Patent Application
20220373267
The subject matter disclosed herein relates generally to the field of heat sinks, and specifically to phase change material heat sinks.
Phase change material (PCM) heat sinks utilize PCMs such as water, wax, or other materials with desirable melting points to store and release heat energy associated with the solid-liquid phase change. The energy associated with such a change is generally referred to as the latent heat of fusion. One type of PCM heat sink uses a heat transport fluid to carry thermal energy into and out of the heat sink. The fluid flows through a fluid passage element that bring the fluid into thermal contact with the PCM to allow heat transfer to occur while keeping the fluid isolated from the PCM.
According to one embodiment, a phase change material heat sink is provided. The phase change material heat sink including: a carbon graphite matrix having one or more removed portions; and an expanded graphite located within the one or more removed portions.
In addition to one or more of the features described above, or as an alternative, further embodiments may include a sealed chamber. The carbon graphite matrix is located within the sealed chamber.
In addition to one or more of the features described above, or as an alternative, further embodiments may include a phase change material located within the sealed chamber. The phase change material embedded within the carbon graphite matrix and the expanded graphite.
In addition to one or more of the features described above, or as an alternative, further embodiments may include that the one or more removed portions are holes.
In addition to one or more of the features described above, or as an alternative, further embodiments may include that the one or more removed portions are channels.
In addition to one or more of the features described above, or as an alternative, further embodiments may include that the expanded graphite fills a selected percentage of the one or more removed portions.
In addition to one or more of the features described above, or as an alternative, further embodiments may include that the selected percentage is less than or equal to 10 percent.
In addition to one or more of the features described above, or as an alternative, further embodiments may include that the selected percentage is equal to 10 percent.
According to another embodiment, a method of manufacturing a phase change material heat sink is provided. The method including: obtaining a carbon graphite matrix having one or more removed portions; and inserting an expanded graphite into the one or more removed portions.
In addition to one or more of the features described above, or as an alternative, further embodiments may include forming the carbon graphite matrix having the one or more removed portions.
In addition to one or more of the features described above, or as an alternative, further embodiments may include machining one or more holes in the carbon graphite matrix to form the one or more removed portions.
In addition to one or more of the features described above, or as an alternative, further embodiments may include machining one or more channels in the carbon graphite matrix to form the one or more removed portions.
In addition to one or more of the features described above, or as an alternative, further embodiments may include inserting the carbon graphite matrix and the expanded graphite into a sealed chamber.
In addition to one or more of the features described above, or as an alternative, further embodiments may include inserting a phase change material into the carbon graphite matrix and the expanded graphite located within the sealed chamber.
In addition to one or more of the features described above, or as an alternative, further embodiments may include that the expanded graphite fills a selected percentage of the one or more removed portions.
In addition to one or more of the features described above, or as an alternative, further embodiments may include that the selected percentage is less than or equal to 10 percent.
In addition to one or more of the features described above, or as an alternative, further embodiments may include that the selected percentage is equal to 10 percent.
In addition to one or more of the features described above, or as an alternative, further embodiments may include inserting a phase change material into the carbon graphite matrix simultaneously with the expanded graphite.
In addition to one or more of the features described above, or as an alternative, further embodiments may include inserting a phase change material into the carbon graphite matrix simultaneously with the expanded graphite via a vacuum.
In addition to one or more of the features described above, or as an alternative, further embodiments may include inserting a phase change material into the carbon graphite matrix and the expanded graphite via a vacuum.
The foregoing features and elements may be combined in various combinations without exclusivity, unless expressly indicated otherwise. These features and elements as well as the operation thereof will become more apparent in light of the following description and the accompanying drawings. It should be understood, however, that the following description and drawings are intended to be illustrative and explanatory in nature and non-limiting.
The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike:
A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figures.
Referring now to
The PCM heat sink 100 also includes a fluid passage element 101. A heat transmission fluid enters (e.g., Freon or water, for example) an end 103 of the fluid passage element 101 via inlet passage (e.g., pipe) 102 and exits it via outlet passage 114. The fluid generally traverses the fluid passage element 101 in the direction shown by arrow A. The fluid passage element 101 illustrated in
The PCM heat sink 100 also optionally include a heat release element 111. As illustrated, the heat release element 111 includes heat diffusion fins 113 and a top 112. In some cases, the heat release element 111 can be brought into thermal contact with the sealed chamber 106 to dissipate heat stored therein. For example, in the context of a satellite, heat may be stored in the sealed chamber 106 until the satellite is not in line-of-sight with the sun. At that time, the bottom 108 of the sealed chamber 106 can be brought into contact with the top 112 of the heat release element 111 and the heat can be released via fins 113 into space.
The PCM 120 is located within the sealed chamber 105 and is embedded within the carbon graphite matrix 109. In an embodiment the PCM 120 may be wax or paraffin wax. The carbon graphite matrix 109 is configured to shape-stabilize the PCM 120 and also increase the thermal conductivity of the PCM 120. The carbon graphite matrix 109 conducts heat better than the PCM 120 and may distribute heat better through the PCM 120 than just using PCM 120 alone without a carbon graphite matrix 109.
The carbon graphite matrix 109 is composed of a graphite material forming a monolithic matrix structure, however few options of this material are available, with one of the best having 60% open porosity. It is desirable to increase the percentage of open porosity, which allows for more PCM 120 to be loaded into sealed chamber 106, without compromising the matrices' ability to shape stabilize the PCM 120 during phase transition cycles. The embodiments disclosed herein seek to remove some of the carbon graphite matrix 109 and replace some of the carbon graphite matrix 109 with an expanded graphite 150 (see
Referring not to
The carbon graphite matrix 109 has an effective conductivity higher than an effective conductivity of the expanded graphite 150. As the carbon graphite matrix 109 is removed and replaced with expanded graphite 150 the effective conductivity of the combination of the carbon graphite matrix 109 and the expanded graphite 150 will decrease but the addition of the expanded graphite will allow the volume available for the PCM 120 to increase, thus giving the PCM 120 more thermal capacity. Thus, using all carbon graphite matrix 109 results in high effective conductivity but low available volume for the PCM 120, whereas using all expanded graphite 150 results in low effective conductivity but more available volume for the PCM 120.
Therefore, the removed portions 121 of
Referring now to
At block 404, a carbon graphite matrix 109 having one or more removed portions 121 is obtained. At block 406, an expanded graphite 150 is inserted into the one or more removed portions 121. The expanded graphite 150 may fill a selected percentage of the one or more removed portions 121. The selected percentage may be less than or equal to 10 percent. The selected percentage may be equal to 10 percent.
The method 400 may further include forming the carbon graphite matrix 109 having one or more removed portions 121 In another embodiment, the carbon graphite matrix 109 and the one or more removed portions 121 may be formed by machining one or more holes 121a in the carbon graphite matrix 109 to form the one or more removed portions 121. In another embodiment, the carbon graphite matrix 109 and the one or more removed portions 121 may be formed by machining one or more channels 121b in the carbon graphite matrix 109 to form the one or more removed portions 121.
The method 400 may also include inserting the carbon graphite matrix 109 and the expanded graphite 150 into a sealed chamber 106. The method 400 may also include inserting a PCM 120 into the carbon graphite matrix 109 and the expanded graphite 150 that are located within the sealed chamber 106.
The PCM 120 may be inserted into the carbon graphite matrix 109 simultaneously with the expanded graphite 150. For example, the PCM 120 may be inserted into the carbon graphite matrix 109 simultaneously with the expanded graphite 150 via a vacuum. The PCM 120 may be mixed into a slurry with the expanded graphite 150 to be inserted into the carbon graphite matrix 109 simultaneously.
Alternatively, the expanded graphite 150 may be inserted into the carbon graphite matrix 109 prior to 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 via a vacuum.
While the above description has described the flow process of
Technical effects and benefits of the features described herein include removing a selected portion of a carbon graphite matrix and replacing with expanded graphite 150 to increase the volume available for PCM and thermal capacity while not compromising too much on conductivity.
A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figures.
The term “about” is intended to include the degree of error associated with measurement of the particular quantity based upon the equipment available at the time of filing the application.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, element components, and/or groups thereof.
While the present disclosure has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the present disclosure. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the present disclosure without departing from the essential scope thereof. Therefore, it is intended that the present disclosure not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this present disclosure, but that the present disclosure will include all embodiments falling within the scope of the claims.
