US1525006A - Method of purging refrigerating systems - Google Patents

Description

Feb. 3, 1925. 15253306.

T. SHIPLEY METHOD OF PURGING REFRIGERATIN": SYSTEMS Filed Feb. 6, 1924 gnoenfoz ?atented Feb. 3, i925.

TATES' THOMAS SHIPLEY, OF YORK, PENNSYLVANIA.

METHOD OF PURGING REFRIGERATING- SYSTEMS.

Application filed February 6, 1924. Serial No. 691,057.

To all whmit it may concern:

Be it known that I, THoMAs SHIPLEY, a citizen of the United States, residing at York, in the county of York and State of Pennsylvania, have invented certain new and useful Improvements in Methods of Purging Refrigerating Systems, of which the following .is a specification.

This invention relates to a method of removing foreign gases from the refrigerant in various types" of refrigerating systems. By the term refrigerating system, I mean to include various types of apparatus for performing a cooling or refrigerating function by the use of a volatile refrigerant which circulates in a closed path, and which is liquefied in one part of its path by the application of pressure and the abstraction of heat, and which is evaporated in another part of the circuit to abstract heat from some surrounding medium.

Such systems are of various known types audit is a fact well known to those familiar with their operation that there is a tendency for foreign gases to enter into and accumulatein the system with a consequent reduction of efficiency. These so-called foreign gases are commonly air, and gases or vaporsresulting from the effects of heat on the lubricating oil used in the compressors forming part of mechanical compressor systems. V

The foreign gases have tended to, accumulate chiefly in the condenser, which is commonly the highest part of the system, and

it has been the generally accepted view that these foreign gases are lighter than the refrigerant gas. Hence, it has been the usual practice and indeed the almost universal practice to discharge the foreign gases from the system by a so-called purging operation carried out at the top of the condenser. There are various modes of purging which differ in detail, but are fundamentally identical. Speaking generally, it may be said that all these methods are characterized by the discharge to the atmosphere from the top of the condenser, or from the tops of the several condenser units seriatim, of the foreign gases together with more or less of the gaseous refrigerant.

The present invention is based on the discovery that the foreign gases which tend only prevented from reaching a lower level v by liquid seals consisting of liquid refrigerant in the lower portions of the coils or in the discharge header or connections of the condenser.

The present invention contemplates the removal of foreign gases from condensers by so constructing, or so operating, the condenser as to prevent the existence of a liquid seal at its bottom, so that the foreign gases are premitted to discharge with the liquid refrigerant from the bottom ofthe condenser, and are thereafter trapped and separated .from the liquid refrigerant by means of a liquid seal and thus prevented from passing to the liquid ammonia receiver. For this reason the foreign gases accumulate in that part of the system between the condenser and the liquid receiver and here a suitable volume is provided to receive them. By their accumulation here they do no substantial harm, since they neither reduce the effective surface of the condenser nor obstruct the flow of liquid refrigerant therefrom.

When the foreign gases have accumulated in sufficient quantity to require the operation, they are discharged from the system by cutting this part of the system out of communication with the rest and then venting its contained gases to atmosphere.

This operation may involve the discharge to the atmosphere of a certain amount of refrigerant gas mixed with the foreign gases, but thisloss can be virtually eliminated. To do so it is only necessary to chill the'gases in that portion of the system until the refrigerant is liquefied. This can be almost completely eflected at a temperature at which the foreign gases maintain their gaseous condition. The liquid refrigerant may then be drained away andreturned to the system before the foreign gases are vented. In this way, substantially all the refrigerant is saved.

A slightly less refined mode of operation is to chill the refrigerant to a temperature decidedly below that corresponding to its pressure, and then vent the foreign gases without draining away the liquid refrigerant. Under such conditions, the foreign 1, the inlet or gas header at 2, the outlet oring drawing.

A portion of the condenser is shown at liquid header at 3', and a thermometer in serted iii a thermometer well in the liquid v header at 4. This condenser is shown as of the familiar atmospheric type and ordinarily would be provided with the usual water cooling sprays, not shown. The type of condenser is immaterial so long as it is so constructed or so operated that the liquid refrigerant does not form a liquid trap. or

' seal either in the lower coils of the condenser or in the liquid header 3.

, As explained, such a trap or seal confines the foreign gases to the condenser by preventing their escape therefrom in substantial quantity, and therefore causes, in the conventional type of system, the accumulation of foreign gases in .the condenser and particularly in the upper'portion thereof.

The liquid refrigerant line 5 leads downward through a branch 6 controlled by a valve 7 to the so-called purge drum 8, the connection entering the top of the drum.

'The outlet connection 9 from the bottom of the drum 8 is-provided with a valve 10 and leads byway of the pipe 11 to the gravity oil trap 12.

A by-pass 13 controlled by a valve. 14

serves to establish a connection between the pipe 5 and the pipe 11. Normally the valve 14 1s closed and the valves 7 and 10 are open so that liquid ammonia passing from the condenser 1 flows through the purge drum 8, and thence by way of the pipe ll to the oil trap 12. When the purge drum is to be freed of foreign gases, valves 7 and 10 are closed to cut the drum 8 off from the system and the valve 14 is opened'to establish a by-pass. connection through which thea plant is kept in'operation during the venting of the purge drum.

The oil trap 12 is of familiar form and is providedwith a gauge glass 15 to permit the operator to observe the level of oil in the trap.- The oil may be drawn off from time to time through the valve connection '16. The top of the tra 12 is connected by a pipe 17, controlled y a valve 18 with the called condensate indicator drum 34.

. memos liquid refrigerant receiver 19. The discharge of ammonia from the receiver 19 to 'the expansion coils, or other apparatus, is controlled by the valve 20. The valved connection 21 is a charging connection through which the system may be charged with refrigerant.

An equalizing pipe 22 is connected through a valve 23 with the top of the trap 12. and through a valve 24 with the socalled equalizing header 25. The header 25 is connected through valves 26 with the various coils making up the condenser (only one coil is visible in the drawing). The valve 27- offers means by which the condenser coils may be purged from the top, as is now the practice, in the event that it should everbe desired to perform this oper-v T he equalizing pipe 22 and header 25 thusserve to equalize the gas pressure at the top of the condenser with the gas pressure at the top of the oil trap so that the oil and liquidammonia may never be forced out of the trap and so that the trap 'will always serve to form a liquid seal controlling the discharge from the purge drum 8.

The apparatus so far described can be used for carrying out my process in its simplest form, provided the purge drum be provided with a normally closed valve controlled vent. The operation is simply to close the valves 7 and 10 and open the valve 14 to permit the plant to continue in operation,-after which the drum 8 is vented to theatmosphere. This discharges a mixture of. ammonia and foreign gases but is quite an effective method because theforeign gases in the system tend to accumulate in the drum. The loss of refrigerant gas is, however,- unnecessary and my method is capable of being practiced in more refined Ways which prevent this loss.

The drum 8 is provided with apressure gauge 28'. and may, if desired, also be equipped with. a thermometer and well 29. An expansion valve 30 is connected to receive liquid refrigerant from the receiver 19 (this connection is not shown in the drawing). The expansion valve 30 allows the liquid refrigerant to expand into a coil 31 housed within the purge drum 8.

The-discharge 32 from the coil 31 is'con-. nected to the suction or low pressure line,

hence the coil 31 acts as a refrigerating coil to chill the mixture of gases in the drum 8. Its effect is to liquefy the ammonia gas while leaving ,the foreign gases in their gaseous condition.

A valve 33. controls a passage to a so- This has a gauge glass 35 which permits the op- ,erator'to. determine the level of the liquid the purge drum to the system.

The purge drum 8 is connected by an equalizing pipe 37' controlled by a valve 38, with the top of the indicator drum 34; pipe 37 serving as apressure equalizing connection to permit the free flow of liquid ammonia from the drum 8 to-the drum 34, when the valves 33' and 38 are open; The valve 39 controls a vent or'purge connection for both the drums 8 and 34.

When the engineer notes that the thermometer 4 on the liquid header 3 indicates a temperature lower than that correspond ing to the pressure shown by" the high pressure gauge on the system, he knows that" foreign gasesare present. To remove such gases, he performs one or more purging operations on the drum 8.

The normal condition of the apparatus is as follows: valve 14 closed; valves 7 and 10 open; expansion valve closed; vent valve 39 closed; liquid ammonia .controlling valve 33 closed; equalizing valve 38 30- closed; and liquid ammonia return valve 36 closed. I

Each purging operation preferably consists of the following steps: valve 14 is opened and valves 7 and 10 are closed. This cuts the drum 8 out of the system and af-.

fords a bypass around it. Expansion valve 30 is then opened to permit. refrigerant to expand into the coil 31 and immediately thereafter the liquid ammonia control valve 33 and equalizing valve 38 are opened to drain liquefied ammonia from the drum 8 into the condensate indicator drum 34.

The desired liquefaction of the ammonia gas is indicated in two ways. During the chilling operation the gauge 28 will short a fall of pressure which will cease when such li uefaction of the refrigerant has occurre This condition will also be indicated by constant level of the liquefied" ammonia in gauge glass 35.

When liquefaction is accomplished, the operator. closes the valves 33 and 38 and opens the valve 36, permitting the liquid ammonia to flowto the low pressureline or suction line of the system thus recov When all the valve 36 is closed.

The .refrigerant now having beenlique fied and recovered, expansion valve 30 is closed and valve 39 is opened to vent the purge drum 8.- 4 Upon the completion of the venting, the

valve 39 is closed, valves 7 and 10 are then opened,'and valve 14 closed. In this way the purge drum 8 is restored as a part of the circulating system and commences once more to perform its function'of acc-umulating foreign gases flowing from the condenser.

As suggested, a reasonably satisfactory discharge of the foreign gases without discharge of any substantial quantity of refrigerant can be had merely by lique'fying.

charge the foreign -gases. When the drum 8 is .restored' to the system, the liquid refrigerant passes on to the receiver. While I prefer to remove the liquid refrigerant from the purge drum before venting it. I wish expressly to state that the simplest mode of operation falls within the broad scope of my invention.

While I contemplate the progressive ac cumulation of foreign gases in the drum 8, it is not strictly necessary that the flow of foreign gases from the condenser 1 be continuous. It might, for example in a condenser having small pipe sections, or a small liquid header. be more or less intermittent. In such a case, if the periods of downward How of the gas were frequent enough, and sufliciently sustained to keep the condenser 1 relatively free of foreign gases, the method -formin the subject-matter of the present application would be present. 4

An important feature of the invention is that a system operating according to this method functions to produce a continuous or substantially continuous discharge of foreign gases from the condenser and their simultaneous accumulation in a part of the system where their presence does not retard the useful heat transfer and therefore exerts a minimum harmful effect on the efiiciency of the system as a whole. Furthermore; the accumulation of these gases by gravity flow, aided by the general flow of the refrigerant, and their retention by a positively maintained liquid seal, leads to the efiective localization of the foreign gases. with a consequently highly effective purging action, and 'this'without the loss of any substantial quantity of refrigerant.

Obviously, the method ma be carried out without employing the specific apparatus described and no limitation to such apparatus is implied.

What is claimed is: 1. The method of removing foreign gas from a refrigerating system including a is frigerant from the bottom of the condenser condenser and a receiver which consists in withdrawing such gas with more or less refrigerant from the bottom of. the condenser by gravity flow, forming a trap seal capable of passing liquid refrigerant, and by it causing progressive accumulation of gas in a part of the system below the level of the condenser and in advance of the receiver, while permitting passage of liquid refrigerant to the receiver; and discharging said accumulated foreign gas.

2. The methodof removing foreign gas from a refrigeratinglsystemincluding a condenser and a receiver, which consists in withdrawing such gas with more or lessredenser by gravity flow forming a trap seal capable of passing liquid refrigerant, and

, gas.

by it causing progressive accumulation of gas in a part of the system below the level of the condenser, while permitting passage of liquid refrigerant to the receiver; isolating said accumulated gas from the system;

chilling said gas to liquefyrefrigerant gas present; and then discharging the foreign 4:. The method of removing foreign gas from a refrigerating system including a2 condenser and a receiver, which c'onsists'in withdrawing suchrgas with more or less refrigerant from the bottom of the con denser by gravity flow, forming a trap seal capable of passing liquid refrigerant, and by it causing progressiveaccumulation of gas ina part of the system below the level of the condenser, while permitting passage of liquid refrigerant-to the receiver; isolat-= ing said accumulated gas from the system;

chilling said isolated gas toliquefy refrigerant vgas present, withdrawing said liquefied.

essence refrigerant; and then discharging said forgas.

5. The methodof purging the condensers of refrigerating systems. which consists in substantially continuously withdrawing liquid refrigerant and such refrigerant gas and foreign gas as may be present together from the bottom of the condenser by sim ple gravity flow, forming a trap seal of liquefied refrigerant at a substantial dis-.

tance below the'bottom of the condenser,

and by it causing the progressive accumulation of foreign gas below the condenser while permitting the flow of liquid refrigerant, and at intervals isolating said accumulated gas from the system and discharging it.

6. The method of purgin of refrigerating systems w ich consists in substantially continuously withdrawing liq-- uid refrigerant and such refrigerant gas and foreign gas as may be present together from the bottom of the condenser by simple gravity flow, forming a trap seal of liquefied refrigerant at a substantial distance below the bottom of the condenser, and by it causing the progressive accumulat-he condensers tion of foreign, gas below the condenser while permitting the flow of liquid refrigerant, and at intervals isolating said accumuv lated gas front the system; chilling it to liquefied gaseous refrigerant present; and then discharging the foreign gas.

7. The method of purging the condensers of refrigerating systems which consists in substantially continuously withdrawing liquid refrigerant and such refrigerant gas and foreign gas as may be present together from the bottom of the condenser by sim- I ple gravity flow, forming atrap seal of liquefied refrigerant at a substantial distance below the bottom of the condenser,

tion of foreign as below the condenser while permitting te flow of liquid refrigerant, and at intervals isolating said accumulated gas from the system, chilling it .to' liquefy gaseous refrigerants present, with and by it causing the progressive accum'ula drawing such'liquefied refrigerant,jand then discharging said foreign gas.

In test-imonv whereof I have signed by f i name to this specification. 3 v a SHIPLEY.

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