A heat exchanger (HX) (120) utilizing a working fluid and having a high heat flux transfer capacity. The HX comprises a core (130) having a heat transfer surface (128), a length and a width. Inlet manifolds (140) and outlet manifolds (142) located alternatingly across the width of the core extend the length of the core. Interconnecting channels (144) each fluidly communicate with a corresponding outlet manifold and the two inlet manifolds located immediately adjacent that outlet manifold. Heat exchanger fin (154) in thermal communication with the heat transfer surface (128) generally defines the surface of the interconnecting channels. A pathway directs the working fluid first towards and then away from heat transfer surface (128) in a direction substantially normal to the heat transfer surface. Heat is transferred to or from the working fluid from heat transfer fin (154) as the fluid flows toward and away from the heat transfer surface.