Heat is transferred from the interior to the surface through several methods. One is simply the conduction of sensible heat through the crust - I would guess this accounts for most of it. But some is also transferred through another route: when crust is subducted, it becomes dehydrated, which absorbs heat. Elsewhere, new crust is created and becomes hydrated, which releases heat. The net effect is the transfer of heat from the interior to the surface, but it is transferred in the form of hydration enthalpy rather than sensible heat. A similar process is serpentinisation, which transfers energy in the form of chemical bonds.
I'm looking for data about the total (net) amount of energy that is transferred from the interior to the surface in the form of hydration enthalpy and heat of serpentinisation, as opposed to sensible heat? Is it a substantial fraction of the total ~45TW figure?