Abstract: A rotary cutting tool for forming a heat plate has a plurality of cutting blades arranged about a cutting tool body. The cutting edge profile of the rotary cutting tool has a lower radius portion and a middle convex portion. The lower radius portion has its center on the axis of the rotary cutting tool and the middle convex portion is defined by an inverse square curve of form Y=1/X2 with the vertical axis of the origin of the inverse square curve offset from the axis of the rotary cutting tool. X has values between 0.25 units and 4 units.

Abstract: A heat exchanger comprises at least one first fluid passage contiguous with at least one second fluid passage. The first fluid passage is separated from the second fluid passage by a common boundary, the boundary having a first surface and a second surface. The first surface is described by a plurality of curvilinear surfaces joined at the ends thereof into a sinuous curvilinear surface and the second surface is described by a plurality of curvilinear surfaces joined at the ends thereof into a sinuous curvilinear surface. The curvilinear surfaces of the first and the second curvilinear surfaces are defined by a portion of an inverse square curve.