Mechanisms of thermal nanofluids on enhanced critical heat flux (CHF)

Research on thermal nanofluids has progressed rapidly since their enhanced thermal conductivities were identified about a decade ago. Thermal nanofluids have been observed to increase the critical heat flux (CHF) remarkably under pool-boiling conditions, which could not be explained by conventional theories developed for pure fluids. This paper proposes an alternative mechanism, the long-range structural disjoining pressure arising from the confinement of nanoparticles in a meniscus, and investigates its role under high heat flux conditions. The structural disjoining pressure is incorporated into a four-zoned dry patch model and an analytical model is established to calculate the equilibrium meniscus shape in the presence of nanoparticles. The results show that the structural disjoining pressure can significantly increase the wettability of the fluids and inhibit the dry patch development. Other possible mechanisms on the enhanced CHF are discussed and future studies to resolve remaining issues are recommended.