CN1837721A - Apparatus and method for maintaining a system at a cryogenic temperature over an extended period of time without active refrigeration - Google Patents

Apparatus and method for maintaining a system at a cryogenic temperature over an extended period of time without active refrigeration Download PDF

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Publication number
CN1837721A
CN1837721A CN200610067682.3A CN200610067682A CN1837721A CN 1837721 A CN1837721 A CN 1837721A CN 200610067682 A CN200610067682 A CN 200610067682A CN 1837721 A CN1837721 A CN 1837721A
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China
Prior art keywords
refrigerant
temperature
calorifics
battery
tank body
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CN200610067682.3A
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Chinese (zh)
Inventor
A·F·阿特金斯
G·吉尔格拉斯
W·斯陶特纳
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Siemens PLC
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Siemens Magnet Technology Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F6/00—Superconducting magnets; Superconducting coils
    • H01F6/04—Cooling
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
    • F17C3/00—Vessels not under pressure
    • F17C3/02—Vessels not under pressure with provision for thermal insulation
    • F17C3/08—Vessels not under pressure with provision for thermal insulation by vacuum spaces, e.g. Dewar flask
    • F17C3/085—Cryostats
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
    • F17C13/00—Details of vessels or of the filling or discharging of vessels
    • F17C13/005—Details of vessels or of the filling or discharging of vessels for medium-size and small storage vessels not under pressure
    • F17C13/006—Details of vessels or of the filling or discharging of vessels for medium-size and small storage vessels not under pressure for Dewar vessels or cryostats
    • F17C13/007—Details of vessels or of the filling or discharging of vessels for medium-size and small storage vessels not under pressure for Dewar vessels or cryostats used for superconducting phenomena
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
    • F17C2203/00—Vessel construction, in particular walls or details thereof
    • F17C2203/06—Materials for walls or layers thereof; Properties or structures of walls or their materials
    • F17C2203/0602—Wall structures; Special features thereof
    • F17C2203/0612—Wall structures
    • F17C2203/0626—Multiple walls
    • F17C2203/0629—Two walls
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
    • F17C2205/00—Vessel construction, in particular mounting arrangements, attachments or identifications means
    • F17C2205/01—Mounting arrangements
    • F17C2205/0123—Mounting arrangements characterised by number of vessels
    • F17C2205/013—Two or more vessels
    • F17C2205/0149—Vessel mounted inside another one
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
    • F17C2205/00—Vessel construction, in particular mounting arrangements, attachments or identifications means
    • F17C2205/01—Mounting arrangements
    • F17C2205/0153—Details of mounting arrangements
    • F17C2205/0157—Details of mounting arrangements for transport
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
    • F17C2221/00—Handled fluid, in particular type of fluid
    • F17C2221/01—Pure fluids
    • F17C2221/014—Nitrogen
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
    • F17C2221/00—Handled fluid, in particular type of fluid
    • F17C2221/01—Pure fluids
    • F17C2221/016—Noble gases (Ar, Kr, Xe)
    • F17C2221/017—Helium
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
    • F17C2223/00—Handled fluid before transfer, i.e. state of fluid when stored in the vessel or before transfer from the vessel
    • F17C2223/01—Handled fluid before transfer, i.e. state of fluid when stored in the vessel or before transfer from the vessel characterised by the phase
    • F17C2223/0146—Two-phase
    • F17C2223/0153—Liquefied gas, e.g. LPG, GPL
    • F17C2223/0161—Liquefied gas, e.g. LPG, GPL cryogenic, e.g. LNG, GNL, PLNG
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
    • F17C2223/00—Handled fluid before transfer, i.e. state of fluid when stored in the vessel or before transfer from the vessel
    • F17C2223/03—Handled fluid before transfer, i.e. state of fluid when stored in the vessel or before transfer from the vessel characterised by the pressure level
    • F17C2223/033—Small pressure, e.g. for liquefied gas
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
    • F17C2270/00—Applications
    • F17C2270/05—Applications for industrial use
    • F17C2270/0527—Superconductors
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
    • F17C2270/00—Applications
    • F17C2270/05—Applications for industrial use
    • F17C2270/0527—Superconductors
    • F17C2270/0536—Magnetic resonance imaging

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Power Engineering (AREA)
  • Containers, Films, And Cooling For Superconductive Devices (AREA)
  • Magnetic Resonance Imaging Apparatus (AREA)

Abstract

A cryogenic thermal battery arrangement for maintaining a superconducting magnet coil or similar apparatus at a cryogenic temperature for a required shipping period, such as thirty days, without consuming a significant amount of a costly working cryogen is disclosed. The present invention allows extended shipping periods without incurring excessive costs.

Description

At the method and apparatus that does not have long-term maintenance equipment low temperature under the situation of active refrigeration
Technical field
Present invention relates in general to a kind of calorifics battery, that is, and at the device that does not have to be used under extraneous refrigeration and the ambient temperature condition with higher device remained under the specified temp.
Background technology
Superconducting magnet is known, and it is used for forming very strong magnetic field in the application scenario of for example magnetic resonance imaging.Superconducting magnet is formed by a large amount of superconducting coils usually, in use, must remain on the cryogenic temperature that the order of magnitude is generally 4K, i.e. the boiling point of liquid helium.In addition, it also is known using the system of so-called high-temperature superconductor.These systems work under the temperature of neon, hydrogen or the nitrogen of boiling.For these materials, has the critical-temperature that scope is 18-80K usually.Although the present invention is described in particular with reference to the system of working under about 4K, wherein the helium by boiling cools off, and the present invention also can be applicable in the high-temperature superconducting device.
In typical devices, superconducting coil is immersed in liquid cryogen for example in the bath of liquid helium.Making liquid refrigerant boiling, and superconducting coil is remained on the steady temperature of refrigerant boiling point, is about 4K for liquid helium.Also be provided with condensation refrigerating plant again, and cold is provided, so that make the refrigerant vapor of evaporation be condensed into liquid state again.Like this, the wastage in bulk or weight of liquid cryogen can be reduced to a lower numerical value, this be because, even the refrigerant of not every evaporation, the refrigerant of the evaporation of the overwhelming majority by condensation again so that turn back to liquid state in the cryogen vessel.Certainly, can also use other refrigerant except liquid helium, this depends on required cryogenic temperature.
Fig. 1 shows and is used for being generally the bobbin 10 that the tubular superconducting magnet of helical makes and being installed in the sectional view of the superconducting coil 12 on the bobbin of MRI (magnetic resonance imaging) or NMR (Magnetic resonance imaging) imaging system.Bobbin 10 and superconducting coil 12 are contained in the cryogen vessel 14.Cryogen vessel 14 partly is filled with liquid cryogen usually, and is not shown in the drawings.Cryogen vessel itself is contained in the outer vacuum chamber 16, and the space between cryogen vessel 14 and outer vacuum chamber 16 is evacuated.In the space that is evacuated between cryogen vessel 14 and outer vacuum chamber 16, also be provided with heat shield piece 18 usually.This heat shield piece has reduced to shine the heat radiation from outer vacuum chamber on the cryogen vessel.Usually also comprise maintenance neck 20.At work, this maintenance neck can hold condensation refrigerating plant again.
When this system transportation and etc. when to be installed, a problem appears.Usually, this system betransported with the form that fills liquid refrigerant, but owing to does not have suitable power supply or because regulation limitations, the condensation refrigerating plant can not be worked again.In transportation, refrigerant may seethe with excitement, and this makes superconducting coil 12 remain on required low temperature.Therefore this refrigerant is as calorifics battery (thermal battery).Maintenance neck 20 provides the refrigerant of evaporation to leave the escape path of cryogen vessel 14.The refrigerant of evaporation may be dispersed in the atmosphere.Reaching in about 30 days time, this system needs to keep the calorifics battery status of this boiling.When the refrigerant of for example helium or neon was used, the refrigerant expense that causes owing to boiling was very large.When hydrogen was used as refrigerant, there was the risk of blast in helium.
Superconducting coil need be remained on low temperature, this is because if not like this, and the expense of the installation of this system increases, problem increases and time-consuming.If this is heated to ambient temperature, this situation can appear if the liquid cryogen boiling exhausts, and this system must be cooled before starting and fill expensive liquid cryogen again like this.Other zone in the whole world, if there is not forethought to arrive this situation, it is very difficult obtaining the required a large amount of liquid cryogen supplies of this operation.This cooling again also is time-consuming with filling again, and considers that the field engineer spends at the scene in the time of system's installation and the material cost that uses refrigerant, and expense may be very high.
In magnet system as shown in Figure 1, the volume of cryogen vessel 14 is roughly limited by the shortest permissible haulage time.In order to satisfy the idle haulage time of after-condenser promptly 30 days, in this system, must accommodate the bigger liquid cryogen of volume, so that guarantee that refrigerant does not exhaust in transportation.The influence when determining the final size of whole system of required refrigerant storage volume is bigger.
Summary of the invention
The invention solves some problems that exist in the prior art, a kind of low temperature calorifics cell apparatus that for example is used for superconducting magnet coil or similar device are remained on low temperature in required haulage time section in 30 days and under the situation that does not consume mass expensive refrigerant is provided.By the present invention, also can under not overspending condition of cost, prolong haulage time.
Therefore, the invention provides device and/or the method that limits by accompanying Claim.
The invention provides a kind of in time period that prolongs for example in 30 days and do not having system to be remained on low temperature and reduce for example method and apparatus of the consumption of liquid helium of expensive refrigerant under the situation of active refrigeration.
According to the present invention, second refrigerant that is different from work refrigerant is arranged in the tank body, and with the system's thermally coupled that is cooled.When this magnet system of being applied to as shown in Figure 1, this tank body can be arranged to and bobbin 10 thermally coupleds, and can realize thermally coupled with superconducting coil 12 by this bobbin, for example shown in the Reference numeral 22 of Fig. 2.
The material of second refrigerant is chosen to not expensive, that can re-use and spends low in transit.Therefore it is preferably as normally used refrigerant.
The tank body that contains second refrigerant is preferably the refrigerant primary tank of being arranged to being used to hold work refrigerant 14 to be separated.This has prevented the pollution of the work refrigerant that second refrigerant causes.This pollution is disadvantageous, and may be risky.It is solid-state that this second refrigerant is preferably under running temperature, and its boiling point is higher than the boiling point of work refrigerant.Use the common system of cooling off by helium as example, thereby work cryogen vessel 14 can remain on about 4K by the helium boiling.In tank body of the present invention, accommodate for example second refrigerant of solid nitrogen.In course of normal operation, the helium boiling is so that arrive about 4K with this system cools; Again the condensation refrigerating plant make evaporation the helium steam again condensation get back to liquid form, and second refrigerant keeps solid-state and inoperative in cooling.
In transportation, work refrigerant (promptly be helium in this example) so that system cools is arrived its boiling point, is about 4K as the first calorifics battery and boiling for helium.In special time period, this work refrigerant exhausts boiling.The temperature of this system will raise.Prior art system that Here it is is heated to the stage of ambient temperature, this before installing, needing to cause expensive, time-consuming, be the cooling again of difficulty sometimes.Yet according to an aspect of of the present present invention, in case this system is heated to specified temp, although this temperature also is a cryogenic temperature, second refrigerant in tank body undergoes phase transition beginning.For be in the second solid-state refrigerant under the work refrigerant temperature for, its solid-state beginning is melted.Such thawing makes melts latent heat from absorbing on every side, thereby cools off this system.Like this, second refrigerant is as the second calorifics battery.In case second refrigerant melts, the temperature of this system will raise once more.In case this system is heated to specified temp, although this temperature also is a cryogenic temperature, second refrigerant in tank body will undergo phase transition once more.In this example, liquid second refrigerant comes to life.Such boiling makes from absorbing evaporation latent heat on every side, thereby cools off this system.This means the second calorifics battery effect of second refrigerant.In case the boiling of second refrigerant exhausts, this system will be heated to ambient temperature.Yet, be arranged on the thing quality and quantity of second refrigerant in the system by careful selection, thereby postpone the heating of this terminal stage, so that realize useful haulage time.Because second refrigerant needn't remain under system's running temperature in this system, therefore can adopt not expensive refrigerant as second refrigerant.
Cost for the work refrigerant that reduces consumption makes its volume in system minimize.This can realize that perhaps at least a portion in this work refrigerant can reclaim by the initial fill of this system of careful control from cryostat before transportation.
Advantageously, postpone this final cooling stage, exhaust up to all or nearly all second refrigerant boiling.Perhaps, the recovery that any remaining second refrigerant can be from cryostat.This has been avoided consuming work refrigerant when second refrigerant of cooling surplus.At second refrigerant is that nitrogen, work refrigerant are in the example of helium, and the nitrogen of designated volume is cooled to 4K from 7 7K, and this needs the helium of double volume, and avoids occurring this situation in order to reduce the consumption of helium, to be preferably.
If any second refrigerant is retained in the cryostat, in case it is cooled to running temperature, then it can not take away any additional thermic load, and only is to keep curdled appearance not participate in the sub-cooled process under running temperature.Yet, making that preferably the quality that is retained in second refrigerant in the cryostat minimizes, this is because second refrigerant means the extra heat quality that need be cooled to running temperature, thereby causes the consumption of unnecessary work refrigerant.
The example of the second possible refrigerant includes but not limited to, nitrogen, neon, hydrogen, oxygen.Nitrogen is attractive as the material as second refrigerant.Nitrogen is not expensive, and a large amount of the existence.It is not easy to blast and also is not easy to burning.Nitrogen has following with the useful physical characteristic of describing.
Find that nitrogen absorbs stable latent heat when temperature 35K, 70K, 77K.Because nitrogen can be Duoed once phase transformation than most refrigerant, so nitrogen is effective refrigerant in should be with occasion.Volume in the solid nitrogen of the following extra fine quality of 35K is approximately little by 0.8% than its liquid volume.
When temperature was elevated to 35K, solid-state-solid-state phase changes took place in solid nitrogen, thereby absorbed latent heat.When 70K, nitrogen is melted into liquid, thereby absorbs latent heat once more.Under atmospheric pressure nitrogen seethes with excitement when 77K, thereby absorbs latent heat once more.More than temperature 77K, and under atmospheric pressure, nitrogen is gaseous state.
When solid nitrogen is used as second refrigerant, can be before its boiling from absorbing most heat on every side.With other alternative material for example hydrogen, neon or oxygen compare, the specific heat capacity of nitrogen is bigger.
If system of the present invention is cooled off as second refrigerant by nitrogen, after work refrigerant evaporates, this system can become warm to a temperature in these transition temperatures (35K, 70K, 77K), but with this system is compared from environment temperature (scope is about 300K) cooling, the degree of difficulty that 4K is got back in the temperature cooling of this system from these transition temperatures (35K, 70K, 77K) obviously reduces.Because this system remains on cryogenic temperature by second refrigerant, the refrigerant that therefore not too needs to provide expensive for example liquid helium is used for transportation.Therefore the volume of work cryogen vessel 14 can reduce, and the cost that is used to like this fill also descends, and the overall dimension of system also can reduce.This system can be lighter, and required liquid cryogen also will reduce in tank body.In known system, need to fill 1500 liters liquid helium refrigerant, its weight is 400kg, and current needs are about
Figure A20061006768200091
3300.According to the present invention, suitable system has 100 liters nitrogen when transportation, and its weight is 80kg, so that provide suitable cooling with the material cost of minimum.For example, by the evaporation of 100 liters liquid nitrogen, system can be cooled to running temperature, and the work refrigerant evaporation that needs minimum afterwards is so that be cooled to this system the boiling point of work refrigerant from the boiling point of nitrogen.
Because being heated to 77K nitrogen from 4K needs lot of energy, so nitrogen is effective refrigerant.Calculate with the evaporation latent heat capacity of simplifying, the evaporation latent heat that 10 liters liquid nitrogen absorbs equals the heat of 55 liters helium evaporation absorption.Therefore, can think that effective cooling that the nitrogen of a given quality provides at its boiling point is equivalent to the helium of 5 times equal mass.Certainly, the boiling point of refrigerant is different, and therefore the helium of boiling remains on the temperature of 4K, and the nitrogen of boiling remains on 77K.As mentioned above, nitrogen also has solid-state phase changes except thawing and boiling phase transformation.Nitrogen is heated to helium that the energy that needs on the 77K is equivalent to equal in quality under the 35K in same temperature ranges stated, heats ten times of required energy.Therefore, for identical cooling effect, use the nitrogen of 1/10th volumes to be equivalent to use the calorifics battery of helium as refrigerant.For example, if the liquid helium total amount of 1500 liters of current needs of cryogenic system guaranteeing 30 days haulage time in degree of admission, and provides 150 liters nitrogen that identical haulage time can be provided.Like this, the size of whole system can reduce, and this is because large-sized cryogen vessel 14 needn't be set, and the expense of the transportation of this system and installation also can reduce, and this is because no longer need a large amount of liquid heliums.In another example, the cumulative volume of refrigerant remains unchanged, and the composition of helium is replaced by nitrogen.Provide for the refrigerant volume of cooling in 31 days for being designed to helium boiling, can calculate 1/3rd of helium volume is replaced 20 days transportation cooling can be provided by the helium boiling temperature by nitrogen, provide 120 days cooling with liquid nitrogen or nitrogen boiling temperature subsequently, this haulage time haulage time that existing apparatus provided far away.The shortcoming of this device is that this system temperature when arrival reaches 77K, rather than is having only the helium boiling to carry out the 4K temperature that is reached under the situation of system cools.
In case this system reaches the spot, it is better simply relatively being reduced to 4K from 77K, for example can realize by using on-the-spot closed loop refrigerating plant.The closed loop refrigerating plant only needs about 3 liters helium to fill.The embodiment of closed loop refrigerating plant below will be described.In addition, by with the direct refrigeration that contacts of bobbin 10, perhaps by adding work refrigerant or making it evaporate this system of cooling off.
Description of drawings
Fig. 1 shows bobbin and is installed in the sectional view of the superconducting coil on the bobbin;
Fig. 2 shows another embodiment of the present invention, wherein is provided with the second refrigerant tank body with the bobbin thermo-contact around bobbin;
Fig. 3 shows the sectional view according to an end of the bobbin of another variant embodiment of the present invention;
Fig. 4 shows the sectional view according to an end of the bobbin of a variant embodiment more of the present invention;
Fig. 5 shows the alternative form of the structure of cooling superconducting coil and bobbin; With
Fig. 6 shows according to embodiments of the invention and uses nitrogen to obtain temperature curve as second refrigerant.
The specific embodiment
Below will describe the specific embodiment of cryostat of the present invention in detail.
In simple embodiment of the present invention, do not change structure shown in Figure 1.Low second refrigerant, for example nitrogen of being filled with of cryogen vessel 14 parts.This can realize by filling liquid nitrogen, thereby perhaps realizes by making corresponding condensation refrigerating plant work again cool to liquid nitrogen temperature and making cryogen vessel and suitable nitrogen supply source connect.In case the second volume required refrigerant is doubly introduced, then introduce volume required work refrigerant, for example helium.This system remains on running temperature by the relevant refrigerating plant of condensation more this moment.It is solid-state that second refrigerant keeps in cryogen vessel, and do not play active role aspect the running temperature in that this system is remained on.
If the condensation refrigerating plant is shut down for a certain reason again, for example because this system shuts down in transit, work refrigerant will evaporate, so that cool off this system.If the boiling of work refrigerant exhausts, second refrigerant will begin to melt, boiling subsequently, thus the boiling point with second refrigerant provides sub-cooled in the time period that prolongs.
Fig. 2 shows another embodiment of the present invention.Be provided with the second refrigerant tank body 22 around bobbin 10, and with the bobbin thermo-contact.By above-mentioned method, this tank body is filled with second refrigerant through going into mouth neck portion 24.It is similar to the aforementioned embodiment to use this tank body to cool off this system, but second refrigerant keeps and the bobbin thermo-contact by the second refrigerant tank body 22, thereby effective cooling of superconducting coil 12 is provided.Be arranged so that second refrigerant and the work refrigerant of the second refrigerant tank body 22 keep separating, and avoid work refrigerant to be polluted by second refrigerant.When emptying, the second refrigerant tank body 22 is as the discharge opeing volume.This makes the work refrigerant that can obtain to be arranged on the given depth in the cryogen vessel with the corresponding refrigerant volume that reduces, and perhaps with another form, the refrigerant of conventional volume is introduced in the container, with darker degree of depth submergence superconducting magnet assembly.It is more most of by being cooled with contacting of liquid cryogen that this has guaranteed superconducting magnet, thereby more constant cooling is provided.
Tank body 22 can be filled by following method.The inlet of tank body 22 is connected with suitable nitrogen supply source.Bobbin 10 is cooled off by the refrigerating plant with any known structure.This cooling can make the wall of tank body 22 be cooled to be lower than the boiling point of nitrogen.Nitrogen begins condensation in tank body.The vacuum that forms owing to the nitrogen condensation makes more nitrogen be inhaled in the tank body.Therefore, nitrogen calorifics battery itself is to fill automatically: when tank body was cooled, nitrogen liquefied with after coagulation, and this makes and sucks more nitrogen.
Fig. 3 shows the details of an end of bobbin, and this is another variant embodiment of the present invention.In this embodiment, in order to realize and the good thermo-contact of superconducting coil 12 that tank body 32 is arranged to the part of the whole of bobbin.As shown in the figure, tank body is annular, and coaxial with bobbin 10, and tank body is located to be soldered to or to be welded on the bobbin in position.Tank body 32 can fill by the tank body 22 described methods of reference Fig. 2.
Fig. 4 shows the details of an end of bobbin, and this is another variant embodiment of the present invention.In this embodiment, in order to realize the good thermal efficiency of this system, tank body 42 is arranged to the form of heat shield piece, but also keeps thermo-contact with bobbin.As shown in the figure, tank body is a cylindricality, and coaxial with bobbin 10, and tank body is located to be soldered to or to be welded on the bobbin in position.By making tank body 42 manufacture complete cylinder (full cyliner) around the axis of superconducting magnet, be attached on the bobbin 10 in each end, because tank body 42 has shielded the heat radiation of incident at least a portion of superconducting coil 12 and bobbin 10, therefore reduced the thermic load that acts on the bobbin 10 that is cooled.If nitrogen is as second refrigerant, tank body 42 should be preferably made of aluminum, and this is that this is favourable in the present invention because aluminium has thermal radiation property at low temperatures.Tank body 42 can fill by the described similarity method of reference Fig. 2.
Superconducting coil 12 and bobbin 10 can be included in the cryogen vessel as illustrated in fig. 1 and 2 and be cooled.Yet Fig. 5 shows the alternative form of the structure of cooling superconducting coil 12 and bobbin 10, and Fig. 5 shows the closed loop refrigeration, but itself does not illustrate embodiments of the invention.
In its simplest form, the closed loop refrigerating plant can comprise the loop of the pipe of being made by Heat Conduction Material, and its end is connected with condensation refrigerating plant again.The condensation refrigerating plant should be arranged on the top of this loop again.The object thermo-contact that pipe is arranged to and is cooled, and be filled with liquid cryogen at least in part.Heat is absorbed via tube material and makes the refrigerant of part seethe with excitement.The refrigerant gas of evaporation upwards flow to condensation refrigerating plant again.Again condensation refrigerating plant cooling refrigerant gas and make its again condensation get back to liquid state, liquid cryogen returns through pipe.By the refrigerating plant of condensation again and the pipe ring road of suitable layout, can set up circular flow around loop.As the closed loop system, this structure can arrive apparatus cools the boiling point of employed refrigerant, and the not consumption of cryogen that is in operation, and only needs a spot of filled refrigerant.
Thereby should be cooled to running temperature by initiatively cooling off according to second refrigerant provided by the invention, for example use the closed loop refrigeration system to realize.The replacement scheme that makes second refrigerant be cooled to running temperature by adding work refrigerant is disadvantageous economically.For example, the amount that adds liquid helium for nitrogen is cooled to 4K may need to double the volume of the nitrogen that is cooled.This can not save cost.
As shown in Figure 5, do not need cryogen vessel 14 or external vacuum cavity 16.Comprise liquid coolant for example the coolant hose 54 of liquid helium be arranged to and bobbin 10 thermo-contacts.Coolant hose can comprise the hoop of one or more annulars, and it locates to be soldered to or to be welded on the bobbin 10 in position.
For the alternative site of cooling tube and other position in the drawings by Reference numeral 54 ' and 54 " represent.Be connected with refrigerating plant so that cool off, and make refrigerant cooling agent these cooling tubes of flowing through, so that form the closed loop refrigeration system.Owing to do not need the refrigerant tank body, the size of whole system can reduce significantly.In this embodiment, the work refrigerant of unique needs is to fill the required refrigerant of cooling tube 54.Certainly, if come work as the calorifics battery under the situation that lacks extraneous refrigeration, then this a spot of work refrigerant can not satisfy any and obviously under the situation this system remained on low temperature for a long time.By this structure is combined with the second refrigerant tank body according to embodiments of the invention, this system can remain on low temperature for a long time.It is particularly advantageous that tank structure shown in Figure 4 is applied to this embodiment, and this is to provide other situation unexistent heat shield piece because rise.
In case the running temperature of being cooled to, superconducting magnet is in the permanent magnetism pattern when work, and superconducting coil cools off by heat conduction or thermal siphon.These two kinds of methods only needing to have realized the closed loop system of a small amount of refrigerant reserves.
Significant advantage of the present invention is, has guaranteed the state of refrigerant system in transportation.As long as in predetermined maximum haulage time, realize transportation, can guarantee that this system is cooled to 77K or lower, under the situation of aspect the cost of equipment or size, not imposed a fine, can make maximum haulage time prolong overrun by the present invention.Necessary is, the work refrigerant that needs to consume specified quantitative for example liquid helium be 4K so that this system is cooled to running temperature from 77K in this example, and still the amount of described liquid helium can be estimated and provide in advance exactly.In prior art system, be cooled in the time of can only wishing to make system's arrival, and need for example fill with about 400 liters helium by helium boiling.If postpone in transit, in fact be in environment temperature during this system arrival, and need initial nitrogen cooling and under operation conditions, add a large amount of liquid heliums.The required erecting bed that is added in of this a large amount of refrigerant is not easy to obtain.
Specific refrigerant for example nitrogen has low heat conductivity when it is solid-state.When this refrigerant was battery operated as calorifics, melted the perimeter of refrigerant, and make before it melts in the other parts that enough heats arrive refrigerant, the perimeter of refrigerant even may seethe with excitement.This may cause the cooling of poor efficiency.On the other hand, the cooling of low rate in the long time period if desired, this effect is favourable.According to specific embodiment of the present invention, thermal conducting path can be arranged in the solid cryogen, so that improve the surperficial contact area of second refrigerant.For example, for example the Reference numeral 32 of Fig. 3 or Fig. 4 are the open-cell material that the second refrigerant tank body of Reference numeral 42 expression can partly fill heat conduction, for example copper cotton (copperwool).This material makes heat loose through second refrigerant row more equably, and makes more uniform heating of second refrigerant, and cools off the system that this is cooled with more constant speed.Similar to the heat abstractor in the electrical equipment, can be in the second refrigerant tank body fin structure be set as an alternative or other form with identical purpose.If the second refrigerant tank body is made by pressing method, for example be formed from aluminium, this is very effective.By the material and the density of this conductive structure, make the speed and the uniformity of the cooling that provides by second refrigerant be adapted to required application scenario.
Fig. 6 shows according to embodiments of the invention and uses nitrogen to obtain temperature curve as second refrigerant.First curve 61 is represented according to embodiments of the invention by the example of nitrogen as the time dependent temperature of superconducting magnet of second refrigerant cooling.As can be seen, because the heat conduction rate variance of second refrigerant when it is solid-state, so the temperature of superconducting magnet can raise above the boiling point of second refrigerant.62 expressions of second curve are by the example of nitrogen as the time dependent temperature of superconducting magnet of second refrigerant cooling, and wherein the refrigerant tank body is identical, but this tank body part is filled with the Heat Conduction Material of perforate, for example the copper cotton.As can be seen from Figure 6, cooling effect is more effective, so that always the temperature of superconducting magnet is remained on below the 77K.This structure is critical wetting; It has avoided being heated to more than the 77K temperature, and has guaranteed that cryostat is stabilized in the nitrogen boiling temperature in the very long time period, in beginning in about 22 days, promptly common haulage time.Certain applications can need special time constant (timeconstant).By Heat Conduction Material suitably is set, thereby change the surface area of solid cryogen effectively in the refrigerant tank body, can obtain the time constant of optimizing for certain applications like this.
Although the present invention describes with reference to a limited number of specific embodiments, for a person skilled in the art, under the situation that does not break away from the scope of the invention that limits by accompanying Claim, can make other modification and change of the present invention.For example, although the present invention describes as second refrigerant in particular with reference to nitrogen, can use other refrigerant.Selected second refrigerant should have higher thermal capacitance when solidifying, and is preferably latent heat thermal capacitance higher when its phase transformation.Selected second refrigerant should not expand when solidifying.If selected second refrigerant expands when solidifying, the tank body that then holds this refrigerant must be flexible so that adapt to the expansion of refrigerant, perhaps must have enough intensity and expand to its applied pressure to bear refrigerant.
Although the present invention describes with reference to a limited number of specific embodiments, for a person skilled in the art, under the situation that does not break away from the scope of the invention that limits by accompanying Claim, can make other modification and change of the present invention.For example, except helium, can use other work refrigerant.Similarly, except nitrogen, can use other second refrigerant.Although the present invention is described in particular with reference to the superconducting magnet that is used for the MRI system, the present invention can be applicable to the cooling of miscellaneous equipment.

Claims (19)

1. calorifics battery that is used in required haulage time section, object (10) being remained on low temperature, this calorifics battery absorbs heat, this calorifics battery comprises first parts and second parts, each parts all with this object thermo-contact,
Described first parts (14; 54) comprise first refrigerant,, be used for this object is remained on first temperature by the boiling of this first refrigerant,
Described second parts (22; 32; 42) thus comprise that the boiling by described work refrigerant remains on second refrigerant of first temperature, this second refrigerant is used for after the boiling of this first refrigerant exhausts this system being remained on second temperature that is higher than first temperature.
2. calorifics battery as claimed in claim 1 is characterized in that, this first temperature is the boiling point of first refrigerant, and this second temperature is the boiling point of second refrigerant.
3. calorifics battery as claimed in claim 1 is characterized in that, this first temperature is the boiling point of first refrigerant, and this second temperature is the melting point of second refrigerant.
4. calorifics battery as claimed in claim 1 is characterized in that, this first temperature is the boiling point of first refrigerant, the solid transformation temperature that this second temperature is second refrigerant.
5. as each the described calorifics battery in the above-mentioned claim, it is characterized in that this calorifics battery comprises the cryogen vessel (14) that is used to keep first refrigerant, and this second refrigerant is contained in the refrigerant tank body that contacts with first refrigerant.
6. as each the described calorifics battery among the above-mentioned claim 1-4, it is characterized in that this calorifics battery comprises the cryogen vessel (14) that is used to keep first refrigerant and is used to keep the second refrigerant tank body (22 of a part of thermo-contact of this second refrigerant and this object; 32; 42), this second refrigerant tank body separates with this first cryogen vessel.
7. calorifics battery as claimed in claim 6 is characterized in that, the second refrigerant tank body (32) is integral with this part of this object.
8. calorifics battery as claimed in claim 6 is characterized in that, the second refrigerant tank body (42) forms as heat shield piece, and a part of roughly surrounding this object stops roughly that thus irradiated with thermal radiation arrives this part of this object.
9. as each the described calorifics battery in the above-mentioned claim, it is characterized in that these second parts are by the tank body (22 that comprises second refrigerant; 32; 42) form, this tank body is filled with the filler of the perforate that fin structure, thermal conductive network or Heat Conduction Material make at least in part.
10. as each or the described calorifics battery of claim 9 among the above-mentioned claim 1-7, it is characterized in that it is arranged to be convenient to cool off the bobbin (10) of the roughly cylindricality that is used for the scroll magnet,
Wherein, these second parts are by the tank body (22 that comprises second refrigerant; 32; 42) form, its attaching becomes outer surface and bobbin thermally coupled and mechanical connection, and this bobbin comprises the inside with first diameter and have at least one outside of second diameter, and second diameter is greater than first diameter,
Wherein, this tank body is general toroidal or cylindrical shape, and coaxial with bobbin, and this tank body is contained in roughly in the cylindricality volume basically, and this volume is coaxial with bobbin, and has the external diameter that equals this second diameter and equal the internal diameter of this first diameter.
11. each the described calorifics battery as in the above-mentioned claim is characterized in that this second refrigerant consists essentially of nitrogen.
12. a magnetic resonance imaging (MRI) system, it comprises that around the superconducting coil (12) of the bobbin (10) of heat conduction this superconducting coil and this bobbin are arranged to be convenient to by cooling off as each the described calorifics battery in the above-mentioned claim.
13. roughly (MRI) system of the magnetic resonance imaging shown in accompanying drawing 2-4 or calorifics battery.
14. a method that is used in required haulage time section object (10) being remained on low temperature, it may further comprise the steps:
At tank body (22; 32; 42) provide second refrigerant in, this tank body and this object thermally coupled;
Add and this object and hot linked first refrigerant of this second refrigerant, thereby so that this object and enemy's refrigerant are remained on first temperature by the boiling of this first refrigerant.
15. method as claimed in claim 14 is characterized in that, also is included in to add first refrigerant before by using the closed loop refrigerating plant to cool off the step of this second refrigerant.
16. the method with the low temperature transporting equipment, it may further comprise the steps:
As described in claim 14 or 15, this object is remained on first low temperature, exhaust up to this first refrigerant boiling; With
After this first refrigerant boiling exhausts, make this second refrigerant phase transformation thus this object to be remained on second low temperature that is higher than this first low temperature, be in the phase transition temperature of second refrigerant.
17. method as claimed in claim 16 is characterized in that, this phase transformation is the boiling of second refrigerant.
18. method as claimed in claim 16 is characterized in that, this phase transformation is the thawing of second refrigerant.
19. method as claimed in claim 16 is characterized in that, this phase transformation is the solid transformation of second refrigerant.
CN200610067682.3A 2005-03-23 2006-03-23 Apparatus and method for maintaining a system at a cryogenic temperature over an extended period of time without active refrigeration Pending CN1837721A (en)

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Cited By (1)

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Publication number Priority date Publication date Assignee Title
CN107110928A (en) * 2014-12-31 2017-08-29 通用电气公司 System and method for cooling down MR imaging apparatus

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US8598881B2 (en) * 2011-01-11 2013-12-03 General Electric Company Magnetic resonance imaging system with thermal reservoir and method for cooling

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US4212169A (en) * 1978-02-21 1980-07-15 Varian Associates, Inc. Cryostat for superconducting NMR spectrometer
JPS5932758A (en) * 1982-08-16 1984-02-22 株式会社日立製作所 Cryostat with helium refrigerator

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN107110928A (en) * 2014-12-31 2017-08-29 通用电气公司 System and method for cooling down MR imaging apparatus

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