Flow Regime Identification of Horizontal Two Phase Refrigerant R-134a Flow Using Neural Networks

Flow regime Identification is an integral aspect of modeling two phase flows as most pressure drop and heat transfer correlations rely on a priori knowledge of the flow regime for accurate system predictions. In the current research, two phase R-134a flow is studied in a 7mm adiabatic horizontal tube over a mass flux range of 100–400 kg/m2s between 550–750 kPa. Electric Capacitance Tomography results for 196 test points were analyzed using statistical methods and neural networks. This data provided repeatable normalized permittivity ratio signatures based on the flow distributions. The first four temporal moments from the mean scaled permittivity data were utilized as input variables. Results showed that only 80 percent of flow regimes could be correctly identified using seven flow regime classifications. However reducing to five more commonly used regimes resulted in an improvement to 99 percent of the flow regimes correctly identified. Both methods of neural network training resulted in errors that were off by mostly one flow regime classification. Further analysis shows that transition cases can oscillate between two separate flow regimes at the same time.

The Effect of Flow Pulsation on Ultrafiltration System Limiting Flux Behavior

Ultrafiltration (UF) is an important industrial operation and is found in the food industry, separation of oil-water emulsions, treatment effluents from the pulp and paper industry, and environmental protection systems. Despite being widely used in these areas, UF systems exhibit a limiting flux behavior caused by concentration polarization on the membrane surface. Concentration polarization can be severe in macromolecular solutions due to low diffusivity on membrane separation and both mechanical and chemical methods have been used to reduce this phenomenon. This study introduces a new mechanical method that improves the performance of membrane separation and decreases concentration polarization. It involves pulsing the feed flow discontinuously and based on our results, feed flow velocity and solution bypass/membrane filtration time ratio are two vital factors when it comes to improving permeate flux. The proposed method is expected to find wide application, particularly in the processing of macromolecular solution.

Effect of Charge Distribution at the Three Phase Contact Line for an Electrolyte Drop

In this paper, we obtain the velocity field in a wedge in a Three Phase Contact Line (TPCL) in an electrolyte drop which is evaporating on a charged solid. Combination of an electrolyte solution and the charged surface leads to the formation of an Electric Double Layer (EDL), which in presence of the evaporation-triggered pressure-driven transport, leads to the generation of a streaming current that causes an electrokinetic transport. Hence, we analyze for the first time an electrokinetic transport in a charged wedge in presence of an evaporation-induced advective flux. Our results exhibit flow patterns that are distinctly different as compared to that of the case where there is no such electrokinetic transport and the problem is merely that of evaporation in a wedge.

A Gravity Driven Microfluidic Platform for DNA Enrichment

There is currently considerable interest in the development of microfluidic based lab-on-chip devices for sample preparation in next generation sequencing. One of these steps is DNA enrichment which often relies on conventional PCR to amplify the sample to detectable levels. To successfully automate this step, technologies are required whereby the samples are selectively inputted, thermocycled and selectively dispensed, all non invasively and therefore leading to no contamination issues. In this study such a system was created through the use of liquid-liquid plugs flowing in a gravity driven siphon. Plug generation was achieved through an innovative approach whereby a hydrophobic tube was traversed between two immiscible fluids (silicon oil and PCR reagents) and successful amplification was shown for Beta-2-Microfloblin (B2M).

Design, Simulation and Development of Gold Microneedles Patch

Technological advancements are essential for all fields of life particularly in health discipline to test and analyze the biological and biomedical samples. Biological micro electromechanical system (Bio-MEMS) based healthcare technologies are handy to make human life comfortable and snug by ease of use, eradicating pain, reducing risk of diseases, improving diagnosis process and treatments techniques. In this study the design, simulation and development of piezoelectricaly actuated microfluidic device (gold needle patch) has been presented. The simulation of skin insertion using gold needle into skin to study the effects of skin piercing and optimize the design of needle has been conducted in ansys autodyne by making 3D model with applied force 0.4 to 0.9 N at the tip area of needle. The microfluidic analysis of 3×3 microneedle patch has been carry out in ansys workbench using computational fluid dynamic (CFX) environment. The maximum velocity 2.015 e4 m/Sec has been achieved. After the successful development of gold needles patch, the fluid transport and insertion test of piezoelectricaly actuated patch also has been conducted using chicken skin.

Numerical Modeling of Fluidic Pumping in Micronetworks of Plants

Plant transport mechanisms are of interest in developing micropump for engineering devices. We present a two-dimensional phloem loading and transport model incorporating protein level mechanics with cellular level fluid mechanics. Governing Navier-Stokes, continuity, and Nernst-Planck equations are numerically solved to determine fluid flow and sugar transport. Phloem loading mechanics for active loading is incorporated through a six-state proton sucrose pump kinetic model. The influence of binding rates constants, concentrations, and membrane electrical potential differences on resulting sucrose transport is studied. Numerical results show that increasing rates of the sucrose transporter will noticeably increase outflow. Simulation result also show that a lower leaf sieve sucrose concentration improves outflow. In addition, a more negative membrane electrical potential difference will increase outflow. This numerical model offers insight on parameters that may be significant for implementing plant transport mechanisms in microfluidic devices.

Fully Lagrangian Modeling of Two-Phase Impulse Microjets

A new fully Lagrangian approach to numerical simulation of 2D transient flows of viscous gas with inertial microparticles is proposed. The method is applicable to simulation of unsteady viscous flows with a dilute admixture of non-colliding particles which do not affect the carrier phase. The novel approach is based on a modification and combination of the full Lagrangian method for the dispersed phase, proposed by Osiptsov [1], and a Lagrangian mesh-free vortex-blob method for Navier-Stokes equations describing the carrier phase in the format suggested by Dynnikova [2]. In the combined numerical algorithm, both these approaches have been implemented and used at each time step. In the first stage, the vortex-blob approach is used to calculate the fields of velocity and spatial derivatives of the carrier-phase flow. In the second stage, using Osiptsov’s approach, particle velocities and number density are calculated along chosen particle trajectories. In this case, the problem of calculation of all parameters of both phases (including particle concentration) is reduced to the solution of a high-order system of ordinary differential equations, describing transient processes in both carrier and dispersed phases. The combined method is applied to simulate the development of vortex ring-like structures in an impulse two-phase microjet. This flow involves the formation of local zones of particle accumulation, regions of multiple intersections of particle trajectories, and multi-valued particle velocity and concentration fields. The proposed mesh-free approach enables one to reproduce with controlled accuracy these flow features without excessive computational costs.

Numerical Research on Flow Field for Petroleum Tar Cutting Pump

In order to study the flow state and distribution of the solid particle in the flow field of petroleum tar cutting pump, the Computational Fluid Dynamic method was used to conduct the numerical simulation of liquid-solid two-phase flow based on Euler-Euler multiphase flow model and standard turbulence equation. The influence of flow rate, revolution speed and tilt angle of stator slot on streamline and distribution of solid concentration were analyzed. The result shows:strong swirl exists in inlet segment in small flow rate, but flow rate has little influence on the solid concentration, so it has no obvious influence on the cutting and grinding efficiency.Grinding efficiency could be improved by increasing revolution speed, but the requirement for the equipment would be higher, so the revolution speed should be determined reasonably. Reducing the tilt angle of stator slot is favor for improving the grinding and cutting efficiency, so it could provide some reference value for the optimal design.

An Experimental Study of the Effect of Drag Reducing Additive on the Structure of Turbulence in Concentric Annular Pipe Flow Using Particle Image Velocimetry Technique

The effect of drag reducing additive on the structure of turbulence in concentric annular pipe flow was investigated using Particle Image Velocimetry (PIV) technique. Experiments were conducted using a 9m long horizontal flow loop with concentric annular geometry (inner to outer pipe radius ratio = 0.4). The drag reducing additive was a commercially available partially hydrolyzed polyacrylamide (PHPA). The experiments were conducted using 0.1% V/V polymer concentration, giving a drag reduction of 26% at a solvent Reynolds number equal to 56400. Near wall local fluctuating velocity values were determined by analysing the PIV data. The root mean square (RMS) values of radial velocity fluctuations showed a significant decrease with the use of drag reducing additive. The RMS values of axial velocity fluctuations near the wall (Y+<10) were similar for both water and polymer fluid flow; though, higher peaks were obtained during the polymer fluid flow. As compared to water flow, a strong reduction in vorticity was observed during polymer fluid flow. The degree of vorticity reduction on the inner wall was higher than that of the outer wall. Results of the viscous dissipation and the shear production terms in the kinetic energy budget showed that less energy was produced and dissipated by the route of turbulence when using polymer fluid.

Aerodynamic Characteristics of Horizontal Axis Wind Turbine With Archimedes Spiral Blade

To investigate the aerodynamic characteristics of an Archimedes spiral wind turbine for urban-usage, both experimental and numerical studies were carried out. The Archimedes spiral blade was designed to produce wind power using drag and lift forces on the blade together. Instantaneous velocity fields were measured by two-dimensional PIV method in the near field of the blade. Mean velocity profiles were compared to those predicted by the steady state and unsteady state CFD simulation. It was found that the interaction between the wake flow at the rotor downstream and the induced velocity due to the tip vortices were strongly affected by the wind speed and resulting rotational speed of the blade. PIV measurements revealed the presence of dominant vertical structures at downstream the hub and near the blade tip. Unsteady CFD simulation results agreed well with those of PIV experiments than the steady state analysis. The power coefficient (Cp) obtained by CFD simulation demonstrated that the new type of wind turbine produced about 0.25, relatively high value compared to other types of urban-usage wind turbine.