High flow high efficiency EGR cooler

A heat exchanger apparatus comprising:

• a housing having a plurality of longitudinal walls;
• a plurality of lateral interior diverter walls positioned in the housing to extend away from at least one of the plurality of longitudinal walls to define a plurality of passages between the lateral interior diverter walls and the longitudinal walls, wherein the plurality of passages are configured to receive a second fluid;
• a first fluid conduit positioned within the housing, the first fluid conduit defining a first fluid flow path for a first fluid and comprising a fluid diode that is at least partly fluidically diodic and formed of a thermally conductive material, the fluid diode comprising:
• a first fluid inlet;
• a first fluid outlet;
• a first sub-conduit extending from the fluid inlet to the fluid outlet;
• and
• a second sub-conduit extending from the first sub-conduit proximal the fluid inlet to the first sub-conduit proximal the fluid outlet as a partial loop defining a cavity extending through the partial loop;
• a second fluid conduit positioned within the housing and fluidly connected with the plurality of passages, the second fluid conduit also positioned within the cavity defined by the partial loop, the second fluid conduit being fluidically isolated from the first fluid conduit, the second fluid conduit defining a second fluid flow path for the second fluid that is separate from the first fluid flow path, wherein the second fluid conduit is in thermal communication with the first fluid conduit.