Refrigeration – Material cooling means including gas-liquid contactor
Reexamination Certificate
2001-11-27
2002-12-24
Jiang, Chen-Wen (Department: 3744)
Refrigeration
Material cooling means including gas-liquid contactor
C062S310000, C261S091000, C428S141000
Reexamination Certificate
active
06497111
ABSTRACT:
FIELD OF THE INVENTION
The invention relates firstly to a method for evaporating liquid, in which a hollow cylindrical drum, which is arranged in a housing and has a drum wall which comprise a liquid-absorbent material, is rotated about its cylinder axis which is arranged substantially horizontally, the drum being immersed in the liquid to be evaporated over part of its circumference, which liquid is situated in a trough which is arranged at the circumference of the drum, while a gas which takes up the evaporated liquid is conveyed in contact with the liquid-absorbent material.
BACKGROUND OF THE INVENTION
A method of this nature is described in DE-A-2 362 619.
The said publication describes a method of the type indicated above which is carried out in a device which operates in the manner indicated above and in which the drum comprises a liquid-absorbent wick-like material which can be moistened with a liquid, for example water, in order that, when air is passed through the wick material from the inside of the drum outwards, water can evaporate.
A method of this type has the drawback that, when water is taken up in the wick material, the pores become filled with water and the resistance to the flow of air increases rapidly.
Although the above publication states that, after it has been immersed in the water, the wick material is allowed to drip dry, it is nevertheless necessary to reckon with a considerable resistance to the flow of air.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a device of the type described above which does not present a drawback of this nature.
To this end, the method according to the invention is characterized in that the liquid-absorbent material delimits a large number of passages which extend across the thickness of the drum wall and the gas is conveyed through these passages.
In the present context, passages is understood as meaning openings with a cross section of considerable size with respect to the liquid-absorbent material included in the drum wall, as will be explained in more detail below.
Advantageously, the passages will extend substantially radially with respect to the axis of the drum; however, this is not imperative, since passages which run in a direction other than the radial direction will also be satisfactory, provided that they are sufficiently large.
With regard to the direction of gas flow inside the passages extending across the thickness of the drum wall, it is, of course, possible to select flow from the inside outwards and from the outside inwards; it is an attractive option for the gas to be supplied inside the drum and to flow through the passages to the space outside the drum.
Where the above text has referred to liquid and gas which takes up evaporated liquid, it will be understood that the method as described offers the possibility of evaporating a wide variety of liquids using an equally wide variety of gases.
However, many applications will involve the evaporation of water, while it is obvious to use air as the gas which takes up evaporated water.
Water and air are generally available in copious quantities, and these two media will be in widespread use in particular for industrial purposes; however, the invention is not limited to these two media. If, instead of water, another liquid is to be evaporated, it will at any rate be necessary to ensure that the liquid-absorbent material is able to absorb this other liquid and that the liquid-absorbent material is inert to the said liquid, i.e. is not chemically affected by this liquid.
In a first embodiment of the method according to the invention, it is used to cool process water which is fed into the trough and air from the environment is conveyed through the passages, and during rotation of the drum at least some of the process water which is absorbed by the water-absorbent material is evaporated, and in this way the temperature of the process water which remains therein and/or of the liquid-absorbent material is reduced, with the result that, during further rotation, the temperature of the process water in the trough is reduced as a result of the cooled remaining absorbed process water and/or the cooled liquid-absorbent material coming into contact with the process water in the trough.
Process water is generated in very considerable quantities in industry and considerable work is involved in suitably cooling such quantities of process water. In many cases, cooling towers are used, in which water drips downwards through a filling packing and air is passed through in countercurrent, in order to cool the process water through evaporation of water.
Cooling processes of this nature require large-scale plant which, furthermore, has the drawback of forming aerosols which are entrained in the gas flow and may reach the environment, which is undesirable for certain environmentally polluting types of process water.
The method according to the invention as described above makes process water cooling of this nature easy and, to do so, uses a plant of small dimensions. In the method according to the invention, the formation of aerosols is to a large extent prevented since there is no contact between a flow of air and water which is already finely dispersed.
The water is absorbed at the surface of the absorption material and will evaporate from this position; consequently, there is little likelihood of aerosols being formed. This embodiment of the method according to the invention will be explained in more detail in the examples.
In another embodiment of the method according to the invention, it is used to cool air, in which method air is withdrawn from the environment and is fed through the passages, and the trough contains evaporation water which is absorbed by the liquid-absorbent material and at least part of which is evaporated during the rotation of the drum, with the result that the temperature of the remaining evaporation water and/or of the liquid-absorbent material is reduced, with the result that the temperature of the air which comes into contact therewith is reduced.
Particularly in houses and buildings, it is important, particularly when the outside temperature is high, for the temperature of the air inside the buildings to be reduced to an acceptable level while, at the same time, providing sufficient ventilation. If the air is simply cooled and dehumidified, the inside climate becomes unpleasant, leading to what is known as sick building syndrome. This is because of the fact that, for economic reasons, the cooled air is reused, with the result that insufficient fresh air is supplied. The cooling efficiency of a good air conditioning installation—the COP—is 5. This means for each kW of electric power supply 5 kW of cooling energy is obtained.
Using the invention, outside air is cooled by the evaporation of water. The COP is in this case
75
. The cooling energy is obtained by the evaporation of water. Since in this method the economic reason is virtually eliminated, it is possible to cool sufficient fresh air and to ensure that the inside climate remains cool and pleasant.
As will be explained in more detail below, by using the method according to the invention in which water is evaporated and therefore heat is extracted, it is possible to achieve very substantial cooling of air which is to be fed to a working environment while, at the same time, the humidity levels in the cooled air remain at an acceptable level. In the conventional air conditioning units of the type which have a closed evaporation/cooling system, it is often the case that not only is the air cooled, but also there is a considerable reduction in humidity, with the result that the condition of the air is uncomfortable for people working in this environment.
In another embodiment of the method according to the invention, it is used for desalination of water, in which method air is withdrawn from the environment and is fed through the passages, and the trough contains salt-containing water which is absorbed by the water-absorbent material and at least some of which is evaporate
Hoffmann & Baron , LLP
Jiang Chen-Wen
The Waterpower Trust N.V.
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