Three wheel and simple cycle aircraft environmental control system

1. An environmental control system of an aircraft comprising:

a ram air circuit including a ram air shell having at least one heat exchanger positioned therein, wherein the at least one heat exchanger includes a first heat exchanger, a second heat exchanger, and a third heat exchanger, the third heat exchanger being arranged in fluid communication with and located directly downstream from the first heat exchanger;

at least one dehumidification system arranged in fluid communication with the ram air circuit;

a compressing device arranged in fluid communication with the ram air circuit and the dehumidification system, the compressing device including a compressor and a first turbine operably coupled by a shaft; and

an expansion device, located remotely from the compressing device and arranged in fluid communication with the ram air circuit and the at least one dehumidification system, the expansion device including a second turbine;

wherein the environmental control system is operable in a plurality of modes and during operation in at least one of the plurality of modes, a first medium flows through the first heat exchanger and the third heat exchanger in series and is provided to the compressing device, a second medium is provided to the compressor and the expansion device, and a mixture of the first medium and the second medium is provided at an outlet of the environmental control system, wherein in the at least one mode of the plurality of modes the first medium is expanded within the first turbine, and the compressor is configured to receive energy from the first medium being expanded across the first turbine, the compressor being configured to compress the second medium.

2. The environmental control system of claim 1 , wherein the expansion device is a two wheel air cycle machine.

3. The environmental control system of claim 1 , wherein the expansion device includes a fan operably coupled to the second turbine via another shaft, the fan being arranged in fluid communication with the ram air circuit.

4. The environmental control system of claim 1 , wherein the first medium is bleed air.

5. The environmental control system of claim 1 , wherein the second medium is fresh air.

6. The environmental control system of claim 1 , wherein the compressing device further includes a power turbine configured to provide energy to the compressor by expanding one of the first medium and a third medium.

7. The environmental control system of claim 1 , further comprising a bypass conduit including a valve operable to allow at least a portion of flow from the first heat exchanger to bypass the third heat exchanger, wherein the valve is operable to control a temperature of the medium downstream from third heat exchanger.

8. The environmental control system of claim 1 , wherein during operation in one of the plurality of modes, a first medium and a second medium are mixed before being supplied to a downstream volume.

9. The environmental control system of claim 4 , wherein the bleed air is drawn from at least one of an engine and an auxiliary power unit.

10. The environmental control system of claim 8 , wherein during operation in one of the plurality of modes, the first medium output from the compressing device and the second medium expelled from the expansion device are mixed.

11. The environmental control system of claim 8 , wherein during operation in another mode of the plurality of modes, the second medium bypasses the expansion device.

12. The environmental control system of claim 8 , wherein during operation in another mode of the plurality of modes, work is extracted from both the first medium and a third medium in the compressing device.

13. The environmental control system of claim 8 , wherein during operation in another mode of the plurality of modes, only the second medium is delivered to the downstream volume.

14. The environmental control system of claim 8 , wherein during operation in another mode of the plurality of modes, only the first medium is supplied to the environmental control system.

15. The environmental control system of claim 12 , wherein the third medium is cabin discharge air.

16. The environmental control system of claim 13 , wherein during operation in the another mode, a first medium is exhausted from the compressing device into the ram air circuit.

17. The environmental control system of claim 14 , wherein during operation in the another mode of the plurality of modes, the compressing device is non-operational.