Collector electrodes and ion collecting surfaces for electrohydrodynamic fluid accelerators

Abstract

Embodiments of electrohydrodynamic (EHD) fluid accelerator devices utilize collector electrode structures that promote efficient fluid flow and reduce the probability of arcing by managing the strength of the electric field produced at the forward edges of the collector electrodes. In one application, the EHD devices dissipate heat generated by a thermal source in a thermal management system.

Description

CROSS-REFERENCE TO RELATED APPLICATION(S)[0001]The present application claims the benefit of U.S. Provisional Application No. 61 / 139,518, filed Dec. 19, 2008.BACKGROUND[0002]1. Field[0003]The present application relates to thermal management, and more particularly, to micro-scale cooling devices that use electrohydrodynamic (EHD, also known as electro-fluid-dynamic, EFD) technology to generate ions and electrical fields to control the movement of fluids, such as air, as part of a thermal management solution to dissipate heat.[0004]2. Related Art[0005]In general, electrohydrodynamic (EHD) technology uses corona discharge principles to move fluids (e.g., air molecules). Basic principles of EHD fluid flow are reasonably well understood by persons of skill in the art. Accordingly, a brief illustration of corona discharge principles in a simple two electrode system sets the stage for the more detailed description that follows.[0006]With reference to the illustration in FIG. 14, corona di...

AI Technical Summary

Benefits of technology

[0009]EHD devices may be employed to motivate flow of air in a thermal management system, such as when employed to exhaust heat dissipated by integrated circuits in computing devices and electronics. For example, in devices such as laptop computers, compact scale, flexible form factor and absence of moving parts can provide design and user advantages over conventional forced air cooling technologies that rely exclusively on fans or blowers. EHD device solutions can operate silently (or at least comparatively so) with reduced volume and mass. In some cases, products incorporating EHD device solutions may be thinner and lighter than those employing conventional forced air cooling technologies. Flexible form factors of EHD devices can facilitate compelling product designs and, in some cases, may provide functional benefits.Fluid Permeable Ion Collection Surfaces

[0010]It has been discovered that, in some EHD device configurations, a fluid-permeable ion collection surface may be provided to promote development of a generally uniform electric field distributed over downstream ion collection surfaces. Accordingly, in some embodiments of the present invention, an apparatus includes an emitter electrode and a collector-radiator assembly including a fluid permeable ion collection surface and an array of heat transfer surfaces extending downstream of the emitter electrode. The fluid permeable ion collection surface spans a major dimension of the heat transfer surface array. The emitter electrode and the collector-radiator assembly are energizable to motivate fluid along a flow path through the fluid permeable ion collection surface and over the heat transfer surfaces of the collector-radiator assembly.

[0016]It has been further discovered that, in some EHD device configurations, ion collection surfaces may extend upstream of an emitter electrode so as to at least partially surround the emitter. In some cases, such a configuration may protect the emitter from mechanical intrusions and / or human contact with a high voltage emitter. In some cases, such a configuration may tend to shield other electrical components from unwanted electric fields and ion bombardment. In some cases, surface conditioning or coating of upstream surfaces may facilitate accumulation and retention of a surface charge that tends to repel ions from the upstream surfaces.

[0022]It has been further discovered that, in some EHD device configurations, ion collection surfaces most closely proximate to an emitter electrode may be preferentially conditioned or coated with a highly-resistive surface. In this way, electrical fields may be advantageously shaped and spark limiting or quenching mechanisms may be provided while still facilitating efficient heat transfer at other downstream surfaces. In some cases, surface conditioning or coating of upstream surfaces may be insulative so as to facilitate accumulation and retention of a surface charge that tends to repel ions from the upstream surfaces.

[0026]In some embodiments, the apparatus is configured as a thermal management assembly, wherein the collector electrodes constitute convective heat transfer surfaces. In some embodiments, the apparatus is configured as a thermal management assembly, wherein the motivated fluid flow is over at least some convective heat transfer surfaces distinct from the collector electrodes. In some embodiments, the emitter electrode and the collector electrodes are operatively coupled between terminals of a high voltage source to establish a corona discharge therebetween and to thereby motivate the fluid in the downstream direction.

Problems solved by technology

In some cases, such a configuration may tend to shield other electrical components from unwanted electric fields and ion bombardment.

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