Refrigeration – Processes – Circulating external gas
Patent
1990-05-16
1991-06-18
Makay, Albert J.
Refrigeration
Processes
Circulating external gas
62 94, 62272, F25D 1706
Patent
active
050240625
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a process for gas conditioning, especially air conditioning, according to a novel principle comprising isothermal step-by-step dehumidification of the gas by means of a suitable liquid, over which the vapour pressure of the substance absorbed is low, and multi-stage evaporation of said liquid before re-use.
In certain areas of the earth the climate is characterized by a high air temperature throughout the year or during parts thereof. This high air temperature is often combined with a high relative humidity. When the temperature approaches the human body temperature the conditions are oppressive and strenuous. Various methods for lowering the temperature by more or less sophisticated technics have been practiced during the years.
In industrialized countries various methods for cooling, dehumidification, reheating and remoistening have been practiced for a long time. A good energy supply is required for all these measures. All kinds of energy are not equivalent in that connection. The most frequent air conditioning technics comprises cooling by means of mechanical vapour compression of a cooling medium, in most cases under electricity consumption.
In an attempt to replace the electricity by thermal energy the absorption technics for dehumidification and cooling has been utilized. However, the efficiency of said processes has not been as good as that obtained with mechanical compression. On the other hand the costs of electric energy is considerably higher than the costs of thermal energy.
The traditional absorption heat pump known for a long time operates with one absorption stage and one stage for regenerating the absorption liquid. When the energy used in the latter stage can be utilized the energy recovered would theoretically be twice the energy supplied. In reality the heat factors are 1.1-1.5.
One of the obstacles for improving the heat factor of the traditional absorption heat pump is the great boiling point elevations always occurring in absorption liquids consisting of aqueous solutions of very soluble salts. The inclination to absorb water from a gas is combined with a corresponding disinclination to release this water by boiling.
In order to cool air having a high temperature and a high humidity the air may be contacted with a suitable moisture absorbing liquid under simultaneous cooling which results in a removal of the heat of evaporation of the water condensed, which heat is released during the absorption. It is desirable that the absorption be carried out by means of a salt solution as concentrated as possible in order to obtain a treated air having a relative humidity as low as possible. Since the untreated air in most cases has a high temperature and a high relative humidity and the available cooling water temperature often is close to the air temperature, the absorption may be said to take place as good as isothermally. It is necessary to avoid a greater dilution of the absorption liquid since the low relative humidity will then be jeopardized. In practice this means a boiling point elevation of 70.degree.-80.degree. C. during the regeneration of the liquid which makes it difficult or impossible to save energy by means of e.g. multi-stage evaporation, compressor evaporation, etc.
According to the invention these difficulties are eliminated by carrying out the absorption of the moisture of the air or gas in several successive absorption stages, the water absorption from the air having the highest humidity being carried out with an absorption liquid having a low concentration and the concentration of the absorption liquid being increased successively from stage to stage. Consequently, the consumption of thermal energy when regenerating the absorption liquid may be decreased by the isothermal multi-stage absorption in the air conditioning process according to the invention.
Thus, the present invention relates to a process for conditioning moist gas, which process is characterized in that the gas step-by-step is contacted with a successively more concentrated a
REFERENCES:
patent: 2017027 (1935-10-01), Forrest
patent: 2182453 (1939-12-01), Sellew
patent: 2894376 (1959-07-01), Kelley
Glazier Stephen
Makay Albert J.
Sears Mary Helen
Sollecito John
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