Abstract
This study conducts an experimental study concerning the improvement of nozzle/diffuser micropump design using some novel no-moving-part valves. A total of three micropumps, including two enhancement structures having two-fin or obstacle structure and one conventional micro nozzle/diffuser design, are made and tested in this study. It is found that dramatic increase of the pressure drops across the designed micro nozzles/diffusers are seen when the obstacle or fin structure is added. The resultant maximum flow rates are 47.07 mm3/s and 53.39 mm3/s, respectively, for the conventional micro nozzle/diffuser and the added two-fin structure in micro nozzle/diffuser operated at a frequency of 400 Hz. Yet the mass flow rate for two-fin design surpasses that of conventional one when the frequency is below 425 Hz but the trend is reversed with a further increase of frequency. This is because the maximum efficiency ratio improvement for added two-fin is appreciably higher than the other design at a lower operating frequency. In the meantime, despite the efficiency ratio of the obstacle structure also reveals a similar trend as that of two-fin design, its significant pressure drop (flow resistance) had offset its superiority at low operating frequency, thereby leading to a lesser flow rate throughout the test range.
Highlights
Microscale pumping had received significant attention in industrial, medical, and biological applications such as lab-on-a-chip, fuel cells, high flux electronic cooling and biochemistry [1,2].Normally microvalves are employed in the micropumps to achieve a higher efficiency
The flow rate for the two-fin structure exceeds that of conventional design when the frequency is below 425 Hz, yet the trend is reversed when the frequency surpasses 425 Hz
The results shown in this figure denote that the micro nozzle/diffuser with added fins substantially outperforms the conventional design in the low flow rate region
Summary
Microscale pumping had received significant attention in industrial, medical, and biological applications such as lab-on-a-chip, fuel cells, high flux electronic cooling and biochemistry [1,2].Normally microvalves are employed in the micropumps to achieve a higher efficiency. Other considerations for micropumps, depending of specific applications, are drug compatibility, small size, power consumption, and flow rate controllability over a wide range of external conditions [6]. The design features easier flow controllability over a wide range of operating conditions at the expense of larger size and additional power consumption. Either active or passive valves are prone to clogging, wear, and fatigue which are always major issues for micro-pump applications. To tackle this problem, the novel concept of a valve-less diffuser pump was first proposed by Van De Pol [7]. Stemme and Stemme [5] later took the concept a step forward with a workable and practical micropump
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