CN115968437A - Heat pipe, system and method for switching and/or programming heat transfer - Google Patents
Heat pipe, system and method for switching and/or programming heat transfer Download PDFInfo
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- CN115968437A CN115968437A CN202180047345.0A CN202180047345A CN115968437A CN 115968437 A CN115968437 A CN 115968437A CN 202180047345 A CN202180047345 A CN 202180047345A CN 115968437 A CN115968437 A CN 115968437A
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Images
Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F28—HEAT EXCHANGE IN GENERAL
- F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
- F28D15/00—Heat-exchange apparatus with the intermediate heat-transfer medium in closed tubes passing into or through the conduit walls ; Heat-exchange apparatus employing intermediate heat-transfer medium or bodies
- F28D15/02—Heat-exchange apparatus with the intermediate heat-transfer medium in closed tubes passing into or through the conduit walls ; Heat-exchange apparatus employing intermediate heat-transfer medium or bodies in which the medium condenses and evaporates, e.g. heat pipes
- F28D15/06—Control arrangements therefor
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F28—HEAT EXCHANGE IN GENERAL
- F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
- F28D15/00—Heat-exchange apparatus with the intermediate heat-transfer medium in closed tubes passing into or through the conduit walls ; Heat-exchange apparatus employing intermediate heat-transfer medium or bodies
- F28D15/02—Heat-exchange apparatus with the intermediate heat-transfer medium in closed tubes passing into or through the conduit walls ; Heat-exchange apparatus employing intermediate heat-transfer medium or bodies in which the medium condenses and evaporates, e.g. heat pipes
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F28—HEAT EXCHANGE IN GENERAL
- F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
- F28D15/00—Heat-exchange apparatus with the intermediate heat-transfer medium in closed tubes passing into or through the conduit walls ; Heat-exchange apparatus employing intermediate heat-transfer medium or bodies
- F28D15/02—Heat-exchange apparatus with the intermediate heat-transfer medium in closed tubes passing into or through the conduit walls ; Heat-exchange apparatus employing intermediate heat-transfer medium or bodies in which the medium condenses and evaporates, e.g. heat pipes
- F28D15/04—Heat-exchange apparatus with the intermediate heat-transfer medium in closed tubes passing into or through the conduit walls ; Heat-exchange apparatus employing intermediate heat-transfer medium or bodies in which the medium condenses and evaporates, e.g. heat pipes with tubes having a capillary structure
- F28D15/046—Heat-exchange apparatus with the intermediate heat-transfer medium in closed tubes passing into or through the conduit walls ; Heat-exchange apparatus employing intermediate heat-transfer medium or bodies in which the medium condenses and evaporates, e.g. heat pipes with tubes having a capillary structure characterised by the material or the construction of the capillary structure
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F28—HEAT EXCHANGE IN GENERAL
- F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
- F28F13/00—Arrangements for modifying heat-transfer, e.g. increasing, decreasing
- F28F2013/005—Thermal joints
- F28F2013/008—Variable conductance materials; Thermal switches
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F28—HEAT EXCHANGE IN GENERAL
- F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
- F28F2245/00—Coatings; Surface treatments
- F28F2245/02—Coatings; Surface treatments hydrophilic
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F28—HEAT EXCHANGE IN GENERAL
- F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
- F28F2245/00—Coatings; Surface treatments
- F28F2245/04—Coatings; Surface treatments hydrophobic
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- Engineering & Computer Science (AREA)
- Life Sciences & Earth Sciences (AREA)
- Sustainable Development (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Cooling Or The Like Of Semiconductors Or Solid State Devices (AREA)
- Cooling Or The Like Of Electrical Apparatus (AREA)
Abstract
The invention relates to a heat pipe (1) having at least one working chamber (2) which has at least one evaporator region (3) which is operatively connected to a heat source and at least one condenser region (4) which is operatively connected to a heat sink, a working fluid (5) being provided in the working chamber (4), and in a first operating state heat being transferred from the heat source to the heat sink via the working fluid (5). It is essential that the heat pipe (1) is designed as a switchable and/or programmable thermal diode or as a switchable and/or programmable thermal switch in that at least one activatable functional material is provided, which functional material is designed and arranged to keep the evaporator region (3) free of working fluid (5) and/or to prevent evaporation of the working fluid (5) in the second operating state in order to reduce and/or prevent heat transfer and/or to change the preferred direction of heat conduction. Furthermore, the present invention relates to a system and a method for switching and/or programming the heat transfer in a heat pipe.
Description
Technical Field
The present invention relates to a heat pipe according to the preamble of claim 1, a system with a heat pipe according to claim 12 and a method for switching and/or programming the heat transfer in a heat pipe according to the preamble of claim 15.
Background
Heat pipes (also known as Heatpipe) are known to transfer heat by the heat of vaporization and can achieve high heat flux densities. Typically, a heat pipe has a hot side, i.e. a heat source, and a cold side, i.e. a heat sink. A working fluid is provided in the heat pipe, which working fluid evaporates in the region of the heat source and condenses in the region of the heat sink. Heat transfer is achieved by the transport of the working fluid and by the transfer of latent heat of condensation and evaporation.
The known heat pipe has a preferred direction for the heat flow, i.e. it is constructed as a thermal diode. This means that such a diode conducts heat very well in one direction and very poorly in the opposite direction.
Such thermal diodes are described, for example, in Boreyko et al 2001, applied Physics Letter 99 (23) and in the document US 8716689 B2. By using a super-hydrophobic coating in the area of the heat sink and a super-hydrophilic coating in the area of the heat source, a preferred direction of heat for the thermal diode results: the surface in the region of the heat sink repels the working fluid by means of the superhydrophobic coating, so that the working fluid is transported back into the superhydrophilic region of the heat source and is evaporated again there.
The disadvantage of the thermal diodes known from the prior art is that the preferred direction of heat transfer is predefined and, due to the design, the diode behavior is fixed, i.e. cannot be changed or adapted during ongoing operation.
Disclosure of Invention
The object of the present invention is therefore to provide a heat pipe or a method for transferring heat, which is variable and overcomes the limitations of the methods and devices known from the prior art.
This object is achieved by a heat pipe according to claim 1, and by a method for switching and/or programming the heat transfer in a heat pipe according to claim 15. Preferred embodiments of the heat pipe according to the invention are given in the dependent claims 2 to 11. The design of a system with a heat pipe according to the invention is given in claims 12 to 14. Preferred embodiments of the method according to the invention are given in claims 16 and 17. All claims are hereby expressly incorporated by reference into this specification in their entirety.
As is known per se, a heat pipe according to the invention comprises at least one working chamber having an evaporator region and at least one condenser region. The evaporator region is operatively connected to a heat source, and the condenser region is connected to a heat sink. A working fluid is disposed in the working chamber. In a first operating state, heat is transferred from the heat source to the heat sink via the working fluid.
It is essential that the heat pipe is designed as a switchable and/or programmable thermal diode or thermal switch in that at least one activatable functional material is provided, which functional material is designed and arranged to keep the evaporator region free of working fluid and/or to prevent evaporation of the working fluid in the second operating state, in order to reduce and/or prevent heat transfer and/or to change the preferred direction of heat conduction for the heat transfer.
The working fluid fills the working chamber and, depending on the pressure and temperature, exists in both liquid and gaseous forms. The expression "keeping the evaporator region free of working fluid" refers to the direct contact and/or the direct interaction of the working fluid in the liquid phase with the surface of the evaporator region. Here, it is also within the scope of the invention that in the evaporator region the working fluid is present in the gaseous phase, since the gaseous phase of the working fluid fills the entire volume of the working chamber of the heat pipe.
The invention is based on the applicant's recognition that by appropriately designing the conditions in the working chamber it is possible to control the heat transfer and even reverse the heat transfer.
The heat pipe according to the invention thus differs from previously known heat pipes in some important respects:
an activatable functional material is provided in the heat pipe, which functional material can be changed from a first state (first operating state of the heat pipe) to a second state (second operating state of the heat pipe). In the first state, the activatable functional material allows heat transfer in the preferred direction of heat conduction in the first operating state or has no effect on the function of the heat pipe. In a second state, the activatable functional material keeps the evaporator region free of working fluid or prevents the working fluid from evaporating. Since heat transfer in the heat pipe is primarily achieved by evaporation of the working fluid in the evaporator region and delivery of the evaporated working fluid to the condenser region, this reduces or prevents heat transfer in the heat pipe. It is also within the scope of the invention for the activatable functional material to be designed such that in the second operating state the preferred direction of heat conduction is changed by the activatable functional material.
In a preferred embodiment of the invention, the heat pipe is designed as a switchable thermal diode or a thermal switch in that the at least one activatable functional material is designed to change its properties at least partially in an external field. Possible properties of the activatable functional material that can be changed by an external field are surface wetting properties, swelling capacity, fluid binding properties and volume.
In an alternative embodiment of the invention, the heat pipe is designed as a programmable thermal diode or a thermal switch in that the at least one activatable functional material is designed to change its properties at least partially as a function of the conditions inside the working chamber. Possible properties of the activatable functional material that can be changed by an external field are surface wetting properties, swelling capacity, fluid binding properties and volume.
The activatable functional material can thus preferably be switched or programmed by external or internal influences. "switchable" in this case means that the operating state can be changed by actively applying an external field. By "programmable" is meant in this case that the heat pipe itself changes state through internal factors inherent to the material when environmental conditions, particularly conditions in the working chamber, change.
This achieves the advantage that the heat transfer in the heat pipe according to the invention can be controlled in a targeted manner.
In a preferred embodiment of the invention, the heat pipe is designed as a programmable thermal diode or as a thermal switch in that the at least one activatable functional material is designed to change its properties as a function of the conditions inside the working chamber, in particular as a function of the temperature, the pH of the working fluid and/or the ionic strength of the working fluid. Thus, advantageously, no external field is required, but heat transfer in the heat pipe can be controlled solely by the working fluid or by the direct properties of the heat pipe.
The working chamber is preferably designed as a closed space, in particular as a heat transfer by convection of the evaporated working fluid and by a return of the condensed working fluid from the condenser region to the evaporator region. In particular, the closed space of the working chamber is designed as a pressure-tight system. In particular all extraneous gases except the working fluid, are substantially removed from the pressure-sealed system. For this purpose, different designs are conceivable, which differ by the return flow of the working fluid. It is known here to design heat pipes or two-phase thermosiphons.
The activatable functional material is disposed within the working chamber. The activatable functional material can also be provided here as part of the working chamber, for example as a bottom or a top cover of the working chamber.
In a preferred embodiment of the invention, the heat pipe is designed with a fluid circuit for a working fluid. Preferably, the fluid circuit comprises a fluid return arrangement for returning condensed working fluid from the condenser region to the evaporator region. This makes it possible to guide the working fluid back into the evaporator region in a targeted and metered manner and thus to avoid drying out of the evaporator region.
In a preferred embodiment of the invention, the closed space has a fluid-repellent coating and/or structure in the evaporator region and/or a fluid-repellent coating and/or structure in the condenser region. It is also within the scope of the invention for the closed space, i.e. the working chamber, to have additional structure in the evaporator region and/or the condenser region. Thereby, for example, the wetting properties of the surface can be optimized.
The enclosed space has a hydrophilic coating and/or structure in the evaporator region and/or a hydrophobic coating and/or structure in the condenser region and/or an oleophilic coating and/or structure in the enclosed space evaporator region and/or an oleophobic coating and/or structure in the condenser region.
The at least one activatable functional material is preferably configured in the form of a switchable coating of the evaporator region and/or the condenser region of the working chamber in such a way that the surface properties of the coating of the evaporator region can be changed from fluidophilic to fluidophobic. Preferably, the coating of the condenser region of the evaporator region is configured such that the surface characteristics of the coating of the evaporator region can be changed from fluid-philic to fluid-phobic, and the surface characteristics of the coating of the condenser region can be changed from fluid-phobic to fluid-philic. In this case, the heat pipe is configured as a switchable thermal diode: the heat pipe can be changed from the first operating state to the second operating state by applying an external field.
If in the first operating state the hot side, i.e. the evaporator region, is heated by the heat source, the working fluid which collects on the fluid-philic coating of the evaporator region evaporates and makes it possible to transfer heat from the evaporator region to the condenser region. Here, the working fluid condenses on the fluidtight coating of the condenser region. The working fluid may form droplets due to the surface characteristics of the lyophobic in the condenser region. In designs where the surface is strongly lyophobic, the working fluid "bounces" back into the evaporator region. Alternatively, the fluidic back-guiding of the droplets can also be achieved by providing capillary forces, for example in the form of a hydrophilic wick structure, as is the case with heat pipes known from the prior art. In this state, the thermal diode is thermally conductive.
If in a second operating state (also referred to below as the cut-off state) the surface properties of the coating in the evaporator region and/or the condenser region are changed, for example by applying an external electric field, the hot side at the heat source, i.e. the evaporator region, now has hydrophobic properties. The working fluid does not collect sufficiently on this coating and the working fluid that collects there quickly evaporates and condenses on the fluid-philic coating in the condenser region. The working fluid remains there and does not flow back into the evaporator region because the above-described back-flow mechanism is not effective. Whereby the hot side of the working chamber dries out and no heat transfer takes place by the working fluid. The thermal diode is turned off.
Preferably, the switchable coating is configured as
And/or has +>
Are inorganic-organic hybrid polymers that can favorably affect the surface characteristics of a wide variety of substrates, see, e.g., sanchez et al, chem. Using a mechanism known from the specialist literature,
coatings that can also be configured to switch from hydrophilic to hydrophobic, and vice versa, see b.xin, j.hao, chem.soc.rev.30,2010,769-782. According to the invention>
Containing, for example, imidazolidinyl-end groups (imidazolium-Endgruppen) to obtain electrically switchable surface properties, or fluoroalkyl azobenzene (fluoroalkylazobenzole) or Spiropyran-end groups (spiropyropyran-Endgruppen) to obtain photochemically switchable surface properties. />
In a particularly preferred embodiment of the process according to the invention,
the coating has microscopic, mesoscopic or nano-structures that enhance its fluidophilic/fluidophobic properties by utilizing the capillary or lotus effect.
In a preferred embodiment of the invention, the activatable functional material is designed such that the evaporator region and the condenser region interchange properties in the second operating state. The second operating state is thus not an off state, but rather a heat transfer in the opposite direction to the first operating state. In this case, in the second operating state, the working fluid can evaporate in the original condenser region, which now represents the evaporator region, and absorb heat from the heat source and deliver heat to the original evaporator region, which now represents the condenser region. The working fluid condenses in this new condenser region and releases heat to the heat sink. Thereby reversing the preferred direction of thermal conduction of the thermal diode.
The activatable functional material is preferably configured in both the evaporator region and the condenser region
And (4) coating. Such a coating is chosen such that the surface wetting properties of the evaporator area and the condenser area are interchanged by applying an external field, preferably an electric field or a radiation field, i.e. (UV) light radiation.
To achieve the electric switchability of the fluidophilic/fluidophobic properties according to the invention, use is made, for example, of
The functional end groups of which consist of ionic groups (Trialkylammonium-, imidazole-, sulfonate-, etc.) which are bound via a "spacer", that is to say a linear alkyl chain (linear alkyl key) and/or ion chain having 2 to 20C atoms, preferably 3 to 12C atoms>
The network structure is covalently bound. By applying an electric field (see Langer et al, science 299,2003, 371-374), the ionic end groups are repelled by the similarly charged matrix and extend into the internal cavity of the thermal diode, which results in a surface with hydrophilic properties. On the other hand, the ionic groups are attracted to the oppositely charged substrate, so that nonpolar "spacer" chains extend into the internal cavity of the thermal diode, which results in a hydrophobic surface. That is to say if two mutually opposite sides of the thermal diode are coated with the same functional->
A hydrophilic side and a hydrophobic side are formed by applying an electric field, and at this time, the characteristics are also reversed by reversing the direction of the field. The voltage applied to the thermal diode is preferably<50V, particularly preferably<5V。
In an alternative embodiment of the invention, the at least one functional material is designed in the form of a reservoir for the working fluid, in particular a liquid reservoir. The absorption or release of the working fluid required for heat transfer is controlled by such reservoirs. This means that the amount of working fluid available can be made variable. In a first operating state of the heat pipe, a working fluid is provided for heat conduction. The heat pipe conducts heat. In a second operating state, the blocking state, the working fluid is confined in the reservoir, in particular in the form of a liquid reservoir. In this form of confinement, the working fluid is no longer available for heat transfer. The heat pipe is no longer thermally conductive.
Within the scope of the present invention, the expression "the heat pipe is no longer conducting heat" refers to the off-state of the diode. This means that the heat transfer is significantly reduced compared to the other switching state. Nevertheless, a small heat flow can occur, for example, also by thermal conduction through the component.
Preferably, the reservoir for the working fluid is configured as a gel, in particular as a polymer gel, as an adsorbent or as a mesostructured surface.
Particularly preferably, the reservoir is configured as a chemically cross-linked polymer gel. The cross-linked polymer gel is designed to swell under the action of a working fluid and has a volume phase transition, preferably between the swollen and the collapsed state of the hydrogel.
Particularly where the working fluid is water, the reservoir is preferably configured as a hydrogel that binds water. The polymer gel has a state of bound water and unbound water. Preferably, the transition of the heat pipe from the first operating state to the shut-off operating state, i.e. the transition from the fluid-unbound state of the polymer gel to the fluid-bound state of the polymer gel, is initiated by a temperature change. The polymer gel may be configured as a volume phase-change polymer gel having a UCST type (upper critical solution temperature) or an LCST type (Lower critical solution temperature). For volume phase transition of the UCST type, the crosslinked polymer gel expands due to the working fluid only when the critical temperature (limit temperature) is exceeded. For LCST-type volume phase transitions, below a critical temperature (limit temperature), the working fluid is expelled from the crosslinked polymer gel. Thus, for UCST type phase changes, the heat pipe is cut off above the critical temperature. For LCST type phase changes, the heat pipe is cut off below the critical temperature. Thus, the limit temperature may be used to define a switching temperature for a transition from the first operating state to the off state of the heat pipe.
Known polymers having UCST volume phase transitions are described, for example, in macromol. Known polymers with LCST volume phase transition are described, for example, in adv. Poly.sci.242, 29-89,2011. The polymer interacts with water and is therefore particularly suitable for heat pipes using water as the working fluid. There is also a series of polymers that have the properties and the behavior described with organic fluids, such as for example mineral oil, see for example j.polym.sci.a46,5724-5733,2008. In this case, a fluid other than water may be used as the working fluid.
In a preferred embodiment of the invention, the reservoir is designed as a sorbent. The sorbent is combined with the fluid. The amount of fluid bound in the adsorbent is also referred to as the adsorption amount. As the temperature (and hence the vapor pressure of the bound fluid) increases, the amount of adsorption of the adsorbent decreases and the fluid is re-released.
Preferably, the adsorbent has a threshold temperature, so that the fluid is released again very suddenly when the threshold temperature is exceeded or when the vapor pressure determined by the fluid is exceeded. Thus, the limit temperature may be used to define a switching temperature for the transition of the heat pipe from the cut-off state to the first operating state.
An example of a material for an adsorbent having a defined threshold temperature or fluid vapor pressure associated therewith is Mitsubishi TM Adsorbent of (2) AQSOA TM -Z05。
It is also within the scope of the invention that the properties of the liquid reservoir are influenced not only by temperature but also by other physical or chemical stimuli. Examples of this are UV light or microwave radiation and the pH value, the ionic strength or the presence of defined organic atoms. Examples of this are described in Angew. Chem. Int. Ed.55,6641-6644, 2015. The switching of the thermal diode is thus effected by different factors and can be adapted accordingly to the field of application and to the environmental conditions.
The object according to the invention is also achieved by a system comprising a heat pipe having the above-mentioned properties according to the invention and a mechanism for loading a field in order to change the properties of the activatable functional material.
Preferably, as means for applying a field, an E-field, a B-field, a stress-strain field, a field generator for generating light, in particular UV light, for generating heat and/or for generating cold are provided. Either only one or a combination of a plurality of the mentioned field generators may be provided. Examples of this include condensers, coils, eccentrics, (UV) light sources or heating and cooling devices. The control strategy can thus be adapted individually to the working fluid used and to the activatable functional material used.
The system according to the invention also has the advantages and features described above for the heat pipe according to the invention and/or for the preferred embodiments of the heat pipe.
The system is preferably designed to be flexible with respect to the hot and cold sides. If the heat pipe is configured with a preferred direction of reversible heat conduction, means are preferably provided which allow the evaporator region and the condenser region to obtain their function in a defined manner by contact with the hot side or, respectively, with the cold side. Preferably, good thermal contact is provided between the evaporator region and the condenser region and the hot side or the cold side, respectively. The heat sink and the heat source are in good thermal contact with the heat pipe.
In a preferred embodiment, the system is a heat pipe formed from a combination of two functional materials, one of which is designed as the above-described liquid reservoir, in particular in the form of a polymer gel. The other functional material is preferably configured to be variable in its lyophilic/lyophobic properties
Preferably variable under the influence of light, in particular UV light.
The object according to the invention is also achieved by a method having the features of claim 15. As is known per se, the method for switching and/or programming the heat transfer is carried out with a heat pipe having at least one working chamber with at least one evaporator region and at least one condenser region and a working fluid. Here, the method comprises the following method steps:
a evaporating the working fluid in the evaporator region, heat being transported with the gaseous working fluid from the evaporator region to the cooler region,
b condenses the working fluid in the cooling area, at which time heat is conducted away to the heat sink.
It is important to operate the heat pipe as a thermal diode or thermal switch by applying an external field and/or varying the thermal conductivity depending on the conditions inside the working chamber.
The method according to the invention is preferably designed for execution by a heat pipe according to the invention and/or a preferred embodiment of a heat pipe according to the invention. The heat pipe according to the invention is, in contrast, designed for carrying out the method according to the invention and/or preferred embodiments of the method according to the invention.
The method according to the invention likewise has the advantages and features of the heat pipe according to the invention and/or of the system according to the invention described above.
The thermal conductivity of the heat pipe is preferably altered by keeping the evaporator region free of working fluid and/or preventing evaporation of the working fluid.
In a preferred embodiment of the invention, in the heat pipe, heat is transported in the first operating state from a hot side (heat source) arranged on the evaporator region to a cold side (heat sink) arranged on the condenser region. The heat pipe is switched to the second operating state by applying an external field in method step C. For this purpose, the activatable functional material is preferably loaded with light, in particular UV light, with heat and/or with cold, or with an E-field, B-field, stress-strain field. In the second operating state, no working fluid or at least no sufficient working fluid is provided in the evaporator region. The evaporator area dries out and the heat pipe no longer conducts heat in the preferred direction of heat conduction for the first operating state.
Alternatively, the working fluid may be changed from the first operating state to the second operating state depending on the conditions inside the working chamber. Parameters that may cause a transition from the first operating state to the second operating state are temperature, pH of the working fluid, and/or ionic strength of the working fluid. The advantage is thereby obtained that the heat pipe can be "programmed" to change operating conditions under certain conditions without external influences being required.
The working fluid is preferably discharged from the evaporator region of the working chamber by means of a switchable surface coating, as already explained above.
Alternatively, the working fluid may be incorporated by an activatable functional material. For this purpose, the at least one activatable functional material is preferably designed in the form of a reservoir for a working fluid, in particular a liquid reservoir. The absorption or release of the working fluid required for heat transfer is controlled by the reservoir. This means that the amount of working fluid available can be varied. In a first operating state of the heat pipe, the working fluid is available for heat conduction. The heat pipe conducts heat. In the second operating state, i.e. the blocking state, the working fluid is confined in the reservoir, in particular in the form of a liquid reservoir. In this form of confinement, the working fluid is not available for heat transfer. The heat pipe is no longer thermally conductive.
In a preferred embodiment of the invention, the preferred direction of heat conduction of the thermal diode is reversed by applying an external field and/or by interchanging the surface properties of the evaporator region and the condenser region depending on the conditions inside the working chamber. In this case, in the second operating state, the working fluid is evaporated in the original condenser region, which now represents the evaporator region, and heat is absorbed from the heat source and transported to the original evaporator region, which now represents the condenser region. In this new condenser region, the working fluid condenses and releases heat to the heat sink. The preferred direction of heat conduction is thereby reversed relative to operating state 1.
The heat pipe according to the invention, the system according to the invention and the method according to the invention are particularly suitable for effectively switching on and off the heat flow, or for controlling or regulating the heat flow. Thermal switches or thermal diodes based on heat pipes are particularly suitable, since such heat pipes can achieve a high switching factor and have only a small thermal resistance in the on-state due to the high heat transfer. Furthermore, such a heat pipe can be realized in a very compact structural form and can therefore be easily integrated. According to a particular design, the heat pipe can be simply constructed, comprising fewer parts, and does not need to contain moving parts.
Drawings
Further preferred features and embodiments of the heat pipe according to the invention and of the method according to the invention are explained below with reference to the examples and the figures. Wherein:
figure 1 shows a schematic view of a first embodiment of a heat pipe according to the invention,
fig. 2 shows a schematic view of a second embodiment of a heat pipe according to the present invention.
Detailed Description
Fig. 1 shows a schematic representation of a thermal diode in which activatable functional material is present in the form of a switchable coating in the evaporator region and in the condenser region, some of which are illustrated a) in the on state and b) in the off state.
The heat pipe 1 has a working chamber 2 with at least one evaporator region 3 and at least one condenser region 4. The evaporator region 3 is operatively connected to a heat source (not shown) which in the present case has a temperature T 1 =100 ℃, and the condenser area 4 is connected to a heat sink (not shown) having a temperature T 2 =10 ℃. A working fluid 5 is provided in the working chamber 2.
The working chamber 2 is in the present case designed as a closed, pressure-tight space, which is designed to transfer heat by convection of the evaporated working fluid 5 and to convey back the condensed working fluid 5.
The working fluid 5 is in the present case water.
The evaporator region 3 and the condenser region 4 are constructed with a coating 6 made of an activatable functional material. The evaporator zone 3 as well as the coating 6 of the condenser zone 4 are constructed such that the surface properties of the coating 6a of the evaporator zone 3 change from hydrophilic to hydrophobic and can be reversed, while the surface properties of the coating 6b of the condenser zone 4 change from hydrophobic to hydrophilic and can be reversed again. Here, the coating 6 is designed such that the evaporator region 3 and the condenser region 4 have exactly opposite surface wetting properties.
In the present case, the coating 6 consisting of activatable functional material is formed from
Consist of and/or have>
Coating 6 of (a). As already explained, is selected>
Are inorganic-organic hybrid polymers (anorganisch-orgaische hybrid polymers) that can advantageously modify the surface properties of many substrates. By means of mechanisms known from the specialist literature>
Coating 6, which can also be configured to switch from hydrophilic to hydrophobic and from hydrophobic back to hydrophilic, see b.xin, j.hao, chem.soc.rev.39,2010,769-782.
In the present case, the coating 6a in the evaporator region 3 and the coating 6b in the condenser region 4 are configured with electrically switchable coatings
As aboveAs described above. In the present case by having a methyl miam>
Dodecyl (Methylimidazolium-dodecylsil) based on functional end groups>
And (4) forming. By applying an electric field (see Langer et al, science 299,2003, 371-374), such ionic end groups are repelled by the similarly charged matrix and extend into the thermal diode's internal cavity by "stretching" of the Dodecyl chain (Dodecyl-Kette). In the present case, the substrates of the evaporator region are configured to carry the same charge. This gives the surface 6a in the evaporator area 3 a hydrophilic character. In the condenser region 4, a substrate of opposite charge is provided. The ionic groups are thereby attracted in opposition, so that nonpolar Dodecyl chains (unpolar Dodecyl-Ketten) extend into the lumen of the thermal diode, which gives the surface 6b in the region of the condenser a hydrophobic character.
The hydrophilic and hydrophobic sides are formed by applying an electric field, and by reversing the field direction, the properties are also reversed.
In the present case, the heat pipe 1 is thus configured as a switchable thermal diode: in a first operating state, heat is transferred from the heat source to the heat sink by evaporation of the working fluid 5, by means of the gaseous working fluid 5 transferring heat from the evaporator region 3 to the condenser region 4. The evaporator region 3 is heated by a heat source, and the working fluid 5 accumulated on the hydrophilic coating 6a of the evaporator region 3 evaporates and enables heat transfer from the evaporator region 3 to the condenser region 4. In the condenser region 4, the working fluid 5 condenses on the hydrophobic coating 6b of the condenser region 4 and conducts heat to the heat sink. Due to the hydrophobic surface properties in the condenser area 4, the formation of droplets of the working fluid 5 occurs. Due to the strongly hydrophobic design of this surface, the working fluid 5 "bounces" back into the evaporator region 3.
By applying an external field, in the present case a voltage of 5V, the heat pipe 1 can be switched from a first operating state in which it is thermally conductive to a second operating state in which it is not thermally conductive.
As illustrated, the surface properties of the coating 6 in the evaporator area 3 and the condenser area 4 are changed by applying an external field. The evaporator area 3 at the heat source now has a hydrophobic character. There is not enough working fluid 5 accumulated on the coating 6a of the evaporator region 3, and the working fluid 5 accumulated therein is rapidly evaporated and condensed on the hydrophilic coating 6b of the condenser region 4. The working fluid 5 remains there and is not transported back into the evaporator region 3, since the now hydrophilic surface does not repel the working fluid 5. The hot side of the working chamber 2 is thereby dried and no heat is transferred by the working fluid 5. The thermal diode is turned off.
Fig. 2 shows a schematic representation of a thermal switch whose activatable functional material is in the form of a liquid reservoir, wherein the partial representation a) is in the on state and b) is in the off state.
To avoid repetition, only the differences from fig. 1 will be discussed below.
In the present case, the at least one activatable functional material is present in the form of a liquid reservoir for the working fluid 5, i.e. in the form of a water-bound hydrogel 7. In this example, the water-binding hydrogel 7 is formed as follows.
Hydrogels with LCST-type volume transitions can be produced, for example, by free-radical polymerization using the following monomers. The mentioned components are not to be understood as exclusive.
The hydrogel having a UCST-type volume transition can be manufactured by radical polymerization, for example, in the case of using the following monomers. The mentioned constituents are not to be understood as exclusive:
furthermore, the possibility exists of producing suitable hydrogels with a volume phase transition by subsequent crosslinking of soluble polymers. In order to obtain hydrogels with an LCST-type volume transition in this way, it is possible, for example, to crosslink partially hydrolyzed polyvinyl acetate (Poly (vinylacetat)) with 1, 4-butanediol diglycidyl ether (1, 4-Butanediglycidylether), polyethylene glycol diglycidyl ether (Poly (ethylene glycol) -diglycidylether) or other di-or multifunctional epoxides (polyfunctional epoxides).
The amount of working fluid 5 available is made variable by the hydrogel 7 binding water. The water-binding hydrogel 7 has a state of bound water and a state of bound water to a significantly lower degree. In the present case, the transition of the heat pipe 1 from the first operating state to the off state, that is to say the state in which the water of hydration of the hydrogel 7 is significantly less, to the state of the bound water, is brought about by a temperature change, in the present case from room temperature to a temperature change of about 150 ℃. This temperature increase is achieved, for example, by heating the hot side of the evaporator side, i.e. without an external field.
In a first operating state of the heat pipe 1, the working fluid 5 is available for heat conduction. The heat pipe 1 conducts heat. In the second operating state, i.e. the blocking state, the working fluid 5 is bound in the bound water hydrogel 7. The working fluid 5 is no longer available for heat transfer in this combined form. The heat pipe 1 is no longer conducting heat.
In contrast to fig. 1, no coating is provided which ensures the return of the working fluid 5 from the condenser region 4 to the evaporator region 3. The heat pipe 1 is thus in the present case constructed with a fluid return structure in the form of a wick structure (not shown).
Claims (17)
1. Heat pipe (1) having at least one working chamber (2) with at least one evaporator region (3) which is operatively connected to a heat source and at least one condenser region (4) which is operatively connected to a heat sink, a working fluid (5) being provided in the working chamber (4) and, in a first operating state, heat being transported from the heat source to the heat sink via the working fluid (5), characterized in that,
the heat pipe (1) is designed as a switchable and/or programmable thermal diode or as a switchable and/or programmable thermal switch in that at least one activatable functional material is provided, which functional material is designed and arranged to keep the evaporator region (3) free of working fluid (5) and/or to prevent evaporation of the working fluid (5) in the second operating state in order to reduce and/or prevent heat transfer and/or to change the preferred direction of heat conduction.
2. A heat pipe according to claim 1, characterized in that the heat pipe (1) is designed as a switchable thermal diode or a thermal switch in such a way that the at least one activatable functional material is designed to change its properties at least partially in an external field.
3. A heat pipe according to claim 1, characterized in that the heat pipe (1) is designed as a programmable thermal diode or a thermal switch in such a way that the at least one activatable functional material is designed to change its properties depending on the conditions inside the working chamber (2), in particular depending on the temperature, the pH of the working fluid (5) and/or the ionic strength of the working fluid (5).
4. A heat pipe according to any of the preceding claims, wherein the working chamber (2) is configured as a closed space configured to transfer heat by convection of evaporated working fluid (5) and by return of condensed working fluid (5), in particular the closed space is configured as a pressure-tight system from which substantially all extraneous gases, preferably other than working fluid (5), are removed.
5. A heat pipe according to any of the preceding claims, wherein the heat pipe (1) is configured with a fluid circuit for the working fluid (5), preferably the fluid circuit comprises a fluid return structure for returning condensed working fluid (5) from the condenser area (4) to the evaporator area (3).
6. A heat pipe according to any of the preceding claims, wherein the enclosed space has a fluid-phobic coating (6) and/or structure in the evaporator region (3) and/or a fluid-philic coating (6) and/or structure in the condenser region (4); in particular, the closed space has a hydrophilic coating (6) and/or structure in the evaporator region (3) and/or a hydrophobic coating (6) and/or structure in the condenser region (4); and/or the closed space evaporator region (3) has an oleophilic coating (6) and/or structure and/or the condenser region (4) has an oleophobic coating (6) and/or structure.
7. A heat pipe according to any of the preceding claims, characterized in that the at least one functional material is configured in the form of a switchable coating of the evaporator region (3) and/or the condenser region (4) in such a way that the surface properties of at least the coating of the evaporator region (3) can be changed from lyophilic to lyophobic.
8. A heat pipe according to any of the preceding claims, wherein the switchable coating (6) is configured as
And/or has +>
9. A heat pipe according to any of claims 1 to 8, characterized in that the at least one functional material is configured in the form of a reservoir for a working fluid (5), in particular a liquid reservoir.
10. A heat pipe according to claim 9, characterized in that the reservoir for the working fluid (5) is configured as a gel, in particular as a polymer gel, as an adsorbent or as a mesostructured surface.
11. A heat pipe according to claim 9 or 10, characterized in that the reservoir for the working fluid (5) is configured as a polymer gel with a temperature induced volume phase change, in particular as a polymer with UCST-type volume phase change or as a polymer with LCST-type volume phase change.
12. A system comprising a heat pipe according to any of the preceding claims wherein means are provided for loading the field to change the properties of the activatable functional material.
13. System according to claim 12, characterized in that a field generator for an electric field, a magnetic field, a stress-strain field, for generating light, in particular UV light, for generating heat and/or for generating cold is provided as a means for loading the field.
14. The system according to claim 12 or 13, wherein the system is configured as a combination of two functional materials, one of which is configured as a liquid reservoir according to any of claims 9 to 11, the other functional material being configured as a liquid reservoir according to any of claims 9 to 11
Which is capable of changing in lyophilic/lyophobic properties, preferably under the influence of light, in particular UV light.
15. Method for switching and/or programming the heat transfer in a heat pipe having at least one working chamber (2) with at least one evaporator region (3) and at least one condenser region (4) and a working fluid (5), comprising the method steps of:
a working fluid (5) is evaporated in an evaporator region (3), heat being transported with the gaseous working fluid (5) from the evaporator region (3) to a condenser region (4),
b the working fluid (5) is condensed in the condenser region (4), in which case heat is conducted away to a heat sink,
it is characterized in that the preparation method is characterized in that,
the heat pipe (1) is operated as a thermal diode or a thermal switch by applying an external field and/or by changing the thermal conductivity depending on the conditions inside the working chamber (2).
16. Method according to claim 15, characterized in that the thermal conductivity of the thermal diode or thermal switch is changed by keeping the evaporator region (3) free of working fluid (5) and/or preventing evaporation of working fluid (5).
17. Method according to claim 15 or 16, characterized in that the preferred direction of thermal conduction of the thermal diode is reversed by applying an external field and/or interchanging the surface properties of the evaporator region (3) and the condenser region (4) depending on the conditions inside the working chamber (2).
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| EP20180665.0 | 2020-06-18 | ||
| EP20180665.0A EP3926285A1 (en) | 2020-06-18 | 2020-06-18 | Heat pipe, system and method for switching and / or programming heat transport |
| PCT/EP2021/066424 WO2021255176A1 (en) | 2020-06-18 | 2021-06-17 | Heat pipe, system and method for switching and/or programming a transport of heat |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN115968437A true CN115968437A (en) | 2023-04-14 |
Family
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202180047345.0A Pending CN115968437A (en) | 2020-06-18 | 2021-06-17 | Heat pipe, system and method for switching and/or programming heat transfer |
Country Status (6)
| Country | Link |
|---|---|
| US (1) | US20230417492A1 (en) |
| EP (1) | EP3926285A1 (en) |
| JP (1) | JP2023531430A (en) |
| KR (1) | KR20230037570A (en) |
| CN (1) | CN115968437A (en) |
| WO (1) | WO2021255176A1 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE102022210523A1 (en) | 2022-10-05 | 2024-04-11 | Vitesco Technologies GmbH | Electric drive system |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2005050717A2 (en) * | 2003-11-18 | 2005-06-02 | Washington State University Research Foundation | Micro-transducer and thermal switch for same |
| JP2007016689A (en) * | 2005-07-07 | 2007-01-25 | Energy Support Corp | Pump and heat exchanger equipped therewith |
| US8716689B2 (en) | 2009-04-21 | 2014-05-06 | Duke University | Thermal diode device and methods |
-
2020
- 2020-06-18 EP EP20180665.0A patent/EP3926285A1/en active Pending
-
2021
- 2021-06-17 WO PCT/EP2021/066424 patent/WO2021255176A1/en active Application Filing
- 2021-06-17 CN CN202180047345.0A patent/CN115968437A/en active Pending
- 2021-06-17 JP JP2022577654A patent/JP2023531430A/en active Pending
- 2021-06-17 US US18/011,247 patent/US20230417492A1/en active Pending
- 2021-06-17 KR KR1020237002195A patent/KR20230037570A/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| US20230417492A1 (en) | 2023-12-28 |
| KR20230037570A (en) | 2023-03-16 |
| WO2021255176A1 (en) | 2021-12-23 |
| JP2023531430A (en) | 2023-07-24 |
| EP3926285A1 (en) | 2021-12-22 |
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