US2168157A - Fluid cooling system - Google Patents

Description

mim cooLI-NG SYSTEM Filed Dec. 23, 1957 H. R. CRAG K 2,168,157

svsheetsrsneet 1 I hveto. Y Y Harry Crago,

' His AttoYT-gey.

H. R. CRAGO FLUID COOLINGA SYSTEM Fi'l edADec. 23, 1937 3 Sheets-Sheet 2 Figi..

. IhveY-VGOY:

` Harry R. C ago by VW $MMW` a l-Hs Attorney.

Aug. 1, 19.39. H; R. cRAGo 2,153,157

FLUID COOLING sYsTEu Fiied Deb. 25. 19:57 'f 3 sheets-sheet 3 Fig. 3.

Inventor:

H R. by #gez/lge Att oT- h ey.

Patented Aug. 1, 1939 PATENT OFFICE 2,1es,1 57 FLUm comme SYSTEM Harry R. Crago, Verona,

eral Electric Company,

York

N. J., assignor to Gena corporation of New Application December 23, 1937, Serial No. 181,274

11 Claims.

l to'carry the load need be connected to operate.

In such systems, each machine may be operated more nearly within its most eiiicient rangel of load. Accordingly, it is an object of my invention to provide a fluid cooling system having a plurality of refrigerating machines and including an improved arrangement for controlling the sequence of operation of the refrigerating machines.

Another object of my invention is to provide a fluid cooling system having a plurality of refrigerating machines and an improved arrangement for selecting the machines for operation in accordance with the load on the system.

Further objects and advantages of my inven- -tion will become apparent as the following description proceeds, and the features of novelty which characterize my invention will'be pointed out with particularity in the claims annexed to and forming' a part of this specification.

' For a better understanding of my invention, reference may be had to the accompanying drawings in which Fig. 1 is a diagrammatic illustration of an air cooling system including a refrigerating machine having two condensing units and embodying my invention; Fig. 2 is a diagrammatic illustration of an air cooling system utilizing two refrigerating machines embodying my invention; and Fig. 3 is a diagrammatic illustration of a modified arrangement of an air cooling system similar to that shown in Fig. 2.

Referring now to the drawings, in Fig. 1 I have shown an air cooling system including a duct I having a fresh air inlet and a return air inlet |2 provided with nlters I3 and I4 respectively. The fresh and re-circulated air enter the duct and are circulated therethrough by operation of a fan I5 driven by a motor I5, themixture of air being discharged into the room or other enclosure to be conditioned through an outlet In order to cool the air passing through the duct I0, I provide a refrigerating machine including evaporators I8 and I9 arranged in the duct I9 and connected in a closed refrigerant circuit including condensing units and 2| connected in parallel to supply liquid refrigerant to the evaporators I8 and I9 through aliquid line 22 and to withdraw gaseous refrigerant from the evaporators through asuction line 23. The condensing unit 2|! includes a compressor 24, acondenser 25, and aliquid receiver 26. 'I'he condenser is cooled by water circulated through a casing 21' surrounding the condenser and having a cooling water inlet and an outlet as indicated by the arrows. The condensing unit 2| comprises acompressor 28, a condenser 29, a liquid receiver and a water circulating casing 3| having a cooling Water inlet and an outlet as indicatedv by the arrows. Thecompressors 24 and 28 are driven bymotors 32 and 34 respectively. A'thermostat 35 arranged in the enclosure to be conditioned is tion of the cooling system. When there is a demand for cooling, one or both of themotors 32 and 34 are operated to compress refrigerant and discharge the compressed refrigerant into the corresponding one of thecondensers 25 and 29 where the refrigerant is cooled and liquefied by the circulation of Water thereover, the liquid refrigerant being collected in thereceivers 26 and 30. Liquid refrigerant 'flows through theliquid line 22 and is admitted to the evaporators I8 and I9 by operation ofthermostatic expansion valves 36 and 3l havingthermostatic elements 38 and 39 respectively connected to the outlet sides of the evaporators. The liquid refrigerant Within the evaporators I8 and I9 absorbs heat from the air circulating through the duct I0 and is vaporized, the vaporized refrigerant being withdrawn and returnedto the condensing units through thesuction line 23. The motor I6 is arranged to drive the fan I5 continuously.

The mixture of air passing through the duct I0 may'vary widely in temperature and relative humidity, and there is, therefore, a wide variation of the load which must be carried by the evaporators. Since each of the condensing units operates most eiliciently within a particular range of loads for which it is designed, it may be desirable to operate only one of the units when the load is relatively small and to operate both units only when full load is required. It will be evident that if, the condensing units are designed to carry different loads, it is possible to provide three dif.- ferent ranges of load at which the system may operate eiiiciently. For example, if thecondensing unit 20 is designed to carry a load of 10 H. P. and the condensing unit 2| a load of 20 H. P., it is `possible to operate the system with high efprovided to control the operaciency at loads of 10 H. P., 20 H. P., and 30 H. P.

,In order to operate the cooling system at maximum eiciency, I provide an arrangement for controlling the condensing units and for selecting the units for operation in accordance with the load demand of the system.

, In the arrangement -shown in Fig. 1, whenever there is a. demand for cooling, thethermostat 35 moves to the right and connects acoil 40 across the secondary of a transformer 4|, the primary of which is connected acrosssupply lines 42, and aswitch 43 is picked up. 'I'he` upper arm of theswitch 43 closes a holding circuit for thecoil 40 and the two lower arms connect leads 44 of the'motor and control circuit across thelines 42.Motor 32 ofcondensing unit 20 is thereby connected to be energized throughswitches 45 and 46 and a line 41. Acoil 48 is also connected across thelines 44 through aswitch 49. Theswitches 46 and 49 are operated bypressure elements 50 and 52 respectively, which are connected to be responsive to the pressure within thesuction line 23. Theswitches 46 'and 49 are pivotally mounted and are operatedbythe pressure elements 50 and 52 through overcenter springs 46a and 49a. respectively; the switch may, therefore, be set to open at a predetermined low pressure and remain open until-a predetermined higher pressure has been attained. Such pressure operated switches are'commonly employed to control refrigerating machines. Thecoil 48 is arranged to pick up an armature 53 of a snap operating mechanism 54 for actuating switch 45to connect themoto'r 34 across thelines 44 thorugh alead 55 and the lead 41. It is desirable, however, to preventthe operation of the condensing unit 2| which is driven by themotor 34 if thecondensing unit 20 can satisfactorily carry the load of the system and I, therefore, provide atime delay device 56 which may be a. dashpot or any other suitable arrangement for delaying the operation of theswitch 45 for a predetermined interval of time. If the operation of thecondensing unit 20 reduces the pressure within thesuction line 23 to a predeterminedV value, say 25pounds per square inch, before the mechanism 54 operates to actuate theswitch 45, the pressure element 52 'will open theswitch 49 thereby deenergizing theswitch 48 and preventing the actuation of theswitch 45. Should the continued operation of thecondensing unit 20 reduce the pressure within thesuction line 23 to a predetermined minimum, say 29 pounds per square inch, thepressure element 50 will operate to open theswitch 46 and stop themotor 32. Should the condensing unit'20 fail to reduce the pressure within thesuction line 23 sufficiently to open theswitch 49, or should the pressure within thesuction line 23 rise to a predetermined value, say 30 pounds per square inch, after theswitch 49 has been opened initially, the element 52 will close the switch 49.V At

. the end of the interval of time determined by thetime delapmechanism 56, the plunger 53 will be fully picked up and will actuate the switch mechanism 54 to snap theswitch 45 to its upper position `and connect themotor 34 to operate the condensing unit 2|. The mechanism 54.as illustrated, comprises a pivoted member 51 connected to theswitch 45 by an over-centerspring 58 to snap the switch between its two extreme positions, it being shown in. its lower position. Whenv the armature 53 is fully picked up, a finger 59 engages the member 51 and moves it upwardly so that the overcenter spring snaps the, switch to its upper position. When the armature 53 drops out, a nger 6| engages the member 51 and snaps theswitch 45 to its lower position. When theswitch 45 is in its upper position, aswitch 62 is connected in series in the circuit of themotor 32. Theswitch 62 is provided with a pressure responsive member 63 and an overcenter spring 62a which are arranged to open theswitch 62 whenever the pressure in theconduit 23 falls below some predetermined value, say 30 pounds per square inch. It is, therefore, evident that if the pressure within theconduit 23 is less than 30 pounds per square inch when the condensing unit 2| isconne'cted, the switch '62 will be opened thereby deenergizing themotor 32 and stopping the condensing unit 2|l. Under ,this condition of operation, the condensing unit 2| carries the entire load of the system. Should the pressure within theconduit 23 be greater than 30 pounds per square inch when the unit 2| is started, theswitch 62 will remain closed. After theswitch 62 has been opened by the pressure element 63, the overcenter spring 62a ysatisied, thethermostat 35 will move to the left to short-circuit thecoil 40 thereby causing theswitch 43 to drop out and disconnect the motors of the condensing units.

During the operation of the cooling system shown in Fig. 1, the motor and control circuits of the condensing units will be energized whenever there is a demand for cooling and the pressure elements 52 and '63 will operate to start and stop the condensingunits 20 and 2| in accordance with the load on the system as determined by the pressure of the gaseous refrigerant withdrawn from the evaporators I8 and I9. Operation of the system at maximum elliciency is thereby assured.

Referring again to the drawings, in Fig. 2 I have shown an air cooling system including a duct 64 having areturn air inlet 65 and lter.

the mixture of air is returned to the enclosure or room to be cooled through a duct 1|. In order to cool the air passing through the duct 64, I provide two refrigerating machines, one comprising an Aevaporator 12 and a condensingunit 13 and the other anevaporator 14 and a condensing unit 15. Theevaporators 12 and 141 are arranged in the duct 64 so that the air is circulated rst over theevaporator 12 and then over theevaporator 14 in series. The condensingunit 13 comprises acompressor 16 driven by amotor 11, acondenser 18 and a liquid receiver 19. Thecondenser 18 is cooled by water cir- V culated through a casing having an inlet and outlet for the water as indicated by the arrows.

`Refrigerant is supplied to theevaporator 12 through a liquid line 8| under control of athermostatic expansion valve 82 having athermostatic element 83 connected in heat exchange relation to the outlet of the evaporator. Gaseous refrigerant is withdrawn from the evaporator through asuction line 84. 'I'he condensing unit,- 15 is similar to the condensingunit 13 and com- `When there is a demand for'coollng, thethermostat 94 moves to the right and connects acoil 95 across the secondary of atransformer 96, the primary of which is connected across 4thesupply lines 91. This energizes thecoil 95 and picks up aswitch 98. The upper arm of the switch closes a holding circuit for thecoil 95 and the lower arm connects motor and control leads 99 to thesupply lines 91 thereby connecting themotors 11 and 86 across the supply lines to start the condensingunits 13 and 15. Themotor 11 is connected across thelines 99 through a line |00, andswitches 0| and |02, and themotor 86 is connected across thelines 99 through the line |00 and a switch |03. 'I'he switches |0l and |03 -are controlled by pressure responsive members 04 and |05 respectively responsive to the pressures in thesuction lines 84 and 9|, and arranged to operate the switches through overcenter springs |04a and |05a. 'I'hese switches comprise the standard type of back. pressure control employed on condensing units to stop the operation of the units when a predetermined minimum pressure has been attained.

If the refrigerating machines are of substantially equal capacity, theevaporator 12 will carry about 60 per cent of the load and theevaporator 14 which is operating in cooled ali` carries about 40 per cent of the load. It is readily apparent that under some conditions of load, one of the evaporators can satisfactorily handle the entire load of the system. It is, therefore, desirable to provide some arrangement for cutting out one of the condensing units in the event the load of the system is suihciently low to be carried by a single unit. In orderto accomplish this purpose, I provide a pressure responsive device |06 having an overcenter spring |06a for opening the switch |02 whenever the pressure within the suction line 9|, of the compressor 85 falls below a predetermined value. Opening of the switch |02 opens a circuit of themotor 11 and stops the operation of the condensingunit 13. The entire load then must be carried by theevaporator 14 connected to the condensing unit 15. In order to prevent the immediate reclosing of the switch |02 y when the additional. 10aa is added to the evap- 1 12 again be connected for Service.

unit 13, therefore, is arranged to be operated in ,if which issimilar to that shown in Fig. 2 andcororator 14, the device |06 is-arranged to reclose the switch at a pressure substantially higher than .that at which it operates to open the switch.

'I'he evaporator 14 may, therefore, carry the entire load, and only lf the load becomes greater than a predetermined value will the evaporator Condensing accordance with the load on the condensing unlt'16.

Should the demand for cooling be satisiled, thethermostat 94 will engage its left-hand contact and short-circuit thecoil 95 thereby causing theswitch 98 to drop out and disconnect the motors of the refrigerating machines. l

In Fig. 3, I have shown -an air cooling system responding parts thereof have been designated by the same numerals. In this arrangement, the condensingunit 13 which supplies refrigerant to theevaporator 12 is started whenever thethermostat 94 calls for cooling and if the load is sufliciently low to be carried by one unit, the

condensing unit 1.5 will not be started.` In order to accomplish this result, I provide a switch |01 actuated by a pressure responsive device |08 responsive to the pressure in thesuction line 84, an overcenter spring |08a being provided to profor delaying the closing of the switch for a predetermined period after the coil |09 has been energized.v In the arrangement illustrated, the device is a dashpot' arranged to delay the picking up of the switch I0. If the pressure in thesuction vline 84 is reduced to a predetermined low value before the switch ||0 is closed, the closing of the switch will not start themotor 86 because the device |08 will have operated to open the switch |01. Unnecessary starting of themotor 86 is thereby prevented. Should the condensingunit 13 at any time be unable to carry the load of the system as determined by the suction pressure in theconduit 84, the switch |01 will be closed and the motor l86 will be started to drive the 'condensing unit 15 and operate theevaporator 14 to cool the air in the duct. Operation of the condensingunits 13 and 15 will continue until the demand for cooling is satisfied as determined by thethermostat 94 or until the back pressure in one or both of thesuction lines 84 and 9| reaches a predetermined minimum as determined by the pressure responsive elements |04 and |05.

From the foregoing, it is readily apparent that I have provided a simple and effective arrangement for dividing the load of a fluid cooling sys- -tem between two or more available condensing While I have described my invention in connection with systems for cooling air, other applications will readily be apparent to those skilled in the art, I do not, therefore desire my invention to be. limited to the particular constructions shown and described and I intend in the appended claims to cover all modifications within the spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A fluid cooling system including a refrigerant evaporator, means including two condensing units for supplying refrigerant to said evaporator and for withdrawing refrigerant from said evaporator, each of said condensing units including means dependent upon a predetermined pressure of refrigerant Withdrawn from said evaporator for stopping the operation of said unit, and means dependent upon concurrent operation of said units and responsive to a pressure of said withdrawn refrigerant greater than the predeter-` mined pressure at which the operation of either of said unitsvis stopped by said last-mentioned 'means for stopping the other of said units.

condensing units "for supplying refrigerant to duce a snap action. When the thermostat callsv for coolingand theswitch 98 is operated to` 4 said evaporator and for withdrawing refrigerant from said evaporator, each of said condensing units including means responsive to the suction pressure thereof for stopping the operation thereof at a predetermined low pressure, and means dependent upon a predetermined pressure of the refrigerant withdrawn from said evaporator and independent of said last-mentioned means for stopping the operation of one of said condensing units, all of said stopping means cooperating to determine the sequence of operation of said condensing units.

3. A fluid cooling system including a refrigerant evaporator, means including two condensing units for supplying refrigerant to said evaporator and for withdrawing refrigerant from said evaporator, means dependent upon a demand for coolingfor starting one of :aid units, means dependent upon pressures in excess of a predetermined pressure of the refrigerant withdrawn from said evaporator for starting the other of said units to maintain both of said units in operation, and means dependent upon concurrent operation of said units and responsive to a pressure in excess of said last-mentioned predetermined pressure for stopping the operation of said one of said units. 1

4. A fluid cooling system including a refrigerant evaporator, means including two condensing units of different full load capacities for supplying refrigerant to said evaporator and for withdrawing refrigerant from said evaporator, means dependent upon a demand for'cooling for starting the one of said units having the lower capacity, means dependent upon pressures in excess of a predetermined pressure of the refrigerant withdrawn from said evaporator for starting the one of said units having the higher capacity to maintain both of said units in operation, and` means dependent upon operation of said higher capacity unit and responsive to a predetermined pressure of said withdrawn refrigerant in excess of said lastmentioned predetermined pressure for stopping the operation of said lower capacity unit.

5. A fluid cooling system including a refrigerant evaporator, means including two condensing units for supplying refrigerant to said evaporator and for withdrawing refrigerant from said evaporator, means dependent upon a demand for cooling for starting one of said units, means responsive to a predetermined low pressure of said refrigerant withdrawn from said evaporator for stopping said unit, means dependent upon pressures in excess of a predetermined pressure of the refrigerant withdrawn from said units for starting the other of said units to maintain both of said units in operation, means dependent upon operation of both of said units and responsive to a pressure in excess of said last-mentioned predetermined pressure for stopping the operation of said one of said units, and means for delaying the starting of said second unit for a predetermined interval of time after the pressure of said withdrawn refrigerant has reached said predetermined pressure in response to which said other of said units is started.

6. A iiuid cooling system including two refrigerating machines, each of said machines having an evaporator, means for circulating a fluid to be cooled first over one of said evaporators and then over the other of said evaporators, vmeans for controlling said machines, and means dependent upon a predetermined load on one of said machines for stopping the other of said machines.

7. A fluid cooling system including two refrig- `erating machines, each of said machines having an evaporator, means for circulating a fluid to be cooled rst over one of said evaporators and then over the other of said evaporators, means for controlling said machines, means for delaying the starting of one of saidvmalchines for a predetermined interval of time after operation of said controlling means, and means dependent upon a predetermined load on the other of said machines for stopping said one of said machines.

8. A fluid cooling System including two refrigerating machines, leach of said machines comprising a compressor and a condenser and an evaporator, each of said machines including a pressure operated device for stopping the operation of the compressor thereof, means for circulating a fluid to be cooled over said evaporators in series, means for controlling the operation of said machines, and means responsive to a predetermined pressure of the refrigerant on the suction side of one of said compressors for stopping the operation of the other of said compressors.

9. A fluid cooling system including two refrigerating machines, each of said machines comprising a compressor and a' condenser and an evaporator, means for circulating a fluid t0 be cooled over one of said evaporators and then over the other of said evaporators, means for controlling said machines to supply refrigerant to and withdraw refrigerant from said evaporators, and means responsive to a predetermined pressure of the refrigerant withdrawn from said other of e said evaporators for stopping the supply of refrigerant to said one of said evaporators.

10. A fluid cooling system including two refrigerating machines, each of said machines comprising a compressor and a condenser and an evaporator, means for circulating a fluid to be cooled over one of Asaid evaporators and then over the other of said evaporators, means for controlling said machines to supply refrigerant to and withdraw refrigerant from said evaporators. and means responsive to a predetermined pressure of the refrigerant withdrawn from said oneof said evaporators for stopping the supply of refrigerant to said other of said evaporators.

11. 'A fluid cooling system including two refrigerating machines, each of said machines comprising a compressor and a condenser and an evaporator, means for circulating a fluid to be cooled over one of said evaporators and then over the other of said evaporators, means forcentrolling said machines, means for preventing the starting of said refrigerating machine including said one evaporator for a predetermined interval of time after the starting of said other refrigerating machine by operation of said controlling means, and means repsonsive to a predetermined pressure of the refrigerant withdrawn from said other of said evaporators for stopping the supply of refrigerant to said one of said evaporators.

HARRY R. CRAGO.

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