Patent Application
20150129174
This invention deals generally with heat transfer, and more particularly with heat plates and/or heat pipes used in transferring heat away from one or more heat-generating components.
Proper thermal management is critical to the successful operation of many types of devices. In this respect, modern jet aircraft include numerous types of devices which generate significant heat during operation, including avionic electronics, radar and directed-energy systems. As an example, avionics components commonly use integrated circuits (hereinafter called “chips” for convenience) for computing applications which can generate significant heat during operation.
Various techniques are known for transferring heat away from devices and/or their components during operation, to keep the devices functioning properly. For example, heat plates are commonly used to transfer heat away from the tops of the chip(s) in an avionics module toward the module's edge (e.g. to one or more side walls). Often a thermal interface transfers heat from the edge to a chassis, which is often a cooled component in which the module resides.
Heat plates commonly employ heat pipe technology. A heat pipe is a closed vessel which stores fluid in two states, or phases (i.e., liquid and gas), and which makes use of changes between the states to transfer heat. In some heat pipes, a volume of liquid is stored in the heat pipe at a given temperature, and then a vacuum is imposed in the vessel. The vessel is then sealed, so that the pressure level within the vessel causes some of the liquid to change to a gaseous state. The two-phase system inside the vessel remains at equilibrium, meaning that the boiling point and condensation point of the fluid in the vessel are at approximately the system's temperature. If heat is then absorbed at a particular location on the vessel, the heat causes liquid stored at that location to boil and be converted to gas, the heat being transferred to the gas, and pressure in the system increasing. A pressure increase causes the condensation point to increase as well, so that condensation begins occurring almost immediately at a different location in the heat pipe, typically where it is coolest, so that heat is transferred from the gas within the vessel to the external environment near the cool location. The liquid which results from this condensation transfers from the cool location back to the heated region (e.g., via a wick, one or more micro-grooves, and/or other mechanism(s)) so that the evaporation-and-condensation cycle can begin again.
Within a heat pipe, heat is transferred at approximately sonic speed from a heated location to a cooled location. As such, if a heat pipe is long enough to transfer heat a sufficient distance away from a heated location of a component, the heat pipe can effectively cool the component, without the need for any auxiliary pumping or moving parts.
The inventors have appreciated that employing heat plates to cool the numerous types of devices and components used in modern applications can present challenges. Components on modern jet aircraft serve as an illustrative example. On a modern jet aircraft, there may be dozens of different avionics modules, each having chips disposed at different locations within the module. In modules in which chips are attached to the module floor, different chips may be at different heights. To provide proper thermal management for all types of modules, a different heat plate may need to be separately configured to properly accommodate the location and height of the chips therein. In this respect, a heat plate is generally designed to come into intimate contact with the chips in a module so as to effectively transfer heat away, without applying so much pressure that any chip's operation is affected. As such, preparing a heat plate for use with a module usually involves configuring the plate to reach each of its chips at a particular height with great specificity. This is difficult to accomplish using conventional fabrication techniques.
One conventional approach to overcoming these difficulties is to employ a conformable, compressible thermal interface layer between each chip and the heat plate. In this approach, a thermal interface typically sits atop each chip, and contacts the heat plate when the heat plate is lowered into the module in which the chip resides. Because the thermal interface is conformable, the heat plate need not be configured to accommodate varying chip heights with great specificity. However, thermal interfaces are notoriously poor at conducting heat away from a chip, because they are typically made from materials which are highly conformable but not very thermally conductive. For example, many thermal interfaces cause about a 50% loss in thermal conductivity when compared with direct contact between a chip and a heat plate.
The inventors have recognized that other conformable materials which are more thermally conductive could be used in a thermal interface layer. For example, silver or copper pastes are both conformable and thermally conductive. However, the use of pastes can make module assembly problematic, because applying a paste on a set of chips having varying heights so that the paste atop each chip reaches the same height can be difficult. In addition, pastes are messy, and can therefore make module maintenance difficult.
In contrast to conventional approaches, some embodiments of the invention provide a heat plate system which includes a closed vessel having at least one flexible surface. The flexible surface allows the vessel to come into intimate contact with heat-generating components of varying heights. In some embodiments, the heat plate may be expandable during use (e.g., in response to being heated). As such, the heat plate may mold itself around the contours of different heat-generating components, increasing the surface area contact between the heat plate and the components, and increasing the heat plate's ability to conduct heat away from the components. In some embodiments of the invention, a heat plate may interface directly with one or more of the module's side walls, and/or a cooling mechanism. As a result, heat is transferred to the external environment via the module's periphery rather than through its cover, which may provide greater control and effectiveness with respect to thermal management than conventional approaches allow.
The foregoing is a non-limiting summary of the invention, some embodiments of which are defined by the attached claims.
The accompanying drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component that is illustrated in various figures is represented by a like numeral. For purposes of clarity, not every component may be labeled in every drawing. In the drawings:
Some embodiments of the invention provide a heat plate system which includes a closed vessel having at least one surface that is pliable and/or flexible, allowing the vessel to come into close contact with contoured surfaces of heat-generating components of varying heights, and enabling effective heat transfer away from those components. In some embodiments of the invention, a heat plate may be expandable, such as upon the absorption of heat, so as to increase the component surface area with which the heat plate system comes into contact, and thereby improving thermal conductivity. In addition, some embodiments of the invention may provide a heat plate system for use with heat-generating components residing in a module housing which is designed to conduct heat to the housing's peripheral walls and/or a cooling mechanism, rather than to the housing's cover, to provide greater control and effectiveness with respect to heat transfer than conventional systems provide.
In module 220, components 210A-210D reside on module floor 225. It should be appreciated, however, that embodiments of the invention are not limited to being used with components residing on the floor of a module, and may be used with components in any suitable location. For example, components may be elevated above a module floor, reside within a recess within a module's floor, be attached to one or more of the module's side walls, and/or reside in any other suitable location(s).
In module 220, periphery walls 215 define a cavity in which components 210A-210D reside. As explained further below, in some embodiments of the invention, one or more of walls 215 may contact, or otherwise be thermally coupled to, one or more external cooling components. For example, one or more of walls 215 may contact components through or over which cooling fluid (which may comprise any suitable gas and/or liquid) flows. It should be appreciated, however, that embodiments of the invention are not limited to being used in conjunction with modules having walls which contact external cooling components.
Arrow 230 in
In the example shown in
In the example shown in
In some embodiments, the material(s) from which heat plate 205 is formed may allow it to expand as it absorbs heat generated by module components, so that as heat is generated, bottom surface 315 is forced into more intimate contact with the components, increasing the surface area of heat plate 205 across which heat may be conducted.
Heat plate 205 may employ any of numerous types of fluids to perform heat transfer. The inventors have observed that fluids which transition without difficulty between liquid and vapor phases, and which expand when entering the vapor phase, may prove advantageous in certain applications. Examples of fluids exhibiting these characteristics include water, alcohol and paraffin. However, it should be appreciated that any suitable fluid(s) may be used, as embodiments of the invention are not limited in this respect.
It should also be appreciated that numerous advantages may flow from the example arrangements shown in
It should further be appreciated that the implementation examples described above are intended to be illustrative rather than limiting, and that numerous variations on these examples are possible. For example, embodiments of the invention may be used to transfer heat away from any suitable component(s), which may or may not include an integrated circuit. In addition, embodiments of the invention may be used in conjunction with any suitable collection of components, which may or may not include or comprise a functional module such as an avionics module. The collection of components may be of any suitable size and include any suitable quantity of components. Embodiments of the invention are not limited in this respect.
Having thus described several aspects of at least one embodiment of this invention, it is to be appreciated that various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be part of this disclosure, and are intended to be within the spirit and scope of the invention. Accordingly, the foregoing description and drawings are by way of example only.
Various aspects of the present invention may be used alone, in combination, or in a variety of arrangements not specifically discussed in the embodiments described in the foregoing and is therefore not limited in this application to the details and arrangement of components set forth in the foregoing description or illustrated in the drawings. For example, aspects described in one embodiment may be combined in any manner with aspects described in other embodiments.
Also, the invention may be embodied as a method, of which an example has been provided. The acts performed as part of the method may be ordered in any suitable way. Accordingly, embodiments may be constructed in which acts are performed in an order different than illustrated, which may include performing some acts simultaneously, even though shown as sequential acts in illustrative embodiments.
Use of ordinal terms such as “first,” “second,” “third,” etc. in the claims to modify a claim element does not by itself connote any priority, precedence or order of one claim element over another or the temporal order in which acts of a method are performed, but are used merely as labels to distinguish one claimed element having a certain name from another element having a same name (but for use of the ordinal term) to distinguish the claim elements.
Also, the phraseology and terminology used herein is used for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having,” “containing,” “involving,” and variations thereof herein, is meant to encompass the items listed thereafter and equivalents thereof as well as additional items.
