A heat exchanger and method that includes the use of at least one manifold having a plurality of vanes for circulating a fluid requiring cooling. The vanes define a pair of adjacent flow channels that each has a changing cross sectional shape that varies the aspect ratio of the adjacent flow channels defined by each vane. Each vane also has a twisting or spiral shape that serves to change the orientation of each of its adjacent flow channels to even more effectively enable transfer of heat from a first fluid flowing within one of the flow channels to a second fluid flowing in the other adjacent flow channel. In various embodiments both counter-direction flow and same-direction flows are employed in the manifold.