US Patent 7814967 Heat exchanger

A heat exchanger having an active surface over which a fluid flows to affect an exchange of heat between the active surface and the fluid. In some embodiments, the active surface includes a logarithmic spiral wherein the radius of the logarithmic spiral measured at equiangular radii unfolds at a constant order of growth. Further embodiments exhibit an active surface conforming to the internal or external surface of particular classes or genera of shells.