CN102563993B - Absorption type low-temperature thermal switch with normal-pressure sealed helium - Google Patents

Absorption type low-temperature thermal switch with normal-pressure sealed helium Download PDF

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CN102563993B
CN102563993B CN201210009802.XA CN201210009802A CN102563993B CN 102563993 B CN102563993 B CN 102563993B CN 201210009802 A CN201210009802 A CN 201210009802A CN 102563993 B CN102563993 B CN 102563993B
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thermal switch
cold
helium
junction post
temperature
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CN102563993A (en
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苏少奎
周玉荣
樊洁
刘瑞元
宋小会
张殿琳
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Institute of Physics of CAS
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Abstract

The invention discloses an absorption type low-temperature thermal switch with normal-pressure helium. The absorption type low-temperature thermal switch comprises a storage chamber, a refrigerating unit and a thermal switch body, the storage chamber is used for storing helium with preset pressure, the refrigerating unit is provided with a primary cold screen, a secondary cold screen and an absorption chamber positioned between the primary cold screen and the secondary cold screen, the storage chamber is communicated with the absorption chamber by a capillary tube, activated carbon is placed in the absorption chamber, a temperature control device for controlling the temperature of the inside of the absorption chamber is further arranged on the absorption chamber, the thermal switch body is provided with a shell, a cold end post and a hot end post, the cold end post and the hot end post are sleeved in the shell, the absorption chamber is connected with the cold end post by a guide tube, and a proper gap is reserved between the cold end post and the hot end post. When the thermal switch is 'turned on', liquid helium is assuredly remained in the thermal switch body. In addition, media and the helium which are used for heat exchange are under the condition of normal pressure and are sealed, and accordingly the absorption type low-temperature thermal switch is safe and is simple in operation. Furthermore, the thermal switch can guarantee that a heat gap at a temperature span ranging from 2K to 300K is proper.

Description

Absorption type low-temperature thermal switch with normal-pressure sealed helium
Technical field
The present invention relates to a kind of cryogenic engineering thermal switch, the thermal switch that particularly refrigeration machine secondary and temperature control platform conduct heat.
Background technology
In cryogenic technique, often need the temperature control platform can be from 4K to 300K, or even 400K continuous temperature control.Realize temperature control platform and be as cold as 4K, just need temperature control platform and low-temperature receiver to have well thermally coupled; But in the time of temperature control platform will being raised to high temperature, need again temperature control platform and low-temperature receiver thermally coupled very poor, can both can just temperature control platform be raised to room temperature with less heating power like this, meanwhile, also do not affect the temperature of low-temperature receiver.Use liquid helium as the temperature-controlling system of refrigeration source, by controlling the flow of helium and heating power easily at 2~400K scope temp, also do not affect the temperature of liquid helium, thereby do not affect the use that keeps the superconducting magnet of superconducting state by liquid helium.But, due to shortage and the operational inconvenience of liquid helium, thereby make aneroid helium refrigeration system obtain people's favor.
But the defect of aneroid helium refrigerator is that its cold head and temperature control platform are all in vacuum, this brings very large difficulty to the heat conduction between them.If temperature control platform and cold head thermal conductance are fine, temperature control platform is easy to arrive 4K temperature, and still, in the time of temperature control platform being controlled at slightly to high-temperature, cold head rises because of the excessive temperature of heat load, so, just the superconducting magnet of cryocooled cannot have been worked.If the cold head thermal conductance of temperature control platform and refrigeration machine is poor, temperature control platform cannot arrive lower temperature.So aneroid helium refrigerator needs a set of thermal conductance at low temperatures good, the poor heat-conducting system of thermal conductance under high temperature.
Be make two heat conducting bars, one is high thermal conductance, and for low-temperature space, one is low thermal conductance, for high-temperature region.This method need to be installed temperature control platform twice, not only operation inconvenience, and most important defect is bring variations in temperature discontinuous.
Also having conventional method is to use helium absorption type thermal switch.Generally to utilize the material absorption such as active carbon or emit helium to change the thermal conductance between cold and hot end.The temperature control from room temperature to 4K that can be continuous.Its shortcoming is, because helium thermal conductance is relatively little, so, once that the lowest temperature of the heat load of temperature control platform large (specimen holder connecting if any room temperature, with system of optical window etc.) temperature control platform will arrive 4K is following.
Summary of the invention
The problem existing for prior art, the object of the present invention is to provide a kind of absorption type low-temperature thermal switch with normal-pressure sealed helium, can realize and under low temperature, have larger thermal conductivity and operation walk away safety.
For achieving the above object, a kind of normal pressure helium adsorption type low temperature thermal switch provided by the invention comprises:
Storeroom, for storing the helium of predetermined pressure;
Refrigeration unit, this refrigeration unit has the cold screen of one-level, the cold screen of secondary and the adsorption chamber between the cold screen of one-level and the cold screen of secondary, described storeroom is conducted by capillary and adsorption chamber, in described adsorption chamber, be placed with active carbon, on described adsorption chamber, be also provided with the attemperating unit of described absorption indoor temperature;
Thermal switch body, has shell and sheathed cold junction post and hot junction post in the enclosure, and described adsorption chamber is connected with cold junction post by conduit, between described cold junction post and hot junction post, has suitable gap.
Between described storeroom and described capillary, be provided with the valve of controlling helium gas flow.
Preferably, described storeroom stores 1 atmospheric helium.
Preferably, described adsorption chamber is arranged in a heat shielding cover.
Preferably, described gap is 20 ± 10 microns.
Preferably, the Length Ratio of described cold junction post and hot junction post is 4~7: 1.
Preferably, the Length Ratio of described cold junction post and hot junction post is 6: 1.
Preferably, the material of described cold junction post and hot junction post is red copper.
Preferably, described shell is stainless steel material.
Preferably, described attemperating unit comprises heater and thermometer.
Thermal switch of the present invention, when "open" state, can ensure liquid helium and remain in thermal switch body, and, due to the medium for heat exchange---helium---be under normal pressure and seal, so be that safety and operation are easy; In addition, thermal switch of the present invention can guarantee that adiabatic gap is applicable at 2~300K warm area always.
Accompanying drawing explanation
Fig. 1 is structural representation of the present invention;
Fig. 2 is the relation of thermal conductance, secondary temperature and temperature control platform temperature;
Fig. 3 is the cooling rate comparison that thermal switch " is opened " " pass " two states.
1--storeroom, 2--adsorption chamber, 3--thermal switch shell, 4--thermal switch cold junction post, 5--temperature control platform, the cold screen of one-level of 6--pulse tube refrigerating machine, the cold screen of secondary of 7--pulse tube refrigerating machine, the hot and cold end face of 8--gap, 9--thermal switch hot junction post, 10--valve, the radiation-resistance mask of 11--adsorption chamber, 12--thermal switch body, 13--refrigeration unit, 14--capillary, 15--stainless steel tube
The specific embodiment
Below in conjunction with accompanying drawing one and the specific embodiment, further illustrate.
As shown in Figure 1, the present invention includes: thermal switch body 12, storeroom 1 and refrigeration unit (being refrigeration machine) 13, storeroom 1 is placed in room temperature environment, is inside filled with an atmospheric helium.Refrigeration machine 13 has the cold screen 6 of one-level, the cold screen 7 of secondary and the adsorption chamber 2 between the cold screen 6 of one-level and the cold screen 7 of secondary.Storeroom 1 is by capillary 14 and adsorption chamber 2 conductings.Adsorption chamber 2 inside are placed with active carbon, thermal switch body 12 has shell 3 and is set in cold junction post 4 and the hot junction post 9 in shell 3, adsorption chamber 2 is connected with the cold junction post 4 of thermal switch body 12 by stainless steel tube 15, between cold junction post 4 and hot junction post 9, has suitable gap.Hot junction post 9 connects temperature control platform 5, unsettled, can connect heat load or testing sample.
In addition, between storeroom 1 and capillary 14, be provided with a valve 10, be used for controlling the amount of helium that enters thermal switch body 12.Capillary 14 enters refrigeration machine 13 inside, uses the gap of 13, epoxy sealing capillary wall and refrigeration machine.Capillary 14 can be done heat sink processing at the cold screen of one-level 6 places, and postcapillary 14 enters the adsorption chamber 2 being under low temperature environment.Thermometer and heater are housed, in order to control the temperature of adsorption chamber 2 on adsorption chamber 2.Adsorption chamber 2 outer cup are provided with a heat shielding cover 11, and this heat shielding cover 11 is made by high thermal conducting material.Heat shielding cover 11 has better thermal conductance with the cold screen 7 of refrigeration machine secondary, but does not have hot being connected with adsorption chamber 2, and object is to reduce the radiant heat to adsorption chamber 2 around.
The present invention is by storeroom 1 as for room temperature environment, and the volume of storeroom 1 and low-temp. portion partial volume (mainly refer to the volume of adsorption chamber, but also comprise the volume of thermal switch body 12 and capillary 14) at the same temperature, have larger volume ratio.Like this, when thermal switch body 12 is during in low temperature, can there is enough pressure to be not less than 3K to guarantee liquid helium boiling point.Like this, just can retain liquid helium in thermal switch body 12 inside, and the convection current of liquid helium, boiling be the reason that its thermal conductivity is very high.In addition, the heat carrier of thermal switch body 12 inside (being cold junction post) adopts the material red copper of high thermal conductivity, to guarantee that the thermal resistance of cold junction post 4 and hot junction post 9 is only determined by the gap 8 between them.The shell of thermal switch body 12 is selected thermal conductance rate variance and the strong material of hardness, and stainless steel for example, for reducing unnecessary thermal conductance and providing support.And cold junction post 4 is 20 microns with the gap of hot junction post 9, can accurately control by fine thread.In addition, it is large that the Length Ratio of cold junction post 4 and hot junction post 9 is wanted, and namely cold junction will be grown, and can be 4~7: 1, and certainly, preferably, near 6: 1, object is when post 9 temperature in hot junction are very high, and adiabatic gap can not reduced a lot.Like this, temperature control end just can guarantee continuous alternating temperature from 4K to 300K.And cold and hot end face adopts cylinder formula, processing technology is simple like this, is also convenient to the control in adiabatic gap.
Below by instantiation, the present invention will be further described.
Storeroom 1 is positioned over room temperature environment, inside has an atmospheric helium.During valve 10 open mode, the helium of storeroom 1 can pass in and out adsorption chamber 2 and thermal switch body 12 freely by capillary 14.Adsorption chamber 2 materials are red copper, by a stainless steel tube that is about the φ 3X0.5 of 6 centimetres, are connected with cold junction post 4.Adsorption chamber 2 is outer is with a heat shielding cover 11, and heat shielding cover 11 materials are red copper, are directly installed on the cold screen 7 of secondary, do not contact with adsorption chamber 2.11 grams of active carbons are equipped with in adsorption chamber 2 inside, and outer surface is equipped with thermometer, heater.The shell of thermal switch body 12 is directly fixed on the cold screen 7 of secondary, and the inner cool and heat ends column material of thermal switch body 12 is red copper, and surface gold-plating, the long 60mm of cold junction post 4, and the long 10mm of hot junction post 9, diameter is 10mm, and shell 3 is 304 stainless steels of φ 12.8X0.3.Cold junction post 4 and hot junction post 9 are fine thread structure with stainless steel casing 3 contact portions, thereby can guarantee that cold junction post 4 and hot junction post 9 end distances are 20 microns when room temperature.Hot junction post 9 is one with temperature control platform 5, and temperature control platform 5 is unsettled, can connect load.Whole thermal switch system is sealed, and leak rate is less than 10 -9paLS.
When not moving, the state of valve 10 in opening, along with the reduction of temperature, helium is gradually by charcoal absorption, and adsorption chamber 2 reaches 10K when following by the time, valve-off 10.Adsorption chamber 2 is warming up to 40K, and now, from adsorption chamber 2 out, this is thermal switch "open" state to helium.The temperature of secondary is 2.8K, so, can form liquid helium and have thermal switch body 12 inside, thereby have very high thermal conductivity.As shown in Figure 2,3, by temperature and thermal conductance curve, can be clearly seen that, near boiling point, thermal conductance is the highest, can reach 0.3W/K; Cooling adsorption chamber 2, can reach 6K, and now, helium is by charcoal absorption, thereby thermal switch inside is vacuum state, and thermal conductance is very poor.This is thermal switch "off" state.Temperature control 300K easily, and the temperature of secondary is also lower than 4.5K.Accompanying drawing two is specific embodiments.
Although above the specific embodiment of the present invention is described in detail and is illustrated by example, but what should indicate is, those skilled in the art can make various changes and modifications above-mentioned embodiment, but these do not depart from the scope that spirit of the present invention and claim are recorded.

Claims (9)

1. a normal pressure helium adsorption type low temperature thermal switch, is characterized in that, comprising:
Storeroom, for storing the helium of predetermined pressure;
Refrigeration unit, this refrigeration unit has the cold screen of one-level, the cold screen of secondary and the adsorption chamber between the cold screen of one-level and the cold screen of secondary, described storeroom is conducted by capillary and adsorption chamber, in described adsorption chamber, be placed with active carbon, on described adsorption chamber, be also provided with the attemperating unit of described absorption indoor temperature;
Thermal switch body, has shell and sheathed cold junction post and hot junction post in the enclosure, and described adsorption chamber is connected with cold junction post by conduit, between described cold junction post and hot junction post, has suitable gap;
Wherein, between described storeroom and described capillary, be provided with the valve of controlling helium gas flow.
2. thermal switch as claimed in claim 1, is characterized in that, described storeroom stores 1 atmospheric helium.
3. thermal switch as claimed in claim 1, is characterized in that, described adsorption chamber is arranged in a heat shielding cover.
4. thermal switch as claimed in claim 1, is characterized in that, described gap is 20 ± 10 microns.
5. thermal switch as claimed in claim 1, is characterized in that, the Length Ratio of described cold junction post and hot junction post is 4~7:1.
6. thermal switch as claimed in claim 5, is characterized in that, the Length Ratio of described cold junction post and hot junction post is 6:1.
7. the thermal switch as described in as arbitrary in claim 1 to 6, is characterized in that, the material of described cold junction post and hot junction post is red copper.
8. thermal switch as claimed in claim 1, is characterized in that, described shell is stainless steel material.
9. thermal switch as claimed in claim 1, is characterized in that, described attemperating unit comprises heater and thermometer.
CN201210009802.XA 2012-01-13 2012-01-13 Absorption type low-temperature thermal switch with normal-pressure sealed helium Active CN102563993B (en)

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CN103257001B (en) * 2013-04-10 2015-05-13 中国科学院理化技术研究所 Three-phase point reproduction device with refrigerator as cold source
CN104654692A (en) * 2013-11-22 2015-05-27 中国科学院理化技术研究所 Air gap type thermal switch applied to extremely-low-temperature refrigerator and heat conduction method thereof
CN110308752A (en) * 2018-03-27 2019-10-08 中国科学院理化技术研究所 A kind of superhigh precision thermostat
CN112880231A (en) * 2021-02-04 2021-06-01 中国科学院理化技术研究所 Adsorption refrigeration system

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US3678992A (en) * 1970-08-06 1972-07-25 Philips Corp Thermal regenerator
CN2465122Y (en) * 2001-02-27 2001-12-12 中国科学院理化技术研究所 Device for adjusting cold end air flow phase of pulse tube refrigerator
US20040231340A1 (en) * 2003-05-23 2004-11-25 Uri Bin-Nun Low cost high performance laminate matrix
CN101105345A (en) * 2007-08-03 2008-01-16 浙江大学 Liquid helium temperature stirling type multi-grade pulse tube refrigerator adopting helium 3-helium 4 double working medium
CN102288065B (en) * 2010-06-17 2012-11-21 中国科学院理化技术研究所 Thermal switch and measuring device using the same

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