US2745255A - Defrosting refrigerating apparatus - Google Patents

Description

May 15, 19 L. A. PHILlPP DEFROSTING REFRIGERATING APPARATUS Filed July 30, 1952 INVENTOR. Akw/Pmvw fl. PHILIP) BY HTTORNEY States Lawrence A. Philipp, Detroit, Mich assignor to American Motors Corporation, a corporation of Maryland Application July 30, 1952, Serial No. 301,641

2 Claims. (Cl. 62-3) This invention relates to refrigerating apparatus and more particularly to the arrangement for defrosting the refrigerant evaporator of the cooling system thereof.

One of the objects of my invention is to provide a new and improved method for defrosting the evaporator of a refrigerating system by dumping a measured quantity of liquid refrigerant from the evaporator into direct contact with the motor-compressor unit to evaporate the same by the heat of the motor-compressor unit and to utilize the latent heat of such evaporation by conducting such heat into the interior of the evaporator.

Another object of my invention is to increase the pressure within the system to cause additional liquid refrigerant to flow into contact with the motor-compressor unit for evaporation immediately following the dumping action of the liquid from the evaporator into direct contact with the motor-compressor unit whereby liquid refrigerant is passed from the evaporator to the motor-compressor unit for evaporation throughout the defrost period of the evaporator.

Another object of my invention is to provide a refrigerating system including a motor-compressor unit and a refrigerant evaporator with an unrestricted flow between the outlet of the evaporator and the motor-compressor unit and arrange for dumping the liquid refrigerant above a certain level in the evaporator into contact with the motor-compressor unit for evaporation so that the latent heat of evaporation may be conducted to the evaporator for rapidly defrosting said evaporator.

Another object of my invention is to provide for dumping liquid refrigerant from the evaporator into contact with the motor-compressor unit to evaporate the refrigerant so that the latent heat of evaporation may be conducted to the interior of the evaporator to rapidly defrost same and have the additional provision for increasing the pressure within the interior of the evaporator to cause additional liquid refrigerant to flow into contact with the motor-compressor unit whereby it is evaporated and the latent heat of such evaporation is conducted to the interior of the evaporator to continue the defrosting action of the refrigerant evaporator.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the acompanying drawings, wherein a preferred form of the present invention is clearly shown.

In the drawing, the view shown is a diagrammatic illustration of a system embodying features of my invention.

In accordance with my invention I provide an improved arrangement in a refrigerating system for rapidly defrosting the refrigerant evaporator thereof. My improved arrangement includes utilizing inherent characteristics of a refrigerating system to rapidly defrost the refigerant evaporator thereof. The inherent characteristics of the system include utilizing the heat of the motor-compressor unit to evaporate liquid refrigerant which is conducted from the refrigerant evaporator into the motor-compressor casing where the liquid is conducted into direct contact with the motor-compressor unit and in contact with the casing which encloses said unit. My invention includes the provision of the refrigerant accumulator having an unrestricted outlet and a connection and arrangement for dumping a measured quantity of liquid refrigerant therefrom into said unit upon initiation of the defrost operation. The operation of dumping the liquid refrigerant into the motor-compressor unit and the operation of connecting the compressor outlet through the by-pass are initiated at the same time to supply liquid refrigerant to the motor-compressor where the evaporation of such liquid takes place. This latent heat of evaporation is conducted through the by-pass conduit into the refrigerant evaporator wherein it is condensed and the latent heat of condensation causes rapid defrosting of the refrigerant evaporator. After such refrigerant is condensed in the evaporator it is again passed through the evaporator accumulator outlet to the motor-compressor unit. Upon completion of the defrost cycle, the system is automatical ly returned to normal operation in response to a certain increased temperature of the refrigerant evaporator. Furthermore, inherent characteristics of this refrigerating system are utilized in a new and improved manner to rapidly defrost the refrigerant evaporator before articles stored therein have an opportunity to thaw or melt before the defrost cycle is over and the system is returned to normal operation.

Referring to the drawing by characters of reference, the refrigerating apparatus shown comprises, in general, a refrigerant evaporator 26, a refrigerant motor-compressor unit 22, and a refrigerant condenser 24. Refrigerant supply and return lines 26 and 28 respectively, operatively connect the evaporator 29 and motor-compressor unit 22 together, and a conduit 30 connects the outlet of the motor-compressor 22 to the inlet of the condenser 24.

The evaporator 20 is illustrated as being of the socalled U-shaped type, although other types may be used, and includes a refrigerant accumulator 32 which is preferably located at or near the top of the evaporator. Also, as illustrated, the evaporator 20 and accumulator 30 are proportioned in capacity with respect to the amount of refrigerant charge used, such that during normal operation, the lower portion of the accumulator contains a large body of liquid refrigerant and the upper portion of the accumulator contains refrigerantvapor. To the upper portion of the accumulator 32 is connected the refrigerant return line 28 through which refrigerant vapor is withdrawn and delivered to the motor-compressor unit 22 during the refrigerating cycle.

Refrigerant supply line 26 is preferably a small diameter or capillary tube to control flow of refrigerant from condenser 24 to the evaporator 26 and to effect a pressure differential in the system, whereas return conduit 28 is unrestricted. Supply line 26 connects to an inlet 34 of the evaporator.

The refrigerating system shown may be used in any suitable cabinet, such as the cabinet shown in my Patent No. 2,485,066, issued October 18, 1949.

The motor-compressor unit 22 includes a casing 36 in which is confined a motor 38 having a rotor 49. A compressor 42 is also confined within the casing 36. Preferably a portion of the compressor housing is placed in contact with the casing 36, as at 44, so that the heat of the compressor is conducted to the casing 36 which is exposed to environment air to permit the heat to be dissipated from the compressor. Likewise, the motor 33 is in engagement with the compressor housing so as to conduct heat from the motor to the compressor housing to the casing 36 to liberate heat from the motor. The rotor 40 is provided with a cup-shaped portion 46 for receiving liquid refrigerant from the evaporator 29 as is hereinafter described.

casing 36 to an outlet end 43 which outlet end extends sor casing 36 through the conduit 28 enters an inlet 50 a of the compressor 42. gaseous refrigerant and delivers same to the condenser coil 24. wherein it is liquified and from which it is delivered to the evaporator 20 through the liquid supply conduit 26. As previously mentioned, the conduit 26 is a capillary or small diameter tube which controls the flow of liquid refrigerant from the condenser 24 to the evaporator 20 to allow the proper amount of liquid to he delivered to the evaporator and in so doing establishes a pressure diiferential between the outlet of the compressorand the interior of the evaporator.

A thermostat 52 of the usual type may be used to control normal cycling of the refrigerating system. This thermostat includes bellows 54 which has connected thereto a thermal bulb 56 which is placed in contact with the evaporator 20. When the evaporator reaches a certain high temperature the pressure within the bellows 54 causes the snap acting thermostat 52 to close contacts 58 to initiate operation of the motor-compressor unit 22. When the temperature of the evaporator reaches a certain low point, the bellows 54 will contract and cause the snap acting thermostat to open contacts 58 and interrupt the circuit to the motor-compressor unit to cause the motor to stop operating. The circuit to the motor-compressor unit is through leads 60, 62 which have the contacts 58 therein and is connected to the main circuit lines 64, 66.

In order to maintain the foods stored within the refrigerant evaporator frozen during periods when the evaporator is defrosted, I have arranged to rapidly defrost the evaporator so that the foods do not melt during that brief period. This is accomplished by conducting hot gaseous refrigerant into the evaporator during defrosting periods and dumping liquid refrigerant from the liquid refrigerant accumulator of the evaporator into the vapor return line where such liquid is conducted to the interior of the motor compressor unit casing. This liquid passes through the outlet 48 into the interior of the cup-shaped motor rotor 46. Since the motor is very warm, the liquid refrigerant coming in contact therewith evaporates rapidly and that which is not evaporated in the cup-shaped rotor 46 is flung into contact with the motor stator 38 and about the walls of the casing into contact with the compressor housing 44. Thus the heat of the motor-compressor unit evaporates the liquid refrigerant sothat only gaseous refrigerant enters the inlet th to the'compressor unit. The inlet 50 is posilioned above the housing 44 Where liquid refrigerant may tend to settle and if desired the opening leading to the inlet 50 may be positioned on the side of the inlet 50 adjacent the side Wall'of the casing and away from the direction of which the liquid refrigerant enters the motor-. compressor casing.

When the liquid refrigerant is evaporated in the motorcompressor casing by the heat generated by the motor and compressor, the pressure in the system is considerably increased and the latent heat of evaporation is utilized for rapidly defrosting the refrigerant evaporator. The greater amount of liquid which is evaporated, the greater the amount will be the increase in pressure and the greater the amount of latent heat which is to be utilized in defrosting the evaporator. This latent heat The compressor compresses, the

is conducted to the evaporator along with the hot refrigerant gases and when these gases come in contact with the cold walls of the evaporator, the gaseous refrigerant condenses and as liquid is forced through the evaporator outlet accumulator into the return line where it is conducted again into the interior of the motorcompressor unit. I have shown a refrigerant evaporator of the type which has an accumulator or tank 32 If desired a refrigerant evaporator which has a flooded portion and liquid tank or header as disclosed in my Patent No. 2,325,706 issued August 3, 19.43, for Refrigerating Apparatus may be used. in either evaporator, the accumulator or header tank accumulates a quantity of liquid in its outlet tank whether the tank be an accumulator or header and this liquid is dumped in a measured amount into the vapor return conduit 28 to be conducted to the interior of the motor-compressor unit. Specifically as shown in the, drawings, a by-pass conduit '76 is used to by-pass the condenser 24 and oapillary tube and deliver hot refrigerant gas direct from the compresi sor to the inlet of the evaporator 29. In order to permit dumping of the liquid refrigerant from the accumulator 32, i have provided avliquid conduit 72 which is connected, to the accumulator 32 below the liquid level there: in. This conduit may be placed at any desired position between the top and lowermost portion of the ac.- curnulator 32 just so that a portion of the conduit 72 is located below the liquid level in the accumulator 32. The initial charge of refrigerant into the system deterinines the height of the liquid level in the tank. Thus when the conduit 72 is opened to permit passage therethrough, the liquid in the accumulator 32 above a certain level will fiow through conduit 72 into the vapor return conduit 2% to be conducted to the motor-compressor unit. Thus a measured amount of liquid is dumped into the vapor return conduit and the measured amount depends on how high or low it is desired to position the liquid. conduit 72 in the side wall of the accumulator. In some instances, it may be desirable to have the liquid conduit 72 adjacent to the lowermost portion'of the ac-.

cumulator 32 so as to dump the entire contents of the liquid conduit 72 so that liquid is being fed to. the motorcompressor unit to keep the pressure in the system sufiiciently high enough to properly effect rapid defrosting.

In by-pass conduit 76, I provide a normally closed solenoid valve 74 to control the flow of refrigerant there- 7 through and in conduit 72, I provide a second normally closed solenoid valve 76 to control dumping of liquid refrigerant from the accumulator 32 into return conduit 28. These valves are connected in series across leads 60, 62 by lead wires 80 and 82 and by lead 84. 80 is provided a switch 85 of well known type which is manually pressed to close the circuit and which responds to temperature rise of the evaporator to open the circuit. This thermostat is shown mounted on one side of the evaporator 26 and comprises a fixed contact 86 and a bimetal blade 88 carrying a cooperating contact 90.

When thermostatic blade '88 is flexed manually to the position shown, the circuit is made through contact 86 90 and both of the solenoid valves 74, 76 are energized and opened. With the valves 74, 76 open, gaseous refrigerant from the compressor will now by-pass the ceude ser 2,4 and cap ll ry t be 26 and PaS hr ugh t e bY-PQSS ond it v to the p ssor o ef ostthee apor tor.

In lead wire v Simultaneous with the opening of solenoid valve 74, valve 76 is energized and opens to permit the dumping of the liquid refrigerant within accumulator 32 into the return conduit 2-3. Thus, it will be seen that refrigerant gas flowing through by-pass 70 will permit dumping of the accumulator to quickly result in defrosting the evaporator. When the temperature of the evaporator increases to such temperature that defrosting is assured, the thermostatic blade 68 parts contacts 86, 90 causing both solenoid valves to close which automatically returns the system to normal operation under control of thermostat 52. An automatic thermostat may be used if desired, for example, one which is controlled by a timer as is well known in the art.

From the foregoing, it will be noted that I have provided a new arrangement for defrosting a refrigerant evaporator of a refrigerating system by dumping a measured quantity of liquid refrigerant from the evaporator accumulator into the motor-compressor unit wherein the refrigerant is evaporated and the latent heat of evaporation is utilized to increase the vapor pressure and temperature in the evaporator. This is caused by the sensible heat stored in the motor-compressor unit and casing, which heat is generated by mechanical friction and additional heat by electrical losses which are effective to evaporate the liquid which is returned to the motor-compressor unit and returned to the evaporator in the form of hot gas which condenses in the evaporator with the accompanying latent heat of condensation providing for rapid defrosting of the evaporator. It will be also noted that I have provided an improved defrosting system in which the time element of defrosting is reduced by dumping the measured quantity of liquid refrigerant in the accumulator into the motor-compressor unit upon initiation of the defrosting action and later causing additional liquid which has been condensed in the evaporator to flow through the accumulator into direct contact with the motor-compres- 501' unit.

Although only a preferred form of the invention has been illustrated, and that form described in detail, it will be apparent to those skilled in the art that various modi fications may be made therein without departing from the spirit of the invention or from the scope of the appended claims.

I claim:

1. Refrigerating apparatus comprising a system having a motor-compressor unit, arefrigerant condenser connected to said unit, a refrigerant evaporator having a liquid refrigerant containing accumulator at its outlet, a vapor return conduit having one end connected to said accumulator above the level of liquid refrigerant therein and the other end thereof connected to said unit adjacent the motor thereof, a supply conduit connected on one end thereof to the condenser and on the other end to said evaporator, a valve controlled by-pass conduit having one end thereof connected to the outlet of said compressor and the other end thereof being connected to the inlet of said evaporator and a valve controlled dumping conduit having one end thereof connected to said accumulator below the level of liquid refrigerant therein and the other end thereof being connected to said vapor return conduit.

2. Refrigerating apparatus comprising a system having a motor-compressor unit, a refrigerant condenser connected to said unit, a refrigerant evaporator having a liquid refrigerant containing accumulator at its outlet, a vapor return conduit having one end connected to said accumulator above the level of liquid refrigerant therein and the other end thereof connected to said unit adjacent the motor thereof, a supply conduit connected on one end thereof to the condenser and on the other end to said evaporator, a valve controlled by-pass conduit having one end thereof connected to the outlet of said compressor and the other end thereof being connected to the inlet of said evaporator, a valve controlled dumping conduit having one end thereof connected to said accumulator below the level of liquid refrigerant therein and the other end thereof being connected to said vapor return conduit and thermostatic means responsive to changes in temperature of said evaporator for controlling the valves of said valve controlled by-pass conduit and dumping conduit.

References Cited in the file of this patent UNITED STATES PATENTS 2,281,770 Hoesel May 5, 1942 2,430,960 Soling Nov. 18, 1947 2,608,834 McCloy Sept. 2, 1952 2,627,730 Zearfoss Feb. 10, 1953

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