A radial flow heat exchanger for heating or cooling a fluid includes a sealed fluid manifold for passage of fluid. A sealed fluid receiving hub is spaced interiorly of the interior peripheral portion of the manifold and includes a passageway for passage of fluid into or out of the heat exchanger. A plurality of separate and spaced fluid flow tubes are disposed between the manifold and the hub. Each of the tubes are in sealed fluid communication with the manifold at one end and the other end is in sealed fluid communication with the hub. A fin assembly is positioned between the manifold and the hub and includes a heat conducting material arranged at spaced intervals between the manifold and the hub, the heat conducting material including a plurality of spaced apertures through which tubes pass. The heat conducting material is in intimate heat conducting contact with the tubes whereby fluid flowing between the manifold and the hub flows into each of the tubes in a radial direction between the manifold and the hub and wherein the heat conducting material of the fin assembly operates to give up or pick up heat from the fluid through the wall of the tubes.