US2692481A - Dual evaporator air cooling apparatus - Google Patents

Description

Oct. 26, 1954 5 sc w 2,692,481

DUAL EVAPORATOR AIR COOLING APPARATUS Filed March 16, 1951 2 Sheets-Sheet l a FIG. I

ROOM AIR i ROOM AIR W 80 TEMPERATURE 70- TO- 60- 60- EVAPORATOR E (TEMPERATURE 50- 5( I 40- 4o- EVAPORATOR TEMPERATURE zofiuu-mlmm nimum HRS. 5 l0 HRS. IO 20 84 4 H95 FIG.

F|G.2 BY

Oct. 26, 1954 s. M. SCHWELLER 2,692,481

DUAL. EVAPORATOR AIR COOLING APPARATUS Filed March 16, 1951 2 S heets-Sheet 2 Patented Oct. 26, 1954 DUAL EVAPORATOR AIR COOLING APPARATUS Sylvester M. Schweller, Dayton, Ohio, assignor to General Motors Corporation, Dayton, Ohio, a

corporation of Delaware Application March 16, 1951, Serial No. 215,985

6 Claims.

This invention relates to refrigerating apparatus and more particularly to air conditioning apparatus of the type used for room cooling and room dehumidification.

Air conditioning apparatus is customarily designed to operate down to a certain air temperature and the smallest size of evaporator is selected which will perform properly down to such a temperature. It sometimes happens that some individual users desire to operate at temperatures below those for which the apparatus is designed. Under such conditions there is often an accumulation of frost and ice upon a portion of the evaporator which gradually builds up as the adverse'conditions continue until the operation of the air conditioning apparatus becomes seriously impaired.

- It is an object of my invention to provide a control device which will prevent this accumulation of frost and ice upon the evaporating means of air conditioning apparatuses.

It is another object of my invention to provide a thermostatic control responsive to temperature upon the coldest part of the evaporator which will stop refrigeration in the evaporator until the temperature of the evaporator rises sufficiently high to prevent frosting and the accumulation of ice.

These objects are obtained in one form of my invention by providing a thermostatic switch in series with one compressor motor of a dual air conditioning room cooling apparatus. This thermostatic switch has its thermostat bulb connected to the coldest portion of the lower evaporator and in particular the bulb is clamped to the lowermost return bend nearest the exit of the air stream drawn through the evaporator. This switch opens the compressor motor circuit at about 35 F. and does not close the circuit until about a temperature of 60 F. is reached. In another form, primarily designed for dehumidification, a thermostat switch is connected in series with the motor compressor unit and has its bulb clamped to the coldest portion of a spiral-shaped evaporator. This coldest portion is located on the second and third outermost coils of the spiral evaporator. This thermostat is set to open a compressor motor circuit at about 28 F. and to close the circuit at about 45 F.

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

In the drawings:

Fig. 1 is a vertical sectional view, partly diagrammatic, of a window type room cooling air conditioning apparatus embodying one form of my invention;

Fig. 2 is a fragmentary enlarged view of a portion of the lower evaporator showing the clamping of the thermostat bulb to the return bend;

Fig. 3 is a temperature-time graph showing the effect upon the evaporator temperature and the room air temperature by operation of my control;

Fig. 4 is a similar temperature time graph for the form of air conditioning apparatus shown in Fig. 5;

Fig. 5 is a vertical sectional view, partly diagrammatic, of an air conditioning apparatus primarily designed for dehumidifying a room or basement and;

Fig. 6 is a fragmentary View showing the particular clamping arrangement of the thermostatic bulb upon the evaporator. 4

Referring now to the drawings and more particularly to Fig. 1, there is shown a window air conditioner 22 adapted to be placed through the opening in the wall 20 of a room or other enclosure to be cooled. This particular apparatus is of the dual type and includes a lower evaporator 24 and an upper evaporator 26 located directly over the lower evaporator 24. These evaporators are both of the cross fin and tube type and are located directly adjacent the room air inlet opening 28 0f the apparatus 22 so that all of the incoming air must flow through the evaporators 24 and 26. Also in this incoming air stream is a filter 30 which removes solid particles from the air stream after the air is passed through the evaporator 24 and 26. This air circulation is provided by a fan 32 driven by an electric motor 34 which also drives the condenser fan 36. The air which is drawn through the evaporators 24 and 26 and the filter 30 by the fan 32 is discharged back into the room through the openings 38 and 40. A partition wall 42 of thermal insulating material divides the air cooling portion of the apparatus from the refrigerant liquefying portion.

The refrigerant liquefying portion comprises a motor compressor 44 which withdraws evaporated refrigerant from the upper manifold of the lower evaporator 24 through the suction conduit 46 and compresses and forwards the compressed refrigerant to the condenser 48 Where the refrigerant is condensed and returned through a capillary tube restrictor 50 to the bottom manifold of the lower evaporator 24. A similar motor compressor unit 52 is provided for withdrawing evaporated refrigerant from the upper manifold of the upper evaporator 26 through the suction conduit 54. This evaporated refrigerant is compressed by the motor compressor unit 52 and forwarded to the condenser 55 where the compressed refrigerant is liquefied and returned through the capillary tube restrictor 58 to the bottom manifold of the upper evaporator 26. The condenser fan 36 draws air from the exterior of the room 60 through the openings 52 and 64 for cooling both compressors and both condensers after which the air is discharged directly to the outside atmosphere.

The motor 34 is connected by the conductors 68 to the conductors 68 and I so that the fans 32 and 35 operate continuously. It has been found when such apparatus reaches a temperature below which it is designed to operate such as 70 F., but under certain conditions of humidity, frost begins to accumulate upon the lower rear tubes of the lower exaporator 24. Continued operation under such conditions causes the frost and ice to gradually accumulate so as to seriously block the flow of air through the lower evaporator 24. The increased restriction of the air flow through the lower evaporator 24 increases the rate of frost and ice accumulation so that the situation becomes progressively worse as long as the adverse conditions continue. When the situation is discovered and the air conditioning apparatus is shut down, there is a considerable amount of ice which must melt before the operation of the apparatus can be resumed. The frost and ice water resulting from this melting sometimes overflows the facilities provided for the collecting and disposal of water condensed from the air and may drip upon the floor. Sometimes this overflow or dripping is caused by freezing or clogging of drainage facilities by the ice and frost.

To prevent such undesirable situations, I have provided a simple bellows actuated snap-acting thermostat I2 which may be of the type shown in Patent 2,479,047 having its contacts 14 connected in series with the supply conductor I6 which with the supply conductor I8 supplies the motor compressor unit 44 with electric energy. The thermostat 12 has the end of its temperature sensitive capillary tube 89 formed into a serpentine shape so as to serve as a bulb which is wrapper around the lower rear return bend 82 of the lower evaporator 24. This lower rear return bend 82 is the coldest portion of the evaporator and is the place at which the frost and ice first begins to accumulate. The reasonfor this is that it is furtherest from the incoming warm air which enters from the opening 28 and has less heat transfer with the air because of the absence of fins upon the return bend. As shown in detail in Fig. 2, the clamping of the capillary tube 80 to the return bend 82 is accomplished by a pair of plates 84 and a bolt 86 which extends through aperture in the plates 84 and through the inside of the return bend 82.

As shown by the temperature-time chart Fig. 3, the thermostat I2 is set to open when the temperature sensitive capillary tube 80 reaches a temperature of 35 F. and it is set to 'reclose when the evaporator temperature reaches 60 F. As shown by the chart, when the apparatus is started the room air and the evaporator temperature are very nearly the same. The evaporator temperature, however, falls more rapidly than the room air temperature and after about three and one-half hours of continuous operation, the evaporator temperature is reduced to about 35 F. while the room air temperature is reduced to about 68 F. If operation of the apparatus were continued these temperatures would fall still lower and frost and ice would begin to accumulate. However, since the thermostat I2 is set to open at 35 F. the lower evaporator 24 will be disabled thereby causing the evaporator 24 to begin to warm up. The room airtemperature will also warm up due to the reduced cooling effect. The fans 32 and 36 however, continue to operate and the upper refrigerating system may likewise continue to operate. Cycling of the lower refrigerating system will continue on this basis as long as the temperature is at such a low level. In this way frosting is prevented and maximum trouble-free use of the apparatus is obtained.

Ordinarily, no frosting or freezing of the upper evaporator 26 is encountered. However this upper system, if desired, may be controlled by a simple room thermostat 88 having contacts 90 which are connected in series with one of the conductors 92 providing a connection between the supply conductor 68 and the upper motor compressor unit 52. The second conductor 94 provides a second connection between the motor compressor unit 52 and the supply conductor 10. This room thermostat I3 8 will limit the temperature to which the room 60 will 'be cooled.

In Fig. Sthere is shown an air conditioning apparatus ZI2I for de'humidification of aroom or basement. It is provided with a cylindrical casing I23 which is adapted to be placed. over a drain. Within the cylindrical casing 1.23., there is provided a sealed motor compressor unit I215. Beneath the motor compressor unit I25 there provided a condenser I21 formed of tubing in the shape of a flat conical spiral and directly beneath it is an evaporator I29 likewise in the shape of .a flat conical spiral. The motor compressor unit I25 withdrawsevaporated refrigerant from the outside turn :of the evaporator 429 through the suction conduit I3I and-compresses this refrigerant and forwards the compressed refrigerant through the supply ocnduit 433 to the outside turn of the condenser I2 1. The innermost turns of the condenser I21 and the evaporator I29 are connected by a capillary tube westrictor I35 which controls the flow of liquid refrigerant from the condenser 1 -21 to the-evaporator [29.

Above the sealed motor compressor unit Hi, there is provided a fan I31 driven by the electric motor I39 connected by the conductors 14.4 directly to the electric :powersupply so that the fan I-3I will be operated continuously. The fan i3] draws air from the room or basemerit through the openings 143 in the bottom of the casing I23 and thence through the coils :of the evaporator I29. On the cold sur iaces of the evaporator coils I29, moisture is condensed from the air and this condensed moisture is collected by the drip collector I45 having a central discharge opening "I41 which is placed -over the drain for disposal of the condensed moisture. The air, after passing through the coils of the evaporator 129 is then reheated "by the coils of the condenser I21 and discharged-badk into the room or basement through the series of outlet openings I43 provided in the top of the cylin drical casing I23.

It has been found that when such'an apparatus is placed in very 'cold basements and operated continuously, that frost and ice begin to "collect upon the outermost turns of the evaporator I29 after .a long period of operation As shown in Fig. 4, the evaporator, temperature falls below 30 F. after about eleven or twelve years of continuous operation in a rather cool basement.

However, since the condenser IN is such close proximity to the evaporator I29 the frost does not begin to build up until lower temperatures are reached. To prevent this accumulation of frost and ice, I connect a simple bellows actuated snap acting thermostat I5I which may be of the type shown in Patent 2,479,047 having its contacts I53 connected in series with one of the supply conductors I55 of the motor compressor unit I25. The temperature sensitive capillary tube I51 connected to the bellows of this thermostat I5I hasits end portion I59 formed into a serpentine shape'and clamped on top of the second and third outermost turns of the coils of the evaporator- I29. The second and third outermost turns are the coldest turns in this evaporator and therefore are the first to frost. Y

The clamping is done by a sheet metal clamp IBI which extends over the serpentine end portion I59 of the capillary tube I57 and the second and third outermost turns of the evaporator I29. The end portions I63 and IE5 of this clamp I'BI are curled beneath the outermost and the fourth outermost coil of evaporator I 29. This insures that the operation of the thermostat I 5I will be substantially in accordance with the temperature of the second and third outermost coils of evaporator I29. The thermostat I5I is set to open at about 28 F. which is just above the temperature at which these coils begin to frost under adverse conditions. The thermostat I5I is set to reclose at about 50 F. as shown in Fig. 4. The room or basement air temperature will fall as long as the system operates and will rise when the thermostat I5I opens the compressor motor circuit. This control arrangement allows maximum use and effectiveness of this air conditioning apparatus for dehumidification and prevents failures by reason of frosting under adverse conditions.

While the form of embodiment of the invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, as may come within the scope of the claims which follow.

What is claimed is as follows:

1. A dual air conditioning apparatus for conditioning the air of an enclosure for producing human comfort including fan means for circulating air from the enclosure through the apparatus and returning the conditioned air to the enclosure, a first evaporator and a second evaporator located above the first evaporator in said circulating air, refrigerant liquefying means for supplying liquid refrigerant to and for withdrawing evaporated refrigerant from said first and second evaporators, and a thermostatic means having a thermostatic element clamped to the coldest portion of said first evaporator for disabling said first evaporator, and a room thermostat responsive to the temperature of the air in said enclosure for disabling said second evaporator.

2. Air conditioning apparatus for conditioning the air of an enclosure, including means for circulating air from the enclosure through the apparatus and returning the conditioned air to the enclosure, an evaporating means located in the apparatus in said circulating air for conditioning in the form of a cross-finned serpentine tubular structure having return bends at least at one 6 end thereof located in the apparatus with the cross-fins in and parallelto the flow of the circulating air for conditioning the circulating air,

a refrigerant. compressing and condensing'means operatively connected to said evaporating means, and thermostatic control means for said compressing means having a thermostat bulb mounted upon the lowermost return bend which is nearest the exit face of the evaporator structure having a setting to stop the compressing means when said bulb reaches a temperature just above the temperature at which frost and ice begin'to'form on said evaporating means. l i

3. Anair conditioning unit comprising a casingadapted to be mounted in a window of an enclosure to be conditioned with one portion of the casing projecting into the enclosure and another portion projecting out of the enclosure, means separating said casing into an evaporator compartment and a condenser compartments/first evaporator and a second evaporator located in said evaporator compartment, a first refrigerant liquefying means including a first condenser in said condenser compartment for sup plying liquid refrigerant to said first evaporator. a second refrigerant liquefying means including a second condenser in said condenser compartment for supplying liquid refrigerant to said second evaporator, and means for stopping said first refrigerant liquefying means in response to the temperature of said first evaporator falling below a predetermined value.

4. An air conditioning unit comprising a casing adapted to be mounted in a window of an enclosure to be conditioned with one portion of the casing projecting into the enclosure and another portion projecting out of the enclosure, means separating said casing into an evaporator compartment and a condenser compartment, a first evaporator and a second evaporator located in said evaporator compartment, a first refrigerant liquefying means including a first condenser in said condenser compartment for supplying liquid refrigerant to said first evaporator, a second refrigerant liquefying means including a second condenser in said condenser compartment for supplying liquid refrigerant to said second evaporator, means for stopping said first refrigerant liquefying means in response to the temperature of said first evaporator falling below a predetermined value, and means responsive to the temperature of the air in said enclosure for controlling said second refrigerant liquefying means.

5. An air conditioning unit comprising a casing adapted to be mounted in a window of an enclosure to beconditioned with one portion of the casing projecting into the enclosure and another portion projecting out of the enclosure, means separating said casing into an evaporator compartment and a condenser compartment, a first evaporator and a second evaporator located in said evaporator compartment, a first refrigerant liquefying means including a first condenser in said condenser compartment for supplying liquid refrigerant to said first evaporator, a second refrigerant liquefying means including a second condenser in said condenser compartment for supplying liquid refrigerant to said second evaporator, means for stopping said first refrigerant liquefying means in response to the temperature of said first evaporator falling below a predetermined value, means responsive to the temperature of the air in said enclosure for controlling said second refrigerant liquefying means,

and a continuously operating fan for circulating air over both of said evaporators in unison.

6. An air conditioning unit comprising a casing adapted to be mounted in a window of an enclosure to be conditioned with one portion of the casing projecting into the enclosure and another portion projecting out of the enclosure, means separating said casing into an evaporator compartment and a condenser compartment,

a first evaporator and a second evaporator located 10 in said evaporator compartment, a first refrigerant liquefying means including a first condenser in said condenser compartment for supplying liquid refrigerant to said first evaporator, a second refrigerant liquefying means including a second condenser in said condenser compartment for supplying liquid refrigerant to said second evaporator, means for stopping said first refrigerant liquefying means in response to the temperature of said first evaporator falling below a predetermined value, means responsive to the temperature of the air in said enclosure for controlling said second refrigerant liquefying means, and a common fan for circulating air to be conditioned over said evaporators, said evaporators being arranged in parallel relative to the circulatins air.

References Cited in the file of this patent UNITED STATES PAI'ENTS Number Name Date 1,967,420 Muffly July 24, 1934 1,988,319 King Jan. 15, 1935 1,988,552 Greever Jan. 22, 1935 2,049,413 Cannon Aug. 4, 1936 2,313,390 Newton Mar. 9, 1943 2,332,711 Gould Oct. 26, 1943 2,367,305 Newton Jan. 16, 1945 2,388,210 Hanson Oct. 30, 1945 2,451,682 Lund Oct. 19, 1948 2,499,411 Pennington Mar. 7, 1950 2,513,679 Ritter July 4, 1950

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