Oscillating heat pipes with randomly varying channel size

Abstract

Oscillating heat pipes and methods of making the same. The oscillating heat pipes include a condenser region, an evaporator region, and a set of channels arranged between the condenser region and the evaporator region. The set of channels define at least a portion of a fluid circuit for a working fluid. Each channel of the set of channels has a respective channel property value that is a percentage variation from a nominal channel property value and the set of channels defines an aperiodic set of channels with respect to the channel property.

Description

BACKGROUND

[0001] The subject matter disclosed herein generally relates to oscillating heat pipes.

[0002] Oscillating Heat Pipes are typically formed of looping portions or channels and include a condenser region and an evaporator region that are interconnected by an adiabatic region. The looping channels can be filled with a two-phase fluid mixture (i.e., a working fluid), which acts as a heat transfer medium for the system. Instabilities caused by the intermittent evaporation and condensation of the working fluid causes the working fluid to move from the evaporator region to condenser region and to return from the condenser region back to the evaporator region in order to transfer heat between the evaporator and condenser regions.

[0003] In some applications, high gravity loads (i.e., gravitational forces in excess of the normal force of gravity) in high gravity force environments can deteriorate the performance of an oscillating heat pipe by preventing the working fluid from returning to the condenser region from the evaporator region. In an example of airborne vehicles, this can be detrimental to critical equipment that relies on an oscillating heat pipe for cooling. Thus, there is a need for improvements in oscillating heat pipes such that an oscillating heat pipe is less sensitive to high gravity loads and can rapidly resume normal operation once a high gravity load is reduced or removed.SUMMARY

[0004] According to some embodiments, oscillating heat pipes are provided. The oscillating heat pipes include a condenser region, an evaporator region, and a set of channels arranged between the condenser region and the evaporator region. The set of channels defines at least a portion of a fluid circuit for a working fluid. Each channel of the set of channels has a respective channel property value that is a percentage variation from a nominal channel property value and the set of channels defines an aperiodic set of channels with respect to the channel property.

[0005] In addition to one or more of the features described herein, or as an alternative, further embodiments of the oscillating heat pipes may include that each respective channel property value of the individual channels of the set of channels is a random value selected within a predefined range relative to the nominal channel property value.

[0006] In addition to one or more of the features described herein, or as an alternative, further embodiments of the oscillating heat pipes may include that the predefined range is a set of values within 5% of the nominal channel property value.

[0007] In addition to one or more of the features described herein, or as an alternative, further embodiments of the oscillating heat pipes may include that the predefined range is a set of values within a selected percentage range selected between 5%-60% of the nominal channel property value.

[0008] In addition to one or more of the features described herein, or as an alternative, further embodiments of the oscillating heat pipes may include that the set of channels comprises a minimum of three channels.

[0009] In addition to one or more of the features described herein, or as an alternative, further embodiments of the oscillating heat pipes may include that the fluid circuit comprises two or more sets of channels, wherein each set of channels of the two or more sets of channels is identical with respect to the number of channels and the respective channel properties of the channels forming each set of channels, and wherein the sets of channels are fluidly connected together.

[0010] In addition to one or more of the features described herein, or as an alternative, further embodiments of the oscillating heat pipes may include that a first channel of the set of channels has a respective first channel property that is different from a second channel of the set of channels having a respective second channel property.

[0011] In addition to one or more of the features described herein, or as an alternative, further embodiments of the oscillating heat pipes may include that the set of channels comprises at least three channels, wherein each channel of the at least three channels within the set of channels has a different channel property value.

[0012] In addition to one or more of the features described herein, or as an alternative, further embodiments of the oscillating heat pipes may include that the channel property is a channel diameter.

[0013] In addition to one or more of the features described herein, or as an alternative, further embodiments of the oscillating heat pipes may include that the channel property is a channel hydraulic diameter.

[0014] In addition to one or more of the features described herein, or as an alternative, further embodiments of the oscillating heat pipes may include that the channel property is at least one of a channel diameter, a channel width, a channel depth, a channel shape, a channel geometry, a channel cross-sectional area, or a channel hydraulic diameter.

[0015] In addition to one or more of the features described herein, or as an alternative, further embodiments of the oscillating heat pipes may include that each channel is fluidly connected to an adjacent channel by a bend to form the fluid circuit.

[0016] In addition to one or more of the features described herein, or as an alternative, further embodiments of the oscillating heat pipes may include that a first channel of the set of channels is fluidly connected to a second channel by a bend formed in the evaporator region, and the second channel is connected to a third channel by a bend formed in the condenser region.

[0017] In addition to one or more of the features described herein, or as an alternative, further embodiments of the oscillating heat pipes may include an adiabatic region defined between the condenser region and the evaporator region, wherein each channel of the set of channels extends across the adiabatic region between the condenser region and the evaporator region.

[0018] According to some embodiments, methods of manufacturing oscillating heat pipes are provided. The methods include forming a condenser region, forming an evaporator region, and arranging a set of channels to extend between the condenser region and the evaporator region. The set of channels are arranged to define at least a portion of a fluid circuit for a working fluid. Each channel of the set of channels has a respective channel property value that is a percentage variation from a nominal channel property value and the set of channels defines an aperiodic set of channels with respect to the channel property.

[0019] In addition to one or more of the features described herein, or as an alternative, further embodiments of the methods may include that each respective channel property value of the individual channels of the set of channels is a random value selected within a predefined range relative to the nominal channel property value.

[0020] In addition to one or more of the features described herein, or as an alternative, further embodiments of the methods may include that the forming of the condenser region and the evaporator region, and arranging the plurality of channels is performed using additive manufacturing.

[0021] In addition to one or more of the features described herein, or as an alternative, further embodiments of the methods may include that the channel property is at least one of a channel diameter, a channel width, a channel depth, a channel shape, a channel geometry, a channel cross-sectional area, or a channel hydraulic diameter.

[0022] In addition to one or more of the features described herein, or as an alternative, further embodiments of the methods may include that each channel is fluidly connected to an adjacent channel by a bend to form the fluid circuit.

[0023] In addition to one or more of the features described herein, or as an alternative, further embodiments of the methods may include forming an adiabatic region between the condenser region and the evaporator region, wherein each channel of the set of channels extends across the adiabatic region between the condenser region and the evaporator region.

[0024] 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.BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0025] The subject matter is particularly pointed out and distinctly claimed at the conclusion of the specification. The foregoing and other features, and advantages of the present disclosure are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:

[0026] FIG. 1 is a schematic illustration of an oscillating heat pipe that may incorporate embodiments of the present disclosure;

[0027] FIG. 2 is a partial schematic illustration of an oscillating heat pipe in accordance with an example of the present disclosure;

[0028] FIG. 3 is a plot illustrating variations of channel diameter of channels of an oscillating heat pipe in accordance with an embodiment of the present disclosure as compared to a conventional oscillating heat pipe configuration;

[0029] FIG. 4 is a plot illustrating the effective thermal conductivity comparing the operational efficiency of conventional oscillating heat pipes and oscillating heat pipes having variable channel properties in accordance with embodiments of the present disclosure; and

[0030] FIG. 5 is a schematic illustration of another configuration of an oscillating heat pipe in accordance with an embodiment of the present disclosure.DETAILED DESCRIPTION

[0031] As shown and described herein, various features of the disclosure will be presented. Various embodiments may have the same or similar features and thus the same or similar features may be labeled with the same reference numeral, but preceded by a different first number indicating the figure to which the feature is shown. Although similar reference numbers may be used in a generic sense, various embodiments will be described and various features may include changes, alterations, modifications, etc. as will be appreciated by those of skill in the art, whether explicitly described or otherwise would be appreciated by those of skill in the art. A more thorough description will now be provided with reference to the accompanying figures. The details shown in the figures are not necessarily to scale, but are shown to aid in understanding the features of the subject technology.

[0032] FIG. 1 schematically shows an example of an oscillating heat pipe 100 that may incorporate embodiments of the present disclosure. The oscillating heat pipe 100 includes a condenser region 102, an evaporator region 104, and an adiabatic region 106. The oscillating heat pipe 100 includes a fluid circuit 108 that includes a working fluid 110 contained therein. The working fluid 110 may be a two-phase mixture which acts as a heat transfer medium within the oscillating heat pipe 100. The fluid circuit 108 is defined by a set of intermediate channels 112 that extend between bends 114, 116 of the condenser region 102 and the evaporator region 104, respectively. The intermediate channels 112 span or extend across the adiabatic region 106, and thus are defined as channels for fluid and / or thermal exchange between the condenser region 102 and the evaporator region 104. Although illustrated as straight or linear sections, the intermediate channels 112 may be curved, sinuous, or otherwise non-straight, without departing from the scope of the present disclosure.

[0033] The oscillating heat pipe 100 may be configured to be mounted to or otherwise arranged in thermal contact with a heat load or heat source. The evaporator region 104 is arranged in thermal contact with a heat load and the condenser region 102 is arranged to disperse or otherwise remove heat that is transferred from the evaporator region 104, through the adiabatic region 106, and into condenser region 102. Each of the condenser region 102 and the evaporator region 104 include or may be defined by a plate or the like with the respective bends 114, 116 of the fluid circuit 108 of the oscillating heat pipe 100 embedded or otherwise arranged in thermal contact with the plates or region / area of a plate(s).

[0034] As shown in FIG. 1, the condenser region 102 includes the bends 114 of the fluid circuit 108 of the oscillating heat pipe 100 that are operable to transfer heat out of the working fluid 110 within the fluid circuit 108. The condenser region 102 may be thermally coupled to a heat sink that may include any suitable type of structure or device for transferring heat out of the working fluid. For example, the heat sink may include plates, fins, or other types of passive heat dispersion elements, and / or active features, such as a secondary fluid (e.g., air) that may be used to remove heat from the condenser region 102. As the heat is removed from the condenser region 102, the working fluid 110 will cool, and may condense from a gaseous state to a liquid state.

[0035] Similarly, as shown in FIG. 1, the evaporator region 104 includes the bends 116 of the fluid circuit 108 of the oscillating heat pipe 100 that are operable to absorb heat from a heat source (e.g., the plate of the evaporator region 104) into the working fluid 110 contained within the fluid circuit 108. The evaporator region 104 can also include any structure(s) or device(s) that transfers heat from a heat source into the working fluid 110 within the bends 116 of the evaporator region 104. Accordingly, the evaporator region 104 may be thermally coupled to a heat source. The heat source can be an electronic component or other device that generates unwanted heat, such as a battery, processing unit, and / or other components or devices as will be apparent to those skilled in the art. As the heat is absorbed by the working fluid 110 in the evaporator region 104, the working fluid 110 will heat, and may evaporate from a liquid state to a gaseous state.

[0036] As shown in FIG. 1, the oscillating heat pipe 100 is configured in a meandering or serpentine configuration with the bends 114, 116 and a plurality of intermediate channels 112 extending from / between and connecting the bends 114, 116. A number of first bends 114 are located in the condenser region 102 and a number of second bends 116 are located in the evaporator region 104. The example meandering or serpentine configuration shown in FIG. 1 includes the bends 114, 116 that alternate as shown. This alternating configuration is beneficial in that the working fluid 110 within the fluid circuit 108 is alternatively cooled in the condenser region 102 and heated in the evaporator region 104 of the fluid circuit 108. In the example shown in FIG. 1, the oscillating heat pipe 100 is configured as a closed-loop fluid circuit 108. However, in other configurations, a closed-loop arrangement is not required. For example, an oscillating heat pipe having an inlet and an outlet disposed, for example, in the condenser region may be provided. As such, it will be appreciated that open-loop fluid circuits may be employed without departing from the scope of the present disclosure.

[0037] The channels or structure of the fluid circuit 108 can include piping or channels with a diameter that is small enough to enable liquid slugs 118 and vapor plugs 120 to be formed within the working fluid 110. The diameter of the channels of the fluid circuit 108 that enables the formation of liquid slugs 118 and vapor plugs 120 can depend upon the type of working fluid 110 that is used, as well as the makeup and associated properties of the working fluid 110 and the oscillating heat pipe 100 that contribute to things such as surface tension, liquid density, vapor density or any other suitable property.

[0038] In the example shown in FIG. 1, the adiabatic region 106 is provided between the condenser region 102 and the evaporator region 104. The adiabatic region 106 is defined, at least in part, by the intermediate channels 112 of the fluid circuit 108 that extend between the first bends 114 of the condenser region 102 and the second bends 116 of the evaporator region 104. As noted above, although the intermediate channels 112 in the adiabatic region 106 are shown as a plurality of straight portions, such configuration is not intended to be limiting. The intermediate channels in the adiabatic region of an oscillating heat pipe in accordance with an embodiment of the present disclosure need not be straight and can take on any geometry and may conform to an arbitrary surface based on a desired application and implementation. For example, and without limitation, the adiabatic region can be saddle shaped with each of the intermediate channels of the fluid circuit in the adiabatic region conforming to the saddle shape. In operation, the working fluid 110 within the adiabatic region 106 will move such that heat obtained from the evaporator region 104 is moved through the fluid circuit 106 along the intermediate channels 112 until the working fluid 110 reaches the condenser region 102 where the heat can be drawn from the working fluid 110 and transferred out of the oscillating heat pipe 100.

[0039] It is noted that the adiabatic region 108, and the associated intermediate channels 112, can be any size relative to the condenser region 102 and / or the evaporator region 104. For example, the intermediate channels 112 of the adiabatic region 106 can be relatively long compared to the bends 114, 116 of the condenser region 102 and the evaporator region 104. In other embodiments, the adiabatic region 106 can essentially be omitted and the fluid circuit 108 of the oscillating heat pipe 100 can alternately extend directly from the condenser region 102 to the evaporator region 104. In this example, the intermediate channels 110 of the fluid circuit 108 of the oscillating heat pipe 100 that extend between the bends 114, 116 can be a part of the condenser region 102, the evaporator region 104, or both. In some examples, the condenser region 102 and the evaporation region 104 can be adjacent to each other with no gap or spacing, or may even overlap.

[0040] When the oscillating heat pipe 100 is in use, heat can be applied to the working fluid 110 in the bends 116 within the evaporator region 104. This heat can cause at least some of the working fluid 110 to evaporate or otherwise change state. In use, instabilities caused by the intermittent evaporation and condensation of the working fluid 110 transfers the vapor portion of the working fluid 110 (e.g., vapor plugs 120) from the evaporator region 104 to the condenser region 102 and return liquid (e.g., liquid slugs 118) from the condenser region 102 back to the evaporator region 104. The evaporation in the evaporator region 104 results in an increase of vapor pressure inside the fluid circuit 108 of the oscillating heat pipe 100, which causes the generation and growth of bubbles or gaseous pockets / regions within the fluid circuit 108 in the evaporator region 104. The growth of the bubbles and the increase in vapor pressure forces liquid slugs 118 of the working fluid 110 to move toward the condenser region 102. The working fluid 110 that is pushed to the condenser region 102 is then cooled by the heat removal at the bends 114 within the condenser region 102. This cooling reduces the vapor pressure within the working fluid 110 and causes condensation of the gaseous working fluid 110 and provides a restoring force that pushes the working fluid 110 back toward the evaporator region 104. This process of alternate increased vapor pressure leading to bubble generation / growth and subsequent condensation causes oscillation of the working fluid 110 within the fluid circuit 108 of the oscillating heat pipe 100 and allows for the transfer of heat between the evaporator region 104 and the condenser region 102.

[0041] It will be appreciated that the oscillating heat pipe 100 can be configured so that it can function in any orientation. That is, the movement of the working fluid 110 within the fluid circuit 108 of the oscillating heat pipe 100 need not be dependent upon gravity. As such, the oscillating heat pipe 100 may be suitable for use in a variety of applications in which the oscillating heat pipe 100 can be used in different orientations. Further, it will be appreciated that the oscillating heat pipe 100, and the elements thereof, can be formed from a variety of different suitable materials based on the intended application including metals, polymers, or the like, or a combination of these.

[0042] Typically, the condenser region 102 and the evaporator region 104 are interconnected by uniformly sized channels or a repeating pattern of alternating channel sizes (i.e., intermediate channels 112). However, because oscillating heat pipes rely on random instabilities to operate, uniform channel diameters tend to inherently resist these instabilities, which can result in reduced efficiency of the oscillating heat pipes. In view of this and other considerations, rather than employing uniform channel diameters, embodiments of the present disclosure are directed to oscillating heat pipe arrangements that utilize a random pattern of channel diameters. That is, the different sections or portions of the fluid circuits of the oscillating heat pipe may have different diameter channels. For example, and without limitation, the differences in channel diameters may vary by ±20% relative to a nominal diameter. Such a random pattern of channel diameters can facilitate the random behavior that oscillating heat pipes rely upon and thus may improve the performance of oscillating heat pipes as compared to conventional, uniform or patterned diameters.

[0043] Referring now to FIG. 2, a schematic illustration of a portion of an oscillating heat pipe 200 in accordance with an embodiment of the present disclosure is shown. The oscillating heat pipe 200 may be arranged similar to that shown and described with respect to FIG. 1. For example, as shown, the oscillating heat pipe 200 includes a fluid circuit 202 that is defined by channels or piping with a working fluid arranged therein. The working fluid may be a two-phase mixture which acts as a heat transfer medium within the oscillating heat pipe 200. The portion of the oscillating heat pipe 200 illustrated in FIG. 2 includes a heat transfer region 204 and an adiabatic region 206. The heat transfer region 204 may be representative of an evaporator region or a condenser region, as shown and described with respect to FIG. 1. Not shown in FIG. 2 is the other heat transfer region, which would be the other of the evaporator region or the condenser region. In this configuration, it is intended that the fluid circuit 202 of the oscillating heat pipe 200 is a closed-loop circuit, although an open-loop circuit may also have a similar implementation as described herein.

[0044] The fluid circuit 202 includes a plurality of channels 208a-h which include bends in the heat transfer region 204 and are substantially straight channels or pipes along the adiabatic region 206. Each of the channels 208a-h is fluidly coupled to or continuous with an adjacent channel 208a-h to form a closed-loop fluid circuit 202. For example, a working fluid may be configured to evaporate and condense and move through the fluid circuit 202. In one illustrative explanation, working fluid may travel through a first channel 208a, around a first bend 210a in the heat transfer region 204, and into a second channel 208b. The working fluid may then travel along the second channel 208b to a bend in a second heat transfer region (not shown) and flow into a third channel 208c, around a second bend 210b in the heat transfer region 204, and into a fourth channel 208d. The working fluid may continue through the fluid circuit 200 traveling through additional bends (e.g., third bend 210c) and additional channels 208e-f. The working fluid will then flow through a final bend in the non-shown heat transfer region and flow along a seventh channel 208g to a fourth bend 210d in the heat transfer region 204 (e.g., a return bend) and loop back to a final or eighth channel 208h. The working fluid will then travel to the non-shown heat transfer region and re-enter the first channel 208a to complete a closed-loop flow circuit.

[0045] In accordance with embodiments of the present disclosure, characteristics of the channels 208a-h may be varied from one channel to the next. In accordance with embodiments of the present disclosure, the characteristic of the channels that may be varied or variable may include channel diameter, channel width, channel depth, channel shape, channel geometry, channel cross-sectional area, channel hydraulic diameter, or the like. In the example of FIG. 2, the channels 208a-h have differing respective channel diameters 212a-h. As shown, the first channel 208a has a respective first channel diameter 212a, the second channel 208b has a respective second channel diameter 212b, the third channel 208c has a respective third channel diameter 212c, and so on, such that the channel 208n has a respective channel diameter 212n. As noted, the channel diameters 212a-h may be representative of a different property or characteristic, and the present description is not intended to be limited to only variations in channel diameter.

[0046] Each channel 208n may be formed with a randomly selected channel diameter 212n. The randomization may be selected from a predefined range, such as within a range around a nominal diameter. For example, in some embodiments, and without limitation, the channel diameters 212n of the channels 208n may be a value that is +20% relative to a nominal diameter. In a non-limiting example, and with reference to FIG. 2, the first channel 208a may have a first channel diameter 212a that is at a nominal value or first diameter D1. The second channel 208b, in this illustrative embodiment, has a second channel diameter 212b (D2) that is smaller than the first channel diameter 212a (i.e., D2<D1), the third channel 208c has a third channel diameter 212c (D3) that is larger than each of the first diameter (D1) and the second diameter (D2) (i.e., D3>D1>D2). The channel diameters 212d-h may continue in a randomized fashion, all relative to a nominal diameter value, which in this case is described as the first diameter D1. In some configurations, none of the channels may have a diameter equal to the nominal value, but rather each channel may be set with a diameter that is either equal to or within a predetermined range of the nominal value. The set of channel diameters may be an aperiodic, asymmetric, or other non-repeating pattern or non-repeating selection of channel diameter values that are based around a nominal value that is set for the specific configuration of the oscillating heat pipe.

[0047] Referring now to FIG. 3, a plot 300 is shown illustrating a comparison between the diameters of the channels of a conventional oscillating heat pipe and the diameters of the channels of an oscillating heat pipe configured in accordance with an embodiment of the present disclosure. In plot 300 the vertical axis is an arbitrary unit of a channel property (e.g., channel shape, channel size, channel diameter, channel depth, channel width, channel cross-sectional area, channel cross-sectional geometry, channel hydraulic diameter, etc.), and the horizontal axis is representative of a series of number channels arranged in sequence of an oscillating heat pipe fluid circuit.

[0048] As shown, each of the channels of the conventional oscillating heat pipe are uniform and set to a constant or uniform channel property indicated by line 302. In contrast, the channels of the oscillating heat pipe with a varying channel property vary from one channel to the next. For example, in the plot 300, the channels are numbered 1 through 10 and indicating a flow path or circuit, such that a working fluid will travel through the first channel (1) into the second channel (2) and so on up to the tenth channel (10), after which the working fluid will return to the first channel (1). In the illustrative plot 300, the channels of the varying channel property oscillating heat pipe has a loop-to-loop varying configuration, with channels (1), (4), (6) and (8) each being less than the nominal channel property, indicated by line 302. In contrast, channels (2), (3), (5) (7), and (10) each have a channel property that is greater than the nominal channel property, indicated by line 302. Finally, in this illustrative configuration, the ninth channel (9) has a channel property equal to the nominal channel property (line 302).

[0049] In this illustration, the variation of the channel properties of the varying-channel property oscillating heat pipe may be within a 20% variation from the nominal channel property, indicated by line 302. However, it will be appreciated that other ranges of variation may be employed without departing from the scope of the present disclosure. The variation, in accordance with embodiments of the present disclosure, is a variation range that is greater than a manufacturing tolerance, and thus may be greater than 5%, for example. On the outer or larger limit, increasing a channel property too much may result in breakdown of the ability of the oscillating heat pipe to function, and thus an upper limit on variation may exist, depending on the application and configuration of the oscillating heat pipe. For example, and without limitation, an upper boundary of the variation may be 60% of the nominal channel property. Although an upper and lower limit on the variation may exist, the upper and / or lower limits may be imposed on the set of channels, and the individual channels may have a channel property that is equal to or less than the limit, inclusive of a diameter of zero variation (i.e., the channel property is equal to the nominal value or a 0% variation).

[0050] In accordance with some embodiments of the present disclosure, the sets of varying channel property channels may be configured as subsets of a fluid circuit. For example, a fluid circuit of an oscillating heat pipe in accordance with an embodiment of the present disclosure may be arranged with a repeating pattern of sets of randomly sized channels. In one such example, and referring to FIG. 3, a set of ten randomly sized channels may be configured according to plot 300 (varying diameter channels). Within the set of ten channels, the channel property / size is varied by a percentage variation from the nominal value. However, the oscillating heat pipe system may have one hundred or more channels, depending on the size and application thereof. In such an oscillating heat pipe, the channels may be arranged in sets of ten channels, which are randomly assigned channel properties relative to a nominal value, as described above. This set of ten may then be repeated ten times to form an oscillating heat pipe with one hundred channels which are subdivided into repeating sets of ten channels.

[0051] It will be appreciated that oscillating heat pipes with repeating sets of random channel property channels is not limited to ten channels. In accordance with embodiments of the present disclosure, a minimum of three channels, each assigned a random channel property relative to a nominal value, are used to form sets that may then be repeated as sets. As such, each set will have a minimum of three channels, wherein each channel of the set is formed with a random channel property relative to a nominal value. The set may then be repeated any number of times with each set being fluidly coupled together to form a fluid circuit. Stated another way, in accordance with some embodiments, a periodic set of channels with a period greater than three channels is used to form a complete fluid circuit. Although the set repeats, the set is created with at least three channels, with each channel of the set having a channel property that is random or selected within a deviation from a nominal value of the channel property.

[0052] Referring now to FIG. 4, a plot 400 illustrating a comparison between conventional oscillating heat pipes and oscillating heat pipes having varying channel properties, in accordance with embodiments of the present disclosure, is shown. On plot 400, the vertical axis is a representation of relative thermal efficiency. On plot 400, the operational performance of standard oscillating heat pipes are shown and labeled as bars (4-uniform) and (6-uniform), with the number being representative of the number of loops in the oscillating heat pipe. A loop, in this example, includes two channels and a bend. In comparison, the operational performance of varying-channel oscillating heat pipes, in accordance with embodiment of the present disclosure, are shown and labeled as bars (4-random) and (6-random), with the number being representative of the number of channels in the oscillating heat pipe. The variations in channel diameter may be randomized, as described above, with a variation being some percentage of a nominal channel diameter. In plot 400, each loop may be formed of channels having variable channel diameters.

[0053] The measure of operational efficiency is measured as a calculation of the effective thermal conductivity (Keff, effective thermal conductivity, [W / m−K]) askeff=Q⁢LeffA⁢Δ⁢T.As noted, Keff is the effective thermal conductivity (W / m−K), Q is the power transported (W), Leff is the effective length[Levaporator+Lcondenser2+Ladiabatic](m), A is the cross-sectional area (m2), and ΔT is the temperature difference between the evaporator and condenser sections (° C.). As shown in FIG. 4, the efficiency or effective thermal conductivity of the randomized loop configurations is increased as compared to a uniform diameter configuration having the same number of loops. That is, the effective thermal conductivity of the 4-random configuration is greater than the effective thermal conductivity of the 4-uniform configuration. Similarly, the effective thermal conductivity of the 6-random configuration is greater than the effective thermal conductivity of the 6-uniform configuration. Although FIG. 4 is illustrative of four distinct configurations, the plot is provided for illustrative purposes of the improvements achieved through implementation of embodiments of the present disclosure. It will be appreciated that various factors, such as those that are part of the thermal conductivity equation may be different depending on the number of loops, length of the various evaporator, condenser, and adiabatic sections, cross-sectional area of the channels, and the temperature different. Additionally, the number of channels and / or loops is not limited to 4 or 6, but rather any number of channels and / or loops may be implemented without departing from the scope of the present disclosure (see, e.g., FIG. 5).As illustrated in FIG. 4, by implementing channels and / or loops of an oscillating heat pipe with randomized channel diameters, the thermal effectiveness of the oscillating heat pipe may be improved. In the illustrative embodiments shown and described thus far, the implication is that each channel has a uniform diameter / shape / size for the extent between the evaporator region to the condenser region, and that the variation is between the different channels. However, such uniform property within or along a single channel is not intended to be limiting. For example, in some embodiments, the channels may have variable diameters or properties along the length between the evaporator region and the condenser region. Such in-channel variations (e.g., tapering) are shown and described in, commonly owned and having shared inventorship, U.S. patent application Ser. No. 17 / 871,836, published as Application Publication No. 2024 / 0027139, filed Jul. 22, 2022, entitled “Oscillating Heat Pipes Operable within High Gravity Force Equivalent (G-Force) Environments, which is incorporated herein in its entirety. If such features are incorporated into an oscillating heat pipe of the present disclosure, the tapering or variance of one channel to the next may be implemented, but also the channel diameter along the length of an individual channel between the evaporator and condenser regions may also be varied.Referring now to FIG. 5, a schematic view of an oscillating heat pipe 500 in accordance with an embodiment of the present disclosure is shown. The oscillating heat pipe 500 may be similar to the oscillating heat pipes shown and described above, with the difference being that the oscillating heat pipe 500 includes two condenser regions 502a, 502b. As shown, the oscillating heat pipe 500 includes an evaporator region 504 having a plurality of bends 506a, 506b which can absorb heat from a heat source. The oscillating heat pipe 500, in this example, also includes the two condenser regions 502a, 502b each having a plurality of respective bends 508a, 508b which are arranged to transfer heat out of the fluid circuit of the oscillating heat pipe 500 to a heat sink or otherwise disperse or dispose of heat picked up by a working fluid in the evaporator region 504.The oscillating heat pipe 500 defines a first adiabatic region 510a between the evaporator region 504 and the first condenser region 502a and defines a second adiabatic region 510b between the evaporator region 504 and the second condenser region 502b. Each adiabatic region 510a, 510b includes intermediate channels 512a, 512b. In this example, the intermediate channels 512a, 512b in each respective adiabatic region 510a, 510b can be similar to the intermediate channels shown and described above. That is, the intermediate channels 512a, 512b may have randomly selected or different cross-sectional areas / channel diameters, at least relative to each other. For example, two adjacent intermediate channels 512a, 512b, may have cross-sectional areas that are different from each other and may be set relative or randomly selected based on a nominal channel diameter or other nominal channel property or characteristic (e.g., shape, size, diameter, depth, width, cross-sectional area, cross-sectional geometry, hydraulic diameter, etc.).

[0057] As described herein, oscillating heat pipes are provided having variable channel properties, such as shape, size, diameter, depth, width, cross-sectional area, cross-sectional geometry, hydraulic diameter. In accordance with some embodiments of the present disclosure, the variation is provided from one channel to the next such that a sequence of channels (one direction between evaporator and condenser) or loops (two directions, one from evaporator to condenser, a bend, and one from condenser to evaporator) are provided with different channel properties, which are randomly selected or defined relative to a nominal channel property. The variation is a variation that is greater than manufacturing tolerances and is a designed or intended variation in the channel property. The variation of the channels is with respect to a nominal value and not necessarily based on any other individual channels (or loops) of the oscillating heat pipe. As such, in some embodiments, two adjacent channels may have the same channel property. However, overall, the collective set of channels or loops have an aperiodic, asymmetric, or other non-repeating set of channel properties. This variability results in changes in hydraulic properties of the oscillating heat pipe which allows for improved efficiencies. That is, the randomness of the channels allows for increased random instabilities within the oscillating heat pipe, as compared to a system with uniform channel diameters, which tend to inherently resist the instabilities necessary for optimal oscillating heat pipe efficiency.

[0058] In accordance with some embodiments of the present disclosure, methods of manufacturing oscillating heat pipes are provided. The methods may include determining a desired number of channels of an oscillating heat pipe for a particular application. Next, a nominal channel property is determined, which is defined a nominal channel property value. The nominal channel property may be selected based on a variety of factors including, but not limited to, operating temperatures, working fluid properties, required heat removal, length of sections of channels, materials used for the oscillating heat pipe, or the like. With a nominal channel property selection, each channel of the oscillating heat pipe may be assigned a channel property value that is within a predetermined range or variance from the nominal channel property value. That is, each channel may be assigned a random channel property value that is within a preset or predefined range of the nominal channel property value. The range may be, for example, a fixed single value between 5% and 60%. With a nominal channel property value (Vn) and a predefined range (e.g., X % of Vn), the channels of the oscillating heat pipe may be assigned a random channel property value within the predefined range (e.g., between 0% and X % of Vn). The assigned channel property value may be a variation that is greater than or less than the nominal channel property value (Vn) (e.g., ±X % relative to the nominal channel property value (Vn)). In accordance with some embodiments, the oscillating heat pipe may be formed using additive manufacturing methodologies and processes. The end result is an oscillating heat pipe having a variable channel property for a set of channels with an aperiodic, asymmetric, or other non-repeating characteristic. In accordance with some embodiments of the present disclosure, the set of channels may be aperiodic with respect to channel properties such that two adjacent channels have different channel properties.

[0059] Advantageously, embodiments of the present disclosure provide for improved oscillating heat pipes. In accordance with embodiments of the present disclosure, oscillating heat pipes are formed having variable or aperiodic channel properties, which results in structurally imposed variation and hydraulic instabilities to thereby improve the instabilities within a working fluid of the oscillating heat pipe and improve thermal efficiencies thereof. The variations in the channel properties may be related to channel diameter, channel width, channel depth, channel shape, channel geometry, channel cross-sectional area, channel hydraulic diameter, or the like.

[0060] The use of the terms “a”, “an”, “the”, and similar references in the context of description (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or specifically contradicted by context. The modifier “about” used in connection with a quantity is inclusive of the stated value and has the meaning dictated by the context (e.g., it includes the degree of error associated with measurement of the particular quantity). All ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other. It should be appreciated that relative positional terms such as “forward,”“aft,”“upper,”“lower,”“above,”“below,” and the like are with reference to normal operational attitude and should not be considered otherwise limiting.

[0061] While the present disclosure has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the present disclosure is not limited to such disclosed embodiments. Rather, the present disclosure can be modified to incorporate any number of variations, alterations, substitutions, combinations, sub-combinations, or equivalent arrangements not heretofore described, but which are commensurate with the scope of the present disclosure. Additionally, while various embodiments of the present disclosure have been described, it is to be understood that aspects of the present disclosure may include only some of the described embodiments.

[0062] Accordingly, the present disclosure is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.

Examples

Embodiment Construction

[0031]As shown and described herein, various features of the disclosure will be presented. Various embodiments may have the same or similar features and thus the same or similar features may be labeled with the same reference numeral, but preceded by a different first number indicating the figure to which the feature is shown. Although similar reference numbers may be used in a generic sense, various embodiments will be described and various features may include changes, alterations, modifications, etc. as will be appreciated by those of skill in the art, whether explicitly described or otherwise would be appreciated by those of skill in the art. A more thorough description will now be provided with reference to the accompanying figures. The details shown in the figures are not necessarily to scale, but are shown to aid in understanding the features of the subject technology.

[0032]FIG. 1 schematically shows an example of an oscillating heat pipe 100 that may incorporate embodiments ...

BACKGROUND

[0001] The subject matter disclosed herein generally relates to oscillating heat pipes.

[0002] Oscillating Heat Pipes are typically formed of looping portions or channels and include a condenser region and an evaporator region that are interconnected by an adiabatic region. The looping channels can be filled with a two-phase fluid mixture (i.e., a working fluid), which acts as a heat transfer medium for the system. Instabilities caused by the intermittent evaporation and condensation of the working fluid causes the working fluid to move from the evaporator region to condenser region and to return from the condenser region back to the evaporator region in order to transfer heat between the evaporator and condenser regions.

[0003] In some applications, high gravity loads (i.e., gravitational forces in excess of the normal force of gravity) in high gravity force environments can deteriorate the performance of an oscillating heat pipe by preventing the working fluid from returning to the condenser region from the evaporator region. In an example of airborne vehicles, this can be detrimental to critical equipment that relies on an oscillating heat pipe for cooling. Thus, there is a need for improvements in oscillating heat pipes such that an oscillating heat pipe is less sensitive to high gravity loads and can rapidly resume normal operation once a high gravity load is reduced or removed.SUMMARY

[0004] According to some embodiments, oscillating heat pipes are provided. The oscillating heat pipes include a condenser region, an evaporator region, and a set of channels arranged between the condenser region and the evaporator region. The set of channels defines at least a portion of a fluid circuit for a working fluid. Each channel of the set of channels has a respective channel property value that is a percentage variation from a nominal channel property value and the set of channels defines an aperiodic set of channels with respect to the channel property.

[0005] In addition to one or more of the features described herein, or as an alternative, further embodiments of the oscillating heat pipes may include that each respective channel property value of the individual channels of the set of channels is a random value selected within a predefined range relative to the nominal channel property value.

[0006] In addition to one or more of the features described herein, or as an alternative, further embodiments of the oscillating heat pipes may include that the predefined range is a set of values within 5% of the nominal channel property value.

[0007] In addition to one or more of the features described herein, or as an alternative, further embodiments of the oscillating heat pipes may include that the predefined range is a set of values within a selected percentage range selected between 5%-60% of the nominal channel property value.

[0008] In addition to one or more of the features described herein, or as an alternative, further embodiments of the oscillating heat pipes may include that the set of channels comprises a minimum of three channels.

[0009] In addition to one or more of the features described herein, or as an alternative, further embodiments of the oscillating heat pipes may include that the fluid circuit comprises two or more sets of channels, wherein each set of channels of the two or more sets of channels is identical with respect to the number of channels and the respective channel properties of the channels forming each set of channels, and wherein the sets of channels are fluidly connected together.

[0010] In addition to one or more of the features described herein, or as an alternative, further embodiments of the oscillating heat pipes may include that a first channel of the set of channels has a respective first channel property that is different from a second channel of the set of channels having a respective second channel property.

[0011] In addition to one or more of the features described herein, or as an alternative, further embodiments of the oscillating heat pipes may include that the set of channels comprises at least three channels, wherein each channel of the at least three channels within the set of channels has a different channel property value.

[0012] In addition to one or more of the features described herein, or as an alternative, further embodiments of the oscillating heat pipes may include that the channel property is a channel diameter.

[0013] In addition to one or more of the features described herein, or as an alternative, further embodiments of the oscillating heat pipes may include that the channel property is a channel hydraulic diameter.

[0014] In addition to one or more of the features described herein, or as an alternative, further embodiments of the oscillating heat pipes may include that the channel property is at least one of a channel diameter, a channel width, a channel depth, a channel shape, a channel geometry, a channel cross-sectional area, or a channel hydraulic diameter.

[0015] In addition to one or more of the features described herein, or as an alternative, further embodiments of the oscillating heat pipes may include that each channel is fluidly connected to an adjacent channel by a bend to form the fluid circuit.

[0016] In addition to one or more of the features described herein, or as an alternative, further embodiments of the oscillating heat pipes may include that a first channel of the set of channels is fluidly connected to a second channel by a bend formed in the evaporator region, and the second channel is connected to a third channel by a bend formed in the condenser region.

[0017] In addition to one or more of the features described herein, or as an alternative, further embodiments of the oscillating heat pipes may include an adiabatic region defined between the condenser region and the evaporator region, wherein each channel of the set of channels extends across the adiabatic region between the condenser region and the evaporator region.

[0018] According to some embodiments, methods of manufacturing oscillating heat pipes are provided. The methods include forming a condenser region, forming an evaporator region, and arranging a set of channels to extend between the condenser region and the evaporator region. The set of channels are arranged to define at least a portion of a fluid circuit for a working fluid. Each channel of the set of channels has a respective channel property value that is a percentage variation from a nominal channel property value and the set of channels defines an aperiodic set of channels with respect to the channel property.

[0019] In addition to one or more of the features described herein, or as an alternative, further embodiments of the methods may include that each respective channel property value of the individual channels of the set of channels is a random value selected within a predefined range relative to the nominal channel property value.

[0020] In addition to one or more of the features described herein, or as an alternative, further embodiments of the methods may include that the forming of the condenser region and the evaporator region, and arranging the plurality of channels is performed using additive manufacturing.

[0021] In addition to one or more of the features described herein, or as an alternative, further embodiments of the methods may include that the channel property is at least one of a channel diameter, a channel width, a channel depth, a channel shape, a channel geometry, a channel cross-sectional area, or a channel hydraulic diameter.

[0022] In addition to one or more of the features described herein, or as an alternative, further embodiments of the methods may include that each channel is fluidly connected to an adjacent channel by a bend to form the fluid circuit.

[0023] In addition to one or more of the features described herein, or as an alternative, further embodiments of the methods may include forming an adiabatic region between the condenser region and the evaporator region, wherein each channel of the set of channels extends across the adiabatic region between the condenser region and the evaporator region.

[0024] 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.BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0025] The subject matter is particularly pointed out and distinctly claimed at the conclusion of the specification. The foregoing and other features, and advantages of the present disclosure are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:

[0026] FIG. 1 is a schematic illustration of an oscillating heat pipe that may incorporate embodiments of the present disclosure;

[0027] FIG. 2 is a partial schematic illustration of an oscillating heat pipe in accordance with an example of the present disclosure;

[0028] FIG. 3 is a plot illustrating variations of channel diameter of channels of an oscillating heat pipe in accordance with an embodiment of the present disclosure as compared to a conventional oscillating heat pipe configuration;

[0029] FIG. 4 is a plot illustrating the effective thermal conductivity comparing the operational efficiency of conventional oscillating heat pipes and oscillating heat pipes having variable channel properties in accordance with embodiments of the present disclosure; and

[0030] FIG. 5 is a schematic illustration of another configuration of an oscillating heat pipe in accordance with an embodiment of the present disclosure.DETAILED DESCRIPTION

[0031] As shown and described herein, various features of the disclosure will be presented. Various embodiments may have the same or similar features and thus the same or similar features may be labeled with the same reference numeral, but preceded by a different first number indicating the figure to which the feature is shown. Although similar reference numbers may be used in a generic sense, various embodiments will be described and various features may include changes, alterations, modifications, etc. as will be appreciated by those of skill in the art, whether explicitly described or otherwise would be appreciated by those of skill in the art. A more thorough description will now be provided with reference to the accompanying figures. The details shown in the figures are not necessarily to scale, but are shown to aid in understanding the features of the subject technology.

[0032] FIG. 1 schematically shows an example of an oscillating heat pipe 100 that may incorporate embodiments of the present disclosure. The oscillating heat pipe 100 includes a condenser region 102, an evaporator region 104, and an adiabatic region 106. The oscillating heat pipe 100 includes a fluid circuit 108 that includes a working fluid 110 contained therein. The working fluid 110 may be a two-phase mixture which acts as a heat transfer medium within the oscillating heat pipe 100. The fluid circuit 108 is defined by a set of intermediate channels 112 that extend between bends 114, 116 of the condenser region 102 and the evaporator region 104, respectively. The intermediate channels 112 span or extend across the adiabatic region 106, and thus are defined as channels for fluid and / or thermal exchange between the condenser region 102 and the evaporator region 104. Although illustrated as straight or linear sections, the intermediate channels 112 may be curved, sinuous, or otherwise non-straight, without departing from the scope of the present disclosure.

[0033] The oscillating heat pipe 100 may be configured to be mounted to or otherwise arranged in thermal contact with a heat load or heat source. The evaporator region 104 is arranged in thermal contact with a heat load and the condenser region 102 is arranged to disperse or otherwise remove heat that is transferred from the evaporator region 104, through the adiabatic region 106, and into condenser region 102. Each of the condenser region 102 and the evaporator region 104 include or may be defined by a plate or the like with the respective bends 114, 116 of the fluid circuit 108 of the oscillating heat pipe 100 embedded or otherwise arranged in thermal contact with the plates or region / area of a plate(s).

[0034] As shown in FIG. 1, the condenser region 102 includes the bends 114 of the fluid circuit 108 of the oscillating heat pipe 100 that are operable to transfer heat out of the working fluid 110 within the fluid circuit 108. The condenser region 102 may be thermally coupled to a heat sink that may include any suitable type of structure or device for transferring heat out of the working fluid. For example, the heat sink may include plates, fins, or other types of passive heat dispersion elements, and / or active features, such as a secondary fluid (e.g., air) that may be used to remove heat from the condenser region 102. As the heat is removed from the condenser region 102, the working fluid 110 will cool, and may condense from a gaseous state to a liquid state.

[0035] Similarly, as shown in FIG. 1, the evaporator region 104 includes the bends 116 of the fluid circuit 108 of the oscillating heat pipe 100 that are operable to absorb heat from a heat source (e.g., the plate of the evaporator region 104) into the working fluid 110 contained within the fluid circuit 108. The evaporator region 104 can also include any structure(s) or device(s) that transfers heat from a heat source into the working fluid 110 within the bends 116 of the evaporator region 104. Accordingly, the evaporator region 104 may be thermally coupled to a heat source. The heat source can be an electronic component or other device that generates unwanted heat, such as a battery, processing unit, and / or other components or devices as will be apparent to those skilled in the art. As the heat is absorbed by the working fluid 110 in the evaporator region 104, the working fluid 110 will heat, and may evaporate from a liquid state to a gaseous state.

[0036] As shown in FIG. 1, the oscillating heat pipe 100 is configured in a meandering or serpentine configuration with the bends 114, 116 and a plurality of intermediate channels 112 extending from / between and connecting the bends 114, 116. A number of first bends 114 are located in the condenser region 102 and a number of second bends 116 are located in the evaporator region 104. The example meandering or serpentine configuration shown in FIG. 1 includes the bends 114, 116 that alternate as shown. This alternating configuration is beneficial in that the working fluid 110 within the fluid circuit 108 is alternatively cooled in the condenser region 102 and heated in the evaporator region 104 of the fluid circuit 108. In the example shown in FIG. 1, the oscillating heat pipe 100 is configured as a closed-loop fluid circuit 108. However, in other configurations, a closed-loop arrangement is not required. For example, an oscillating heat pipe having an inlet and an outlet disposed, for example, in the condenser region may be provided. As such, it will be appreciated that open-loop fluid circuits may be employed without departing from the scope of the present disclosure.

[0037] The channels or structure of the fluid circuit 108 can include piping or channels with a diameter that is small enough to enable liquid slugs 118 and vapor plugs 120 to be formed within the working fluid 110. The diameter of the channels of the fluid circuit 108 that enables the formation of liquid slugs 118 and vapor plugs 120 can depend upon the type of working fluid 110 that is used, as well as the makeup and associated properties of the working fluid 110 and the oscillating heat pipe 100 that contribute to things such as surface tension, liquid density, vapor density or any other suitable property.

[0038] In the example shown in FIG. 1, the adiabatic region 106 is provided between the condenser region 102 and the evaporator region 104. The adiabatic region 106 is defined, at least in part, by the intermediate channels 112 of the fluid circuit 108 that extend between the first bends 114 of the condenser region 102 and the second bends 116 of the evaporator region 104. As noted above, although the intermediate channels 112 in the adiabatic region 106 are shown as a plurality of straight portions, such configuration is not intended to be limiting. The intermediate channels in the adiabatic region of an oscillating heat pipe in accordance with an embodiment of the present disclosure need not be straight and can take on any geometry and may conform to an arbitrary surface based on a desired application and implementation. For example, and without limitation, the adiabatic region can be saddle shaped with each of the intermediate channels of the fluid circuit in the adiabatic region conforming to the saddle shape. In operation, the working fluid 110 within the adiabatic region 106 will move such that heat obtained from the evaporator region 104 is moved through the fluid circuit 106 along the intermediate channels 112 until the working fluid 110 reaches the condenser region 102 where the heat can be drawn from the working fluid 110 and transferred out of the oscillating heat pipe 100.

[0039] It is noted that the adiabatic region 108, and the associated intermediate channels 112, can be any size relative to the condenser region 102 and / or the evaporator region 104. For example, the intermediate channels 112 of the adiabatic region 106 can be relatively long compared to the bends 114, 116 of the condenser region 102 and the evaporator region 104. In other embodiments, the adiabatic region 106 can essentially be omitted and the fluid circuit 108 of the oscillating heat pipe 100 can alternately extend directly from the condenser region 102 to the evaporator region 104. In this example, the intermediate channels 110 of the fluid circuit 108 of the oscillating heat pipe 100 that extend between the bends 114, 116 can be a part of the condenser region 102, the evaporator region 104, or both. In some examples, the condenser region 102 and the evaporation region 104 can be adjacent to each other with no gap or spacing, or may even overlap.

[0040] When the oscillating heat pipe 100 is in use, heat can be applied to the working fluid 110 in the bends 116 within the evaporator region 104. This heat can cause at least some of the working fluid 110 to evaporate or otherwise change state. In use, instabilities caused by the intermittent evaporation and condensation of the working fluid 110 transfers the vapor portion of the working fluid 110 (e.g., vapor plugs 120) from the evaporator region 104 to the condenser region 102 and return liquid (e.g., liquid slugs 118) from the condenser region 102 back to the evaporator region 104. The evaporation in the evaporator region 104 results in an increase of vapor pressure inside the fluid circuit 108 of the oscillating heat pipe 100, which causes the generation and growth of bubbles or gaseous pockets / regions within the fluid circuit 108 in the evaporator region 104. The growth of the bubbles and the increase in vapor pressure forces liquid slugs 118 of the working fluid 110 to move toward the condenser region 102. The working fluid 110 that is pushed to the condenser region 102 is then cooled by the heat removal at the bends 114 within the condenser region 102. This cooling reduces the vapor pressure within the working fluid 110 and causes condensation of the gaseous working fluid 110 and provides a restoring force that pushes the working fluid 110 back toward the evaporator region 104. This process of alternate increased vapor pressure leading to bubble generation / growth and subsequent condensation causes oscillation of the working fluid 110 within the fluid circuit 108 of the oscillating heat pipe 100 and allows for the transfer of heat between the evaporator region 104 and the condenser region 102.

[0041] It will be appreciated that the oscillating heat pipe 100 can be configured so that it can function in any orientation. That is, the movement of the working fluid 110 within the fluid circuit 108 of the oscillating heat pipe 100 need not be dependent upon gravity. As such, the oscillating heat pipe 100 may be suitable for use in a variety of applications in which the oscillating heat pipe 100 can be used in different orientations. Further, it will be appreciated that the oscillating heat pipe 100, and the elements thereof, can be formed from a variety of different suitable materials based on the intended application including metals, polymers, or the like, or a combination of these.

[0042] Typically, the condenser region 102 and the evaporator region 104 are interconnected by uniformly sized channels or a repeating pattern of alternating channel sizes (i.e., intermediate channels 112). However, because oscillating heat pipes rely on random instabilities to operate, uniform channel diameters tend to inherently resist these instabilities, which can result in reduced efficiency of the oscillating heat pipes. In view of this and other considerations, rather than employing uniform channel diameters, embodiments of the present disclosure are directed to oscillating heat pipe arrangements that utilize a random pattern of channel diameters. That is, the different sections or portions of the fluid circuits of the oscillating heat pipe may have different diameter channels. For example, and without limitation, the differences in channel diameters may vary by ±20% relative to a nominal diameter. Such a random pattern of channel diameters can facilitate the random behavior that oscillating heat pipes rely upon and thus may improve the performance of oscillating heat pipes as compared to conventional, uniform or patterned diameters.

[0043] Referring now to FIG. 2, a schematic illustration of a portion of an oscillating heat pipe 200 in accordance with an embodiment of the present disclosure is shown. The oscillating heat pipe 200 may be arranged similar to that shown and described with respect to FIG. 1. For example, as shown, the oscillating heat pipe 200 includes a fluid circuit 202 that is defined by channels or piping with a working fluid arranged therein. The working fluid may be a two-phase mixture which acts as a heat transfer medium within the oscillating heat pipe 200. The portion of the oscillating heat pipe 200 illustrated in FIG. 2 includes a heat transfer region 204 and an adiabatic region 206. The heat transfer region 204 may be representative of an evaporator region or a condenser region, as shown and described with respect to FIG. 1. Not shown in FIG. 2 is the other heat transfer region, which would be the other of the evaporator region or the condenser region. In this configuration, it is intended that the fluid circuit 202 of the oscillating heat pipe 200 is a closed-loop circuit, although an open-loop circuit may also have a similar implementation as described herein.

[0044] The fluid circuit 202 includes a plurality of channels 208a-h which include bends in the heat transfer region 204 and are substantially straight channels or pipes along the adiabatic region 206. Each of the channels 208a-h is fluidly coupled to or continuous with an adjacent channel 208a-h to form a closed-loop fluid circuit 202. For example, a working fluid may be configured to evaporate and condense and move through the fluid circuit 202. In one illustrative explanation, working fluid may travel through a first channel 208a, around a first bend 210a in the heat transfer region 204, and into a second channel 208b. The working fluid may then travel along the second channel 208b to a bend in a second heat transfer region (not shown) and flow into a third channel 208c, around a second bend 210b in the heat transfer region 204, and into a fourth channel 208d. The working fluid may continue through the fluid circuit 200 traveling through additional bends (e.g., third bend 210c) and additional channels 208e-f. The working fluid will then flow through a final bend in the non-shown heat transfer region and flow along a seventh channel 208g to a fourth bend 210d in the heat transfer region 204 (e.g., a return bend) and loop back to a final or eighth channel 208h. The working fluid will then travel to the non-shown heat transfer region and re-enter the first channel 208a to complete a closed-loop flow circuit.

[0045] In accordance with embodiments of the present disclosure, characteristics of the channels 208a-h may be varied from one channel to the next. In accordance with embodiments of the present disclosure, the characteristic of the channels that may be varied or variable may include channel diameter, channel width, channel depth, channel shape, channel geometry, channel cross-sectional area, channel hydraulic diameter, or the like. In the example of FIG. 2, the channels 208a-h have differing respective channel diameters 212a-h. As shown, the first channel 208a has a respective first channel diameter 212a, the second channel 208b has a respective second channel diameter 212b, the third channel 208c has a respective third channel diameter 212c, and so on, such that the channel 208n has a respective channel diameter 212n. As noted, the channel diameters 212a-h may be representative of a different property or characteristic, and the present description is not intended to be limited to only variations in channel diameter.

[0046] Each channel 208n may be formed with a randomly selected channel diameter 212n. The randomization may be selected from a predefined range, such as within a range around a nominal diameter. For example, in some embodiments, and without limitation, the channel diameters 212n of the channels 208n may be a value that is +20% relative to a nominal diameter. In a non-limiting example, and with reference to FIG. 2, the first channel 208a may have a first channel diameter 212a that is at a nominal value or first diameter D1. The second channel 208b, in this illustrative embodiment, has a second channel diameter 212b (D2) that is smaller than the first channel diameter 212a (i.e., D2<D1), the third channel 208c has a third channel diameter 212c (D3) that is larger than each of the first diameter (D1) and the second diameter (D2) (i.e., D3>D1>D2). The channel diameters 212d-h may continue in a randomized fashion, all relative to a nominal diameter value, which in this case is described as the first diameter D1. In some configurations, none of the channels may have a diameter equal to the nominal value, but rather each channel may be set with a diameter that is either equal to or within a predetermined range of the nominal value. The set of channel diameters may be an aperiodic, asymmetric, or other non-repeating pattern or non-repeating selection of channel diameter values that are based around a nominal value that is set for the specific configuration of the oscillating heat pipe.

[0047] Referring now to FIG. 3, a plot 300 is shown illustrating a comparison between the diameters of the channels of a conventional oscillating heat pipe and the diameters of the channels of an oscillating heat pipe configured in accordance with an embodiment of the present disclosure. In plot 300 the vertical axis is an arbitrary unit of a channel property (e.g., channel shape, channel size, channel diameter, channel depth, channel width, channel cross-sectional area, channel cross-sectional geometry, channel hydraulic diameter, etc.), and the horizontal axis is representative of a series of number channels arranged in sequence of an oscillating heat pipe fluid circuit.

[0048] As shown, each of the channels of the conventional oscillating heat pipe are uniform and set to a constant or uniform channel property indicated by line 302. In contrast, the channels of the oscillating heat pipe with a varying channel property vary from one channel to the next. For example, in the plot 300, the channels are numbered 1 through 10 and indicating a flow path or circuit, such that a working fluid will travel through the first channel (1) into the second channel (2) and so on up to the tenth channel (10), after which the working fluid will return to the first channel (1). In the illustrative plot 300, the channels of the varying channel property oscillating heat pipe has a loop-to-loop varying configuration, with channels (1), (4), (6) and (8) each being less than the nominal channel property, indicated by line 302. In contrast, channels (2), (3), (5) (7), and (10) each have a channel property that is greater than the nominal channel property, indicated by line 302. Finally, in this illustrative configuration, the ninth channel (9) has a channel property equal to the nominal channel property (line 302).

[0049] In this illustration, the variation of the channel properties of the varying-channel property oscillating heat pipe may be within a 20% variation from the nominal channel property, indicated by line 302. However, it will be appreciated that other ranges of variation may be employed without departing from the scope of the present disclosure. The variation, in accordance with embodiments of the present disclosure, is a variation range that is greater than a manufacturing tolerance, and thus may be greater than 5%, for example. On the outer or larger limit, increasing a channel property too much may result in breakdown of the ability of the oscillating heat pipe to function, and thus an upper limit on variation may exist, depending on the application and configuration of the oscillating heat pipe. For example, and without limitation, an upper boundary of the variation may be 60% of the nominal channel property. Although an upper and lower limit on the variation may exist, the upper and / or lower limits may be imposed on the set of channels, and the individual channels may have a channel property that is equal to or less than the limit, inclusive of a diameter of zero variation (i.e., the channel property is equal to the nominal value or a 0% variation).

[0050] In accordance with some embodiments of the present disclosure, the sets of varying channel property channels may be configured as subsets of a fluid circuit. For example, a fluid circuit of an oscillating heat pipe in accordance with an embodiment of the present disclosure may be arranged with a repeating pattern of sets of randomly sized channels. In one such example, and referring to FIG. 3, a set of ten randomly sized channels may be configured according to plot 300 (varying diameter channels). Within the set of ten channels, the channel property / size is varied by a percentage variation from the nominal value. However, the oscillating heat pipe system may have one hundred or more channels, depending on the size and application thereof. In such an oscillating heat pipe, the channels may be arranged in sets of ten channels, which are randomly assigned channel properties relative to a nominal value, as described above. This set of ten may then be repeated ten times to form an oscillating heat pipe with one hundred channels which are subdivided into repeating sets of ten channels.

[0051] It will be appreciated that oscillating heat pipes with repeating sets of random channel property channels is not limited to ten channels. In accordance with embodiments of the present disclosure, a minimum of three channels, each assigned a random channel property relative to a nominal value, are used to form sets that may then be repeated as sets. As such, each set will have a minimum of three channels, wherein each channel of the set is formed with a random channel property relative to a nominal value. The set may then be repeated any number of times with each set being fluidly coupled together to form a fluid circuit. Stated another way, in accordance with some embodiments, a periodic set of channels with a period greater than three channels is used to form a complete fluid circuit. Although the set repeats, the set is created with at least three channels, with each channel of the set having a channel property that is random or selected within a deviation from a nominal value of the channel property.

[0052] Referring now to FIG. 4, a plot 400 illustrating a comparison between conventional oscillating heat pipes and oscillating heat pipes having varying channel properties, in accordance with embodiments of the present disclosure, is shown. On plot 400, the vertical axis is a representation of relative thermal efficiency. On plot 400, the operational performance of standard oscillating heat pipes are shown and labeled as bars (4-uniform) and (6-uniform), with the number being representative of the number of loops in the oscillating heat pipe. A loop, in this example, includes two channels and a bend. In comparison, the operational performance of varying-channel oscillating heat pipes, in accordance with embodiment of the present disclosure, are shown and labeled as bars (4-random) and (6-random), with the number being representative of the number of channels in the oscillating heat pipe. The variations in channel diameter may be randomized, as described above, with a variation being some percentage of a nominal channel diameter. In plot 400, each loop may be formed of channels having variable channel diameters.

[0053] The measure of operational efficiency is measured as a calculation of the effective thermal conductivity (Keff, effective thermal conductivity, [W / m−K]) askeff=Q⁢LeffA⁢Δ⁢T.As noted, Keff is the effective thermal conductivity (W / m−K), Q is the power transported (W), Leff is the effective length[Levaporator+Lcondenser2+Ladiabatic](m), A is the cross-sectional area (m2), and ΔT is the temperature difference between the evaporator and condenser sections (° C.). As shown in FIG. 4, the efficiency or effective thermal conductivity of the randomized loop configurations is increased as compared to a uniform diameter configuration having the same number of loops. That is, the effective thermal conductivity of the 4-random configuration is greater than the effective thermal conductivity of the 4-uniform configuration. Similarly, the effective thermal conductivity of the 6-random configuration is greater than the effective thermal conductivity of the 6-uniform configuration. Although FIG. 4 is illustrative of four distinct configurations, the plot is provided for illustrative purposes of the improvements achieved through implementation of embodiments of the present disclosure. It will be appreciated that various factors, such as those that are part of the thermal conductivity equation may be different depending on the number of loops, length of the various evaporator, condenser, and adiabatic sections, cross-sectional area of the channels, and the temperature different. Additionally, the number of channels and / or loops is not limited to 4 or 6, but rather any number of channels and / or loops may be implemented without departing from the scope of the present disclosure (see, e.g., FIG. 5).As illustrated in FIG. 4, by implementing channels and / or loops of an oscillating heat pipe with randomized channel diameters, the thermal effectiveness of the oscillating heat pipe may be improved. In the illustrative embodiments shown and described thus far, the implication is that each channel has a uniform diameter / shape / size for the extent between the evaporator region to the condenser region, and that the variation is between the different channels. However, such uniform property within or along a single channel is not intended to be limiting. For example, in some embodiments, the channels may have variable diameters or properties along the length between the evaporator region and the condenser region. Such in-channel variations (e.g., tapering) are shown and described in, commonly owned and having shared inventorship, U.S. patent application Ser. No. 17 / 871,836, published as Application Publication No. 2024 / 0027139, filed Jul. 22, 2022, entitled “Oscillating Heat Pipes Operable within High Gravity Force Equivalent (G-Force) Environments, which is incorporated herein in its entirety. If such features are incorporated into an oscillating heat pipe of the present disclosure, the tapering or variance of one channel to the next may be implemented, but also the channel diameter along the length of an individual channel between the evaporator and condenser regions may also be varied.Referring now to FIG. 5, a schematic view of an oscillating heat pipe 500 in accordance with an embodiment of the present disclosure is shown. The oscillating heat pipe 500 may be similar to the oscillating heat pipes shown and described above, with the difference being that the oscillating heat pipe 500 includes two condenser regions 502a, 502b. As shown, the oscillating heat pipe 500 includes an evaporator region 504 having a plurality of bends 506a, 506b which can absorb heat from a heat source. The oscillating heat pipe 500, in this example, also includes the two condenser regions 502a, 502b each having a plurality of respective bends 508a, 508b which are arranged to transfer heat out of the fluid circuit of the oscillating heat pipe 500 to a heat sink or otherwise disperse or dispose of heat picked up by a working fluid in the evaporator region 504.The oscillating heat pipe 500 defines a first adiabatic region 510a between the evaporator region 504 and the first condenser region 502a and defines a second adiabatic region 510b between the evaporator region 504 and the second condenser region 502b. Each adiabatic region 510a, 510b includes intermediate channels 512a, 512b. In this example, the intermediate channels 512a, 512b in each respective adiabatic region 510a, 510b can be similar to the intermediate channels shown and described above. That is, the intermediate channels 512a, 512b may have randomly selected or different cross-sectional areas / channel diameters, at least relative to each other. For example, two adjacent intermediate channels 512a, 512b, may have cross-sectional areas that are different from each other and may be set relative or randomly selected based on a nominal channel diameter or other nominal channel property or characteristic (e.g., shape, size, diameter, depth, width, cross-sectional area, cross-sectional geometry, hydraulic diameter, etc.).

[0057] As described herein, oscillating heat pipes are provided having variable channel properties, such as shape, size, diameter, depth, width, cross-sectional area, cross-sectional geometry, hydraulic diameter. In accordance with some embodiments of the present disclosure, the variation is provided from one channel to the next such that a sequence of channels (one direction between evaporator and condenser) or loops (two directions, one from evaporator to condenser, a bend, and one from condenser to evaporator) are provided with different channel properties, which are randomly selected or defined relative to a nominal channel property. The variation is a variation that is greater than manufacturing tolerances and is a designed or intended variation in the channel property. The variation of the channels is with respect to a nominal value and not necessarily based on any other individual channels (or loops) of the oscillating heat pipe. As such, in some embodiments, two adjacent channels may have the same channel property. However, overall, the collective set of channels or loops have an aperiodic, asymmetric, or other non-repeating set of channel properties. This variability results in changes in hydraulic properties of the oscillating heat pipe which allows for improved efficiencies. That is, the randomness of the channels allows for increased random instabilities within the oscillating heat pipe, as compared to a system with uniform channel diameters, which tend to inherently resist the instabilities necessary for optimal oscillating heat pipe efficiency.

[0058] In accordance with some embodiments of the present disclosure, methods of manufacturing oscillating heat pipes are provided. The methods may include determining a desired number of channels of an oscillating heat pipe for a particular application. Next, a nominal channel property is determined, which is defined a nominal channel property value. The nominal channel property may be selected based on a variety of factors including, but not limited to, operating temperatures, working fluid properties, required heat removal, length of sections of channels, materials used for the oscillating heat pipe, or the like. With a nominal channel property selection, each channel of the oscillating heat pipe may be assigned a channel property value that is within a predetermined range or variance from the nominal channel property value. That is, each channel may be assigned a random channel property value that is within a preset or predefined range of the nominal channel property value. The range may be, for example, a fixed single value between 5% and 60%. With a nominal channel property value (Vn) and a predefined range (e.g., X % of Vn), the channels of the oscillating heat pipe may be assigned a random channel property value within the predefined range (e.g., between 0% and X % of Vn). The assigned channel property value may be a variation that is greater than or less than the nominal channel property value (Vn) (e.g., ±X % relative to the nominal channel property value (Vn)). In accordance with some embodiments, the oscillating heat pipe may be formed using additive manufacturing methodologies and processes. The end result is an oscillating heat pipe having a variable channel property for a set of channels with an aperiodic, asymmetric, or other non-repeating characteristic. In accordance with some embodiments of the present disclosure, the set of channels may be aperiodic with respect to channel properties such that two adjacent channels have different channel properties.

[0059] Advantageously, embodiments of the present disclosure provide for improved oscillating heat pipes. In accordance with embodiments of the present disclosure, oscillating heat pipes are formed having variable or aperiodic channel properties, which results in structurally imposed variation and hydraulic instabilities to thereby improve the instabilities within a working fluid of the oscillating heat pipe and improve thermal efficiencies thereof. The variations in the channel properties may be related to channel diameter, channel width, channel depth, channel shape, channel geometry, channel cross-sectional area, channel hydraulic diameter, or the like.

[0060] The use of the terms “a”, “an”, “the”, and similar references in the context of description (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or specifically contradicted by context. The modifier “about” used in connection with a quantity is inclusive of the stated value and has the meaning dictated by the context (e.g., it includes the degree of error associated with measurement of the particular quantity). All ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other. It should be appreciated that relative positional terms such as “forward,”“aft,”“upper,”“lower,”“above,”“below,” and the like are with reference to normal operational attitude and should not be considered otherwise limiting.

[0061] While the present disclosure has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the present disclosure is not limited to such disclosed embodiments. Rather, the present disclosure can be modified to incorporate any number of variations, alterations, substitutions, combinations, sub-combinations, or equivalent arrangements not heretofore described, but which are commensurate with the scope of the present disclosure. Additionally, while various embodiments of the present disclosure have been described, it is to be understood that aspects of the present disclosure may include only some of the described embodiments.

[0062] Accordingly, the present disclosure is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.

Examples

Embodiment Construction

[0031]As shown and described herein, various features of the disclosure will be presented. Various embodiments may have the same or similar features and thus the same or similar features may be labeled with the same reference numeral, but preceded by a different first number indicating the figure to which the feature is shown. Although similar reference numbers may be used in a generic sense, various embodiments will be described and various features may include changes, alterations, modifications, etc. as will be appreciated by those of skill in the art, whether explicitly described or otherwise would be appreciated by those of skill in the art. A more thorough description will now be provided with reference to the accompanying figures. The details shown in the figures are not necessarily to scale, but are shown to aid in understanding the features of the subject technology.

[0032]FIG. 1 schematically shows an example of an oscillating heat pipe 100 that may incorporate embodiments ...

Claims

1. An oscillating heat pipe comprising:a condenser region;an evaporator region; anda set of channels arranged between the condenser region and the evaporator region and defining at least a portion of a fluid circuit for a working fluid, wherein each channel of the set of channels has a respective channel property value that is a percentage variation from a nominal channel property value and the set of channels defines an aperiodic set of channels with respect to the channel property.

2. The oscillating heat pipe of claim 1, wherein each respective channel property value of the individual channels of the set of channels is a random value selected within a predefined range relative to the nominal channel property value.

3. The oscillating heat pipe of claim 2, wherein the predefined range is a set of values within 5% of the nominal channel property value.

4. The oscillating heat pipe of claim 2, wherein the predefined range is a set of values within a selected percentage range selected between 5%-60% of the nominal channel property value.

5. The oscillating heat pipe of claim 1, wherein the set of channels comprises a minimum of three channels.

6. The oscillating heat pipe of claim 1, wherein the fluid circuit comprises two or more sets of channels, wherein each set of channels of the two or more sets of channels is identical with respect to the number of channels and the respective channel properties of the channels forming each set of channels, and wherein the sets of channels are fluidly connected together.

7. The oscillating heat pipe of claim 1, wherein a first channel of the set of channels has a respective first channel property that is different from a second channel of the set of channels having a respective second channel property.

8. The oscillating heat pipe of claim 1, wherein the set of channels comprises at least three channels, wherein each channel of the at least three channels within the set of channels has a different channel property value.

9. The oscillating heat pipe of claim 1, wherein the channel property is a channel diameter.

10. The oscillating heat pipe of claim 1, wherein the channel property is a channel hydraulic diameter.

11. The oscillating heat pipe of claim 1, wherein the channel property is at least one of a channel diameter, a channel width, a channel depth, a channel shape, a channel geometry, a channel cross-sectional area, or a channel hydraulic diameter.

12. The oscillating heat pipe of claim 1, wherein each channel is fluidly connected to an adjacent channel by a bend to form the fluid circuit.

13. The oscillating heat pipe of claim 12, wherein a first channel of the set of channels is fluidly connected to a second channel by a bend formed in the evaporator region, and the second channel is connected to a third channel by a bend formed in the condenser region.

14. The oscillating heat pipe of claim 1, further comprising:an adiabatic region defined between the condenser region and the evaporator region, wherein each channel of the set of channels extends across the adiabatic region between the condenser region and the evaporator region.

15. A method of manufacturing an oscillating heat pipe, the method comprising:forming a condenser region;forming an evaporator region; andarranging a set of channels to extend between the condenser region and the evaporator region, wherein the set of channels are arranged to define at least a portion of a fluid circuit for a working fluid, wherein each channel of the set of channels has a respective channel property value that is a percentage variation from a nominal channel property value and the set of channels defines an aperiodic set of channels with respect to the channel property.

16. The method of claim 15, wherein each respective channel property value of the individual channels of the set of channels is a random value selected within a predefined range relative to the nominal channel property value.

17. The method of claim 15, wherein the forming of the condenser region and the evaporator region, and arranging the plurality of channels is performed using additive manufacturing.

18. The method of claim 15, wherein the channel property is at least one of a channel diameter, a channel width, a channel depth, a channel shape, a channel geometry, a channel cross-sectional area, or a channel hydraulic diameter.

19. The method of claim 15, wherein each channel is fluidly connected to an adjacent channel by a bend to form the fluid circuit.

20. The method of claim 15, further comprising:forming an adiabatic region between the condenser region and the evaporator region, wherein each channel of the set of channels extends across the adiabatic region between the condenser region and the evaporator region.

Images