TY - JOUR TI - Molecular dynamics studies of nanoscale evaporation and pool boiling heat transfer on modified surfaces DO - https://doi.org/doi:10.7282/T3C250WR PY - 2018 AB - Phase change has long been known to be an efficient method of heat transfer, due to the latent energy released at constant or near-constant temperature. Pool boiling in particular has been previously used to remove heat fluxes in excess of 1 MW/m2. As technological advances continue to reduce the footprint of high power devices it is critical to investigate boiling heat transfer processes on the nanoscale, so that more efficient heat flux removal can be achieved. In the present work molecular dynamics (MD) is used to simulate various pool boiling scenarios in order to gain a better understanding of the critical factors affecting nanoscale heat transfer. In the first study the effect of hetero- and homogeneous wettability on nanostructured substrates is investigated to understand evaporation and heat flux characteristics. Results reveal that the substrates modified with hydrophilic nano-posts produce larger heat fluxes than heterogenous nanostructure/base wall combinations, due to enhanced kinetic energy transfer. A new coordination number criterion for liquid argon is developed to aid in tracking vapor atoms. The second study details the effect of contact angle and nanostructure pitch on maximum heat flux. Heat flux is found to increase with increasing pitch and decreasing contact angle, reaching an overall maximum of 159 MW/m2. For larger pitches the superheat at which the peak heat flux occurs increases with both contact angle and pitch. In the final study single-layer graphene (SLG) topped substrates were simulated in the pool boiling of water. Results show improvements over plain substrates of 2-10x in heat flux values, which are on the order of 10 MW/m2. CHF was also found to increase by as much as 14% with the addition of SLG, with lower superheats required to attain the CHF condition. KW - Mechanical and Aerospace Engineering KW - Molecular dynamics LA - eng ER -