WO2016068834A1

WO2016068834A1 - An artificial peristalsis device

Info

Publication number: WO2016068834A1
Application number: PCT/US2014/062347
Authority: WO
Inventors: Titus D. Stauffer; Mary Dove STAUFFER
Original assignee: Hewlett Packard Enterprise Development LP
Current assignee: Hewlett Packard Enterprise Development LP
Priority date: 2014-10-27
Filing date: 2014-10-27
Publication date: 2016-05-06
Anticipated expiration: 2017-04-27

Abstract

The technologies discussed herein are related to an artificial peristalsis device, and a method to circulate a viscous fluid using an artificial peristalsis device. In one example, the artificial peristalsis device can include an artificial muscle. The artificial peristalsis device can include a flexible sheath covering the artificial muscle. The artificial peristalsis device can include an inner hose used to circulate a viscous fluid. The inner hose can have a one-way flow valve to help control the flow direction of the viscous fluid through the inner hose. The artificial peristalsis device can also include a cold water hose that is spiral wrapped around the inner hose. The artificial muscle can be co-wrapped with the cold water hose.

Description

AN ARTIFICIAL PERISTALSIS DEVICE

BACKGROUND

[0001] Immersion cooling is a technique used to provide temperature regulation for heat producing components of a computer system. The electronic components to be cooled are immersed in a viscous fluid or a semi-fluid paste with low electrical conductivity. A coolant fluid that is thermally conductive and has low- electrical conductivity is chosen to immerse the computer components, in order to avoid potential electrical short circuits in the computer system. The coolant fluid is pre-chilled and absorbs heat throughout the computer system, as the coolant fluid is typically circulated using electromechanical pumps. The electromechanical pumps are heat sources themselves, and often have harsh metallic edges or bearings that wear with friction and time. Electromechanical pumps may also shed metal particles into the cooling fluid, and require troublesome maintenance and lubrication. If the cooling fluid is viscous, then electromechanical pumps, like screw propellers, for example, may not sufficiently circulate the cooling fluid.

BRIEF DESCRIPTION OF THE DRAWINGS

[0002] Certain examples are described in the following detailed description and in reference to the drawings, in which:

[0003] FIG. 1 A is a diagram of an artificial peristalsis device with a segment that is in a relaxed state;

[0004] FIG. 1 B is a diagram of an artificial peristalsis device with a segment that is in a partially-constricted state;

[0005] FIG. 1 C is a diagram of an artificial peristalsis device with a segment that is in a fully-constricted state;

[0006] FIG. 2 is a process flow diagram of a method to circulate a viscous fluid through use of an artificial peristalsis device;

[0007] FIG. 3 is a process flow diagram of a method to circulate a viscous fluid through use of a peristalsis device;

[0008] FIG. 4 is a schematic diagram of a computer system with a case and printed circuit board configured for immersion cooling that uses artificial peristalsis devices to circulate a viscous coolant fluid; [0009] FIG. 5 is a process flow diagram of a method to regulate the

temperature of components of a computer system with immersion cooling by using an artificial peristalsis device;

[0010] FIG. 6 is a block diagram of a computer system with a case and printed circuit board configured for immersion cooling using an artificial peristalsis device and a brush device to circulate a viscous coolant fluid;

[0011] FIGS. 7A and 7B are diagrams of a system with a valve actuated by an artificial muscle;

[0012] FIG. 8 is a diagram showing a coolant fluid flow through a case;

[0013] FIG. 9 is a diagram of a system with a valve actuated by an artificial muscle attached to a pulley; and

[0014] FIG. 10 is a diagram of a bellows pump actuated by a linear actuator.

DETAILED DESCRIPTION OF SPECIFIC EXAMPLES

[0015] The techniques and technologies described herein use "artificial muscles" that relax when cooled, and constrict when heated. The artificial muscles can act as an artificial peristalsis pump used to circulate viscous fluids, much like the gastrointestinal system in humans. Peristalsis is a means by which an artificial wave propagates down a tube in an anterograde fashion. The artificial muscle or peristalsis pump can be composed of flexible walls and highly twisted monofilament string, and can be incorporated into an artificial peristalsis device described herein. Because the artificial peristalsis device contracts when heated and relaxes when cooled, and further because the artificial peristalsis device does not introduce any heat energy into a being-cooled environment, it may be useful in an immersion cooling system. The techniques herein describe an energy efficient means of circulating a viscous fluid, and in some examples of circulating a viscous coolant fluid or semi-fluid paste in a computing environment that requires cooling.

[0016] Paraffin wax, for example, tricosane, is an example of a phase-change cooling material that is viscous. As the paraffin wax changes from the solid phase to the liquid phase, for example, at about 40 to about 70 degrees C, it absorbs heat during the phase change. However, wax, whether solid or liquid, is not highly thermally conductive. Various ingredients, such as hexagonal boron nitride, have been used as additives to increase the thermal conductivity of wax, without increasing electrical conductivity. Other additives with similar properties can be utilized, such as metal oxides, small spheres of metal with anodized surfaces, or metal spheres coated in thermally conductive epoxy that is not electrically conductive so to eliminate the hazard of shorting electronics components.

[0017] A coolant fluid made up only of paraffin wax, when cold, may be too stiff and resistant to flow to allow it to be pumped and circulated in a controlled manner, and to be directed to where it is needed in a cooling system. Accordingly, a useful mixture of properties for the coolant fluid would include being non-corrosive, non-toxic, thermally conductive, and electrically non-conductive. In examples described herein, the coolant fluid has the ability to change phases and absorb significant amounts of heat during the phase change process.

[0018] The coolant fluid can also include, for example, mildly to moderately combustible additives in small amounts like kerosene or petroleum oils. Such additives can help increase the fluidity and reduce resistance to flow for the coolant fluid. The coolant fluid may also include, for example, methanol, ethanol, or propanol, provided safe and effective methods are used to rapidly return the highly volatile gaseous phases of such material to the liquid phase, settling back into the coolant fluid.

[0019] Some examples of the artificial peristalsis techniques described herein include a method and artificial peristalsis device to circulate a fluid. The fluid can be a viscous fluid, or a semi-viscous fluid, or can be a fluid that has low viscosity. This circulation can begin by taking the viscous fluid into the artificial peristalsis device. Cold water can be pumped through a cold water hose of the artificial peristalsis device, the cold water is configured to cool the viscous fluid that has absorbed ambient heat. As the viscous fluid is cooled, the artificial peristalsis device is also cooled. The artificial peristalsis device also includes an artificial muscle that relaxes when cooled and constricts when heated. Ambient heat may again be absorbed by the viscous fluid, thereby heating and constricting the artificial peristalsis device. The viscous fluid can be expelled from the artificial peristalsis device because of the changes in temperature and the relaxing and constricting of the artificial peristalsis device.

[0020] FIG. 1 A is a diagram of an artificial peristalsis device 1 00 with a segment 102 that is in a relaxed state. FIG. 1 A shows a segment 102 of the artificial peristalsis device 100 in a relaxing phase, with a fluid 104 being circulated through the segment 102. On each end of the segment 102, there is a one-way valve 106 to help control the flow of the fluid through the artificial peristalsis device 100. An artificial muscle 108 can be wrapped around a flexible tubular 1 10 that contains the fluid 104 being pumped. The artificial muscle 108 can be made, for example, of flexible walls and twisted monofilament string, among other. A cold water hose 1 12 can be co-wrapped with the artificial muscle 108 around the outside of the flexible tubular 1 10. Chilled water can be pumped through the cold water hose 1 12.

[0021] When cold water is introduced into a segment 102 of the artificial peristalsis device 100 at entrance 1 14 of the cold water hose 1 12, the artificial muscle 1 08 cools and relaxes. As the artificial muscle 108 relaxes, it allows the flexible tubular 1 10 to open to a wider diameter. Ambient pressure of the fluid 104 can force the fluid 104 into the relaxed chamber of the flexible tubular 1 1 0.

[0022] The flow of the cold water can be stopped to allow heat to increase in the cold water hose 1 1 2. The cold water can be allowed to heat up and eventually pumped out of exit 1 16 of cold water hose 1 12. The water temperature gradually increases as heat is absorbed by the fluid 104 from the surroundings and transferred to the colder water. As the temperature increases, the artificial muscle 108 constricts, forcing the fluid 104 through the one-way flow valves 1 06 into, for example, a subsequent segment of the artificial peristalsis device 100, or into another chamber.

[0023] There are two primary reasons why the flexible tubular 1 10 opens up, taking in the fluid 1 04 on the left side of FIG. 1 . One reason is that the artificial muscle 1 08, co-wrapped with the cold water hose 1 12, cools and relaxes. Another reason is that the water pressure inside the cold water hose 1 12 inflates the flexible tubular 1 10, as the fluid 1 04 around it develops a lower pressure region. The vacuum causes the cold water hose 1 12 to seek its maximum volume, creating an internal, hose-wrapped cavity.

[0024] The cold water hose 1 12 can be joined to the flexible tubular 1 10, for example, by bonding or periodically tacking. The artificial muscle 108 can also be securely connected where it enters and exits the co-wrapping of the cold water hose 1 12, so to prevent sliding back and forth from one segment 1 02 of the artificial peristalsis device 100 to the next. Without such bonding the artificial muscle 108 risks becoming tightly bunched and stuck around a segment 102 due to friction and other forces.

[0025] In some examples, the artificial muscle 108 can be immersed in the fluid 104. In some examples, the artificial muscle 108 can be heated and cooled by both the water in the cold water hose 1 12 and the surrounding fluid 104. In some examples, the innermost side of the flexible tubular 1 10 can be thermally insulated so the artificial muscle 108 exchanges more heat with the water and less with the ambient fluid 104.

[0026] FIG. 1 B is a diagram of an artificial peristalsis device 1 00 with a segment 102 that is in a partially-constricted state. Like numbered items are as described with respect to FIG. 1 A. FIG. 1 B shows a segment 102 of the artificial peristalsis device 100 in a warm phase, with a fluid 104 being circulated through the segment 102.

[0027] After the water in the cold water hose 1 12 has had time to absorb heat from the artificial muscle 108, allowing the segment 102 to contract, the water can slowly be pumped out of the artificial peristalsis device 100 at exit 1 16. The water pressure within the cold water hose 1 12 is reduced, and the cold water hose 1 1 2 may collapse. The collapse of the cold water hose 1 12 acts to further force the fluid 104 to move within the flexible tubular 1 10. The fluid 1 04 also circulates due to heating of the artificial muscle 108, which causes the artificial muscle 108 to contract and pump more fluid 104 toward the next one-way valve 106. The lower pressure region inside the flexible tubular 1 10 can change to a neutral and then a positive pressure. This change in pressure helps force more of the fluid 1 04 along the segment 102 of the artificial peristalsis device 100.

[0028] FIG. 1 C is a diagram of an artificial peristalsis device 100 with a segment 102 that is in a fully-constricted state. Like numbered items can be described with respect to FIG. 1 A. FIG. 1 C shows a segment 1 02 of the artificial peristalsis device 100 in a hot phase, with a fluid 104 being circulated through the segment 102.

[0029] In the depicted fully-constricted state, the water in the cold water hose 1 12 has remained static for a longer duration, heating up to a hotter temperature, for example, anywhere from about 30 to about 80 degrees C. Pumping the hot water completely out from the cold water hose 1 12 causes the cold water hose 1 12 to collapse even further, increasing the pressure around the flexible tubular 1 10. The artificial muscle 108 absorbs the maximum heat for the cycle and constricts more tightly than in the phases depicted by FIGS. 1 A and 1 B. The pumped fluid 104 is expelled through the segment 102 at the end of the artificial peristalsis device 100, and the cycle depicted by FIGS. 1 A, 1 B, and 1 C can be repeated.

[0030] The stages of the artificial peristalsis device 100 function described herein combines the effects of cooling the fluid 104 without the chilled water mixing into the fluid 104, and without producing excess heat, while pumping the fluid 1 04 in a controlled way. In some examples, the hot water pumped out of the artificial peristalsis device 102 can be cooled outside of the computer system 100 before being reintroduced as chilled water. In some examples, the hot water pumped out of the artificial peristalsis device 100 can be cooled inside the computer system 100, and recirculated as chilled water. In some examples, the cold water hose 1 12 can be refilled with cold water at 1 14, and can be refilled with cold water continuously if the heat load in computer system 100 is significantly high. In some examples, a separate injection pump at one end of a segment 1 02 of the cold water hose 1 12, and a suction pump at another end of the segment 102 can be included. Such an example can allow the flow of water at the hottest point within the artificial peristalsis device 1 00 to be more efficiently controlled. The collapse of cold water hose 1 12 can be controlled, and the heated fluid 104 placed in almost direct contact with the artificial muscle 108, which can attain maximum constriction. After the collapsed condition persists, for example, for a specified time period where temperature can be monitored, cold water can be pumped back inside the cold water hose 1 12.

[0031] In some examples, the entry point for the fluid 104 in the artificial peristalsis device 100 consists of a rigid-framed opening to the flexible tubular 1 10. Such an example ensures that ambient viscous fluid is free to enter the flexible tubular 1 10 without the opening collapsing or folding, and thereby obstructing entry of the fluid 104 into the artificial peristalsis device 1 00. In some examples, both the entry point of the fluid 104 and the exit point of the artificial peristalsis device 1 00 can be firmly mechanically secured for both the flexible tubular 1 10 and for the artificial muscle. The artificial peristalsis device 100 described herein reduces wasteful direct mixing of incoming chilled water and outgoing heated water, and does not introduce any heat energy itself to a system that is being cooled. [0032] The diagrams of FIGS. 1 A, 1 B, and 1 C are not intended to indicate that the artificial peristalsis device 100 is to include all of the components shown in FIGS. 1 A, 1 B, and 1 C. Any number of additional components may be included within the artificial peristalsis device 100, depending on the details of the device and specific implementation of circulating a fluid by artificial peristalsis. For example, the items discussed are not limited to the functionalities mentioned, but the functions could be done in different places and by different components. For example, the segment 102 can be one segment of a multiple segment device. In such an example, a first segment can take fluid from a surrounding environment, intermediate segments can pass fluid from a previous segment to a following segment, and a final segment can eject the fluid into the surrounding environment.

[0033] FIG. 2 is a process flow diagram of a method 200 to circulate a viscous fluid through use of an artificial peristalsis device. In some examples, the peristalsis device can be described with respect to artificial peristalsis device 100 from FIG. 1 . The method 200 begins at block 202.

[0034] At block 202, the method 200 begins by taking a viscous fluid into the peristalsis device. The peristalsis device can be immersed in the viscous fluid. The viscous fluid can be a viscous semi-fluid, a paste, or a liquid. In some examples, the viscosity can range from about 2000 centipoise, for example, the viscosity of honey or molasses, to about 200,000 centipoise, for example, the viscosity of peanut butter.

[0035] At block 204, cold water is pumped into a cold water hose of the peristalsis device. The cold water hose can be wrapped around the outside of an inner hose or chamber of the peristalsis device. The cold water hose can cool the viscous fluid within the peristalsis device. This may, for example, be able to remove excess heat from the device.

[0036] At block 206, the viscous fluid is cooled by exchanging heat with the water in the cold water hose. This cooling can also cool the peristalsis device. In this example, as the artificial muscles within the peristalsis device are cooled they relax. The relaxing of the artificial muscles can widen the entrance of the peristalsis device, and allow the intake of additional viscous fluid.

[0037] At block 208, ambient heat is absorbed by the viscous fluid. The absorbed heat also heats the peristalsis device. The heating of the peristalsis device causes the artificial muscle to constrict. This constricting forces the viscous fluid through the peristalsis device.

[0038] At block 210, the method 200 ends by expelling the viscous fluid from the peristalsis device. When an amount of heat is absorbed that causes the artificial muscle to fully constrict, the viscous fluid will be pushed to the end of the peristalsis device. The viscous fluid is then expelled from the peristalsis device as the heating and pumping cycle described continues to circulate the viscous fluid through the peristalsis device.

[0039] The method 200 of FIG. 2 is not intended to indicate that method 200 is to include all of the steps shown in FIG. 2. Further, any number of additional steps may be included within the method 200, including, for example, steps from the method described with respect to the process flow diagram in FIG. 3.

[0040] FIG. 3 is a process flow diagram of a method 300 to circulate a viscous fluid through use of a peristalsis device. In some examples, the peristalsis device can be described with respect to artificial peristalsis device 100 from FIG. 1 . The method 300 begins at block 302 when a viscous fluid is taken into the peristalsis device. The peristalsis device is encased in a flexible sheath, and the peristalsis device is spiral-wrapped by a cold water hose.

[0041] The method 300 continues at block 304 where cold water is pumped through the cold water hose around the peristalsis device. At block 306, the cold water absorbs heat from the viscous fluid, allowing the viscous fluid to cool, and the peristalsis device to cool and relax. As the peristalsis device relaxes, the device is opened to a widest point and is ready to intake additional viscous fluid. At block 308, additional viscous fluid is taken in from outside the peristalsis device. The peristalsis device can be immersed in a viscous fluid used for cooling. The immersed peristalsis device can circulate the viscous fluid using method 300 throughout a contained area.

[0042] At block 310, the peristalsis device heats up and constrict as the viscous fluid absorbs ambient heat. As the peristalsis device constricts, the viscous fluid is circulated through the peristalsis device in an anterograde manner. Flowing in an anterograde manner means flow is directed forward in one direction over time. At block 312, heated water is slowly pumped out from the cold water hose that has absorbed heat from the viscous fluid circulated by the peristalsis device. [0043] At block 314, the cold water hose collapses. The collapse of the cold water hose can be due to water being pumped out from the cold water hose without being refilled. At block 316, the peristalsis device is further constricted due to both the constricting of the heated artificial muscle of the peristalsis device, as well as the collapsing of the cold water hose. The method 300 ends at block 318 where the viscous fluid is expelled from the peristalsis device. At this point, the method 300 is ready to repeat and continue circulating a viscous fluid through the peristalsis device.

[0044] The method 300 of FIG. 3 is not intended to indicate that method 300 is to include all of the steps shown in FIG. 3. Further, any number of additional steps may be included within the method 300, including, for example, steps from the method described with respect to the process flow diagram in FIG. 5.

[0045] FIG. 4 is a schematic diagram of a computer system 400 with a case 402 and printed circuit board (PCB) 404 configured for immersion cooling that uses artificial peristalsis devices 406 to circulate a viscous coolant fluid 408. The case 402 can be a housing for a computer system that is typically used in the art, for example, a server box. The PCB 404 can also be a printed circuit assembly (PCA), with multiple electrical components that generate heat and require cooling. In some examples, the artificial peristalsis devices 406 can be described with respect to artificial peristalsis device 100 of FIG. 1 . The block diagram of FIG. 4 is intended as a top-down view of the case 402 being cooled.

[0046] An actively flowing cooling system is to circulate the viscous coolant fluid 408 to where it is needed in the case 402. Artificial peristalsis devices 406 are positioned throughout the case 402 and anchored to the PCB 404. Different artificial peristalsis devices 406 are to move ambient viscous coolant fluid 408 through the area of the case 402 over the PCB 404. In some examples, a larger artificial peristalsis device 407 can handle heated viscous coolant fluid 408 on a "downwind" or more heated side of a major heat source 410. As the viscous coolant fluid 408 cools and is redirected, the viscous coolant fluid 408 can be deposited away from the major heat source 410 and near smaller heat sources 412 to be cooled.

[0047] Additional artificial peristalsis devices 406 can be configured

throughout the case 402 and over the PCB 404. These artificial peristalsis devices 406 can be placed, for example, near the smaller heat sources 412. The artificial peristalsis devices 406 can pump and cool down the viscous coolant fluid 408 after the viscous coolant fluid 408 has absorbed heat by cooling the smaller heat sources 412. The viscous coolant fluid 408 can also be directed toward diffuse, small heat sources 414 to provide cooling and circulation of the viscous coolant fluid 408 throughout the case 402.

[0048] In the example described in FIG. 4, a current 416, depicted by arrows, may be created for circulating the viscous coolant fluid 408 throughout the case 402 of the computer system 400. The current 41 6 is the flow of the viscous coolant fluid 408 established by the configuration of artificial peristalsis devices 406 around various components of the PCB 404. The current 41 6 created by the artificial peristalsis devices 406 forces the ambient viscous coolant fluid 408 to and from different heat sources inside the case 402. Some sources in the computer system 400 that generate significant heat and require continuous cooling can include, for example, a processor or a large transistor. The artificial peristalsis devices 406 themselves do not introduce heat into the computer system 400. Not only do the artificial peristalsis devices 406 circulate viscous fluid without adding heat to the computer system 400, the artificial peristalsis devices 406 remove heat from the computer system 400, as well. The efficient cooling techniques, heat transfer, and artificial muscles within the artificial peristalsis devices 406, can result in an effective current 416 of the viscous coolant fluid 408 that cools the PCB 404.

[0049] In some examples, mechanical fences and shields can be used to protect delicate components of the PCB 404 from the constricting and relaxing motions of the artificial peristalsis devices 406. In some examples, surfaces with small and delicate surface mounted components are coated with a protective epoxy, or the like, that is thermally conductive but not electrically conductive. In some examples, the viscous coolant fluid 408 can be completely contained within the case 402, and chilled water can be pumped through the cold water hoses connected to the artificial peristalsis devices 406. In some examples, the viscous coolant fluid 408 is chilled outside of the case 402 and then pumped into the box to further cool the components within, while hot fluid 408 can actively be pumped out of the case 402 to be re-chilled. In some examples, chilled water can be injected in cold water hoses to cool the viscous coolant fluid 408 in the artificial peristalsis devices 406, and the viscous coolant fluid 408 can additionally be chilled outside of the case 402 and returned to the case 402. [0050] A set of pistons 418 that are fluidically coupled to the viscous fluid 408 in the case 402 can also be included. As water is being pumped into and out of the hoses in the computer system 400, the volume of fluid within the computer system 400 can change. The pistons 41 8 allow for slight expansion and contraction of the fluid in the case 402 so that the PCB 404 and other components are not damaged. Additionally, due to thermal expansion and contraction of the viscous coolant fluid 408, there can also be increases and decreases in total volume within the case 402. The pistons 418 can help to prevent the buildup of pressure on certain components of the computer system 400, and to keep the case 402 balanced. Other

arrangements, such as springs coupling one wall of the case 402 to the rest of the case may provide the same benefits, for example, by allowing the entire case to function as a piston, expanding and contracting with the fluid. Flexible walls at the periphery of the case 402 may be included so the top of the case 402 can be displaced up or down in response to changes in volume. The springs can ensure the top of the case 402 does not get out of alignment with the case 402.

[0051] The schematic diagram of FIG. 4 is not intended to indicate that the computer system 400 is to include all of the components shown in FIG. 4. Any number of additional components may be included within the computer system 400, depending on the details of the devices and specific implementation of immersion cooling described herein. For example, a heat pump, such as a Peltier device that utilizes current to create a temperature drop across thermoelectric plates of the device, can be included and controlled to run by anticipating times of peak workloads and heat generation. Additionally, in some examples, a heat sink or multiple heat sinks cooled by air or otherwise can be placed in proximity to a hotter component of the PCB 404, such as a processor, to assist with dissipating ambient heat. Also, additional heat sinks can be placed on top of or within the case 402 to assist in cooling. Further, the items discussed are not limited to the functionalities mentioned, but the functions could be done in different places, or by different components.

[0052] FIG. 5 is a process flow diagram of a method 500 to regulate the temperature of components of a computer system with immersion cooling by using an artificial peristalsis device. In some examples, the components utilized in method 300 can be described with respect to like items from previous figures discussed herein. In some examples, method 500 can be performed with computer device 400 of FIG. 4. The method 500 begins at block 502.

[0053] At block 502, a PCB in a case is immersed with a thermally conductive and electrically nonconductive viscous fluid. The viscous fluid can be, for example, paraffin wax, as described herein. Ideally this viscous wax must be able to be pumped. To this end, additives may be used to make the viscous fluid of paraffin wax behave more like a fluid, especially at low temperatures. Additives used in small amounts can include, for example, moderately combustible additives like kerosene or petroleum oils, or more highly volatile additives like methanol, ethanol, or propanol. When such additives are used, safe and effective measures should be in place to rapidly return the highly volatile gaseous phases of such material to the liquid phase, which mixes back into the viscous coolant fluid.

[0054] At block 504, an artificial peristalsis device is used to circulate the viscous fluid and create a prevailing flow of the viscous fluid is created across the PCB. The artificial peristalsis device is coupled to the PCB so that it does not potentially become twisted or otherwise disoriented, thereby avoiding reducing or eliminating the prevailing flow. The prevailing flow can be configured to circulate the viscous fluid in a preferred manner across the PCB, depending in part on the location of heat sources. In some examples, multiple artificial peristalsis devices can be attached throughout the PCB, and configured to direct the flow of the viscous fluid.

[0055] At block 506, the viscous fluid is cooled by introducing cold water in a hose around the artificial peristalsis device. This cooling causes the artificial peristalsis device to relax and widen, allowing more viscous fluid inside the artificial peristalsis device. A one-way valve can be used to ensure that the viscous fluid may enter the artificial peristalsis device without escaping back through the entrance of the artificial peristalsis device.

[0056] At block 508, ambient heat is absorbed from the computer system and PCB. The heating of the viscous fluid by the ambient heat allows the viscous fluid to be pumped more easily through the artificial peristalsis device. The increased heat causes the artificial peristalsis device to constrict as the viscous fluid absorbs and transfers ambient heat to the artificial muscles. [0057] At block 510, the viscous fluid is circulated above the PCB by cooling and relaxing the artificial peristalsis device, and by absorbing heat and constricting the artificial peristalsis device. This cycle of relaxing and constricting effectively pumps the viscous fluid around the PCB, while providing an efficient means of temperature regulation throughout the PCB. The steps of method 500 effectively pump the viscous fluid along the prevailing flow created by the artificial peristalsis device or a number of artificial peristalsis devices.

[0058] In some examples, method 500 can include using a heat sensor and a cooling management system to speed up or slow down viscous fluid that is cooled outside of the box and pumped inside. In other examples, method 500 can include using a heat sensor and cooling management system to activate heat pumps, such as Peltier devices, during peak workloads and heat generation. In some examples, if the box of electronics is large and has sub-assembly components that shed heat at variable rates, then the method 500 can include steering the flow of the viscous fluid, selectively, within the box. In examples where the viscous fluid includes an additive that is volatile and combustible, the method 500 can include using an expansion vessel to collect a gaseous component of the viscous fluid that escapes as heated and condense it, returning it to the liquid phase and into the viscous fluid. In some examples, the viscous fluid may include heavier solids that settle out of the mixture, accumulating at areas of low flow rate, and potentially reducing cooling efficiency. In such an example, brushes that are immersed in the viscous fluid can be used to stir the solids preferentially in a certain direction. In such an example, brushes can be coupled to an artificial peristalsis device and configured to move back and forth in accordance with the constricting and relaxing mechanism described herein, and depicted by FIG. 6.

[0059] The method 500 of FIG. 5 is not intended to indicate that method 500 is to include all of the steps shown in FIG. 5. Further, any number of additional steps may be included within the method 500, including, but not limited to, steps from the examples described in the preceding paragraph, or steps described with respect to method 300 in FIG. 3, for example.

[0060] FIG. 6 is a block diagram of a computer system 600 with a case 602 and printed circuit board (PCB) 604 configured for immersion cooling using an artificial peristalsis device 606 and a brush device 608 to circulate a viscous coolant fluid 610. Components of computer system 600 can be described, for example, with respect to like items from FIG. 4. FIG. 6 is intended to be a side perspective view of computer system 600 with case 602.

[0061] Depending on the ingredients of the viscous coolant fluid 610, there may be problems with heavier solids settling out of the mixture. Such solids would tend to accumulate in areas of low rates of flow. Over time this accumulation of solids may reduce cooling efficiency. The bristles of the brush device 608 would be pulled back and forth in alternate directions by artificial muscles of the artificial peristalsis device 606. The artificial peristalsis device 606 can be water-cooled, and cooled and heated by the viscous coolant fluid 610 using techniques described herein. In some examples, if the brush device 608 can be protectively fenced, it can serve both the sediments-stirring function while also shielding delicate components of the PCB 604. For example, if the PCB 604 being cooled has many heat generating Voltage Regulator Modules (VRMs) 612 rising vertically up out of the horizontal plane of the motherboard, these VRMs 612 and similar protruding components 614 can be protected, as well as cooled. In some examples, the VRMs 612 could be arranged in a row, with a long brush of a brush device 608 that is pulled lengthwise in an alternating fashion. In some examples, the outermost brush bristles can be long and stiff, so as to stir solid sediments off of the PCB 604, and to provide the fencing function for the VRMs 612 as well. In some examples, the central bristles of the brush device 608 can be shorter and softer to help stir the viscous coolant fluid 610 around the VRMs 612, and to protect the VRMs 612 from potential damage by the moving viscous coolant fluid 610.

[0062] A set of springs 616 can also be included in or around the case 602. In some examples, cold water is being pumped into the computer system 600 by cold water hoses. In some examples, as the cold water absorbs ambient heat from the viscous coolant fluid 610 and components of the PCB 604 and is pumped out of the computer system 600, the volume of fluid within the computer system 600 will change. The springs 616 help to allow for slight movement within the case 602 so that the PCB 604, VRMs 612 and other components 614 are not damaged.

Additionally, due to thermal expansion and contraction of the viscous coolant fluid 610, there can also be increases and decreases in total volume within the case 602. The springs 616 can help to prevent the buildup of pressure on certain components 614 of the computer system 600, and to keep the case 602 balanced. In some examples, flexible walls 618 at the periphery of the case 602 can also be included so the top of the case 602 can be displaced up or down in response to changes in volume. The springs 616 can ensure the top of the case 602 does not get out of alignment.

[0063] In some examples, a set of ballast chambers (not shown) at each end of the sliding brush device 608 could be alternately inflated with cold water and deflated by pumping hot water back out. The ballast chambers can be configured to provide motion power for the viscous coolant fluid 610 as with the artificial peristalsis device 606. In some examples, the brush bristles of brush device 608 can be arranged so as to push viscous coolant fluid 610 and solid particulates preferentially in one direction. In such an example, the brush bristles can be slanted in one direction, or preferentially fold in one direction, and not the other. In some examples, finer sub-bristles can be configured to branch off of the main bristles.

[0064] The block diagram of FIG. 6 is not intended to indicate that the computer system 600 is to include all of the components shown in FIG. 6. Any number of additional components may be included within the computer system 600, depending on the details of the devices and specific implementation of immersion cooling described herein. For example, a heat pump, such as a Peltier device that utilizes current to create a temperature drop across thermoelectric plates of the device, can be included and controlled to run by anticipating times of peak workloads and heat generation. Additionally, in some examples, a heat sink or multiple heat sinks cooled by air or otherwise can be placed in proximity to a hottest component of the PCB 604, such as a processor or VRM 612, to assist with dissipating ambient heat. Also, additional heat sinks can be placed on top of or within the case 602 to assist in cooling. Further, the items discussed are not limited to the functionalities mentioned, but the functions could be done in different places, or by different components.

[0065] FIGS. 7A and 7B are diagrams of a system 700 with a valve 702 actuated by an artificial muscle 704. The system 700 can be a case or container, for example, a case that houses electrical components of a computer device. The valve 702 can be a thermo-mechanical flow control valve that is self-regulating. Force is exerted on the valve 702 by a spring 706. The spring 706 creates a force that to keep the valve 702 in a closed position, as shown in Fig. 7A. The artificial muscle 704 is coupled to a side wall of the system 700 and the valve 702, for example, passing down the inside of the spring 706. The valve 702 can rotate on a hinge 708. The artificial muscle 704 can oppose the force created by the mechanical spring 706, pulling the valve 702 into an open position. The illustration in FIG. 7B shows the valve in the open position.

[0066] The system 700 can be immersed in a fluid. In some examples, the fluid is a coolant fluid that can transfer heat from hotter electrical components that can be housed in the system 700. A higher pressure fluid 710 may be present on the closed side of valve 702, and a lower pressure fluid 712 may be present on the opposite side of the valve 702. The higher pressure fluid 71 0 and the lower pressure fluid 712 are of the same composition. In FIG. 7A, the lower pressure fluid 712 is cold. The cold temperature causes the artificial muscle 704 to relax when cooled, and the mechanical spring 706 then forces the valve 702 shut. In FIG. 7B, the lower pressure fluid 712 is hot. The hot temperature causes the artificial muscle 704 to contract when heated, and the mechanical spring 706 is pulled open through force of the contracting artificial muscle 704. An arrow 714 in FIG. 7B depicts the direction of flow for the fluid from an area of higher pressure to lower pressure when the valve 702 is actuated open by the artificial muscle 704. If the strength of the mechanical spring 706 and the artificial muscle 704 is properly matched, the valve 702 may regulate itself, opening and closing automatically when temperature changes occur within the system 700, and, thus, controlling the temperature of the lower pressure fluid 712.

[0067] FIG. 8 is a diagram showing a case 800 filled with a coolant fluid 802. The case 800 can hold electronics being cooled. The case 800 has an array of inlet valves 804 on one or more sides. The inlet valves 804 may be, for example, the valves described with respect to FIG. 7. A high pressure area 806 may exist on the entry side of the inlet valves 804, and a low pressure area 808 may exist on the exit side of the inlet valves 804. In some examples, the case 800 is filled with computer electronics where the hottest components receive more cooling from the coolant fluid 802, as flow is automatically directed toward the hottest relative areas within the case 800. Where there is more heat being generated within the case 800, an increased flow of the coolant fluid 802 will result. The pressure differential across the inlet valves 804 also helps to direct the coolant fluid throughout the case 800.

[0068] In some examples, an external circulation system (not shown) is used to cool the coolant fluid, and to pump it at a rate suitable to maintain the pressure drop across the inlet valves 804. A control system may measure and react to temperature changes. A pressure sensor (not shown) in the low pressure area 806 and a pressure sensor in the high pressure area 808 can be used to control the amount of energy to the pump that circulates the coolant fluid 802, in order to maintain a suitable degree of cooling. The hottest components, such as large, hot heat source 810, can be located close to the inlet valves 804 to activate opening, and thus control the cooling. Small heat sources 812 may also be located near inlet valves 804 to receive more relative cooling from the coolant fluid 802 entering the case 800. Diffuse or small heat sources 814 can be more centrally located in the case 800, as there is less need for cooling at areas of lower relative temperatures within the case 800.

[0069] As described herein, coolant fluid 802 may be based on a phase- change material like paraffin wax. Such a wax-based fluid would be quite viscous at cold start-up of computer devices within the case 800. At cold start-up, the hot devices can liquefy the coolant fluid 802 next to the inlet valves 804. The inlet valves 804 accept cold coolant fluid 802, and the coolant fluid 802 becomes more liquefied as it is heated. The hotter coolant fluid 802 will form hot streams that naturally flow toward the exit point 816 of the case 800. This establishes flow within the case, and moves the pressure drop back to the barrier with the inlet valves 804, with higher pressure on the outside of the case 800 and lower pressure inside. The case 800 can be suspended by springs 81 8 that are to allow for volumetric changes of the case 802, and to compensate for thermal expansion and volumetric changes of the coolant fluid 802 as it is heated and cooled and moved throughout the case 802.

[0070] In some examples, the coolant fluid 802 can be fully contained within the case 800, e.g., only being circulate within the case 800, without being pumped outside and externally cooled. If the cooling slurry is largely a phase-change material such as paraffin wax, then cooler, more solid wax is denser than hotter, more liquid wax. The hotter, liquid coolant fluid 802 will rise for that reason, as well as for the reason of convection currents. This will efficiently transfer heat from the electrical components in the case 800 to the coolant fluid 802. Heat can then be transferred across, for example, a metal barrier at the top of the case 800, to a top layer that can have a heat sink, a water-cooler, and the like.

[0071] FIG. 9 is a diagram of a system 900 with a valve 902 actuated by an artificial muscle 904 attached to a pulley 906. The system 900 can be as described with respect to FIGS. 7A and 7B. A mechanical spring 908 may hold the valve 902 in a closed position against a hard stop 91 0. The valve 902 can swivel about a hinge 912. The hard stop 91 0 has an internal space, such as a hole, to permit a

connection from the pulley 906 to pass through the hard stop 904 and attach to the artificial muscle 904. The artificial muscle 904 is located in a higher pressure region 914, and a lower pressure region 916 exists on the opposite side of the valve 902.

[0072] As heat is introduced to the system 900, the artificial muscle 904 contracts. As the artificial muscle 904 contracts, the connection from the artificial muscle 904, applies a force on the valve 902 opposite to the force exerted by the spring 908. When the artificial muscles 904 is sufficiently contracted, the valve 902 will be forced open, and coolant fluid within the system can flow in the direction of arrow 91 8. When the system 900 cools down and the artificial muscle 904 in turn cools down, the artificial muscle 904 will relax. As the artificial muscle 904 relaxes, the pulley 906 exerts less force on the valve 902, and the force by the spring 908 forces the valve 902 back into a closed position.

[0073] FIG. 10 is a diagram of a bellows pump 1 000 actuated by a linear actuator 1002. The accordion-style, bellows pump 1 000 includes metal plates 1004 to aid in heat transfer, and a flexible component 1 006 at the corners of each level of the telescoping bellows pump 1000. The flexible component 1006 is to

accommodate for the motion of the bellows pump 1 000, while ensuring structural stability. One-way valves 1008 on either end of an internal hose 101 0 help ensure that fluid is only moved in one direction through the bellows pump 1000. The internal hose 1 010 is to be flexible enough to move along with the bellows pump 1000.

[0074] The linear actuator 1 002 act on the bellows pump 1 000 by forcing it to actuate back and forth in a linear direction. The linear actuator 1 002 can include, for example, a hydraulic cylinder, a pneumatic cylinder, or a rotating motor that creates the desired linear motion of the bellows pump 1000. The linear actuator 1002 can include, for example, artificial muscles to drive the linear motion of the bellows pump 1000. In such an example, the artificial muscles respond to temperature changes, constricting and relaxing and thereby driving the actuation of the bellows pump 1000. In some examples, a control mechanism can be implemented that monitors a pressure differential across a defined pressure wall (not shown) that is perforated by thermo-mechanical flow-control valves, for example, like those illustrated in FIGS. 7A and 7B or FIG. 8. The bellows pump 1000 can be used to circulate a coolant fluid in a system like system 800 or system 900 that have heated electrical components that require cooling.

[0075] While the present techniques may be susceptible to various

modifications and alternative forms, the exemplary examples discussed above have been shown only by way of example. It is to be understood that the technique is not intended to be limited to the particular examples disclosed herein. Indeed, the present techniques include all alternatives, modifications, and equivalents falling within the true spirit and scope of the appended claims.

Claims

1 . A method to circulate a viscous fluid through use of an artificial peristalsis device, comprising:

taking the viscous fluid into the artificial peristalsis device;

pumping cold water through a cold water hose of the artificial peristalsis

device;

cooling the viscous fluid, thereby cooling and relaxing the artificial peristalsis device;

absorbing ambient heat by the viscous fluid, thereby heating and constricting the artificial peristalsis device; and

expelling the viscous fluid from the artificial peristalsis device.

2. The method of claim 1 , further comprising, when the artificial peristalsis device is relaxed and cooled, taking in additional viscous fluid from outside the peristalsis device, and cooling the viscous fluid inside the artificial peristalsis device.

3. The method of claim 1 , wherein as the artificial peristalsis device constricts the viscous fluid is pumped through the artificial peristalsis device in one direction.

4. The method of claim 1 , further comprising slowly pumping heated water out from the cold water hose that has absorbed heat from the viscous fluid circulated by the artificial peristalsis device, collapsing the cold water hose, and further constricting the artificial peristalsis device.

5. The method of claim 1 , wherein the viscous fluid comprises a phase- changing material that is thermally conductive and not electrically conductive, wherein the phase-changing material comprises a mix of paraffin wax, an additive to increase the fluidity of the mix at low temperature, and an additive to increase the thermal conductivity of the mix.

6. The method of claim 1 , further comprising bracing the artificial peristalsis device to keep from unwinding, thereby ensuring consistent circulation of the viscous fluid through the artificial peristalsis device.

7. The method of claim 1 , further comprising controlling the flow of the viscous fluid using a valve connected to a mechanical spring and an artificial muscle.

8. An artificial peristalsis device, comprising:

an artificial muscle;

a flexible sheath covering the artificial muscle;

an inner hose used to circulate a viscous fluid, wherein the inner hose has a one-way flow valve to control flow direction of the viscous fluid through the inner hose; and

a cold water hose that is spiral wrapped around the inner hose, and wherein the artificial muscle is co-wrapped with the cold water hose.

9. The artificial peristalsis device of claim 8, wherein the artificial muscle is comprised of highly twisted monofilament string that contracts when heated and relaxes when cooled.

10. The artificial peristalsis device of claim 8, further comprising a valve connected to a spring and an artificial muscle used to control the flow of the viscous fluid based on changes in temperature.

1 1 . The artificial peristalsis device of claim 8, further comprising a valve connected to a spring and a pulley, wherein the pulley is connected to an artificial muscle and is to actuate the valve open and closed based on changes in

temperature.

12. A method for providing temperature regulation in a computer system with immersion cooling, comprising:

immersing a printed circuit board (PCB) in a box with a viscous fluid; using an artificial peristalsis device to circulate the viscous fluid and create a prevailing flow of the viscous fluid across a the PCB, wherein the artificial peristalsis device is coupled to the PCB;

cooling the viscous fluid by introducing cold water in a hose around the artificial peristalsis device, wherein the artificial peristalsis device relaxes as it is cooled;

absorbing ambient heat from the computer system and PCB, wherein the artificial peristalsis device constricts as it is heated by the viscous fluid as the viscous fluid absorbs the ambient heat; and

circulating the viscous fluid above the PCB by cooling and relaxing the artificial peristalsis device and by absorbing heat and constricting the artificial peristalsis device, thereby pumping the viscous fluid along the prevailing flow created by the artificial peristalsis device.

13. The method of claim 12, wherein the viscous fluid is comprised of a material that is thermally conductive and electrically nonconductive.

14. The method of claim 12, further comprising forcing solids that settle out of the viscous fluid to circulate by coupling brushes to the artificial peristalsis device.

15. The method of claim 12, further comprising controlling the flow of the viscous fluid using a valve connected to a mechanical spring and an artificial muscle.