GB2489568A

GB2489568A - Cascade Cooling Arrangement with Controllable Evaporation Temperature

Info

Publication number: GB2489568A
Application number: GB1204856.7A
Authority: GB
Inventors: Franco Sestito; Markus Mayer
Original assignee: Bruker Biospin SAS
Current assignee: Bruker Biospin SAS
Priority date: 2011-03-25
Filing date: 2012-03-20
Publication date: 2012-10-03
Anticipated expiration: 2032-03-20
Also published as: DE102011006174A1; DE102011006174B4; GB201204856D0; GB2489568B; US20120240610A1

Abstract

A cooling arrangement for cooling a test sample has at least two cascade cooling stages, each includes at least one coolant line, one compressor 1.1, 2.1, one relief throttle 1.5, 2.5, 2.6, one evaporator 6, 7 and one liquefier / condenser 3, 6. The coolant line is divided into at least two partial lines â Aâ & â Bâ between the compressor and the liquefier / condenser 6 of the last cascade cooling stage, and at least all but one of the partial lines can be blocked individually and independently of each other by means of a valve 2.7, 2.8, Each partial line has its own relief throttle, and the partial lines both connect to the evaporator of the last cascade cooling stage. Since the valves are positioned in the relatively warm refrigerant line between the compressor and the liquefier / condenser, in use, there is no requirement for valves to operate at a relatively low temperature, such low-temperature valves being both complex and expensive.

Description

COOLING DEVICE WITH CONTROLLABLE EVAPORATION TEMPERATURE

The invention concerns a cooling device for cooling a test sample, comprising at least two cascade cooling stages, each comprising at least one coolant line, one compressor, one relief throttle, one evaporator and one liquefier.

Devices having such properties include the device NMR9O of the company Millrock Technology, Kingston, NY, USA, the device ULSP9O of the company ULSP by, Ede, NL and the device FTS XR Air Jet of the company RototecSpintec GmbH, Biebesheim, Germany.

Various analysis methods require cooling of the samples to be analyzed. In specific cases, such as nuclear magnetic resonance spectroscopy or X-ray crystallography, this is often achieved by introducing the sample into a cold gas flow, advantageously nitrogen or helium.

This cold gas flow may be realized, for example, through evaporation of liquid gases or cooling a warm gas using heat exchangers that are immersed into liquefied gas. Provision or generation and storage of these liquefied gases requires complex logistics.

The warm gas may alternatively also be cooled using a coolant cycle process. In a cycle process, a suitable coolant is compressed in a compressor to a higher pressure and is thereby heated, then cooled (desuperheated) in a heat exchanger to a temperature below the liquefaction temperature that prevails at the obtained pressure, thereby dissipating heat, is further liquefied, thereby dissipating further heat, is relieved by a suitable throttle to a lower pressure, and evaporated again in a second heat exchanger, thereby absorbing heat from the gas to be cooled at the low evaporation temperature.

There are conventional configurations of coolant cycle processes with adjustable evaporation pressure and adjustable throttle between the first heat exchanger (coolant liquefier) and second heat exchanger (coolant evaporator) in order to adjust the desired cooling temperature. Such a configuration is technically complex when the cycle process to be varied is already operated in a cascade of cycle processes at a very low liquefaction temperature and the adjustable throttle consequently also becomes very cold.

For this reason, it is current practice to largely do without adjustment of the desired coolant temperature. This applies to the devices of the companies Bruker (type "BCU-X"), ULSP type "90 Immersion Probe Cooler", and Milrock type "NMR9O sample cooler". In an ahcrnative fashion, the gas flow that has been cooled to a predetermined temperature is heated to a desired higher temperature by means of an installed heating device. One example therefore are the devices of the company RototecSpintec FTS "XR Air-Jet Cooler".

It is the underlying purpose of the present invention to provide a simple way of adjusting the cooling temperature without using valves that must be adjusted in a cold state, since these are complex and expensive.

This object is achieved in a surprisingly simple and yet effective fashion in that the coolant line is divided into n partial lines between the compressor and the liquefier of the last cascade cooling stage, wherein n ? 2, the divided n partial lines can be blocked individually and independently of each other by means of at least n-i valves, the divided partial lines each comprise their own relief throttle, and the divided partial lines are both connected to the evaporator of the last cascade cooling stage.

In the inventive cooling device, the compressed coolant is divided into two or more parallel paths upstream of the first heat exchanger (liquefier) and guided in this fashion through the liquefier, through a separate respective throttle and to the second heat exchanger (evaporator). When the individual paths are selectively individually blocked by the valves thereof one obtains an overall adjustable throttle effect. 2"-l different throttle effects can be adjusted for n valves when the individual throttles are properly dimensioned. At least one valve has to be open at any time, and for this reason, one valve can be omitted. One then obtains 2' different throttle effects with n valves and n+1 coolant paths with each throttle.

The coolant is evaporated, thereby providing the desired cooling power in the second heat exchanger at the evaporation temperature of the coolant at this influenceable pressure, and for this reason, the cooling temperature can also be influenced.

In contrast to the conventional devices, the throttles of this device need not be adjustable themselves, which could be realized only with great technical expense in a cascade of cycle processes of a cycle process to be varied with a very low liquefying temperature and therefore low throttle temperature.

One particularly preferred embodiment of the inventive cooling device is characterized in that the divided partial lines are guided in parallel through the liquefier.

One further advantageous embodiment is characterized in that the evaporator of the last cascade cooling stage is designed as a heat exchanger, a gas to be cooled enters the heat exchanger through a gas inlet, dissipates heat and exits the heat exchanger again through a gas outlet, and the cooled cooling gas is guided to the test sample for cooling it. With this design, the heat exchanger is simultaneously the transfer line for the cooling gas and the device can be designed in a simple and space-saving fashion.

The invention is particularly advantageous when the cooling device is part of a nuclear magnetic resonance spectroscopy apparatus, in which the cooled gas flow is heated to the desired temperature and higher temperatures can be achieved with less cooling and therefore also less heating, which simplifies control.

The inventive cooling device may alternatively also be part of an X-ray spectroscopy apparatus. In particular, X-ray crystallography often requires cooling of the test samples.

The inventive cooling device is alternatively also advantageously part of an EPR apparatus.

Further advantages of the invention can be extracted from the description and the drawing.

The features mentioned above and below may be used individually or collectively in arbitrary combination. The embodiments shown and described are not to be understood as exhaustive enumeration but have exemplary character for describing the invention.

The invention will be further described with reference to a preferred embodiment, as shown in the drawings in which: Fig. 1 shows a schematic view of an embodiment of the inventive cooling device.

The cooling device shown by way of example in Fig. 1 includes a first cascade cooling stage with compressor 1.1, safety pressure switch 1.2, filter 1.3, relief throttle 1.5, and pressure compensating vessel 1.4, and also a second cascade cooling stage with compressor 2.1, safety pressure switch 2.2, filter 2.3, and pressure compensating vessel 2.4.

A combined air heat exchanger with fan 5 is e.g. used as liquefier 3 for the first cascade cooling stage and as desuperheater 4 for the second cascade cooling stage.

A heat exchanger 6 is used as evaporator for the first cascade cooling stage and as liquefier for the second cascade cooling stage.

A heat exchanger 7, illustrated by way of example as transfer line, is used as evaporator for the second cascade cooling stage to provide the desired cooling power in that a gas to be cooled is guided from the inlet 7.1 to the outlet 7.2.

Downstream of the compressor 2.1 of the second cascade cooling stage, the coolant line of the illustrated embodiment is divided into two partial lines A, B. These are guided in parallel through the heat exchanger 6 downstream of the respective valves 2.7, 2.8. Each of the partial lines A, B, has its own relief throttle 2.5, 2.6. The two partial lines A, B, are subsequently guided into the heat exchanger 7. The evaporation temperature can then be controlled via connecting or disconnecting a partial line A, B, by means of the valves 2.7, 2.8.

Although the invention is illustrated above by means of a cooling device in accordance with the principle of a compression cooling machine with two-stage cooling cascade, adjustment of the evaporation temperature by dividing the coolant path upstream of the first heat exchanger into two or more paths is also possible with one-stage cooling devices according to this principle and also with cooling cascades with more than two stages.

S

List of Reference Numerals 1.1 compressor of the first cascade cooling stage 1.2 safety pressure switch thereof 1.3 filter thereof 1.4 compensating vessel thereof 1.5 relief throttle thereof 2.1 compressor of the second cascade cooling stage 2.2 safety pressure switch thereof 2.3 filter thereof 2.4 compensating vessel thereof 2.5 relief throttle A thereof 2.6 relief throttle B thereof 2.7 valve to the relief throttle A thereof 2.8 valve to the relief throttle B thereof 3 liquefier of the first cascade cooling stage 4 desuperheater of the second cascade cooling stage S fan for liquefier 3 and desupercooler 4 6 heat exchanger as evaporator of the first cascade cooling stage and liquefier of the second cascade cooling stage 7 heat exchanger as evaporator of the second cascade cooling stage for providing the cooling power by cooling a gas 7.1 entry of the gas to be cooled 7.2 exit of the cooled gas

Claims

Claims 1. A cooling device for cooling a test sample, comprising at least two cascade cooling stages, each comprising at least one coolant line, one compressor, one relief throttle, one evaporator and one liquefier, characterized in that the coolant line is divided into n partial lines between the compressor and the liquefier of the last cascade cooling stage, wherein n? 2, and wherein the divided n partial lines can be blocked individually and independently of each other by means of at least n-i valves, the divided partial lines each have their own relief throttle, and the divided partial lines are both connected to the evaporator of the last cascade cooling stage.
2. A cooling device according to claim i, wherein the divided partial lines are guided in parallel through the liquefier.
3. A cooling device according to any one of the preceding claims, wherein the evaporator of the last cascade cooling stage is designed as a heat exchanger, a gas to be cooled enters the heat exchanger through a gas inlet, dissipates heat and exits the heat exchanger again through a gas outlet, and the cooled cooling gas is guided to the test sample for cooling it.
4. A cooling device according to any one of the claims i through 3, wherein the cooling device is part of a nuclear magnetic resonance spectroscopy apparatus.
5. A cooling device according to any one of the claims i through 3, wherein the cooling device is part of an X-ray spectroscopy apparatus.
6. A cooling device according to any one of the claims 1 through 3, wherein the cooling device is part of an EPR apparatus.
7. A cooling device with controllable evaporation temperature substantially as hcrcinbcforc described with reference to and as illustrated by the accompanying drawings.