Methods of cooling a fluid using an annular heat exchanger

A method of cooling a hot fluid in an annular duct of a gas turbine engine, comprising:

• directing the hot fluid through a plurality of cooling channels that are radially layered within the annular duct to define a heat transfer area, wherein the plurality of cooling channels are defined within a plurality of curvilinear plates that are radially layered within the annular duct, and wherein each curvilinear plate from the plurality of curvilinear plates traverses the annular duct from a radially inner portion to a radially outer portion with respect to a centerline of the annular duct, and further wherein each cooling channel from the plurality of cooling channels extends from a first opening along the radially inner portion of the curvilinear plate to a second opening along the radially inner portion of the curvilinear plate;
• and
• passing a cooling fluid through the annular duct in an axial direction of the gas turbine engine, wherein at least 90% of the cooling fluid flows through the heat transfer area of the annular duct.

A method of cooling a hot fluid in an annular duct of a gas turbine engine, comprising:

• passing the hot fluid into a first inner radial tube, through a plurality of cooling channels defined within a plurality of curvilinear plates that are radially layered within the annular duct, and into a second inner radial tube, wherein each curvilinear plate from the plurality of curvilinear plates traverses the annular duct from a radially inner portion to a radially outer portion with respect to a centerline of the annular duct, wherein a first opening is in fluid communication with the first inner radial tube along the radially inner portion of the curvilinear plate, and wherein a second opening is in fluid communication with the second inner radial tube along the radially inner portion of the curvilinear plate;
• and passing a cooling fluid through the annular duct.