Patent ID: 12196471

MODES FOR CARRYING OUT THE INVENTION

Definitions

A “low-temperature storage device” is a storage device adapted to store objects at temperatures below 0° C., in particular below −20° C., advantageously below −60° C.

A “heat pump” moves thermal energy in the opposite direction of spontaneous heat transfer by absorbing heat from a cold space and releasing it to a warmer one. Advantageously, a heat pump is a device having a condenser, an expansion valve, an evaporator and a compressor, with the compressor pumping a fluid to the condenser (which is heated), through the expansion valve, through the evaporator (which is cooled), and back to the compressor.

In the present context, heat pumps are used for cooling purposes.

Overview:

An embodiment of a storage device is shown inFIGS.1and2. The basic set-up of the storage device corresponds to the one disclosed in EP 2 998 669.

The storage device comprises a storage chamber1enclosed by vertical insulating side walls2a, an insulating ceiling2band an insulating floor2d.

A transfer chamber3(FIG.1) may be located adjacent to storage chamber1and shares at least one of the insulating side walls2awith storage chamber1. In the embodiment ofFIG.1, transfer chamber3is divided into two sub-chambers3a,3bwith a separating wall4having a lock door5arranged between them, but transfer chamber3can also be a single chamber.

A door6provides user access to transfer chamber3. In the embodiment ofFIG.1, stairs7lead up to door6because transfer chamber3is above the level of bottom wall2dof the device. For the same reason, transfer chamber3is supported by struts8at its bottom side.

A refrigerator device10is provided to cool storage chamber1to a storage temperature below 0° C., in particular below −20° C., and in the second aspect of the device below −80° C. Details of the temperatures within storage chamber1follow below.

Refrigerator device10also cools transfer chamber3to a transfer temperature below 0° C., in particular to approximately −20° C.

Advantageously, the air in transfer chamber3is cooled and dried such that it has a low dew point, in particular below −30° C.

First Embodiment

The storage chamber1shown here is of cuboid shape. As best seen inFIG.2, it is divided into a bottom section11and a top section12. Top section12comprises typically 50-70% of the volume of storage chamber1, and bottom section lithe rest.

Top section12is located vertically above bottom section11.

Bottom section11holds a cassette store14formed by a grid15located at the top of bottom section11. Grid15forms an array of rectangular apertures16. Each rectangular aperture16forms a cassette location for receiving a storage cassette.

An example of a storage cassette17is shown inFIG.5. It comprises two vertical sidewalls20, with ledges21formed thereon. The ledges21form a plurality of storage locations22above each other for receiving the objects to be stored. At its top end, the storage cassette17comprises an insulating head section23. The head sections23of all storage cassettes17inserted into cassette store14form an insulating wall between bottom section11and top section12of storage chamber1, thereby helping to maintain a more constant temperature in bottom section11where most of the objects are stored.

A metal plate24or a mechanical coupling member24′ (shown in dotted lines) is located at the top of each storage cassette17. It is used for gripping the storage cassettes as described in EP 2998669.

The individual cassette locations or apertures16in cassette store14have a size fitting the footprint of the storage cassettes17to be received. There may be differently shaped apertures16to receive differently shaped storage cassettes, such as cassettes having the SBS footprint of 134×86 mm and/or cassettes having a “cryobox” square footprint of 137×137 mm.

As best seen inFIGS.3and4, bottom section11is divided into several storage zones. In the embodiment ofFIGS.2and3, there is a first storage zone101surrounded by a second storage zone102.

A first insulating wall111separates first storage zone101from second storage zone102.

Second storage zone102surrounds first storage zone101in all horizontal directions. Insulating wall111is arranged vertically between them.

As explained above, the temperature T1in first storage zone101is lower than the temperature T2in second storage zone102.

For example, the temperature T1in first storage zone101is advantageously below −80° C. In particular, it is smaller than −110° C., in particular smaller than the glass transition temperature of water, i.e. smaller than −130° C.

The temperature T2in second storage zone101is advantageously below −60° C., in particular between −100° C. and −60° C. Other temperature regimes are possible. However, the first temperature T1is advantageously at least 10° C. below second temperature T2.

As described above, this design reduces the flow of heat from the environment into first storage zone101and therefore makes the storage device more energy efficient.

As shown inFIG.3, when seen from above, first insulating wall111is arranged in a square, which minimizes (for a four-fold symmetry) the surface to volume ratio. As mentioned above, any other regular polygon shape or a circle can also be used to optimize that ratio.

FIG.4shows that second storage zone102has a bottom insulation2d. First storage zone101has a bottom insulation2eof its own, sitting on top of bottom insulation2d. Thus, the total bottom insulation below first zone101is thicker than below second zone102.

Hence, if the top of bottom section11is to be at the same height over first and second zone101,102, longer storage cassettes17can be used in second zone102in order to fully exploit the available space.

Cassette Handler:

As best seen inFIG.2, an automated cassette handler25is located in top section12of storage chamber1. It comprises a cassette lift26adapted to move an individual storage cassette17between its cassette location in cassette store15and top section12. Further, cassette handler25comprises a cassette holder, which is advantageously formed by cassette lift26, for holding a raised cassette in top section12of storage chamber1.

Cassette lift26, or at least the cassette holder, is arranged on a transport mechanism27a,27b, which is adapted to horizontally displace the cassette holder with a raised cassette, between a position where the raised cassette is vertically above its cassette location to a transfer station29having a transfer opening30(seeFIGS.6and7).

In order to provide enough room for an upright storage cassette17as well as the overhead required by cassette handler25, top section12of storage chamber1is advantageously somewhat higher than bottom section11.

Transport mechanism27a,27bcomprises a horizontal beam27aspanning storage chamber1and being held at opposite ends by rails27b. Beam27ais located at the top of top section12. Cassette lift26is suspended from beam27a. A displacement drive is provided for horizontally displacing beam27aalong the rails27b, and also for horizontally displacing cassette lift26along beam27a.

The design of cassette lift26can e.g. correspond to the one shown in EP 2998669 as described in reference toFIGS.5and9-13of that document.

Transfer Station:

Transfer station29is shown inFIGS.6and7. It comprises a transfer opening30arranged in a vertical side wall31of top section12.

In contrast to the design of EP 2998669, transfer opening30has a height H of less than three times the height h of one of the storage locations22, in particular of less than two times the height of one of the storage locations.

In specific numbers, height H may be less than 50 cm, in particular less than 20 cm.

Further, transfer opening30may have a width W of less than two times the width w of the storage locations22.

Using such a small transfer opening30in an otherwise closed wall30has the advantage of reducing heat and gas exchange when accessing the stored object. It also reduces the risk of accessing the wrong object.

Since transfer opening30has a height much smaller than the total height of a storage cassette17, cassette handler26is programmed to vertically displace cassette17in transfer station29in order to position any desired storage location22next to transfer opening30.

As is best seen inFIGS.3and7, the storage device can comprise a pit33at transfer station29. Pit33is located in bottom section11and positioned and sized to receive the bottom end of a storage cassette17in transfer station29, such that all of the cassette's storage locations22can be positioned next to transfer opening30.

Pit33is open at its top but it may be insulated against the storage zones.

Transfer opening30may be equipped with an automated door34for closing in when not used. In addition or alternatively thereto, a manually operatable door35may be provided.

Refrigerator Device:

FIG.8shows a first embodiment of refrigerator device10. It is adapted and structured to maintain the temperatures T1and T2in the various storage zones of the storage device.

In the shown embodiment, refrigerator device10advantageously comprises several heat pumps40a,40b,40carranged in series, with the condenser41aof the first heat pump40abeing cooled e.g. by means of environmental air or cooling water, and its evaporator41bcooling the condenser42aof the next heat pump40betc., thus generating a series of temperature levels T1(coldest) through Tn (with n>1 being the number of heat pumps and n=3 inFIG.8).

The evaporator43bof the last heat pump may be used to cool the first storage zone101, while the evaporator42bof the second last heat pump may be used to cool the second storage zone102, etc.

In the embodiment ofFIG.8, a first storage-cooling heat exchanger44may be arranged in first storage zone101, a second storage-cooling heat exchanger45amay be arranged in second storage zone102, and a third storage-cooling heat exchanger45bmay be arranged in transfer chamber3. Heat transfer devices46,47a,47bmay be provided to transfer heat from the storage-cooling heat exchangers44,45a,45b, respectively, to the various parts of refrigerator device10.

The storage-cooling heat exchangers44,45a,45bcan e.g. be designed as liquid-air exchangers or radiators cooling the air in the various parts of the storage device. In addition, they can be used for drying the air, in particular in transfer chamber3.

The heat transfer device46coupling refrigerator device10to storage-cooling heat exchanger44in first zone is advantageously a refrigerant circuit, i.e. a circuit where a cryo-liquid, in particular argon or nitrogen, is circulated, at least in part in its liquid, sub-critical phase.

More details about heat transfer devices based on the refrigerant circuit are provided below.

Alternatively, liquid gas, in particular liquid nitrogen, may be used to cool one or more of the storage zones101,102.

Second Embodiment

As mentioned, the invention is also directed to a storage device having a refrigerant circuit for cooling the first storage zone. This second aspect can be applied to the storage device shown above but also to other types of storage devices, e.g. also to storage devices having non-concentric storage zones or only a single storage zone.

Some further embodiments of the second aspect are described in the following.

FIG.9shows a second embodiment of a storage device with a storage chamber1and a refrigerator device10.

Storage chamber1has an outer region50(forming e.g. top section12and/or transfer chamber3in the embodiments above). Further, it comprises an inner region52(forming e.g. bottom section11in the embodiments above).

Outer region50reduces the transfer of humidity into inner region52, and it is e.g. maintained at a temperature of −10° C. to −40° C.

Inner region52comprises a first storage zone101for storing objects at a temperature T1below −80° C., in particular below −110° C., in particular below −130° C., e.g. at −150° C.+/−20° C.

Inner region52may also comprise a second storage zone102for storing objects at a higher temperature T2. Second zone102may horizontally surround first zone101, as in the first embodiment, but this is not strictly required in the second aspect of the present technique.

Refrigerator device10of the present embodiment comprises several heat pumps40a,40carranged in series.FIG.9shows two of them, but their number may be larger.

Same as in the embodiment ofFIG.8, the evaporator41bof one heat pump40ais used to cool the condenser43aof the next colder heat pump40c.

The evaporator43bof the last (i.e. the coldest) heat pump40cis thermally coupled to a refrigerant circuit46by means of a heat exchanger54.

Refrigerant circuit46at least comprises a duct section55in heat exchanger56, which is thermally coupled to evaporator43b, and the storage-cooling heat exchanger44.

In operation, the cryo-liquid is circulated in refrigerant circuit46to transfer heat from storage-cooling heat exchanger44to heat exchanger54, thereby cooling storage zone101.

In the shown embodiment, refrigerant circuit46is designed as a heat pump with a compressor58and an expansion valve60. Storage-cooling heat exchanger44forms an evaporator, and duct55in heat exchanger56forms a condenser for the cryo-liquid. The cryo-liquid is in its sub-critical, liquid state at least on its path from heat exchanger56to expander or throttle60.

Advantageously, an expansion vessel61is provided in refrigerant circuit46. It is designed to receive cryo-liquid in case the temperature in the refrigerant circuit is high, e.g. when the storage device is not in operation.

In operation, first heat pump40amay e.g. have a temperature between −10° C. and −40° C. at its cold side, i.e. at its evaporator41b.

Heat exchanger T1is coupled to a cooling device45bby means of a heat transfer device47b. Heat transfer device47bmay e.g. be a liquid circuit with a suitable pump.

Heat exchanger T1is also coupled to evaporator43aof heat pump40c, which can e.g. use methane (R50), which evaporates at a temperature below −160° C. Methane is advantageous not only because of its low boiling point but also because it can be used as a heat pump fluid over a large temperature difference.

Heat pump40cmay e.g. also use ethane or another liquid. Suitable liquids are typically flammable.

Methane and ethane are environmentally friendly. However, flammable liquids should not be used in closed, poorly aired spaces, such as in first storage zone101. However, refrigerant circuit46allows to design the cooling system without ethane or methane entering the storage zone.

In the embodiment ofFIG.9, only two heat pumps40a,40care arranged in series. There may, however, also be more heat pumps. In that case, further temperature levels may be available for selectively cooling e.g. second storage zone102and/or other parts of storage chamber1.

Instead of or in addition to using a plurality of heat pumps in series, refrigerator device10may also comprise a heat pump using mix of several fluids having different boiling points and with liquid/gas separators in order to generate different temperature levels as known to the skilled person.

Third Embodiment

FIG.10shows a storage device similar to the one ofFIG.9. In this embodiment, however, refrigerator device10comprises an air cycle machine65having a compression turbine66and an expansion turbine68, e.g. driven by a common motor70. It further comprises one or more hot-side heat exchangers72,73between compression turbine66and expansion turbine68for cooling the air and at least one cold-side heat exchanger54arranged after expansion turbine68.

Cold-side heat exchanger54is again coupled to refrigerant circuit46.

The hot-side heat exchanger(s)72,73may be cooled e.g. by environmental air and/or water.

Advantageously, though, and as shown inFIG.10, the air from compression turbine66is first guided through first hot-side heat exchanger72, which is e.g. cooled by environmental air and/or water, and then though second hot-side heat exchanger73, which is cooled by a separate heat pump40a.

Heat pump40amay comprise condenser41acooled e.g. by environmental air and/or water and an evaporator41b. Evaporator41bis coupled to second hot-side heat exchanger73of air cycle machine65, which allows to reach lower temperatures at cold-side heat exchanger54.

In other words, refrigerator device10advantageously comprises a first heat pump40ahaving an evaporator41bthermally coupled to a hot-side heat exchanger73of air cycle machine65.

Advantageously, evaporator41bof heat pump40ais also coupled to at least one heat transfer device47a,47bfor cooling a part of storage device1to a temperature between −5° C. and −80° C., in particular between −10° C. and −40° C.

In operation, air is compressed by compression turbine66, cooled in the hot-side heat exchanger(s)72,73, and expanded in expansion turbine68. The cooled air after expansion turbine68receives thermal energy in heat exchanger54, whereupon it returns to compression turbine66.

As described above, air cycle machine65can be used for reaching very low temperatures, e.g. around −150° C.+/−20° C., at heat exchanger54.

Refrigerant circuit46is coupled to heat exchanger54.

Refrigerant Circuit

As mentioned above, the refrigerant circuit46is used to carry heat away from storage zone101.

As described above, refrigerant circuit46can be a heat pump evaporating the cryo-liquid in storage-cooling heat exchanger44.

Alternatively, the cryo-liquid in refrigerant circuit46may be circulated in its subcritical, liquid state by natural convection or by means of a pump, without a phase change taking place.

Advantageously, the temperature in refrigerant circuit46is below −80° C., in particular below −110° C., in particular below −130° C. On the other hand, it is advantageously above −180° C.

In particular, the temperature at first storage-cooling heat exchanger44in storage zone101is at −150° C.+/−20° C.

To keep the cryo-liquid in its liquid state, the pressure in at least part of refrigerant circuit46(namely at the parts where the cryo-liquid should be liquid) is advantageously at least 2 bar, in particular at least 5 bar, e.g. 10-30 bar, in particular when using argon or nitrogen as a cryo-liquid. In one embodiment, it is at 15+/−3 bar when operating at a cryo-liquid temperature of −150+/−4° C. In another embodiment, it is at 25+/−3 bar when operating at an cryo-liquid temperature of −140+/−3° C.

The storage device further comprises a control unit62(which is shown, by way of example, inFIGS.9and10), which is adapted and structured to operate refrigerator device10to maintain the parameters described here during operation of the storage device.

Notes:

In some of the embodiments of the first aspect described so far, there are two storage zones101,102. There may, however, also be more than two storage zones, e.g. at least three storage zones,101,102,103as shown inFIG.11. In this case, the third storage zone103horizontally surrounds the second storage zone102, and a second insulating wall112vertically separates the second and third storage zones102,103.

Refrigerator device10may control the third temperature T3in third storage zone103to be higher than the second temperature T2in second storage zone102. Advantageously, second temperature T2is at least 10° C. below third temperature T3.

In the embodiments of the first aspect as described above, second storage zone102horizontally surrounds first storage zone101. Alternatively, and as mentioned, second storage zone102may surround first storage zone101only partially.

The temperatures and pressures of the refrigerant circuit given above are particularly optimized for using argon as a cryo-liquid, but they can be easily adapted to e.g. nitrogen or another inert gas by using the material's phase diagram.

The storage device can be used to store a vast range of objects, such as chemical or biological samples. The objects may e.g. be tube holders (tube racks) or microtiter-plates, with each tube rack or microtiter-plate being stored in its own storage location22.

While there are shown and described presently preferred embodiments of the invention, it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied and practiced within the scope of the following claims.