Lightweight carbon foam structure for phase change material heat sinks
The PCM heat sink design addresses the balance between thermal conductivity and latent heat storage by using a carbon graphite matrix with expanded graphite, enhancing volume and heat capacity while maintaining conductivity.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- HAMILTON SUNDSTRAND CORP
- Filing Date
- 2022-04-28
- Publication Date
- 2026-05-20
AI Technical Summary
Existing phase change material (PCM) heat sinks face challenges in optimizing the balance between thermal conductivity and latent heat storage capacity, as they often compromise one for the other due to the limited volume and conductivity properties of the carbon graphite matrix.
A PCM heat sink design that incorporates a carbon graphite matrix with removal sections replaced by expanded graphite, allowing for increased PCM volume and latent heat storage while maintaining high thermal conductivity by using a combination of carbon graphite and expanded graphite.
The design enhances the available volume for PCM and heat capacity without significantly impairing thermal conductivity, providing improved heat management capabilities.
Smart Images
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Abstract
Description
Technical Field
[0001] The subject matter disclosed herein generally relates to the field of heat sinks, and more particularly, to phase change material heat sinks.
Background Art
[0002] Phase change material (PCM) heat sinks utilize a PCM such as water, wax, or other materials having a desired melting point to store and release thermal energy associated with solid-liquid phase changes. The energy associated with such changes is generally referred to as the latent heat of fusion. One type of PCM heat sink uses a heat transfer fluid to transfer thermal energy into and out of the heat sink. The fluid flows through fluid passage elements that thermally contact the PCM and allow heat transfer to occur while keeping the fluid isolated from the PCM.
Summary of the Invention
Means for Solving the Problems
[0003] According to one embodiment, a phase change material heat sink is provided. The phase change material heat sink includes a carbon graphite matrix having one or more removal portions and expanded graphite located within the one or more removal portions.
[0004] In addition to or as an alternative to the one or more features described above, further embodiments may include a sealed chamber. The carbon graphite matrix is located within the sealed chamber.
[0005] In addition to or as an alternative to the one or more features described above, further embodiments may include a phase change material located within the sealed chamber. The phase change material is embedded within the carbon graphite matrix and the expanded graphite.
[0006] In addition to or as an alternative to the one or more features described above, in further embodiments, the one or more removal portions may include holes.
[0007] In addition to, or alternatively to, one or more of the above features, further embodiments may include one or more removal units being channels.
[0008] In addition to, or as an alternative to, one of the above features, in further embodiments, the expanded graphite may include filling a selected proportion of one or more removal sections.
[0009] In addition to, or alternatively to, one of the above features, further embodiments may include a selection of 10 percent or less.
[0010] In addition to, or alternatively to, one of the above features, further embodiments may include the selected percentage being equal to 10 percent.
[0011] A method for manufacturing a phase-change material heat sink is provided according to another embodiment. This method includes obtaining a carbon-graphite matrix having one or more removal sections, and inserting expanded graphite into one or more removal sections.
[0012] In addition to, or as an alternative to, one or more of the above features, further embodiments may include forming a carbon graphite matrix having one or more removal sections.
[0013] In addition to, or as an alternative to, one or more of the above features, further embodiments may include machining one or more holes in the carbon graphite matrix to form one or more removal sections.
[0014] In addition to, or as an alternative to, one or more of the above features, further embodiments may include machining one or more channels in the carbon graphite matrix to form one or more removal sections.
[0015] In addition to, or as an alternative to, one or more of the above features, further embodiments may include inserting a carbon graphite matrix and expanded graphite into a sealed chamber.
[0016] In addition to, or as an alternative to, one or more of the above features, further embodiments may include inserting the phase-change material into a carbon-graphite matrix and expanded graphite located within a sealed chamber.
[0017] In addition to, or as an alternative to, one of the above features, in further embodiments, the expanded graphite may include filling a selected proportion of one or more removal sections.
[0018] In addition to, or alternatively to, one of the above features, further embodiments may include a selection of 10 percent or less.
[0019] In addition to, or alternatively to, one of the above features, further embodiments may include the selected percentage being equal to 10 percent.
[0020] In addition to, or as an alternative to, one or more of the above features, further embodiments may include inserting a phase-change material into a carbon-graphite matrix simultaneously with the expanded graphite.
[0021] In addition to, or as an alternative to, one of the above features, further embodiments may include using a vacuum to insert the phase-change material into the carbon-graphite matrix simultaneously with the expanded graphite.
[0022] In addition to, or as an alternative to, one or more of the above features, further embodiments may include using a vacuum to insert the phase-change material into the carbon graphite matrix and the expanded graphite.
[0023] The aforementioned features and elements are not mutually exclusive and can be combined in various ways unless otherwise explicitly stated. These features and elements, as well as their operation, will become clearer with consideration of the following description and accompanying drawings. However, please understand that the following description and drawings are intended to be illustrative and explanatory in nature, and are not limiting.
[0024] The following description should not be considered as limiting in any way. In the accompanying drawings, like elements are numbered alike.
Brief Description of the Drawings
[0025] [Figure 1] Shows an exploded view of a PCM heat sink according to an embodiment of the present disclosure. <0OO0086> [Figure 2] Is an isometric view of a carbon graphite matrix according to an embodiment of the present disclosure. [Figure 3] Shows a flowchart of a method for manufacturing a PCM heat sink according to an embodiment of the present disclosure.
Modes for Carrying Out the Invention
[0026] A detailed description of one or more embodiments of the disclosed apparatus and method is presented herein by way of example and not limitation with reference to the figures.
[0027] Referring now to FIG. 1, an exploded view of a PCM heat sink 100 according to an embodiment of the present disclosure is shown. The PCM heat sink 100 shown in FIG. 1 is an exemplary configuration, and it is understood that the embodiments disclosed herein may be applicable to PCM heat sinks having different configurations. In one embodiment, the PCM heat sink may receive thermal energy directly from a heat source (e.g., an electronic device housing, etc.) using conduction. The PCM heat sink 100 includes a sealed chamber 106. This sealed chamber 106 includes a carbon graphite matrix 109 located within the sealed chamber 106 and a PCM 120 such as water or wax sealed within the sealed chamber 106. The sealed chamber 106 includes an upper portion 107 and a bottom portion 108. In FIG. 1, the sealed chamber 106 is shown such that the PCM 120 is visible. However, it should be understood that in reality, the upper portion 107 is formed of a solid material and the PCM 120 may not be visible.
[0028] The PCM heat sink 100 also includes a fluid passage element 101. A heat transfer fluid (e.g., Freon or water) enters the end 103 of the fluid passage element 101 through an inlet passage (e.g., a pipe) 102 and exits the fluid passage element 101 through an outlet passage 114. The fluid generally traverses the fluid passage element 101 in the direction indicated by arrow A. The fluid passage element 101 shown in Figure 1 includes a connector portion 104 positioned between the ends 103, allowing the fluid to pass between the ends 103 while simultaneously traversing the fluid passage element 101 from the inlet passage 102 to the outlet passage 114. The connector portion 104 in particular, and the fluid passage element 101 in general, include a bottom portion 105. When the PCM heat sink 100 is assembled, the upper part 107 of the sealed chamber 106 is in thermal contact with the bottom portion 105 of the fluid passage element 101.
[0029] The PCM heatsink 100 also optionally includes a heat dissipation element 111. As shown in the figure, the heat dissipation element 111 includes a heat diffusion fin 113 and an upper part 112. In some cases, the heat dissipation element 111 can be made to thermally contact the sealed chamber 106 to dissipate the heat stored therein. For example, in a satellite situation, heat can be stored in the sealed chamber 106 until the satellite is no longer in line with the sun. At that point, the bottom 108 of the sealed chamber 106 can come into contact with the upper part 112 of the heat dissipation element 111, and the heat can be released into space via the fin 113.
[0030] The PCM120 is located within a sealed chamber 105 and embedded in a carbon-graphite matrix 109. In some embodiments, the PCM120 may be wax or paraffin wax. The carbon-graphite matrix 109 is configured to stabilize the shape of the PCM120 and to increase its thermal conductivity. The carbon-graphite matrix 109 conducts heat better than the PCM120 and can disperse heat better through the PCM120 than when the PCM120 is used alone without the carbon-graphite matrix 109.
[0031] The carbon-graphite matrix 109 consists of a graphite material that forms a monolithic matrix structure, but there are few options for this material, the best of which has an open porosity of 60%. It is desirable to increase the percentage of open porosity so that more PCM 120 can be loaded into the sealed chamber 106 without impairing the matrix's ability to shape-stabilize the PCM 120 during the phase transition cycle. Embodiments disclosed herein aim to remove a portion of the carbon-graphite matrix 109 and replace a portion of the carbon-graphite matrix 109 with expanded graphite 150 (see Figure 2). Advantageously, by replacing a portion of the carbon-graphite matrix 109 with expanded graphite 150 (see Figure 2), the volume of PCM 120 can be increased within the sealed chamber 106, providing a larger amount of latent heat storage.
[0032] Referring again to Figure 1, and now to Figure 2, the carbon-graphite matrix 109 is shown according to embodiments of the present disclosure. The carbon-graphite matrix 109 may be a monolithic matrix structure made of a single material. The carbon-graphite matrix 109 may have a porosity between 95% and 50%. For example, a porosity of 95% would mean that the carbon-graphite matrix 109 is 5% of its volume and 95% of its volume is open space. The carbon-graphite matrix 109 in Figure 2 includes a removal section 121 from which a portion of the carbon-graphite matrix 109 has been removed. The portion of the carbon-graphite matrix 109 may be removed by drilling, machining, or any other manufacturing process. In one embodiment, the removal section 121 may be a hole 121a. The hole 121a may stretch the carbon-graphite matrix 109 entirely or partially. In another embodiment, the removal section 121 may be a channel 121b. The channel 121b may stretch the carbon-graphite matrix 109 entirely or partially. In one embodiment, there may be any number of removal sections 121. The removal sections 121 may also be located on any side 110 of the carbon graphite matrix 109. The removal sections 121 are then backfilled with expanded graphite 150 to a selected percentage. The selected percentage is the percentage of the removal sections 121 and may be measured between 0% and 100%. At 0%, the removal sections 121 are not filled at all with expanded graphite 150, and at 100%, the entire removal section 121 is completely filled with expanded graphite 150. The PCM 120 is located in a sealed chamber 105 and embedded in the carbon graphite matrix 109 and the expanded graphite 150. The expanded graphite 150 may have a porosity between 2% and 20%. In one embodiment, the expanded graphite has a porosity of 10%.
[0033] The carbon graphite matrix 109 has a higher effective conductivity than the expanded graphite 150. When the carbon graphite matrix 109 is removed and replaced with expanded graphite 150, the effective conductivity of the combination of carbon graphite matrix 109 and expanded graphite 150 decreases, but the addition of expanded graphite increases the available volume in the PCM 120, resulting in a greater heat capacity for the PCM 120. Therefore, using all of the carbon graphite matrix 109 increases the effective conductivity of the PCM 120 but reduces its available volume. Conversely, using all of the expanded graphite 150 results in a lower effective conductivity but increases the available volume of the PCM 120.
[0034] Therefore, the removal section 121 in Figure 2 should remove a portion, though not all, of the carbon graphite matrix 109 and replace it with a selected proportion of expanded graphite 150 to increase the available volume of the PCM 120 while maintaining high effective conductivity. In one embodiment, the selected proportion of expanded graphite 150 may be between approximately 0% and 10% of the removal section 121. In another embodiment, the selected proportion of expanded graphite 150 may be between approximately 5% and 10% of the removal section 121. In one embodiment, the selected proportion of expanded graphite 150 may be about 10% of the removal section 121.
[0035] Continuing with reference to Figures 1 and 2, and now referring to Figure 3, a flowchart of a method 400 for manufacturing a PCM heatsink 100 according to an embodiment of the present disclosure is shown.
[0036] In block 404, a carbon graphite matrix 109 having one or more removal sections 121 is obtained. In block 406, expanded graphite 150 is inserted into one or more removal sections 121. The expanded graphite 150 may fill one or more removal sections 121 in a selected proportion. The selected proportion may be 10 percent or less. The selected proportion may be equal to 10 percent.
[0037] Method 400 may further include forming a carbon graphite matrix 109 having one or more removal portions 121. In another embodiment, the carbon graphite matrix 109 and the one or more removal portions 121 may be formed by machining one or more holes 121a in the carbon graphite matrix 109 to form one or more removal portions 121. In another embodiment, the carbon graphite matrix 109 and the one or more removal portions 121 may be formed by machining one or more channels 121b in the carbon graphite matrix 109 to form one or more removal portions 121.
[0038] Method 400 may also include inserting the carbon graphite matrix 109 and the expanded graphite 150 into a sealed chamber 106. Method 400 may also include inserting the PCM 120 into the carbon graphite matrix 109 and the expanded graphite 150 located inside the sealed chamber 106.
[0039] PCM120 can be inserted into the carbon graphite matrix 109 simultaneously with the expanded graphite 150. For example, PCM120 can be inserted into the carbon graphite matrix 109 simultaneously with the expanded graphite 150 using a vacuum. PCM120 can be mixed into the slurry together with the expanded graphite 150 which is inserted into the carbon graphite matrix 109 at the same time.
[0040] Alternatively, the expanded graphite 150 may be inserted into the carbon graphite matrix 109 before the PCM 120. For example, the expanded graphite 150 may be mixed into the carbon graphite matrix 109, and then the PCM 120 may be inserted into the carbon graphite matrix 109 and the expanded graphite 150 using a vacuum.
[0041] While the above description illustrates the flow step in Figure 3 in a specific order, please understand that the order of the steps may change unless otherwise specifically required in the attached claims, and that the order of the steps may occur simultaneously or nearly simultaneously within layers, etc.
[0042] The technical effects and advantages of the features described herein include removing selected portions of the carbon graphite matrix and replacing the expanded graphite 150 to increase the volume available for PCM and heat capacity without excessively impairing conductivity.
[0043] A detailed description of one or more embodiments of the disclosed apparatus and methods is presented herein as illustrative, not limiting, with reference to the figures.
[0044] The term "approximately" is intended to include the degree of error associated with the measurement of a particular quantity based on the equipment available at the time of filing.
[0045] The technical terms used herein are for the sole purpose of describing specific embodiments and are not intended to limit this disclosure. As used herein, the singular forms “a,” “an,” and “the” are also intended to include the plural forms unless the context otherwise explicitly indicates. Furthermore, it should be understood that the terms “comprises” and / or “comprising,” when used herein, identify the presence of the described feature, integer, step, action, element, and / or component, but do not exclude the presence or addition of one or more other features, integers, steps, actions, elements, components, and / or groups thereof.
[0046] While this disclosure is described with reference to exemplary embodiments or multiple embodiments, it will be understood by those skilled in the art that various modifications can be made without departing from the scope of this disclosure, and that equivalents can be substituted for its elements. Furthermore, many modifications can be made without departing from the essential scope of this disclosure to adapt the teachings of this disclosure to specific circumstances or materials. Thus, this disclosure is not limited to specific embodiments disclosed as the best possible form conceived for carrying out this disclosure, but is intended to include all embodiments within the claims.
Claims
1. A carbon graphite matrix having one or more removal sections, Expanded graphite located within one or more of the removal sections, Includes, The expanded graphite fills the one or more removal sections in a selected proportion. Phase change material heat sink.
2. A phase change material heat sink according to claim 1, further comprising a sealed chamber, wherein the carbon graphite matrix is located within the sealed chamber.
3. The phase change material heat sink according to claim 2, further comprising a phase change material located within the sealed chamber, wherein the phase change material is embedded within the carbon graphite matrix and the expanded graphite.
4. The phase change material heat sink according to claim 1, wherein one or more of the removal portions are holes.
5. The phase change material heat sink according to claim 1, wherein the one or more removal sections are channels.
6. The phase change material heat sink according to claim 1, wherein the selected percentage is 10 percent or less.
7. The phase change material heat sink according to claim 1, wherein the selected proportion is equal to 10 percent.
8. A method for manufacturing a phase change material heat sink, To obtain a carbon graphite matrix having one or more removal areas, Inserting expanded graphite into one or more of the removal sections, Includes, The expanded graphite fills the one or more removal sections in a selected proportion. method.
9. The method according to claim 8, further comprising forming the carbon graphite matrix having one or more removal portions.
10. The method according to claim 8, further comprising machining one or more holes in the carbon graphite matrix to form one or more removal portions.
11. The method according to claim 8, further comprising machining one or more channels in the carbon graphite matrix to form one or more removal portions.
12. The method according to claim 8, further comprising inserting the carbon graphite matrix and the expanded graphite into a sealed chamber.
13. The method according to claim 12, further comprising inserting a phase change material into the carbon graphite matrix and the expanded graphite located within the sealed chamber.
14. The method according to claim 8, wherein the selected percentage is 10 percent or less.
15. The method according to claim 8, wherein the selected percentage is equal to 10 percent.
16. The method according to claim 12, further comprising inserting a phase change material into the carbon graphite matrix at the same time as the expanded graphite.
17. The method according to claim 12, further comprising using a vacuum to insert a phase change material into the carbon graphite matrix simultaneously with the expanded graphite.
18. The method according to claim 12, further comprising using a vacuum to insert a phase change material into the carbon graphite matrix and the expanded graphite.