An improved method and apparatus for purging moisture from a refrigeration system includes means for withdrawing a mixture of refrigerant vapor and moisture from the system, removing moisture from this mixed stream and then reintroducing the dried vapor into said evaporator, all of said operation taking place during a normal shutdown period of said system.
Dillenbeck, Warren H. (York, PA)
Muench, Paul W. (Medford Lakes, NJ)
Walker, Elmo R. (York, PA)
What is claimed is
1. In a refrigeration system of the closed circuit, vapor cycle type, the improvement comprising refrigerant drier means; and means for circulating a stream of refrigerant vapor and moisture through said drier means from the vapor space of said system during periods when the system is not in operation.
2. Apparatus as defined in claim 1 wherein said means for circulating said stream includes conduit means connecting said system and said refrigerant drier means in a closed circuit fluid path, and a heater element adapted to induce circulation of vapor through said conduit means and said drier.
3. Apparatus as defined in claim 1 wherein said means for circulating said stream includes a blower in said conduit means.
4. A method of removing moisture from a refrigeration system of the type utilizing a flooded evaporator including an evaporator shell, a tube bundle in said shell, and a body of refrigerant therein, the refrigerant level being below the upper portion of said shell; the steps which include withdrawing a stream of refrigerant vapor and moisture only during periods when said system is not in operation, removing moisture from said vapor and moisture stream and returning the dried refrigerant vapor to the evaporator shell.
5. A method of removing moisture from a refrigeration system of the type utilizing a shell and tube condenser, the steps which include withdrawing a stream of refrigerant vapor and moisture from said condenser only during periods when said system is not in operation, removing moisture from said vapor and moisture stream and returning the dried refrigerant vapor to said condenser.
BACKGROUND OF THE INVENTION
1. Field of the Invention
Purging apparatus and methods for removing moisture from refrigeration systems, particularly flooded evaporators.
2. Description of Prior Art
U.S. Pat. No. 2,951,349 issued to T. L. Etherington discloses means for taking a portion of the refrigerant being introduced into the suction side of a compressor and removing moisture by a chemical absorber.
SUMMARY OF THE INVENTION
This invention relates to apparatus and a method for removing undesirable moisture from a refrigeration system, particularly the closed circuit, vapor cycle type in which a flooded evaporator or shell and tube condenser are employed.
In refrigeration systems using a halocarbon refrigerant, it is extremely important to keep moisture out of the refrigerant circulatory system, because moisture causes the refrigerant to break down and increases the corrosion of metal parts in contact with the refrigerant, particularly the tube bundles and compressor working spaces. The problem is most acute when using refrigerants which evaporate at subatmospheric pressures, because even the smallest leak in the system allows entry of humid air. Centrifugal water chilling machines, which generally use R-11 refrigerant, are typical of subatmospheric systems.
Most refrigerant driers operate continuously while the compressor is running, such as by continuously passing refrigerant vapor (and entrained moisture) through a chemical drier to adsorb moisture or, as in the case of Etherington, periodically withdrawing the stream and subsequently regenerating the desiccant.
It has been found that these approaches are not as effective as they might be; because liquid and vapor samples taken from the system, during machine operation, are almost always dry. It is possible that the water in the system migrates to the liquid surface in the evaporator where it is difficult to remove. However, when the machine is shut down, the water evaporates and a high concentration of moisture is found in the refrigerant vapors throughout the system.
It is an object of the present invention to provide means for withdrawing moist refrigerant vapor in a stream from the vapor space of the system, drying it and then reintroducing the dried refrigerant into the vapor space, all during a period of shutdown.
DETAILED DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic drawing disclosing a typical water chiller and including the improved means for drying refrigerant which is withdrawn from the vapor space of the evaporator; and
FIG. 2 is a view similar to FIG. 1 showing a modification of the invention.
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a typical vapor cycle refrigeration system including a centrifugal compressor 10, a condenser 12, an expansion device 14 and an evaporator 16. In operation, the refrigerant vapor is compressed by the compressor and conducted to condenser 12 by means of a conduit 20. The liquid refrigerant flows to the expansion device by means of passages 22 and the low pressure refrigerant passes into the evaporator shell through passage 24. The vapor is delivered to the suction side of the compressor through conduit 26.
It will be noted that the evaporator described herein is of the flooded type in which the tube bundle 30 in shell 31 is at least partly submerged in a body of liquid refrigerant, the level of which normally varies (depending on the load) around the line indicated at 32.
The improvement of the present invention comprises means connected to the upper portion of the evaporator shell for withdrawing a stream of refrigerant vapor containing moisture and for drying the same. In one form of the invention shown in FIG. 1, a heater element 38 is operatively associated with a conduit 39 which has its entrance end located at 40 and its exit end located at 42. A drier element 44, which may be either of the disposable or regenerative type, is located in conduit 39 to adsorb water as the stream passes through it. The heater element is energized only during shutdown of the system when the moisture tends to migrate into the upper space above the tube bundle. The heat energy applied to the conduit by the heater causes a convective movement of vapor from the entrance 40 to the exit 42 through the drier element.
In the modified system shown in FIG. 2, the same reference numerals are applied to identical elements. In this case, a mechanical vapor flow inducing element, such as blower 50, is substituted for the heater. Again, the blower is energized, causing the refrigerant vapor and moisture to circulate through the line, only when the system is shut down.
While the invention has been described in connection with a certain specific embodiment thereof, it is to be understood that this is by way of illustration and not by way of limitation. For example, the drier could as well be applied to the condenser vapor space. The scope of the appended claims should be construed as broadly as the prior art will permit.