Refrigeration – Gas compression – heat regeneration and expansion – e.g.,...
Patent
1992-08-20
1994-06-07
Bennett, Henry A.
Refrigeration
Gas compression, heat regeneration and expansion, e.g.,...
62 511, 62 512, F25B 1902
Patent
active
053178785
DESCRIPTION:
BRIEF SUMMARY
This invent on relates to cryogenic cooling apparatus.
There are numerous scientific, technological and industrial situations in which a need for cryogenic cooling arises. For example, the performance of many detector devices used for the detection or measurement of very small incident signals is enhanced by reducing the detector-device temperature so as to achieve an improved signal-to-noise ratio. Such cooling has been accomplished in the past by the use of stored, solid or liquid cryogens, but such systems have a limited life and a large mass which makes them unsuitable for use in, for example, cooling the detector devices of measuring apparatus carried aboard space probes or earth satellites. Increase in the useful lifetime without undue increase in the overall mass may be achieved by employing a closed cycle cooling system in which the cryogenic working substance, instead of being used "once through" and then exhausted, is recycled indefinitely; and solar-powered electrically-driven Stirling-cycle refrigerators using helium as their cryogenic working fluid have indeed been developed for such purposes. A single-stage Stirling-cycle refrigerator is capable of achieving temperatures down to about 80.degree. K., but for many applications lower temperatures are desirable or necessary. A two-stage Stirling-cycle refrigerator capable of achieving temperatures below 20.degree. K. and of producing 200 mW of refrigeration at 30.degree. K., with an operating frequency of about 35 Hz and an electrical driving power input of some 90 watts, has recently been described by the inventors of the present invention (Bradshaw, T.W. and Orlowska, A.H.: Proceedings of the 3rd European Symposium on Space Thermal Control and Life Support Systems: ESA SP-288 (1988)); but a Stirling-cycle machine and, indeed, any regenerative-cycle machine, must become increasingly inefficient at very low temperatures due, mainly, to decreasing regenerator effectiveness.
In order to reach very low temperatures (around 4.degree. K.) it is therefore necessary in practice to introduce a non-regenerative cooling stage, and it is known in this context to make use of the Joule-Thomson (J-T) expansion effect, namely that a gas, under high pressure and at a temperature below its inversion temperature, becomes cooled when it is allowed to expand through a flow constrictor to a lower pressure. However, the inversion temperatures of many gases, including helium, are well below ordinary room temperature, and therefore they must first be precooled before they can be further cooled by use of the J-T effect. The required precooling may be effected by means of any suitable refrigerating apparatus, which may, for example, be a Stirling-cycle refrigerator such as one of those referred to above.
The present invention relates, therefore, in one of its aspects, to a multi-stage cryogenic cooling apparatus having a closed-loop J-T expansion stage and at least one pre-cooler stage, the J-T stage comprising a gas compressor, a J-T expansion chamber (having an outlet connected to the compressor via a low-pressure return line and an inlet arranged to receive high pressure gas via a high-pressure line from the compressor and constituted as a flow-restricting expansion valve therefor), and a J-T stage heat exchanger in which the high-pressure supply line and the low-pressure return line are in heat-exchanging relationship, and the precooler stage being arranged to pre-cool gas in the high-pressure supply line before it enters the J-T stage heat exchanger. Such a cryogenic cooling apparatus is referred to hereinafter as apparatus of the defined kind.
In such apparatus of this defined kind, high pressure gas from the compressor is precooled by the precooler stage before passing, via the J-T stage heat exchanger, to the flow-restricting expansion valve through which it expands into the expansion chamber with the effect of cooling both itself and the expansion chamber. The resulting low-pressure gas, now at the lowest temperature in the whole system, returns from the expansio
REFERENCES:
patent: 1829096 (1931-10-01), Kramer
patent: 3125863 (1964-03-01), Hood, Jr.
patent: 3375675 (1968-04-01), Trepp et al.
patent: 3415077 (1968-12-01), Collins
patent: 3656313 (1972-04-01), Low et al.
patent: 3802211 (1974-04-01), Bamberg et al.
patent: 4077231 (1978-03-01), Fletcher et al.
patent: 4223540 (1980-09-01), Longsworth
patent: 4567943 (1986-02-01), Longsworth et al.
patent: 4606201 (1986-08-01), Longsworth
patent: 4766741 (1988-08-01), Bartlett et al.
patent: 4840043 (1989-06-01), Sakitani et al.
patent: 5060481 (1991-10-01), Bartlett et al.
T. W. Bradshaw et al.: "A 4-K mechanical refrigerator for space applications" pp. 393-397; FIGS. 4, 5 cited in the application unknown.
Bradshaw Thomas W.
Orlowska Anna H.
Bennett Henry A.
British Technology Group Ltd.
Kilner Christopher B.
LandOfFree
Cryogenic cooling apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Cryogenic cooling apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Cryogenic cooling apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-785486