Variable geometry heat exchanger apparatus

A heat exchanger apparatus for use in an oil cooling system of an aircraft engine comprising:

• a surface cooler;
• wherein the surface cooler is disposed in a housing;
• the surface cooler comprising:
• a manifold portion including a radially inner surface and a radially outer surface, an upstream wall and an opposite downstream wall;
• one or more flow through channels in fluid communication with the manifold portion and extending through the manifold portion, the one or more flow through channels having contained therein a heat transfer fluid;
• and
• a plurality of cooling fins formed unitarily with the manifold portion, projecting from an outer surface thereof and positioned perpendicular to the one or more flow through channels;
• and
• a passive automatic retraction and extension system coupled to the surface cooler, the passive automatic retraction and extension system comprising a thermal actuation component comprised of a shape memory alloy and a plate including a plurality of openings formed therein and overlying the surface cooler, wherein the shape memory alloy senses a temperature of at least one of the heat transfer fluid and a cooling fluid flow and actuates a change in a geometry of the surface cooler in response to a sensed change in the temperature of the at least one of the heat transfer fluid and the cooling fluid flow, so that the shape memory alloy provides a passive, automatic retraction of the plurality of fins through the plurality of openings in the plate and out of the cooling fluid flow during a first state of operation and provides a passive, automatic extension of the plurality of fins through the plurality of openings in the plate and into the cooling fluid flow during a second state of operation.

An engine comprising:

• a fan assembly;
• a core engine downstream of the fan assembly;
• a fan casing circumscribing the fan assembly;
• a booster casing circumscribing the core engine such that a bypass duct is defined between the fan casing and the booster casing;
• and
• an arcuate heat exchanger apparatus coupled to one of the fan casing and the booster casing, the arcuate heat exchanger comprising:
• a surface cooler having disposed therein one or more fluid flow channels configured for a passage therethrough of a heat transfer fluid to be cooled, the heat transfer fluid in a heat transfer relation on an inner side of said one or more fluid flow channels, the surface cooler including a plurality of fins projecting from an outer surface thereof;
• wherein the surface cooler is disposed within a housing;
• and
• a passive automatic retraction and extension system coupled to the surface cooler, the passive automatic retraction and extension system comprising:
• a thermal actuation component comprised of a shape memory alloy and a plate including a plurality of openings formed therein and overlying the surface cooler, wherein the shape memory alloy senses a temperature of at least one of the heat transfer fluid and a cooling fluid flow and actuates a change in a geometry of the surface cooler in response to a first, sensed change in temperature of the at least one of the heat transfer fluid and the cooling fluid flow to provide a passive, automatic retraction of the plurality of fins through the plurality of openings in the plate and out of the cooling fluid flow during a first state of operation and to provide a passive, automatic extension of the plurality of fins through the plurality of openings in the plate and into the cooling fluid flow during a second state of operation.