In the present study, a 3-dimensional model was developed to investigate fluid flow in MHD micro-pumps. Initially, 3D governing equations were derived and numerically solved using the finite volume method/SIMPLE algorithm. The case study was a (MHD) micropump built in the year 2000 (channel length: 20mm, channel width: 800μm, channel height: 380μm and electrode length: 4mm). The applied magnetic flux density was 13mT and the electric current was different for various solutions (10 ~ 140mA). The numerical results were verified by experimental and analytical data for several solutions. In addition effects of magnetic field strength, electric current, geometrical parameters of the MHD micropump, electrode length and electrode location on its performance have been investigated. Finally the results has been considered and discussed.

In the present study, the effect of the number of stages of Tesla Micro-Valve (TMV), as well as the dependency of Reynolds number, Re, on the valve performance has been analyzed. For this purpose, different layouts include one to four-stage with different sizes are investigated numerically. The main criterion for evaluation of valves performance is diodicity, Di. Unsteady and steady flow in valve have been simulated and compared. It is shown that although there are some difference but the trend is similar for both responses. Finally, 2-D and steady state computations of the fluid flow have been utilized that reveal a strong dependence of Di on Re and pressure drop, ΔP. The results showed that the maximum Di of the two-stage microvalve is approximately 1.45 times of that of one-stage. Additional stages increase the complexity, and they do not change Di appreciably. It is concluded that two-stage layout of Tesla type valve is the best option. Also, the two-stage valve performance for three different sizes is compared with Nozzle-Diffuser type Micro-Valve (NDMV). Comparisons, which are performed based on calculation Di in applicable range of Re, showed that Di as a function of Re is independent of the valve size. Also, the superiority of the Tesla type valve at higher Re and its weakness at lower Re is observed.

The no-moving-part valve (NMPV) pump design has been proven to be a better micro pump design for its easier fabrication, cost-effective and no destroying flow particle. Previous literatures often used a diffuser design with a divergent angle for NMPV studies. Different from previous studies, we apply a convergent-divergent (C-D) nozzle with convergent half angle θ1 and divergent half angle θ2 for NMPV design in this study. By using the dipole value (Dip) of current C-D nozzle type NMPV as an objective function in “Design of Experiments” (DOE) and “Response Surface Modeling” (RSM) optimization methods, C-D nozzle type NMPV with convergent half angles near θ1 = 46° ∼ 54° and divergent half angles θ2 = 113° ∼ 116° has a maximum peak region for Dip value. It is found that the optimal design with the convergent half angle of θ1 = 60° and the divergent half angle of θ2 = 110°. The operational Reynolds numbers raging from 20 to 30 are suggested for the optimal design and operation condition for the current C-D nozzle type NMPV. It is also verified that the C-D nozzle type NMPV pump design has a better performance than the typical diffuser type NMPV pump design. These findings would be useful to the design and operation for C-D nozzle type NMPV micropump.

A numerical analysis of the unsteady flows in conical microdiffusers appropriate for valveless micropump applications is performed. The rectification efficiency of the diffuser valve is calculated directly as a function of geometric and operational parameters, including diffuser angle, diffuser slenderness, sizes of actuation chamber and inlet/outlet port, actuation frequency, and amplitude of actuation pressure. The computational results show that the diffuser with diverging angle of 10° and slenderness of 7.5 has the best rectification performance. For large actuation pressure amplitude, the optimal rectification efficiency and its corresponding Roshko number are relatively high. At the optimal Roshko number, the flow impedance is found to be dominated by fluid inertia. Sizes of the pump chamber and inlet/outlet port are shown to have a prominent effect on valve performance. Small actuation chamber or small inlet/outlet port can significantly deteriorate the valving performance of the diffuser.