An apparatus providing high efficiency heat exchange between two fluids is disclosed. The apparatus most commonly comprises multiple thin panels with fluid channels directing the flow of the two fluids, specifically: one or more flat panels aligned at some angle to the flow of the fluid traveling through the shortest channel of the thin panels. The panels are arranged in series and parallel, so that the hot fluid travels through multiple thin panels. The coolant is delivered to the thin panels through tubes or manifolds while the hot fluid is delivered through a duct or other piping.