Molecular dynamics study of nanoscale boiling on double layered porous meshed surfaces with gradient porosity

The micro-nanoporous structures enhanced boiling heat transfer has attracted much attention to meet the growing heat dissipation demand. However, it is difficult to completely understand the boiling heat transfer process in the nanoscale pores by traditional experimental methods. The aim of this work is to investigate the boiling process on copper surfaces with two layers of nanoscale porous meshes using molecular dynamics simulations. To understand the effects of gradient porosity, pore size in the bottom/top meshes is changed. Three surfaces with porous meshes of different nanopore sizes are used: a surface with uniform pore size in the bottom and top meshes, a surface with fine bottom mesh and coarse top mesh and a surface with coarse bottom mesh and fine top mesh. The results of this work show that the surfaces with meshes can significantly reduce the bubble inception time when compared with the plain surface. Different bubble inception times are observed for the different surfaces with meshes, depending on the pore size in the bottom/top meshes. The evaporation rates are also higher for the surfaces with meshes. The liquid separation temperature at time around the detachment of the liquid cluster is higher for the surfaces with meshes, and it is the largest for the case with coarse bottom mesh and fine top mesh. Also, fine bottom/top mesh cases have a large average heat transfer rate with the highest when top mesh is fine. The heat exchange rate is also higher for the surfaces with fine top mesh, demonstrating an excellent boiling performance with multi-layer mesh structures.