Electrohydrodynamic (EHD) conduction pumps have been investigated in theoretical and experimental studies. In general, EHD pumps contain no moving parts. They generate pressure gradients and/or flows in dielectric liquids via any of a variety of interactions between (1) applied electric fields and (2) free and/or bound electric charges in the liquids. Like a related prior device denoted an EHD ion-drag pump, an EHD conduction pump exploits interactions with free charges in liquids, but unlike an ion-drag pump, a conduction pump functions without direct injection of electric charges into the liquid. In the absence of direct injection, EHD conduction pumps are the only EHD devices that can pump isothermal liquids. EHD conduction pumps could be suitable for use as compact, low-power-consumption pumps to enhance flows and thus heat-transfer rates in heat pipes and capillary-pumped loops.
In an EHD conduction pump, an electric field is applied to a dielectric liquid through electrodes that are made either flat or else rounded with large curvatures and without sharp points so that there are no electric-field concentrations large enough to give rise to direct injection of charges. Figure 1 depicts salient aspects of the theory of operation in simplified form. Instead of free charges introduced through direct injection, an EHD conduction pump utilizes free charges in thin heterocharge layers formed in the vicinities of the electrodes through dissociation of molecules within the liquid and recombination of the resulting ions. In order to take advantage of the pumping effect of the heterocharge layers, an EHD pump must also utilize the residual small electrical conduction through the bulk of the otherwise nominally purely dielectric liquid.
Experiments on static-pressure EHD conduction pumps containing three different electrode configurations, using refrigerant 123 (dichlorotrifluoroethane) as the working fluid, have demonstrated the feasibility of this pumping concept. The best performance, observed in the case of a pump containing five hollow-central-electrode/ ring-outer-electrode pairs similar to the pair shown in Figure 2, was characterized by a maximum static pressure of 1,034 Pa at an applied potential of 20 kV and a maximum power consumption of 0.57 W.
This work was done by Jamal Seyed-Yagoobi, James E. Bryan, S. I. Jeong, and Y. Feng of Texas A & M University and P. Atten and B. Malraison of LEMD, CNRS (Grenoble, France) for Glenn Research Center.
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