EP2593735A2

EP2593735A2 - Cooling apparatus

Info

Publication number: EP2593735A2
Application number: EP11738939.5A
Authority: EP
Inventors: Johannes Wild
Original assignee: Wild Johannes
Current assignee: Wild Johannes
Priority date: 2010-07-12
Filing date: 2011-07-12
Publication date: 2013-05-22
Anticipated expiration: 2031-07-12
Also published as: US20130205826A1; ES2717632T3; AT510064B1; CY1121387T1; PL2593735T3; WO2012006645A2; EP2593735B1; HUE041997T2; AT510064A1; WO2012006645A3; US9851126B2; LT2593735T

Abstract

In a cooling apparatus with a closed cooling circuit for cooling objects to semi-cryogenic or cryogenic temperatures of 230K to 80K, the cooling apparatus comprising a compressor for compressing a coolant, to which compressor the coolant is supplied in a gaseous state and from which the coolant emerges in a compressed gaseous state, an after-cooler which is connected downstream of the compressor and from which most of the coolant emerges in gaseous form, a counterflow heat exchanger comprising a feed line and a return line, which are arranged in such a manner that the compressed coolant is liquefied in the feed line by the expanded coolant flowing through the return line being heated, and a cooling head which is connected to the feed line and the return line and through which the coolant flows and in which the coolant is evaporated, the cooling head (11) is arranged in a vacuum chamber (16) which can be connected to a negative pressure source and is connected to the feed line and the return line (8, 9) of the counterflow heat exchanger (7) via flexible connecting lines (13, 14).

Description

cooler

The invention relates to a cooling device with a closed cooling circuit for cooling objects to semi-cryogenic temperatures of 230 K to 80 K, comprising a compressor for compressing a coolant to which the coolant is supplied in the gaseous state and from which the coolant in compressed gaseous state exits, a compressor downstream aftercooler, a countercurrent heat exchanger comprising a supply and a return line, which are arranged such that the compressed refrigerant in the supply line is liquefied by heating the flowing through the return line expanded refrigerant, and one with the Supply and return line connected, cooled by the coolant cooling head in which the coolant evaporates.

Such a cooling device can be found, for example, in document EP 650574 A1. In commercial cooling systems, the countercurrent heat exchanger and the cooling head are combined to form a structural unit and placed in a vacuum chamber in which the object to be cooled is also placed. The countercurrent heat exchanger arranged in the vacuum chamber is thereby integrated into the cooling circuit via flexible gas supply. Since the coolant in the flexible gas supply lines is at room temperature and only in the vacuum chamber is brought to semi-cryogenic or cryogenic temperatures, eliminating the need for the isolation of these lines. The problems associated with the transport of coolant cooled to semi-cryogenic or cryogenic temperatures via flexible lines, such as icing, the formation of condensation water and the occurrence of heat losses, are thus avoided. The disadvantage, however, lies in the fact that the devices require a large vacuum chamber suitable for Many processes are undesirable or even unusable. The heat exchangers used in such devices are usually several meters long and are wound in a spiral in order to achieve a certain compactness of the cooling head with the heat exchanger. Nevertheless, the heat exchangers are relatively large even at low power (eg -130 ° C at 30W) (about 200mm high with a diameter of 80mm). Furthermore, such a cooling system requires a good vacuum system, since the volume of the vacuum chamber must be correspondingly large. In existing devices (eg Polycold Cryotiger) that use the Mixed Gas Joule Thomson process (see EP 650574 AI) and have the countercurrent heat exchanger with cooling head in the vacuum chamber, an increase in cooling capacity is accompanied by a significant increase in the heat exchanger. Especially at higher cooling capacities (> 50W) such devices are no longer economically viable or unattractive, especially for scientific applications (eg high power laser amplifiers, eg 150W at 130K, laser crystals with dimensions of eg 3mmx6mm) where small vacuum chambers are used. wishes are.

The invention therefore aims to improve a cooling device such that a cooling of an object in an efficient manner to the lowest possible semi-cryogenic or cryogenic temperatures succeeds, the vacuum chamber should be designed as small and handy as possible and at the same time achieves a significant increase in performance should be (eg instead of 30W / 140K, 200W / 140K). Furthermore, the losses during transport of the coolant should be kept as low as possible.

To achieve this object, the cooling device of the type mentioned is inventively further developed to the effect that the cooling head is arranged in a connectable to a vacuum source vacuum chamber, the above xible connecting lines is connected to the supply and the return line of the countercurrent heat exchanger, so that the countercurrent heat exchanger is arranged outside the vacuum chamber. The invention is thus based on the idea of using the conventional Mixed JT process and carrying out the process of liquefying the coolant by means of the countercurrent heat exchanger separated from the vacuum chamber. The liquefaction of the coolant thus takes place outside the vacuum chamber, wherein the liquefied coolant is supplied to the vacuum chamber via flexible connecting lines. It is only necessary to ensure that the heat exchanger and the connecting lines are suitably thermally insulated. The heat exchanger can be isolated, for example, by means of its own vacuum chamber with vacuum pump or more easily by means of expanded polystyrene (EPS), extruded polystyrene (XPS) insulation, polyurethane (PUR) insulation or by means of a vacuum insulation panel (VIP). Since the cooling capacities can be multiplied due to the design according to the invention, losses due to a possibly poorer insulation of the heat exchanger play only a minor role. For example, performances were realized on a cooling head with (cylinder: H 35mm x D 35mm) 300W / 140K. This corresponds to a tenfold increase in cooling capacity with a reduction in volume of approximately 30 times. For better thermal insulation, in particular at lower temperatures, a temperature radiation-reflecting layer of aluminum foil or equivalent material can be introduced into the insulation of the heat exchanger. This results, for example, in a layer structure EPS, aluminum foil, EPS, aluminum foil, ...

Due to the construction according to the invention, there is the possibility to form the cooling unit and the cooling head as a functionally separate units, so that in the cooling head itself no bulky components of the cooling unit, such as For example, a Gegenstromwärmetausc er od. Like., Must be arranged. This makes it possible, furthermore, to provide a cooling unit, which corresponds to the respective requirements, with the required cooling power in each case, without the cooling head having to be adapted in any way and without the handling of the cooling head being impaired in any way.

A particularly easy handling is ensured by the fact that, as it corresponds to a preferred development, the compressor, the aftercooler and the countercurrent heat exchanger are arranged together in a stand unit whose housing has a passage for connecting the countercurrent heat exchanger with the vacuum chamber connecting lines.

Essential in the case of the Mixed Gas Joule Thomson refrigeration unit is that the radiator, with the interposition of a throttle element, is connected to the supply line of the countercurrent heat exchanger so that the necessary pressure reduction of the refrigerant takes place and the liquefied coolant can evaporate in the cold head. A particularly advantageous construction in this context provides that the connecting line connecting the supply line of the countercurrent heat exchanger with the cooling head forms the throttle element.

In order to minimize the thermal losses during transport of the coolant through the connecting lines, it is provided according to a preferred development of the invention that the connecting lines have a vacuum insulation. Preferably, it can be provided that the vacuum chamber and the vacuum insulation of the connecting lines are in direct contact with each other and can be connected to a common vacuum source. This has the advantage that the vacuum system of the vacuum chamber is used in order to provide the refrigerant in a suitable form. to isolate medium on the transport between the vacuum chamber or the cooling head and the cooling reservoir and to make a vacuum feedthrough. In the vacuum chamber itself is located on the connecting lines mounted cooling head (eg copper) through which the refrigerant (eg liquid nitrogen) is coming from the connecting lines coming. In this case, the existing vacuum chamber is expanded by the relatively small volume of the vacuum insulation of the connecting lines and at the same time creates a vacuum connection between the vacuum insulation of the connecting lines and the vacuum chamber. Thus, the problem of the vacuum feedthrough and the insulation of the connecting lines is achieved with little effort and expense. It is preferably provided that the vacuum chamber has a passage for the connecting lines, which is designed such that the cavity of the vacuum insulation of the connecting lines is in communication with the interior of the vacuum chamber.

At the other end of the connecting lines, ie on the side of the cold reservoir, the refrigerant-carrying line is led out of the vacuum insulation, as well as suitable in vacuum-insulated pipes known from the prior art. It is particularly important to pay attention to the thermal conductivity of the cladding tube of the vacuum insulation and the heat transfer surface. A good vacuum welding during the transition is also important. This transition, which should cause low heat transfer losses, can be further protected by conventional insulation against condensation or ice. Due to the described training, it is now possible extremely efficient, space-saving (volume-saving), depending on the dimensions of the respective cooling unit to initiate any refrigeration capacity in a vacuum chamber. A particularly simple construction of the vacuum insulation of the connecting lines is achieved if, as is the case with a preferred development of the invention, the vacuum insulation comprises an enveloping tube surrounding the connecting lines to form a preferably substantially annular cavity. The buffer tube can be flexible as well as the connecting lines. In order to prevent the connecting lines from touching the enveloping hose, which would lead to an undesirable heat transfer, the embodiment is preferably designed such that at least one spacer is arranged in the hollow space between the connecting lines and the enveloping hose. If, as is preferred, the spacer has a corrugated outer and inner contour, it is ensured that between spacers on the one hand and the buffer tube and the connecting lines on the other hand only point or linear contacts arise, due to such Hertz 'shear contacts the heat input from the outside can be further reduced. A particularly simple structure is achieved according to a preferred embodiment, when the common vacuum source is connected to the vacuum chamber.

Furthermore, it is preferably provided that in the vacuum chamber surrounding the implementation, in particular tubular spacer is arranged, which defines the distance between the cooling head and the inner wall of the vacuum chamber, wherein the spacer has radial openings, so that the interior of the vacuum chamber with the cavity the vacuum insulation of the connecting lines is in communication.

The coolant preferably comprises butane and / or isobutane and / or propane and / or propene and / or ethyne and / or ethane and / or ethene and / or methane and / or argon and / or nitrogen.

The invention will now be explained in more detail with reference to embodiments shown schematically in the drawing. 2 shows a sectional view of the cooling head with the connecting lines and FIG. 3 shows a section according to the line III-III of FIG.

The cooling circuit shown in Fig.l is usually referred to as a mixed gas Joule Thomson cooling process and is described for example in the document EP 650574 AI. The cooling circuit comprises a compressor 1 for compressing the gaseously supplied refrigerant in 2. The refrigerant may be, for example, a gas mixture consisting of propane, ethane, methane and nitrogen. The compressed refrigerant is fed via a line 3 to an oil separator 4, with which the possibly in the compressor 1 with the refrigerant mixing oil is separated. The oil purified by the oil is then fed to an aftercooler 5, in which the heat supplied to the compressor 1 is removed from the refrigerant. The cooled, compressed, but still mostly gaseous refrigerant is then fed via a line 6 to a countercurrent heat exchanger 7, in which the coolant flowing through the refrigerant supply line 8 is cooled and liquefied by the refrigerant flowing in the refrigerant return line 9. The refrigerant supply line 8 and the refrigerant return line 9 may in practice be several meters long and are often helically or spirally wound in order to achieve a certain compactness of the heat flow heat exchanger. The liquefied refrigerant is depressurized via a throttle 10, so that the refrigerant in the cooling head 11 evaporate and thereby escape the environment evaporation heat. The cooling head 11 is from Coolant flows through and is therefore designed for example as a hollow cylinder. The flowing back from the cooling head 11 refrigerant is heated in countercurrent heat exchanger 7 in the sequence up to room temperature, wherein the refluxing refrigerant cools the flowing refrigerant. For cooling an object, which is schematically indicated by 12, this is brought into contact with the cooling head 11. The cooling head 11 is therefore made of a thermally conductive material such as copper. According to the invention, the cooling head 11 is connected via connecting lines

13 and 14 connected to the counterflow heat exchanger 7, so that the cooling unit 15 and arranged in a vacuum chamber 16 cooling head 11 can be realized as separate structural units. The inventive construction makes it necessary that the cooled and liquefied in the heat exchanger 7 refrigerant is transported via the connecting lines 13 and 14 over a more or less long distance, so that a sufficient insulation of the connecting lines must be ensured.

2, the cooling head together with the vacuum chamber and the connecting lines are shown in more detail. It can be seen that the connecting lines 13 and 14 have a vacuum insulation 17 whose evacuated interior communicates with the interior of the vacuum chamber 16. The connecting lines 13 and

14 may be formed as flexible tubes to improve the handling. The vacuum insulation 17 of the connecting line has a flexible Hüllschlauch 18, which may be formed for example as a stainless steel corrugated pipe, which preferably has a steel jacket. Between the connecting lines 13 and 14, which may also have a corrugated outer contour, spacers 19 may be arranged, which may also be made flexible. The spacers 19 preferably have a corrugated outer contour, so that due to the line contacts achieved with the cladding tube 18 and the connecting lines 13 and 14, the heat transfer is minimized. The spacer 19 thus serves the mechanical and thus thermal decoupling of the connecting lines 13 and 14 to the cladding tube 18th It should be sufficiently flexible, temperature stable, resistant to aging and degassing free (eg Teflon, plastic, stainless steel). At the point 20, the connecting lines 13 and 14 are led out of the vacuum insulation 17. Low thermal losses at the transition point 20 should be taken into account. This can be achieved by materials with low thermal conductivity and a low transition cross-section (eg stainless steel). In addition, the interface 20 may be protected by conventional thermal insulation materials (eg, foamed polystyrene, Amaflex).

The connecting lines 13 and 14 may be thermally coupled. The connecting lines 13 and 14 can alternatively be guided into each other. Depending on the cross-section and length of the connecting line 13, the coolant may experience a pressure reduction along the supply line, so that the refrigerant is evaporated in the cooling head as in compression refrigerating machines and heat is dissipated. In this case, the supply line is immediately throttle body.

The vacuum insulation 17 is connected to a vacuum flange 21, through which the connecting lines 13 and 14 are passed and fed to the cooling head 11. In order to improve the mechanical stability of the cooling head 11, a spacer 22 is disposed between the cooling head 11 and the vacuum flange 21, which may for example consist of Teflon, ceramic or stainless steel and ausgasungsbeständig, low temperature suitable, should be resistant to embrittlement and aging. In this case, sufficient thermal decoupling of the distance In the cross-sectional view of Figure 3 it can be seen that the spacer 22 has a plurality of radial openings 24, so that the evacuated interior of the vacuum insulation of the connecting lines with the evacuated interior of the Vacuum chamber 16 is in a conductive connection. A flange for connection to a vacuum pump is indicated at 23. When the cooling head flows through coolant evenly and when the cooling head is mechanically stabilized by means of spacers, the cooling head is extremely low in vibration.

Typical applications for the invention are the cooling of high-power laser amplifiers and various cooling tasks in analytical chemistry, in the field of superconductivity, astronomy and in general in research and development as well as in medical diagnostics.

Claims

Claims:

A closed-circuit cooling apparatus for cooling objects to semi-cryogenic temperatures of 230K to 80K comprising a compressor for compressing a refrigerant to which the refrigerant is supplied in a gaseous state and from which the refrigerant exits in a compressed gaseous state, an aftercooler downstream of the compressor, from which the coolant exits for the most part in gaseous form, a countercurrent heat exchanger comprising a supply and a return line arranged such that the compressed coolant in the supply line can be liquefied while heating the expanded coolant flowing through the return line, and a cooling head through which the coolant flows, in which the coolant flows, which is connected to the supply and return lines, characterized in that the cooling head (11) is arranged in a vacuum chamber (16) which can be connected to a vacuum source and which is connected via flexible le connecting lines (13,14) with the supply and the return line (8,9) of the countercurrent heat exchanger (7) is connected, so that the countercurrent heat exchanger is arranged outside the vacuum chamber.

2. Cooling device according to claim 1, characterized in that the compressor (1), the aftercooler (5) and the countercurrent heat exchanger (7) are arranged together in a stand unit whose housing has a passage for the countercurrent heat exchanger (7) with the vacuum chamber ( 16) connecting connecting lines (13,14).

3. Cooling device according to claim 1 or 2, characterized in that the cooling head (11) with the interposition of a throttle body (10) with the supply line (8) of the countercurrent heat exchanger (7) is in communication.

4. Cooling device according to claim 3, characterized in that the supply line (8) of the countercurrent heat exchanger (7) with the cooling head (11) connecting connecting line (13) forms the Dros- selorgan (10).

5. Cooling device according to one of claims 1 to 4, characterized in that the connecting lines (13,14) have a vacuum insulation (17).

6. Cooling device according to claim 5, characterized in that the vacuum insulation (17) comprises a the connecting lines (13,14) to form a substantially annular cavity surrounding Hüllschlauch (18), wherein the cavity with a vacuum source is connectable.

7. Cooling device according to claim 5 or 6, characterized in that the vacuum chamber (16) and the vacuum insulation (17) of the connecting lines (13,14) communicate with each other directly and are connectable to a common vacuum source.

8. Cooling device according to claim 5, 6 or 7, characterized in that the vacuum chamber (16) has a passage for the connecting lines (13,14) which is designed such that the cavity of the vacuum insulation (17) of the connecting lines (13, 14) communicates with the interior of the vacuum chamber (16).

9. Cooling device according to one of claims 6 to 8, characterized in that in the cavity between the connecting lines (13,14) and the enveloping tube (18) at least one spacer (19) is arranged.

10. Cooling device according to claim 9, characterized in that the spacer (19) has a corrugated outer and inner contour.

11. Cooling device according to one of claims 6 to 10, characterized in that the vacuum chamber (16) has a connection (23) for connecting the common vacuum source.

12. Cooling device according to one of claims 1 to 11, characterized in that in the vacuum chamber (16) surrounding a bushing, in particular tubular spacer (22) is arranged, the distance between the cooling head (11) and the inner wall of the vacuum chamber ( 16), wherein the spacer (22) has radial openings (24), so that the interior of the vacuum chamber (16) with the cavity of the vacuum insulation (17) of the connecting lines (13,14) is in communication.

13. Cooling device according to one of claims 1 to 12, characterized in that the coolant is butane and / or iso-butane and / or propane and / or propene and / or ethyne and / or ethane and / or ethene and / or methane and / or argon and / or nitrogen.