Embodiments of a heat transfer apparatus, and related methods, involve a curved flow path, a heat source external to and in thermal communication with at least a portion of an inner radial boundary of the curved flow path, and a working fluid, including a heavier component and a lighter component, flowing through the flow path. The flow path causes the working fluid to experience centrifugal force so as to preferentially force the heavier component toward the exterior wall portion and thereby cause the lighter component to preferentially absorb heat from the interior wall portion.