US2178445A

US2178445A - Refrigerating machine

Info

Publication number: US2178445A
Application number: US183465A
Authority: US
Inventors: Roman C Warneke
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1938-01-05
Filing date: 1938-01-05
Publication date: 1939-10-31
Anticipated expiration: 1956-10-31

Description

Oct. 31, 1939. R. c. WARNEKE 2,178,445

REFRIGERATING MACHINE Filed Jan. 5. 1938 2 Sheets-Sheet '1 Invent or: Pom an C. Warne ke,

y His/Attorney O 31, 1939- R. c. QWARNEKE 2,178,445

REFRIGERATING MACHINE Filed Jan. 5, 1958 '2 Sheets- Sheet 2 CLDJEO Inventor Roman C. Warneke,

by $21 M.

His Attorney.

Patented Oct. 31, 1939 UNITED STATES REFRIGERA'IING MACHINE Roman O. Warneke, Fort Wayne, Ind., assignor to General Electric Company, a corporation of New York Application January 5, 1938, Serial No. 183,465

12 Claims.

My invention relates to refrigerating machines and particularly to arrangements for defrosting the evaporators of refrigerating machines.

Evaporators" of refrigerating machines which are utilized to cool air and which are operated at temperatures below the freezing point of water condense moisture on their surfaces which freezes and forms a layer of frost. In order to maintain eflicient operation of the evaporator, it

' is desirable to remove the layer of frost before it attains substantial thickness. The defrosting of an evaporator may be accomplished in several different ways. For example, the refrigerating machine may be shut down so that the tempera ll ture of the evaporator rises and the frost is melted. Such an arrangement, however, requires a considerable period of time for defrosting and it is, therefore, preferable to provide an arrangement for supplying additional heat to the evaporator in order to. melt the frost more quickly.

The arrangements for supplying additional heat to the evaporator include heating elements arranged adjacent the evaporator and arrangements for admitting hot liquid or gaseous refrigerant to the evaporator. When heat is supplied to the evaporator, liquid refrigerant therein may be boiled violently and slugs of liquid refrigerant may enter the suction line, and be drawn into the compressor where they are apt to cause damage to the valves. Accordingly, it

is an object of my invention toprovide an improved arrangement for defrosting the evaporator of a refrigerating machine and for insuring the removal of liquid refrigerant from the evaporator before the application of heat to defrost the evaporator.

Another object of my invention is to provide a refrigerating machine and an improved arrangement utilizing hot compressed refrigerant for defrosting the evaporator of the refrigerating machine.

Further objects and advantages of my invention 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 schematic diagram illustrating a refrigerating machine embodying my invention, and Fig. 2 is a schematic diagram of a similar system showing a modification-o my invention.

Referring now to the drawings, in Fig. 1. I

have shown a refrigerating machine including a compressor I0 driven by an electric motor II, a condenser I2 and an evaporator I3. The compressor I 0 is arranged to compress gaseous relfrigerant and to discharge the compressed refrigerant into the condenser I2 where it is cooled and liquefied, the liquid refrigerant collecting in a receiver l4. Liquid refrigerant flows from the receiver I4 to the evaporator I3' through a liquid line or conduit I5, the rate of flow being controlled by a thermostatic expansion value I6 having a thermostatic element I'I secured to a suction line I8 in the usual manner. The evaporator I3 is arranged within a space to be cooled indicated by a broken line at I9, a fan 20 driven. 15

by a motor 2| being provided to circulate air over the evaporator and through the space I9. The liquid refrigerant within the evaporator I3 is vaporized by the absorption of heat from the air within the space I9 and .the vaporized refrigerant is withdrawn from the evaporator through the suction line I8 by operation of the compressor Ill. The refrigerating machine is controlled in response to the temperature within the space I9, a thermostat 22 being provided for this purpose. Power for driving the motors It and 2| and for energizing the control circuits, is supplied from lines 23. When there is a demand for cooling of the air within the space I 9-, the thermostat 22 moves to the left and connects a coil 24 of a solenoid operated switch 25 across the secondary of a transformer 26 thereby energizing the coil and picking up the switch 25. The top arm' of the switch 25 closes a holding circuit for the coil 24 and the two lower arms connect the motor II across the lines 23 through lines 21?. The motor is thereby started and operates the compressor I0 to supply refrigerant to the evaporator I3. The motor 2| is connected across lines 28 and is operated continuously during normal operation of the refrigerating machine to circulate air through the space I9. When the thermostat 22 is satisfied, it moves to the right and short-circuits the coil 24 causing switch 25 to drop out and deenergize the motor II thereby stopping the operation of the compressor.

During the operation of the refrigerating machine, moisture is condensed on the surface of the evaporator I3 and a layer of frost is thereby formed. It is desirable to pevent the formation of any substantial thickness of frost on the evaporator and I, therefore, provide an arrangement for defrosting the evaporator. The defrosting arrangement as illustrated includes a conduit or passage 29 arranged to by-pass the 55 iiii condenser i2 and the expansion valve l3 so that hotcompressed refrigerant may be delivered from the compressor l directly to the evaporator l3. The passage 23 is restricted by a fixed throttle valve 33 so that the normal operating pressures of the compressor Ill will be maintained during defrosting. Conduit 29 is provided with a solenoid or electrically operated valve 3| which is maintained closed during normal operation of the refrigerating machine. The liquid line I I is provided with an electrically operated or solenoid valve -32- which is provided with a normally energized coil 33 connected across the lines 23 to maintain the valve open during normal operation of the refrigerating machine. In order to defrost the evaporator I3, I provide an arrangement for deenergizing the valve operating coil 33 so that the supply of liquid refrigerant to the evaporator through the line i! is stopped, and for opening the valve 3| to admit hot gaseous refrigerant to the evaporator. In order to insure removal of the liquid refrigerant from the evaporator before the admission of hot gaseous refrigerant, I provide a switch 34 arranged in the circuit of a coil 35 which is the operating coil of the valve 3|. The switch 34 is operated by an expansible bellows 34a responsive to the pressure within the conduit Ii between the valve 32 and the expansion valve.

The continued operation of the compressor after the valve 32 has been closed vaporizes the liquid refrigerant in the evaporator and removes it therefrom and from the conduit l5. When the liquid has been removed, the pressure within the evaporator is substantially reduced and the bellows 34a contracts to close the circuit of the coil 35 from one of the lines 23 to a line 33; this opens the valve 3| to admit hot refrigerant to the evaporator to melt the layer of frost on the surface of the evaporator. It is therefore apparent that the defrosting operation can be affected only after removal of the liquid refrigerant from the evaporator.

The defrosting operation in the system shown in Fig. 1 is initiated by a time-controlled switch 31 which is operated by a motor 33 connected across the lines 23. The motor 33 rotates a cam comprising two

segmental portions

39 and 40 to operate a switch arm 4|. The motor may, for

' example, be arranged to rotate the cam at the rate of one revolution per hour, and when a notched portion 42 of the cam moves into po sition adjacent a follower 43 secured to the switch arm 4|, the switch is opened, a spring 44 being provided to cause the switch arm to follow the cam surface. The period of defrosting may be varied by adjusting the positions of the

portions

39 and 40 of the cam. When the switch 4| is opened, the coil 33 is deenergized as is also the motor 2|. The supply of liquid refrigerant to the evaporator and the circulation .of air over the evaporator are thereby stopped. The re- 1 the liquid line l between the evaporator and the valve 32, the pressure responsive switch 34 will close to energize the coil 35 and open the valve 3| thereby admitting hot gaseous refrigerant to the evaporator. At the end of the defrosting period the cam operated switch 4| will close thereby energizing the coil 33 and opening the valve 32 to admit to the liquid line I! refrigerant at the full pressure of the condenser l2 thereby opening the switch 34 and deenergizing the coil 35 to stop the supply of hot refrigerant through the passage 29. Operation of the fan. 2| is also restored by the closing of the switch 4| and the normal operation of the refrigerating machine to cool the air circulated over the evaporator continues until the time-controlled switch 31 again starts the defrosting operation.

Referring again to the drawings, in Fig. 2, I have shown a schematic diagram illustrating a modified form of my invention. The arrangement shown in Fig. 2 is similar to that shown in Fig. 1 and corresponding parts have been designated by the same numerals. Both arrangements accomplish the same purpose in that the admission of hot compressed refrigerant to the evaporator for defrosting is delayed for an interval of time to allow the compressor to remove the liquid refrigerant from the evaporator. The arrangement shown in Fig. 2 differs from that shown in Fig. 1 in that a time control switch 45 is utilized to delay the admission of hot gaseous refrigerant for a definite interval of time after the initiation of the defrosting operation and the pressure responsive element is, therefore, omitted. The time control switch 45 includes a cam comprising

adjustable segments

43 and 41 and arranged to operate a switch arm 43 to effect defrosting a predetermined interval of time after the opening of the switch arm 4| by '1 the time control switch 31. The switch arm 43 is provided with a cam follower 43a pressed against the surface of the cam by a spring 43.

The switch arm 43 is arranged to close the cir- Y cult of the operating coil 33 of the valve 3| whenever the follower 43a falls into a gap or notch 48a formed. between the

portions

48 and 41 of the cam. The cam for operating the switch 43 is rotated by a synchronous motor 33 connected in parallel with the motor 33 which drives the cam of the switch 31. Since the two synchronous motors are connected to the same circuit, the cams driven thereby rotate in fixed relation and the cam surfaces 43 and 41 may be adjusted to actuate the switch and close the switch arm 43 a predetermined interval after the opening of the contacts of the switch arm 4|. This interval of time which is determined by the relative angular positions of the cam portions 33 and 46 may be selected so that it is sufficient to insure the withdrawal by the compressorof the liquid refrigerant from the evaporator l3. In order to insure continuous operation of the compressor while the switch arm 43 is in its closed position, I provide a small heater 5| adjacent the thermostat 22 and arrange the heater to be energized through a back contact 52 engaged by the switch arm 4| when in its open position. The heater 5| heats the thermostat 22 and maintains the thermostat in position to call for cooling and actuate the compressor.

During the operation of the cooling system shown in Fig.2 whenever the time control switch 31 opens the circuit of the coil 33 and motor 2| a predetermined interval of time elapses before the switch 45 closes the circuit of the coil 33 to open the valve 3| and admit hot gaseous refrigerant to the evaporator l3. During this interval of time, as long as the switch 31 is in its open position, the compressor is maintained continuously in operation due to the heat produced by the coil 5| adjacent the control thermostat 22 and the compressor, therefore, removes the liquid refrigerant from the evaporator l3. The switch 45 then actuates the arm 48 to energize the coil 35 and open the valve 3|, thereby admitting hot gaseous refrigerant to the evaporator. At the end of the defrosting period determined by the adjustment of the cam portions 46 and 41, switch 45 operates the arm 48 to open the circuit of the coil 35 and stop the admission of hot gaseous refrigerant to the evaporator. At the same time or shortly thereafter the time control switch 31. is also operated to open the circuit of the coil 5i and close the circuit of the coil 33 and motor 2| thereby restoring the cooling system to its condition for normal operation.

From the foregoing, it is readily apparent that I have provided a simple and effective arrangement for defrosting the evaporator of a refrigerating machine and for insuring the. removal of I liquid refrigerant from the evaporator before the defrosting operation can be effected.

While I have described my invention in connection with refrigerating machines utilized for cooling the air circulated within a closed space, 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 construction shown and described, and I intend in the accompanying 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 refrigerating system including an evaporator, means including a refrigerant line for supplying liquid refrigerant to said evaporator, means for withdrawing gaseous refrigerant from said evaporator. means arranged to supply heat to said evaporator for defrosting said evaporator,

means for stopping the supply of liq id refrigerant to said evaporator through said refrigerant line, and means dependent upon the lapse of an interval of time after operation of said stopping means for rendering effective said defrosting means to defrost said evaporator.

2. A refrigerating system including an evaporator,means including a refrigerant line for supplying liquid refrigerant to said evaporator, means for withdrawing gaseous refrigerant from said evaporator, means arranged to supply heat to said evaporator for defrosting said evaporator, means for stopping the supply of liquid refrigerant to said evaporator through-said refrigerant line, and means dependent upon the removal from said evaporator of the liquid refrigerant therein after operation of said stopping means for rendering effective said defrosting means to defrost said evaporator.

3. A refrigerating system including an evaporator, means including a refrigerant line for supplying refrigerant to said evaporator, means for withdrawing refrigerant from said evaporator, means arranged to supply heat to said evaporator for defrosting said evaporator, means for stopping the supply of refrigerant to said evaporator through said refrigerant line, and means dependent upon a predetermined low pressure within said evaporator after the supply of refrigerant through said line has been stopped for rendering efiective said defrosting means to defrost said evaporator.

operation of said system, means for withdrawing refrgerant from said evaporator, means for stopping the supply of liquid refrigerant to said evaporator, and means dependent upon a predetermined low pressure in said evaporator after said liquid supply has been stopped for rendering effective said hot gaseous refrigerant supplying means to defrost said evaporator.

5. A refrigerating system including a compressor and a'condenser and an evaporator arranged in series in a closed refrigerant circuit, said cfrcuit including a liquid line connected between said condenser and said evaporator and an expansion valve in said line for controlling the flow of refrigerant to said evaporator, means including a restricted passage arranged to bypass said condenser for conveying hot gaseous refrigerant to said evaporator, means for maintaining said by-pass normally closed, means for stopping the flow of refrigerant from said condenser to said evaporator through said liquid lne, and means responsive to a predetermined low pressure in said liquid line after operation for stopping the supply of liquid refrigerant through said conduit to said evaporator, means dependent upon a predetermined low pressure in said evaporator after the supply of liquid refrigerant through said conduit has been stopped for rendering effective said hot gaseous refrigerant supplying means to defrost the evaporator, and means for restricting the flow of refrigerant through said gaseous refrigerant supplying means.

'7. A refrigerating system including an evaporator arranged within a space to be cooled, means including a refrigerant conduit having an expansion valve therein for supplying liquid refrigerant to said evaporator, means for withdrawing refrigerant from said evaporator, means responsive to the temperature within the space to be cooled for controlling the operation of said refrigerant supplying means, means for supplying hot refrigerant to said evaporator, said hot refrigerant supplying means being ineffective during normal operation of said system, means for stopping the supply of liquid refrigerant to said evaporator through said conduit, and means dependent upon a predetermined low pressure in said evaporator after the supply of refrigerant through said conduit has been stopped for rendering effective said hot refrigerant supplying means to defrost said evaporator.

8. 'A refrigerating system including a compressor and a condenser and an evaporator arranged in series in a closed refrigerant circuit, sad circuit including a conduit connected between said condenser and said evaporator and an expansion valve in said conduit for controliii? 4. A refrigerating system including an evapo-ling the flow of refrigerant to said evaporator, 35,

means including a restricted passage arranged F Y-pw said expansion valve and said condenser for conveying hot gaseous refrigerant to said evaporator, means including an electrically operated valve for maintaining said by-pass normally closed, means including an electrically operated valve arranged in said conduit for stopping the flow of refrigerant through said conduit to said evaporator, means for closing said electrically operated valve in said conduit, and means dependent upon a predetermined low pressure in said evaporator after said valve in said conduit has been closedfor actuating said valve in said by-pass to admit hot gaseous refrigerant to said evaporator.

9. A refrigerating system including a compressor and a condenser and an evaporator arranged in series in a closed refrigerant circuit, said circuit including a conduit connected between said condenser and said evaporator and an expansion valve in said conduit for controlling the flow of refrigerant to said evaporator, means including a restricted passage arranged to by-pass said expansion valve and said condenser for conveying hot gaseous refrigerant to said evaporator, means including a normally deenerglzed electrically operated valve for maintaining said by-pass normally closed, means including an electrically operated valve arranged in said conduit for stopping the flow of refrigerant from said conduit to said evaporator, said last-mentioned electrically operated valve being normally energized to permit the flow of refrigerant through said conduit, means for deenergizing said electrically operated valve in said conduit to stop the flow of refrigerant through said conduit, and means dependent upon a predetermined low pressure in said evaporator after said valve in said conduit has been closed for energizing said valve in said by-pass to admit hot gaseous refrigerant to said evaporator.

arrasss 10. A refrigerating system including an evaporator, means including a fan for circulating air over said evaporator, means including a refrigerant linefor supplying refrigerant to said evaporator, means for withdrawing refrigerant from said evaporator, means arranged to supply heat to said evaporator for defrosting said evaporator, means for stopping the supply of refrigerant to said evaporator through said refrigerant line and for stopping the operation of said fan, and means dependent upon a predetermined low pressure within said evaporator after the supply of refrigerant through said line has been stopped for rendering effective said defrosting means to defrost said evaporator.

11 A refrigerant system including an evaporator, means including a refrigerant line for supplying refrigerant to said evaporator, means for withdrawing refrigerant from said evaporator, means arranged to supply heat to said evaporator for defrosting said evaporator, means for stopping automatically and periodically the supply of refrigerant to said evaporator through said refrigerant line, and means dependent upon the lapse of an interval of time after operation of said stopping means for rendering effective said defrosting means to defrost said evaporator.

12. A refrigerating system including an evaporator, means including a refrigerant line for supplying refrigerant to said evaporator, means for withdrawing refrigerant from said evaporator, means arranged to supply heat to said evaporator for defrosting said evaporator, means for stopping automatically and periodically the supply of refrigerant to said evaporator through said refrigerant line, and means dependent upon a predetermined low pressure within said evaporator after the supply of refrigerant through said line has been stopped for actuating said defrosting means to defrost said evaporator.

ROMAN C. WARNEKE.