Nanocapillarity in Graphene Oxide Laminate and Its Effect on Critical Heat Flux

Abstract

The nanocapillarity phenomenon involves ultralow frictional flow of water molecules through nanoscale channels, and here we study this using exceptionally large number of nanochannels within graphene oxide (GO) laminates. The nanoconfined water molecules in GO nanochannels form square lattice (as in the ice bilayer), which melts and jumps across the channels, similar to slip flow, with mean speed of the order of 1 m/s. This ease of liquid spreading in GO laminate is used to delay the critical heat flux (CHF) phenomenon in water pool boiling, by preventing formation/growth of dry spots. The water nanocapillarity speed is derived based on the measured water penetration flux, and the CHF enhancement (up to 140%) is demonstrated on a 1-μm-thick GO laminate. The GO laminate offers efficient surface modifications for increased transport efficiency (and safety margin) of pool boiling heat transfer systems.