Heat exchanger thermal fatigue stress reduction

1. A plate fin heat exchanger comprising:

a plate fin core having a plurality of plates defining a set of hot air passages extending from a hot air inlet region of the plate fin core to a hot air outlet region of the plate fin core and a set of cool air passages extending from a cool air inlet region of the plate fin core to a cool air outlet region of the plate fin core, wherein the hot air inlet region of the plate fin core is disposed at a first side of the plate fin core, wherein the hot air outlet region of the plate fin core is disposed at a second side of the plate fin core opposite the first side of the plate fin core, wherein the cool air inlet region of the plate fin core is disposed at a third side of the plate fin core that is orthogonal to the first and second sides of the plate fin core, and wherein the cool air outlet region of the plate fin core is disposed at a fourth side of the plate fin core that is opposite the third side and orthogonal to the first and second sides of the plate fin core; and

a mounting flange circumscribing the cool air outlet region at the fourth side of the plate fin core the mounting flange defined by first and second parallel legs and third and fourth parallel legs that are perpendicular to the first and second legs, at least a portion of the mounting flange having a plurality of heat transfer structures that extend into a flow path of cooling air exiting the cool air outlet region of the plate fin core, wherein the plurality of heat transfer structures of the mounting flange are comprised on the first leg of the mounting flange which extends along an intersection of the first and fourth sides of the plate fin core.

2. The plate fin heat exchanger of claim 1 , wherein the plurality of heat transfer structures comprise a plurality of heat transfer fins.

3. The plate fin heat exchanger of claim 1 , further comprising a hot air inlet proximate the hot air inlet region of the plate fin core, wherein the plurality of heat transfer structures of the mounting flange are proximate the hot air inlet.

4. The plate fin heat exchanger of claim 3 , wherein the hot air inlet is configured to receive at least one of bleed air from a gas turbine engine and compressed air from an air compressor.

5. The plate fin heat exchanger of claim 1 , wherein the mounting flange and the plurality of heat transfer structures are formed of a contiguous piece of material.

6. The plate fin heat exchanger of claim 5 , wherein the material comprises aluminum.

7. The plate fin heat exchanger of claim 1 ,

wherein the mounting flange comprises a first face disposed parallel the flow path of the cooling air exiting the cool air outlet region of the plate fin core and a second face disposed orthogonal the first face and extending in a direction away from the flow path of the cooling air, and

wherein the plurality of heat transfer structures extend from the first face into the flow path of the cooling air exiting the cool air outlet region of the plate fin core.

8. The plate fin heat exchanger of claim 7 , wherein the second face of the mounting flange is configured to mount with at least one external component.

9. The plate fin heat exchanger of claim 1 , wherein the set of hot air passages and the set of cold air passages comprise alternating sets of passages.

10. The plate fin heat exchanger of claim 9 , wherein the cool air inlet is configured to receive ram air.

11. A method comprising:

directing hot air through a set of hot air passages of a core of a plate fin heat exchanger, the set of hot air passages extending in a first direction, wherein directing the hot air through the set of hot air passages comprises:

directing the hot air through a hot air inlet region of the core of the plate fin heat exchanger disposed at a first side of the core of the plate fin heat exchanger; and

directing the hot air through a hot air outlet region of the core of the plate fin heat exchanger disposed at a second side of the core of the plate fin heat exchanger, the second side opposite the first side;

directing cool air through a set of cool air passages of the core of the plate fin heat exchanger, the set of cool air passages extending in a second direction, wherein directing the cool air through the set of cool air passages comprises:

directing the cool air through a cool air inlet region of the core of the plate fin heat exchanger disposed at a third side of the core of the plate fin heat exchanger that is orthogonal to the first and second sides of the core of the plate fin heat exchanger; and

directing the cool air through a cool air outlet region of the core of the plate fin heat exchanger disposed at a fourth side of the core of the plate fine heat exchanger that is opposite the third side and orthogonal to the first and second sides; and

flowing a portion of the cool air over a plurality of heat transfer structures of a mounting flange that circumscribes the cool air outlet region at the fourth side of the core of the plate fin heat exchanger the mounting flange defined by first and second parallel legs and third and fourth parallel legs that are perpendicular to the first and second legs, wherein the plurality of heat transfer structures of the mounting flange are comprised on the first leg of the mounting flange which extends along an intersection of the first and fourth sides of the plate fin core.

12. The method of claim 11 , wherein the plurality of heat transfer structures comprise a plurality of heat transfer fins.

13. The method of claim 11 , wherein flowing the portion of the cool air over the plurality of heat transfer structures of the mounting flange comprises flowing the portion of the cool air over the plurality of heat transfer structures of the mounting flange disposed proximate a hot-hot region of the plate fin heat exchanger.

14. The method of claim 13 , wherein the hot-hot region of the plate fin heat exchanger comprises a region of the plate fin heat exchanger that is proximate the hot air inlet region of the plate fin heat exchanger and the cool air outlet region of the plate fin heat exchanger.

15. The method of claim 11 , wherein the first direction is orthogonal to the second direction.