水温分层水库中大规模高浓度泥沙侵入及长期浊水放流问题的对策

用数值模型描述了水温分层水库中大规模高浓度泥沙流入时的水动力学现象,定量研究并讨论了如何改善这种情况下水库形成的长期浊水化现象。在大流量、高浓度时,洪水水流沿着水库底部向下游高速流动,撞击大坝后造成的回流形成洪水的混浊水体与水库内周围环境水体的混合,导致水库长时间浑浊,形成长期浊水放流。该机理提示了减少洪水后库内混浊水体积的可能性。数值实验表明,如果合理采用选择性取水设备,或通过下层泄洪口可以成功地减少混浊水和清洁水体的混合,将洪水后库内残余混浊水的量减少88％。进一步的计算表明,如果可以改变温度跃层的位置或泄洪口的高程,则可以控制洪水时泥水在水库中的流动,以改善洪水后浊水放流的状况。     

Role of working fluids on the cooling of discrete heated modules: a numerical approach

The study has focused on the role of working fluids (air, water and FC-72) on the cooling of discrete heated modules under free, forced and mixed convection medium. Three non-identical protruding discrete heat sources are arranged at different positions on a substrate board following golden mean ratio (GMR). Numerical simulations for these heat sources are carried out using a commercial software (ANSYS-Icepak R-15) to simulate their flow and temperature fields under three different modes of heat transfer. Results suggest that the temperature of the heat sources is a strong function of their size, position on the substrate board, the velocity of the fluid and type of working fluid used. A correlation has been proposed for the temperature of these heat sources keeping in mind their strong dependence on the afore-mentioned parameters. It has been found that water can be used for better heat removal from the heat sources due to its high boiling point. The whole idea gives a clear insight to the electronic cooling engineers regarding the selection of working fluids and modes of heat transfer for the cooling of electronic components.     

New oil-gelling agents for cosmetics: formation mechanism of oil gels

New oil-gelling agents have been developed composed of a long-chain dialkyl phosphate (DP) surfactant and aluminium ion or multinuclear aluminum ion (MAI) which provide good oil-gel systems. One such gelling agent is the aluminum salt of DP (DP-Al) prepared as a precipitate by mixing DP with aluminum chloride in aqueous solutions. Addition of small amounts of the salt to non-polar oils led to hardening of the oil solutions at temperature below the melting point of the alkyl chain (Tc) of DP-Al. Results obtained by X-ray diffraction techniques and with scanning electron microscopy (SEM) revealed that linearly-polymerized assemblies of DP-Al expand in oils three-dimensionally, which suggests that the excellent stability of the gel systems arises from the highly ordered structure. The gelling agent of DP-Al offered the ideal rheological property to waxy cosmetic products such as lipsticks. The complexes of DP with MAI particles (1 nm diameter) of aluminum chlorohydrate, Al₁₃O₄(OH)₂₄(H₂O)₁₂CI₇, provided the ideal thixotropic behaviour in non-polar oils. The DP-MAI particle complexes were found to interact weakly by cohesive forces which makes a highly ordered structure of the DP-MAI particle complexes. The DP-MAI particle complexes gave excellent stability and transparency to cosmetic products such as w/o creams.