Design, testing and optimization of a micropump for cryogenic spot cooling applications

The performance of two micropumps with different electrode designs in liquid N₂ was investigated in this study. One of the experimental challenges was developing a method for measuring the flow rate of the liquid N₂. By combining a numerical model of the non-isothermal flow of the liquid N₂ around the loop and the experimental measurements of the temperatures around the flow loop, the liquid N₂ flow rates could be determined accurately enough to compare the pumping performance of these micropumps. The first tested micropump had an electrode spacing of 20 μm and an electrode pair spacing of 80 μm, while the second pump had an electrode spacing of 50 μm and electrode-pair spacing of 200 μm. The results showed that both micropumps pumped sufficient liquid N₂ to cool a typical superconductive sensor or other low power device. For both pumps, the pumping capacities increased with increasing EHD voltage. The pump with the smaller electrode spacing generated a higher flow rate at a lower applied voltage. This pump generated flow rates as high as 10 mL/min at an applied voltage of 500 V.