EP2354729B1 - Device for adjusting cryogenic temperatures - Google Patents

Description

The invention relates to a device for adjusting and maintaining cryogenic temperatures with at least one cold chamber and an energy-efficient and ice-free access to this, as they are generically in the DE 34 41 091 C2 is described.

Deep-freezing or cryogenic temperatures are usually generated by the action of cold and evaporating gases, whereby the endothermic volume increase of such gases is used for lowering the ambient temperature. In general, temperatures which are substantially lower than the temperature of the environment are referred to as "deep-freezing". Depending on the situation and the definition used, these can be temperatures around the freezing point up to absolute zero.

In the operation of devices in which areas have cryogenic temperatures, condensing and freezing air humidity and the concomitant icing, in particular of moving components, is a regular problem. This mainly concerns the accesses to the cryogenic areas, when these are frequently opened and closed become.

Icing develops a number of adverse effects. On the one hand, the risk of accidents z. B. in enter or passable cold stores significantly increased, on the other hand, icing prevent tight closing of the entrances, causing energy losses. In addition, the brittleness of known sealing materials in areas of cryogenic temperatures increases and limits their applications, duration of use and sealing effect.

In order to reduce the problem of icing and cold loss, measures are proposed by which a separation of cryogenic areas and areas with warmer temperatures is to be achieved. The most common measure is the use of a lock, the accesses are provided in the lock or in the cryogenic areas with various devices. It is also known to influence the temperatures and / or humidity within a lock targeted, as z. B. in the DE 34 22 790 A1 described is. According to the local disclosure heated surfaces are heated by means of directional radiant heaters and prevents icing this.

Particular claims are made of those means by the areas of very large temperature differences between the space to be cooled and the environment are separated, as with z. B. Cryogenic devices for biological samples or for medical applications may be the case.

From the DE 196 19 152 A1 is a freezer for trapped in flat bag frozen food is known, which has a refrigerant flowing through dies in a serving as a cold chamber housing. At the cold chamber two lock chambers are present, the respective volume of closable access on the one hand with the environment and on the other hand with the volume of the cold chamber in combination. The flat bag with the frozen food is introduced via the first lock chamber in the cold chamber, there pressed between the pressing tools and frozen. In order to largely avoid icing, the humidity in the first lock is reduced to a minimum value. Subsequently, the flat bag from the cold chamber is discharged into the second lock chamber and from this into the environment. Disadvantages here are volume flows which occur during insertion and removal of the flat bag in or out of the freezer.

According to the DE 34 41 091 C2 Temperatures of -150 ° C and lower are set in a thermally insulated cold chamber by the action of liquid nitrogen. The heat extraction takes place via heat exchangers, through which the nitrogen is passed.

In at least one wall of the cold chamber, there is a first access with a door which leads into an adjacent, likewise heat-insulated, lock chamber (henceforth lock chamber). The lock chamber communicates with a closable second access to the environment. In a device as used in the DE 34 41 091 C2 is described, so are a cryogenic gas volume in the cold chamber and at least one other cooled volume in the lock chamber available. To avoid an oversized cold loss from the To avoid cold chamber when opening the first access, the temperature of the lock chamber is lowered, the effect of cooling the cold chamber nitrogen is also used for cooling the lock chamber down to -60 ° C. An icing is largely countered by the blowing of dried air, however, in addition, the seals of the doors are heated to ensure their proper functioning. In order to allow a visual inspection in the cold chamber and the lock chamber, heatable viewing windows are installed in the doors. Motors which serve to drive devices in the cold chamber are preferably arranged in the lock chamber or outside the heat-insulated wall of the cold chamber or lock chamber. By using suitable sensors and thermostats, the device can be operated automatically. DE 3441091 C2 discloses a device according to the preamble of claim 1.

A disadvantage of the known devices is the occurrence of volume flows in the operation of at least one of the entrances and the complex and energy-intensive measures to avoid icing.

The invention has for its object to show a way of energy-efficient and ice-free access to cryogenic cooling chambers through the insulated wall through, the occurrence of adverse flow rates should be avoided.

The object is achieved by a device for setting cryogenic temperatures, with a, a first volume enclosing cold chamber in the heat-insulated wall a closable first access is provided, via which the first volume is connected to a second volume of a heat-insulated lock chamber, also in the lock chamber there is a closable second access via which the second volume communicates with the environment of the device and the temperatures in the cold chamber and lock chamber are adjusted by the action of a cold or evaporating refrigerant, achieved by the first access having a vertical extent, which is less than the vertical extent of the lock chamber and that the second volume extends beyond the highest point of the vertical extent of the first access. Only in this way is it possible to set the temperatures and temperature profiles (temperature gradients) in the first and second volumes, in particular in their upper regions, largely independently of one another. At the first access a first closure is arranged, which largely prevents the formation of a volume flow between the cold chamber and lock chamber in the closed state. The second access is arranged to begin above and at a vertical distance from the highest vertical extension of the first access. Also at the second access is a closure, which, however, gas-tight and pressure-tight is closed here. First and second volumes have temperature profiles over their vertical dimensions, which can be adjusted largely independently of each other. The adjustment of the temperature in the second volume is carried out so that in the region of closed second access the temperature is more than 0 ° C, whereby ice formation on the second closure is avoided.

The core of the invention is the creation of stable, vertical temperature stratifications in the two volumes, whereby the formation of unfavorable volume flows, especially in the supply and removal of refrigerated goods, is greatly reduced. In addition, the temperature profile of the stratifications in the two volumes can be set largely independently.

All of the elements of the device described below and arrangements thereof therefore essentially serve to produce in each case stable temperature stratifications in the first and second volumes. In this case, the temperatures increase along the vertical extent of the first or second volume, wherein the temperature stratification can be described by the vertical temperature profile, to which reference is made in the following.

A preferred temperature profile in the cold chamber is given by temperatures from below -100 ° C to temperatures of more than 0 ° C and up to + 25 ° C. The temperatures at the upper end of the lock chamber are above 0 ° C to + 25 ° C. Areas with temperatures above 0 ° C can be referred to as hot areas, areas with 0 ° C and below as cold areas for simplicity's sake.

For the operation of the device according to the invention, a cold or evaporating cooling gas is used. This can be a gas such. For example, molecular nitrogen or a gas mixture such. B. be air.

In the cold chamber, a cooling device is provided which generates cryogenic temperatures in the cold chamber in a known manner. In this case, systems may be used in which the withdrawal of heat energy takes place by means of appropriately sized and dimensioned heat exchangers. Furthermore, cooling gas can also be introduced directly into the cold chamber, so that a refrigerated goods located therein is lapped by the cooling gas.

It is within the meaning of the invention if the cooling device is arranged on or in the vicinity of the bottom of the cold chamber. If a cooling gas is introduced directly, this advantageously takes place so that it collects at the bottom of the cold chamber and flow turbulences are avoided as far as possible.

Refrigerated goods are all objects or substances referred to, which are introduced for the purpose of their cooling for temporary storage in the cold chamber. Of course, substances to be cooled can also be packed. The refrigerated goods can be placed, for example, in standard and laboratory standard mounts or freezer boxes. For example, buffered and unbuffered biological samples such as tissue, DNA, cell material or organelles may be stored as refrigerated goods.

The wall of the cold chamber is the well-known prior art, very well insulated against the environment of the device and have correspondingly low heat transfer coefficient [W / (m ² K)] on.

The first access is provided with a first closure and can be locked by this, wherein the first closure does not necessarily have to close gas-tight. Such a first closure can be actuated manually and / or by a technical device and be, for example, a stopper, a slide, a lid or a door. The dimensions of the first access are selected so that the intended refrigerated goods in the opened state of the first closure can be easily moved through the first access.

The cold chamber may be designed one or more chambers.

In an advantageous multi-chambered embodiment, the first access is at a vertical distance to the bottom of the cold chamber. The region lying below the first access can be formed as at least one storage chamber and include devices for the systematic orderly storage of the goods to be cooled. Advantageously, such devices include vertically movable means for Picking up the chilled goods. Storage chamber and the at least one space above, hereinafter referred to as manipulation chamber, may be formed so that the vertical temperature profile in the region of the transition from the storage chamber and manipulation chamber a temperature jump, preferably towards higher temperatures has. This can be achieved in that the storage chamber is spatially delimited from the manipulation chamber, as can be realized for example by a lid or a cover at the upper end of the storage chamber. However, the manipulation chamber and the storage chamber are not thermally decoupled from each other by the spatial delimitation in the sense of two independent, heat-insulated volumes.

In the wall of the cold chamber may further be present at least one engagement device that allow manipulative activities on the refrigerated goods. Such engagement devices are preferably arranged so that in addition a movement of the goods to be cooled, possibly using aids and / or auxiliary devices, in and out of an optionally existing storage chamber and through the first access is possible therethrough. The interventional device can be used as a manual intervention, for. B. be formed on heat-insulated gloves and / or purely mechanical devices such as gripping arms. In addition, at least one viewing window is advantageously arranged in the wall of the cold chamber so that a person operating the intervention device can see into the cold chamber. It can be arranged more windows. In addition, in the wall of the cold chamber and / or the wall of the lock chamber imaging systems such as cameras and / or arrangements of optical elements such as lenses and mirrors may be present.

An intervention device and viewing window can also be present in the lock chamber.

Furthermore, a device may be provided with which samples can be moved through the first access, which is not actuated by an intervention device, but for example by a mechanical drive and a controller.

The arrangement of engines, for. B. for the movement of the first closure, the engagement device and the like is preferably carried out of cold or lock chamber. If, in alternative embodiments, motors are arranged in the interior of the cold chamber or lock chamber, they can be designed to be heatable, which, however, can have a disadvantageous effect on the attainability of a stable thermal stratification and possibly means increased costs for the insulation of the motors.

The manipulative activities are performed in the manipulation chamber located above the storage chamber. The temperature profile of the first volume is adjusted so that the manipulative activities take place at temperatures at which thawing of the chilled goods is prevented. At the same time, the materials making up the interventional device should remain sufficiently flexible and have a material thickness which ensures a minimum of tactile perception during the manipulative activities. It is advantageous if the manipulative activities take place at temperatures colder than -100 ° C.

The vertical extent of the lock chamber should not be higher than the height to which the cooling gas is lifted by the pressure existing in the cold chamber. Otherwise, there is the disadvantage that when closing the second access a residual volume of ambient air is trapped in the lock chamber and it can cause condensation and icing.

It is of great advantage if the gas pressure inside the device is preferably higher by 10 to 50 Pascal than the ambient pressure. As a result, when opening the second access or simultaneously opening both entrances, a volumetric flow directed towards the device according to the invention is always ensured, which prevents the ingress of moisture-laden air into the lock chamber.

The insulation of the wall of the lock chamber is also designed so that their heat transfer coefficients are low and equal over the extent of the wall of the lock chamber.

Isolation means all measures for influencing the heat transfer coefficients. An increase in the insulation can be achieved, for example, by a thicker layer of an insulating material or by the use of different insulating materials with mutually different Dämmleistungen.

In a preferred embodiment of the device according to the invention, however, the heat transfer coefficients may increase with the vertical extent of the lock chamber. As a result, more heat is absorbed from the environment of the device in the upper regions of the lock chamber. Such a structural design is a passive measure for influencing the temperature profile in the lock chamber. It can preferably be implemented by reducing the insulation and / or by using materials with a lower insulating effect.

It is also possible that the insulation of the wall of the cold chamber is carried out analogously as the isolation of the wall of the lock chamber.

Passive measures are particularly useful when the ambient temperatures of the device are largely constant and predictable. This can for example be the case in air-conditioned laboratory rooms.

In order to be able to react to changing environmental conditions, it is also possible for a device for influencing the temperature, preferably a heater, to be present above the first access. This communicates with a heating control. With this, the temperature profile in the lock chamber can be actively influenced. Of course, active and passive measures can also be combined.

All measures for adjusting the temperature gradients must be such that the dew point lies below the outer surface of the wall of the lock chamber. In addition, the second access and the second closure must be arranged in the warm area of the lock chamber.

The second access beginning above the first access preferably closes the lock chamber upwards, but may also be arranged in a wall of the lock chamber which does not face the cold chamber.

The lock chamber may optionally extend below the first access. The space formed thereby can be used as an intermediate storage for samples that should not be spent directly in the cold chamber. The intermediate storage can be active, z. B. by a cooling device, cooled and / or passively by cold, flowing from the cold chamber and collecting in the interim storage, gas tempered.

In the device according to the invention, sensors, in particular temperature sensors, but also sensors for measuring volume flows, pressures and other physical quantities, may be present and connected to a controller in a signal-conducting manner. The controller can also be connected to cooling devices in the cold and / or lock chamber, with the first and second shutters and / or with the device for influencing the temperature in the lock chamber and drive them.

By this device, two cooling gas volumes are created, which communicate with each other and their respective vertical extent by defined heat input in each case a temperature profile is adjustable, which is largely independent of the temperature profile of the other volume.

The device uses the known fact that with increasing temperature decrease, the density of a cooling gas increases. If a cooling gas volume is not circulated or in any other way prevents the formation of a stratification, the coldest portions of cooling gas accumulate near the bottom during the The warmest portions of the cooling gas can be found in the layers that are vertically farthest from the earth's surface. It comes to the application of the device, in particular the formation of layers of different temperature, contrary, that gases have a low thermal conductivity, so that after formation of stable layers temperature profiles with steep temperature gradients, ie with high temperature differences over short distances can be generated.

When using the device according to the invention, the temperature in the cold chamber is lowered by the action of a cooling gas. The first volume contained in the cold chamber cools down and becomes denser.

The first volume passes as a directed volume flow through the first access into the lock chamber. The lowest temperature in the lock chamber is determined by the temperature of the layer which flows over the lower edge of the first access from the cold chamber into the lock chamber.

Over the range of the vertical extent of the first access, stratification takes place with stable and balanced pressure ratios between the two volumes, the temperature profile of which is the same in both volumes.
Such stratification prevents the emergence of unfavorable volume flows between the cold and lock chamber.

From the top edge of the first access, the temperature curves in both volumes can deviate again without influencing each other. This circumstance is used to create a temperature profile in the lock chamber in which those layers which lie in the area of the second access have temperatures above 0 ° C. The lying at the same horizontal height layers of the cooling gas in the cold chamber can therefore have significantly lower temperatures than in the lock chamber. Thus, for example, the second access may be located in a warm area, while the corresponding layers in the cold chamber still come to lie in a cold area.

For a first startup of the device, the cold chamber can be cooled and a volume flow can be generated by opening the two approaches, by which the temperatures are lowered in both volumes. The second access is then sealed gas-tight. It sets a pressure equilibrium between the two volumes and the volumetric flow succumbs. After the first access has also been closed, a temperature profile is created in the lock chamber, which includes a warm area in the adjacent to the second access layers.

If the device is to be loaded with samples, the second access is opened and the samples are placed in the lock chamber. The first access is meanwhile closed, whereby the formation of a volume flow between the cold chamber and lock chamber is prevented. The fact that the formation of turbulence and slightly occurring volume flows during the introduction of the samples can not be completely ruled out may even be beneficial. Thus, a leaked through the second access cooling gas can be replaced.

The samples are placed in the lock chamber and the second access closed. Due to the existing passive and / or active measures, the desired temperature profile is set in the lock chamber. The samples are located in the layers with the lowest temperatures of the lock chamber.

Subsequently, the first access is opened and the samples by means of z. B. an intervention device in the cold chamber. The first access is closed and the samples can be manipulated in the cold chamber, stored and, if necessary, be discharged again.

It is possible by the device according to the invention in an extremely advantageous manner to produce in the warm area of the lock chamber temperatures that are higher than the temperatures of the cold chamber and at the same time to obtain a connection between the two. In addition, the heating of the cooling gas to a certain temperature allows the use of this temperature associated benefits without the adverse effects of adding other gases or mixtures. Thus, a temperature around the freezing point allows the use of simple and inexpensive sealing elements on the second access and at the same time obtain the advantages of the dry cooling gas in order to obtain, for. B. to prevent icing or corrosion. The device according to the invention allows access to cryogenic areas while avoiding disadvantageous icing and high cooling losses.

About measuring devices, it is possible to control with information z. B. to actual conditions such as temperatures, occurring flow rates and stability of the stratification and, if necessary, to effect a control reaction to maintain the desired cooling conditions.

The invention will be explained in more detail with reference to embodiments and drawings.

Fig. 1

eine erste Ausführung der erfindungsgemäßen Vorrichtung im Schnitt und

Fig. 2

eine zweite Ausführung der erfindungsgemäßen Vorrichtung im Schnitt.

In the accompanying drawings show

Fig. 1

a first embodiment of the device according to the invention in section and

Fig. 2

a second embodiment of the device according to the invention in section.

In a first embodiment are according to Fig. 1 a cold chamber 1 with a first volume 2, a lock chamber 7 with a second volume 6, a first access 3 with a first closure 10 and a second access 12 with a second closure 14 to recognize as essential components. A wall 4 of the cold chamber 1 and a wall 5 of the lock chamber 7 are designed to be thermally insulated.

A device, not shown, for low-turbulence introduction of the liquid nitrogen having a temperature of -196 ° C as the cooling gas is arranged in this embodiment at the bottom of the cold chamber 1. In other arrangements of such a device, the cooling gas can be supplied to the wall 4 of the cold chamber 1. The pressure generated by the cooling gas is 30 pascals higher than the pressure Ambient pressure outside of cold chamber 1 and lock chamber 7. In the wall 4 of the cold chamber 1, an engagement device 8 in the form of thermally insulated gloves and a window inspection window 9 through which a person using the engagement device 8 can look into the cold chamber 1. The first shutter 10 is arranged as a manually operated slide. The first closure 10 is not gas-tight and therefore allows a small gas exchange between the first volume 2 and the second volume 6 even in the closed state. The vertical extent of the first access 3 begins with a small distance above the bottom of the cold chamber 1. The vertical extent of the first access 3 is dimensioned smaller than the vertical extent of the lock chamber 7. The bottom of the lock chamber 7 is horizontally level with the ground an insulation 11 of the walls 5 decreases in the vertical direction, whereby the heat transfer coefficient increases in the vertical direction. How out Fig. 1 can be clearly seen, the region of the decreasing insulation 11 begins above the first access 3. At the upper end of the lock chamber 7 is the second access 12, to which a seal 13 and formed as a manually operable lid second closure 14 are present. The second closure 14 is mounted inclined to the horizontal and covers the entire elevation of the lock chamber 7. In the closed state of the second closure 14 is firmly against the seal 13 and provides a gas and pressure-tight separation of the second volume 6 from the environment of the device forth ,

Above the first access 3, a heater 15 is arranged in the second volume 6, which is connected to a controller 16. The controller 16 is also connected to a device for low-turbulence introduction liquid nitrogen and a respective temperature sensor 17 in the cold chamber 1 and the lock chamber 7. The compounds are not shown for reasons of clarity.

The vertical temperature profile in the cold chamber 1 ranges from -196 ° C in the cold range 18 to + 20 ° C in the hot area 19. In the lock chamber 7 corresponds to the lowest temperature in the cold region 18 of the temperature of that layer extends directly over the lower edge of the first access 3, while in the hot area 19 of the second access 12 rule around + 10 ° C.

The first closure 10 can also be actuated hydraulically, pneumatically or electrically in further embodiments. It can also be designed hinged as a door, as a slide, cover or as a straight line in and out of the first access 3 to moving plug.

Likewise, the actuation of the second closure 14 can also be effected electrically, pneumatically or hydraulically. The second closure 14 may be realized in other embodiments as a door, slide or plug.

In further embodiments, the second access 12 may be arranged horizontally and / or extend over partial areas of the tear surface of the lock chamber 7. In addition, the insulation 11 of the wall 4 of the cold chamber 1 in the vertical direction decrease and thereby the formation of the hot area 19 are supported.

In a further embodiment according to Fig. 2 the cold chamber 1 is articulated in an upper manipulation chamber 20 and a lower storage chamber 21. At the transition between manipulation chamber 20 and bearing chamber 21 is a cover 22 z. B. plastic, which serves as a work surface for manipulative activities and at the same time the spatial separation of manipulation chamber 20 and storage chamber 21. In the cover 22 a closable with a lid opening 23 is present. Under the cover 22, in the storage chamber 21, a cylinder rotatable about its vertical axis is arranged as a storage device 24. This has vertical radiographs arranged on a radius into which shelves with standardized styrofoam freezer boxes for receiving sample containers can be lowered and removed.

The vertical temperature profile in the storage chamber 21 ranges from about -196 ° C to -130 ° C. Above the cover 22 in the manipulation chamber 20, the temperatures of -130 ° C in the cold range 18 to + 20 ° C in the hot area 19 to.

The manipulation of the samples takes place in areas where temperatures are colder than -100 ° C, but can not thaw the goods to be chilled.

How out Fig.2 recognizable, in this embodiment, the lock chamber 7 has been increased downwards. Thus, an intermediate storage 25 is created by the samples can be initially stored without the risk of thawing. The intermediate storage 25 is tempered by cooling gas which flows through the first access 3 from the cold chamber 1 into the intermediate storage 25.

LIST OF REFERENCE NUMBERS

1

cold chamber

2

first volume

3

first access

4

wall

5

wall

6

second volume

7

lock chamber

8th

engaging device

9

window

10

first closure

11

isolation

12

second access

13

poetry

14

second closure

15

heater

16

control

17

temperature sensor

18

cold area

19

warm area

20

glovebox

21

storage chamber

22

cover

23

opening

24

bearing device

25

interim storage

Claims (10)

1. Device having a lock chamber and a cold chamber for adjusting cryogenic temperatures, wherein the cold chamber (1) encloses a first volume and a first inlet (3) is present in the heat insulated wall of the cold chamber, which first inlet (3) connects the first volume with a second volume of the heat insulated lock chamber (7), wherein the lock chamber (7) has a second inlet (12), via which the second volume communicates with the external environment when the second inlet is open, and the temperatures in the cold chamber (1) and the lock chamber (7) are adjusted by the effect of a cold or evaporating cooling gas, wherein

   - the first inlet (3) has a vertical extension which is less than the vertical extension of the lock chamber (7),

   - a first closure (10) is associated with the first inlet (3) and a second closure (14) is associated with the second inlet (12),

   characterized in that

   - the second inlet (12) is arranged above the first inlet (3) and

   - means for adjusting stable vertical temperature stratification are present in the second volume (6), by which a temperature curve is adjustable over the vertical extension of the second volume (6) by a defined heat input, wherein the temperature is higher than 0 °C in the region of the second inlet (12).
2. Device according to claim 1, characterized in that the second closure (14) has a sealing (13), so that the second volume (6) can be closed with respect to the environment in a gas-tight and pressure-tight manner.
3. Device according to claim 2, characterized in that the means for adjusting stable vertical temperature stratification is a decreasing insulation (11) of the wall (5) of the lock chamber (7) beginning above the first inlet (3), so that the wall (5) of the lock chamber (7) has an increasing heat transmission coefficient over its vertical run upwards.
4. Device according to claim 2 or 3, characterized in that the dew point is below the outer surface of the wall (5) of the lock chamber (7).
5. Device according to claims 1 to 4, characterized in that there is a heating (15) in the second volume (6) above the first inlet (3), which heating (15) is connected to a control (16).
6. Device according to one of the preceding claims, characterized in that stable vertical temperature stratification with temperature curves in the range between -200 °C and +25 °C is present both in the first volume (2) of the cold chamber (1) and in the second volume (6) of the lock chamber (7) over the periods during which the second inlet (12) is closed, wherein the respective temperature curves are adjustable largely independently of one another.
7. Device according to one of the preceding claims, characterized in that inspection glasses (9) are present in the wall (4) of the cold chamber (1) and/or the wall (5) of the lock chamber (7).
8. Device according to one of the preceding claims, characterized in that at least one intervention device (8) is arranged in the wall (4) of the cold chamber (1) and/or the wall (5) of the lock chamber (7), by which intervention device (8) targeted manipulative acts can be performed in the first and/or second volume (2, 6).
9. Device according to one of the preceding claims, characterized in that the cold chamber (1) consists of at least one manipulation chamber (20) with the first inlet (3) and at least one storage chamber (21) located in vertical direction below the manipulation chamber (20).
10. Device according to one of the preceding claims, characterized in that the lock chamber (7) has a space formed as an intermediate storage (25) below the lower edge of the first inlet (3).

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