DYNAMICALLY ENHANCING HEAT TRANSFER THROUGH HEAT PIPES

A heat pipe system, method, and heat sink system to enhance heat transfer from a heat-generating component. The method includes generating heat with the heat-generating component. The method also includes transferring at least a portion of the heat to at least a portion of a volatile fluid within one or more heat pipes. The method further includes modifying, dynamically, an active heat transfer region of the one or more heat pipes, thereby dynamically modulating heat transfer from the heat-generating component through the one or more heat pipes.

BACKGROUND

The present disclosure relates to heat transfer from objects, and more specifically, to enhancing heat transfer from heat-generating components through heat pipes.

Many known modern processors include high-performance central processing units (CPUs) are configured to execute multiple parallel operations simultaneously. Such known processors tend to increase the power consumption over that of their predecessors. As such, heat generation also tends to increase and the heat needs to be removed to allow the respective processors to operate at their design capacities within the design temperature parameters. Many of these known processors use one or more heat pipes affixed to the external surfaces of the processors as the heat sinks to remove the generated heat. Many known heat pipes are sealed at manufacturing and utilize two primary paths which facilitate sufficient heat transfer from the respective processor.

SUMMARY

A heat pipe system, method, and heat sink system are provided for enhancing heat transfer from heat-generating components through heat pipes.

In one aspect, a heat pipe system to enhance heat transfer from a heat-generating component is presented. The heat pipe system includes one or more heat pipes. Each heat pipe of the one or more heat pipes includes an outer shell and a wick structure coupled to the outer shell. At least a portion of the wick structure defines a chamber therein and the chamber includes an evaporator portion and a condenser portion. The heat pipe system also includes one or more vapor blocking devices positioned in the chamber. Each vapor blocking device of the one or more vapor blocking devices is configured to dynamically modify an active heat transfer region of the condenser portion, thereby dynamically modulate heat transfer through the condenser portion. Accordingly, the heat pipe system facilitates enhanced heat transfer from heat sources through dynamically adjusting the heat transfer capabilities of the affected heat pipe automatically, thereby enhancing the dynamic modulating of the heat transfer capabilities of the respective heat pipe.

In another aspect, method to enhance heat transfer from a heat-generating component is presented. The method includes generating heat with the heat-generating component. The method also includes transferring at least a portion of the heat to at least a portion of a volatile fluid within one or more heat pipes. The method further includes modifying, dynamically, an active heat transfer region of the one or more heat pipes, thereby dynamically modulating heat transfer from the heat-generating component through the one or more heat pipes. Accordingly, the method facilitates enhanced heat transfer from one or more heat sources through dynamically adjusting the heat transfer capabilities of the affected heat pipes automatically, thereby enhancing the dynamic modulating of the heat transfer capabilities of the respective heat pipe.

In yet another aspect, a heat sink system to enhance heat transfer from a heat-generating component is presented. The heat sink system includes one or more heat pipes. Each heat pipe of the one or more heat pipes includes an outer shell and a wick structure coupled to the outer shell. At least a portion of the wick structure defines a chamber therein, and the chamber includes an evaporator portion and a condenser portion. The heat sink system also includes one or more vapor blocking devices positioned in the chamber. Each vapor blocking device of the one or more vapor blocking devices is configured to dynamically modify an active heat transfer region of the condenser portion, thereby dynamically modulate heat transfer through the condenser portion. The heat sink system also includes one or more cooling fins thermally coupled to the one or more heat pipes. Accordingly, the heat sink system facilitates enhanced heat transfer from one or more heat sources through dynamically adjusting the heat transfer capabilities of the affected heat pipes automatically, thereby enhancing the dynamic modulating of the heat transfer capabilities of the respective heat pipe.

The present Summary is not intended to illustrate each aspect of, every implementation of, and/or every embodiment of the present disclosure. These and other features and advantages will become apparent from the following detailed description of the present embodiment(s), taken in conjunction with the accompanying drawings.

DETAILED DESCRIPTION

Aspects of the present disclosure relate to implementing a heat pipe system, method, and heat sink system for enhancing heat transfer from heat-generating components through heat pipes. While the present disclosure is not necessarily limited to such applications, various aspects of the disclosure may be appreciated through a discussion of various examples using this context.

It will be readily understood that the components of the present embodiments, as generally described and illustrated in the Figures herein, may be arranged and designed in a wide variety of different configurations. Thus, the following details description of the embodiments of the apparatus, system, method, and computer program product of the present embodiments, as presented in the Figures, is not intended to limit the scope of the embodiments, as claimed, but is merely representative of selected embodiments.

Reference throughout this specification to “a select embodiment,” “at least one embodiment,” “one embodiment,” “another embodiment,” “other embodiments,” or “an embodiment” and similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, appearances of the phrases “a select embodiment,” “at least one embodiment,” “in one embodiment,” “another embodiment,” “other embodiments,” or “an embodiment” in various places throughout this specification are not necessarily referring to the same embodiment.

As used herein, “facilitating” an action includes performing the action, making the action easier, helping to carry the action out, or causing the action to be performed. Thus, by way of example and not limitation, instructions executing on one processor might facilitate an action carried out by semiconductor processing equipment, by sending appropriate data or commands to cause or aid the action to be performed. Where an actor facilitates an action by other than performing the action, the action is nevertheless performed by some entity or combination of entities.

Many known modern processors include high-performance central processing units (CPUs) and are configured to execute multiple parallel operations simultaneously. Such known processors tend to increase the power consumption over that of their predecessors. As such, heat generation also tends to increase and the heat needs to be removed to allow the respective processors to operate at their design capacities within the design temperature parameters. Many of these known processors use one or more heat pipes affixed to the external surfaces of the processors as the heat sinks to remove the generated heat. In addition, the use of heat pipes are prevalent through heating and ventilation and air-conditioning (HVAC) systems for energy recovery because they require little to no power. They are also used for thermal control of satellites and spacecraft.

As the power requirements for computing continue to increase, the computing industry is continually tasked with dissipating the associated increases in heat output commensurate with the increased power requirements, while reducing, or at least, mitigating any increase of cost, and also improving the efficiency of heat removal. Many known heat pipes are sealed at manufacturing and utilize two primary paths which facilitate sufficient heat transfer from the respective processor. At least most known heat pipe-based heat sinks provide a single design heat removal point throughout the expected lifetime of the heat pipe. However, many known modern processors are cycled through periods of high workload and low workload; therefore, most known heat pipes are not designed for both low and high power outputs, and as such, most known heat pipes are designed with a sub-optimized performance across most of the spectrum of power draws and heat generation. More specifically, many known heat sinks using heat pipes are most efficient only in a narrow band of the design operational spectrum of the respective heat-generating component.

In general, heat pipes utilize two primary paths which facilitate a significant amount of heat transfer away from the object to be cooled. Such heat pipes are filled with a volatile liquid designed for the range of expected heat removal from the respective heat sources. Therefore, the first path includes a vapor flow path that includes a liquid-to-vapor evaporator section that is typically directly, mechanically coupled to the heat source. The liquid is evaporated into a vapor that traverses the length of the first path a high speeds (i.e., near sonic velocities) to a condenser section that removes the heat energy in the vapor state to condense the vapor back into the liquid state. The heat removal from the vapor includes conduction into external heat fins and convection into the local environment. The condensed vapor in the liquid state flows back to the evaporator section through the inside walls of the heat pipe in a wick path through capillary action. Such mechanisms facilitate steady state heat transfer in through a two-phase evaporation-condensation cycle.

In some embodiments, a plurality of the described heat pipes are routinely used with a single heat sink, and in some embodiments, multiple heat pipes used for a single heat generating device. Therefore, in some instances where multiple heat pipes are used in a single heat sink, it is desirable to have more effective and efficient heat removal in some regions of the heat sink rather than others in order to more effectively cool components both in contact with the heat sink and within the more expansive system which the heat sink resides. For example, a heat sink using multiple heat pipes is used to remove heat generated by a multi-core processing device resident within a server cabinet.

At least one know method to enhance heat pipe operation includes a flattened heat pipe with a wick structure, where a thickness of the wick structure is changed so as to be thicker in a high-temperature portion where an exothermic element is disposed than in a low-temperature portion where none of the exothermic elements are disposed (see U.S. Pat. No. 9,188,396). However, such a flattened heat pipe has a fixed configuration that is not configured for dynamic changing.

Some known heat transfer systems use transport of heat by liquid-vapor phase change of a working fluid. Some of these system include using temperature-controlled flow modulation valves to independently control the flow of working fluid into and out of each respective heat exchanger in response to the heat load thereon (see U.S. Pat. No. 4,664,177).

At least some known cooling systems (see U.S. Patent Publication number 2022/0316764) use multiple cooling interfaces, i.e., any devices that may absorb heat from a heat source (e.g., electronic components) through direct contact or indirect contact, and through one or more fluid flow channels. Each of the cooling interfaces may include a liquid coolant inlet, a gas or vapor coolant outlet, and an inlet shut-off valve to control the flow of liquid coolant into the cooling interface. The system may further comprise a condenser. The liquid coolant may flow from the condenser, through a channel, to the liquid coolant inlet. The inlet shut-off valve may block the liquid coolant from entering the cooling interface or may permit the liquid coolant to enter the cooling interface. The cooling interface may be in contact with a heat source and heat may be transferred from the heat source to the liquid coolant. The liquid coolant may be vaporized and may exit the cooling interface through the gas coolant outlet to be directed to the condenser. In some embodiments, the cooling system may include one or more outlet shut-off valves that may aid in controlling the amount of coolant in the cooling interface and the pressure of the cooling interface, thereby maintaining the temperature of the heat source.

Some known embodiments of heat pipes include a control mechanism to modulate the flow of heat within the pipe (see U.S. Patent Publication number 2010/0218496). The control mechanism may comprise a thermal valve in the form of a rotatable circular plate which, depending on its position, allows, impedes, or obstructs the flow of vapor in the pipe thus effectively providing a means for modulating heat flow within the pipe.

Other known heat pipes control the heating medium flow rate by means of the movement of a magnetic fluid brought about by the movement of a magnetic flux generating part (see Japanese Patent Publication number JP-H0293293-A). A continuous array-type electromagnet comprising first to fourth electromagnets disposed around the exterior of the evaporator section and the heat insulator section of the pipe body proper, while a magnetic fluid is sealed inside the pipe body proper. When the electromagnets are OFF, the magnetic fluid is positioned in the lower part of the evaporator section due to its own weight to settle in the bottom, where the heat transfer takes place by means of the circulation of the heating medium. In order to stop the heat transfer, the first to fourth electromagnets are sequentially turned ON from the lower one to the upper one, thereby controlling a thermal flow by movement of the magnetic fluid accompanying movement of the magnetic flux generating part.

Some known heat transfer mechanisms maintain the temperature of a heat pipe within a certain range by controlling heat transfer resistance (see Japanese Patent Publication number JP-H04268193-A). The arrangement is such that a sealed container made from shape memory alloy, a wick made from shape memory alloy, an actuation liquid, and a rubber ring are provided. When the temperature falls, the shape in the center of a heat pipe is changed by elastic forces of the ring to narrow a passage. As a result, flow of vapor is controlled and heat transfer resistance at low temperature increases.

Other known heat transfer mechanisms (see Chinese Patent Publication CN-107144035-A) for geothermal energy extraction include a sleeve-type loop heat pipe that includes an evaporation section, an adiabatic section, and a reflux section. The evaporation section is located in the high-temperature heat storage. The surface heat exchanger is equipped with a condensation section. The condensation section exchanges heat with the outside. A one-way vale is provided between the adiabatic section and the condensation section. A valve or a steam pump, and a one-way throttle valve is set between the storage tank and the return section. The evaporation section, the adiabatic section, the condensation section, the storage tank, and the return section are connected end to end, and the working fluid in the storage tank passes through the return flow. The liquid working fluid return enters the evaporation section, and the liquid working fluid after entering the evaporation section absorbs heat and produces film boiling. Control of the liquid phase reflux mode and boiling mode of the evaporation section are controlled by passing the working fluid of the liquid storage tank through the reflux section, and this can adjust the effective liquid filling rate of the geothermal heat pipe in real time, thereby achieving stable and efficient extraction of geothermal energy.

Accordingly, there is a need in the computing industry to better dynamically modulate the heat transfer capabilities of the respective heat sink devices.

A heat pipe system, method, and heat sink system are disclosed and described herein for enhancing heat transfer from heat-generating components through heat pipes. In at least some of the embodiments described herein, the vapor path within a heat pipe is dynamically altered to adjust the localized heat flux in a manner that enhances component cooling in an electronics enclosure. Specifically, the present disclosure presents an improved, dynamic heat pipe system that adjusts its active heat transfer regions to direct the transfer of heat to the most appropriate section, or sections, of heat fins. More specifically, mechanisms to modulate the vapor's transport across a heat pipe chamber results in modifying the active heat transfer region of the heat pipe through at least one of blocking the vapor from selected portions of a condenser, or insulating a portion of the condenser from the vapor. Such mechanisms include dynamic, real-time positioning of devices within the heat pipe chamber to dynamically respond to changes in workload shifts across cores in a modern multi-core processor, including increases and decreases of processing activity for a particular core, as well as across multi-chip modules.

In addition, as presented herein, the repositioning of devices in the chamber changes the total volume of the heat pipe chamber that impacts the effective fill ratio (sometimes referred to as filling ratio) for a fixed mass of the volatile fluid resident in the heat pipe. As used herein, the fill ratio is defined as the volume of liquid presently in the heat pipe as compared to the volume of the evaporator section. As the fill ratio increases from for example, and without limitation, from dry (approximately 0%, i.e., substantially all of the liquid has been vaporized in the evaporator section) to approximately 85%, the thermal resistance to heat transfer decreases, thereby facilitating high heat transfer rates at lower differential temperatures between the object being cooled and the localized environment. As the fill ratio increases from approximately 85% to approximately 100%, the thermal resistance to heat transfer generally increases.

Accordingly, each heat pipe and heat sink embodiment presented herein facilitates enhanced heat transfer from one or more heat sources through dynamically adjusting the heat transfer capabilities of the affected heat pipes automatically, thereby better dynamically modulating the heat transfer capabilities of the respective heat sink devices.

Referring toFIG.1A, a schematic diagram of a heat pipe system100(herein referred to as “the system100”) is presented including a dynamically positionable hollow sleeve130in a first position, in accordance with some embodiments of the present disclosure. The system100includes an outer shell102and a wick structure104fixedly coupled to the outer shell102. The wick structure104defines a substantially cylindrical chamber106. The outer shell102and the wick structure104cooperate to define an evaporator section108and a corresponding evaporator portion110of the chamber106. The evaporator portion110is distinguished from the evaporator section108in that the evaporator section108includes the evaporator portion110, and the evaporator portion110is applied to the chamber106to distinguish the evaporator portion110of the chamber106from the other portions. Similarly, the outer shell102and the wick structure104cooperate to define a condenser section112and a corresponding condenser portion114of the chamber106. The condenser portion114is distinguished from the condenser section112in that the condenser section112includes the condenser portion114, and the condenser portion114is applied to the chamber106to distinguish the condenser portion114of the chamber106from the other portions, e.g., the evaporator portion110. A plurality of cooling fins116are thermally coupled to the outer shell102. A volatile liquid118is resident within the evaporator portion110of the chamber106.

In operation, the heat pipe system100is positioned proximate to, including in some embodiments thermally coupled to, a heat source (not shown inFIG.1A; however, seeFIG.4for the heat source490) that transmits heat120into the evaporator section108, and into the volatile liquid118that is resident within the evaporator portion110of the chamber106. The volatile liquid118is changed into a vapor stream122that is channeled through the chamber106into the condenser section112, i.e., the condenser portion114of the chamber106. The vapor stream122transmits the heat120to the plurality of cooling fins116that releases the heat124to the local environment (not labeled) as the condensing vapor stream122enters the wick structure104as condensate126. The condensate126is transported back to the evaporator section108through capillary action to replenish the inventory of volatile liquid118in the evaporator portion110of the chamber106.

In some embodiments, a vapor blocking device, i.e., the sleeve130, is disposed within the chamber106, where the sleeve130blocks, i.e., insulates, the vapor stream122from cooling fins116. The sleeve130includes a cylindrical wall132that defines a circular inlet port134and a circular outlet port136with a cylindrical cavity138therebetween. As such, the cylindrical configuration of the sleeve130defines a vapor flow path therethrough via the inlet port134, the cavity138, and the outlet port136. The sleeve130is configured to dynamically modify at least a portion of an effective active heat transfer region125A of the condenser section112, thereby dynamically modulate the transfer of the heat124through the condenser portion114. As used herein, the term “effective active heat transfer region” refers to the portion, or sum of portions, of the cooling fins116that are actively employed to capture and transport heat124from the outer shell102. This action is executed through using the wall132to insulate the selected portion of the active heat transfer region of the condenser section112including the respective portion of the wick structure104, the respective portion of the outer shell102, and the respective portion of the cooling fins116, from the vapor stream122flowing within the condenser section112.

Referring toFIG.1B, a schematic diagram of a cutaway view of a portion of the heat pipe system100including the dynamically positionable hollow sleeve130ofFIG.1Ais presented, in accordance with some embodiments of the present disclosure. Also, referring toFIG.1C, a schematic diagram of a magnified portion of the heat pipe system100including the dynamically positionable hollow sleeve130ofFIGS.1A and1Bis presented, in accordance with some embodiments of the present disclosure. Continuing to refer toFIG.1Aand continuing the numbering scheme thereof, the sleeve130is positioned in the chamber106(shown inFIG.1A) with a first travel guide140(not shown inFIG.1A) extending from the wall132of the sleeve130radially outward into a first guide track142(not shown inFIG.1A) formed within the wick structure104. Similarly, the sleeve130includes a second travel guide144(not shown inFIG.1A) extending from the wall132of the sleeve130radially outward into a second guide track146(not shown inFIG.1A) formed within the wick structure104.

The number of two guide tracks142and146and two travel guides140and144is not a limiting value, and any number of guide tracks142and146and any number of the travel guides140and144that enable operation of sleeve130and the system100as described herein is used. For example, and without limitation, in some embodiments, the sleeve130includes two or more travel guides140and144for each respective guide track142and146. In some embodiments, the system100includes three guide tracks separated at 120 degree intervals, and in some embodiments, the system includes four guide tracks separated at 90 degree intervals. In addition, the directly opposing configuration of the guide tracks142and146and the travel guides140and144is not limiting and any positioning of the guide tracks142and146and the travel guides140and144that enables operation of sleeve130and the system100as described herein is used. The length of the guide tracks142and146extend from an adiabatic region148of the chamber106(shown by a double-headed arrow inFIG.1A) to approximately the far end of the condenser portion114of the chamber106. The sizes of the travels guides140and144are configured to mitigate any potential for disengagement from, and any potential for excessive frictional interference with, travel thereof through the respective guide tracks142and146.

In one or more embodiments, the outer shell102is fabricated from copper, or a copper alloy. In some embodiments, the outer shell102is fabricated from aluminum. In some embodiments, the outer shell102is fabricated from any materials that enable operation of the system100as described herein. In at least some embodiments, the wick structure104is fabricated from cintered copper to form a porous configuration to use the capillary action to transport the condensed vapor from the condenser section112to the evaporator section108. In some embodiments, the sleeve130is fabricated from any materials that are susceptible to magnetic fields and that are chemically compatible with the volatile liquid118and its vapor stream122as well as the wick structure104. For example, and without limitation, in some embodiments, ferromagnetic materials such as iron, iron alloys, copper, and cooper alloys are used.

In at least some embodiments, the wall132of the sleeve130and the inner surface of the wick structure104define a circumferential clearance149to facilitate movement of the sleeve130along the guide tracks142and146, where the respective travel guides140and144facilitate radial support and stability of the sleeve130. In addition, the guide tracks142and146and the respective travel guides140and144facilitate maintaining the sleeve130at the designed relative distance from the wick structure104, i.e., the circumferential clearance149between the outside of the wall132of the sleeve130and the radially inner wall of the wick structure104. Also, the guide tracks142and146and the respective travel guides140and144facilitate maintaining axial alignment of sleeve130. Moreover, the guide tracks142and146and the respective travel guides140and144facilitate employment of a lock or positional brake (not shown) that engages when the magnetic coupling162is removed.

In addition, in some embodiments, the radially outer surface of the wall132is coated with a material to further facilitate free travel, e.g., and without limitation, TEFLON™. In some embodiments, the volatile liquid118includes additives that further facilitate lubrication of the radially outer surface of the wall132. In addition, the manufacturing processes for the system100are executed to mitigate surface roughness of one or both of the inner surface of the wick structure104and the radially outer surface of the wall132.

In some embodiments, system100as shown inFIGS.1A,1B, and1C(as well as at least some of the subsequent figures) is approximately 6 millimeters (mm) to approximately 8 mm in diameter and approximately 6 to 12 inches in length (FIGS.1A,1B, and1Care not drawn to scale). The thickness of the outer shell102and the wick structure104are each approximately 0.3 mm to approximately 0.5 mm such that the chamber106is approximately 4 mm to approximately 6.8 mm in diameter. The sleeve130is approximately 0.5 mm smaller in diameter than the chamber106, therefore the diameter of the sleeve130is approximately 3.5 mm to approximately 6.3 mm with the circumferential clearance149of approximately 0.25 mm. In addition, the circumferential clearance149between the outside of the wall132of the sleeve130and the radially inner wall of the wick structure104is not a perfect seal, where such small gaps will tend to choke or throttle the flow of the vapor stream122, but not prevent it. Accordingly, the close tolerances facilitate transit of the sleeve130through the chamber106, while mitigating flow of vapor stream122through the clearance149and not through the sleeve130.

In one or more embodiments, the system100further includes a modulating device150that is external to the chamber106that includes a magnet152, i.e., magnet152that is operably coupled to an actuator154through a coupling device156. In some embodiments, the actuator154is configured to receive position commands158directed toward the sleeve130and transmit position feedback160as a portion of a larger control system (not shown). In some embodiments, an input to the position commands158includes, without limitation, a measured temperature of the heat-generating component proximate the system100. The modulating device150is magnetically coupled to the sleeve130through a magnetic coupling162, where the modulating device150is configured to dynamically reposition the sleeve130within the chamber106at least partially based on a temperature of the heat-generating component. Specifically. the modulating device150is configured to transport the magnet152longitudinally along a portion of the length of the chamber106such that the sleeve130is positionable anywhere between the adiabatic region148and the far end of the condenser portion114. As shown inFIG.1A, with the sleeve130in the adiabatic region148, the effective active heat transfer region125A of the condenser section112is the entirety of the cooling fins116.

In some embodiments, the actuator154and the coupling device156are configured to move the magnet152orthogonally to the outer shell102to modulate the strength of the magnetic coupling162. In some embodiments, the strength of the magnetic coupling162is modulated through the actuator154adjusting an electric current (not shown) through the coupling device156(i.e., an electric conduit within) to the magnetic152. In some embodiments, more than one modulating device150is used. In some embodiments, rather than a magnet152, a magnetic field generated through any mechanism that enable operation of the system100as described herein is used. For example, rather than a track for the actuator154to travel, a magnetic field device that extends longitudinally along the length of the chamber106from the adiabatic region148to the far end of the condenser portion114is energized sectionally to transport the sleeve130.

In at least some embodiments, the cooling fins116have any length extending orthogonally to the outer shell102, including substantially similar lengths and variable lengths, and are fabricated from any materials, that enable operation of the system100as described herein. In those embodiments that include the magnet152, the cooling fins116define a longitudinal opening (not shown) to permit transit of the magnet152proximate the outer shell102. In some embodiments, the magnet152is withdrawn toward the actuator154to travel over the cooling fins116where the strength of the magnetic coupling162is modulated to facilitate the travel of the sleeve130.

Referring toFIG.1D, a schematic diagram of the heat pipe system100including the dynamically positionable hollow sleeve130ofFIGS.1A-1Cin a second position is presented, in accordance with some embodiments of the present disclosure. Continuing to refer toFIGS.1A-1Cand continuing the numbering scheme thereof, the sleeve130is shown in the second position as transported by the modulating device150through the embodiment thereof that includes the magnet152retracted orthogonally from the outer shell102to modulate the strength of the magnetic coupling162. The sleeve130has dynamically modified at least a portion of the previous effective active heat transfer region125A (seeFIG.1A) of the condenser section112to an effective active heat transfer region125D that includes only a portion of the cooling fins116. The remaining cooling fins116define an insulated section164of cooling fins116. As such, the system100has dynamically modulated the transfer of the heat124through the condenser section112.

Similarly, referring toFIG.1E, a schematic diagram of the heat pipe system100including the dynamically positionable hollow sleeve130ofFIGS.1A-1Din a third position is presented, in accordance with some embodiments of the present disclosure. Continuing to refer toFIGS.1A-1Dand continuing the numbering scheme thereof, the sleeve130is shown in the third position as transported by the modulating device150through the embodiment thereof that includes the magnet152retracted orthogonally from the outer shell102to modulate the strength of the magnetic coupling162. The sleeve130has dynamically modified at least a portion of the previous effective active heat transfer region125A (seeFIG.1A) and125D (seeFIG.1D) of the condenser section112to an effective active heat transfer region125E that includes only a portion of the cooling fins116. The remaining cooling fins116define an insulated section166of cooling fins116. As such, the system100has dynamically modulated the transfer of the heat124through the condenser portion114.

Therefore, the sleeve130is repositioned within the heat pipe chamber106to cover sections of the wick structure104to impede condensing of the vapor stream122proximate the sleeve130and the subsequent heat124transferred to the cooling fins116due to the insulating by the sleeve130. The sleeve130open at each end facilitates travel of the vapor stream122through the sleeve130to other sections of the heat pipe chamber106. The sleeve130does not block the migration of the condensate126in the wick structure104returning to the evaporator section108. In addition, the effective internal volume of the chamber106and the wick structure104does not change with the repositioning of the sleeve130, therefore the saturation pressure for the closed system remains substantially unchanged. Furthermore, the amount of volatile liquid118in the chamber106and the wick structure104does not need to be adjusted for optimal heat transfer as the excess condensate126fluid will be stored in the wick structure104which does not change.

In some embodiments, for example, those embodiments of system100with extended longitudinal lengths, as well as an extended condenser section112with a commensurate extended number of cooling fins116, more than one sleeve130is used to create multiple effective active heat transfer regions125D and125E.

Referring toFIG.2A, a schematic diagram of a heat pipe system200(herein referred to as “the system200”) including a dynamically positionable valve270in a first position is presented, in accordance with some embodiments of the present disclosure. Also referring toFIG.2B, a schematic diagram of the system200including the positionable valve270ofFIG.2Ain a second position is presented, in accordance with some embodiments of the present disclosure. Further referring toFIG.2C, a schematic diagram of a cutaway view of a portion of the system200including the positionable valve270ofFIGS.2A-2Bis presented, in accordance with some embodiments of the present disclosure. InFIG.2C, the valve270is shown in the position indicated inFIG.2B. The system200is similar to the system100as described inFIGS.1A-1Ewith at least one exception, i.e., rather than a modulating device150including a sleeve130, the system200includes a modulating device250that includes the positionable valve270, where the valve270is a vapor blocking device. The valve270is configured to at least partially isolate at least a portion of the condenser portion214from at least a portion of the vapor stream222flowing through the condenser portion214.

In at least some embodiments, the valve270is a butterfly valve that is resident within the chamber206. In some embodiments, any valve type that enables operation of the system200as described herein is used. InFIG.2A, the valve270is shown in an open position, and inFIGS.2B and2C, the valve270is shown in the closed position.

Referring only toFIG.2C, the valve270includes a rotatable disk272and two cylindrical pins274, where the pins274are resident within their respective pin cavities276. One of the pins274is rotatably coupled to an actuator254through a coupling member256as indicated by arrow257. In some embodiments, the actuator254is configured to receive position commands258directed toward the valve270and transmit position feedback260as a portion of a larger control system (not shown). In some embodiments, an input to the position commands258includes, without limitation, a measured temperature of the heat-generating component proximate the system200. Some embodiments include an outer shell sealing device278at least partially embedded within the outer shell202to mitigate a potential for liquid or vapor leakage from the chamber206. In at least some embodiments, the disk272of the valve270and the inner surface of the wick structure204define a circumferential clearance249to facilitate movement of the disk272, where the respective pins274facilitate radial support and stability of the disk272. In addition, in some embodiments, the radially outer surface of the disk272is coated with a material to further facilitate free travel, e.g., and without limitation, TEFLON™. In some embodiments, the volatile liquid218includes additives that further facilitate lubrication of the radially outer surface of the disk272. In addition, the manufacturing processes for the system200are executed to mitigate surface roughness of one or both of the inner surface of the wick structure204and the radially outer surface of the disk272. In some embodiments, there is a design leakage of vapor stream222through the clearance249.

Referring again toFIGS.2A and2B, in at least some embodiments, the valve270is a binary device, i.e., the state of the valve270is either one of fully open (as shown inFIG.2A) or fully closed (as shown inFIG.2B). In such embodiments, valve is configured to dynamically modify at least a portion of an effective active heat transfer region225A of the condenser section212, thereby dynamically modulate the transfer of the heat224through the condenser portion214. As shown inFIG.2A, with the valve270fully open, the effective active heat transfer region225A of the condenser section212is the entirety of the cooling fins216. As shown inFIG.2B. with the valve270fully closed, the valve270has been dynamically modified such that at least a portion of the previous effective active heat transfer region225A (seeFIG.2A) of the condenser section212is decreased to an effective active heat transfer region225B that includes only a portion of the cooling fins216. The remaining cooling fins216define an isolated section264of cooling fins216. As such, the system200has dynamically modulated the transfer of the heat224through the condenser portion214.

In some embodiments, the valve270is modulated through the full range of the associated 90 degree motion rather than the binary open and closed states of the valve270. Such embodiments provide more granularity to the vapor stream222to maintain at least some heat transfer of the heat224through the section264of the cooling fins216.

In some embodiments, for example, those embodiments of system200with extended longitudinal lengths, as well as an extended condenser section212with a commensurate extended number of cooling fins216, and since the valve270is in a fixed location, more than one valve270is used to create a series of active heat transfer regions225B.

Referring toFIG.3A, a schematic diagram of a heat pipe system300(herein referred to as “the system300”) including a dynamically positionable blocking object380in a first position is presented, in accordance with some embodiments of the present disclosure. Also referring toFIG.3B, a schematic diagram of the system300including the positionable blocking object380ofFIG.3Ain a second position is presented, in accordance with some embodiments of the present disclosure. The system200is similar to the system100as described inFIGS.1A-1Eand the system200as described inFIGS.2A-2Cwith at least one exception, i.e., rather than a modulating device150including the sleeve130, or a modulating device250that includes the positionable valve270, the system300includes a modulating device, i.e., the positionable blocking object380, where the blocking object380is a vapor blocking device. The blocking object380is configured to at least partially block, i.e., isolate at least a portion of the condenser portion314from at least a portion of the vapor stream322flowing through the condenser portion314. InFIG.3A, the blocking object380is shown in an idle position at the far end of the condenser portion314of the chamber306, and inFIG.3B, the blocking object380is shown in an active position.

In at least some embodiments, the blocking object380is a spherical object that is resident within the chamber306, where the diameter of the blocking object380is slightly smaller than the diameter of the chamber306. For example, in some embodiments, with the magnetic coupling362adjusted to a magnetic field strength that substantially centers the blocking object380in the center of the condenser portion314of the chamber306, a circumferential clearance (not shown) of approximately 0.25 mm to approximately 0.5 mm is established between the outer surface of the blocking object380and the radially inner wall of the wick structure304. In some of these embodiments, there is a design leakage of vapor stream322through the clearance. Therefore, in such embodiments, a perfect seal is not established, where such small gaps will tend to choke or throttle the flow of the vapor stream322, but not prevent it. Accordingly, the close tolerances facilitate transit of the blocking object380through the chamber306, while mitigating flow of vapor stream322through the clearance.

In addition, in some embodiments, the radially outer surface of the blocking object380is coated with a material to further facilitate free travel, e.g., and without limitation, TEFLON™. In some embodiments, the volatile liquid318includes additives that further facilitate lubrication of the radially outer surface of the blocking object380. In addition, the manufacturing processes for the system300are executed to mitigate surface roughness of one or both of the inner surface of the wick structure304and the radially outer surface of the blocking object380.

In some embodiments, any shape of object that enables operation of the system300as described herein is used, including, for example, a cylindrical object similar to the sleeve130(seeFIGS.1A-1E), however, in such embodiments, the object is solid with no cylindrical cavity138.

In one or more embodiments, the system300further includes a modulating device350that is similar to the modulating device150(shown inFIG.1A). Specifically, the modulating device350is substantially external to the chamber306that includes a magnet352, i.e., magnet352that is operably coupled to an actuator354through a coupling device356. In some embodiments, the actuator354is configured to receive position commands358directed toward the blocking object380and transmit position feedback360as a portion of a larger control system (not shown). In some embodiments, an input to the position commands358includes, without limitation, a measured temperature of the heat-generating component proximate the system300. The modulating device350is magnetically coupled to the blocking object380through the magnetic coupling362, where the modulating device350is configured to dynamically reposition the blocking object380within the chamber306at least partially based on a temperature of the heat-generating component. Specifically. the modulating device350is configured to transport the magnet352longitudinally along a portion of the length of the chamber306such that the blocking object380is positionable anywhere within the condenser portion314, including the far end of the condenser portion314. As shown inFIG.3A, with the blocking object380in the idle position at the far end of the condenser section312, the effective active heat transfer region325A of the condenser section312is the entirety of the cooling fins316.

In some embodiments, the actuator354and the coupling device356are configured to move the magnet352orthogonally to the outer shell302to modulate the strength of the magnetic coupling362(as previously described further with respect toFIGS.1A-1E). In such embodiments, the magnet352is withdrawn toward the actuator354to travel over the cooling fins316where the strength of the magnetic coupling362is modulated to facilitate the travel of the blocking object380. In some embodiments, the strength of the magnetic coupling362is modulated through the actuator354adjusting an electric current (not shown) through the coupling device356(i.e., an electric conduit within) to the magnet352. In some embodiments, a portion of the cooling fins316(shown in phantom inFIGS.3A and3B) define a longitudinal opening (not shown) to permit transit of the magnet352proximate the outer shell302.

In some embodiments, more than one modulating device350is used. In some embodiments, rather than a magnet352, a magnetic field generated through any mechanism that enable operation of the system300as described herein is used. For example, rather than a track for the actuator354to travel, a magnetic field device that extends longitudinally along a portion of the length of the chamber306such that the blocking object380is positionable anywhere within the condenser portion314, including the far end of the condenser portion314, is used.

In at least some embodiments, the blocking object380is configured to dynamically modify at least a portion of the effective active heat transfer region325A (seeFIG.3A) of the condenser section312, thereby dynamically modulate the transfer of the heat324through the condenser portion314. As shown inFIG.3A, and as previously described, with the blocking object380in the idle position, the effective active heat transfer region325A of the condenser section312is the entirety of the cooling fins316. As shown inFIG.3B, with the blocking object380in a blocking position, the flow of vapor stream322has been dynamically modified such that at least a portion of the previous effective active heat transfer region325A of the condenser section312is decreased to an effective active heat transfer region325B that includes only a portion of the cooling fins316. The remaining cooling fins316define an isolated section364of cooling fins316. As such, the system300has dynamically modulated the transfer of the heat324through the condenser portion314.

Referring toFIG.4, a schematic diagram of a heat sink system400including a plurality of U-shaped heat pipes, i.e., a first heat pipe492and a second heat pipe494coupled to a heat source490, in accordance with some embodiments of the present disclosure. In general, the numbering scheme ofFIGS.1A-3Bare followed with the exceptions and additions clearly evident. In some embodiments, the heat source490is a multi-core processing device. In some embodiments, the heat source490is any heat-generating component that can be effectively cooled through the heat pipe embodiments described herein. The description ofFIG.4is primarily directed toward the first heat pipe492, where the second heat pipe494is substantially similar. The first heat pipe492includes a horizontally-oriented evaporator section408that is thermally coupled to the heat-generating component, i.e., the heat source490. The first heat pipe492also includes two or more vertically-oriented condenser sections, i.e., a first condenser section412A and a second condenser section412B that are each coupled in fluid communication with the evaporator section408. The heat sink system400also includes a plurality of cooling fins, i.e., a first set of cooling fins416A thermally coupled to the first condenser section412A and a second set of cooling fins416B thermally coupled to the second condenser section412B.

In at least some embodiments, each condenser section412A and412B includes one or more vapor blocking devices. As presented for illustrative purposes, the first condenser section includes a plurality of sleeves430A1and430A2, where each of the sleeves430A1and430A2are substantially similar to the sleeve130(shown inFIGS.1A-1E). The modulating devices for the sleeves430A1and430A2that are substantially similar to the modulating devices described for the sleeve130, including the modulating device150, are not shown inFIG.4. Also, between each of the condenser sections412A and412B and the evaporator section408a first valve470A and a second valve470B, respectively, is positioned. The valves470A and470B are substantially similar to the valve270(shown inFIGS.2A-2C), where the associated modulating devices, including the modulating device250, are not shown inFIG.4. The first valve470A is shown in the closed position, thereby effectively isolating the first condenser section412A from the evaporator section408. As such, all of the cooling fins416A are isolated and there is no effective active heat transfer region of the condenser section412A.

In one or more embodiments, in contrast to the first condenser section412A, the second valve470B is shown in the open position. In addition, the second condenser section412B includes a blocking object480that is substantially similar to the blocking object380(shown inFIGS.3A-3B), where the modulating devices for the blocking object480that is substantially similar to the modulating devices described for the blocking object380, including the modulating device350, are not shown inFIG.4. The position of the blocking object480defines an isolated section464B of the cooling fins416B and an effective active heat transfer region425B. Similarly, in some embodiments, the valve470A is open, and the positions of the sleeves430A1and430A2define two isolated sections464A1and464A2of the cooling fins416A and two effective active heat transfer regions425A1and425A2.

Referring toFIG.5, a flowchart is provided illustrating a process500for enhancing heat transfer from heat-generating components through heat pipes, in accordance with some embodiments of the present disclosure. Also referring toFIGS.1A-4, the process500includes generating502heat with the heat-generating component, e.g., and without limitation, the heat source490. The process500also includes transferring504at least a portion of the heat to at least a portion of a volatile fluid within one or more heat pipes. For example, and without limitation, heat energy120,220, and320is transferred into the respective evaporator sections108,208,308, as well as the evaporator section408, of the respective heat pipe systems100,200, and300, as well as the heat sink system400. The process500further includes modifying506, dynamically, an active heat transfer region (see the effective active heat transfer regions125A,125B,125C,225A,225B,325A,325B,425A1,425A2, and425B) of the one or more heat pipes, thereby dynamically modulating heat transfer from the heat source490through the one or more heat pipes.

In one or more embodiments, the process500also includes repositioning508, dynamically, within the one or more heat pipes, through one or more respective modulating devices (see the modulating devices150,250, and350in their respective figures), one or more vapor blocking devices (see the sleeve130, the valve270, and the blocking device380in their respective figures). Accordingly, the repositioning508of the respective modulating devices150,250, and350facilitate the modulation of the heat transfer through the respective heat pipe by positioning the respective vapor blocking devices to either insulate or isolate the respective cooing fins as described further.

In some embodiments, the repositioning508operation of the one or more vapor blocking devices includes insulating510, dynamically, at least a portion of the active heat transfer region of the one or more heat pipes, from at least a portion of a vapor flowing through the active heat transfer region. The sleeves130,430A1, and430A2are repositioned to extend over at least a portion of the cooling fins116,416A, and416B to define the insulated sections164of cooling fins116, and the two isolated sections464A1and464A2of the cooling fins416A. For the system100, the streams of vapor stream122are insulated from the wick structure104, the outer shell102, and the respective cooling fins116by the sleeve130. In turn, for both the system100and the heat sink system400, respective effective active heat transfer regions125A,125B.125C,425A1, and425A2result as a consequence. Examples include the effective active heat transfer regions125B and125C are different from the initial effective heat transfer region125A responsive to the repositioning508of the sleeve130and the subsequent insulating510. Accordingly, the insulating510of the respective cooling fins from the vapor within the heat pipe chamber effectively changes the heat transfer through the heat pipe by effectively removing at least a portion of the cooing fins from the heat transfer process.

In some embodiments, the repositioning508operation of the one or more vapor blocking devices includes isolating512, dynamically, at least a portion of the active heat transfer region of the one or more heat pipes, from at least a portion of a vapor flowing through the active heat transfer region. The valves270(as well as the valves470A and470B), and the blocking objects380(and480), are repositioned508as described elsewhere herein. Such repositioning508to define those portions of the respective chambers206and306that are isolated from the respective streams of vapor streams222and322, i.e., the isolated section264of the cooling fins216and the isolated section364of the cooling fins316. Such isolation512defines the effective active heat transfer regions225A and225B of the condenser section212, and the effective active heat transfer regions325A and325B of the condenser section312. One example includes the effective active heat transfer region225B is different from the initial effective heat transfer region225A responsive to the repositioning508of the valve270and the subsequent isolating512. A second example includes the effective active heat transfer region325B is different from the initial effective heat transfer region325A responsive to the repositioning508of the blocking object380and the subsequent isolating512. Accordingly, the isolating512of the respective cooling fins from the vapor within the heat pipe chamber effectively changes the heat transfer through the heat pipe by effectively removing at least a portion of the cooing fins from the heat transfer process.

A feature of the systems and methods described herein includes changing, dynamically, a fill ratio within the respective heat pipes as a result of modifying506, dynamically, the active heat transfer region of the respective heat pipes. Specifically, the repositioning of devices in the chamber changes the total volume of the heat pipe chamber that impacts the effective fill ratio (sometimes referred to as filling ratio) for a fixed mass of the volatile fluid (liquid and vapor states combined) resident in the heat pipe. Since the fill ratio is defined as the volume of liquid (thereby excluding the vapor) presently in the heat pipe as compared to the volume of the evaporator section, the fill ratio increases from an initial value to a different, i.e., greater value as the vapor generation decreases as a result of a decreasing temperature of the heat source, and the sum of the liquid in the wick structure and the evaporator section increase. As the fill ratio increases from for example, and without limitation, from dry (approximately 0%, i.e., substantially all of the liquid has been vaporized in the evaporator section) to approximately 85%, the thermal resistance to heat transfer decreases, thereby facilitating high heat transfer rates at lower differential temperatures between the object being cooled and the localized environment. As the fill ratio increases from approximately 85% to approximately 100%, the thermal resistance to heat transfer increases.

The systems and methods described herein result in a more efficient and effective dynamic modulating of the heat transfer capabilities of the respective heat sink devices. Specifically, systems and methods presented herein provide for an improved, dynamic heat pipe that can adjust its active regions to direct the heat transfer to the most appropriate section of cooling fins. This facilitates the heat sink dynamically responding to workload shifts across cores in a modern multi-core processor. As such, the systems and methods described herein facilitate broadening the design operational spectrum for effective and efficient heat removal to more closely approach the design operational spectrum of the respective heat-generating component. Accordingly, the systems and methods described herein enhance the capabilities of the respective heat pipes to dynamically adjust the physical locations of the highest performing regions of the heat sink in response to varying heat source location as the processing loads of the various cores are changing.

Further, dynamically adjusting the locations of the highest performing regions of the heat sink, in some instances, where multiple heat pipes are used in a single heat sink, the result of manipulating the heat dissipated in specific regions of the heat pipe facilitates more effective cooling of specific components. Such manipulating of a path of the vapor stream within a heat pipe adjusts the heat flux in a manner that enhances heat removal from components in an electronics enclosure. Specifically, a more efficient heat flux in some regions of the heat sink are defined in order to more effectively cool components both in contact with the heat sink and within the larger computing system, e.g., the enclosure in which the heat sink resides.

Accordingly, each heat sink embodiment presented herein facilitates enhanced heat transfer from one or more heat sources through dynamically adjusting the heat transfer capabilities of the affected heat pipes automatically, thereby enhancing the dynamic modulating of the heat transfer capabilities of the respective heat sink devices. In the present disclosure, at least some of the embodiments described are directed toward heat removal from processing devices. However, in addition, the use of the systems and methods presented herein are adaptable to HVAC systems as energy recovery mechanisms and for thermal control of satellites and spacecraft.