Increasing global energy demands results in the need for efficient and environmentally friendly solutions. Nanofluids, which are suspensions of particles with an average size smaller than 100 nm in basefluids (mostly water, glycols and refrigerants), may become such a solution. Upward trends in excess heat which should be removed from electronic devices intensify research on this topic. Nanofluids show potential to work as ecological heat carriers without clogging, sedimentation and abrasion problems, commonly met with suspensions of larger particles.

Usage of nanofluids in heat exchangers may result in enhanced thermal efficiency what for thermosyphon means lower thermal resistance. Two-phase closed thermosyphon is relatively simple device that is characterized by quite complex thermodynamics. Experimental study presented here focuses on selected carbon-based nanofluids: nanohorns stabilized with SDS and graphene oxide with and without addition of the same surfactant, employed as working fluid in thermosyphon.

Addition of nanoparticles to water may improve heat transfer processes in the device by various mechanisms, among others by nanolayer deposition on the inner surface of the evaporator and lowering the surface tension. Moreover, some nanofluids prevents thermal instabilities − geyser boiling - appearing in the device exposed to high heat fluxes. This somewhat unforeseen result is mostly affected by employed surfactants. However, it turns out that chemistry of the particle surface also plays a key role.