Refrigeration – Automatic control – Refrigeration producer
Reexamination Certificate
2000-10-19
2001-11-06
Tanner, Harry B. (Department: 3744)
Refrigeration
Automatic control
Refrigeration producer
C062S222000, C062S278000, C062S509000, C062S513000, C062SDIG001
Reexamination Certificate
active
06311507
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
This invention relates to refrigeration systems in general, and more specifically, a refrigeration system capable of maintaining a minimum pre-set condensing pressure to produce hot gas for defrosting or heating air units or for use in reheating coils to control relative humidity inside an enclosure, when the ambient conditions around the condenser are very cold.
BACKGROUND OF THE INVENTION
In any conventional refrigeration system, the evaporator or air unit is subject to frosting over when the evaporator temperature is below freezing point. One method of preventing the evaporator from clogging up with frost is to apply an external heat source, such as an electrical heater or water, to the exterior of the air unit which warms it up enough to melt the frost. Another method is to release hot, gaseous refrigerant stored in the receiver of the refrigeration system to the interior of the air unit pipes. Using hot refrigerant from the refrigeration system is preferable to an external heat source, because the hot gas is a by-product of a refrigeration system and an additional energy source is not required.
There are also times when it is desired to warm the enclosure such as when outdoor ambient temperatures are very low. An external heat source, such as an electric heater can be used, but again it is desirable to heat the enclosure using the hot, gaseous refrigerant from the receiver as above. This hot, gaseous refrigerant is routed through hot gas piping either to the air unit in a heating mode or to a separate re-heating coil for heating the enclosure or to control its relative humidity.
However, as the temperature of ambient conditions surrounding a condenser of a refrigeration system sized for the summer conditions begins to drop, the condenser is too large and becomes able to condense the refrigerant at much lower pressures. The pressure of the refrigerant leaving the compressor decreases, and the receiver fills substantially with liquid refrigerant at a lower pressure. In this situation, there is less hot gas refrigerant available, and because the condenser pressure is lower, the available hot gaseous refrigerant is also at a lower pressure and temperature. Many times there is not enough pressure and the gaseous refrigerant is not hot enough to provide ample defrosting to the air unit, to provide heating to the enclosure, or to operate the re-heat coil.
Therefore, there is a need for a refrigeration system that can produce enough hot, gaseous refrigerant at a controlled pressure to defrost air units, operate air units in a heating mode, or operate the re-heat coils, when ambient conditions around the condenser are low.
SUMMARY OF THE INVENTION
The present invention is an improved refrigeration system capable of producing hot gaseous refrigerant at pressures enough to defrost the air unit when the temperature of the ambient conditions around the condenser is low. The system has a compressor for compressing a refrigerant to a hot gaseous refrigerant. The compressor has oil for lubrication. A condenser receives the hot gaseous refrigerant from the compressor and condenses at least a portion of the refrigerant to a liquid refrigerant. A thermo-siphon vessel receives and stores the liquid refrigerant from the condenser. An oil cooler receives the liquid refrigerant from the thermo-siphon vessel and uses the liquid refrigerant to cool the compressor oil. An air unit receives liquid refrigerant from the receiver and uses the liquid refrigerant to cool the enclosure. A receiver receives and stores the liquid refrigerant from the thermo-siphon vessel and releases the liquid refrigerant to the air unit. A pressure regulator between the receiver and the thermo-siphon vessel controls the minimum pressure of the liquid refrigerant from the thermo-siphon vessel. A hot gas line leads from a portion of the system containing hot gaseous refrigerant to the evaporator to defrost the evaporator.
The condenser has an inlet and the upper portion of the receiver is in communication with the inlet for equalizing the pressure of the receiver with the inlet of the condenser. The receiver receives the refrigerant from the oil cooler after cooling the compressor oil. The hot gas line leads from an upper portion of the receiver. The liquid refrigerant is routed to the air unit from the receiver by a liquid line. The liquid line has an inlet positioned above the bottom of the thermo-siphon vessel so as not to completely drain the thermo-siphon vessel when the system runs out of liquid. The pressure regulator opens and closes in response to upstream pressure in this liquid line. If this upstream pressure is below the pressure regulator set point, the liquid flow from the thermo-syphon receiver will stop. That will allow the liquid to flood the condenser. The condenser loses area and increases the discharge pressure of the compressor since the temperature of condensation increases due to the loss of area resulting from flooding. This system allows the pressure at the thermo-syphon receiver to raise and consequently the pressure of the high pressure receiver. The hot gas line coming from the high pressure receiver feeds the air units to raise the temperature of the enclosure and to allow defrost inside as required.
REFERENCES:
patent: 4566288 (1986-01-01), O'Neal
patent: 4862702 (1989-09-01), O'Neal
patent: 5454228 (1995-10-01), Yang et al.
Industrial Refrigeration Handbook by Wilbert F. Stoecker, 9 pages.
Refrigeration 1998 Ashrae Handbook from American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc., 5 pages.
Thermosyphon Oil Cooling from Frick E 70-900E/Aug. 95, pp. 1-10.
Bracewell & Patterson L.L.P.
Carter Burgess, Incorporated
Tanner Harry B.
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