Cooling device with controllable evaporation temperature

Abstract

A cooling device for cooling a test sample has at least two cascade cooling stages, each with at least one coolant line, one compressor (1.1, 2.1), one relief throttle (1.4, 2.4), one evaporator (6, 7) and one liquefier (3, 6). The cooling device has an additional relief throttle disposed between the evaporator (7) of the last cascade cooling stage and the compressor (2.1) of the last cascade cooling stage. This represents a simple possibility of adjusting the cooling temperature, thereby avoiding the use of valves that can be adjusted at low temperatures, since these are complex and expensive.

Description

[0001]This application claims Paris Convention priority of DE 10 2011 006 165.7 filed Mar. 25, 2011 the complete disclosure of which is hereby incorporated by reference.BACKGROUND OF THE INVENTION[0002]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.[0003]Devices having such properties are e.g. the device NMR90 of the company Millrock Technology, Kingston, N.Y., USA, the device ULSP90 of the company ULSP by, Ede, NL and the device FTS XR Air Jet of the company RototecSpintec GmbH, Biebesheim, Germany.[0004]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 (cooling gas), advantageously nitrogen or helium.[0005]This cold gas f...

AI Technical Summary

Benefits of technology

[0012]In contrast to the methods that are normally used, the throttle does not need to be adjustable itself, 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.

[0013]One further advantage of this invention results from the fact that, when a higher temperature and therefore higher evaporation pressure in the second heat exchanger is desired, the suction pressure in the compressor is lower due to the necessary increased decompression at the second throttle, which decreases the power input of the compressor. In contrast thereto, a throttle which is adjusted at a low temperature between the first and the second heat exchanger would entail a higher suction pressure and therefore higher power input of the compressor when adjusting a higher evaporation temperature with consequently reduced cooling power requirements.

[0014]One particularly advantageous embodiment is characterized in that the additional relief throttle is designed in two stages in the form of a parallel arrangement of a bypass valve and an invariable relief throttle. This provides a variable relief throttle with simple and inexpensive means.

[0016]One further advantageous embodiment is characterized in that the evaporator of the last cascade cooling stage is designed as a heat exchanger, a cooling gas 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.

[0017]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.

Problems solved by technology

Provision or generation and storage of these liquefied gases requires complex logistics.

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.

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