Abstract: A two-pass, loop flow heat exchanger includes an inlet plenum that receives a fluid to be cooled, a housing, a plurality of inlet flow passages substantially centrally positioned within the housing and having a first end fluidly coupled to the inlet plenum to receive the fluid, a turnaround plenum fluidly coupled to a second end of the inlet flow passages for reversing the flow of the fluid, a plurality of outlet flow passages peripherally positioned within the housing and having a first end fluidly coupled to the turnaround plenum, and an outlet plenum fluidly coupled to a second end of the outlet flow passages to present the fluid.