Spiral ripple circumferential flow heat exchanger

An improved oil cooler, comprising a plurality of stacked energy exchange structures, each said structure comprising:

• first and second generally parallel opposing plates joined to define hollow passageway therebetween and further defining an inlet and an outlet therein and a generally overall circular flow path from the inlet to the outlet, each of said opposing plates undulating in cross-section to define a plurality of opposing valleys forming the hollow passageway, at least some of the valleys of each said plate being arranged to follow spiral curves disposed at an oblique angle to the circular flow path, the oblique angle being higher near the center of the circular flow path than at the outer periphery thereof with apexes of valleys of the first plate arranged to cross apexes of valleys of the second plate such that the area between opposing valleys defines crossing passages.