Refrigeration – Storage of solidified or liquified gas – Including cryostat
Reexamination Certificate
1999-04-01
2001-03-13
Doerrler, William (Department: 3744)
Refrigeration
Storage of solidified or liquified gas
Including cryostat
C062S397000, C062S529000
Reexamination Certificate
active
06199386
ABSTRACT:
This invention relates to the supply of a liquid, particularly but not exclusively a potable liquid such as a spirit drink, which has been chilled below ambient temperature and preferably below 0° C.
BACKGROUND OF THE INVENTION
There is a widespread need for many types of liquid to be supplied, or dispensed, at sub-ambient temperature. Much energy and expense is incurred in providing chilled drinks, such as by adding pre-formed ice or by chilling the bottle containing the drink. Such methods have significant disadvantages: ice tends to melt and so dilute the drink, and chilling the entire bottle is both time-consuming and inefficient.
BRIEF SUMMARY OF THE INVENTION
Accordingly, the present invention is predicated on the use of a cryogen to chill a liquid. The present invention also provides an apparatus for supplying a liquid comprising conduit means for bringing the liquid at or about ambient temperature into indirect thermal contact with a cryogen so as to chill the liquid below ambient temperature.
The term “cryogen” is used herein to denote those gases and gas mixtures which at ambient temperature and pressure are normally in gaseous form—air, nitrogen, oxygen, carbon dioxide and the like—but which are used in the liquid or solid state, as well as azeotropic mixtures such as solid carbon dioxide and acetone. Such substances are, in use, all at a temperature substantially below 0° C. (boiling point, at ambient pressure, of carbon dioxide being −78° C. and nitrogen −194.3° C.) and thus have considerable capacity to chill an equivalent volume of a liquid to sub-ambient temperature very quickly. In fact, the cooling rate achievable using such cold substances is so great that care has to be taken not to over-chill, or even freeze, the liquid. Thus, in the present invention, a degree of thermal separation between the cryogen and the liquid to be cooled is important, so as to prevent over-chilling. In the case of spirits for example (alcoholic drinks containing between about 35% and about 50% alcohol by volume), these are preferably chilled to about −5° C. before drinking; because of their alcohol content, spirits usually remain liquid at these temperatures and when drunk will give the drinker the frisson of frozen pleasure sought without being so cold as to damage the tissues of the mouth.
Preferably at least one conduit in thermal contact with the cryogen is provided each conduit being adapted to allow a throughflow of the liquid, or beverage, to be supplied, the liquid being in direct thermal contact with the conduit(s). This enables the high cooling rate of the cryogen to be used but enables over-chilling to be avoided.
Means may be provided to restrict the throughflow of liquid, so as to prolong the indirect thermal contact between liquid and cryogen, so as accurately to control the chilling of the liquid, according to its specific heat capacity, for example. This may be combined with means to supply a metered dose, or shot, of liquid for chilling, as is the norm for the commercial dispensing of spirits, for example.
The conduit(s) may be formed of a thermally-conductive material, and in relatively poor thermal contact with the cryogen. This allows rapid heat transfer between conduit(s) and liquid so as rapidly to chill the liquid by the desired amount without over-chilling, followed by the somewhat slower cooling of the conduit(s) through heat transfer with the cryogen. Clearly a cycle comprising the successive chilling of an amount of liquid, the removal of said liquid from the conduit(s) and the cooling of the conduit(s) to cryogenic temperature is envisaged, a cycle suited to the dispensing of shots of spirits.
The conduit(s) is/are preferably in indirect thermal contact with the cryogen. This permits a preferred arrangement whereby the cryogen is contained within a vessel, the or each conduit being disposed within a channel passing through the vessel and in use being disposed so as to pass through the cryogen. Those skilled in the art will begin to comprehend how such an arrangement will complement the usual “optics” used for dispensing some alcoholic beverages; as a shot of spirits is supplied to a channel, its throughflow is restricted for long enough for the cold channel to chill the spirit to about −5° C. (the specific heats of the channel and spirit resulting in this net temperature—which of course can be varied if seen as appropriate) whilst the heat transfer rate with the surrounding cryogen is insufficient to materially affect this. The shot of spirits then flows out of the channel (typically under gravity) at the desired temperature and the channel then gradually cools to cryogenic temperature so that a further measure of spirits can be chilled. For a typical shot of spirits to be cooled from ambient temperature to −5° C. requires about 1 kCal (4.186 kJ), so a channel of a thermally-conductive material such as plated copper, with silver or gold having a mass of about 0.12 kg would be required. In terms of heat flow, the spirits should flow through the channel in about 5 seconds and the time for the channel to recool would be about 30-40 seconds. This rate of recooling can be controlled by providing a preferential path for heat transfer of known thermal conductivity between the channel and the cryogen; a typical arrangement may comprise the thermally-conductive channel in direct thermal contact with a surrounding layer of known (relatively poor) thermal conductivity of particular area, which layer is in turn in direct thermal contact with either the cryogen itself or the surrounding walls of the vessel or bath containing the cryogen.
Those familiar with the characteristics of cryogens will realise that there are several features which lend themselves to embodiments which will be particularly advantageous in the milieu of commercial spirit dispensing (in bars). Each time that a channel is recooled there will be a corresponding burst of rapid cryogen vaporisation. This will usually result in a puff of fog which, using suitable lighting, could enhance the aesthetic appeal of the spirit chiller. Similarly, the boiling of the cryogen could present an aesthetic attraction in itself, if the cryogen container were transparent and suitably lit, and/or the cryogen itself tinted or coloured.
In practical embodiments of spirit chilling apparatus in accordance with the invention. a single cryogen-containing vessel could have a plurality of channels passing through it, each channel being for the throughflow of a different spirit, so preventing mixing of different spirits prior to discharge from the chiller, and enhancing hygiene. Alternatively, a number of channels may be dedicated to a particular spirit, thus maximising the area of thermal contact between channel and spirit for maximised chilling rate and corresponding boiling of cryogen for eye appeal.
For ease of cleaning the or each channel is suitably disposed within the vessel, and/or the vessel is advantageously configured such that, on tilting the vessel away from its usual in use position, the channel(s) is/are disposed above the surface of the liquid cryogen within the vessel. It will also be understood that means are preferably provided for preventing any convective flow of ambient air into the channel(s), since this would lend to the formation of frost and, ultimately, blockage thereof.
REFERENCES:
patent: 1591623 (1926-07-01), Hassensall
patent: 2313954 (1943-03-01), Mariani
patent: 4407356 (1983-10-01), DeLau
patent: 4599872 (1986-07-01), Rist
patent: 5009083 (1991-04-01), Spinos et al.
patent: 5142874 (1992-09-01), Maric
patent: 5427276 (1995-06-01), Knuettel et al.
patent: 5799506 (1998-09-01), Johansson et al.
Garrett Michael Ernest
Shervington Evelyn Arthur
Doerrler William
Pace Salvatore P.
The BOC Group plc
Von Neida Philip N.
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