Icicles are often formed under the downside surface of conductor in the wet growth icing of overhead power line. When the ice deposit around overhead power line is molten by Joule heat produced by current, the pattern...Icicles are often formed under the downside surface of conductor in the wet growth icing of overhead power line. When the ice deposit around overhead power line is molten by Joule heat produced by current, the pattern of heat transfer of ice deposit with icicles is dissimilar to that without icicle, so the ice-melting model for the columnar icing conductor cannot be applied to icicle-shaped icing conductor. According to the heat-transfer characteristic of the icicle-shaped icing conductor, this paper puts forward a DC ice-melting model for the icicle-shaped icing conductor. Because this full model includes three-dimensional heat-transfer and interface movement, which cannot be solved in closed form, a finite element scheme in space-domain and a finite difference scheme in time-domain are employed to discretize the governing equations. Firstly the whole ice-melting process on the icicle-shaped icing conductor is simulated by this model. Then the simulated results are validated by ice-melting experiments in the artificial chamber. The study from the model and the experiments shows that the size and length of icicle as well as the space between the adjacent icicles are factors to affect ice-melting. With the shorter icicle space, the bigger icicle size and the longer icicle-length, the surface of ice layer is enlarged and then more heat is taken away by the convection and radiation, so the ice melting time will get longer.展开更多
Interfacial water is of fundamental importance in many technological fields, such as biological processes, chemical reactions and lubrications. A prevalent way to study the structure and dynamics of interfacial water ...Interfacial water is of fundamental importance in many technological fields, such as biological processes, chemical reactions and lubrications. A prevalent way to study the structure and dynamics of interfacial water is carrying out molecular dynamics simulations with empirical potential water models. However, discrepant results have been reported due to their different charge geometries and target properties. Here we investigated the interfacial water structures on smooth surfaces of varying hydrophobicity at low temperatures by comprehensive molecular dynamics simulations with the prevailing water models. It is shown that the choice of the water model can significantly change the water structure on the hydrophilic surface, while has a minor effect on the contact angle on a hydrophobic surface. Furthermore, zero-dimensional ice pyramids and one-dimensional icicles were formed under the regulation of external charges injected to the substrate or imposed electric field, respectively. These results offer new insights into the water structures on different surfaces and reasonable choice of parameters in molecular simulations, and the development of water models.展开更多
基金supported by the Special Funds for Major State Basic Research Projects of China (973 Program) (Grant No. 2009CB724501)the Natural Science Foundation Project of CQ CSTC (2008BB6157)
文摘Icicles are often formed under the downside surface of conductor in the wet growth icing of overhead power line. When the ice deposit around overhead power line is molten by Joule heat produced by current, the pattern of heat transfer of ice deposit with icicles is dissimilar to that without icicle, so the ice-melting model for the columnar icing conductor cannot be applied to icicle-shaped icing conductor. According to the heat-transfer characteristic of the icicle-shaped icing conductor, this paper puts forward a DC ice-melting model for the icicle-shaped icing conductor. Because this full model includes three-dimensional heat-transfer and interface movement, which cannot be solved in closed form, a finite element scheme in space-domain and a finite difference scheme in time-domain are employed to discretize the governing equations. Firstly the whole ice-melting process on the icicle-shaped icing conductor is simulated by this model. Then the simulated results are validated by ice-melting experiments in the artificial chamber. The study from the model and the experiments shows that the size and length of icicle as well as the space between the adjacent icicles are factors to affect ice-melting. With the shorter icicle space, the bigger icicle size and the longer icicle-length, the surface of ice layer is enlarged and then more heat is taken away by the convection and radiation, so the ice melting time will get longer.
文摘Interfacial water is of fundamental importance in many technological fields, such as biological processes, chemical reactions and lubrications. A prevalent way to study the structure and dynamics of interfacial water is carrying out molecular dynamics simulations with empirical potential water models. However, discrepant results have been reported due to their different charge geometries and target properties. Here we investigated the interfacial water structures on smooth surfaces of varying hydrophobicity at low temperatures by comprehensive molecular dynamics simulations with the prevailing water models. It is shown that the choice of the water model can significantly change the water structure on the hydrophilic surface, while has a minor effect on the contact angle on a hydrophobic surface. Furthermore, zero-dimensional ice pyramids and one-dimensional icicles were formed under the regulation of external charges injected to the substrate or imposed electric field, respectively. These results offer new insights into the water structures on different surfaces and reasonable choice of parameters in molecular simulations, and the development of water models.
