Heat exchanger for gas turbine engines

A gas turbine engine, comprising:

• a turbomachine comprising a compressor section, a combustion section, and a turbine section in serial flow order and at least partially defining a core gas flowpath;
• and
• a heat exchanger comprising:
• a core extending in an axial direction between a first end and a second end opposite the second end, the core defining a first fluid domain and a second fluid domain fluidly isolated from the first fluid domain, wherein the second fluid domain defines one or more helical fluid passageways, wherein the one or more helical fluid passageways define a pitch (P) measured in millimeters (mm), wherein the core defines a diameter (D) measured in mm extending perpendicular to the axial direction;
• a fluid inlet manifold fluidly coupled to the first end of the core and in fluid communication with each of the one or more helical fluid passageways of the second fluid domain, the fluid inlet manifold defining an inlet opening having an axial height (h) measured in mm extending in the axial direction;
• and
• a fluid outlet manifold fluidly coupled to the second end of the core and in fluid communication with the second fluid domain;
• wherein
• ⁢
• h
• D
• =
• P
• D
• ·
• 1
• 4
• ⁢
• π
• ·
• cos
• ⁢
• (
• arctan
• ⁢
• (
• P
• π
• ⁢
• D
• )
• )
• ;
• wherein h/D is less than P/D.