Layered radiator for efficient heat rejection

Abstract

A radiator which rejects heat to its surrounding environment through radiation, comprising layers of thermally conductive material in a tapered geometry. As well, a radiator which incorporates structural support to maintain rigidity in the out-of-plane directions for its thermally conductive layers. The radiator is used by incorporating a source of heat to the layers, having a lower temperature in the surrounding environment, and structurally attaching to an assigned location.

Claims

1. A radiator comprising: at least two thermally conductive layers arranged in a stack of layers; a heat transfer clamping bracket operably coupled to a first end of the layers of the stack and configured to deliver heat from a heat source to said layers, the heat transfer clamping bracket having a heat source receiving portion configured to thermally couple with a heat source, the heat transfer clamping bracket being configured to clamp said layers together proximal to said heat transfer source; and one or more supporting brackets coupled at a first end thereof to the heat transfer clamping bracket and arranged along a length of the stack of thermally conductive layers, the one or more structurally supporting brackets supporting the stack of thermally conductive layers in a predetermined orientation, wherein the stack of layers has a tapered overall shape in cross section due to sequentially shorter lengths of the thermally conductive layers exposing a second end of each layer to a surrounding environment for heat rejection, a total thickness of the stack diminishing with distance away from said heat transfer clamping bracket.

2. The radiator according to claim 1, further including, on at least a portion of a surface of each thermally conductive layer, a heat-emission layer wherein the heat-emission layer has an exposed surface with an emissivity of at least 0.7.

3. The radiator according to claim 2, further comprising an adhesive layer arranged to bond said each thermally conductive layer to said heat-emission layer.

4. The radiator according to claim 1, further comprising one or more layer-securing units configured to mechanically fix each of the thermally conductive layers in place, said layer-securing units being disposed in or on the stack at one or more distances away from the heat transfer clamping bracket.

5. The radiator according to claim 1, further comprising one or more layer-securing units configured to mechanically fix said thermally conductive layers to each other, said one or more layer-securing units being disposed in or on the stack at one or more distances away from said heat transfer unit, wherein each layer-securing unit attaches to the heat transfer clamping bracket that clamps said thermally conductive layers.

6. The radiator according to claim 1, wherein at least a portion of the heat transfer clamping bracket is composed of aluminum.

7. The radiator according to claim 1, wherein the heat transfer clamping bracket is formed at least in part from a resiliently compliant material and positioned to apply force against the stack of thermally conductive layers, the force corresponding to an amount of compliance of the resiliently compliant material against the stack of conductive layers.

8. The radiator according to claim 1, wherein at least one of said thermally conductive layers includes a pyrolytic graphite sheet.

9. The radiator according to claim 1, wherein the radiator includes at least two instances of the stack of layers, each stack instance being thermally coupled to the heat transfer clamping bracket at the first end of the respective stack.

10. The radiator according to claim 9, wherein the at least two stacks of layers and the heat transfer clamping bracket are arranged substantially in a common plane.

11. The radiator according to claim 1, wherein at least one of said thermally conductive layers is composed of aluminum.

12. The radiator according to claim 1, wherein the thermally conductive layers are disposed having a distance less than 400 ?m between adjacent thermally conductive layers.

13. The radiator according to claim 1, wherein each structurally supporting bracket includes a first half and a second half, the first half of the structurally supporting bracket being disposed on one side of the stack of thermally conductive layers, and the second half being disposed on an opposite side of the stack of thermally conductive layers.

14. The radiator according to claim 1, wherein the stack of layers includes a number of the thermally conductive layers arranged on respective sides of one or more central layers, in a mutually tapered cross section such that a length of the one or more central layers of the thermally conductive layers is longer, from the first end of the one or more central layers to the second end of the one or more central layers, than a length of adjacent layers, of the thermally conductive layers arranged on respective sides of the one or more central layers.

15. The radiator according to claim 14, wherein the thermally conductive layers arranged on respective sides of the central layer include at least one pair of thermally conductive layers arranged symmetrically about the one or more central layers and having a common length with each other.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is an isometric view of a multiple-sided radiator

(2) FIG. 2 is a side view of a multiple-sided radiator

(3) FIG. 2A is a detailed view of the last 4 layers of a single side of the radiator from FIG. 2

(4) FIG. 2B is a detailed view of a clamping bracket attached to the layers of the radiator from FIG. 2 along with a source of heat

(5) FIG. 2C is a detailed view of the radiator's layers' connection to the clamping bracket from FIG. 2B

(6) FIG. 3 is an isometric view of a multiple-sided radiator with structural supports

(7) FIG. 3A is an isometric view of a support structure

(8) FIG. 4 is an isometric view of a multiple-sided radiator with disks compressing the layers together

(9) FIG. 4A is a disk used to compress layers together

(10) FIG. 4B is a front view of a multiple-sided radiator with disks compressing the layers

(11) FIG. 5 is an isometric view of a spacecraft with several connected radiator assemblies along with tubes to transport the heat to those radiators

(12) FIG. 6 is a detailed view of tapered radiator layers with a layer or coating to increase the surface's emissivity.

DETAILED DESCRIPTION

(13) FIG. 1 shows an isometric view of a multiple-sided tapered radiator assembly, referred to as the first embodiment, or just the radiator, 9. This image shows the tapered layered thermally conductive sheets, referred to as the layers, including the last four, 1, 2, 3, and 4 which are labeled. It also includes a clamping bracket that both holds the layers together, and transfers heat to them from the source of heat, 6. It should be noted that this design assumes radiation occurs from both top and bottom layered surfaces, although some applications would only use one side. If this is the case, one could consider using just the top half of the layers, still tapered, just not symmetric. As has been mentioned previously, other linear, or non-linear curves that the taper follows could also work. Here, the device is shown to be around 200 mm wide, however, since this device is here depicted as a constant cross-section, this dimension could be changed to whatever is necessary for the application. The device does not need to be a constant cross-section, however.

(14) FIG. 2 shows a front view of this embodiment. The clamping bracket can be seen in the center section, and the layered sections can be seen on either side. Because the layers of this radiator are very thin and long, a zoomed-in detailed view is required.

(15) FIG. 2A shows how the layers taper, and this view includes break lines in between the lengths of the layers because it would be difficult to show this effect if it were at true scale. I presently contemplate that these layers are 10 ?m thick each, made of pyrolytic graphite with in-plane thermal conductivity of 1950 W/(m*K), with 10 layers per quadrant, however, it can have different sizes, and use different materials. The tapering effect reduces mass towards the sections that are further from the heat source, which is important in optimizing for heat per unit mass of any radiator.

(16) FIG. 2B shows the clamping bracket of part number 5 and shows it in contact with the layers in between it. This contact is important for the function of this device because the heat source, 6, needs to have a pathway to conduct heat through the bracket, and into the layers which spread the heat horizontally. This contact is emphasized in the detailed view, FIG. 2C. This bracket is a dual-purpose device, which supports the layers, but also transfers heat to them as well. I presently contemplate this to be made from aluminum 1050-H14, 22 mm wide, 10 mm tall, in an oval internal cross-section, although other materials, dimensions, and cross-sections could also be used. The source of heat, 6, along with the clamping bracket, 5, together make up the means of delivering heat to the thermally conductive layers.

(17) FIG. 2C shows a detailed view of the clamping bracket, part 5, which transfers heat from the source to the layers through conductive heat transfer. The layers are all clamped together, and the furthest four layers, parts 1, 2, 3, and 4, of the top right quadrant of the radiator can be seen near the center of this detailed view. To reduce thermal resistance (reducing a drop in temperature) heat transfer requires a larger surface area for materials or geometries that are less conductive, such as the aluminum bracket. In addition, the layers have a much lower thermal conductivity in the out-of-plane directions, around 14 W/(m*K). These factors combined are the reason why the area of thermal contact is much larger than the total combined thickness of the layers.

(18) FIG. 3 shows a second embodiment, one which includes a structural supporting bracket to maintain the rigidity of these thin flexible layers. This radiator assembly is the same as assembly, 9, with just the addition of a structural supporting bracket, part 7. This supporting element could be necessary if these layers are not otherwise supported. It is shown here attached to the clamping bracket; however, this does not need to be the case. Other supports from a spacecraft could be attached to the external surface of these radiators and used to position its layers in place and prevent any motion due to forces or accelerations.

(19) FIG. 3A shows an isometric view of just the structural supporting bracket, 7. Here, it is presently contemplated to be attached to clamp, 5, through some means of adhesion, although other fastening methods are acceptable as well. This supporting member is shown with material at the end connecting two halves, although this is not necessary for the function of maintaining structural rigidity in the layers. This structural bracket could also be directly attached to the layers by using fasteners or adhesive. This support could be made solid or include hollow sections. The material which is presently thought to be an optimal configuration is carbon fiber composite, however, other materials, sizes, geometries, and placements for this supporting member could also be considered.

(20) FIG. 4 shows a third embodiment which includes multiple devices, each part 8, that affixes this embodiment's layers together. This layer-to-layer contact could be accomplished either by using adhesive or using compression forces created externally from the layers. The function of this device is to ensure that layers are not spreading apart, and to enable good thermal contact between layers for higher heat transfer.

(21) FIG. 4A shows an isometric view of a part, 8, that holds the layers together. This device is pictured using magnets on multiple sides to create the compression loads, but this is just one means of performing this task. Other means of compressing layers could include grommets, clamps, or other fasteners. Other sizes, materials, placements, or means of connecting layers together could also be used instead of part 8 which is depicted.

(22) FIG. 4B shows a front view of the third embodiment, indicating that the parts that hold the layers together, 8, are on opposite sides.

(23) FIG. 5 shows just one example of how to use the first embodiment, assembly 9, on a spacecraft. The radiator assemblies are connected and placed side by side, here in clusters of four. A source of heat, 6, runs through the clusters and transfers heat to the radiating layers. The example spacecraft, 10, has a cylindrical surface which the radiators attach to, however, they could also be deployed from a mechanism, free-floating, or otherwise attached. The source of heat comes from the spacecraft and is then transferred to the radiators through the source of heat, 6. Here, only the front faces are being used for radiation, as these are the faces exposed to the environment. Other uses can include double-sided radiation.

(24) FIG. 6 shows a front detailed view of just two example layers, 1, and 2, tapered, with a heat-emission layer or coating, 11, on the radiating surfaces. This additional layer is used to increase radiation by having an emissivity larger than the conductive layers themselves. This coating, 11, can be adhesive itself, or include a layer underneath it to connect to the conductive layers below.

REFERENCE NUMERALS

(25) 1 furthest layer 2 second from furthest layer 3 third from furthest layer 4 fourth from furthest layer 5 clamping bracket 6 source of heat 7 structural supporting bracket 8 part to hold layers together 9 radiator assembly 10 spacecraft 11 heat-emission layer or coating with or without adhesive
Operation

(26) In operation, one uses these embodiments by providing a source of heat, also known as a means of delivering heat, which transfers this heat to the radiating layers. This means of delivering heat may be accomplished by using heat pipes, pumped fluid loops, or even through the means of conduction of a solid material. A bracket that clamps the layers together can be used to support layers, but also connect them to this means of delivering heat.

(27) The layers need to face a cooler temperature in the surrounding environment for radiative heat transfer to remove heat from the layers. In the presence of an atmosphere, convection could also play a role in transferring heat along with radiation.

(28) To position these radiators, one could add any means of attachment to an assigned fixed location. The use of supporting brackets, walls, straps, cords, adhesives, fasteners, or even using a pressurized tube that maintains tension could be incorporated to keep a radiator in a specified location.

(29) The structural supports that prevent out-of-plane motion of the layers are used by connecting a member that holds the layers to a separate more rigid member, therefore reducing motion when forces are applied.

CONCLUSION, RAMIFICATIONS, AND SCOPE

(30) Accordingly, the reader will see that the tapered and layered radiator embodiments can be used to reject a large amount of heat for minimal mass. Layered sections are held together by structural supports as well as other mechanisms and can withstand forces that may act to displace the layers. A spacecraft which uses this design could save many kilograms of mass over traditional sandwich panel radiator designs. Furthermore, the radiator shown can be connected with many others to reject more heat than when used individually.

(31) Although the description above contains many specificities, these should not be construed as limiting the scope of the embodiments but as merely providing illustrations of some of several embodiments. For example, the structure supporting the radiator layers can come in many shapes or connect to other structures; the source of heat can come from a wall instead of a tube; the layers can be non-symmetric and different sizes, etc.

(32) Thus, the scope of the embodiments should be determined by the appended claims and their legal equivalents, rather than by the examples given.