Anomalously enhanced thermal performance of carbon-nanotubes coated micro heat pipes

We conduct experiments to study the effects of incorporation of carbon nanotubes (CNTs) coatings on the thermal performance of micro heat pipe (MHP) arrays. The microchannels of MHP are fully coated with CNTs which are functionalized through a thermal curing process. The cured CNTs coating manifests a superhydrophilic characteristic and fast water permeation property. The rapid water permeation through CNTs nanostructure enhances the evaporation at the evaporator section and the fluid circulation synergically in the MHP. For evaporation, the superhydrophilic highly permeable porous CNTs nanostructures increase the nucleation sites and promote film-wise evaporation which is more efficient than the bulk evaporation. For circulation of working fluid, an intricately interconnected CNTs networks facilitate the fluid transport with enhanced capillary pressure. The effective thermal conductivity, which denotes the overall performance of a micro heat pipe manifests a maximum enhancement of 202%; and the evaporator heat transfer coefficient which represents the evaporation strength is enhanced up to 61%. Computationally, molecular dynamics simulations are performed to investigate the fast water permeation property of CNTs nanostructure which leads to the anomalous thermal performance enhancement. This study provides interesting insight into the viability of incorporating CNTs nanostructures into an MHP for microscale cooling applications.