Heat conduction and electronics cooling system

Abstract

Heat pipe (106) for an electronics cooling system (100) with an electronic component (104), the heat pipe (106) comprising: a tube (108) having an inner diameter surface (110) defining a bore (112), the tube (108) having a first end (114) and a second end (116) along the bore (112); a sorbent material (122) coated on the inner diameter surface (110) of the tube (108); a first liquid (120) contained in the bore (112) of the tube (108) and having a first boiling temperature; and a second liquid (124) adsorbed by the sorbent material (122) and having a second boiling temperature higher than the first boiling temperature of the first liquid (120); wherein the first liquid (120) evaporates into a first vapor (126) in response to the tube (108) receiving heat from the electronic component (104) and the first liquid (120) reaching the first boiling temperature, and the first vapor (126) moves to the second end (116) where the first vapor (126) dissipates heat through the tube (108) and condenses into the first liquid (120); wherein the second liquid (124) is desorbed from the sorbent material (122) in response to the second liquid (124) and the sorbent material (122) reaching a predetermined desorption temperature which is lower than the second boiling temperature, and the second liquid (124) evaporates to a second vapor (128) when the second liquid (124) reaches the second boiling temperature.

Description

[0001] The present description relates generally to the cooling of electronics and, more particularly, to a heat pipe having multiple fluids and associated boiling temperatures that differ from one another to provide multiple stages of cooling.

[0002] Electronics generate heat when electrical current flows through them. The amount of heat depends on the power, device characteristics, and circuit design. The resistance of processors, driver circuits, power circuits, and memory contributes to some heat and power dissipation. To avoid circuit failures or malfunctions, electronics must operate and remain within safe temperature limits. While some circuits operate without additional cooling, others have mechanisms for heat dissipation.

[0003] Existing heat pipes for electronics include an elongated tube containing a single liquid. The tube has a first end that transfers heat from an electronic component to the liquid, causing the liquid to evaporate into a vapor when the liquid temperature reaches its boiling point. The heat pipe further includes a second end that transfers heat from the vapor to the surroundings to condense the vapor into the liquid when the vapor temperature drops below the boiling point. The heat pipe further includes a wicking material connecting the first and second ends to return the condensed liquid from the second end to the first end.In a desiccation state where all the liquid evaporates to vapor, the vapor does not move to the second end to cool, and condensate does not form and return to the first end, so the ability of the heat conductor to cool is adversely affected.

[0004] US 2006 / 0 054 308 A1 describes a heat pipe comprising a fluid conduit, a first working fluid having a first boiling point disposed in the fluid conduit, and a second working fluid having a second boiling point different from the first boiling point disposed in the fluid conduit. The first and second working fluids are disposed in the fluid conduit of the heat pipe such that, during operation, the heat from the hot body vaporizes the first working fluid, while the second working fluid remains liquid. The vaporized first working fluid then transports the second working fluid through the fluid conduit to thermally transfer the heat.

[0005] DE 10 2006 028 372 A1 describes a heat exchanger, in particular a sorption, reaction and / or heat pipe, with a plurality of fibers, wherein a plurality of the fibers are attached with their one end to or in the wall.

[0006] It can be considered a task to specify new and improved heat pipes for electronics.

[0007] The object is achieved by a heat pipe for an electronics cooling system according to claim 1 and an electronics cooling system according to claim 8. Furthermore, an exemplary method for operating an electronics cooling system is described.

[0008] A heat pipe according to the invention is provided for cooling an electronic component of a printed circuit board. The heat pipe comprises a tube having an inner diameter surface defining a bore, the tube having a first end and a second end along the bore. The heat pipe further includes a sorbent material coated on the inner diameter surface of the tube. The heat pipe further includes a first liquid contained within the bore of the tube and having a first boiling temperature. The heat pipe further includes a second liquid adsorbed by the sorbent material and having a second boiling temperature higher than the first boiling temperature of the first liquid. The first liquid evaporates into a first vapor in response to the tube receiving heat from the electronic component and the first liquid reaching the first boiling temperature.The first vapor flows to the second end of the tube, where the first vapor dissipates heat through the tube and condenses into the first liquid. The second liquid is desorbed from the sorbent material in response to the second liquid and the sorbent material reaching a predetermined desorption temperature that is lower than the second boiling temperature. The second liquid evaporates into a second vapor in response to the second liquid reaching the second boiling temperature.

[0009] In one embodiment, the sorbent material is configured to desorb at least a portion of the second liquid into the bore before all of the first liquid evaporates to the first vapor.

[0010] In another embodiment, the inner diameter surface defines at least one axial groove extending between the first end and the second end for drawing the first liquid from the second end to the first end by capillary action.

[0011] In another embodiment, a plurality of axial grooves are arranged circumferentially spaced from one another on the inner diameter surface.

[0012] In another embodiment, the sorbent material is spaced from the second end of the tube so that the condensed first liquid flows from the bore to the axial grooves. The sorbent material is further spaced from the first end of the tube so that the first liquid flows back from the axial grooves into the bore.

[0013] In another embodiment, the first liquid is water.

[0014] In another embodiment, the second liquid is ethylene glycol.

[0015] An electronics cooling system according to the invention comprises an electronic component that generates heat. The electronics cooling system further comprises a heat pipe for cooling the electronic component, and the heat pipe comprises a tube with an inner diameter surface defining a bore. The tube has a first and a second end along the bore. The heat pipe further includes a sorbent material coated on the inner diameter surface of the tube proximate the first end. The heat pipe further includes a first liquid contained within the bore of the tube and having a first boiling temperature. The heat pipe further includes a second liquid adsorbed by the sorbent material and having a second boiling temperature. The second boiling temperature of the second liquid is higher than the first boiling temperature of the first liquid.The first liquid evaporates into a first vapor in response to the first end of the tube receiving heat from the electronic component and the first liquid reaching the first boiling temperature. The first vapor moves toward the second end, where the first vapor conducts heat through the tube and condenses into the first liquid. The second liquid is desorbed from the sorbent material in response to the second liquid and the sorbent material reaching a predetermined desorption temperature that is below the second boiling temperature. The second liquid evaporates into a second vapor in response to the second liquid reaching the second boiling temperature.The electronics cooling system further includes one or more thermocouples attached to the electronic component and / or the heat pipe to generate a first temperature signal associated with the temperature of the first fluid. The electronics cooling system further includes a controller electrically connected to the thermocouple. The controller compares the temperature of the first fluid to a first temperature threshold in response to the controller receiving the first temperature signal from the thermocouple. The controller generates a first warning signal when the controller determines that the temperature of the first fluid is above the first temperature threshold.The controller is electrically coupled to an indicator device for displaying a first warning indicating that the first fluid is approaching the first temperature threshold in response to the indicator device receiving the first warning signal from the controller.

[0016] In one embodiment, the thermocouple generates a second temperature signal associated with the temperature of the second liquid. The controller compares the temperature of the second liquid to a second temperature threshold in response to the controller receiving the second temperature signal from the thermocouple. The controller generates a second warning signal in response to the controller determining that the temperature of the second liquid is above the second temperature threshold. The indicator displays a second warning indicating that the temperature of the second liquid is approaching the second temperature threshold in response to the indicator receiving the second warning signal from the controller.

[0017] In another embodiment, the electronics cooling system further includes a fan that generates an airflow for cooling the second end of the tube and the first vapor in the tube.

[0018] In another aspect, the electronics cooling system further comprises a wicking material attached to the inner diameter surface adjacent to the second end of the tube, wherein the wicking material is different from the sorbent material.

[0019] In another embodiment, the wicking material is a layer extending from the second end to a portion of the tube adjacent to the electronic component.

[0020] In another embodiment, the sorbent material includes a plurality of recesses and the wicking material further includes a plurality of protrusions extending from the layer into the recesses of the sorbent material such that the wicking material draws the first liquid from the second end to the first end of the tube.

[0021] In another embodiment, the inner diameter surface defines a plurality of axial grooves extending between the first end and the second end for drawing the first fluid from the second end to the first end by capillary action. The axial grooves are circumferentially spaced from each other around the inner diameter surface.

[0022] In another embodiment, the sorbent material is spaced from the second end of the tube so that the condensed first liquid flows from the bore to the axial grooves. The sorbent material is further spaced from the first end of the tube so that the first liquid flows back from the axial grooves into the bore.

[0023] In another embodiment, the thermocouples include a first thermocouple attached to the electronic component and generating the first temperature signal. The thermocouples further include a second thermocouple attached to the heat pipe and generating the second temperature signal.

[0024] An exemplary method of operating an electronics cooling system is further described. The electronics cooling system includes an electronic component and a heat pipe attached to the electronic component. The heat pipe includes a tube having an inner diameter surface defining a bore, a sorbent material applied to the inner diameter surface, a first liquid contained within the bore, a second liquid adsorbed by the sorbent material, one or more thermocouples attached to the electronic component and / or the heat pipe, and a controller. The method includes the step of transferring heat from the electronic component to the first liquid at a first end of the closed-end tube.The first liquid evaporates to a first vapor in response to the first liquid receiving heat from the electronic component and the first liquid reaching the first boiling temperature. The first vapor flows from a first end of the closed-end tube to a second end of the closed-end tube where the first vapor dissipates heat through the tube. The first vapor condenses to the first liquid in response to the first vapor dissipating heat through the tube. The second liquid is desorbed from the sorbent in response to the second liquid and the sorbent reaching a predetermined desorption temperature that is below the second boiling temperature. The second liquid evaporates to a second vapor in response to the second liquid reaching the second boiling temperature.

[0025] At least a portion of the second liquid may be desorbed from the sorption material and introduced into the borehole before all of the first liquid evaporates to the first vapor.

[0026] The first liquid can be drawn by capillary action from the second end to the first end and through at least one axial groove formed in the inner diameter surface.

[0027] The thermocouple can generate a first temperature signal associated with a temperature of the first liquid. The controller compares the temperature of the first liquid to a first temperature threshold in response to the controller receiving the first temperature signal from the thermocouple. The controller generates a first warning signal in response to the controller determining that the temperature of the first liquid is above the first temperature threshold. An indicator displays a first warning indicating that the first liquid is approaching the first temperature threshold in response to the indicator receiving the first warning signal from the controller. The thermocouple generates a second temperature signal associated with a temperature of the second liquid.The controller compares the temperature of the second fluid to a second temperature threshold in response to the controller receiving the second temperature signal from the thermocouple. The controller generates a second warning signal in response to the controller determining that the temperature of the second fluid is above the second temperature threshold. The indicator displays a second warning indicating that the temperature of the second fluid is approaching the second temperature threshold in response to the indicator receiving the second warning signal from the controller. Fig. 1 is a perspective view of an example of an electronics cooling system including an electronic component and a heat pipe for cooling the electronic component. Fig. 2 is a cross-sectional view of an example of heat conduction of Fig.1, taken along line 2-2. Fig. 3 is a cross-sectional view of the heat conduction of Fig. 2 taken along line 3-3 showing the heat pipe having an inner diameter surface defining a plurality of axial grooves for drawing condensed first liquid from a second end of the heat pipe to a first end of the heat pipe. Fig. 4 is a diagram showing several fluids in the heat conduction of Fig. 1, which cools the electronic component of the circuit board. Fig. 5 is a cross-sectional view of another example of heat conduction from Fig. 1, showing heat conduction with wick material where the inner diameter surface is free of axial grooves. Fig. 6 is a cross-sectional view of the heat conduction of Fig. 5, taken along line 6-6, showing the sorbent material coated on the inner diameter surface. Fig. 7 is a cross-sectional view of the heat conduction of Fig. 5, taken along line 7-7, showing the wick material coated onto the inner diameter surface. Fig. Figure 8 is a cross-sectional view of yet another example of heat conduction from Fig. 1. Fig. 9 is a cross-sectional view of the heat conduction of Fig. 8, taken along line 9-9, showing the coated wicking material with multiple protrusions extending from an integral layer of the wicking material into corresponding recesses of the sorbent material. Fig. 10 is a cross-sectional view of the heat conduction of Fig. 8 along line 10-10, showing the integrated layer of wick material. Fig. 11 is a cross-sectional view of another example of heat conduction from Fig.1, which shows a layer of sorption material with a thickness less than the thickness of a layer of the wick material. Fig. 12 is a flowchart of an example of an example method for operating the circuit board of Fig. 2.

[0028] An exemplary electronics cooling system includes a heat pipe with a sorbent material to separate and recombine two or more liquids for cooling one or more electronic components. As described in the detailed examples below, the heat pipe includes two liquids with two different boiling temperatures, with one liquid stored in a bore of the heat pipe and another liquid stored in a sorbent material. These two liquids provide a dual active thermal range (or range of operating temperatures) within which the heat pipe removes heat from the electronic component. The range of operating temperatures can extend from the lowest freezing point of the two liquids to the highest boiling point of the two liquids.Within this range, the liquids receive heat from the electronic component, which in turn increases the temperature of the liquids. Those skilled in the art will know that heat can be transferred by removing heat from a heat source and adding that heat to another substance, such as a liquid, with or without the liquid reaching its boiling point. As just one example, the operating temperature of a heat pipe using only water ranges from 32 degrees Fahrenheit (the freezing point) to 212 degrees Fahrenheit (the boiling point at sea level). Evaporation is the vaporization at the water / air surface, and evaporation can occur at any temperature between the freezing point and the boiling point under a pressure of 1 atmosphere while heat conduction remains functional.It is envisioned that the heat pipe may contain more than two working fluids, and the sorbent material may be disposed in any position relative to the electronic component to adjust the heat pipe so that the percentage of each fluid used for cooling can be selected. Furthermore, the system described in detail below is a passive, open-loop system with a gravity-fed, closed-ended pipe, the first closed end of which is adjacent to the electronic component and the second closed end of which is adjacent to a cooling fan. However, it is conceivable that in other examples, the system may be an active, closed-loop system comprising a pipe forming a loop and a pump that pumps the condensate through the loop to return it to the electronic component.Furthermore, the examples of sorbent material described below are located near electronic components, and it is conceivable that the sorbent material is axially spaced from the electronic components and forms a layer of suitable thickness to achieve a corresponding cooling property. In still other examples, different sections of the sorbent material may initially store different liquids with associated boiling temperatures that differ from one another and be desorbed from the associated section of the sorbent material at associated temperatures to remove heat from the electronic components.

[0029] With reference to the Fig. 1 and Fig.2, an example of an electronics cooling system 100 includes an electronic component 104 that generates heat in response to an electrical current flowing through the electronic component 104. The electronic component may be a processor, driver circuitry, power circuitry, memory, or other electronic component that generates heat in response to receiving an electrical current.

[0030] As in the Fig. 2 and Fig. 3, the system 100 further includes a heat pipe 106 for cooling the electronic component 104. The heat pipe 106 includes a tube 108 having an inner diameter surface 110 defining a bore 112, the tube 108 having a first end 114 and a second end 116 ( Fig.2) along the bore 112. The inner diameter surface 110 defines one or more axial grooves 118 extending between the first end 114 and the second end 116 for drawing a first liquid 120 by capillary action from the second end 116 to the first end 114, as described in detail below. As shown in Fig. As best illustrated in Figure 3, the axial grooves 118 are circumferentially spaced at a uniform distance from one another around the inner diameter surface 110. It is contemplated that the grooves may be circumferentially spaced at a plurality of uniform or non-uniform distances around the inner diameter surface.

[0031] The heat pipe 106 further includes a sorption material 122 coated onto the inner diameter surface 110 of the tube 108 and spaced apart from the first end 114 and the second end 116 of the tube 108. In other words, the sorption material 122 is coated over the entire length of the inner diameter surface 110, except for a portion immediately adjacent the first end 114 and another portion immediately adjacent the second end 116. The sorption material 122 is configured to desorb at least a portion of a second liquid 124 into the bore 112 before all of the first liquid 120 evaporates into a first vapor 126. It is contemplated that the sorption material may be coated onto any portion of the inner diameter surface. The sorption material is selected from the group consisting of a zeolite, a silica gel, and a metal-organic framework.However, in other examples, the sorbent material may also contain other suitable materials for desorbing and adsorbing the second liquid.

[0032] The first liquid 120 is located within the bore 112 of the tube 108 and has a first boiling temperature. The first liquid 120 evaporates into a first vapor 126 in response to the tube 108 and the first liquid 120 receiving heat from the electronic component 104 and the first liquid 120 reaching the first boiling temperature. The first vapor 126 moves from the first end 114 to the second end 116, where the first vapor 126 conducts heat through the tube 108 and condenses into the first liquid 120.

[0033] The heat pipe 106 further includes a second liquid 124 adsorbed by the sorbent material 122 and having a second boiling temperature higher than the first boiling temperature of the first liquid 120. The second liquid 124 is desorbed from the sorbent material 122 and evaporates to a second vapor 128 in response to the second liquid 124 reaching the second boiling temperature. In this example, the first liquid 120 is water with a boiling temperature of 212 degrees Fahrenheit, and the second liquid 124 is ethylene glycol with a boiling temperature of 387 degrees Fahrenheit. However, it is conceivable that the first liquid and the second liquid are other suitable liquids with corresponding boiling temperatures. As in Fig.4, heat is supplied to the first liquid 120 during a first cooling stage 130, causing the temperature of the first liquid 120 to rise to the first boiling temperature BT1 and the first liquid 120 to evaporate. During a second cooling stage 132, the sorbent material 122 and the second liquid 124 receive heat from the electronic component 104 until the temperature of the sorbent material 122 and the second liquid 124 rises to a predetermined desorption temperature. The predetermined desorption temperature is lower than the second boiling temperature of the second liquid 124. More specifically, in this example, the predetermined desorption temperature is lower than both the first boiling temperature of the first liquid 120 and the second boiling temperature of the second liquid 124.Accordingly, the second liquid 124 is released from the sorbent material 122 before all of the first liquid 120 evaporates when the temperature of the sorbent material 122 and the second liquid 124 reaches the predetermined desorption temperature. The second liquid 124 evaporates in response to the temperature of the second liquid 124 reaching the second boiling temperature BT2.

[0034] In one example, the sorbent material 122 may release the second liquid 124 to combine with the first liquid 120, so that the boiling temperature of the resulting mixture may have a boiling temperature dependent on the concentration of the mixture. Examples of the boiling temperature and concentration of ethylene glycol in water may include the values ​​listed in the table below. Weight percent ethylene glycol Boiling point of the solution (deg F) Boiling point of the solution (deg C) 0 212 100 10 215 102 20 215 102 30 220 104 40 220 104 50 225 107 60 230 110 70 240 116 80 255 124 90 285 140 100 387 197

[0035] The concentration or weight percentage of the solution can be controlled by at least one of the following: using predetermined liquids with associated boiling points, positioning sorbent materials containing these liquids at predetermined positions relative to the electronic components, and forming the sorbent material into layers of predetermined thickness.

[0036] With further reference to Fig.2, the system 100 further includes one or more thermocouples 134 attached to the electronic component 104 and / or the heat pipe 106, wherein the thermocouple 134 generates a first temperature signal associated with a temperature of the first liquid and generates a second temperature signal associated with the temperature of the second liquid 124. More specifically, in this example, the at least one thermocouple 134 includes a first thermocouple 136 attached to the electronic component 104 and generates the first temperature signal. The at least one thermocouple 134 further includes a second thermocouple 138 attached to the heat pipe 106 and generates the second temperature signal.In other examples, the system includes a single thermocouple disposed within the bore of the tube or elsewhere and attached to any portion of the heat pipe or electronic component.

[0037] The system 100 further includes a controller 140 electrically connected to the thermocouples 134. The controller 140 compares the temperature of the first liquid 120 to a first temperature threshold in response to the controller 140 receiving the first temperature signal from the thermocouple 134. The controller 140 generates a first warning signal in response to the controller 140 determining that the temperature of the first liquid 120 is above the first temperature threshold. In this example, the first temperature threshold is the first boiling temperature of the first liquid, such as 212 degrees Fahrenheit, the boiling temperature of water. The controller 148 compares the temperature of the second liquid 124 to a second temperature threshold in response to the controller 140 receiving the second temperature signal from the thermocouple 134.The controller 140 generates a second warning signal in response to the controller 140 determining that the temperature of the second liquid 124 is above the second temperature threshold. Following the previous example, the second temperature threshold is the second boiling temperature of the second liquid 124, for example, 387 degrees Fahrenheit, the boiling temperature of ethylene glycol.

[0038] The controller 140 is further electrically coupled to a display device 142 for displaying a first warning indicating that the first liquid 120 is approaching the first temperature threshold in response to the display device 142 receiving the first warning signal from the controller 140. The display device 142 further displays a second warning indicating that the temperature of the second liquid 124 is approaching the second temperature threshold in response to the display device 142 receiving the second warning signal from the controller 140.

[0039] The system 100 further includes a fan 144 that directs an air flow over the second end 116 of the tube 108 and the fins 117 ( Fig. 2) extending from the tube 108 to dissipate heat therefrom.

[0040] With reference to the Fig.5-7 is another example of a heat pipe 206 of the heat pipe 106 of Fig. 2 and includes the same components, which are identified by the same reference numerals increased by 100. While the heat pipe 106 of Fig.2-3 has axial grooves 118 for returning the first liquid 120 from the second end 116 to the first end 114, the heat pipe 206 includes an inner diameter surface 210 that is free of grooves. The heat pipe 206 includes a wicking material 250 coated onto the inner diameter surface 210 that is different from the sorption material 222. The wick material 250 extends from a portion of the inner diameter surface 210 near the second end 216 to a portion of the inner diameter surface 210 near the electronic component 204. The wick material 250 absorbs the first liquid 220 after the first vapor 226 has passed from the first end 214 to the second end 216, where the first vapor 226 conducts heat through the tube 208 and condenses into the first liquid 220, so that the wick material 250 draws the first liquid 220 from the second end 216 to the first end 214. While the heat pipe 106 of Fig. 2 includes a tube 108 with sorption material 122 extending from a portion near the first end 114 to another portion near the second end 116, the heat pipe 206 includes a sorption material 222 coated only on a portion immediately adjacent the first end 214. All of the sorption material 222 and a portion of the electronic component 204 are arranged along the tube 208 in coextensive relationship with each other, with another portion of the electronic component 204 extending axially beyond the sorption material 222.

[0041] With reference to the Fig. 8-10 is another example of a heat pipe 306 of the heat pipe 206 from the Fig. 5-7 and includes the same components, which are identified by the same reference numerals increased by 100. While the entire sorption material 222 and only a part of the electronic component 204 of the Fig.4-6 are coextensive along the tube 208, the entire electronic component 304 and a portion of the sorption material 322 are arranged coextensive with each other along the tube 308, with another portion of the sorption material 322 extending axially beyond the electronic component 304. In comparison to the heat pipe 206 of the Fig. 5-7, the heat pipe 306 has an arrangement of the sorption material 322 relative to the electronic component 304 that transfers heat to a larger portion of the second liquid 324 at a faster rate than the heat pipe 206 of the Fig.5-7. Furthermore, the sorbent material 322 includes a plurality of recesses 352, and the wicking material 350 includes a layer 354 extending from the sorbent material 322 to the second end 316, with a plurality of protrusions 358 extending from the layer 354 into the recesses 352 of the sorbent material 322 so that the first liquid 320 can be drawn from the second end 316 to the first end 314 of the tube 308.

[0042] With reference to Fig. 11 another example of a heat pipe 406 of the heat pipe 306 from the Fig. 8-10 and includes the same components, which are identified by the same reference numbers increased by 100. However, while the entire electronic component 304 and only a part of the sorption material 322 of Fig.8-10 are coextensive, the entire electronic component 404 and the entire sorption material 422 are coextensive. While the sorption material 322 and the wick material 350 of the Fig. 8-10 each form layers of equal thickness, the sorption material 422 also forms a layer 458 whose thickness is less than the thickness of the layer 454 of the wick material 450.

[0043] With reference to Fig. 12, an exemplary method 500 for operating the system 100 of Fig. 2. The method 500 begins at block 502, where the electronic component 104 transfers heat through the tube 108 to the first fluid 120. The electronic component or another part of the system may generate heat when the electrical component receives an electrical current.

[0044] In block 504, the first liquid 120 evaporates into the first vapor 126 in response to the first liquid 120 receiving heat from the electronic component 104 and the first liquid 120 reaching the first boiling temperature.

[0045] In block 506, the first thermocouple 136 generates a first temperature signal associated with the temperature of the first liquid.

[0046] In block 508, the controller 140 compares the temperature of the first liquid 120 to a first temperature threshold in response to the controller receiving the first temperature signal from the first thermocouple 136. In this example, the first temperature threshold is the first boiling temperature. However, it is conceivable that the first temperature threshold is above or below the first boiling temperature. For example, to provide an additional warning about the drying out of the first liquid 120, the first temperature threshold may be a temperature below the first boiling temperature of the first liquid 120. If the temperature of the first liquid 120 is below the first temperature threshold, the method repeats block 508. If the temperature of the first liquid 120 is above the first temperature threshold, the method continues to block 510.

[0047] In block 510, the controller 140 generates a first warning signal in response to the controller 140 determining that the temperature of the first liquid 120 is above the first temperature threshold.

[0048] In block 512, a display device 142 displays a first warning indicating that the first liquid 120 is approaching the first temperature threshold in response to the display device receiving the first warning signal from the control unit 140.

[0049] In block 514, the first steam 126 flows to the second end 116 and the fins 117, where the first steam 126 dissipates heat through the tube 108 and the fins 117.

[0050] In block 516, the first vapor 126 condenses into the first liquid 120 as the first vapor 126 releases heat through the second end 116 of the tube 108.

[0051] In block 518, the first liquid 120 is drawn by capillary action from the second end 116 to the first end 114 through the axial grooves 118 formed in the inner diameter surface 110.

[0052] In block 520, the second liquid 124 is desorbed from the sorbent 122 and evaporates to the second vapor 128 in response to the second liquid 124 reaching the second boiling temperature. In this example, at least a portion of the second liquid 124 is desorbed from the sorbent material 122 into the bore 112 before all of the first liquid 120 evaporates to the first vapor 126. This can be achieved by providing liquids with predetermined boiling points, sorbents arranged in various configurations relative to the electronic components, and sorbent layers of appropriate thickness.

[0053] In block 522, the second thermocouple 138 generates a second temperature signal associated with the temperature of the second liquid 124.

[0054] In block 524, the controller 140 compares the temperature of the second liquid 124 to a second temperature threshold in response to the controller 140 receiving the second temperature signal from the second thermocouple 138. In this example, the second temperature threshold is the second boiling temperature. However, it is conceivable that the second temperature threshold is above or below the second boiling temperature. For example, to provide additional warning of the second liquid 124 drying out, the second temperature threshold may be lower than the second boiling temperature of the second liquid 124. If the temperature of the second liquid 124 is below the second temperature threshold, the method repeats block 524. If the temperature of the second liquid 124 is above the second temperature threshold, the method continues to block 526.

[0055] In block 526, the controller 140 generates a second warning signal in response to the controller 140 determining that the temperature of the second liquid 124 is above the second temperature threshold.

[0056] In block 528, the display device 142 displays a second warning indicating that the temperature of the second liquid is approaching the second temperature threshold in response to the display device receiving the second warning signal from the controller 140. In this example, the second temperature threshold is the second boiling temperature. However, it is contemplated that the second temperature threshold may be above or below the second boiling temperature. For example, to provide an additional warning of the drying out of the second liquid 124, the second temperature threshold may be a temperature below the second boiling temperature.

Claims

[1] Heat pipe (106) for an electronics cooling system (100) with an electronic component (104), the heat pipe (106) comprising: a tube (108) having an inner diameter surface (110) defining a bore (112), the tube (108) having a first end (114) and a second end (116) along the bore (112); a sorbent material (122) coated on the inner diameter surface (110) of the tube (108); a first liquid (120) contained in the bore (112) of the tube (108) and having a first boiling temperature; and a second liquid (124) adsorbed by the sorbent material (122) and having a second boiling temperature higher than the first boiling temperature of the first liquid (120); wherein the first liquid (120) evaporates into a first vapor (126) in response to the tube (108) receiving heat from the electronic component (104) and the first liquid (120) reaching the first boiling temperature, and the first vapor (126) moves to the second end (116) where the first vapor (126) dissipates heat through the tube (108) and condenses into the first liquid (120); wherein the second liquid (124) is desorbed from the sorbent material (122) in response to the second liquid (124) and the sorbent material (122) reaching a predetermined desorption temperature which is lower than the second boiling temperature, and the second liquid (124) evaporates to a second vapor (128) when the second liquid (124) reaches the second boiling temperature. [2] The heat pipe (106) of claim 1, wherein the sorption material (122) is configured to desorb at least a portion of the second liquid (124) into the bore (112) before all of the first liquid (120) evaporates to the first vapor (126). [3] The heat pipe (106) of claim 2, wherein the inner diameter surface (110) defines at least one axial groove (118) extending between the first end (114) and the second end (116) for drawing the first liquid (120) from the second end (116) to the first end (114) by capillary action. [4] The heat pipe (106) of claim 3, wherein the at least one axial groove (118) comprises a plurality of axial grooves (118) circumferentially spaced from each other on the inner diameter surface (110). [5] The heat pipe (106) of claim 4, wherein the sorbent material (122) is coated onto the inner diameter surface (110) and spaced from the first and second ends (114, 116) of the tube (108). [6] The heat pipe (106) of claim 5, wherein the first liquid (120) is water. [7] The heat pipe (106) of claim 6, wherein the second liquid (124) is ethylene glycol. [8] Electronics cooling system (100), comprising: an electronic component (104) that generates heat; a heat pipe (106) for cooling the electronic component (104), the heat pipe (106) comprising: a tube (108) having an inner diameter surface (110) defining a bore (112), the tube (108) having a first end (114) and a second end (116) along the bore (112); a sorbent material (122) coated on the inner diameter surface (110) of the tube (108) near the first end (114); a first liquid (120) contained in the bore (112) of the tube (108) and having a first boiling temperature; and a second liquid (124) adsorbed by the sorbent material (122) and having a second boiling temperature higher than the first boiling temperature of the first liquid (120); wherein the first liquid (120) evaporates into a first vapor (126) in response to the tube (108) receiving heat from the electronic component (104) and the first liquid (120) reaching the first boiling temperature, and the first vapor (126) moves to the second end (116) where the first vapor (126) dissipates heat through the tube (108) and condenses into the first liquid (120); and wherein the second liquid (124) is desorbed from the sorbent material (122) in response to the second liquid (124) and the sorbent material (122) reaching a predetermined desorption temperature which is lower than the second boiling temperature, and the second liquid (124) evaporates to a second vapor (128) when the second liquid (124) reaches the second boiling temperature; at least one thermocouple (134) attached to the electronic component (104) and / or the heat pipe (106), wherein the at least one thermocouple (134) generates a first temperature signal associated with the temperature of the first liquid (120); a controller (140) electrically connected to the at least one thermocouple (134), wherein the controller (140) compares the temperature of the first liquid (120) to a first temperature threshold in response to the controller (140) receiving the first temperature signal from the at least one thermocouple (134), and wherein the controller (140) generates a first warning signal when the controller (140) determines that the temperature of the first liquid (120) is above the first temperature threshold; wherein the controller (140) is electrically coupled to a display device (142) to display a first warning indicating that the first liquid (120) is approaching the first temperature threshold when the display device (142) receives the first warning signal from the controller (140). [9] The electronics cooling system (100) of claim 8, wherein the at least one thermocouple (134) generates a second temperature signal associated with the temperature of the second liquid (124); wherein the controller (140) compares the temperature of the second liquid (124) to a second temperature threshold in response to the controller (140) receiving the second temperature signal from the at least one thermocouple (134); and wherein the indicator device (142) displays a second warning indicating that the temperature of the second liquid (124) is approaching the second temperature threshold in response to the indicator device (142) receiving the second warning signal from the controller (140). [10] The electronics cooling system (100) of claim 9, further comprising a fan (144) that generates an airflow for cooling the second end (116) of the tube (108) and the vapor within the closed-end tube (108).

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