A comparison between the efficacy of surface boundary structure and presence of nanoparticles on the condensation two-phase flow inside rough nanochannels has been accomplished by applying molecular dynamics procedure to evaluate the thermal conductivity and flow characteristics. Simulation is performed in a computational region with two copper walls containing rectangular rough elements under different saturated temperatures. The main properties of liquid-vapor interface including density and the number of liquid atoms

are obtained. It is observed that the density profile is more affected by nanoparticles than the roughness. Also

compared to the condensation of nanofluid in a smooth nanochannel

the rough wall causes a greater drop in the temperature at the early time steps and by development of liquid films

effects of the wall roughness reduce. At the first of the condensation process

adding nanoparticle causes that transferring argon particles to the liquid phase increases with a steeper slope. Furthermore

heat current autocorrelation function (HCACF) for nanofluid condensation flow over considered correlation time is analyzed and following that the thermal conductivity for different saturated conditions is calculated. It has been represented that at lower temperatures the roughness makes more significant influence on the heat transfer of two-phase flow

while at higher temperatures the importance of nanoparticles prevails.