Refrigeration – Refrigeration producer – Sorbent type
Reexamination Certificate
2001-03-13
2002-06-04
Doerrler, William (Department: 3744)
Refrigeration
Refrigeration producer
Sorbent type
C062S483000, C062S487000, C062S101000, C062S147000, C417S208000
Reexamination Certificate
active
06397625
ABSTRACT:
The invention relates to an absorption refrigeration machine according to the Platen-Munters system, with a generator for evaporating a refrigerant in a solvent, a solvent separator in which the separation of the solvent from the refrigerant is performed, a condenser for liquefying the refrigerant, an evaporator in which the refrigerant is evaporated using a dry gas while being cooled, optionally with a first gas heat exchanger, and an absorber in which the evaporated refrigerant is added to the depleted mixture of refrigerant and solvent which is then again evaporated in the generator.
To operate a known absorption refrigeration machine according to the Platen-Munters system it is necessary to have a heat source with a temperature far in excess of 100 degrees Celsius. At temperatures of 100 degrees Celsius and below the efficiency tends towards zero. Existing heat sources with low temperatures such as hot water from industrial waste heat system such as long-distance heating, solar heating or the like are not suitable for the conventional designs of said absorption refrigeration machines because the required high temperatures can generally not be achieved.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an absorption refrigeration machine of the kind mentioned above with which it is possible to achieve a high efficiency even at relatively low temperatures, preferably at approx. 75 degrees Celsius.
This is achieved in accordance with the invention in such a way that the output of the evaporator or the output of the optional first gas heat exchanger which is arranged downstream of the evaporator and the output of the generator open into a bypass leading into the absorber, with the mixture consisting of evaporated refrigerant and dry gas which arrives from the evaporator via the first gas heat exchanger being transferred to the output of the generator and from there into the bypass where the gas mixture is brought into contact with the hot, partially degassed solution coming from the generator and withdraws further refrigerant from the same.
The mixture arriving from the evaporator via the first gas heat exchanger is therefore not transferred directly to the absorber, but instead to the output of the generator and from there through the bypass and withdraws refrigerant from the solution arriving from the generator. It is also possible to omit the first gas heat exchanger, so that in this case the mixture is guided from the output of the evaporator to the bypass input. It is possible in both cases to achieve a low solution concentration in the area of the absorber input which is a precondition for a low refrigerating temperature without requiring that the generator be strongly heated. Heat sources of low temperature can therefore be used for the absorption refrigeration machine in accordance with the invention. As a result of the low generator temperature, the quantity of the simultaneously evaporated water is reduced, thus avoiding any losses in efficiency in the evaporator.
In a further development of the invention it may be provided that a second gas heat exchanger is provided whose primary side is disposed between the output of the evaporator or, optionally, the output of the first gas heat exchanger and the input of the bypass and whose secondary side is disposed between the output of the bypass and the input of the absorber, so that the gas mixture arriving from the bypass is cooled. The cooling of the gas mixture allows improving the enrichment of the depleted mixture arriving from the generator.
The bypass allows a low operating temperature, but also causes energy loss. According to a further embodiment of the invention it can be provided that a control valve is arranged between the output of the evaporator and the input of the absorber or between the input and the output of the bypass with which the quantity of the gas can be metered which is rerouted through the bypass, with the part not rerouted flowing directly to the absorber. This ensures a regulation of the bypass effect on the momentarily required temperature reduction of the supplying heat source.
According to a variant of the invention, the control valve can be a straight-through valve which short-circuits the bypass, as a result of which the bypass becomes ineffective when the valve is opened and the bypass can be fully effective when the valve is closed.
According to a further variant of the invention the control valve can be a three-way valve which divides the gas mixture arriving from the evaporator between the flow to the bypass and the flow to the absorber. As a result, the bypass can be set very precisely in its effect.
In order to increase the contact surface between the gas mixture flowing through the bypass and the liquid flowing through the same, the interior wall of the bypass tube can be coated with an ammonia-resistant fiber material, with the ammonia-resistant fiber material preferably being formed by a glass-fiber web which fulfills the requirements placed on a large surface and high durability.
A further feature of the invention can be that in the interior of the bypass tube there is arranged a coil spring resting on the interior wall thereof, with the ammonia-resistant fiber material being tensioned between the interior wall and the coil spring.
It is prevented in this way that the bypass flow cross section decreases for the gas flowing through the bypass.
A particularly high efficiency is achieved in accordance with a further embodiment of the invention in such a way that the refrigerant is formed by ammonia and the solvent by water.
It can further be provided that the bypass is heatable, thus making the bypass temperature adjustable to a value in which the inflowing gas mixture withdraws a very high share of ammonia from the depleted solution.
The invention relates further to a bubble pump for an absorption refrigeration machine with at least one vertical pump tube which is heatable by a liquid or gaseous heat carrier medium and in which a refrigerant solution can be moved upwardly by bubble formation.
The liquid circulation in absorption refrigeration machines is often maintained by so-called “mammoth” or “bubble pumps”, e.g. in the classical system of Platen-Munters in which water is used as solvent and ammonia as refrigerant. As the energy of a heat source can be taken for the operation of such an absorption refrigeration machine, it is outstandingly suitable for the conversion of solar power into cold. Conventional bubble pumps are not or only badly suited for the heating by heat carrier media with variable temperature as occurs in the winning of solar power.
Such a bubble pump consists of two mutually communicating vessels which are filled with a hydrous ammonia solution. One of these vessels, namely the active part of the pump, is arranged as a small upwardly striving tube which is heated, so that ammonia is released in its interior. The produced gas bubbles drive the solution upward in the narrow tube. In some bubble pumps one can find a small gas collecting vessel in the lower part of the upwardly striving tube in which the tube penetrates from above. The gas collects there before it upwardly pushes the liquid in the tube situated above.
In the two aforementioned types of bubble pumps there is a critical low temperature range in which the gas bubbles will form so slowly that they are too small to fill the entire cross section of the pump tube and will therefore migrate upwardly without entraining any liquid. The ammonia concentration will thus decrease in the pump tube. According to the thermodynamic data of ammonia solution in water, the temperature at which ammonia can be released will then rise. In the case of a slow rise in the temperature of the pump the required minimum temperature will thus rise simultaneously and situations can occur in which the bubble pump will consistently fail to operate because the pump tube only contains water and hardly any more ammonia. The aforementioned gas collecting vessel is provided to reduce this danger. Pa
Doerrler William
Feiereisen Henry M.
Jones Melvin
Solarfrost International Ltd.
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