

7. The refrigerant circuit of claim 1 , wherein in the heating mode the refrigerant flows from the compressor through the reversing valve to the indoor heat exchanger, from the indoor heat exchanger through the expansion valve to the outdoor heat exchanger, from the outdoor heat exchanger to the recovery heat exchanger, and from the recovery heat exchanger to the compressor.

8. A method, comprising:

operating a refrigerant circuit in a cooling mode or a heating mode to condition an indoor air in a conditioned space, the refrigerant circuit comprising a compressor operable to compress a refrigerant, an expansion valve, an outdoor heat exchanger, an indoor heat exchanger in a fresh air inlet to the conditioned space, and a recovery heat exchanger in an extracted air outlet from the conditioned space; and

recovering energy from the indoor air via the recovery heat exchanger.

9. The method of claim 8 , wherein the recovering energy comprises subcooling the refrigerant with the recovery heat exchanger.

10. The method of claim 8 , wherein the recovering energy comprises superheating the refrigerant with the recovery heat exchanger.

11. The method of claim 8 , further comprising, when operating in the cooling mode:

directing the refrigerant from the compressor to the outdoor heat exchanger;

removing heat from the refrigerant at the outdoor heat exchanger;

directing the refrigerant from the outdoor heat exchanger to the recovery heat exchanger;

removing heat from the refrigerant at the recovery heat exchanger;

directing the refrigerant from the recovery heat exchanger to the expansion valve and the indoor heat exchanger;

adding heat to the refrigerant at the indoor heat exchanger; and

directing the refrigerant from the indoor heat exchanger to the compressor.

12. The method of claim 11 , wherein the outdoor heat exchanger and the recovery heat exchanger have a reverse refrigerant flow direction in the heating mode relative to the cooling mode; and

the outdoor heat exchanger and the recovery heat exchanger are both in counter-current flow in one of the heating mode and the cooling mode and in co-current flow in the other one of the heating mode and the cooling mode.

13. The method of claim 11 , wherein the outdoor heat exchanger is in counter-current flow in the heating mode and the cooling mode.

14. The method of claim 8 , further comprising, when operating in the heating mode:

directing the refrigerant from the compressor to the indoor heat exchanger;

removing heat from the refrigerant at the indoor heat exchanger;

directing the refrigerant from the indoor heat exchanger through the expansion valve to the recovery heat exchanger;

adding heat to the refrigerant at the recovery heat exchanger;

directing the refrigerant from the recovery heat exchanger to the outdoor heat exchanger;

adding heat to the refrigerant at the outdoor heat exchanger; and

directing the refrigerant from the outdoor heat exchanger to the compressor.

15. The method of claim 8 , further comprising:

when operating in the cooling mode:

directing the refrigerant from the compressor to the outdoor heat exchanger;

removing heat from the refrigerant at the outdoor heat exchanger;

directing the refrigerant from the outdoor heat exchanger to the recovery heat exchanger;

removing heat from the refrigerant at the recovery heat exchanger;

directing the refrigerant from the recovery heat exchanger to the expansion valve and the indoor heat exchanger;

adding heat to the refrigerant at the indoor heat exchanger; and

directing the refrigerant from the indoor heat exchanger to the compressor; and

when operating in the heating mode:

directing the refrigerant from the compressor to the indoor heat exchanger;

removing heat from the refrigerant at the indoor heat exchanger;

directing the refrigerant from the indoor heat exchanger through the expansion valve to the recovery heat exchanger;

adding heat to the refrigerant at the recovery heat exchanger;

directing the refrigerant from the recovery heat exchanger to the outdoor heat exchanger;

adding heat to the refrigerant at the outdoor heat exchanger; and

directing the refrigerant from the outdoor heat exchanger to the compressor.

16. The method of claim 8 , further comprising, when operating in the heating mode:

directing the refrigerant from the compressor to the indoor heat exchanger;

removing heat from the refrigerant at the indoor heat exchanger;

directing the refrigerant from the indoor heat exchanger through the expansion valve to the outdoor heat exchanger;

adding heat to the refrigerant at the outdoor heat exchanger;

directing the refrigerant from the outdoor heat exchanger to the recovery heat exchanger;

adding heat to the refrigerant at the recovery heat exchanger; and

directing the refrigerant from the recovery heat exchanger to the compressor.

17. The method of claim 16 , wherein the indoor refrigerant is superheated by the indoor air at the recovery heat exchanger.

18. The method of claim 8 , further comprising:

when operating in the cooling mode:

directing the refrigerant from the compressor to the outdoor heat exchanger;

removing heat from the refrigerant at the outdoor heat exchanger;

directing the refrigerant from the outdoor heat exchanger to the recovery heat exchanger;

removing heat from the refrigerant at the recovery heat exchanger;

directing the refrigerant from the recovery heat exchanger to the expansion valve and the indoor heat exchanger;

adding heat to the refrigerant at the indoor heat exchanger; and

directing the refrigerant from the indoor heat exchanger to the compressor; and

when operating in the heating mode:

directing the refrigerant from the compressor to the indoor heat exchanger;

removing heat from the refrigerant at the indoor heat exchanger;

directing the refrigerant from the indoor heat exchanger through the expansion valve to the outdoor heat exchanger;

adding heat to the refrigerant at the outdoor heat exchanger;

directing the refrigerant from the outdoor heat exchanger to the recovery heat exchanger;

adding heat to the refrigerant at the recovery heat exchanger; and

directing the refrigerant from the recovery heat exchanger to the compressor.

19. The method of claim 8 , further comprising, when operating in the heating mode:

directing the refrigerant from the compressor to the indoor heat exchanger;

removing heat from the refrigerant at the indoor heat exchanger;

directing the refrigerant from the indoor heat exchanger through the expansion valve to the recovery heat exchanger bypassing the outdoor heat exchanger;

heating the refrigerant at the recovery heat exchanger; and

directing the refrigerant from the recovery heat exchanger to the compressor.

20. The method of claim 8 , further comprising performing a deicing procedure, the deicing procedure comprising:

recirculating a first portion of the indoor air from the extracted air outlet, downstream of the recovery heat exchanger, to the fresh air inlet, upstream of the indoor heat exchanger;

directing a second portion of the indoor air across the recovery heat exchanger;

directing the refrigerant from the indoor heat exchanger through the expansion valve to the outdoor heat exchanger; and

directing the refrigerant from the outdoor heat exchanger to the compressor bypassing the recovery heat exchanger.