Condensation on nanorods by molecular dynamics

Understanding the effect of calcium containing compounds on ash deposition during boiler operation: experiment study and dynamics calculation

During the operation of the boiler, the ash deposition phenomenon in the furnace will cause abnormal operation of the boiler system. This will lead to an increase the pollutant emission. To relieve the pollutant emission during the abnormal operation of the boiler, the mechanism of ash deposition was investigated from the perspective of reducing the phenomenon for ash deposition in this paper. Calcium-containing compounds play an important role in ash deposition burning coal. Therefore, the influence of calcium-containing compounds on ash deposition was investigated with Zhundong coal in a horizontal tube furnace in this paper. Furthermore, the binding and diffusion properties of calcium-containing compounds on the oxide film's surface were characterized under different temperatures by molecular dynamics simulations. The growth process of surface crystals was also researched by kinetic Monte Carlo method. The results indicated the precipitation rate of calcium gradually increases with the increase of combustion temperature. CaO, CaSO₄, and CaSiO₃ can play an important role in ash deposition burning Zhundong coal. CaSO₄ is more easily to react with α-Fe₂O₃ (110) than CaO or CaSiO₃. The diffusion coefficient of CaSO₄, CaO, or CaSiO₃ increases gradually with the increase of temperature. Furthermore, the system composed of CaSO₄ and oxide film is more affected by temperature than that of CaO or CaSiO₃ and oxide film. Moreover, under the whole temperature, the content of CaSO₄ on the surface of the oxide film is the most. Finally, three calcium-containing minerals can promote each other during the deposition process and accelerate the formation of ash deposits.

Droplet Nucleation and Growth in the Presence of Noncondensable Gas: A Molecular Dynamics Study

The presence of noncondensable gas (NCG) followed by undesirable heat transfer deterioration cannot be avoided in some situations. In this work, droplet nucleation and growth for the Ar-Ne mixed system are investigated using molecular dynamics simulation. Different droplet state transition modes corresponding to the subcooling degree or NCG content are obtained. The interaction between NCG and a droplet caused by gas enrichment near the solid surface is considered to explain the droplet wetting state during the condensation process. Finally, the disappearance mechanism of the flooding mode on the nanostructured surface under a large amount of NCG is clarified from the nanoscale, which could encourage a clear understanding of the NCG effect on dropwise condensation heat transfer on nanostructured superhydrophobic surfaces.