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1.
Singlet oxygen was generated by reaction of sodium hypochlorite and hydrogen peroxide in a micro-channel. The two reagent solutions were delivered into the micro-channel by a syringe pump, providing a laminar flow liquid-liquid interface. The chemiluminescence from the singlet oxygen was emitted in the collapse of the interface due to molecular diffusion under laminar flow conditions. The chemiluminescence intensity was observed continuously and stably for each combination of reagents fed into the micro-channel; while, in the normal batch-type reactor the chemiluminescence peaks from singlet oxygen were observed within ca. 5 s. The features of the chemiluminescence emitted under laminar flow conditions were examined by changing the concentrations of sodium hypochlorite and hydrogen peroxide; the concentrations of 2.5 mM sodium hypochlorite and 7.5 mM hydrogen peroxide provided highest chemiluminescence intensities without bubble formation. Also, the effects of beverages, such as green tea, coffee, white wine, red wine, and sake (rice wine), on the chemiluminescence intensity as well as the concentrations of sodium hypochlorite and hydrogen peroxide were examined. The chemiluminescence intensities observed with addition of the beverages to the reagents decreased in the following orders; green tea > coffee > red wine > rice wine > white wine (being added to sodium hypochlorite); coffee > white wine > green tea > red wine > rice wine (being added to hydrogen peroxide). It was found that coffee decreased the chemiluminescence intensity (ca. 33% chemiluminescence decrease) without altering the concentrations of sodium hypochlorite or hydrogen peroxide. The cause of the decrease in chemiluminescence with coffee is discussed. 相似文献
2.
Steady laminar forced convection gaseous slip-flow through parallel-plates micro-channel filled with porous medium under Local
Thermal Non-Equilibrium (LTNE) condition is studied numerically. We consider incompressible Newtonian gas flow, which is hydrodynamically
fully developed while thermally is developing. The Darcy–Brinkman–Forchheimer model embedded in the Navier–Stokes equations
is used to model the flow within the porous domain. The present study reports the effect of several operating parameters on
velocity slip and temperature jump at the wall. Mainly, the current study demonstrates the effects of: Knudsen number (Kn),
Darcy number (Da), Forchheimer number (Γ), Peclet number (Pe), Biot number (Bi), and effective thermal conductivity ratio
(K
R) on velocity slip and temperature jump at the wall. Results are given in terms of skin friction (C
f
Re
*) and Nusselt number (Nu). It is found that the skin friction: (1) increases as Darcy number increases; (2) decreases as Forchheimer
number or Knudsen number increases. Heat transfer is found to (1) decreases as the Knudsen number, Forchheimer number, or
K
R increases; (2) increases as the Peclet number, Darcy number, or Biot number increases. 相似文献
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4.
Measurement of concentration distributions of suspended particles in a micro-channel is one of the most crucial necessities in the area of Lab-on-a-chip to be used for various bio-chemical applications. One most feasible way to measure the concentration field in the micro-channel is using μ-LIF (micro-scale laser-induced fluorescence) method. However, an accurate concentration field at a given cross-plane in a micro-channel has not been successfully achieved so far due to various limitations in the light illumination and fluorescence signal detection. The present study demonstrates a novel method to provide an ultra-thin laser sheet beam having 5 μm thickness using a micro-focus laser line generator. The laser sheet beam illuminates an exact plane of concentration measurement field to increase the signal-to-noise ratio and considerably reduce the depth uncertainty.Nile Blue A was used as fluorescent dye for the present LIF measurement. The enhancement of the fluorescent intensity signals was performed by a solvent mixture of water (95%) and ethanol (EtOH)/methanol (MeOH) (5%) mixture. To reduce the rms errors resulting from the CCD electronic noise and other sources, an expansion of grid size was attempted from 1×1 to 3×3 or 5×5 pixel data windows and the pertinent signal-to-noise level has been noticeably increased accordingly. 相似文献
5.
Determination of the rheological behavior of the polymer melt within micro-structured geometry is vital for accurate simulation modeling of micro-molding. The lack of commercial equipment is one of main hurdles in the investigation of micro-melt rheology. In this study, a melt viscosity measurement system for POM melt flowing through micro-channels was established. For measured pressure drop and volumetric flow rate, both capillary and slit flow models were used for the calculation of viscosity. The calculated results were also compared with those of PS resin to discuss the effect of morphology structure on the viscosity characteristics of polymer within micro-channels. It was found that the measured POM viscosity values in the test ranges are significantly lower (about 29-35% for a channel size of 150 μm) than those obtained with a traditional capillary rheometer. Meanwhile, the percentage reduction in the viscosity value and the ratio of slip velocity relative to mean velocity all increase with decreasing micro-channel size, but less significantly when compared with PS resin. In the present study we emphasize that the rheological behavior of the POM resin in microscopic scale is also different from that of macroscopic scale as PS resin but displays a less significant lower. It also revealed that the wall slip occurs more easily for the PS resin within micro-channels than POM resin due to enlarge the effect of molecular weight. 相似文献
6.
Bubble generation and transport in a micro-device composed of a micro-T-junction and a following serpentine micro-channel was experimentally investigated. It has a rectangular cross-sectional with an aspect ratio of 7.425. Air and water were used as gas and liquid, respectively. Mixtures of water–glycerol and water–Tween-20 were used to study the effects of liquid viscosity and surface tension. Compared with previous T-junction bubble generation, the liquid and gas inlets orientation was switched in this work. The continuous flow was driven from the perpendicular channel and the dispersion flow was from the main channel. It shows that the break-up process has three periodic steps under certain operating conditions. The dimensionless bubble length L/w in the micro-channel with high aspect ratio is much larger than that in square microchannels. A correlation is proposed to correlate L/w with liquid flow rate JL, gas flow rate JG, and liquid viscosity μL. Surface tension σ can change the bubble shape but almost does not affect the bubble length in this fast break-up process. Additionally, a long bubble may be broken up at the corners at the same time because the locations of gas and liquid are exchanged relative to the concave and convex portions of an elbow after a turn which may result in the change of fluid velocities and gas–liquid pressure drop. 相似文献
7.
基于神光Ⅱ物理实验,研究了X射线分幅相机中真空弧放电对荧光屏和微通道板的损害。通过观测放电点在荧光屏上的位置和输出强度,发现X射线分幅相机存在的3种弧放电形式:散弧、强弧和定弧,由弧点位置和强度的时空变化比较了3种放电形式对器件的损害程度和对相机工作状态的影响。散弧在一定真空度条件下具有很好的稳定性,并且微放电不影响XFC正常性能;强弧的屏输出强饱和,MCP和荧光屏被一次性损害,相机无法正常工作;定弧对相机的正常工作没有影响,放电在两种屏压加载下都表现出稳定的趋向。由场致电子发射理论解释了放电机理,分析了弧放电损坏的稳定性,由实验结果推导了定弧的场增强因子。 相似文献
8.
The role of structural heat exchange and heat loss in the design of efficient silicon micro-combustors 总被引:1,自引:0,他引:1
The performance of millimeter-scale combustors intended for miniaturized power and propulsion systems is strongly influenced by heat exchange to and within the combustor structure. Accordingly, a one-dimensional model with full chemistry that includes heat exchange to and within the combustor wall has been developed. It is used to study the effects of axial heat transfer from the post-flame to the pre-flame via wall conduction in a silicon micro-channel combustor with planar symmetry. The simulations show that axial heat transfer widens stability limits, increases the burning rate, and can enable the construction of smaller, higher power density combustors. Axial heat transfer also enhances the benefits of operating at elevated pressures. The simulations also show that heat loss to the environment places a lower bound on the combustor volume. Maximum power density combustor configurations are identified under adiabatic and non-adiabatic conditions. The maximum power density tends to increase with increasing pressure while the micro-channel length and height associated with the maximum tend to decrease. 相似文献
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10.
Simulation of forced convection of FMWNT-water (functionalized multi-walled carbon nano-tubes) nano-fluid in a micro-channel under a magnetic field in slip flow regime is performed. The micro-channel wall is divided into two portions. The micro-channel entrance is insulated while the rest of length of the micro-channel has constant temperature (TC). Moreover, the micro-channel domain is exposed to a magnetic field with constant strength of B0. High temperature nano-fluid (TH) enters the micro-channel and exposed to its cold walls. Slip velocity boundary condition along the walls of the micro-channel is considered. Governing equations are numerically solved using FORTRAN computer code based on the SIMPLE algorithm. Results are presented as the velocity, temperature, and Nusselt number profiles. Greater Reynolds number, Hartmann number, and volume fraction related to more heat transfer rate; however, the effects of Ha and ϕ are more noteworthy at higher Re. 相似文献