Conceptually, a radiation heat pipe is a method for optimising the view factor between distant objects. In essence, infra-red radiant energy emitted from a source is captured and transmitted with low loss to a sink at lower temperature. A hollow glass wave guide – commonly employed in surgical lasers – is currently under investigation at Stokes: initial data indicates that the waveguide offers very high effective transmissivity.

The primary application envisaged for radiation heat pipes is in the thermal management of electronic devices. For the technique to operate at maximum efficiency, the source temperature must be as high as possible: this requires accessing the junction directly – potentially a key obstacle to adaptation in practice. Moreover, capturing the radiant energy from the source is the key limitation in the technique for sources of characteristic dimension much greater than the diameter of the waveguide – even with high transmissivity material, lenses appear not to operate effectively. In this regard, however, it is evident that radiation heat pipes offer promise for the thermal management of micro- and nano- scale sources.