Abstract:
A method and system for selectively dissipating thermal energy are provided. The system includes a heat-generating structure, a first heat sink, a second heat sink, and a heat transfer element. The heat-generating structure generates thermal energy. The first heat sink is in thermal communication with the heat-generating structure. The heat transfer element is configured to be selectively positioned between the first heat sink and the second heat sink to establish a path for the transfer of thermal energy between the first heat sink and the second heat sink. Upon positioning the heat transfer element between the first heat sink and the second heat sink, at least a portion of the thermal energy from the heat-generating structure is allowed to travel through the first heat sink and through the heat transfer element to the second heat sink.

Description:
TECHNICAL FIELD 
     The present disclosure is directed, in general, to cooling systems, and more specifically, to a system and method for a switchable heat sink. 
     BACKGROUND OF THE DISCLOSURE 
     In a variety of scenarios, a structure that may ordinarily be considered a suitable heat sink may suddenly become an unsuitable heat sink. This may occur as a result of changed conditions in a system. As one example, due to operating conditions, a heat sink may become undesirably hot, effectively removing its ability to serve as a heat sink. Additionally, in certain scenarios, the heat sink may become so hot that it becomes a source of heat or thermal energy as opposed to a sink for thermal energy. 
     SUMMARY OF THE DISCLOSURE 
     To address one or more of the above-identified deficiencies of the prior art, one embodiment of the disclosure is a system and method for a switchable heat sink. The system is configured to selectively dissipate thermal energy and includes a heat-generating structure, a first heat sink, a second heat sink, and a heat transfer element. The heat-generating structure generates thermal energy. The first heat sink is in thermal communication with the heat-generating structure. The heat transfer element is configured to be selectively positioned between the first heat sink and the second heat sink to establish a path for the transfer of thermal energy between the first heat sink and the second heat sink. Upon positioning the heat transfer element between the first heat sink and the second heat sink, at least a portion of the thermal energy from the heat-generating structure is allowed to travel through the first heat sink and through the heat transfer element to the second heat sink. 
     Certain embodiments of the disclosure may provide numerous technical advantages. For example, a technical advantage of one embodiment may include the ability to sink and un-sink a heat sink. Other technical advantages of other embodiments may include the capability to automatically switch a heat sink on and off based on a temperature of the heat sink. Yet other technical advantages of other embodiments may include the capability to switch between different heat sinks, depending on the temperatures of each. Still yet other technical advantages of other embodiments may include the capability to sink and un-sink a heat sink utilizing a fluid containing magnetic particles. 
     Although specific advantages have been enumerated above, various embodiments may include all, some, or none of the enumerated advantages. Additionally, other technical advantages may become readily apparent to one of ordinary skill in the art after review of the following figures and description. 
     Before undertaking the DETAILED DESCRIPTION below, it may be advantageous to set forth definitions of certain words and phrases used throughout this patent document. The term “couple” and its derivatives refer to any direct or indirect communication between two or more elements, whether or not those elements are in physical contact with one another. The terms “include” and “comprise,” as well as derivatives thereof, mean inclusion without limitation. The term “or” is inclusive, meaning and/or. The phrases “associated with” and “associated therewith,” as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, have a relationship to or with, or the like. The term “controller” means any device, system, or part thereof that controls at least one operation. A controller represents any suitable structure, such as hardware or a combination of hardware and software/firmware instructions. The functionality associated with any particular controller may be centralized or distributed, whether locally or remotely. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the present disclosure and its advantages, reference is now made to the following description taken in conjunction with the accompanying drawings, in which like reference numerals represent like parts: 
         FIGS. 1A and 1B  illustrate a switchable heat sink, according to an embodiment of the disclosure; 
         FIGS. 2A and 2B  illustrate another switchable heat sink, according to an embodiment of the disclosure; 
         FIGS. 3A and 3B  illustrate another switchable heat sink, according to yet another embodiment of the disclosure; 
         FIGS. 4A and 4B  illustrate another switchable heat sink, according to yet another embodiment of the disclosure; 
         FIGS. 5A and 5B  illustrate another switchable heat sink, according to yet another embodiment of the disclosure; 
         FIGS. 6A and 6B  illustrates aspects of a switchable heat sink that may be utilized in embodiments of the disclosure; 
         FIGS. 7A and 7B  illustrate additional aspects of a switchable heat sink that may be utilized in embodiments of the disclosure; 
         FIG. 8  illustrates how a sensor may be utilized to activate the actuators, according to an embodiment of the disclosure; 
         FIGS. 9A and 9B  illustrate another switchable heat sink within an environment, according to yet another embodiment of the disclosure; and 
         FIG. 10  illustrates a method for dissipating thermal energy, according to an embodiment of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     It should be understood at the outset that, although exemplary embodiments are illustrated below, the present invention may be implemented using any number of techniques, whether currently known or not. The present invention should in no way be limited to the example implementations, drawings, and techniques illustrated below, and no such limitation is intended. Additionally, the drawings are not necessarily drawn to scale. 
       FIGS. 1A and 1B  illustrate a switchable heat sink  100 , according to an embodiment of the disclosure. The switchable heat sink  100  in the embodiment of  FIGS. 1A and 1B  includes a heat-generating structure  110 , a first heat sink  120 , a heat transfer element  150 , and a second heat sink  180 . 
     The heat-generating structure  110  may be any device or structure that generates heat or thermal energy. In particular configurations, the heat-generating structure  110  may be electronics or circuits. The heat-generating structure  110  may have an associated first heat sink  120  to which thermal energy is designed to drain. 
     The heat transfer element  150  may be any material capable of transferring thermal energy, including solids, liquids, and gases. The second heat sink  180  represents any device or item capable of receiving thermal energy. Both the first heat sink  120  and the second heat sink  180  may be made of any suitable material including, but not limited to, metallic materials. 
     In operation, the heat transfer element  150  is selectively placed into position between the first heat sink  120  and the second heat sink  180  to allow the dissipation of thermal energy as indicated by arrows  81  and  82 . For example, if the heat sink  180  has a suitable temperature, the heat transfer element  150  may be positioned between the two. However, if the heat sink  180  does not have a suitable temperature, the heat transfer element  150  may be removed from between the first heat sink  120  and the second heat sink  180 . As an example of such suitable temperatures, if the second heat sink  180  has a temperature higher than first heat sink  120  (and absent a thermoelectric cooler), it would be undesirable to place the heat transfer element into position because the first heat sink  120  (and heat-generating structure  110 ) would not be dissipating thermal energy. Rather, thermal energy may undesirably be supplied to the first heat sink  120  from the second heat sink  180 . Accordingly, in particular configurations, the selective positioning of the heat transfer element  150  is dependent on a temperature of the second heat sink  180 . 
     Although a particular configuration of a switchable heat sink is shown in  FIG. 1  and particular configurations of switchable heat sinks will be shown and described herein, a variety of other configurations may be utilized, including those with more less or different components. 
       FIGS. 2A and 2B  illustrate another switchable heat sink  102 , according to an embodiment of the disclosure. The switchable heat sink  102  includes the heat-generating structure  110 , the first heat sink  120 , the heat transfer element  150 , and the second heat sink  180  as shown in  FIG. 1 . However, the switchable heat sink  110  also includes a third heat sink  182 . Similar to the second heat sink  180 , the third heat sink  182  represents any device or item capable of receiving thermal energy and may be made of any suitable material. 
     In particular configurations, it may be desirable to have multiple paths for the dissipation of thermal energy depending on the dynamics of the system, device, or equipment in which the switchable heat sink is contained, including, for example, the respective temperatures of the second heat sink  180  and the third heat sink  182 . 
     As a non-limiting operative example, in space-borne equipment such as space orbiting satellites and other space equipment, there may be a portion of the space-borne equipment exposed to the sun and another portion not exposed. Such exposure to the sun may vary over time. The portion exposed to the sun may have high temperatures and be unsuitable for a heat sink; however, the portions not exposed to the sun may have relatively cool temperatures and be suitable for a heat sink. Thus, the second heat sink  180  may represent a portion of the space-borne equipment whereas the third heat sink  182  may represent another portion of the space borne equipment. Depending on which portion is currently exposed to the sun, the switchable heat sink  102  may selectively move the heat transfer element  150  to dissipate the thermal energy from a heat-generating structure to the heat sink  180  or  182  not exposed to the sun. 
     In such multiple path scenarios, thermal energy may be dissipated through paths  83  and  84  in certain scenarios and paths  85  and  86  in other scenarios. Although two heat sinks  180 ,  182  are shown in this configuration, more than two may be utilized in other configurations where the heat transfer element  150  may be moved between any one of three or more paths for the thermal energy. 
       FIGS. 3A and 3B  illustrate another switchable heat sink  104 , according to yet another embodiment of the disclosure. The switchable heat sink  104  includes the heat-generating structure  110 , the first heat sink  120 , and the second heat sink  180  as shown in  FIG. 1 . However, the heat transfer element  152  is thermally conductive fluid that is capable of being moved in a chamber  155 . As described with reference to figures below, the thermally conductive fluid for the heat transfer element  152  may be a ferrofluid or colloidal suspension of magnetic particles that move according to a magnetic field applied thereto. In operation, the fluid is moved from one side of the chamber  155  to another to selectively allow dissipation of the thermal energy to the second heat sink  180  in a similar manner as that shown above with reference to  FIGS. 1A and 1B  to allow thermal energy to move along paths  87 ,  88 . 
       FIGS. 4A and 4B  illustrate another switchable heat sink  106 , according to yet another embodiment of the disclosure. The switchable heat sink  110  includes the heat-generating structure  110 , the first heat sink  120 , the second heat sink  180 , and the third heat sink  182  as shown in  FIGS. 2A and 2B , and the chamber  155  and heat transfer element as shown in  FIGS. 3A and 3B . In a manner similar to  FIGS. 2A and 2B , the movement of the heating transfer element  152  allows multiple paths for the transfer of thermal energy (e.g., paths  89 ,  91  or paths  92 ,  93 ). Additionally, although two are shown, three or more may be utilized in other configurations. 
       FIGS. 5A and 5B  illustrate another switchable heat sink  200 , according to yet another embodiment of the disclosure. The switchable heat sink  200  in the embodiment of  FIGS. 5A and 5B  includes a heat-generating structure and/or first heat sink (collectively item  212 ), a heat transfer element  250 , and a second heat sink  280  similar to that described in  FIGS. 1A and 1B . However, the heat transfer element  250  is shown being rotated out of position, for example, as shown by arrow  251 . Such a configuration may be utilized by other embodiments of the disclosure. 
       FIGS. 6A and 6B  illustrates aspects of a switchable heat sink  300  that may be utilized in embodiments of the disclosure. In  FIGS. 6A and 6B , a heat transfer element  352  is shown as a ferrofluid or colloidal suspension of magnetic particles in a movable magnetic field. Because of the magnetic properties of the heat transfer element  352 , movement of a magnet  372  will also cause movement of the heat transfer element  352 . Accordingly a movement of the magnet  372  to the right as shown in  FIG. 6A  shows how the heat transfer element  352  moves to the right and the movement of the magnet  372  to the left as shown in  FIG. 6B  shows how the heat transfer element  372  moves to the left. The remainder of the elements for the switchable heat sink, for example the first heat sink and the second heat sink, and the heat-generating structure are not shown. 
     An actuator  360  may be any actuator capable of moving the magnet  372  for appropriate positioning of the heat conducing element  352 , for example, as shown in  FIGS. 1A, 1B, 2A, 2B, 3A, 3B, 4A, and 4B . Non-limiting examples of actuators include, but are not limited to, electrically activated, power screws, pneumatic actuators, compressed fluid actuators, electromagnetic actuators, thermal energy actuators, and bimorph actuators. Yet other types of actuators will become apparent to one or ordinary skill in the art after review of this disclosure. This disclosure is not intended to be limited to any one actuator. Additionally, more than one and more than one type of actuator may be utilized in particular configurations. 
     Although the heat transfer element  372  is described as being a fluid in this embodiment, the disclosures herein may equally apply to configurations in which the heat transfer element  372  is a solid. In certain configurations, the actuator(s)  360  may act directly on the heat transfer element. In other configurations, the actuator(s)  360  may indirectly act on the heat transfer element. 
     In particular configurations, the actuator(s)  360  may take advantage of forces and/or energy that result from an operation of the system, device, or equipment in which the switchable heat sink is contained and/or a surrounding environment of the system, device, or equipment. Non-limiting examples include gravity, buoyancy, atmospheric pressure and/or temperature, inertia, the dissipated thermal energy from the heat-generating structure, and/or other parameters of the surrounding environment or combinations of the preceding. As a non-limiting example, in a device traveling at high speeds, forces of air against leading surfaces of the device may be used as an actuator, for example, to move the heat transfer element  352  from a first location to a second location leveraging pressure from such leading surface forces and vice versa. For example, a first valve may open to one side of a chamber for movement in a first direction and a second valve may open on a different side of the chamber for movement in a different direction. Additionally, the very thermal energy that is dissipated from the heat-generating structure may be utilized to develop a pressure in a chamber to move a mechanism from the second location to the first location or vice versa. Additionally, for example, in space-borne equipment, thermal energy from the sun may be harnessed to move a mechanism from a first location to a second location and vice versa. 
     An element  357  represents any of a variety of devices that may be keep either the heat transfer element  352  and/or magnet  372  in position after particular movement. Non-limiting examples for element  357  include selectively activated latches, valves, magnets, friction locks, and the like. A variety of other elements  357  should become apparent to one or ordinary skill in the art after review of the specification. Such elements  357  in particular configurations may be activated by the actuator(s)  360 . 
     In particular configurations, it may be desirable to only utilize energy during movement of the heat transfer element  352 . Accordingly, the actuator  360  may initiate movement of the heat transfer element  352  (e.g., by initiating movement of the magnet  372 ) and/or the element  357  and once in place, may no longer need to be activated to maintain the heat transfer element  352  in place. The element  357  may, for example, keep the heat transfer element  352  in place. As an example, a permanent magnets may respectively be placed on a solid form heat transfer element and corresponding locations in a chamber for positioning of the solid form heat transfer element. The actuator may overcome the magnetic attraction between the heat transfer element and a magnet at a first location to move the solid form heat transfer element to another location for additional magnetic attraction with a different magnet. 
       FIGS. 7A and 7B  illustrate additional aspects of a switchable heat sink  400  that may be utilized in embodiments of the disclosure. In  FIGS. 7A and 7B , the actuators are electromagnets  473 ,  475  that do not move. Selective activation of one of the electromagnets  473 ,  475  attracts the heat transfer element  452  to the respective electromagnets. Although generally shown as a block, the electromagnets  473 ,  475  may have selective portions of the electromagnet charged to facilitate movement. 
     Similar to that shown above, in particular configurations, an element  457  may be utilized to maintain the heat transfer element  452  in position without maintaining an activation of the electromagnets  473 ,  475 . A non-limiting example is a valve between respective portions of a chamber, for example, in the case where the heat transfer element  452  is a fluid. Element  457  may also include other structure, including those described above with reference to element  357 . 
       FIG. 8  illustrates how a sensor  585  may be utilized to activate the actuators  562 ,  564 , according to an embodiment of the disclosure. In particular configurations, the sensor  585  may be a thermal sensor that measures a temperature of a heat sink and issues a signal to the actuators  562 ,  564  to begin actuation in the case temperature exceeds a certain threshold condition (e.g., too hot or too cold). In addition to measuring a temperature of the heat sink, the sensor  585  may also measure the temperature of the heat-generating structure or the first heat sink (proximate to the heat-generating structure) and ambient temperature. By doing so, a temperature differential between the respectively measured items may be consulted to determine whether or not there is a suitable temperature differential for signaling the actuators  562 ,  564  to move the heat transfer element. As a non-limiting example, when the temperature differential between the second heat sink and the first heat sink is small, the heat transfer element may be moved out of position from between the first heat sink and the second heat sink. 
     In particular configurations, the sensor  585  may have a controller. In other configurations, multiple sensors  585  may be utilized. Additionally, in yet other configurations, the sensor  585  may be integrated into the actuators  562 ,  564 . As referenced above, in particular configurations, energy for actuator  562  and/or  564  may come from the thermal energy dissipated from the heat generating structure as shown by arrows  594 ,  595 . 
       FIGS. 9A and 9B  illustrate another switchable heat sink  500  within an environment, according to yet another embodiment of the disclosure. In the embodiment of  FIGS. 9A and 9B , the switchable heat sink  500  is shown selectively dissipating thermal energy to a skin of a missile  515 . Similar to that shown with reference to  FIGS. 3A, 3B, 6A, and 6B , the switchable heat sink  500  includes a heat-generating structure  510 , a first heat sink  520 , a second heat sink  580 , and a heat transfer element  552 , and a magnet  572 . In this configuration, the second heat sink  580  is the skin of the missile  515  and the heat-generating structure is electronics (e.g., an electronics stack) that may be utilized for operation of the missile  515 . 
     A sensor (not shown) may sense that the skin of the missile  515  is at a suitable temperature and accordingly have the heat transfer element  552  element moved from the off-position shown in  FIG. 9A  to the on-position in  FIG. 9B , allowing thermal energy to be dissipated to the skin of the missile  515 . Contrariwise, a sensor may also sense that the skin of the missile  515  is not at a suitable temperature (e.g., the missile is traveling at supersonic speeds) and accordingly have the heat transfer element  552  element moved from the on-position shown in  FIG. 9B  to the off-position shown in  FIG. 9A . In both such movements, the magnet  572  may be moved using any suitable actuator, for example, as described with reference to  FIGS. 6A and 6B . 
       FIG. 10  illustrates a method  600  for dissipating thermal energy, according to an embodiment of the disclosure. Although this method will be described, other methods may be utilized, including those disclosed herein. The method  600  of  FIG. 10  includes a sensing of the temperature of the second heat sink at step  610 . Additionally, according to certain embodiments, the temperature of the heat-generating structure and/or a first heat sink may also be sensed at step  610 . Moreover, in certain embodiments, ambient temperature may also be measured. Then, a determination is made at step  620  as to whether or not threshold(s) are satisfied. In certain embodiments, the threshold may be a temperature. In such embodiments, the threshold may be satisfied when the temperature of the second heat sink is below a value. In other embodiments, the threshold may be a temperature differential. In such embodiments, the threshold may be satisfied when the temperature differential between the second heat sink and the heat-generating structure and/or the first heat sink is greater than a value. Additionally, as referenced above, the threshold may actually be multiple thresholds. For example, in certain embodiments, a first value may need to be satisfied, for example, the ambient temperature may need to be low enough to serve as an ultimate heat sink. Then, a second value, which may be a temperature differential, may need to be satisfied. As another example, there may need to be both a large enough temperature differential between the first heat sink and the second heat sink and a large enough temperature differential between the second heat sink and ambient air. Yet other suitable threshold determinations will become apparent to one of ordinary skill in the art after review of this disclosure. 
     If the threshold(s) are satisfied, the process  600  moves on to step  630 . If not, the process  620  moves back to step  610 . 
     At step  630  the heat transfer element is positioned between the first and second heat sinks to allow a dissipation or transfer of thermal energy therethrough. 
     At step  640 , the temperature of the second heat sink is again measured. Additionally, similar to that described above, according to certain embodiments, the temperature of the heat-generating structure and/or a first heat sink may also be sensed at step  640 . Additionally, in certain embodiments, ambient temperature may also be measured. Then, at step  650 , a determination is made as to whether or not threshold(s) are satisfied. The threshold determination in step  650  may be the same as the threshold determination in step  610 . In other embodiments, the thresholds and any associated values may be different. If the threshold is not satisfied, the process  600  proceeds to step  660  where the heat transfer element is positioned away from between the first and second heat sinks and thermal energy is no longer allowed to dissipated from between the first and second heat sinks. If the threshold value is satisfied, the process  600  moves to step  640 . 
     Modifications, additions, or omissions may be made to the systems, apparatuses, and methods described herein without departing from the scope of the invention. The components of the systems and apparatuses may be integrated or separated. Moreover, the operations of the systems and apparatuses may be performed by more, fewer, or other components. The methods may include more, fewer, or other steps. Additionally, steps may be performed in any suitable order. As used in this document, “each” refers to each member of a set or each member of a subset of a set. 
     To aid the Patent Office, and any readers of any patent issued on this application in interpreting the claims appended hereto, applicants wish to note that they do not intend any of the appended claims or claim elements to invoke paragraph 6 of 35 U.S.C. Section 112 as it exists on the date of filing hereof unless the words “means for” or “step for” are explicitly used in the particular claim.