In situ boiling-induced self-assembly of stably self-dispersed crumpled graphene for efficient utilization of thermal energy.

• We generate a stably self-dispersed crumpled graphene/water nanofluid at 100 °C. • The nanofluid enhances the heat transfer coefficient by 89.1% over deionized water. • The enhancement is due to the porous structure generated by self-assembly. Boiling can induce the self-assembly of nanomaterials in nanofluids to generate reliable micro/nanostructures for enhancing boiling heat transfer. The practical applications of most nanofluids in boiling, however, are limited by the poor thermal stability at the boiling point, and improving the thermal stability of nanofluids at such high temperature is challenging. Here, we demonstrate that the crumpled graphene can remain uniformly and stably dispersed within deionized water at the boiling point of 100 °C due to its highly wrinkled structure, while self-assembling to generate a porous structure on the substrate during boiling. Such porous structure can vary the surface micromorphology, wettability and roughness, which increases the nucleation sites and departure frequency of bubbles, thus effectively enhancing the critical heat flux and the maximum heat transfer coefficient by 80.7 and 89.1% compared to the pristine copper substrate, respectively. This in situ boiling-induced self-assembly provides a facile and low-cost strategy to achieve high-performance boiling heat transfer for a wide variety of nanomaterials. The crumpled graphene/water nanofluid used can be directly utilized as a phase change working medium in boiling systems to harvest thermal energy and generate clean steam. [Display omitted] [ABSTRACT FROM AUTHOR]