Design Optimization of Valveless Micropump by Parametric Study of Diffuser/Nozzle angle and Aspect Ratio

Abstract

In this paper, the diffuser/nozzle based valveless micropump is modeled and analyzed numerically by using CFD commercial software (Fluent 6.2). Two (3-D) models are used for numerical calculations. In model-I, the uniform inlet velocity is applied as a boundary condition at lower wall (diaphragm) of chamber. The inlet velocity is modeled as a function of diaphragm deflection on the basis of experimental data. In model-II, the deflection of diaphragm is modeled as a moving wall and transient flux is calculated at inlet and outlet of the pump to predict the net flux. On the basis of numerical results, it is observed that the numerical results of both models agree well with the experimental results. Although the model-II is very close to the dynamic working conditions of pump but it demands a long computational time, hence model-I is preferred for further study to predict the optimized diffuser/nozzle angle and aspect ratio (length and throat width ratio). The maximum flow rate of 36.00 ?l/min is attained for diffuser/nozzle angle of 160 and aspect ratio of 12.75 under the conditions (zero back pressure, fluid type, chamber size, frequency & max deflection etc.) considered in 3-D model of valveless micropump. The effects of aspect ratio and back pressure on the optimized diffuser angle are also examined. Since under dynamic flow conditions, 3-D modeling (model-II) acquires a very long computational time, therefore another 2-D model is created to examine the effects of dynamic flow. In this model, the deflection of diaphragm is defined as a moving wall similar to model-II. 2-D model is also applied to see the effects of displacement of diffusers from the center of the chamber and chamber depth on the flow rate. The comparisons between steady (model-I) and dynamic flow conditions (2-D model) are also presented.