非自动衡器电磁兼容测试现状和试验结果分析

随着电磁环境日益复杂,非自动衡器类产品出现电磁兼容问题层出不穷。作者根据多年的实际工作经验,对已经发布的JJF 1834-2020 《非自动衡器通用技术要求》中涉及电磁兼容抗干扰性能试验进行了梳理,同时剖析了电磁兼容问题存在的主要原因,进一步阐述了电磁兼容试验对计量器具型式评价的重要作用。     

微通道散热器新型结构设计及流动与散热分析

为了提高微通道散热器的散热性能,采用Fluent对散热器内部流场流动和换热特性进行了数值仿真分析。同时通过调整通道和翅片截面的宽度,添加肋柱与孔洞,设计了一种新型微通道散热器结构。结果表明:在不同入口体积流量(0.25—1.5 L/min)下,新型微通道散热器结构的各通道内质量流量的极差为初始结构的1/8,流体不均匀分配因子为初始结构的9%—56%,基底最大温度降低6.4—8.8℃,基底平均温度降低7.1—10.1℃,高换热量区内换热量的极差为初始结构的17%—24%,平均Nu数是初始结构的2.1—2.4倍。Rth值较初始结构减少了7%—26%。说明该设计结构下的内部流场分配均匀且换热型性能优越。     

二氧化硅纳米颗粒对液滴冻结特性的影响

为了改善液滴的冻结特性,以含SiO₂纳米颗粒的液滴为研究对象,研究了不同SiO₂纳米颗粒含量(5 mg/mL、10 mg/mL、30 mg/mL、50 mg/mL)和不同冷表面温度(268 K、265 K、263 K)对液滴动态冻结特性(液滴形变、接触角、冻结时间等)的影响。结果表明:二氧化硅液滴(SiO₂-H₂O)的冻结时间受过冷度和SiO₂纳米颗粒含量的影响。在低过冷度(263K)时,10 mg/mLSiO₂-H₂O加速冻结,可加快34.78%,在高过冷度(265 K和263 K)时,5 mg/mLSiO₂-H₂O均表现为延迟冻结,分别延缓21.2%和36.84%。此外,根据液滴形变特性,SiO₂纳米颗粒可以使初始液滴砂化加剧,减少冻结液滴内部气泡的释放。SiO₂纳米颗粒与固液相界面之间相互影响,使得液滴冻结完成时纵向变化率减少,横向形变增强,...     

镀TiO2喷嘴-筒状电极下负脉冲放电等离子体降解酸性橙Ⅱ（英文）

Many sub-products of pulsed discharge,such as ultraviolet light,strong electric fields,shock waves and active species,are effective in treating wastewater.To improve the efficiency of the discharge plasma technology in removing pollutants,adding TiO2 photo-catalyst to pulsed discharges could help.A negative-pulsed-discharge system,which has nozzle discharge electrodes with or without TiO2 coating,is used to degrade azo dye Acid Orange Ⅱ,and the effects of several key conditions(maximum pulse voltage,pulse repetition frequency,initial mass concentration of Acid Orange Ⅱ initial solution pH,treatment duration,the phase of discharge,and the existence of TiO2) on the degradation are experimentally investigated.The degradation of Acid Orange Ⅱ increases with maximum pulse voltage,pulse repetition frequency,and treatment duration,and it is larger when putting the discharge electrode on the solution surface than in air or inside the solution,i.e.the discharge in gas phase is more effective than that in gas-liquid phase or liquid phase.The degradation decreases as the initial mass concentration of the solution increases.It also relates to pH and is higher at acidic conditions than at neutral or alkaline conditions.Compared to treatments without TiO2,the ones using the nozzle discharge electrode with TiO2 coated increase the degradation of Acid Orange Ⅱ by 5 %.It is concluded that the proposed system with TiO2 added in can remove Acid Orange Ⅱ from wastewater effectively.