基于光线追迹的方形微通道X光器件模拟

为研究方形微通道X光器件的成像特性,基于光线追迹法建立了一种方形微通道X光器件的数学模型。利用数值模拟的方法对比了方形微通道X光器件和传统多毛细管X光器件的传输效率,研究了方形微通道X光器件的潜在光源位置分辨能力、光斑形貌等成像特性。证实了方形微通道X光器件在深空探测和空间X射线成像领域的潜在应用价值。     

Streaming potential and electroviscous effect in heterogeneous microchannels

This communication presents a theoretical analysis of the streaming potential and the electroviscous effect on pressure-driven flow in heterogeneous microchannels. Compact formulae in terms of phenomenological coefficients are derived for the streaming potential and the apparent viscosity ratio in channels with surface charge variations perpendicular and parallel to the applied pressure gradient. In the latter case, the streaming potential per unit liquid flow in a multi-section channel is found to be simply the summation of that in each homogeneous section. The apparent viscosity ratio is a weighted average of each section where the hydrodynamic resistance serves as the weighting factor. The phenomenological coefficients are specified using electrokinetic flow analysis, through which the streaming potential and electroviscous effect in a two-section slit channel are examined. It is found that they both depend on the arrangement of surface heterogeneity in small microchannels. This dependence, however, gets weak in large microchannels, which is consistent with the prediction of thin double layer approximation.

Straight-through microchannel devices for generating monodisperse emulsion droplets several microns in size

The authors recently proposed a promising technique for producing monodisperse emulsions using a straight-through microchannel (MC) device composed of an array of microfabricated oblong holes. This research developed new straight-through MC devices with tens of thousands of oblong channels of several microns in size on a silicon-on-insulator plate, and investigated the emulsification characteristics using the microfabricated straight-through MC devices. Monodisperse oil-in-water (O/W) and W/O emulsions with average droplet diameters of 4.4–9.8 μm and coefficients of variation of less than 6% were stably produced using surface-treated straight-through MC devices that included uniformly sized oblong channels with equivalent diameters of 1.7–5.4 μm. The droplet size of the resultant emulsions depended greatly on the size of the preceding oblong channels. The emulsification process using the straight-through MC devices developed in this research had very high apparent energy efficiencies of 47–60%, defined as (actual energy input applied to droplet generation/theoretical minimum energy input necessary for making droplets) × 100. Straight-through MC devices with numerous oblong microfluidic channels also have great potential for increasing the productivity of monodisperse fine emulsions.     

微流控芯片微通道热压成形中塑料流动的仿真

目前,PMMA微流控芯片微通道成形过程中热压参数的调整周期很长.针对这一问题,本文基于热粘弹性理论建立微通道成形过程中的热-应力耦合场模型,利用有限元软件对微通道热压成形过程进行了仿真,通过对不同压力、温度和时间下微通道成形的仿真,得出了最优化的工艺参数.实验结果验证了仿真结论,可以实现对微流控芯片微通道热压成形过程的快速有效的控制.     

小功率金卤灯电弧管泡壳成形机理及设备的研究

本文介绍小功率金属卤化物灯电弧管用的石英玻璃特性，根据石英玻璃的特性来研究电弧管泡壳成形的方法，并计算玻管的堆料量，同时介绍泡壳成形机的工作原理和泡壳成形质量控制方法。     

面向热伏发电系统的紧凑式换热结构设计及性能分析

中低温地热温差材料热伏发电是世界性研究热点,其难点是如何提高热伏发电的热电转换效率。本文提出一种基于自相似结构（SSHS）的换热结构设计方案,可以大大减小一般热电转换系统换热结构的体积与重量,同时提高热电转换效率。以一个热端热沉的流动换热过程为例,利用数值计算方法对其换热和流动阻力特性进行了模拟和分析,并与两种传统换热结构进行了对比。计算结果表明：SSHS热沉具有更强的换热能力,换热均匀性更好,流量范围0.010 3～0.018 6 kg/s、热流密度2 W/cm²及进口热水温度100 ℃条件下,SSHS热沉的换热能力可达一般换热结构的2倍以上,换热面（释热面）温度高出5～10 K,温度分布均匀性提高了50%以上,进而有利于提高热电转换效率;此外,SSHS虽然相较传统结构有更大的流动阻力,但对于当前设计总流动阻力也不超过450 Pa,因此SSHS热沉非常适合用于模块化的热电直接转换系统。     

扇形凹穴型微通道液体流动与传热特性的数值模拟

为得到扇形凹穴型微通道内单相液体流动与传热特性,以等截面矩形微通道为参照,利用FLUENT计算流体力学模拟与分析软件进行三维数值模拟,采用有限体积法离散模型和SIMPLEX算法进行层流计算,讨论扇形凹穴型微通道热沉在不同体积流量不同热流密度条件下流体流动特性和传热特性.模拟结果表明：较大Re条件下扇形凹穴型微通道具有很...     

高热流微冷却器的换热性能研究

对以水为换热介质的微通道冷却器对模拟发热电子芯片进行冷却的换热性能进行了实验研究.通过测量流体的流量、进出口温度、发热片表面热流密度,获得了不同几何结构微通道冷却器在不同加热功率、不同Re数条件下的换热特性和冷却效果.结果表明,微通道冷却器可以有效地对表面热流密度高达5.34×105 W/m2的发热电子芯片进行冷却;微通道冷却器的换热性能随Re数的增大而提高,所提高的幅度随加热功率的增大而增大;微通道的几何结构对换热性能有显著影响,平均Nu数随微通道的宽深比增大而增大.     

采用S7-300型西门子PLC实现缅甸冷库全自动控制

本文主要介绍了西门子系列PLC的技术特点,并且采用S7－300型PLC作为系统的主控制器,对我公司出口缅甸最大的冷库成套项目实现了全自动控制,作者在西门子“WINCCV4．02”组态软件平台上自行设计开发了动态监测组态画面,在计算机上监测整个系统的设备运行状况,同时进行参数设定和指令控制等功能。     

Pressure distributions of gaseous slip flow in straight and uniform rectangular microchannels

This paper presents analytical derivations of the pressure distribution in straight and uniform rectangular microchannels in the slip flow regime and new experimental data in those channels. The flow is to be steady state, two-dimensional, isothermal, and to have negligible transverse velocities with a first order slip boundary condition. The measured pressure distributions of airflows are compared with newly derived analytical results. There is close agreement between the measurements and calculation by the slip flow formula. The dimensionless location of the maximum deviation from the linear pressure distribution is found analytically and compared with the measurements. This dimensionless location of the maximum deviation increases with the increasing pressure ratios in the slip flow regime. The effect of several parameters such as the channel aspect ratio and the Knudsen number on the locations of maximum deviation from linearity are investigated. The nonlinearity of the pressure distribution is also discussed.