Electrostatic precipitator pre-filter for electrohydrodynamic fluid mover

Abstract

Electrostatic precipitation is performed upstream of collector electrode surfaces toward which a downstream EHD fluid mover accelerates fluid flow. In this way, the upstream electrostatic precipitator (ESP) acts as a pre-filter (with low flow-impedance) and can reduce accumulation of otherwise detrimental materials on downstream electrodes and / or arcing. In some cases, pre-filtering by an upstream electrostatic precipitator may also reduce accumulation of otherwise detrimental materials on downstream heat transfer surfaces and / or ozone catalytic or reactive surfaces / materials. In some embodiments, an EHD fluid mover with an ESP pre-filter is used in a thermal management system to dissipate heat generated by a thermal source.

Description

BACKGROUND[0001]1. Field[0002]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 heat transfer solution.[0003]2. Related Art[0004]Devices built to exploit ionic movement of a fluid are variously referred to in the literature as ionic wind machines, electric wind machines, corona wind pumps, electro-fluid-dynamic (EFD) devices, electrohydrodynamic (EHD) thrusters, EHD gas pumps and EHD fluid or air movers. Some aspects of the technology have also been exploited in devices referred to as electrostatic air cleaners or electrostatic precipitators.[0005]When employed as part of a thermal management solution, an ion flow fluid mover may result in improved cooling efficiency with reduced vibrations, power consumption, electronic device temperatures...

AI Technical Summary

Benefits of technology

[0011]As before, corona discharge-type devices provide a useful descriptive context, it will be understood (based on the present description) that other ion generation techniques may also be employed. Techniques such as silent discharge, AC discharge, dielectric barrier discharge (DBD), or the like, may also be employed to generate ions that, in turn, impart charge to entrained particulates and thereby facilitate filtration or precipitation the charged particulates from the fluid flow.

[0012]Thus, EHD devices may be employed to motivate ESP pre-filtered 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 with ESP pre-filtration can operate silently (or at least comparatively so) with reduced volume and mass. In some cases, products incorporating EHD device solutions with ESP pre-filtration may be thinner and lighter than those employing conventional forced air cooling technologies. Furthermore, flexible form factors of EHD and ESP devices can facilitate compelling product designs and, in some cases, may provide functional benefits. More specifically, it has been discovered that, in some EHD device configurations, upstream pre-filtration of a fluid flow using an electrostatic filter or precipitator may reduce accumulation of detrimental material on electrode surfaces of the downstream EHD device.

[0013]In some embodiments of the present invention, an apparatus includes a fluid flow path, an electrohydrodynamic (EHD) fluid mover introduced in the fluid flow path and operable to motivate fluid flow therealong and an electrostatic precipitator. The electrostatic precipitator precedes the EHD fluid mover in the fluid flow path and is operable to prevent a substantial amount of particulate matter otherwise entrained in the fluid flow from reaching at least the collector electrode surfaces of the EHD fluid mover. In some embodiments, heat transfer surfaces are introduced in the fluid flow path downstream of the electrostatic precipitator to transfer heat to or from the fluid flow.

[0018]In some embodiments in accordance with the present invention, a method includes (i) motivating fluid flow using an electrohydrodynamic (EHD) fluid mover introduced in a fluid flow path; and (ii) upstream of the electrohydrodynamic (EHD) fluid mover, electrostatically precipitating from the fluid flow a substantial amount of particulate matter otherwise entrained therein and thereby preventing the electrostatically precipitated particulate matter from reaching collector electrode surfaces of the EHD fluid mover. In some embodiments, the method further includes transferring heat to or from the fluid flow using heat transfer surfaces introduced in the fluid flow path downstream of the electrostatic precipitating.

[0021]In some embodiments in accordance with the present invention, an apparatus includes an enclosure and a thermal management assembly for use in cooling one or more devices within the enclosure. The thermal management assembly defines a flow path for conveyance of air between ventilated boundary portions of the enclosure. The thermal management assembly includes an electrohydrodynamic (EHD) fluid mover introduced in the flow path and operable to motivate air flow past heat transfer surfaces thermally coupled to the one or more devices within the enclosure and an electrostatic precipitator preceding the EHD fluid mover in the flow path. The electrostatic precipitator operable to prevent a substantial amount of particulate matter otherwise entrained in the air flow from reaching the EHD fluid mover.

[0022]In some embodiments, a repelling electrode is positioned between an emitter electrode of the EHD fluid mover and collection surfaces of the electrostatic precipitator. In some embodiments, a collector electrode of the electrostatic precipitator allows the air flow to transit therethrough.

Problems solved by technology

However, in many EHD devices and / or operating environments, detrimental materials such as silica dendrites, surface contaminants, particulate or other debris may accumulate or form on electrode surfaces and may decrease the performance, efficiency and lifetime of such devices.

Build-up of such detrimental materials can decrease power efficiency, cause sparking or reduce spark-over voltage and contribute to device failure.

In general, detrimental material build up may affect any number of surfaces including emitter and / or collector electrode surfaces involved in the motivation of fluid flow.

However, because elevated levels of ozone have been associated with certain health issues, ozone emission can be subject to strict regulatory limits such as those set by the Underwriters Laboratories (UL) or the Environmental Protection Agency (EPA).

In some cases, detrimental material build up can interfere with catalytically or reactively techniques employed to reduce ozone concentrations or even contribute, e.g., through sparking, to ozone production.

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