Metal working – Method of mechanical manufacture – Heat exchanger or boiler making
Reexamination Certificate
1999-10-28
2001-04-03
Rosenbaum, I Cuda (Department: 3726)
Metal working
Method of mechanical manufacture
Heat exchanger or boiler making
C029S890054
Reexamination Certificate
active
06209200
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention generally relates to heat pipe devices and more particularly pertains to the improvement of such devices. Specifically, the improvements encompass enhanced heat transfer efficiency as well as increased mechanical strength, conformability to a wide variety of geometric configurations, a reduction of specific weight and volume and manufacturability at relatively low cost.
Heat pipes provide a heat transfer function with a structure that is wholly devoid of moving parts. Such devices generally include a combination of relatively large conduits and small capillary-like structures that extend between two surfaces, one such surface being adjacent a heat source and the other being adjacent a heat sink. A quantity of coolant is contained within the device wherein the coolant is selected so as to evaporate upon contact with the hot surface and condense upon contact with the cold surface. The conduits enable the transport of vaporized coolant toward the heat sink where it reassumes its liquid state while the capillary structure facilitates the return of the liquid coolant to the heat source by capillary action. The coolant is thereby available for the continuous repetition of the cycle.
Various structural configurations have been found to be effective as heat pipe devices including a fabricated honeycomb structure that is capped by faceplates and lined with mesh material. The interior space of each honeycomb cell functions as a vapor conduit while the mesh performs the function of a capillary-like structure to wick liquid coolant from the cold to the hot faceplate. Efforts to enhance the heat transfer capacity of such devices have typically entailed the substitution of various composite materials for the aluminum normally used in the construction thereof. Additionally, because such devices are often intended for applications with strict space and weight limitations, it is most desirable to minimize both their weight and volume. It is especially preferable to have the ability to wholly integrate a heat pipe device within structural components that are necessarily associated with a particular application. For example, a heat pipe structure integrated within the walls, struts, and/or shelves of a satellite could fulfill the heat transport/rejection requirements without taking up space or adding weight to the spacecraft. The feasibility of a particular heat pipe design for such applications not only depends upon its specific heat transfer capacity, both in terms of weight and volume, but also its configurability to a wide range of geometries and orientations. These capabilities must be available without compromise to the structural strength while the device must nonetheless be economical to manufacture. The previously known devices have been unable to adequately fulfill all these requirements simultaneously especially as necessitated in microsatellite applications.
SUMMARY OF THE INVENTION
The present invention provides a heat pipe device that is inherently strong and is extremely efficient in transferring heat from a hot to a cold surface. Moreover, the device is easily configured in a wide variety of geometries and orientations and is therefore readily integrated within structural components. Utilization thereof minimizes and can possibly eliminate parasitic weight and volume in some applications. The device is relatively economical to produce due in part to the minimal amount of tooling utilized in its manufacture.
More particularly, the heat pipe device of the present invention consists of a lamination of individually etched and perforated foil layers wherein perforations and etchings formed therein cooperate to define cells, ducts, capillary-like structures and arteries that extend throughout the device. Moreover, because the position, size, and shape of each perforation and etching can be varied from layer to layer, the resulting conduits, as well as the outer envelope of the entire device, can be manufactured so as to conform to virtually any desired geometry. Such capability provides for extreme flexibility in terms of accessing one or more heat sources, accessing one or more heat sinks and the routing of a cooling path or paths therebetween. Additionally, the heat pipe device may readily be shaped to precisely conform to the heat source and the heat sink so as to maximize the transfer of heat therebetween. Furthermore, the etchings and perforations are easily configured so as to transport heat in either one, two or three dimensions. Both the liquid as well as the gaseous phases of the coolant contained therein are free to translate throughout the available flow paths and as a result, heat is automatically transferred from wherever a region of high temperature is located to wherever a region of low temperature is located.
In a preferred embodiment, metallic foil is appropriately processed so as to have formed therein a pattern of precisely dimensioned perforations and half-etchings. A plurality of such foil layers, each with a selected pattern of perforations and half-etchings, are subsequently stacked, one on top of another, wherein the various perforations and half-etchings in the layers cooperate to define the various vapor and liquid conduits. The larger conduits facilitate the transport of vapor while extremely small passages or grooves support capillary action for the transport of liquid. More specifically, vapor transport in a single dimension is typically achieved by a plurality of parallel cells wherein such cells may optionally be set into fluid communication with one another via ducts to provide for multi-dimensional vapor transport. Grooves formed on the walls of the cells and extending along their lengths serve for the one dimensional transport of liquid while gaps may be formed between adjoining cells to define arteries that not only provide additional parallel flowpaths but provide for the multi-dimensional transport of liquid. Alternatively, pores formed in the cell walls serve as a wick by forming a capillary interface between the interior of the cell and the adjoining arterial network. Faceplates cap the cells and serve to seal the structure, while grooves formed on the interior surface of the faceplates further set the capillaries and the arterial network into fluid communication with the vapor conduits. The device is positioned such that one faceplate or portion thereof is adjacent the heat source and another faceplate or portion thereof is adjacent a heat sink. In this particular configuration, the sections of cell wall adjacent the faceplates provide extended firm structures to augment face sheet heat transfer areas.
Construction of a heat pipe device of the present invention is generally accomplished as follows. Upon considering the heat transfer requirements and available space in a particular application, the exterior envelope of the device determined. Subsequent thereto, the internal routing of the cells, ducts, capillaries and arterial network is designed so as to optimize the utilization of the available interior space and provide for either a single or multi-dimensional heat transfer configuration. The corresponding pattern of perforations and half etchings are then determined for each individual layer of foil. Such pattern is imparted to the individual foils wherein the precise dimensioning and shaping of the capillaries that is thereby possible allows capillary action performance to be optimized. The flexibility of such system is inherent in the fact that the manufacturing process is substantially unaffected by the complexity of the configurational requirements that may be dictated by a particular application. The effort required to manufacture a particular foil is substantially the same regardless of the number of heat sources, their positions and configurations, the number of heat sinks, their positions and configurations and the paths available therebetween. The individual layers are ultimately stacked and bonded to one another to form a substantially monolithic structure. When integrated within a s
Cuda Rosenbaum I
Fulwider Patton Lee & Utecht LLP
Sadleback Aerospace
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