Refrigeration – Processes – Circulating external gas
Patent
1996-11-27
1998-08-25
Kilner, Christopher
Refrigeration
Processes
Circulating external gas
622383, 62271, F25B 1702
Patent
active
057972729
DESCRIPTION:
BRIEF SUMMARY
This invention relates to dewatering of desiccant brines, utilising a vacuum technique in lieu of the conventional high energy heating.
BACKGROUND OF THE INVENTION
Air conditioners fall into two general categories, the first being of the so called refrigerative type which comprises a closed circuit of refrigerant and lubricant which is pumped by means of a reciprocating or scroll pump through a condenser wherein the refrigerant is mostly if not entirely converted to liquid, and is then expanded in an evaporator wherein the liquid converts back to gas, and thereby absorbs latent heat to provide the refrigeration. A coefficient of performance of about 3 is frequently achieved with such refrigerant type air conditioners, and they are in common use.
A much less expensive type is the evaporative cooler wherein water passes over an absorbent pad from which it is evaporated by a passage of ambient air, and is cooled. For relatively dry atmospheres, the coefficient of performance is very much greater than can be achieved with more expensive refrigerator type of air conditioners, and consequently there is much demand for such coolers. However, difficulties are encountered in the more humid climates, and no evaporation at all will occur when the humidity of the air is 100%. Furthermore, in climates where the humidity is high, although not as high as 100%, the addition of more water vapour to the air is not acceptable and in some instances there is a requirement for heat exchangers to separate the cooled but more humid air. However, because of the relatively small range of humidity within which evaporation can take place, the temperature differential of the evaporated and unevaporated air is small and as a consequence, heat exchangers if used need large surface areas. These problems have been very well recognised and much effort has been made to solve them, mainly through the use of desiccants. Hygroscopic material such as lithium bromide is very effective in absorbing moisture from the atmosphere, but whereas evaporation of moisture will result in cooling, condensation results in heating and in prior art evaporative air conditioners wherein desiccants first dry the air, it has been considered necessary to use additional heat exchangers. A common method of regeneration of desiccant is by the application of further heat (for example, gas flames) but this still further increases the energy input and further heat exchangers are required. Because of the bulk and cost of heat exchangers, some efforts have been made to utilise multiple stages of desiccants, and for example reference can be made to the U.S. Pat. No. 5,170,633, Kaplan. Reference can also be made to the U.S. Pat. No. 4,869,070, Assaf. Along with Albers (U.S. Pat. No. 5,097,668), these specifications contain the prior art which Applicant believes is the most relevant to this specification.
Further relevant prior art exists in the so called "water refrigerator". Water is said to be quite unsuitable for use in refrigerators of the type using closed circuits because firstly of its very low vapour pressure and secondly of its high specific volume at low temperatures. However, it is well recognised that it is possible to maintain a high degree of vacuum, and for example, at about 7.degree. C. (45.degree. F.) the vapour pressure is about 10 millibars (0.15 psi) and the corresponding specific volume of vapour is about 125 m.sup.3 per kilogram (2000 cubic feet per pound). This large volume requires removal of vapour if the evaporation is to be continuous, and in installations where water has been used as a refrigerant, such as vegetable cooling devices, vacuum pumps have been supplemented by refrigerant evaporators within a vacuum chamber which assist in condensation of the water vapour while still in the chamber. This invention utilises a vacuum dewatering technique, but without refrigeration. An alternative which has been considered but as far as is known to the Applicant has not been used, is use of high pressure steam discharging through a nozzle upstream from
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patent: 5092135 (1992-03-01), Cameron
patent: 5097668 (1992-03-01), Albers et al.
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F F Seeley Nominees Pty Ltd
Kilner Christopher
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