US2321964A - Purge system for refrigerative circuits - Google Patents

Description

Ju'ne 15, 1943. w. E. ZIEBER PURGE SYSTEM FOR REFRIGERATIVE-CIRCUITS 2 Sheets-Sheet- 1 Filed Aug. 8. 1941 QN A Noimongm Isdn uuMnl Zmventor dowwmmuoo Gttcrnegs June 15, 1943. l w. E. zlEBER PURGE SYSTEMAFOR REFRIGERATI'VE CIRCUITS Filed Aug. 8', 1941 2 sheets-sheet 2 E. w23 n50:

. xdUW ZUB ZOU A ahw) nnentor Patented June 15,

PURGE SYSTEM FOB REFRIGERATIVE CIRCUITS l William E. Ziebcr, York, Pa., assignor to York Ice Machinery Corporation, York, Pa., a corporation of Delaware f Application August 8,1941, serial No. 406,061

' (c1. sz-115)' 13 Claims.

This invention relates to refrigeration and particularly to purging systems for use with refrigerative circuits. While the invention can be arranged for manual control, a feature is the pro-v vision of automatic means which render manual control unnecessary and which respond to condiv tions within the system indicating the need of the purging operation.

The invention is of marked 'utility in connec- I tion with refrigerants of the Freon class and generally with refrigerants with which lubricating oil is freely miscible, particularly .those in which the miscibility is vcharacteristic of all degrees of oil concentration. Wherethis is the case, gravity separation of the lubricant from the refrigerant is impracticable so that special provision must be made for the desired separation. Refrigerants having this character of miscibility with the oil are typified by the Freon group and the discussion will be based on the use of Freon simply as examples and without implying any necessary limitation to this particular field. Freon is a trade name, and various types of the general class areV distinguished by numbers as F-11,F12,etc.

The invention is useful in any refrigerating plant in which the evaporator, or both evaporator and condenser operate below atmospheric pressureand hence are subject to in-leakage of air and water vapor during normal operating periods. Leakage, of course, is not a normal function but it cannot always be prevented. In an air conditioning system, to take one familiar example, the evaporator is commonly operated at the circuit as completely as is reasonably practicable.

With certain refrigerants commonly used in air conditioning the operating pressure ranges are rather low so that there is a tendency for atmosatmospheric air always contains some water vapor, the entrance of air is attended with the entrance of water in the vapor phase. The operation of most compressors is such as to cause mix- The invention provides for the segregation of V elimination of the oil separator.

y pheric air to enter the refrigerative circuit. Since ture of some lubricating oil with the refrigerant.

such oil from 'the refrigerant. vThe segregation of the oilis automatic but its removal from the circuit is preferably under manual control.

The operation cf the purging system for separating and rejecting the air is fully automatic. The separation of the water is automatic, the quantity is not great enough to render automatic discharge worth the extra complication.

To embodiments of the invention are shown, one involving the use of a small secondary reciprocating compressor to withdraw refrigerant, air and water vapor from the condenser and deliver them to a secondary condenser, and the other involving the use of a secondary condensing coil operated at a temperature so low as to make the use of a compressor unnecessary. Such a low temperature condensingcoil forming part of the purge device is peculiarly desirable in plants.,

where a low temperature cooling liquid or a low temperature refrigerant is rendered available by extraneous meansl because low temperature permits eicient purging. Elimination of the secondary compressor, in plants in which the main compressor is of the centrifugal type, permits Reciprocating compressors are likely to contaminate the refrigerant with oil and their elimination reduces the oil problem practically to the vanishing point.

' Two types of automatic control for the purgel device are disclosed, and either may be used with either of the two embodiments just mentioned. These two controls are characterized, one by a rather wide control range which ordinarily gives sufliciently precise control, and the other by a very narrow control range, which is required in cases where temperature and pressure in the main condenser are rather. l'ow and condensation of water vapor in the condenser may occur unless a precise purge control is afforded. Low condenser temperatures are encountered in known types of circuit in which cascade cooling is used, i. e., cooling of the .main condenser by an auxiliary refrigerating circuit.

Generally stated, according to the invention, av

mixture of refrigerant vapor, water vapor and air is drawn from Athe main condenser and delivered to a secondary purging 'condenser which is operated at a lower temperature than the main condenser. If this temperature is suiliciently low, no secondary compressor is neede'd, but in most cases, it is desirable to use a compressor towithdraw refrigerant vapor with air and water vapor from the main condenser and deliver them under oiftake.

elevated pressure to the secondary condenser. In thisv secondary or purge condenser, the refriger- V ant isliquefied almost completely so that the sures) to` liquefy all of the refrigerant. Theliquefied refrigerant is returned to the system after a gravity separation of Water therefrom, and on its way back to the system may be fed through the evaporative cooling coil of the secondary or purge condenser. In this condenser the oil is deposited and flows to a bailied oil-separator which may be drained from time to time. The vaporous refrigerant, thus freed of air, water and oil returns to the low side of the main circuit.

The automatic control puts the purge circuit into operation whenever air is present in the condenser in excess of a chosen proportion When the purge device operates, air mixed with a minimum quantity of refrigerant is discharged from the circuit. All water is separated from the liquid refrigerant and discharged. The refrigerant (includingl if desired, some drawn from the main condenser) is freed of oil and returned to the low pressure side of the main refrigerative circuit. As stated, except for draining off of the oil and of the Water, each of which is required at relatively long intervals, the operation of the system is completely automatic.

Preferred embodiments of the invention will now be described by reference to the accompanying drawings.

In the drawings:

Fig. 1 is a diagram, partly in section, showing the embodiment using a secondary compressor, and a controller ofthe differential pressure type.

Fig. 2 is a section on the line 2-2 of Fig. 1.

Fig. 3 is a fragmentary view of the Weir notch through which the liquid refrigerant flows.

Fig. 4 is a sectional view of a protective valve used on the air vent line. l

Fig. 5 is a fragmentary view of the local c ooler associated with the purge offtake from the Vconcompressor is omitted.

Embodiment of Figs. 1-5

The main refrigerative circuit comprises an evaporator II Aof any type, a compressor I2 of any type (but here assumed to be of the centrifugal type), drawing vaporous refrigerant from evaporator I I and delivering it at higher pressure to condenser I3 which ordinarily would be of the Water-cooled shell and tube type. Any cooling medium can be used in the condenser.

Refrigerant liquefied in the condenser collects in the receiver f4 from Awhich itis fed to the evaporator II by any suitable controlling mea'ns conventionally indicated at `I 0.

Communicating freely with the vapor space in condenser I3 by port I5 is a cooled purge-oiftake chamber I6 (see Fig. 5). This is cooled by any means such as coil I1 through which a cooling uid is circulated. The purpose is to cool chamber I6 below condensing temperature and thus stimulate a free flow of non-condensable gases (chiefly air) to the chamber and thence to the The cooling fluid may, for example,'be

condenser cooling water on'its way to the main water spaces of the condenser I3, and hence cooler than the condenser, but this is a matter of detail.

The purge oitake line I0 leads from chamber I 6 to the intake of secondary compressor I9 which discharges through check valve 2| and air-cooled condenser 22 to the purge drum 23 in which is mounted the secondary condensing coil 24. The condenser 22 is :merely an economlzer and may be omitted. The check valve 2I is important because it preventsreflux of water to the compressor I9 when the latter stops. This water has been found to have serious corrosive action upon' the compressor if allowed to flow back to the compressor when. the latter stops, To thesame end the pipe connections from check va1ve'2l to 'purge drum 23 are made small so that high ow rates (say 1,000 ft. per minute or more) are had, the purpose being to sweep water droplets toward drum 23 and prevent retention of slugs of water in the piping.

Coil 24 is fed with liquid refrigerant and oper- `ates at substantially the pressure and temperature of evaporator il, as will later appear. It condenses the major portion of the refrigerant entering drum 23. The air and a small amount of uncondensed refrigerant discharges through the loaded relief valve 25 which controls air vent pipe 25.

The relief valve 25 can be used alone, but because such valves sometimes fail to seat tightly,

, a protection valve 21 is interposed between drum 23 and valve 25. The structure of the protection valve is shown in Fig. 4, and since the valve is of known mechanical construction (but heretofore used for a wholly different purpose) only a brief description is needed.

The valve proper 28 opens in the direction of flow toward valve 25. It is loaded in a closing direction by coil compression spring 29. The

y spring loading is opposed by pressure in drum 23 communicated through tube 3l to bellows 32,

' causing the bellows to react in a. valve opening direction on stem 33 which engages the valve 28. Bellows 34 form a packless seal for stem 33. The loading of spring 29 isv adjustable and is so set that the valve 28 closes except when purging pressures exist in drum 23, at which time it opens and transfers vent control to the loaded vent valve 25. Yalve 2 will close tightly at other times. 'Hence valve 25 will not weep continuously even though its seat should become scored.

The valve 25 is simply a spring loaded relief valve set to open when chamber 23 is at purging pressure, and by purging pressure is meant'a pressure substantially higher than the pressure corresponding to the temperature of the coil 24 as determined by the thermo-dynamic properties of the refrigerant used in circuit I I, I2, I3, I4.

This can be illustrated by a practical example.

VAssume that the refrigerant is F-11 and that the evaporator II operates to cool water to 40 F.

The evaporator II would operate at a, pressure of about 6 lbs. per sq. in. absolute and the condenser would operate at about 10 lbs. gage, assuming cooling water at about F. With the connections as shown in Figure 1, the refrigerant is slightly below the bottom of notch di.

through the valve 25, which is adjusted to open only in the relatively high pressure range above suggested.

Refrigerant liquefied in drum 23 passes by dip pipe 35 to the gravity separation chamber 36, shown formed as a downward extension of drum 23. The entire structure is insulated to minimize the entrance of heat, such insulation being indicated at 30. The arrangement of chamber 38 will be clear from a consideration of Figs. -`1, 2

and 3.

There is a water overow weir comprising a weir notch 31 in partition 38 controlling now to water collecting sump 39. There is a refrigerant overilow weir comprising a weir notch 4| in partition 42 controlling ilow to refrigerant collect chamber 63. y

Since the refrigerant isassumed te have a higher specic gravity than water, the notch 3l is slightly higher than notch dl. To facilitate gravity separation in chamber 88 at least one vertical cross bame dd is used. Two bales are shown and their function is to suppress turbulence caused by the entrance of liquid through dip pipe 35. The bottom edge oi bame dt is above the bottom of chamber 36 and the top edge Thus notch 3l skims water ofi'. The rate of horizontal liquid now in chamber 36 should be low, say six to twelve inches per minute. Refrigerant, thus freed of Water, passes below a dip partition t5 to reach weir notch di. Any freely miscible oil would travel with the refrigerant.

Water is drained away from sump 39 by manually opening valve dt. li'loat control of valve S8 woyld be an unnecessary complication since the amount of water to be discharged is small. However', the discharge from chamber d3 is iloat controlled, the drain line di leading to a high side float valve t8. A' pressure equalizing connection 49 to the vapor space in purge drum 23 is pro,

vided. A oat valve similar to t8 could replace valve d6, and such a substitution would involve only mechanical skill. v

Refrigerant passing through valve It is led by line 5I to the entrance (upper) end of coil 28 which is carefully designed to drain all oil precipitated therein to its lower discharge end. This oil might, for example, enter the system at the reciprocating secondary compressor I9. The system. need not withdraw oil with refrigerant from condenser I3 where compressor i2 is of the centrifugal type, since contamination of refrigerant by oil does not occur to any appreciable extent in such compressors. However, if the main compressor is of the reciprocating type some of the oil which might then become mixed with refrigerant would pass from condenser I3 through expansion valve 52, about to be described, and

' would be separated by the oil separator 5l.

Snce the refrigerant passing" valve d8 is insuiilcient to supply the demands of coil 2d, an automatic expansion valve 52 of the superheat control type is interposed in a connection 58 between leaving the coil and affecting the temperature of bulb 34 will be slightly superheated. l

Refrigerant leaving coil 28 and oil draining therefrom pass by connection 56 to one end of oil separator drum 51 which has ballles 58 for arresting oil droplets and a manually operable normally closedoil drain valve 58. 'I'he other end of the drum is connected by line 6I with evaporator Il, i. e., to the low side of the main refrigerating circuit. As stated, the system can operate to` the invention provides for recovery of some but not all of the oil entering the main condenser. Since the valve 52 isalways eiiective to feed coil 24, some oil separation is occurring from time to time irrespective of the cycling of the purge device as long as the main compresser operates.

The purging circuit above set forth is active only when conditions in the condenser are such as to require purging. This is evidenced by rise of condenser pressure unduly above the pressure corresponding to the temperature of liquid refrigerant in the condenser. At such times the compresser I9 is operated. At all other times the compressor is inactive.

Compressor I8 is driven by electric motor t2 which receives current from lines 63, $8 through normally closed switch 65. A control switch 68 operated by opposed bellows motors 6l, 68 reacting upon lever 89 which is iulcrumed at 'II starts and stops motor' 62 according to conditions in condenser i3. Bellows motor 6l which acts in a switch closing direction is subject to pressure in the vapor space in condenser I3. Bellows mot/or 88 which acts in a switch opening direction is connected with a thermostatic bulb 'I2 submerged in liquid refrigerant in condenser I3 and containing a volatile liquid, conveniently of the same composition as the liquid refrigerant, so as to have identical thermal characteristics. A spring I3 gives a moderate opening bias to the switch.

Such a switch will run motor 62 and compressor I9 whenever condenser pressure is out of ,line with the'temperature at which the condenser is operating. 'I'he device cannot; be arranged for very precise control but is commercially satisfac tory.

Precise control, Fig. 6

When comparatively precise control is desired, the control mechanism illustrated in Figure 6 is used in lieu of the parts 88 to I3 inclusive. In Figure 6 only suilcient mechanism is'illustrated to make clear how the precise control mechanism is substituted, and parts which are identical with parts in Figure 1 are given the same reference numerals used in Figure 1 but with the distinguishing letter a.

erant to coil 2t at rates such that refrigerant 75 A loadedfvalve 8| is interposed between line I8a which is the suction line to the secondary compressor, and the chamber [6a which is in free communication with the vapor space in the condenser I3a by way of the non-restricting opening l5a. The valve 8| is adjusted to produce a small pressure drop between the chamber Ita and the suction line I8a, the purpose being to ensure that when the secondary compressor is running the suction line I8a will be maintained at a pressure below the pressure in the condenser I3a.

A drum 82 is -in free communication with the chamber Ilia by way of the pipe 83. It is important that this pipe be large enough to permit free flow. The drum 82 is also connected at its bottom with the liquid space in the condenser |3a by way of the pipe 84. 'I'he drum 82 is in restricted communication with ,the suction line I8a by way of the choke 85 scr that when the secondary compressor runs there is retarded flow from the drum 82tot trie suction line I8a.

In the drum 8,2 isis:refrigerating surface or coil 88 which must @be operated at a temperature below, usually atleast to 25 degrees below, the lowest temperature which is ever maintained-in the condenser |3a. It is convenient to refrigerate this coil by evaporating liquid refrigerant in the coil, but cold water or brine may be circulated through it.

Details of the supply and return connections to the coil 86 are not illustrated because they would be conventional in any event and are sub- A ject to wide variation.

A thermostatic switch of the insertion type is illustrated at 81. The thermally responsive element extends axially through the chamber 82 so as to be subject to the temperature of gaseous medium in that chamber. 'I'he thermostatic switch 81 is adjusted to close on fall of temperature to a value below temperature in condenser |3a and preferably'only a few degrees above the temperature at which the coil 86 is maintained. The thermostatic switch 81 controls the motor 62a which is the driving motor of the secondary compressor.

Assume now that the motor 62a and the secondary compressor driven thereby are not running. Because the coil 86 is at a lower temper- ,ature than the condenser |3a, vaporous refrigerant will enter freely through the pipe 83, c ondense in the drum 82 and drain through the pipe 84. Whatever the temperature of thel coil 88 may be, refrigerant would enter and condense at a rate suiilcient to absorb the entire refrigerating effect of the coil. Thus the temperature of gaseous media in drum 82 is that corresponding to the pressure in condenser |3a and nothing happens so long as no air is present. If air be present in the condenser |3a it will enter the drum 82 with the vaporous refrigerant and will accumulate in that drum. Ulti- :mately the concentration of air will become such lthat little vapcrous refrigerant can enter, conl densation `of refrigerant in drum 82 is reduced, and the coil 86 becomes effective to reduce the temperature of the gaseous media in drum 82.v

This fall of temperature ultimately causes thermostatic switch 81 to start the motor 62a.

When this happens the secondary compressor will draw vaporous refrigerant and air in substantial quantity through the valve 8| and in limited quantity through the choke 85.

The flow capacity of choke 85, the pressure differential imposed by the valve 8|, and the volume of the chamber 82 are so coordinated that the chamber 82 will not be too rapidly swept free of air. If the secondary compressor could draw freely from the drum 82 this drum would be quickly freed of air and the motor 62a would promptly be shut down by the thermostatic switch.

Modified embodiment, Fig. 7

In this ligure the control of Figure 6 is shown. Parts identical 'with Figures land 6 aregiven the same identifying numeral with the letter b.

Tooperate such a system there must be some means (cold brine or volatile refrigerant) for cooling the coil 24h to a sufficiently low temperature to ensure eilicient operation. The secondary compressor |9 is omitted because low temperature implies low pressure in drum 23h. Connection |8b leads directly to purge drum- 2 3bto which flow occurs because the drum is always below condenser pressure.

An electrically operated valve 9| of limited flow capacity controls this connection, is normally closed and opens when winding 93 is excited. The iiow of cooling medium through coil 2lb is desirably (but not necessarily) controlled by a similar electrically operated valve 92 which is normally closed and opens when winding 94 is excited. An adjustable by-pass 90 permits limited flow past valve 92 when the latter is closed so that coil 24h is never completely inactive. The reduction vof flow through coil 2lb is simply in the interests of economy. Thermostatic switch 81h closes the circuit through windings 93, 94 when temperature in drum 82h falls below a chosen value. The importa'nt function is that valve 9| (and valve 92, if used) shall open when purging is needed, i. e., when temperature in drum 82h falls below a chosen Value.

An important relationship is that the total condensing capacity of coil 2lb when valve 92 is open shall exceed the flow capacity by way of the valve 9|, so that coil 24h when active will cause a decided pressure drop in drum 23h.

The arrangement described is simply a convenient one of several which might be devised by persons skilled in the art to secure the desired result. 'I'he control used in Figure 1 is obviously adaptable.

As in the device of Figure 6, valve 8| b is set for a moderate pressure ldrop between condenser |31) and line |8b, andits setting is coordinated with the volume of chamber 82h and iiow capacity vof choke 85h to ensure properly sustained purging.

Float valve 48h delivers recovered refrigerant directly to evaporator IIb in the preferred arrangement, illustrated. This is practicable for two reasons; the coil 24h is here illustrated as cooled `by extraneous means, so the refrigerant need not be fed to that. No oil separator drum such as the part 51 of Figure l is'here required in view of the omission of the secondary compressor, and the assumed use of a main compressor of the centrifugal type.

Consideration of Figure 7 will indicate that the resistance of the back pressure valve 8|b, the now resistance through connection |8b and valve 9| and the pressure range required for operation of the valves 2lb and 25h impose the requirement that the valve 25hl must open at some presit is ldesirable that the coil 2lb operate at a lcw temperature.

To assume a practical example and without yimplying any limitation to the values stated, itv

will be assumed that the condenser IIb is operated at lbs. per sq. in. gage and the purge valve h opens at approximately 2 lbs. gage. The coil 24h at whatever low temperature it is operated, should have a condensing 'capacity so related to the ow capacity of valve 8| for vaporous refrigerant thatin the absence Vof air in drum 23h a pressure will be established in the purge drum 23h lower than the opening pressure of valve 25h, here assumed to be 2 lbs. gage.

Under these conditions if air is present in the condenser |312 and causes the mechanism in the drum 82h to open the valves 9| and 92, air will accumulate in the purge drum 23h. Thus pressure which would initially be below the setting of the valve 25h would gradually rise with the increasing concentration of air and the consequently reduced condensing effect of coil 2th until the valve 25h would open. This opening would occur only when the`air concentration in the drum 23h is considerable. As a practical matter, the opening of the valve 25h is intermittent, the opening of the valve serving to reduce the air concentration and its resulting closure initiating a new increase-of concentration.

General considerations The valve 2-5 in the arrangement of Fig. 1 will also open and close for similar reasons at times. When the compressor I9 starts the air concentration will -be high and valve 25 may remain open continuously for a considerable period but in time, and .before compressor I9 shuts down, the air concentration will have been reduced so that valve 25 will close and open. alternately, the openl periods tending to become shorter .because the rate of delivery of air to drum 23 diminlshes.

Both the embodiments of Figs. l and '7 have the word "air being used in a loose sense as .typif'ying any non-condensable gas or mixture of non-condensable gases which might be present in the refrigerative circuit, and the claims should be interpreted on this understanding.

What is claimed is:

1. The combination of a refrigerative circuit containing a volatile refrigerant and including a condenser; a purge drum; a loaded ventvalve controlling flow fromy said drum and set to openwhen pressure in the drum exceeds a definite value; refrlgerative means serving to cool gases in said drum to a temperature which for said refrigerant is substantially lower than that.corre. spending to said pressure; means for returning condensed refrigerant from said drum to said circuit; means for delivering from the'condenser to the drum, at a pressure higher than the setting' of said vent valve, vaporous refrigerant', and air when air is present in the condenser; and a controller responsive to the presence of air in the condenser and including a thermally responsive element, said controller serving to control the last named means.

2. The combination of a refrigerative circuit containing a volatile refrigerant and including a condenser; a purge drum; a loaded vent valve controlling flow from said drum and set to open when pressure in the drum. exceeds a denite in said drum to a temperature which forsaid refrigerant is substantially lower than that cor.

responding to said pressure; means for returning condensed refrigerant from said drum to said circuit; means for delivering from the condenser to the drum, at a pressure higher than the setting of said vent Valve, vaporous refrigerant, and air when air is present in the condenser; and means responsive to pressure-temperature relations in the condenserserving to control the last named means.

3. The combination of a refrigerative circuit containing a. volatile refrigerant and including a condenser; a purge drum; a loaded vent valve controlling ow from said drum and set to open when pressure in the drum exceeds a definite value; refrigerative means serving to cool gases in common the idea of controllable purging circuits in response to condenser conditions, and the incorporation in the purge circuit of cooling means and a pressure operated purge valve which coact to ensure purging now at times when the air is present to the practicable maximum and Vaporcus refrigerant is present only to the practicable minimum in the mixture in drum 23h.

Two embodiments of the purge circuit and two specifically different control mechanisms have been described, with the idea of illustrating the in said drum to a temperature which for said refrigerant is substantially lower than that corresponding to said pressure means for returning condensed refrigerant from said drum to said gcircuit; means for delivering from the condenser non-condensable gases. In most circuits, air will 1 cication and in certain of the claims as typifying the non-condensable gas to be purged.

The invention is not limited to purging air and the claims are not intended to be limited to'air,

to the drum, at a pressure -higher than the setting of said vent valve, vaporous refrigerant, and air" when air is present in the condenser; and means for creating a vapor-air atmosphere substantially at condenser pressure and in which the air is concentrated by flow from the condenser and condensation of refrigerant 4vapor therefrom; and temperature responsive means in said atmosphere -and connected to control said delivering means.

a.v The combination deined in claim' 1 in which the delivering means comprises va motor drivencompressor controlled by said controller and having its suction connected with the'vapor space of the condenser and its discharge connected with the purge drum, and the loaded vent valve is set to maintain the purge drum at a pressure higher than that in the condenser.

5. The combination defined in claim 1 in which the delivering means comprises a motor actuated valve of restricted flow capacity controlled by said controller and interposed between the condenser and the purge drum.' and the refrigerative means operate at a temperature so low Ithat the purge valve is set to open at a pressure lower than condenser pressure.

6. The combination of a refrigerative circuit containing a volatile refrigerant and including a condenser; a purge drum; a. loaded vent valve controlling flow from said drum and set to open when pressure in the drum exceeds a definite value; refrigerative means serving to cool gases in said drum to a temperature which for said refrigerant is substantially lower than that corresponding to said pressure; a connection for returning condensed refrigerant from said drum controlling flow from said drum and set to open whenA pressure in the drum exceeds a definite value; refrigerative means serving to cool gases in said drum to a temperature which for said refrigerant is substantially lower than that corresponding to said pressure; a connection for returning condensed refrigerant from said drum to said circuit; a water separator of the gravity type in said connection; an evaporator also in said' connection beyond said Water separator, and in which refrigerant is evaporated and oil, if present is trapped; and means for deliveringA from the condenser to the drum, at a pressure higher than the setting of said vent valve, vaporous refrigerant, and air when air is present in the condenser.

8. The combination cfa refrigerative circuit containing a. volatile refrigerant and including `a condenser; a purge drum; a pressure operated vent valve controlling purging flow from said drum and arranged to open when pressure in the drum exceeds a chosen pressure; refrigeratlng means for cooling gaseous media in said purge drum to temperatures materially below that corresponding tosaid chosen pressure on the basis of the thermo-dynamic properties of said refrigerant; means for causing vaporous refrigerant, together with water vapor and non-condensable gases when present, to iiow from said condenser to said drum; means responsive to the presence densed in the purge drum.

10. The combination of a refrigerative circuit containing a volatile refrigerant and including a condenser; a purge drum; a pressure operated vent valve controlling purging flow from said drum and arranged to open when pressure in the drum exceeds a chosen pressure; refrigerating means for cooling gaseous media in said purge drum to temperatures materially below vthat corresponding to said chosen pressure on the basis of the thermo-dynamic properties of said refrigerant; means for causing vaporous refrigerant, together with water vapor and. noncondensable gases when present, to flow from said condenser to said drum; means responsive to the presence of non-condensable gases in said circuit to control the last named means; means for separating condensed Water from condensed refrigerant and withdrawing them separately from said drum, lubricating oil when present from any source iiowing from said separating meanswith the condensed refrigerant,- and means for returning such condensed'refrigerant to said circuit, said means including an evaporative separatorI in which the refrigerant is evaporated and the trapped. s

'11.' 'I'he combination of a refrigerative circuit containing a volatile refrigerant and including a condenser; an air-concentrating chamber in free communication with the condenser; means for cooling said chamber to a temperature lower than' condensing temperature whereby a tendency toward concentration of non-condensable gases in said chamber is created; a ,purge device of the reirigerative separator type; and means responsive to the presence of air in the condenser for connecting said air concentrating chamber to said purge device.

12. The combination of arefrigerative circuit containing a volatile refrigerant and including a condenser; a chamber having connections affording free entrance of gases and vapors from the condenser and free drainage of liquid back to thecondenser; means for cooling the interior of said chamber to a temperature substantially below condensing temperature; purging means arranged yto draw vapors and gases from said condenser and simultaneously to draw them from said chamber at a restricted rate; and a thermostatic controller for said purging means subject to temperature of vaporous and gaseous media in said chamber.

13. The combination of a refrigerative circuit containing a volatilevrefrigerant and including a condenser; a purge drum: means forming a re` stricted communication between the condenser and the purge drum; a pressure responsive purge valve controlling flow from said drum and ar,- ranged to open at a purge drum pressure lower than condenser pressure; a cooling coil in said drum and operated at a temperature which for the refrigerant in the-circuit is decidedly lower than that4 corresponding to the pressure at which the purge valve opens, said coil having condensing capacity at least sufficient to condense all the refrigerant that can flow to the purge drum through said restricted communication, a valve controlling. said restricted communication; and means sensitive to the presence of non-condensable gases in said circuit connected to said valve to actuate the same and arranged to opensaid valve when non-condensible gases are present in substantial quantity and close it at other times.

WILLIAM E. ZIEBER.

oil so freed from refrigerant is

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