Patent Application
20110261122
Thermal management in electronic devices presents critical issues. High heat environments generally degrade the performance and efficiency of electronic devices, resulting in higher power consumption. Additionally, the heat generated by the devices can cause the environment around them to have higher temperatures, requiring more energy to cool them. For entities desiring to obtain efficiencies ratings, such as the EnergyStar® endorsements, the management of the heat becomes a critical issue.
One approach to thermal management uses thermal insulators in the devices to absorb and contain the heat generated by the devices. Aerogels perform very well as thermal insulators. An aerogel generally consists of a manufactured material derived from a “gel”, but where air or other gas replaces the liquid component of the gel. The resulting aerogel solid has very low density riddled with nanopores near the mean free path of air molecules, trapping them, stopping heat transfer (or other energy transfer) between them. It generally feels dry and rigid to the touch, but has very high effectiveness as a thermal insulator. Silica based aerogels in particular make very efficient thermal insulators as they are 95-99.8% air and the remainder is the silica nanostructure.
Aerogels generally perform better after application of a vacuum prior to heat sealing the insulation ‘bag’ or container. However, vacuum sealing aerogel-based insulation often fails. Upon application of the vacuum, the aerogel produces particles that enter the vacuum stream and contaminate the heat seal. The resulting heat seal either does not seal or will not hold upon usage. While one could use the insulating materials without using a vacuum, these materials work far more effectively if they undergo a vacuum
Several advantages exist in the use of aerogels as insulating materials. These materials have very good thermal conductivity and users can shape or mold them to a desired shape in many instances. When one applies a vacuum to the silica aerogel, the thermal conductivity decreases as shown in
A more material specific graph is shown in
The data associated with the graph is given in the following table:
The use of a relatively high vacuum increases the effectiveness of aerogels with regard to their thermal conductivity. However, as discussed above, these materials generate a relatively high volume of particles when a vacuum is applied, resulting in contamination of the seal when the container, such as a bag, pouch, or container, is sealed.
This filter is inserted or otherwise wrapped with a sealable material or container, such as a heat sealable bag. The bag or container may take any form, the only limitation being that it has to contain the filter and the material within the filter and be sealable. Once the filter and its enclosed insulation material are enclosed with the sealable container, a vacuum is applied. The container 26 is then sealed. Typically, this will be a heat seal, but other types of seals are of course possible, including adhesives, airtight fasteners or gaskets, etc. The main characteristic of the seal is that it be airtight, especially in the presences of a relatively high vacuum.
The application of this type of insulator may occur in many different environments, including buildings, vehicles, machinery, apparatus, and electronic or other devices that require thermal management. One particular example of these devices consists of a solid ink jet printer. Solid ink printers use an ink supply in the form of solid sticks of color or black. The printer melts the ink into a reservoir and then passes the ink to a print head. Generally, the conduits and the print head are themselves heated to prevent the ink from re-solidifying. These types of printers generate high levels of heat and thermal management becomes more important than in lower heat devices. The example of a printer is merely an example and is not intended to limit the claims or application of the embodiments in any way.
The printer 30 has an ink reservoir 36 into which the solid ink sticks will melt. A conduit 38 provides the ink to the print head 32. The print head 32 has a nozzle or aperture plate 34 that ejects ink onto a print substrate. A controller or processor 40 determines whether or not a particular nozzle ejects ink onto the print substrate, based upon image data. The pattern of drops of ink forms the desired image represented by the image data.
As mentioned above, many of the components of solid ink printers are heated to keep the ink in its molten state, generating quite a bit of heat. Insulators become very important in managing the heat. In the example of
While this is just an example of the insulation used in electronic devices, printer 30 does illustrate the use of insulation and highlights the need for good thermal conductivity within devices. Using silica aerogels in a vacuum provides that thermal conductivity. The embodiments here avoid the contamination of the seal that previously caused problems, allowing the seal to hold for much longer at higher vacuums.
Prior to using techniques discussed here, the aerogels generate a high volume of particles that get pulled into the vacuum stream and contaminate the surface of the sealing portions of the container. Once sealed, the seals did not work well, often failing in a matter of minutes. However, upon containing the insulation material in a filter and then sealing the filter into the container, the seals have held for months.
In this manner, one can have the advantages of using aerogels under vacuum as insulators while not suffering the consequences of their high particle generation. The embodiments described here allow for customizable sizes and shapes of insulators with good thermal conductivity with a relatively small adjustment in the manufacturing process.
It will be appreciated that several of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Also that various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.
