Sound absorbing duct for environmental control system

1. A duct comprising:

a rigid air-permeable tube of composite material;

a layer of insulation coupled to an exterior surface of the rigid air-permeable tube, the layer of insulation comprising aramid felt; and

a non-rigid insulation layer applied to an exterior surface of the layer of insulation, the non-rigid insulation layer forming an air-impermeable duct wall that seals the duct, the non-rigid insulation layer comprises a polyetherketoneketone (PEKK) film or a high mass fabric.

2. The duct of claim 1 , wherein the composite material comprises a fabric material having a leno weave arrangement.

3. The duct of claim 1 , wherein the layer of insulation comprises spiral wrapped melamine foam.

4. The duct of claim 3 , wherein the composite material comprises an open weave composite material tube.

5. The duct of claim 1 , further comprising adhesive tape coupled to the layer of insulation and to the non-rigid insulation layer.

6. The duct of claim 1 , wherein an adhesive tape is configured to restrain the layer of insulation and the non-rigid insulation layer, and wherein the adhesive tape includes metallized polyether ether ketone (MPEEK).

7. The duct of claim 1 , wherein the rigid air-permeable tube has a circular cross-section, an elliptical cross-section, a rectangular cross-section, a square cross-section, a triangular cross-section, or a hexagonal cross-section, and wherein the rigid air-permeable tube further includes an inlet, an outlet opposing the inlet, and an interior surface opposing the exterior surface.

8. The duct of claim 1 , wherein the layer of insulation is configured to absorb sound and to thermally insulate the duct, wherein the non-rigid insulation layer is configured to thermally insulate the duct.

9. A vehicle including the duct of claim 1 , the vehicle comprising:

an environmental control system, the environmental control system including:

first zone ducts;

second zone ducts; and

riser ducts coupled to the first zone ducts and the second zone ducts, wherein one of the first zone ducts, the second zone ducts, or the riser ducts comprises the duct of claim 1 .

10. The vehicle of claim 9 , wherein the first zone ducts do not include a noise attenuating muffler.

11. A method of manufacturing a duct, the method comprising:

applying insulation to an exterior surface of a rigid air-permeable tube of composite material to form a layer of insulation on the exterior surface of the rigid air-permeable tube; and

applying non-rigid insulation to an exterior surface of the layer of insulation to form a non-rigid insulation layer in contact with the layer of insulation, the non-rigid insulation layer forming an air-impermeable duct wall that seals the duct, the non-rigid insulation layer comprises a polyether ether ketone (PEEK) film or a high mass fabric.

12. The method of claim 11 , wherein forming the layer of insulation creates a first seam along the layer of insulation, and wherein forming the non-rigid insulation layer creates a second seam along the non-rigid insulation layer, and wherein the method further comprises applying an adhesive over the first seam and the second seam.

13. The method of claim 11 , further comprising applying adhesive tape to the layer of insulation, the non-rigid insulation layer, or both, to secure the layer of insulation to the rigid air-permeable tube, to secure the non-rigid insulation layer to the layer of insulation, or both.

14. An environmental control system comprising:

an air conditioning unit;

an intake port;

an exhaust port; and

a plurality of ducts, wherein the plurality of ducts is configured to direct fluid between the intake port and the air conditioning unit, wherein the plurality of ducts is further configured to direct the fluid from the air conditioning unit and the exhaust port, and wherein a duct of the plurality of the ducts comprises:

a rigid air-permeable tube of composite material;

a layer of insulation coupled to an exterior surface of the rigid air-permeable tube, the layer of insulation comprising aramid felt or a layer of open cell foam; and

a non-rigid insulation layer applied to an exterior surface of the layer of insulation, the non-rigid insulation layer forming an air-impermeable duct wall that seals the duct, the non-rigid insulation layer comprises a high mass fabric.

15. The environmental control system of claim 14 , wherein the duct is a zone duct.

16. The environmental control system of claim 14 , wherein the plurality of duct is configured to direct fluid to a plurality of outlet ports distinct from the exhaust port.

17. The environmental control system of claim 14 , wherein the duct is a riser duct.

18. The environmental control system of claim 14 , wherein the plurality of ducts is configured to direct fluid to a plurality of outlet ports distinct from the exhaust port.

19. The environmental control system of claim 14 , wherein the composite material comprises a fabric material having a leno weave arrangement.

20. The environmental control system of claim 14 , wherein the layer of insulation comprises spiral wrapped melamine foam.

21. The environmental control system of claim 14 , wherein the composite material comprises an open weave composite material tube.

22. The environmental control system of claim 14 , further comprising adhesive tape coupled to the layer of insulation and to the non-rigid insulation layer.

23. The environmental control system of claim 14 , wherein the rigid air-permeable tube has a circular cross-section, an elliptical cross-section, a rectangular cross-section, a square cross-section, a triangular cross-section, or a hexagonal cross-section, and wherein the rigid air-permeable tube further includes an inlet, an outlet opposing the inlet, and an interior surface opposing the exterior surface.