The microwave absorbents of Fe and C nanoparticles as magnetic loss and dielectric loss material respectively were composited with the polyvinyl alcohol(PVA)as binder by spray granulation method,The electromagnetic pa...The microwave absorbents of Fe and C nanoparticles as magnetic loss and dielectric loss material respectively were composited with the polyvinyl alcohol(PVA)as binder by spray granulation method,The electromagnetic parameters of Fe and C composite particles were analyzed by vector network.The complex permittivity and magnetic permeability of Fe and C composite particles matched well with increasing C nanoparticle content,and then the microwave loss property was improved.A minimum reflection loss(RL)of-42.7 dB at 3.68 GHz for a composite with 4.6 mm in thickness can be obtained when the content ratio of the C nanoparticles,the modified Fe nanoparticles and the PVA is 21:49:30(Sample 3).展开更多
The heat transfer enhancement characteristics of water with polystyrene particles are examined in the present numerical study. The numerical study is conducted in the hydrodynamically fully developed turbulent flows w...The heat transfer enhancement characteristics of water with polystyrene particles are examined in the present numerical study. The numerical study is conducted in the hydrodynamically fully developed turbulent flows within a circular duct with the wall boundary condition of a constant heat flux. The thermal conductivity of the turbulent flow obtained by the Reynolds analogy is 1000 times as much as the thermal conductivity of water. On the contrary, the enhancement of thermal conductivity caused by water-microparticles suspension is relatively low. Slight enhancements of the local Nusselt number are obtained in the numerical calculations of Newtonian turbulent flows with the micro-convection effects, thus showing large deviations from the experimental data. The numerical results in non-Newtonian flows are in agreement with the experimental data. Thus, the main cause for the enhancement of the heat transfer of the suspension might be not due to the micro-convection effects but to the non-Newtonian展开更多
基金the support from the National Natural Science Foundation of China(No.51171033)the Fundamental Research Funds for the Central Universities(DUT15LAB05,DUT16LAB03)
文摘The microwave absorbents of Fe and C nanoparticles as magnetic loss and dielectric loss material respectively were composited with the polyvinyl alcohol(PVA)as binder by spray granulation method,The electromagnetic parameters of Fe and C composite particles were analyzed by vector network.The complex permittivity and magnetic permeability of Fe and C composite particles matched well with increasing C nanoparticle content,and then the microwave loss property was improved.A minimum reflection loss(RL)of-42.7 dB at 3.68 GHz for a composite with 4.6 mm in thickness can be obtained when the content ratio of the C nanoparticles,the modified Fe nanoparticles and the PVA is 21:49:30(Sample 3).
文摘The heat transfer enhancement characteristics of water with polystyrene particles are examined in the present numerical study. The numerical study is conducted in the hydrodynamically fully developed turbulent flows within a circular duct with the wall boundary condition of a constant heat flux. The thermal conductivity of the turbulent flow obtained by the Reynolds analogy is 1000 times as much as the thermal conductivity of water. On the contrary, the enhancement of thermal conductivity caused by water-microparticles suspension is relatively low. Slight enhancements of the local Nusselt number are obtained in the numerical calculations of Newtonian turbulent flows with the micro-convection effects, thus showing large deviations from the experimental data. The numerical results in non-Newtonian flows are in agreement with the experimental data. Thus, the main cause for the enhancement of the heat transfer of the suspension might be not due to the micro-convection effects but to the non-Newtonian
