Refrigeration – Automatic control – Of closed system sorbent type
Reexamination Certificate
2000-05-26
2001-07-17
Doerrler, William (Department: 3744)
Refrigeration
Automatic control
Of closed system sorbent type
C062S476000, C062S103000
Reexamination Certificate
active
06260364
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to absorption cooling systems and to absorption heating and cooling systems. In particular, the invention relates to a dilution control apparatus for releasing, into such systems, within the available dilution time, a quantity of additional refrigerant sufficient to enable them to shut down without creating conditions that allow crystals of the absorbent to form in their absorbers.
In an absorption type cooling system, an absorbent is dissolved in a liquid refrigerant to produce a refrigerant-absorbent solution that is suitable for use in the process. When such a system operates under cooling loads that vary, the amount of refrigerant necessary to keep the system running efficiently will also vary. As a result, it is a common practice to equip such a cooling system with a refrigerant adjusting system which includes a refrigerant storage reservoir, and to store refrigerant in or release refrigerant from this reservoir as necessary to keep the concentration of the solution within an acceptable range of concentrations as the cooling load fluctuates. This storage reservoir often takes the form of a sump that is located in or in close association with the system condenser.
One example of a cooling mode refrigerant adjusting system of the above-described type is described in unexamined Japanese application 62-178858, which is assigned to Ebara Ltd. of Tokyo, Japan. In the latter application, there is disclosed an absorption machine in which the gravity flow of liquid refrigerant between the system condenser and the system evaporator is controlled in response to a sensed condition of the system, such as the solution temperature as it is leaving the absorber. A reservoir for liquid refrigerant is provided inside the condenser and the refrigerant is supplied to the evaporator through a first flow path under normal operating conditions. Upon the sensing of a condition that calls for an increase in the quantity of refrigerant, a second flow path is opened which supplies additional refrigerant from the condenser to the evaporator.
Another example of a refrigerant adjusting system is described in copending U.S. patent application Ser. No. 09/244,910, filed Feb. 4, 1999, which is commonly assigned herewith, and which is hereby expressly incorporated by reference herein. In the latter application, there is disclosed an absorption type machine in which refrigerant is stored in a holding tank that is separate from the condenser sump and that is filled via a refrigerant bleed line. The desired refrigerant concentration is then maintained by releasing refrigerant from the holding tank under the control of a microprocessor in response to the sensing of a need for additional refrigerant.
An example of a refrigerant adjusting system that is specially adapted for use in an absorption type refrigerator is described in U.S. Pat. No. 5,806,325 (Furukawa et al). In the latter patent there is described an absorption type refrigerator in which a storage reservoir is formed in the condenser by a dam with an array of holes that allows the rate at which refrigerant is released to vary as a function of the rate at which refrigerant condenses and, consequently, as a function of the cooling load that the refrigerator must support.
When an absorption type cooling system is shut down, it is necessary to release into the system, within a time known as the dilution time, a quantity of refrigerant which is sufficient to dilute or reduce the concentration of the absorbent-refrigerant solution within the absorber to a value low enough to prevent crystals of the absorbent from forming therein. The diluting of this solution during the shut down process is known as the dilution cycle of the system. Prior to the present invention, the additional refrigerant necessary to enable the system to complete its dilution cycle was provided in one of two ways. A first of these was to pump the additional refrigerant from a specially provided storage tank. This approach is not cost effective, however, not only because of the cost of providing such a storage tank, but also because of the cost of providing the associated pump and pump control circuitry.
A second way of providing the additional refrigerant necessary to complete the dilution process was to release into the system the contents of the refrigerant storage reservoir or tank that is used as a part of its cooling mode refrigerant adjusting system. This way of diluting the solution, however, has a deficiency that limits its usefulness. This is that the reservoir outlets and piping through which refrigerant is released during the cooling mode refrigerant adjusting process are too small to allow the refrigerant necessary to complete the dilution process to be released within the available dilution time. As a result, the released refrigerant may not be able to mix with the absorbent-refrigerant solution rapidly enough to prevent crystals from forming in the absorber.
While the above-mentioned deficiency may be overcome by providing circuitry which senses the occurrence of a shut down condition, and which opens valves that controllably increase the rate at which refrigerant is released into the evaporator, the provision of such circuitry and valves substantially increases the cost of the shut down portion of the cooling system. The provision of such control circuitry and valves also increases the complexity of the system and thereby introduces failure modes that decrease the overall reliability thereof.
In view of the foregoing, it will be seen that, prior to the present invention, there existed a need for a simple but effective way of releasing into an absorption cooling system, within the available dilution time, a quantity of refrigerant sufficient to prevent crystals from forming in the absorber after the system has been shut down.
SUMMARY OF THE INVENTION
In accordance with the present invention there is provided an improved dilution control apparatus that provides a simple but effective way of releasing into the system, within the available dilution time, a quantity of refrigerant sufficient to prevent crystals from forming in the absorber sump after the system has been shut down.
Generally speaking, the present invention includes, in association with the condenser, a primary refrigerant reservoir having a storage capacity sufficient to store a quantity of refrigerant which, if released into the system during the dilution phase of the shutdown process, is sufficient to lower the concentration of the solution from a concentration which is within the range of concentrations that the solution may have when the system operates normally in its cooling mode to a concentration which is low enough to prevent crystals of the absorbent from forming in the absorber after the system has been shut down. When the system operates in its cooling mode, refrigerant is released from this reservoir, via a primary refrigerant releasing structure which includes a primary refrigerant barrier, such as a dam, that is located at one extremity of the primary reservoir and that defines at least one (preferably two) flow paths along which refrigerant may be released from the primary reservoir into the evaporator sump. These flow paths assure that the system is provided with refrigerant at a rate which is sufficient to assure that the system operates efficiently in spite of fluctuations in the cooling load carried by it. In preferred embodiments of the invention, refrigerant flowing along these flow paths are mixed together in an outlet box and supplied to the evaporator through a single primary drain pipe.
The present invention also includes a secondary refrigerant reservoir and a secondary refrigerant releasing structure which does not release refrigerant into the evaporator sump when the system is operating in its cooling mode, but which does release refrigerant into the evaporator sump when the condition of the system indicates that it is being shut down, i.e., when the dilution cycle is in progress. As a result, the secondary reservoir and secondary
Gupte Neelkanth Shridhar
Moon In Shik
Ryu Jin Sang
Carrier Corporation
Doerrler William
Jiang Chen-Wen
Wall Marjama & Bilinski
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