US2730869A - Purging device for closed refrigeration systems - Google Patents

Description

Jan. 17, 1956 E. M. STUBBLEFIELD PURGING DEVICE FOR CLOSED REFRIGERATION SYSTEMS Filed Jan. 8, 1952 INVENTOR.

of liquid willstand in conduit 26 between the levels X and Y and a liquid column will stand in the conduit 25" between the levels Z and the top of the conduit which balance the difference in pressure between the high and low pressure sides of the system.

The absorber 8 and condenser 6 are cooled by cooling water from any suitable source which flows through the elements successively. The cooling water is delivered to a plurality of cooling coils 31 in the absorber 8 from a conduit 32 and header 33 connecting one end of the coils. The outlet ends of the cooling coils 31 are connected together by a header 34 and the cooling water from the absorber flows through conduit 35 to the inlet chamber 36 of the condenser 6. Cooling water then flows through the tubes 37 of the condenser 6 and is discharged from the system through a conduit 38.

The various elements of the refrigeration system are connected to each other to provide a closed hermetically sealed system which is initially evacuated to a very low pressure of at least 2 mm. Hg abs. or less. After the system has been evacuated a water solution of a salt such as lithium bromide is introduced into the system, the water of the solution constituting the refrigerant and the salt solution at different concentrations constituting the absorption solution weak in refrigerant and absorption solution strong in refrigerant. During operation of the system the generator and condenser 6 may have a pressure of 40 mm. Hg abs. corresponding to a condensing temperature of 90 F. and the evaporator 7 and absorber 8 may have apressure of 8 mm. Hg abs. corresponding to the vapor pressure of the lithium bromide solution at its particular temperature. The refrigerant, water, will then boil at 46 F. in evaporator 7 at the low pressure therein. In such a vacuum type system non-condensable gases are apt to occur which blanket the heat transfer surfaces of'the condenser tubes 37 and cooling coils 31 of the absorber 7. These non-condensable gases probably result from corrosion in the unit and a large percent of the gases is hydrogen. While the corrosive effect on the elements. of the unit may be negligible, the volume of hydrogen gas produced by such corrosion is excessive due to the low pressure and will interfere with the proper operation of the system.

To prevent the accumulation of such non-condensable gases in any element of the active part of the system means are provided for continuously transferring such gases from other parts of the system to one element thereof where they are collected and stored as described in detail in the Roswell reissue patent, referred to above. Suffice it to state herein that gases occurring in the generator 5 and condenser 6 are swept by the refrigerant vapor toward the outlet end of the condenser and pass through the orifice 19 concurrently with the liquid refrigerant into the evaporator 7. Non-condensable gases in the evaporator 7 and absorber 8 are swept by refrigerant vapor tothe bottom and center of the absorber where turbulence is'at a minimum. A purging device 39 is provided for withdrawing the gases 'from the absorber which is in the form of an auxiliary absorber having a chamber 40 connected to the main absorber by a suction tube 41 extendingto the bottom and center of the latter where the non-condensable gases accumulate. A limited quantity of absorption solution weak in refrigerant flows from conduit 25 to the purge chamber 40 through a vessel'47 is located above the highest level to which liquid can rise in riser 46 at the pressures in the system. The

gas storage vessel 47 also has a nipple 48 with a valve 49 for detachable connection to a vacuum pump 50 for evacuating the vessel of gases.

for varying the concentration of the absorption solution? in accordance with operating conditions. The side of the concentration control vessel 51 is connected to the end of the lowermost evaporator tube 20 by a conduit 52, the bottom of'the vessel is connected to the inlet chamber 11 of generator 5 by a conduit 53 and the top the chamber 56 and is sealed thereto at opposite ends by of the vessel is connected to the header 22 by a vent conduit 54. Liquid refrigerant overflowing from the evaporator 7 is stored in the concentration control vessel 51 to increase the concentration of the absorption solution to correct the condition causing the refrigerant to overflow and the amount of refrigerant that can be stored varies with the height of the pressure balancing liquid column in the vessel. 1

In accordance with the present invention one of the elements of the refrigeration system has a wall of amaterial which is permeable to hydrogen and non-permeableto other fluids. Palladium is such a material through which hydrogen will diffuse from a source at a higher partial pressure to an atmosphere at lower partial pre ssure regardless of the total pressure at either side of the wall. 1 For example, hydrogen will flow from a vacuum type refrigeration system of the type described from an extremely low absolute pressure of i 8 mm. Hg abs. through a palladium wall to the surrounding atmosphere at 760 mm. Hg abs. so long as the partial pressure of hydrogen in the system is greater than the partial pres sure of hydrogen'in the ambient atmosphere. Such a palladium wall may be applied to any of the elements of the system where the gases are apt to accumulate such as the condenser or absorber but in the illustrated embodiment it is preferably applied to the gas storage vessel to which the gases have been transferred from other parts of the system and are stored at a high concentration and partial pressure. The rate at which hydrogen gas will diffuse through a palladium wall is functionally related to its temperature and will diffuse through the material at atmospheric temperatures at a very slow rate. It is therefore desirable to heat the palladium wall to correlate the rate at which hydrogen will diffuse from the system to the atmosphere with the rate at which hydrogen is generated in the system.

In the illustrated embodiment of the invention the palladium wall is contained in a separate cell 55 connected to the gas storage vessel 47. As shown more clearly in the enlarged view of Fig. 2, the cell 55 is in-the form of an upright chamber 56 connected to the gas storage vessel. 47 adjacent its bottom by a' conduit 57 and adjacent its a top by a conduit 58. The palladium wall comprises a tube 59 of the material which extends vertically through means of silver solder 60 or the like. At one side of the chamber 56 and in intimate heat conducting relation with its wall is a well 61 containing an electric heating element 62. The electric heating element 62 is preferably connected to an electric control system for the refrigeration system, not shown, so that when the refrigeration system is in. operation the heating element is energized but when the system is notin operation the heating element is de-energized. The higher the temperature of cell.55

. the higher the rate of diffusion through the wall of the.

palladium tube 59 and the lower the temperature the lower the rate of diifusion and preferably the heating element is of such capacity relative to the cell 56 as to heat the palladium tube to a-temperature between 300 to' 500 F. Such heating of the cell 56 will cause. a circulation of .non-condensable' gases from the gasstoragevessel'47 through the conduit 57 upwardly through the. chamber 56 of cell 55and back through the conduit 58 to the gas storage vessel. Simultaneously, the heating of the cell 55 causes a flow of atmospheric air through the center of the palladium tube 59. Thus, the non-condensable gases are circulated through the cell 55 to maintain hydrogen at a higher concentration and partialpressure on one side of the tube wall and atmospheric air is circulated through the center of the tube to maintain air on the other side of the tube wall at a low hydrogen concentration and partial pressure so that hydrogen will diffuse through the wall 54 of the palladium tube 59 from the system to the atmosphere. One form of the invention having now been described in detail, the mode of operation of the complete system is described as follows.

Heat from steam supplied to the heating chamber 14 of generator is transmitted through the Walls of the generator tubes to expel refrigerant vapor from absorption solution therein and lift the absorbent into the separating chamber 12. Refrigerant vapor flows at high velocity from the separating chamber 12 to the condenser 6 where the vapor is condensed to a liquid and the flow of refrigerant vapor carries any non-condensable gases to the outlet from the condenser. Liquefied refrigerant and non-condensable gases flow concurrently through the orifice 19 which is of such size as to permit such concurrent fiow but maintain the difference in pressure between the condenser 6 and evaporator 7. Liquid refrigerant evaporates in the tubes 20 of the evaporator 7 at a low pressure and temperature to cool air flowing over the exterior of the finned tubes. t

Simultaneously, absorption solution weak in refrigerant flows by gravity from the separating chamber 12 to the absorber 8 in a path of flow comprising conduit 23, outer passages 24 of the liquid heat exchanger 9 and conduit 25.. Solution supplied to absorber 8 flows by gravity over the cooling coils 31 in the absorber 8 Where it absorbs refrigerant vapor from the evaporator 7 to produce a low pressure and temperature in the latter. The flow of refrigerant vapor from the tubes 20 and through the headers 21 and 22 sweeps non-condensable gases toward the center and bottom of the absorber 8 where turbulence is at a minimum. Absorption solution strong in refrigerant flows by gravity from the bottom of the absorber 8 to the inlet chamber 11 of the generator 5 in a path of flow comprising the conduit 26, inner passages 27 of liquid. heat exchanger 9, conduit 28, leveling chamber 29 and conduit 30. Any unevaporated liquid refrigerant flows from the lowermost tube of the evaporator 7 to the concentration control vessel 51 to vary the concentration of the absorption solution in accordance with operating conditions.

A portion of the absorption solution weak in refrigerant flowing toward the absorber 8 is diverted through the branch conduit 42 into the chamber 40 of the purge device 39 where it flows over the cooling coil 43. Such cooled absorption solution weak in refrigerant absorbs refrigerant vapor to produce a partial vacuum relative to main absorber 8 to draw in non-condensable gases through the suction tube 41. Such non-condensable gases are transferred by the fall tube pump 44 and riser 46 from the active part of the system to the gas storage vessel 47 in an inactive part of the system. The non-condensable gases are thus collected and segregated in the gas storage vessel 47.

Simultaneously with the operation of the refrigeration system the heating element 62 is energized to heat the purging cell 55. Such heating of the cell causes a circulation of gases in the gas storage vessel 47 through the cell 55 and a flow of atmospheric air through the center of the palladium tube 59. Any hydrogen gas in the cell 55 at a higher partial pressure than the partial pressure of hydrogen in the atmosphere will diffuse through the wall of the palladium tube from the closed refrigeration system to the atmosphere. ladium tube 59 and the rate of heating are correlated with the expected rate of hydrogen generation in the system, the gas storage vessel 47 is continuously and automatically purged of hydrogen as fast as it is generated.

it has been found that contact of certain substances such as lithium bromide used as an absorbent will contaminate or poison the palladium so as to prevent the diffusion of hydrogen therethrough. This poisoning effect of lithium bromide or other refrigerants or absorbents can be easily corrected by washing the substances from the surface of the palladium Wall. However, it is ditlicult to so locate the palladium cell 55 as to prevent contamination by refrigerants or absorbents during transportation or to wash the surface of the palladium wall after it has been contaminated. In Fig. 3 a modified construction is illustrated which automatically closes the cell 35 from the refrigeration system when the latter is not in operation and opens the cell for communication with the system when the refrigeration system is in operation. The arrangement illustrated in Fig. 3 is substantially identical with that illustrated in Fig. 2 except that a bimetallic strip 65 is connected intermediate its ends to the Wall of the cell chamber 56 between the inlet and outlet conduits 57 and 58. A valve element 66 is mounted on each end of the bimetallic strip 65 and the arrangement is such that the valves are pressed into engagement with ports at the ends of conduits 57 and 58 at normal temperatures. However, at a high temperature which will exist when the heating element 62 is energized, the bimetallic strip 65 will automatically flex to open the conduits 57 and 58 to permit the flow of gases from the gas storage vessel 47 through the chamber 56 of the cell 55.

It will now be observed that the present invention provides a device for continuously and automatically purging hydrogen from a closed refrigeration system to the atmosphere. it will further be observed that the present invention provides a palladium wall in one of the elements of the system through which hydrogen diffuses froma relatively high partial pressure in the system to a lower partial pressure in the ambient atmosphere. It will further be observed that the present invention provides a heated cell connected to one of the elements of the system and having a vertically arranged palladium tube extending therethrough. It will still further be observed that the present invention provides an automatic valve means for closing the purging cell from communication with the refrigeration system when the latter is not in operation and opening the cell for communication with the system when the refrigeration system is in operation.

While two embodiments of the invention are herein illustrated and described, it will be understood that further changes may be made in the construction and arrangement of elements without departing from the spirit or scope of the invention. Therefore, without limitation in this respect, the invention is defined by the following claims.

I claim:

1. In a closed vacuum type heat transfer apparatus having a plurality of elements and containing a solution of water in absorbent from which water vapor is expelled by the application of heat and in which hydrogen is apt to accumulate as a foreign body which interferes with the proper operation of the apparatus, a purging device for automatically removing hydrogen from the interior of the closed apparatus comprising a wall in an element of the apparatus where hydrogen accumulates which is permeable to hydrogen and nonpermeable to water vapor, said hydrogen automatically diffusing through said wall from the interior to the exterior of the apparatus, and the exterior surface of said hydrogen permeable wall being so arranged as to facilitate the escape of dif- As the wall surface of the pal 7 fused hydrogen therefrom to maintain a lower partial pressure of hydrogen in the atmosphere at the outside of the wall than the partial pressure of hydrogen in the atmosphere at the inside of said wall.

2. A purging device for a closed heat transfer apparatus in accordance with claim 1 in which the hydrogen permeable wall is composed of palladium and located in I ,a cell connected to an element of the apparatus from which it receives hydrogen, and means for heating the cell.

3. A purging device for a closed heat transfer apparatus in accordance with claim 1 in which means are provided' for continuously transferring hydrogen from other parts of the apparatus to the element having the hydrogen permeable wall.

4. In combination with a closed refrigeration system having a plurality of elements and in which hydrogen is apt to accumulate,.a cell for purging hydrogen from the system comprising, a chamber connected at its top and bottom to one of the elements where the hydrogen accumulates, a palladium tube extending vertically through said chamber and sealed thereto, and means for heating the cell to cause a circulation of hydrogen from the system through the chamber and a circulation of air through the center of the tube.

5. In a vacuum type absorption refrigeration system utilizing water as a refrigerant and a salt solution as an absorbent, a gas storage vessel, means for continually transferring non-condensable gases from the other elements tothe storage vessel, and a cell for automatically purging hydrogen from the system to the atmosphere comprising a chamber connected to the gas storage vessel and a palladium tube extending vertically through the chamber, and means for heating the cell, the hydrogen diffusing through the wall of the palladium tube from a higher partial pressure in the cell to a lower partial pressure in the atmosphere.

6. In a closed refrigeration apparatus in which hydrogen accumulates as a foreign body, a cell connected to the apparatus and having a palladium wall through which hydrogen diffuses from the interior of the apparatus to the atmosphere, valve means for opening the cell for communication with the interior of the apparatus during periods of operation and closing the cell from the interior of the apparatus when the system is not in operation, and means responsive to an operating condition of the refrigerating apparatus for opening the valve means.

7. In a closed refrigeration system in which hydrogen accumulates as a foreign body and interferes with the operation of the system, means for transferring hydrogen from other parts of the system to one of the elements thereof, a cell connected to the element where the hydrogen is transferred, a palladium wall in the cell through which hydrogen diffuses to the atmosphere, valve means for opening and closing the connection between the system and the cell, means for heating the cell, and a movable actuator responsive to the heating means for opening the valve means when the cell is heated.

8. In combination with a closed refrigeration apparatus in which hydrogen is apt to accumulate, means for automatically purging hydrogen from the apparatus comprising a wall in the apparatus which is permeable to hydrogen and non permeable to other fluids, a construction,

providing a flue for directing ambient air over the exterior of the hydrogen permeable wall, and means for heating the flue to cause circulation of ambient air therethrough to sweep hydrogen from the exterior surface of the hydrogen permeable wall whereby to cause hydrogen to diffuse through the wall from a higher partial pressure in the system to a lower partial pressure in the ambient atmosphere. v

9. In a refrigerating apparatus containing a working fluid in which hydrogen is apt to accumulate as a foreign body, means for transferring hydrogen from other parts 7 of the system to one of the elements thereof, a cell connected to the element where the hydrogen is transferred, a wall of the cell being composed of a material permeable to hydrogen and non-permeable to other fluids and through which hydrogen diffuses from the interior of the apparatus to the ambient atmosphere, said hydrogen permeable wall. being subject to contamination by the working fluid in said apparatus, and means for protecting the hydrogen permeable wall from contact by working fluid in any tipped position of the apparatus during transit while permitting flow of hydrogen to the wall during operation of the apparatus.

References Cited in the file of this patent UNITED STATES PATENTS 1,174,631 Snelling Mar. 7, 1916 1,685,759 Walter Sept. 25, 1928 1,738,720 Munters Dec. 10, 1929 1,964,391 Thomas June 26, 1934 2,320,349 Cropper June 1, 1943 2,374,564 Reid Apr. 24, 1945 2,456,163 Watson Dec. 14, 1948 2,536,610 King Jan. 2, 1951 2,627,933 Teter Feb. 10, 1953 FOREIGN PATENTS 308,792 Great Britain Aug. 11, 1930 358.086 Great Britain Sept. 30, 1931

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