In this paper, we present an analysis of the performance of micronozzle/diffusers and we report on the fabrication and testing of a micronozzle/diffuser. We have found that the pressure loss coefficient for the nozzle/diffuser decreases with the Reynolds number. At a given Reynolds number, the pressure loss coefficient for the nozzle is higher than that of the diffuser due to a considerable difference in the momentum change. We find that the nozzle/diffuser length has little influence on the pressure loss coefficient. At a fixed volumetric flow rate, we encounter a ‘minimum’ phenomenon of the pressure loss coefficient versus nozzle/diffuser depth. This is related to the interactions of velocity change and friction factor. In this work, we find good agreement between the measured data and the predicted results, except for a diffuser having an opening angle of 20°. This is because of the presence of flow separation. The departure of this case from the prediction is due to the separation phenomenon in a diffuser with a larger angle.

This study numerically examines the performance of micro nozzle/diffuser pumps subject to parallel and series combinations. For a single-chamber micro nozzle/diffuser micro-pump, four stages are identified. For dual micro-pumps in a parallel combination, the flow field in each chamber is symmetrical about the center line of the arrangement. For in-phase operation, the maximum flowrate is about two times higher than that of the single-chamber. For micro-pumps in a series combination, it is found that the overall performance is strongly related to the phase angle. The effective flowrate can be significantly increased, decreased, or even reversed. This indicates that the flowrate can be controlled within a wide span by changing the phase angles. At a phase angle of 90°, an eight-fold increase of effective flowrate is seen relative to that of a single-chamber operation. The significant increase of flowrate is attributed to two effects; the first effect is due to the "active valve" effect that increases the efficiency during pump mode. The second influence is attributed to the increased pressure difference that brings in more fluid during supply mode.

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In this study, an analysis of the performance of micro nozzle/diffusers is performed and fabrication of the micro nozzle/diffuser is conducted and tested. It is found that the pressure loss coefficient for the nozzle/diffuser decreases with the Reynolds number. At a given Reynolds number, the pressure loss coefficient for nozzle is higher than that of the diffuser due to considerable difference in the momentum change. For the effect of nozzle/diffuser length on the pressure loss coefficient, it is found that the influence is rather small. At a fixed volumetric flowrate, a “minimum” phenomenon of the pressure loss coefficient vs. nozzle/diffuser depth is encountered. This is related to the interactions of velocity change and friction factor. Good agreements of the measured data with the predicted results are found in this study except at a diffuser having an opening angle of 20° . It is likely that the departure of this case to the prediction is due to the separation phenomenon in a larger angle of the diffuser.