Evaluation of the performance of a valveless micropump by CFD and lumped-system analyses

Abstract

The flow in a valveless micropump is analyzed using both the CFD method and the lumped-system method. In the multidimensional simulation of the CFD model, the Navier-Stokes equations are solved using a finite volume method suitable for the use of unstructured grids. The moving membrane is modeled by imposing a reciprocating velocity boundary condition. It is seen that a good agreement with measurements can be obtained for various back pressures by adopting an appropriate membrane shape blending the parabolic and the trapezoidal profiles. The multidimensional predictions serve as benchmark solutions to the lumped-system analysis. In the latter analysis two correlations for the loss coefficients of the nozzle and the diffuser are employed. The results show that with a more accurate one of the two correlations, a better agreement with the multidimensional calculations is yielded. The performance of the pump can be evaluated by considering the pumping efficiency. The pumping efficiency can be approximately formulated in two different ways, depending on the average ratios of the outlet flow rate to the inlet flow rate in the pumping and supply stages. In the averaging process to determine the mean ratios, the transient region between the pumping stage and the supply stage is excluded. This leads to even closer agreement to the multidimensional calculations in the pumping efficiency. (C) 2008 Elsevier B.V. All rights reserved.