The mathematical model of a double chamber pump is obtained by dividing the problem in two separate ones. The first that considers inertia force and viscous loss in relation of actuation pressure and frequency is obtained, and then a model of the nozzle/diffuser elements is introduced. The value of the flow rate obtained from the first model is then introduced in the second to determine the loss coefficients starting from geometrical properties and flow velocity. Then the loss coefficients obtained are used in the first model to obtain a new value of flow rate. These two models have been implemented in a Matlab® code that numerically reaches convergence repeating the cycle above. Using this model is possible to predict performances of the micropump only from geometrical properties and actuation parameters, without assumptions about the loss coefficients. A similar model is obtained for a single-chamber pump with geometrical dimensions equal to each chamber of the double chamber pump, and the results from both the models are then compared for equal applied actuation pressure and frequency. Results gives for our pump a max flow working frequency that is about 30% lower than the single chamber design, with the same applied pressure on the membrane, same geometry of parts and materials, and a max flow rate that is about 140% of the single chamber max flow in max flow conditions. For lower frequencies flow rate is more than twice, and maximum membrane deflection smaller up to 20% less. These results can change due to geometrical and material properties. Finally the influences of every significant geometrical property on flow rate, maximum flow frequency, loss coefficients and membrane strain are examined, and the nozzle/diffuser initial width and chamber side length are founded to be the most important dimension.

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