US2175419A - Purger arrangement - Google Patents

Description

Oct.A 10, 1939. l.. F. WHITNEY- PURGER ARRANGEMENT Filed oct. 5, 1937 2 Sheets-Sheet 1 I?? 1622 07; [ymara ffl/Zita@ Oct. 10, 1939.P F. WHITNEY PURGER ARRANGEMENT Filed Oct. 5, 1957 2 Sheets-Sheet 2 tra@ A zii/L5:

Wwf/k fw E Zymarz I ZJ Patented ct. l0, 1939 UNITED ,STATES 2,175,419 runden. ARRANGEMENT' Lyman F. Whitney, Cambridge,

by mcsne assignments, to Stator Mass., assignor, Corporation, a

corporation of Rhode Island Application October 5, 1937, Serial No. 167,402

1s claim.. (ci. 627-115) This invention relates to low pressure heat exchange apparatus, and particularly to purger arrangements associated with such apparatus. The United States Patent No. 1,761,551 to East- 5 'man A. Weaver discloses a low pressure refrigerating apparatus wherein a heavy propellant liquid,

such as mercury, is effective in pumping an aqueous refrigerant about a refrigerant circuit.

All portions of such a circuit preferably operate l0 at a sub-atmospheric pressure, the pressure of the cooler, for example, being less than mm. absolute under ordinary operating conditions, and the.

pressure of the condenserr similarly being less than 150mm. absolute. As set forth in the United States Patent No. 1,892,869 of Daniel F. Comstock, issued January 3,y 1933, it is desirable to provide such a system with a purger to exhaust non-condensable gases from the system. Such a purger thus permits low pressures to be maintained indefinitely in the system despite slight leakage of atmospheric air and the development of a small quantity of non-condensable gases inside of the system.

The present invention is particularly directed Y 2,5 to an improved purger arrangement especially adapted for use in systems of the character disclosed in the above-identified patents. When the quantity of non-condensable gases appearing in such a system is less than the pumping capacity 80 of the purger, refrigerant vapor may be exhausted from the system. However, this exhaustion of vapor does not result in any substantial depletion f the supply of refrigerant in the system even over a very long period of time. Under certain lli operating conditions, however, there may be a tendency for the purger to exhaust liquid refrigerant from the system rather than non-condensable gases and/cr refrigerant vapor. Should the purger thus operate to exhaustliquid refrigerant 4o from the system, the cooler might become denuded within a few weeks, which obviously would be a very objectionable result.

One aspect of the present invention, therefore, relates to the provision of means to prevent the 45 exhaustion of condensed refrigerant from the system by the purger. To this-end the purger supply tube which connects the refrigerant condenser to the purger, preferably is arranged adjoining a hot portion of the system, so that condensate which 50 appears in the tube is revaporized rather than draining to the purger in liquid form.

Purgers `of the type to which the present invention is more particularly directed are provided by drop tubes in which successive globules of liquid u propellant actA as liquid pistons entraining and compressing bodies of non-condensable gases therebetween. When a drop tube of 'conventional steel is used; I have found that the pumping efliciency of the purgerdecreases after a period of time. Under such conditions, the mercury may 6 continue to flow freely through the bore of the tube, but the mercury globules do not continue to pump the non-condensable gases so effectively. The bore-of such a tube may have a thin layer of corroded metal, and it is possible that this in 10 some way affects the surface tension of the mercury so that the latter does not form an effective seal with the wall of the tube, even though the mercury ows freely. In any case, I have found that Ametals which do not corrode are more satis- 15 factory in permitting the purger to operate eiliciently over a long period of time. {I'he present invention provides improvedv purger tubes which permit the effective operation of the purger without substantial leakage between the liquid pistons, and without liability of clogging 'by scale or rust. Such materials should provide a rather smooth and even surface tocontact the liquid globules substantially uniformly, andshould be of a character which does not result in rusting and the formation of scale. y

Ihave found that tubes of rust-resisting, stainless steel may be advantageously employed for this purpose, or that chromium plated tubes may have similar advantages. I have also foundthat a conventional steel tube may be satisfactory, when treated to convert the surface of the metal to form iron and manganese phosphates. While such a tube may not have a surface as smooth as that provided by the stainless steel or chromium plat- V ing, a reasonably uniform surface is provided with which the liquid globules adord effective seals, while rusting and the formation of scale is effectively precluded. f

A further aspect of the present invention relates 40 to the physical arrangement lof the drop tube and the associated piping in a compact assembly. For A f this purpose the drop tube preferably mayV be arranged concentrically within the return duct through which the propellant returns from the lower end of the drop tube to a spill-over connectionl fromfwhich it is supplied tothe vaporizer. Suche compact assembly has distinct advantages, since only supporting means for one tube or duct is required in the framing which supports the system, while the relatively small drop tube is protected from injury in accidental blows or the like. Furthermore, such' an arrangement permits the return duct to have a small effective cross section while being non-capillary, thus reducing 5s body of liquid mercury exposed to the atmosphere,

so that this well is disposed concentrically about the lower end of the drop tube and the lower end of the return duct. Such an arrangement may be conveniently manufactured and may be readily disassembled when it is desired to inspect or replace the drop tube.

.Further features of the invention relate t details of construction and advantageous relationships which I have found desirable in purger assemblies or the like.

In the accompanying drawings: v

Fig. 1 is a diagrammatic view of a refrigerat- Ingsystem provided with an improved purger arrangement constructed in accordance with this invention;

Fig. 2 is an elevational detail of a portion oi' the connection between the purgersupply tube andthe condenser of the refrigerating system;

Fig. 3 is a broken vertical section of the purger assembly, parts being shown in elevation;

Fig. 4 is a view of the purger assembly similar to Fig. 3 but on a larger scale and showing some parts in greater detail;

Fig. 5 is an elevational view of a portion of the sealing arrangement for the purger, parts being broken away;

Figs. 6 and 7 are enlarged sections indicated by lines 6-6 and 11, respectively, of Fig. 4; and

Fig. 8 is a view partly in section and partly in elevation of a port/ion of a purger assembly showing an optional arrangement of the gas venting.

means.

For purposes of illustration, the accompanying drawings show a simple form of refrigeratng system in which the principles of the present inv'ention may be employed, it being understood that in practice these principles may be employed in a system such as disclosed in my copending application Serial No. 171,325 filed October 27, 1937.

A system of this type may be provided with a boiler I provided with an electrical heater Il. The boiler normally contains a body of liquid propellant, e. g., mercury. -Propeilant vapor passes upwardly from the boiler or vaporizer I through a riser duct 2 to an aspirator nozzle 3. Propellant vapor issues at high velocity from the nozzle 3 into the mixing chamber 4, which is connected by a vapor duct 5 to the cooler E. The latter may contain a body of aqueous refrigerant, such as water, or a suitable anti-freeze agent in solution with the water. Refrigerant vapor is drawn from the cooler through the pipe 5 to the mixing chamber 4, where it is entrained in the propellant vapor stream. The mixed vapors pass into the funnel 8 where the refrigerant is compressed and the propellant may be condensed. Suitable cooling means, such as ns I0, are provided to aid the condensation of this propellant.

The refrigerant vapor from the funnel 8 passes upwardly through the duct I3 to the condenser I4, which may be of any suitable type, as shown, being provided with fins I5 to facilitate air cooling. Suitable means I6 forl exhausting air from the system and for thensealing the system is provided on the condenser, such means being fully disclosed and claimed in my copending application Serial No. 136,612, filed April 13, 1937. The condenser is preferably provided with a drum or chamber I1 into which the condensed refrigerant drains. A return pipe I8 is connected to the lower end of this drum to receive the condensate therefrom. 'The lower part of this return pipe is provided with a trap I9 which may contain a body of the heavy propellant liquid. The condensate piling up in pipe I8 above the propellant depresses the propellant in this trap so that refrigerant can leak through the trap and return from the same `to the cooler 6. Stray propellant particles, which passed into the condenser I4 and condensed there drain into the trap I9'to replenish and maintain the body of liquid propellantin that trap.. Propellant overflowing from the trap is received by the cooler andl passes into the lower part of the same, being in turn received by a Mercury condensing in the funnel 8 is received by the leg of a trap 20, the opposite leg of which is connected vby a vduct section 22b to the entraining chamber 22 of the purger 2S (Fig. 2). A purger supply tube 24 has an open end disposed within the lower part of chamber or drum I1 of the condenser and communicates with the entraining chamber 22. Preferably this tube may be provided with a small vent 21 (Fig. 2) in the upper part of the drum I1, this vent being preferably provided with a diametrically disposed wire 28, as more fully disclosed and claimed in the copending application of Eastman A. Weaver; serial No, 168,961 filed October 14, 1937.

Such 'an arrangement permits the purger to continue to exhaust non-condensable gases from the system should the open end of the purger supply tube 24 be immersed in a body of the liquid condensate, for example when freezing occurs in the return duct I8 between the trap I9 and the cooler. Ordinarily, however, a film of liquid con-v densate closes the vent 28 so that the non-condensable gases are received through the open end of the tube 24. l 4

' 'Ihe entraining chamber 22 of the purger may be provided by a tubular member 23. This member is welded to a tube 30 which interts therewith and affords the return duct of the purger. 'I'he drop tube 3l, which is a tube of restricted internal diameter, is provided with an outwardly flared upper portion 32, which rests on the upper i end of the tube 30, as shown in Fig. 2. This flange 'serves to hold the upper part of the drop tube in substantially concentric position within the duct 30. The ange does not have a gas-tight contact with the upper end of the duct 30 or with the surrounding wall of the tubular member 23, so that the pressure in the upper part of the tubular member 30 and the pressure in the entraining chamber 22 may be substantially equalized, although the small vent or crack which is thus provided does not permit the leakage of mercury directly from the chamber 22 in the duct 30.

As successive mercury globules spill over from the duct section 2i)b into the entraining chamber '22, they are received by the drop tube 3l and pass down the same separated by bodies of gas and/or refrigerant vapor. As the globules ilow downwardly through the tube, these bodies are compressed and the non-condensable 'gases and vapor may arise from the bottom of the tube into a body of liquid propellant 38 disposed in a vat 36- surrounding the lower part of the tube and the duct 30. The upper surface of this liquid body is exposed to the atmosphere so that non-condensable gases and uncondensed vapor may bubble up through the liquid body and be exhausted to the atmosphere, while any refrigerant which has condensed in the tube will rise to the top of the mercury body and eventually be` vaporized,

i lojto a decrease in obviously the vat at has a height above'the.

lower end oi' tube 33 suiiicient to permit the mercurylevel in the vat to vary in accordance with the changes in the pressure differential between the interior of the system and the external atmosphere. Thus, for example, the mercury level in vat 36 tends to rise in response to an increase in the internal pressure or a decrease in'the'atmospheric pressure, and tends to fall in response crease in the atmospheric pressure.

The upper part of the duct 33 has a spill-over connection with a downwardly inclined pipe 44, the opposite end of which is connected to a trap 43, the remote leg of the latter providing a drain.

42 to receive propellantparticles which condense in the mixing chamber 4, 'I'he propellant return duct 45 receives propellant overiiowing from the trap 43 and contains a column of the propellant liquid to balance the boiler pressure. Alduct 48 connects the trap 2| to the pipe 44, so that mercury overowing from trap 2| will be received by the pipe 44 as well as the mercury which rises upwardly in the return duct 30 and spills over into the duct 44.

As shown in Fig. 1, the purger supply tube 24 is preferably arranged so that a portion thereof is juxtaposed to the hot funnel 8. Thus the temperature of the lower part of thistube may be substantially higher ythan the condensation point ofthe refrigerant vapor at the pressure of the tube 24, i. e., at the condenser pressure. Accordingly condensation of refrigerant in the sup# ply tube 24 is prevented, while condensate which appears in this tube is revaporized. Thus liquid refrigerant is prevented from passing from the tube 24 into the entraining chamber 22, and accordingly the purger can only exhaust non-condensable' gases or refrigerant vapor from the system, Even if no non-condensable gases appear in the system, the amount of refrigerant vapor which may thusl be exhausted is relatively small even over a period of years.

A cup-like defiector 31 of the type-disclosed and claimed in the copending application of Raymond W. Tibbets, Serial No. 168,958, led October 14, 1937, is arranged about the lower end ofthe return duct 30 but above the lower end of the drop tube 3| lower end of the return duct. For example, the lower end of the tube 3| may be threaded to receive this deector (Fig. 4)

'I'he lower part of the tubular member 30 may be provided with spaced indentations 30* (Fig. 6)

' vengaging the drop tube 3| and serving accurately to center the lower part of the latter relative to the tubular member (Fig. 6). The well 36 has an upper wall 40 with openings 4| through which the interior of the well communicates with the atmosphere. 'I'he innerportlon oi' the wall 4|! is suitably secured to the duct 30, thus supportf ing the vat at the lower part of the purger assembly. The lower end of the well may be provided with an internally threaded opening to receive a screw-threaded plug 43, which may be removed when it is desired to Withdraw the drop tube 3| from the assembly. In order to permit such a withdrawal of the drop tube, and also to permit easy assembly of this portion oi' the system, a suitable sealing arrangement, designated generally by numeral 6|, is associated with the upper part of the duct 23, it being understood that this arrangement is somewhat similar to the sealing means IB associated with the condenser |4. Such sealing devices are disclosed in detail the internal pressure or an inmember.

to deflect gas bubbles away from the lar member 23.

and claimed in my copending applicationI No. 136,(162, filed -April 13,'1937.

'I'his sealing arrangement 6|, which is shown more particularly in Figs. 4 and 5, comprises a metal cup 42 welded to the tubular member 23 of the purger assembly. The rim of this cup is provided with opposite recesses, which have paral.. lei vertical edges, as shown in Fig. 5, and which interiit with complementary projections 63 in the lower portion o1' a cap member 64, to prevent rotation of the cap member. This cap member may conveniently comprise a solid metal cap piece with a ring welded thereto which provides the extension 63.

A sealing ring or washer 35 of yieldable mate'- rial, such as a suitable rubber composition or the like, is disposed between the cap 64 and the bottom of the cup 62, it being understood that the cap 64 is provided withan outer shell portion registering with the outer wall of the cup and providing the protuberances 63. 'I'he inner surface of the bottomwall of the cup 62 and the lower portion of the cap 64 are provided with annular ribs 62* and 64, respectively, w-hich firmly engage with and bite into the rubber sealing member 65, 'I'hus this member may be pressed rmly against the inner surface of the outer wall of the cup, and against the outer surface of the tube 23 when the cap is forced downwardly on the sealing For this purpose, a suitable inverted U-shaped member 66is provided with inturned end portions 10 engageble underthe lower wall of the cup 62. 'I'he bight portion of this member receives a set screw 13 which, when tightened, presses downwardly on the cap 64 and consequently on the sealing member 65 to seal the purger assembly against leakage of atmospheric air. The bight portion oi' the member 66 may be provided with a suitable reinforcement 66e, if desired, to aiford a more sturdy threaded engagement with the set screw.

In orde`r to prevent foreign particlesfrom passing into the machine during assembly, and further to aid the sealing of the device, a small plug 13 formed oi' somewhat yieldable material, such as wood or rubber, may be tted within the upper end of the tubularmember 23.

When it is desired to remove the drop tube for inspection or replacement, theplug 43l is unscrewed from the bottom of the well 36,v thus permitting the mercury to run out of this portion oi' the system. The deiiector 31 is then unscrewed from the lower part of the drop tube 3|, this portion of the tube being slotted. as designated by numeral 3| (Fig. 4) to permit the convenient removal of the deilector.

Since the upper flared portion 32 of the tube merely rests upon the upper end of the tubular member 30, it may then be pushed upwardly if the'sealing asembly 6| has been opened. This may be done by loosening the 'cap screw 13 so that the U-shaped member 66 may be swung out of engagement with the cup 82, whereupon the cap 34 may be lifted from the sealing member 65 and the plug 18 may be removed from the tubu- When the Vdrop tube is replaced, it may readily be dropped into position within the tubular member 30, the ared upper portion oi' the drop tube andthe indentations 3|)Il of the tube 30 positioning the drop tube. The deiiector 31 may then be screwed onto the lower end of the drop tube, the lower extremity 4of the tubular l while afforing openings through which the pro\ pellant may pass. Thereupon the plug 1B may be replaced. The recesses of cap 64 are caused to intert with the protuberances 63 and the U-shaped member 66 is returned to its normal position. The set screw 13 is then tightened firmly to hold the parts in engagement with the sealing member 65.

The arrangement of the annular ribs 62* and 64 permits an unusually firm, dependable, airtight seal. This result is materially aided by the arrangement of the protuberances 63 interiitting with the corresponding recesses ofthe cap 6I, thus preventing rotation of the cap relative to the sealing member 65 as the set screw is tightened or loosened and avoiding possible scoring of the material of the sealing member by irregularities in the surfaces of the cup and cap which engage that member.

Preferably the bore of drop tube 3i is accurately formed with an inner surface that will remain uniform over a long period, not deteriorating or oxidizing readily in the presence of water vapor and air and maintaining an effective seal with the mercury globules. For this purpose I may employ a corrosion-resistant stainless steel or nichrome, although chromium plating can also be employed for this purpose, and I have also found that a treatment which results in converting the surface of a conventional steel tube to form iron and manganese phosphate is particularly advantageous for this purpose. When materials of this character are employed any danger of the ultimate choking of the small diametered purged tube by rust or scale particles is also avoided.

Fig 8 shows an optional construction which may be employed at the upper part of the vat 3G for venting the non-condensable gases. In this form of the invention the vat is provided with an annular cover plate I0 and a vent tube 4In extends laterally from the upper part of the vat and affords an open outlet end at an appreciable distance therefrom. Obviously the noncondensable gases are vented through the tube Il* in the same manner as has been described with reference to the vent openings 4I The construction shown in Fig. 8 is advantageous since a receptacle may readily be arranged under the open end of the tube 4|Il to catch mercury should the same overflow from the vat due to any abnormal condition, such as the leakage of a substantial quantity of atmospheric air into the system and a consequent material increase in the internal pressure thereof. Such a receptacle may conveniently be suspended from the end of the tube Il or may be placed below the end of the tube in any convenient location.

It is evident that the present invention affords a simple, efficient and compact purger assembly which may operate satisfactorily over a long period of time, that the exhausting of liquid refrigerant from the system by the. purger is prevented, and that the drop tube may readily be removed and replaced when and if necessary.

It should be understood that the present disclosure is for the purpose of illustration only and that this invention includes all modifications and equivalents which fall within the scope of the appended claims.

them to the exterior atmosphere, a lduct connecting the condenser to the purger, said duct being in heat transfer relation to a part of the circuit which is kept warm by the heater so that condensation of vapor from the condenser is precluded in said duct, whereby the purger is prevented from exhausting liquid-from the system.

2. Apparatus of the class described comprising a heater, a fluid circuit through which fluid is circulated by energy received from the heater, a condenser 4included in said circuit, a purger for receiving non-condensable gases and exhausting them to the exterior atmosphere, said purger including a tube o1' restricted diameter wherein successive falling globules of liquid pump bodies of gas, a duct connecting the condenser to the upper end of said tube, said duct being in heat transfer relation to a part of the circuit which is kept warm by the heater so that condensation of vapor from the condenser is precluded in said duct, whereby the purger is prevented from exhausting liquid from the system.

3. Apparatus of the class described comprising a circuit for a heavy, high-boiling point propellant including a boiler, an aspirator nozzle, a propellant condenser, and a return pipe to direct condensed propellant to the boiler, a circuit for refrigerant including a cooler, a refrigerant condenser, and a part in common with the propellant circuit where the refrigerant is pumped by aspiration, a purger receiving condensed propellant from the propellant condenser, said purger including a drop tube wherein successive globules of liquid propellant entrain bodies of gas, means for receiving propellant from the lower end' of the tube and directing the same to the return pipe and for exhausting the gas to the atmosphere, and a duct to direct gas from the refrigerant condenser to the upper end of the drop tube, said duct having a part in heat transfer relation to a Warm part of the propellant circuit to preclude condensation of refrigerant vapor therein.

4. Apparatus of the class described comprising a circuit for a heavy, high-boiling point propellant including a boiler, an aspirator nozzle, a. propellant condenser, and a return pipe to direct condensed propellant to the boiler, a circuit for refrigerant including a cooler, a refrigerant condenser, and a part in common with the propellant circuit where the refrigerant is pumped by aspiration, a purger receiving condensed propellant from the propellant condenser, said purger including a drop tube wherein successive globules of liquid propellant entrain bodies of gas, means for'receiving propellant from the lower end of the tube and directing the same to the return pipe and for exhausting the gas to the atmosphere, and a duct to direct gas from the refrigerant condenser to the upper end of the drop tube, said duct having a part in heat transfer relation to the propellant condenser to preclude condensation of refrigerant vapor therein.

5. Refrigerating apparatus of the class described comprising a refrigerating circuit including a cooler and a condenser, a purger, a supply tube to direct non-condensable gases from the condenser to the purger, a propellant circuit including a boiler and having a part in common with the refrigerant circuit where propellant vapor entrains and pumps refrigerant vapor from the cooler to the condenser, said supply tube having a portion in heat transfer relation to a warm portion of the propellant circuit to preclude the condensation of refrigerant in said tube and thus to prevent the exhaustion of appreciable liquid refrigerant from the system, saidv purger includrounding the lower part of'said Vdrop tube and ing a drop tube of restricted diameter through which globules of propellant liquid pass, entraining bodies of non-condensable 'gases therebetween, a vat containing a body of propellant liquid to receive the globules and the bodies ofnon-condensable gases from the lower end of the drop tube, and a return duct arranged concentrically about the drop tube vand receiving propellant therefrom, the upper part of said return duct being provided with a spill-over connection from which propellant is returned to the boiler.-

6. A system of the class described comprising a drop tube pump in which successive liquid bodies entrain and pump bodies of a lighter iiuid,` a return duct surrounding the tube, a receptacle communicating with the lower parts of the tube and duct, said receptacle containing` a body'of the pumping liquid, the lower end of the tube extend--y ing below the lower end of the duct; said tube ,having an outlet opening,below the duct, said duct having an inlet opening above the lower end of the tube, whereby the pumping liquid from said tube may pass into the liquid body and liquid from the latter may pass into said duct, while the lighter fluid may rise to the surface of said liquid body. i i

7. Apparatus of the class described comprising a fluid circuit including a condenser .which normally operates at subatmospheric pressure, a

`purger assembly connected tothe condenser to Ireceive non-condensable gases therefrom, said assembly 'including an entraining chamber receiving circulating liquid inthe form of separate liquid globules, and receiving non-.condensable gases from the condenser, a drop tube, a vat surreceiving liquid and non-condensable gases therefrom, said vat containing a body of liquid with its surface exposed to atmospheric pressure, a tubular member having its lower end immersed in said body of liquid and being arranged concehtrically about said drop tube, the upper part of said tubu- 4 lar member being provided with a spill-over connection with the interior of the system,V whereby l liquid may rise from the vat into the space between said tubular member and said drop tube.

8. Apparatus of the class described comprising la drop tube assembly including a drop tube'to receive liquid globules and bodies of a lighter fluid entrained therebetween, a tubular member surrounding. the drop tube, the upper portion of the tube being dared and resting upon the upper end of the tubula'r member, and an outer metal tube secured to the tubular member and extending above the end of the drop tube to aifcrd an entraining chamber, a` vat containing a liquid body in whichthe lower end of the drop tube and of the tubular member are immersed, the upper part of said tubular member having a spill-over connection to receive liquid from said liquid body, said assembly normally operating at a subatmospheric pressure and the arrangement of theared end of the drop tube resting upon the end of the tubular member, permitting equalization of pressures in the entraining chamber above the flared end of the drop tube and in the-space between the drop tube and tubular member, while pre.

4member having its lower end immersed in said body of liquid and being arranged concentrically about said drop tube, the upper part of said tubularmember being provided with-a spill-over connection with the interior of the system to receive liquid which has risen from the vat into the space between said tubular member and said drop tube, a small vent connecting -said space with the entraining chamber, whereby the pressures in said space and chamber may be equalized but where-i by the flow of liquid through said ventvis substantially precluded. a

10. Apparatus of the class described comprisingia fluid circuit including a portion which normally operates at sub-atmospheric pressure, a

purger assembly connected to said portion to receive non-condensable gases therefrom, said assembly including an entraining chamber receiving circulating liquid in `the form of separate liquid globules and vreceiving non-condensable gases from said portion, a vat surrounding the lower part of said drop tube and receiving liquid and non-condensable gases therefrom, said vat containing a body of liquid with its surface exposed to atmospheric pressure, a. tubular member having its lower end immersed in said body of liquid and being arranged concentrically about said drop tube, the upper part of said tubular;

member being provided with aspill-over connection with the interior of the system to receive liquid which may rise from the vat into the space between said tubular member and said idrop tube, a small vent connecting said space with the entraining chamber, whereby the pressures in said space and chamber may be equalized but whereby the flow of liquid through said vent is substantially precluded, and a sealing assembly associated with the entraining chamber, said sealing assembly including portions clamped together effectively to seal the chamber against the leakage 4of* atmospheric air but capable of disassembly to permit the removal of the drop tube by its yupward movement through the tubular member and the entraining chamber.

11. Apparatus of the class described compriss ing a fluid circuit including a portion which normally operates at subatmospheric pressure, a purger assembly connected to said portion to receive non-condensable gases therefrom, said assembly including an entraining chamber receiving circulating liquid in the form of separate liquid globules and receiving non-condensable gases from'said portion, a drop tube, a vat surrounding the lower part of said drop tube and receiving liquid and non-condensable gases therefrom, said vat containing a body-of liquid with its surface exposed to atmospheric pressure, a tubular member having its lower en d immersed in said body"of liquid. and being arranged concentrically about said drop tube, the upper part of said tubular member being provided with a l spill-over connection withl the interior Iof the system, whereby liquid may rise from the vat into the space between said tubular member and said drop tube, and a sealing assembly associated with the entraining chamber, said sealing assembly including portions clamped together effectively n to seal the chamber against the leakage oratmospheric` air but capable of disassembly to permit the removal of the drop tube by its upward movement through the tubular member and the entraining chamber.

12. A drop tube assembly of the class described comprising a drop tube of restricted internal diameter, said drop tube having a ared upper end, an entraining chamber above the upper end of the drop tube and arranged concentrically in relation to the same, a return duct arranged concentrically about the drop tube below its iiared upper end, a vat surrounding the lower end of the drop tube and the return duct, a removable plug in the bottom of the vat, and a sealing assembly at the top of the entraining chamber, said assembly normally being closed to seal the entraining chamber against leakage of atmospheric air, said assembly being capable of being opened so that when the plug is removed from the bottom of the vat the drop tube may be pushed upwardly through the opened sealing assembly.

13. Apparatus of the class described comprising a refrigerant circuit including a condenser and a cooler which operate at subatmospheric pressures, a purger assembly receiving non-condensable gases from the condenser, said assembly including a drop tube of restricted diameter in which successive liquid globules pump and compress non-condensable gases, an entraining ing a refrigerant circuit including a cooler and,

a condenser, said cooler containing an aqueous refrigerant, pumping means to cause the circulation of refrigerant through said circuit, a heater supplying energy to said pumping means, a purger, a supply tube receiving non-condensable gases from the condenser and directing the same to the purger. 'said supply tube having a portionl the arrangement of the'supply tube to 'receive heat from the heater preventing the exhaustion of condensed refrigerant from the system, while the corrosion resistant wall of the drop tube pre- `ventsdeterioration of the tube andl impairment of the pumping eiilciency of th purger due to corrosionin the presence of gases and refrigerant vapor. Y

l5. A drop tube assembly of the class described comprising adrop tube of restricted internal diameter having an inner surface providing a smooth relatively uniform face for contacting successive liquid globules so that the globules may afford effective seals with the surface of the tube, said surface being resistant to corrosion in the presence of water and air, a return duct arranged concentrically about the tube, a vat surrounding the lower part of the tube and of the return duct, said vat containing a body of liquid with its surface exposed to the atmosphere, a spill-over connection at the upper part of the return duct, and an entraining ch'amber receiving liquid and non-condensable gases and supplying liquid globules and bodies of non-condensable gas to the upper end of the drop tube.

'16. A purger assembly of the class described comprising a metal drop tube ofv restricted internal diameter in which successive liquid globules compress and pump bodies of non-condensable gases, said tube having an inner surface providing a smooth, relatively uniform face for contacting successive liquid globules so that the globules may afford effective seals with the surface of the tube. said surface being resistant to corrosion in the presence of air, whereby the surface of the tube may continue to aiIord an effective seal with the liquid globules and whereby corrosion of the tube and possible choking of the same by scale is prevented.

LYMAN F. WHITNEY.

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