US2655008A - Liquid refrigerant transfer in refrigeration system - Google Patents

Description

Um., h3, 1953 H. sLoAN ET AL 29655900@ LIQUID REFRIGERANT TRANSFER IN REFRIGERATION SYSTEM Filed April 11, 1949 Patented Oct. 13, 1953 UNITED STATES PATENT OFFICE LIQUID REFRIGERANT TRANSFER IN REFRIGERATION SYSTEM of Wisconsin Application April 11, 1949, Serial No. 86,782

3 Claims. l

Our invention relates generally to improvements in the art of refrigeration, and relates more specically to an improved liquid refrigerant transfer system for refrigeration plants or similar installations.

The primary object of the present invention is to provide an improved system of transferring liquid refrigerant from the low pressure accumulator to the high pressure receiver of a refrigeration plant.

It has long been customary to install large drums in the main suction lines of the larger refrigerating plants for the purpose of separating the liquid refrigerant from the vapor in order to prevent liquid slugs from entering the compressors and thus causing severe damage such as breakage of heads, cracked frames, or injury to the operators. In many of these prior installations the safety drums were equipped with banls of coils through which the liquid refrigerant delivered to the various evaporators, was cooled and the liquid which was separated from the vapor was subsequently evaporated and passed on to the compressor. This mode of handling the separated liquid is not satisfactory because at times the liquid level builds up sufficiently to cause liquid to overflow and enter the compressor, and this action takes place whenever the amount of liquid returning with the suction vapor exceeds the amount required to cool the liquid flowing through the coils.

Some of the prior separator drums have also been equipped with lioat switches adapted to operate alarm bells or the like, when the liquid level reached a dangerous height. The operator Was then obligated to manually reduce the quantity of liquid refrigerant delivered to the various evaporators thus disarranging and disturbing the entire installation. Other prior safety systems were equipped with pumps or ejectors which would start Whenever the alarm operated, and would continue to function until the liquid level had dropped sufliciently. Some of these previous safety drums were provided with float actuated switches which would automatically start a pump whenever the liquid in the drum attained a predetermined high level and would likewise stop the pump at a definite low level, but with this system it Was necessary for the pump to discharge liquid into a high pressure receiver under severe operating conditions when the suction pressure was low, and gas locks were frequent when handling highly volatile liquid.

All of the prior liquid refrigerant return systems were therefore objectionable and unsatisfactory for one reason or another, and it is an object of our present invention to provide a simplied and more reliable mode of automatically performing this particular duty.

Another important object of our invention is to provide an improved system for automatically returning liquid refrigerant from the suction to the high pressure lines of a refrigerating plant with the aid of relatively small drums or Vessels adapted to maintain a maximum quantity of refrigerant in actual use.

A further important object of this invention is to provide an improved refrigeration installation in which the condenser pressure is lowered to a minimum, and wherein any entrained air and other noncondensible gas which tends to accumulate in the condenser and receiver, will be kept in circulation, by merely taking the operating pressure for evacuating the refrigerant storage drum from the uppermost portion of the receiver.

Still another object of the invention is to provide an improved refrigeration system wherein the liquid refrigerant returned from the suction line to the receiver Will always be at a temperature corresponding to the suction vapor pressure, and will therefore sub-cool the liquid in the receiver to a degree depending on the quantity of liquid returning through the suction line, so that the sub-cooled liquid will ow to the several evaporators in the form of solid columns up to the expansion valves and will thus present formation of troublesome vapor in the liquid conducting pipes and connections.

An additional general object of our invention is to provide an improved mode of improving the efficiency of the evaporators of a refrigeration plant by reducing to a minimum the quantity of flash gas in the cooling coils, and by insuring most effective circulation of the cooling medium.

These and other objects and advantages of the invention will be apparent from the following detailed description of a typical refrigeration installation.

A clear conception of the features constituting the present improvement and of the mode of constructing and operating a typical refrigeration plant embodying the same, may be had by referring to the drawings accompanying and forming a part of this specification wherein like reference characters designate the same or similar parts in the various views.

Fig. 1 is a diagram of one typical refrigeration plant embodying our improved liquid refrigerant transfer system;

Fig. 2 is a wiring diagram showing the electrical apparatus and connections involved in the system of Fig. 1, in transfer cycle starting position; and

Fig. 3 is a similar diagram showing the electrical apparatus in action as when refrigerant is being transferred.

While the invention has been illustrated and described herein as being advantageously applicable to a system wherein the various control switches are float actuated and in which electrically operated valves are utilized, it is not our desire or intention to thereby unnecessarily restrict the scope or utility of the improvement; and it is also contemplated that descriptive terms employed herein be given the broadest possible interpretation consistent with the disclosure.

Referring to Figs. l and 2 of the drawings, the improved refrigeration plant illustrated diagrammatically therein, comprises in ,general a main compressor 4 having a suction line 5 provided with hand valves 5 and a discharge line 6 provided with hand valves 5 and a check valve 1'; a condenser 'I communicating at its upper portion with the compressor discharge line 6 and having a liquid refrigerant delivery pipe 8 at its lower portion provided with a hand valve 8; a main horizontal `high pressure liquid receiver 9 communicating at one end with the condenser delivery pipe 8 and having a liquid refrigerant discharge pipe Il) provided with a hand valve 9', a charging valve I andan expansion valve I I and extending into `the lowerm-ost portion of the opposite end of the receiver 9; one or more cooling coils or evaporators II communicating at their lower inlet ends with the supply pipe past the expansion valve -IIl and having their upper ends provided with an outlet pipe I2.; an upright suction line accumulator I3 communicating at its upper end with the pipe I2 and with the compressor suction -line 5, and having its lower portion provided with an oil Adrainage valve I3 and located considerably below the receiver .9 and also provided with a liquid refrigerant delivery 4pipe 14; a-n `ini-tial horizontal liquid refrigerant transfer container or ldrum I located well below the receiver 9 and having the uppermost port-ion of one end thereof in comm-unication with the accumulator loutlet pipe vI4 while its lowermost lopposite end has a liquid refrigerantdischarge pipe I6 provided with a flow control hand valve I6', land extending upwardly therefrom; a iinal horizontal liquid refrigerant transfer container or drum -I l located l:above the receiver 9 and lhaving its Vupper por-tion connected to the pipe I6 while its lowermost portion has a liquid refrigerant delivery pipe I8 communicating with the top mid-portion of the receiver 9,; and a plurality of additional valves and auxiliary pipe connections for insuring .automatic functioning of the installation.

The compressor 4, condenser V'I, high pressure receiver 9, evaporator II, and accumulator I3, are all of usual and well-known construction, but the initial transfer container or drum I5 and its location with respect to the container or drum 'I 'I and receiver B -constitute an important feature of our invention. There may also be any desired number of evaporators I -I provided, all connected to the usual inlet anddischarge headers I9, 26 respectively with which the ypipes HJ, I2 communicate, and the various pipes and -connections of ythe installa-tion are preferably lpro- 4 vided with shut-off and check valves as hereinbefore indicated for permitting various parts to be inspected or removed without necessarily disrupting the entire installation.

In order to utilize the two transfer containers or drums I5, I'I so as to automatically return liquid refrigerant from the suction line accumulator I3 to the high pressure liquid receiver 9 without endangering the compressor 4 and also without utilizing special auxiliary pumps or ejectors, we have provided a special system of float actuated valves cooperating with a number of electrically actuated valves and an alarm, and which valve system is shown in Figs. 1, 2 and 3. A high level oat actuated switch 22 located in the upper portion of the suction line accumulator I3 is adapted to open upon drop in liquid level and to close upon rise in level, and to :sound an electric bell 23 or other alarm energized from a main electric current supply line 24 whenever the liquid level rises to a dangerous height in the accumulator I3. The initial lowf er liquid refrigerant transfer drum I5 is provided with a high level float actuated yswitch, 25

: and with a low level float actuated switch 26 both of which close to complete an electric circuit energized from the main line 24 when the level of the liquid within the initial transfer drum I5 rises predetermined amounts .and open to interrupt the circuit when the liquid level drops. While thesel switches 25, 26 both respond to variations in the liquid level in the drum I5, they are set at different levels and operate independently in order to obtain the necessary wide liquid level differential. When the liquid level is at the bottom of the drum I5 both of these switches 25, 26 are open, and as .the liquid level rises the lower switch 26 will close but the upper switch 25 will remain open until the liquid level reaches .the top of the drum. When the liquid level drops, the upper switch 25 will open but the lower switch 2-6 will remain 4closed until the liquid level has dropped lsufficiently to open it.

The liquid refrigerant delivery pipe I4 leading from the accumulator I3 into one end vof the drum I5 has an automatic magnetically actuated flow control valve 2.1 therein, and the refrigerant Idischarge pipe I6 leading from the bottom of the lower drum vI5 into the top of the upper drum I'I has a similar magnetically actuated ow control valve 28 therein besides the hand operated regulating valve I6,. Thedelivery pipe I8 which connects the bottom of the upper drum I1 with the top of the receiver .5, also has a magnetically actuated flow control valve v25 therein. A pressure transfer pipe 30 is also provided between the upper portion of the lower drum I5 .and the top of lthe high pressure receiver l9, Iand this pipe 30 is .provided with another magnetically actuated valve 3-I. The portion of the pipe 30 on the drum side of the valve 3I is connected to the suction accumulator I3 by means of another pipe 32 having still another magnetically actuated valve 33 therein; and the portion of the pipe 32 between the accumulator I3 and the valve 3-3 is connected t0 the high pressure receiver 9 by still another pipe 34 having a branch 35 leading into the top of the upper drum I1. A magnetically actuated valve 36 is also provided in the pipe 34 on the accumulator side of the branch 35, and a similar magnetically actuated valve .31 is also provided in the ypipe 34 on Vthe receiver side .of the branch 35, thus completing the special automatic valve system.

All of the magnetic or solenoid valves 21, 28, 29, 3|, 33, 3B, 3`| may be of similar construction and are periodically opened and closed by means of a two-pole double-throw magnetic relay 38 cooperating with a pair of single-pole timing devices 39, 49 shown in the wiring diagrams of Figs. 2 and 3. The relay 38 has two normally open contacts and one or more normally closed contacts, and as illustrated in the diagram, the upper contact is normally open but is adapted to actuate the valves 28, 3 I, 3B through the timer 49. The next lower contact is also normally open and provides a holding contact for the float switches 22, 25, 23, while the next lower contact is normally closed and actuates the valves 2l. 29, 33, 37| through the timer 39. The timer 39 has normally open contacts, but when the liquid level in the drum I5 drops and the switch 26 opens, the relay 38 is de-energized thereby closing the contacts which are adapted to energize the valves 33, 3l and starting the timer 39 which after the preset period closes so as to energize the valves 2l, 29, and the timer 39 automatically resets when de-energized. The timer 4U also has normally open contacts, but when the liquid level in the drum I5 rises and the switch 25 closes, the relay 38 is energized thereby closing the contacts which are adapted to energize the valves 3|, 36 and starting the timer 49 which after the preset period closes sov as to energize the valves 28, and this timer 49 likewise automatically resets when de-energized. The remaining contacts of the relay 38 provide a holding circuit Which prevents the relay from cle-energizing until the liquid level has dropped to open the valve 26. The purpose of utilizing these timers 39, 49 in order to delay the opening of the valves, is to allow the pressures in the drums I5, I'I to equalize so that the valves are not required to open against abnormal pressure differences thereby making maximum power available to quickly open these valves against friction produced by congealed oil, and the pressure equalization furthermore prevents liquid surges and resultant hydraulic hammer due to great pressure difference. Both groups of magnetically actuated valves are however energized from the main line 24, and the normal operation of the improved system is as follows:

As a cycle starting point, assume the level of the liquid refrigerant within the lower container or drum I5 to be near the bottom thereof, at which time both the high level switch 25 and the low level switch 26 are open and the timer 39 is inactive. The magnetic valves 33, 27, 3l, 29 are energized and open at such time and the magnetic valves 3|, 36, 28 are deenergized and closed, while electric current is passing through the circuit shown in heavy solid lines in Fig. 2. With the system in this condition, liquid refrigerant from the suction accumulator is free to drain by gravity into the lower drum I5.

As the liquid level in the drum I5 rises, the lower level switch 26 closes but nothing actually transpires in the system until the liquid level has continued to rise suiciently to also close the switch 25, whereupon the coil of the relay 38 is energized and causes the movable contacts of this relay to assume the positions shown in Fig. 3. When this happens the magnetic valves 33, 2l, 3T, 29 are deenergized and closed, while the magnetic valves 3 I, 36 are energized and open immediately but the magnetic valve 28 opens only under the influence of the timer 49 which has been preset so as to prevent opening of the valve 28 until after the pressure in the drum I'| has been reduced through the open valve 36 and high pressure uid is being admitted to the drum I5 past the open valve 3|. With the valve 28 thus open liquid refrigerant is forced by the high pressure vapor flowing from the receiver 9 into the drum I5 past the open valve 3|, into the drum Il through the conduit I6.

As the liquid level in the drum I5 drops, the high level switch 25 opens but nothing occurs within the system until the liquid level in the drum I5 has continued to drop sufficiently to also open the low level switch 26, whereupon the coil of the relay 38 is deenergized and the electric circuit reverts to the condition shown in Fig. 2. When this action occurs the magnetic valves 33, 31 open immediately, but the magnetic valves 2'|, 29 will open only under the influence of the timer 39 which has been preset so as to prevent opening of the valves 2l, 29 until after the pressure in the upper drum II has equalized with that in the receiver 9 through the open valve 3l and the pressure in the lower drum I5 has also equalized with that in the accumulator |3 past the open valve 33. During this period of operation the magnetic valves 3|, 3S, 23 close immediately prior to the opening of the valves 2l, 29, thus preparing the system for subsequent automatic repetition of the cycle.

The improved liquid refrigerant transfer system thus functions to automatically and eifectively transfer the liquid cooling medium from the separator and/or accumulator to the high pressure receiver, Without the use of pumps or ejectors, and without in any manner endangering the compressor or the operators. This automatic transfer of the liquid refrigerant is effected solely by gravity and/or the high pressure within the main receiver, and is controlled primarily by the oat switches of the system. The alarm which is actuated by one of the float switches functions only under abnormal conditions of operation of the installation, and the refrigerant receptacles may be of relatively small capacity in order to maintain most of the liquid refrigerant in circulation whenever the plant is operating normally.

From the foregoing detailed description of the construction and operation of our improvement, it should be apparent that We have in fact provided a simple yet highly ecient liquid refrigerant transfer system which functions automatically to maintain effective circulation of the cooling medium without permitting liquid to reach the compressor inlet. The improved system maintains all air and other non-condensible gas in constant circulation thus reducing the condenser pressure to a minimum, and since the liquid refrigerant returned from the suction accumulator to the high pressure receiver has a temperature corresponding to the suction vapor pressure, it will tend to sub-cool the liquid in the receiver to a degree depending upon the quantity of liquid returning through the suction line. This sub-cooled liquid flowing to the evaporators insures the formation of a solid column or stream passing through the conduits and pipes leading up to the expansion valve IIJ', thus preventing formation of annoying vapor, and also increasing the efficiency of the evaporators by reducing the quantity of fiash gas therein.

It should be understood that it is not our desire :to limit this invention to the exact details of construction, or to the precise mode of operation of the electrically actuated liquid refrigerant transfer system herein shown and described, for various modifications Within the .scope of the appended claims may occur to persons skilled in the refrigeration art.

We claim:

l, In a refrigerating system including the con- #ventional compressor having a suction line for returning evaporated refrigerant to the compressor fand having a high pressure refrigerant line, an accumulator drum interposed in the suction line ifor collecting liquid refrigerant to prevent delivery of the same to the compressor, a liquid trap :located below the accumulator drum and having connection with the drum for receiving liquid refrigerant therefrom by gravity now, a second liquid trap having an elevated position with respect to the first mentioned trap, conduit means l.joining said traps, means supplying high pressure gaseous refrigerant from said high pressure refrigerant line to the first mentioned trap to ef- ,ffectv a flow of the liquid refrigerant therein through said conduit means to the second trap, a connection from the second trap to the high pressure refrigerant line, and other means supplying high pressure gaseous refrigerant from said line \to the second trap to effect flow of the liquid refrigerant in the second trap through said connection to the high pressure side of the system.

2. In a refrigerating system, in combination, a suction line for delivering evaporated refrigerant to the compressor of the system, a high pressure refrigerant line connecting with the discharge side of the compressor, a container adapted to receive liquid refrigerant from the suction line, a second container having an elevated position with respect to the rstmentioned container, conduit means joining said containers, means supplying high pressure gaseous refrigerant from said high pressure refrigerant line to the first mentioned container to effect avflow of the liquid refrigerant through said conduit means to the second container, said means having op;- eration to vent the said first mentioned container to the suction line during the period when the supply of said gaseous refrigerant is stopped, a connection from the second container to the high pressure refrigerant line, other means supplying high pressure gaseous refrigerant from said line to the second container to effect flow of the liquid refrigerant through said connection to the high pressure side of the system, and said other means having operation to vent the second container to the suction line during the period when the supply of gaseous refrigerant is stopped,

3. In a refrigerating system including the conventional compressor having a suction line for returning evaporated refrigerant to the compressor and having a high pressure refrigerant line, an accumulator in the suction line for collecting liquid refrigerant to prevent delivery of the same to the compressor, conduit means providing a passageway connecting the accumulator with a receiver in the high pressure refrigerant line, said conduit means including first and second valved containers with the second container having a position above the first container, and means supplying high pressure gaseous refrigerant from said high pressure refrigerant line to the con-y tainers in an intermittent and alternate manner, whereby to pump the liquid refrigerant in ythe rst container to the second container and then from the second container to the receiver.

HARRY SLOAN. ERICH J. KOCHER.

References Cited in the le of this patent UNITED STATES PATENTS Number N ame Date 1,050,894 Williams et al Jan. 21, 1913 V1,106,244 Schliemann Aug. 4, 1914 1,106,287 Doelling Aug. 4, 1914 I1,718,312 Shipley June 25, 1929 1,720,171 Davison July 9, 1929 l2,032,286 Kitzmillr Feb. 25, 1936

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