Abstract
Boiling heat transfer efficiency is critically dependent on heating surface orientation, particularly the downward-facing mode essential for compact cooling systems from electronics to aerospace. Using molecular dynamics (MD) simulations, this study reveals how heating orientation dictates both boiling performance and the fate of nanoparticles. For downward-facing boiling, optimal heat transfer is achieved not by placing nanoparticles on the heat source, but on the opposing cold wall. This "remote enhancement" triggers explosive boiling 30 ps earlier and increases the peak evaporation rate by 4.6% compared to other particle distributions. Suspended particles offer moderate gains due to restricted fluid mobility from strong adsorption, while particles on the hot wall underperform due to an insulating vapor film. These findings establish a new thermal management principle that strategic nanoparticle placement on cold surfaces unlocks maximum heat transfer in orientation-constrained systems, providing a transformative approach for designing high-performance cooling technologies.