US20100155034A1 - Heat pipe and cooling device used in cryotechnology - Google Patents

Abstract

The invention relates to a heat pipe or cold pipe for cryotechnology, with a casing pipe and with a chamber encapsulated hermetically by a condensation element at one pipe end and by an evaporation element at the other pipe end and filled with a heat transfer medium suitable for cryogenics. So that superconductive elements or components can be cooled to the required transition temperature with high operating reliability and efficiency in a short cooling time, in the chamber, between the condensation element and the evaporation element, at least one cooling module is installed which partially bears with a tubular surface area against the inner surface of the casing pipe and which is provided at least on the condensation element side with a conducting means in order to guide condensed and/or liquid heat transfer medium to the surface area. The invention also relates to a cooling device having a plurality of cold pipes.

Description

• This application claims priority to and the benefit of the filing date of International Application No. PCT/EP2008/004483, filed 5 Jun. 2008, which application claims priority to and the benefit of the filing date of German Application No. 10 2007 027 355.1, filed 11 Jun. 2007, both of which are hereby incorporated by reference into the specification of this application.
• The invention relates to a heat pipe for cryotechnology, with a casing pipe and with a chamber encapsulated hermetically by a condensation element at one pipe end and by an evaporation element at the other pipe end and filled with heat transfer medium. The invention relates, furthermore, to a cooling device for cryotechnology for the cooling of superconductor components, in particular superconductor coils, such as HTS coils (high-temperature superconductor coils), with at least one heat pipe.
BACKGROUND
• The use of heat pipes, as they are known, is known not only in heat exchanger systems, but, for example, also for the cooling of microprocessors and solar modules or for microelectronics cooling. A heat pipe is a heat exchanger which, using the evaporation heat and condensation heat of a substance, makes it possible to have a high heat flow density. The functioning of a heat pipe is based on causing a heat transfer medium to circulate, solely as a result of gravity, in a hermetically encapsulated pipe, in each case with a heat exchange surface for the heat source and for the heat sink, in order, as a result of the phase transition of the heat transfer medium between liquid and gaseous, to extract heat from the space, material or element to be cooled. For gravity-independent circulation, use can be made in the heat pipe of the capillary action of a shaft. Reference is made, merely by way of an example of the prior art for heat pipes, to EP 483 324 B1 which describes a heat pipe coupled thermally to a solar collector.
• When superconductive structural elements, such as, for example, superconductor coils, superconductor generators, linear motors with superconductive coils, superconducting magnets or the like, are employed, it is necessary to cool the superconductive components to a temperature level lying below the transition temperature of the superconductor material. Since a temperature level below about 77 K has to be reached for most superconductive HTS materials, cooling often takes place by means of refrigeration units in the form of cryocoolers with, for example, a closed helium pressure circuit (dry cooling) or in a liquid bath, for example liquid nitrogen (77 K at normal pressure). Conventional low temperature technology, which employs what are known as cryogenic superconductors, even employs for this purpose liquid helium which makes it possible to have an operating temperature of 4.2 K in the liquid bath. Since the aim is to have a temperature level below about −150° C., numerous different refrigeration units or cryocoolers may be used for cryotechnology, cryogenics or low temperature technology.
• Liquid bath cooling, however, has the disadvantage of a high outlay, since a closed and pressure-resistant vessel has to be ensured. If, by contrast, the liquid is allowed to evaporate away, it has to be topped up constantly from a reservoir. The direct contact of a refrigeration unit (cryocooler) with a component to be cooled entails the disadvantage that the discharge of heat takes place via heat conduction in the material, and it is therefore restricted in terms of the distance and the transmittable power or demands the use of a very large amount of additional material which makes practical applications undesirably complicated.
• Reference is made, merely as an example of the use of refrigeration units in the form of cryocoolers, combined with a heat conduction pipe, in a superconductive motor, to DE 102 11 363 A1 in which, between a secondary part, receiving the superconductive coils, of a motor (rotor) and a refrigeration unit having a cold head, a stationary heat pipe is arranged which projects axially into a lateral cavity corotating with the secondary part and which cooperates with a refrigerant (heat transfer medium). The heat transfer medium (refrigerant) consists of a mixture of at least two refrigerant components, the condensed refrigerant being introduced via the heat pipe into the lateral cavity, using a thermosiphon effect, and refrigerant which evaporates in the cavity returning to the condensation unit via the heat pipe. It is known from DE 102 11 363 A1 also to employ a heat pipe for cryotechnology.
• A conventional heat pipe for heating applications is known from US 2005/0257918 A1. An installation element is fitted in the chamber of the casing pipe in order to subdivide the casing pipe into an upper and a lower half. The heat transfer medium, which changes its state of aggregation into hot steam at the evaporation element, rises through the installation element up to the condensation element and is precipitated there as condensate at the inner circumference of the casing pipe, the condensed drops which run off downward from the condensation element to the installation element bringing about heat exchange over the entire casing surface of the upper half. The installation element serves as a collecting ring, in order to transfer the liquid heat transfer medium into a bridging line which branches off outward and which returns liquid heat transfer medium, along a closed line outside the chamber, to the evaporation element.
SUMMARY OF INVENTION
• One of the objects of the invention is to provide a heat pipe for cryotechnology and a cooling device with corresponding heat pipes, by means of which superconductive elements or components can be cooled to the required transition temperature with high operating reliability and efficiency and in a short cooling time. A further object of the invention is to provide heat pipes, by means of which even superconducting components of greater extent can be cooled.
• In a heat pipe, the above objects are achieved, according to the invention, in that, in the chamber, between the condensation element and the evaporation element, at least one cooling module is installed which partially bears with a tubular surface area against the inner surface of the casing pipe and which is provided at least on the condensation element side with a conducting means in order to guide condensed and/or liquid heat transfer medium to the inside of the surface area of the cooling module. The liquid or condensed heat transfer medium runs downward along the inside of the surface area of the cooling module, with the result that heat discharge takes place in a directed manner only in the region of the extent of the surface area. Since the heat pipe according to the invention is to be used for cryotechnology, and since the heat transfer medium employed is a suitable refrigerant for the selected temperature range of cryotechnology, the heat pipe can also be designated as a cold pipe. The cooling module, installed in the heat pipe or cold pipe and bearing only partially in relation to the overall area of the casing pipe against the inner wall of the latter, has the effect that the heat transfer medium or refrigerant causes a cooling of the wall surface solely in specific regions of the casing pipe on account of the direct contact between the surface area of the cooling module and the inner surface of the casing pipe. At the locations where there is contact between the cooling module and casing pipe or at which the cooling module is positioned on the inside, therefore, heat can be discharged in a directed manner, in particular heat from a superconductive component which is connected indirectly or directly to the zone of the casing pipe of the heat pipe or cold pipe. The functioning of the heat pipe (cold pipe) is based on the fact that the refrigerant which is enclosed hermetically in the cold pipe, and which according to one aspect is a liquefied gas or gas mixture suitable for cryotechnology, evaporates upon the supply of heat and is reliquefied on the cooled condensation element. The refrigerant which evaporates on warmer regions inside the heat pipe extracts heat from the corresponding zone via the evaporation heat or evaporation enthalpy, with the result that the cooling action is achieved in the region of the cooling modules. In the case of a constant pressure of the refrigerant, the temperature of the refrigerant (boiling temperature) also remains constant during phase transition. It will be appreciated that, in order to operate a heat pipe or cold pipe, the condensation element has to be coupled thermally to a cryocooler, in order to cool the condensation element to a temperature at which gaseous/liquid phase transition takes place for the reliquefaction of the refrigerant.
• In one exemplary embodiment, the conducting means in the cooling module is provided with passage slots which open to the inside of the surface area, in order to achieve a directed action upon the surface area by the liquid refrigerant dropping off at the condensation element. According to one aspect, the conducting means is designed as a cone or so as to be generally funnel-shaped, and it widens from the condensation element in the direction of the surface area. It will be appreciated that each cooling module will normally be at a specific distance from the condensation element.
• In order to restrict the cooling action of the casing pipe to a specific zone in a directed manner, according to one aspect the cooling module is provided on the evaporation element side with a conducting element in order to lead condensed and/or liquid heat transfer medium away from the surface area again. The conducting element may likewise be designed as a cone or so as to be generally funnel-shaped. According to another exemplary embodiment, the conducting element may have a sieve-like wall, consist of a perforated plate or be produced from a perforated plate. The clearances in the sieve or in the perforated plate serve for causing still liquid refrigerant to drop off on the conducting element, in order to supply it to a further cooling module or to the evaporation element at the lower pipe end of the heat pipe. Alternatively, the conducting element may be provided with run-off slots.
• So that a cold pipe according to invention can be manufactured at a relatively low outlay, according to one aspect the cooling module, together with the conducting means, surface area and conducting element, consists of metal, in particular sheet metal, such as steel, sheet steel, copper, copper alloy or sheet copper. The cooling module can then be produced by sheet forming, if appropriate without weld seams or the like. To mount a cooling module inside the casing pipe, the mounting operation is carried out by means of a shrinkage operation, to be precise by the cooling of the cooling module and/or the simultaneous heating of said casing pipe, so that, especially also at the cryogenic temperatures, a reliable positioning of the cooling modules and, at the same time, reliable contacting between the surface area of the cooling module and the inner surface of the casing pipe are ensured.
• According to another exemplary embodiment, the cryogenic refrigerant (heat transfer medium) may consist of a mixture of at least two refrigerants having different condensation temperatures, such as, for example, a helium/nitrogen mixture (n-H₂) or nitrogen/oxygen mixture suitable for cryotechnology. Alternatively, the refrigerant may consist of a liquefied pure substance gas or an isotope thereof, in particular⁴He (liquid helium I),³He, neon, hydrogen or nitrogen (N₂). The advantage of a polyphase refrigerant is that this refrigerant does not have an exact boiling point, but, instead, a boiling range. The thermodynamic equilibrium can then be shifted to the higher-boiling component of the liquid phase, thus bringing about an increase in the boiling point. When a corresponding liquefied heat transfer medium (refrigerant) is heated, phase transition commences when the temperature reaches the boiling temperature of that mixture constituent which has the lower boiling point. Since the particles of this constituent change over to the gas phase to an increased extent, the composition of the mixture changes locally, with the result that the boiling point also changes, until the boiling point of the other component is reached. At the same time, the selected pressure in the heat pipe can be higher or lower in the adaptation to the requirements, so that a fine tuning of the cooling range can thereby also be carried out.
• In a particularly exemplary embodiment, that side of the condensation element which faces the chamber has a prism-like surface with drop-off tips, the drop-off tips lying in alignment with the passage slots in the cooling module in the mounted state. This measure, too, serves for the directed supply of the refrigerant liquefied at the condensation element to the conical conducting means of the cooling module and to the passage slots formed there, when the cold pipe is used, standing essentially vertically, and the circulation of the refrigerant takes place as a consequence of gravity. The surfaces of the prisms may also be designed as lamellae in order to enlarge the heat exchange surface. The lamellae in this case stand perpendicularly to the surface, and the tips of the prisms are formed by the lamellae, that is to say the prisms constitute an overstructure.
• In order to bring about the circulation of the refrigerant between the cooling modules and the condensation element or between the evaporation element at the lower pipe end and the condensation element at the upper pipe end purely passively by means of gravitational forces, according to one aspect a shaft is installed which leads from the evaporation element to the condensation element and is laid concentrically to the mid-axis and which, in particular, may be formed by means of a hollow pipe. Gaseous refrigerant can then rise, unimpeded, through the cavity of the shaft or shaft pipe to the condensation element.
• A heat pipe according to the invention may have only a single cooling module in the chamber. In the preferred embodiment, however, a plurality of cooling modules are installed in the chamber, so that, by means of one cold pipe, where appropriate, a plurality of superconductive components arranged outside the cold pipe can be cooled to the operating temperature necessary for superconductivity. In the case of a plurality of cooling modules in the chamber, the effect additionally arises whereby each cooling module forms a zone, between which and the condensation element the refrigerant circulates until the zone is cooled to the desired cryogenic temperature level (ideally, for example, about 27 K or 33 K), since only then does liquid refrigerant pass through the perforated plate of the conducting element to the cooling module of the next zone. When a cooling module has reached the temperature level, an approximately constant temperature profile is established between the condensation element and this cooling module, with the result that the condensation zone also increases in size. At the start, the refrigerant will evaporate as far as possible completely in a lower-lying zone, along with a high discharge of heat. However, on account of the extended condensation zone, this vapor can also condense again, on the cooling module lying above it, into wet vapor or drops, without the vapor having to rise as far as the condensation element. Even in the case of a plurality of cooling modules, a shaft is provided, for which purpose the cooling modules have centrally a leadthrough for a shaft or a hollow shaft pipe. In order to ensure that refrigerant evaporating on the individual cooling modules can rise to the condensation element, the shaft for each cooling module may have at least one radial orifice, above which the conducting means bears sealingly against the hollow pipe.
• The central hollow pipe or shaft pipe may be connected to the plurality of cooling modules, in turn, by means of a shrinkage process, in which case, when a heat pipe with a plurality of cooling modules is being manufactured, all the cooling modules are first fastened to the hollow pipe, and then this unit is introduced into the casing pipe, again by means of a shrinkage process. Alternatively, a combination of a shrinkage process with soldering may also be carried out.
• According to a further exemplary embodiment according to the invention, the casing pipe may be of ring-shaped design and have an inner ring jacket and an outer ring jacket, the cooling module bearing with its surface area against the inner surface of the inner ring jacket or against the inner surface of the outer ring jacket, depending on the positioning of the component to be cooled. The superconductive structural element to be cooled, such as, in particular, a superconductive coil, is expediently positioned on the ring jacket, against the inner surface of which the surface areas of the cooling module or cooling modules come to bear. A ring-shaped heat pipe is suitable especially advantageously for the cooling of large superconductor coils, that is to say coils having large inside diameters. The coils and, correspondingly, the heat pipe may be designed so as to be rotationally symmetrical about a central axis or else may also be of elliptic, oval or racetrack-shaped design. In such embodiments of the heat pipe, a ring-shaped shaft may be formed between the cooling module or cooling modules and that ring jacket, against the inner surface of which the surface areas of the cooling module or cooling modules do not come to bear. The conducting means and the conducting elements are then correspondingly oriented obliquely in such a way that the conducting means guide condensed heat transfer medium to the surface area on which the coil to be cooled is positioned, and the conducting elements lead the heat transfer medium away from the surface area again. Further, if the coil is positioned on the inner jacket of the ring-shaped heat pipe, a thermal insulation may be installed in the center of the component to be cooled, in order to generate a hot bore at the center of the coil. So that even long superconductor coils or superconductor elements can be cooled uniformly, a heat distribution element, in particular a copper pipe, may be arranged additionally between the component to be cooled and the ring jacket.
• The abovementioned object is also achieved by means of a cooling device for cryotechnology for the cooling of superconductor components, such as, for example, superconductor coils, in particular HTS coils, which has at least one such heat pipe or cold pipe. The cooling device has a reception pipe, in the inner chamber of which are arranged, according to the invention, a plurality of heat pipes, each with at least one installed cooling module, the condensation elements of which are coupled thermally to a cryocooler and the casing pipes of which are at least partially in contact with the reception pipe. The cooling modules of a plurality of, in one embodiment of all, the heat pipes lie in one common plane, and a superconductive component is positioned in the same plane on the outer circumference of the reception pipe. In order to achieve optimal thermal coupling between the cold pipes and the components to be cooled cryogenically, internal thermal coupler elements may be formed in the inner space of the reception pipe at the same installation height as the cooling modules, and/or an external thermal coupler element, such as, for example, a copper ring, may be formed between the superconductive component and the outer jacket of the reception pipe. By means of a cooling device of this type, for example, not only superconductor coils of large inside diameter can be cooled, but at the same time a high cooling capacity can be achieved on account of the multiplicity of heat pipes or cold pipes. Also, by means of such cold pipes, long combinations of coils can be cooled, since a transport of heat over relatively large structural units is ensured.
• Where a cooling device is concerned, according to one aspect the heat pipes are anchored with their evaporation elements in a common reception base which is designed to be thermally conductive and which is coupled thermally to a heating device. The heating device then makes it possible to prevent a situation where during cooling, when all the cooling modules have cooled the corresponding portion of the casing pipe to the desired temperature and themselves have the cryogenic temperature, liquid refrigerant collecting at the foot of the heat pipe becomes iced up since the additional supply of heat then evaporates the refrigerant, the vapor rising to the condensation element via the shaft due to convection or to a capillary action.
• An advantageous field of use of corresponding cooling devices could be, for example, generators provided with superconductor coils for the conversion of ocean waves or ocean flows into current. Another advantageous application is the cooling of an elongate polysolenoid linear motor or of an elongate and/or large-volume coil of a magnet for current limiters.
• Further advantages and embodiments of the invention will be gathered from the following description of advantageous exemplary embodiments shown in the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 shows a longitudinal section through a heat pipe according to the invention for cryotechnology, partially cut away;
• FIG. 2 shows a side view of an exemplary embodiment of a cooling module for a heat pipe according to the invention;
• FIG. 3 shows in perspective an exemplary embodiment of a condensation element for a heat pipe according to the invention;
• FIG. 4 shows a cooling device with heat pipes according to the invention in a side view;
• FIG. 5 shows diagrammatically a longitudinal section through the cooling device according toFIG. 4, partially cut away;
• FIG. 6 shows a top view of the upper head of the cooling device according toFIGS. 4 and 5; and
• FIG. 7 shows diagrammatically a longitudinal section through a ring-shaped heat pipe according to a further exemplary embodiment for the cooling of large HTS coils.
DETAILED DESCRIPTION
• Referring now to the drawings wherein the showings are for the purpose of illustrating exemplary embodiments of the invention only and not for the purpose of limiting same, the heat pipe or cold pipe for cryotechnology, designated inFIG. 1 as a whole byreference symbol10, has a generallycylindrical casing pipe1 as a connecting pipe, which is closed at its lower end by means of anevaporation plate2, as an evaporation element, and at its upper end by means of acondensation plate3, as a condensation element or condenser element. The connection between the pipe jacket of thecasing pipe1, thecondensation plate2 and theevaporation plate3 is made in such a way that a chamber4 encapsulated hermetically with respect to the surroundings is obtained inside thecasing pipe1. So that the heat pipe orcold pipe10 shown inFIG. 1 can be used for cryotechnology, that is to say for a temperature range below about −150° C., the chamber4 is filled with a suitable cryogenic refrigerant, not illustrated, as a heat transfer medium, such as, in particular,⁴He with a boiling point of about 4.23 K (Kelvin) at 1.013 bar, n-H₂with a boiling point of about 20.4 K or N₂with a boiling point of about 77.35 K. The cryogenic refrigerant may also consist of another liquid pure substance gas or gas mixture. To operate theheat pipe10, thecondensation plate3 is connected thermally to a suitable cryocooler, not illustrated, by means of which thecondensation element3 can be cooled to a temperature at which gaseous refrigerant enclosed in the chamber4 changes over to the liquid state of aggregation. The chamber4 is filled with the refrigerant at a pressure which is higher than atmospheric pressure, and theheat pipe10 and all the connections inside theheat pipe10 can withstand high excess pressure. According to one exemplary embodiment, theheat pipe10 is designed for standing installation, in which the mid-axis of thejacket pipe1 stands vertically or assumes a small angle with respect to the perpendicular or vertical of <30°.
• According to the invention, at least one cooling module, designated as a whole by20, which is illustrated in detail inFIG. 2 and which is now first referred to is installed in the chamber4. Thecooling module20 consisting of metal, such as steel or copper or copper alloy, has a markedly smaller axial length than the casing pipe and has a cylindricaltubular surface area21 which has adjoining it upward a first cone orconical element22 which, starting from thetransition23 between thesurface area21 and theconical element22, tapers upward conically or in a funnel-shaped manner. The conical surface, widening toward thesurface area21, of thecone22 forms a conducting means in order to guide liquid or liquefied refrigerant, which falls down from above onto theconical element22 by virtue of the gravitational forces, toward thesurface area21. The conducting action of theconical element22 is reinforced in that a plurality of, for example four to eight conductingslots24 are formed, distributed over the circumference of theconical element22, and extend as far as the margin ortransition23, and make it possible that the liquid refrigerant dropping down from above can pass through the conductingslots24, designed as orifices, to theinner surface21′ (FIG. 1) of thesurface area21, in order to flow off downward there. Theconical element22 issues at the top in a truncated manner into around dome25 which forms a circular orifice for a shaft pipe or hollow pipe5 (FIG. 1) which is positioned concentrically to the axis of thecasing pipe1 of theheat pipe10 and which extends essentially over the entire height of theheat pipe10. Thesurface area21 has adjoining it downward a secondconical element26 which, in the exemplary embodiment shown, is produced from a sieve plate or the like, has numerous sieve holes27 and tapers conically from the lowercylindrical margin28 of the surface area toward the mid-axis. The secondconical element26, too, ends in a truncated manner in a throughbore29 for the passage of the hollow pipe orshaft pipe5. The clearances or holes27 in the sieve plate of theconical element26 serve for conducting still liquid refrigerant away or further on downward, so that liquid refrigerant cannot build up inside anindividual cooling module20. Thecone22 forming the conducting means has essentially the same dimensions as the cone forming the conducting element, but is oriented conversely, in order to achieve an inflow of liquid refrigerant to thecasing pipe1 or a flow away towards the axis and at the same time to guide a stream of gaseous refrigerant inside the cones toward the mid-axis.
• In aheat pipe10 according to the invention, at least onecorresponding cooling module20 is arranged between theevaporation plate2 closing the lower pipe end of thecasing pipe1 and thecondensation plate3 closing the upper pipe end and is inserted into the chamber4 in such a way that thesurface area21 bears areally with its outside all around against theinner surface1′ of thejacket pipe1. According to one aspect, a real bearing contact is brought about by means of a press fit which is achieved as a result of a shrinkage of thecooling module20 into thejacket pipe1, in that, for example, for the shrinkage process thejacket pipe1 is heated and at the same time thecooling module20 is cooled in order to cause thecooling module20 andcasing pipe1 to be joined together as a result of contraction or expansion.
• What is achieved by thecooling module20 installed in theheat pipe10 is that liquid refrigerant is routed in a directed manner onto thesurface area21 of each coolingmodule20, with the result that heat can be discharged at thecasing pipe1 into that region in which thecooling module20 bears with itssurface area21 against theinner surface1′ of the casing pipe. A superconductive structural element, such as, for example, a superconductive coil, can therefore be positioned on the outer circumference of thejacket pipe1 of the heat pipe orcold pipe10, in a region which lies in alignment with the surface area of thecooling module20, with the result that a liquid refrigerant supplied to this contact zone inside the chamber4 of theheat pipe10 can discharge heat in a directed manner and effectively from the superconductor components or superconductive coils, so that these are operated below the transition temperatures of the superconductive material. In this case, for heat discharge, the evaporation enthalpy of the refrigerant is utilized, which the refrigerant requires upon phase transition between the liquid and gaseous states of aggregation. Installing thecooling modules20 in thecold pipe10 has the particular effect that the maximum cooling capacity is provided in a limited manner, within the shortest possible time, in that region in which superconductive structural elements are positioned on the outer circumference of the heat pipe.
• In order to allow an optimal circulation of the refrigerant inside the chamber4 in the heat pipe orcold pipe10, thehollow pipe5 forming the shaft has, essentially directly below thedome25 of the upperconical element22 having thepassage slots24, radial passages6 of sufficient size, through which refrigerant which has changed over to the gaseous state of aggregation inside acooling module20 can flow over into theinner pipe7 of theshaft pipe5 and be supplied from there in gaseous form to thecondensation plate3 cooled by means of the cryocooler. This, too, is assisted by the generally funnel shape or generally conical shape of thecooling module20.
• Admittedly,FIG. 1 shows only onecooling module20 inside the chamber4 of thecold pipe10. However, a plurality ofidentical cooling modules20 are arranged, if appropriate distributed uniformly, over the height of thecold pipe10, liquid refrigerant dropping down from thecondensation plate3 only onto thecooling module20 uppermost inside the chamber4 and directly adjacent to thecondensation element3, while liquid refrigerant drops down onto the conducting means orconical elements22 of the following cooling modules and passes through theholes27 in the lowerconical element26. Theevaporation plate2 at the lower end of theheat pipe10 comes into play when thelowest cooling module20 inside the chamber4 also allows still liquid refrigerant to pass through downward. In order to prevent an accumulation of liquid refrigerant at the foot or bottom of thecold pipe10, theevaporation plate2 may be coupled thermally to a heating device or the like which prevents the liquid refrigerant from icing up at the foot of thecold pipe10. The refrigerant which has changed over to the gaseous state of aggregation at theevaporation plate2 can in this case flow over into the shaftinner pipe7 throughradial entrances8 at the foot of thehollow pipe5 and flow over from there to thecondensation plate3. For theradial slots8, it is, where appropriate, sufficient to arrange thefoot portion9 of theshaft pipe5 at a suitable distance from theevaporation plate2 or to support it by means of intermediate webs on said evaporation plate or on thecasing pipe1. Before thecooling modules20 are mounted inside the chamber4 of thecasing pipe1, in one exemplary embodiment all thecooling modules20 are shrunk onto thehollow pipe5 by means of a shrinkage process, before the composite structure comprising theshaft pipe5 andcooling modules20 is inserted as a unit into thecasing pipe1, making use of thermal expansion/shrinkage.
• FIG. 3 shows an exemplary embodiment of acondensation plate3 with as large a surface as possible, in order to maximize the contact area for gaseous refrigerant and at the same time to achieve a directed dropping off or falling down of reliquefied or liquefied refrigerant. For this purpose, thecondensation plate3 has on its underside a prism-like surface13 with a number of drop-offtips14 which can correspond to the number ofpassage slots24 in theuppermost cooling module20. Each drop-off tip may have, for example, four planar flanks as prism surfaces. The thermal coupling of thecondensation plate3 to the cold head of a cryocooler may take place, for example, via a copper bar or the like as a thermal bus, or the cold head of a cryocooler may be connected directly to thecondensation plate3 of the heat pipe orcold pipe10.
• FIGS. 4 to 6 show an example of an application of the use of a plurality of cold pipes within a cooling device designated as a whole by100. Eachcold pipe10 has in this case a set-up, such as was described with reference toFIGS. 1 to 3, and eachcold pipe10 has a multiplicity of coolingmodules20 over its height. The individualcold pipes10 are in this case designed in such a way that, in all thecold pipes10, the coolingmodules20 are positioned at the same distance from thecondensation plate3 or the evaporation plate of eachcold pipe10.
• In thecooling device100, overall sixcold pipes10 are arranged at an equal angular spacing on a reference circle about a central axis Z of thecooling device100. The outer surfaces of thecasing pipe1 of eachcold pipe10 can bear directly against areception pipe80 which is positioned concentrically to the central axis Z and which encloses all thecold pipes10 over its entire height. In the inner space of thisreception pipe80, in one exemplary embodiment solely in those regions in which thecooling modules20 are arranged inside thecold pipes10, on each cooling module plane an innerthermal conductor81 is positioned as a thermal coupling element which partially brings about direct thermal contact between the entire outer surface of thecasing pipe1 of theindividual cooling pipes10 and theinner surface area82 of thereception pipe80, in order to achieve the highest possible heat transmission between thereception pipe80 and the coolingpipes10 in that region in which theindividual cooling modules20 are positioned. In the exemplary embodiment shown, outer thermal coupling rings85 are positioned on those regions of theouter jacket83 of thereception pipe80 which lie in alignment with the coolingmodules20 and the innerthermal conductor elements81, ring-shaped superconductor coils90 bearing here with their inner ring against said coupling rings.
• The superconductor coils90 can be cooled to below the transition temperature of the superconductive material by means of therespective cooling modules20 in thecold pipes10. All thecondensation plates3 of the total of sixcold pipes10 here are connected to one another via acoupling ring70, to which thecold head75 of a cryocooler, not illustrated in any more detail, is connected. Thereception pipe80 for thecold pipes10 is positioned, in turn, inside atubular jacket71 which according to one aspect is designed as a cryostatic container. In thecooling device100, all thecold pipes10 are arranged with their lower ends closed by means of the evaporation plates in a reception base72 or are coupled thermally to the latter which is assigned to a heating device, in order to prevent a situation where the refrigerant may freeze inside the individual hermetically encapsulatedcold pipes10.
• FIG. 7 shows an exemplary embodiment of aheat pipe210 for cooling a large andlong superconductor coil290. Theheat pipe210 is designed here to be rotationally symmetric about the central axis Z′ and has a ring-shapedcasing pipe201 with aninner ring jacket261 and with anouter ring jacket262. A ring-shapedcondensation plate203 with drop-offtips214 on its underside is fastened to the upper end of the two ring jackets of thecasing pipe201 and a ring-shaped evaporation plate202 is fastened at the lower end in such a way as to form in the casing pipe201 a hermetically encapsulatedchamber204 which is filled with a suitable cryogenic refrigerant. A plurality of coolingmodules220, only one of which is illustrated here, are installed in the ring-shaped chamber4. Eachcooling module220 bears with acylindrical surface area221 against theinner surface261′ of theinner ring jacket261. Above eachsurface area221 is formed an oblique conducting means222 which runs in the form of a ring around theinner ring jacket261 and which guides liquid or condensed refrigerant to thesurface area221. Below eachsurface area221, thecooling module220 has anoblique conducting wall226 which leads liquid refrigerant away from thesurface area221. The conductingwall226 is provided withsieve holes227 so that refrigerant can drop off downward to a further cooling module or to theevaporation plate204. Between the coolingmodules220 and theouter ring jacket262 is arranged a ring-shapedintermediate wall265, by means of which a ring-shapedshaft207 is formed inside the chamber4 between the coolingmodules220 and theouter ring jacket262. Theintermediate wall265 is spaced apart from thecondensation plate203 and theevaporation plate204, so that liquid and/or gaseous refrigerant can flow over into that part of thechamber204 in which the cooling modules are arranged. The drop-offtips214 on thecondensation plate203 lie correspondingly radially within theintermediate wall265. Theintermediate wall265 is provided withpassages206 directly below the contact point between the conductingring222, running obliquely upward here at about 45°, and its contact point with theintermediate wall265, so that evaporating refrigerant can rise upward inside the coolingmodules220 via the shaft to thecondensation plate203. In the exemplary embodiment shown, thesuperconductor coil290 to be cooled is positioned inside theinner pipe jacket261. In order to achieve good heat conduction between the coolingmodules220 and thecoil290 to be cooled, thermal coupling rings281 are arranged, opposite thesurface areas221, outside thecasing pipe201. Since thecoil290 extends over almost the entire height of theheat pipe210, acopper pipe285 as a heat distribution element bears against the outside of thecoil290 and, in turn, at a plurality of locations is in each case in contact with the coupling rings281.
• A person skilled in the art can gather from the above description numerous modifications which are to come within the scope of protection of the accompanying claims. The figures show only preferred exemplary embodiments, and, in particular, the number of cooling modules in a cold pipe or heat pipe, the number of cold pipes in a refrigerating device and the thermal coupling between a cryocooler and the condensation elements of the individual cold pipes may vary, without departing from the scope of protection of the accompanying claims. Various pure substance gases, gases or gas mixtures which are suitable for cryotechnology or cryogenics may also be used as refrigerant. The superconductive structural elements and components may be fastened directly to the cold pipes or the reception pipe of the cooling device, or indirectly to these, or may be coupled thermally to these. The pipes may additionally be provided with safety valves for excess pressure, pumping-off valves for generating a vacuum and/or access valves for the introduction of cooling media. In the ring-shaped heat pipe, a thermal insulation could be installed in the center of the coil, thus giving rise at the center of the coil to a heat bore. Alternatively, the coil could also bear on the outside of the outer ring jacket. The conducting means and conducting wall of the cooling modules would then be inclined correspondingly obliquely with respect to the outer ring jacket and the surface area would bear against this. The ring-shaped heat pipe could also be of oval or suchlike design. Ducts or gaps could also be formed between the outside of the surface area of the cooling modules and the inner surface in order to allow condensed or liquid heat transfer medium/refrigerant to flow through these ducts or gaps in the region of the cooling modules and then to guide it away from the inner surface again by means of suitable devices, such as drop-off rings, and lead it to the inner surface again only in the region of the following cooling module. In this case, the entire heat transfer medium could also flow in each case through only the ducts or gaps.
• It will be appreciated that various of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Also that various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.

Claims (20)

1. A heat pipe for cryotechnology, the heat pipe comprising: a casing pipe and a chamber encapsulated hermetically by a condensation element at one pipe end and by an evaporation element at the other pipe end and filled with heat transfer medium, wherein in the chamber, between the condensation element and the evaporation element, at least one cooling module is installed which partially bears with a tubular surface area against the inner surface of the casing pipe and which is provided at least on the condensation element side with a conducting means in order to guide at least one of condensed and liquid heat transfer medium to the inside of the surface area of the cooling module.

2. The heat pipe as claimed inclaim 1, wherein the conducting means is provided with passage slots which open out to the inside of the surface area, and/or that and the conducting means is designed generally funnel-shaped.

3. The heat pipe as claimed inclaim 1, wherein the cooling module is provided on the evaporation element side with a conducting element in order to lead condensed and/or liquid heat transfer medium away from the surface area, the conducting element being generally funnel-shaped.

4. The heat pipe as claimed inclaim 3, wherein the conducting element is one of designed as a sieve or formed from a perforated plate.

5. The heat pipe as claimed inclaim 3, wherein the conducting element is provided with run-off slots running radially.

6. The heat pipe as claimed inclaim 3, wherein the cooling module, together with the conducting means, surface area and conducting element, consists of sheet metal.

7. The heat pipe as claimed inclaim 1, wherein the cooling module is inserted into the casing pipe by a shrinkage process by at least one of the cooling of the cooling module and the heating of the casing pipe.

8. The heat pipe as claimed inclaim 1, wherein the heat transfer medium is a mixture of at least two refrigerants having different condensation temperatures.

9. The heat pipe as claimed inclaim 1, wherein that side of the condensation element which faces the chamber has one of a prism-like surface with drop-off tips or a prism-like overstructure with drop-off tips, the drop-off tips lying in alignment with passage slots in the cooling module.

10. The heat pipe as claimed inclaim 1, wherein a shaft leads from the evaporation element to the condensation element and is laid concentrically to the mid-axis and is formed by a hollow pipe.

11. The heat pipe as claimed inclaim 1, wherein a plurality of cooling modules are installed in the chamber.

12. The heat pipe as claimed inclaim 11, wherein the cooling modules have centrally a leadthrough for a shaft or a hollow pipe, the hollow pipe being provided for each cooling module with at least one radial orifice, above which the conducting means bears against the hollow pipe.

13. The heat pipe as claimed inclaim 1, wherein a superconductive structural element, is positioned on the outer circumference of the casing pipe in the same installation position as the surface area of the cooling module.

14. The heat pipe as claimed inclaim 1, wherein the casing pipe is generally ring-shaped design and has an inner ring jacket and an outer ring jacket, the cooling module bearing with its surface area against one of the inner surface of the inner ring jacket or against the inner surface of the outer ring jacket.

15. The heat pipe as claimed inclaim 14, wherein a superconductive structural element to be cooled is positioned on the inner ring jacket against the inner surface of the inner ring jacket of which the surface areas of the cooling module comes to bear.

16. The heat pipe as claimed inclaim 14, wherein a ring-shaped shaft is formed between the cooling module and the outer ring jacket, against the inner surface of the outer ring jacket of which the surface areas of the cooling module does not come to bear.

17. The heat pipe as claimed inclaim 14, wherein a thermal insulation for achieving a hot bore is installed in the center of a component to be cooled, and a heat distribution element is arranged between the component to be cooled and the inner ring jacket.

18. A cooling device for cryotechnology for the cooling of superconductor components or superconductor coils with at least one heat pipe, the cooling device comprising: a reception pipe, in the inner space of which the reception pipe are arranged a plurality of heat pipes, condensation elements of the heat pipes are coupled thermally to a cryocooler and casing pipes of the cryocooler are at least partially in contact with the reception pipe, cooling modules of a plurality of the heat pipes lying in one common plane, and a superconductive component being positioned in the same plane on the outer circumference of the reception pipe.

19. The cooling device as claimed inclaim 18, wherein internal thermal conducting elements are formed in the inner space of the reception pipe at the same installation height as the cooling modules, and an external thermal conductor is formed between the superconductive component and the outer circumference of the reception pipe.

20. The cooling device as claimed inclaim 18, wherein the heat pipes are anchored with their evaporation elements in a common reception base which thermally conductive and which is coupled thermally to a heating device.

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