  Since the thermal conduction equation has form invariance under coordinate
transformation, one can design thermal metamaterials with novel functions by
tailoring materials' thermal conductivities. In this work, we establish a
different transformation theory, and propose a layered device with anisotropic
thermal conductivities. The device is able to convert heat flux from parallel
patterns into non-parallel patterns and vice versa. In the mean time, the heat
flux pattern outside the device keeps undisturbed as if this device is absent.
We perform finite-element simulations to confirm the converting behavior. This
work paves a different way to manipulate the flow of heat at will.
