A heat exchanger assembly for cooling an electronic element includes an oblong condensing tube extending between ends to define an upper chamber downwardly bowed through an upwardly extending arc and a lower chamber upwardly bowed through a downwardly extending arc for dissipating heat. A continuous sheet extends in v-shaped fins between and engaging said arcs of said chambers. The internal fins extend from a center axis of the tube to reverse bends defining the opposite ends of the tube. A continuous sheet extending in sinuous corrugations extends around the exterior of the endless loop between opposite sides of a heat transfer area, which receives the electronic element.