US2487012A - Refrigeration system - Google Patents

Description

Nov. 1, 1949 E. w. z EARFoss, JR 2,487,012

REFRIGERATION SYSTEM Filed Jan. 8, 1946 INVENTOR.

Patented Nov. 1, 1949 REFRIGERATION SYSTEM Elmer W. Zeari'oss, Jr., Philadelphia, Pa., assignor, by mesne assignments, to Philco Corporation,

Philadelphia, vania Pa., a corporation of Pennsyl- Appllcatlon January 8, 1946, Serial No. 639,720

6 Claims. (Cl. 62-115) The present invention relates to refrigeration systems and particularly to the control of refrigerant flow between the high pressure side and the low pressure side of a refrigeration system of the capillary-tube restriction type.

As is commonly known in the art, systems of the general type above referred to are designed for optimum efficiency when operating under specific conditions. For example, a system may be designed to operate at its best when the evaporator temperature is +10 F., and the room temperature is 90 F. In such a system, the capillary tube is so constructed that the flow of refrigerant therethrough is exactly controlled (by the difference in pressure at the opposite ends of the tube) to prevent an excessive amount of gas from passing into the evaporator and to prevent an undue amount of liquid from accumulating in the condenser, when the conditions are precisely as noted. However, these conditions are most unstable, due to the fact that the evaporator and the condenser are subject, respectively, to variations in heat-load and to variations in thermo-gradient. These variations in turn cause a change in pressure which deleteriously afiects the flow of refrigerant and accordingly lessens the efficiency of the system.

Thus, if the evaporator temperature is reduced, a corresponding reduction in evaporator pressure will follow-and therefore less refrigerant will be' pumped by the compressor so that an excessive amount of gas, still containing heat of vaporization, will be forced through the capillary and circulated throughout the system, accordingly reducing its efliciency. Likewise, the efllciency of the system will be impaired by the circulation of an excessive amount of heat laden gas, if the room temperature rises to a point where the condensing pressure becomes so aflected that the refrigerant, discharged by the compressor into the condenser, can not be fully condensed by the time it leaves the latter to enter the capillary.

A rise in evaporator temperature or a drop in room temperature, will so affect the condensation process that liquified refrigerant will be available in an amount greater than the amount which ;he capillary will allow to pass into the evaporator. Consequently the liquified refrigerant will sack up into the condenser reducing its effective :ondensing surface and accordingly reducing the emciency of the system.

In ordinary capillary system, no provision is rnade to compensate for temperature variations as Jutllned above, since, in such a system, the :apillary restriction is fixed and the flow of refrigerant is directly subject to the differences in pressures betweenthe high side and low side of the system. However, attempts have heretofore been made to control the flow-retarding effect of a capillary tube by abstracting heat therefrom in response to variations in conditions which effect pressure changes within the refrigeration system. For that purpose, it has been suggested to provide the system with an auxiliary capillary tube which forms apart of a liquid refrigerant receiving chamber, and which terminates with a portion arranged in heat exchange relation with the discharging end of the main capillary tube. Such an arrangement may function effectively so long as liquid refrigerant passes through the auxiliary capillary tube, but as soon as gas starts flowing through such auxiliary tube, then the system operates in the same manner as it would operate with a single capillary tube. Consequently such known arrangements are subject to the same objections as hereinabove mentioned because in those arrangements the detrimental effects of a single capillary tube are merely transferred to a second capillary tube.

It is therefore, the primary object of this invention to overcome the above mentioned objections and to assure optimum operation of a system of the type referred to, by controlling the flow of refrigerant not only through the main capillary tube but also through the auxiliary capillary tube.

It is another object of the invention to provide an arrangement whereby heat may be abstracted from the auxiliary capillary tube, which itself is utilized for the purpose of abstracting heat from the main capillary tube of the refrigeration system, so that the flow of refrigerant through the latter may be automatically varied in response to temperature-pressure changes in the system. The abstraction of heat from the auxiliary capillary tube results in cooling the refrigerant passing therethrough and thus assures the presence of sufficient cool refrigerant in an expanderportion of said tube for the purpose above specified.

Another and more specific object of the invention resides in the provision of a novel arrangement and interrelationship of elements within a refrigerating system employing a main capillary tube and a pilot" capillary tube, such arrangement and relationship of elements resulting in greatly increasing the operational efl'iciency of the system for any given evaporator temperature and in ensuring maintenance of optimum efiiciency of the system throughout a wide range of evaporator temperatures.

Moreover, the invention is particularly characterized by the inclusion of an expander within a refrigerating system of the kind employing two capillarly tubes, that is, a main capillary tube to tain amount of flash gas with the liquid refrigerant being supplied to the evaporator I. In the system illustrated in the drawing, the amount ofretard the flow of refrigerant from the condenser to the evaporator and an auxiliarly capillary tube to control the flow retarding effect of the main capillarly tube. This expander is associated with the two capillary tubes in such a manner that each are kept physically independent from the other so that the refrigerant circulating through said expander is the sole influence on either capillary tube. Such an. arrangement makes it possible to obtain practically instantaneous control of the refrigerant flow through the main capillary tube.

These and other objects of the invention will be apparent from the following description based upon the accompanying drawing, the single figure of which diagrammatically illustrates a possible embodiment of a refrigeration system constructed in accordance with this invention.

In the drawing, the invention has been shown as applied to refrigerating apparatus of the compression type, but it is to be understood that the invention. is applicable to other types of refrigcrating apparatus in which a volatile fluid may be evaporated upon absorbing heat and condensed upon having heat abstracted therefrom.

As represented in the drawing, the system basically comprises an evaporator i and a condensing unit, the latter including a motor compressor 2 and a condenser 3. The evaporator I: is associated with a refrigerator compartment 4 so that the-liquid refrigerant, as it evaporates in'said evaporator, may absorb heat from the air -\ivith'ir'i such compartment to cool the same. The gas forming in the evaporator due to the absorptiOllfOf heat during the vaporization process, is drawn through a suction line 5 into the compressor 2. There, the gas-is compressed and discharged through a conduit 6 into the condenser 3 which is flash gas is controlled to vary the restrictive effect of the capillary tube so that the flow of refrigerant therethrough may be automatically regulated in response to changes in temperaturepressureconditions within the system. For that purpose, a portion l6b of the capillary tube I6 is disposed for heat exchange relation with an expander 20, the outlet end 2| of which discharges into the evaporator inlet Ill. The inlet end 22 of the expander communicates with the outlet end of an auxiliary or "pilot" capillary tube 23, the inlet end of which communicates with the liquid line at a point ahead of and at a level slightly higher than the inlet of the main capillary tube iii. In practice, the inlet end of the auxiliary capillary tube may be suitably connected with the top side of the filter l5, as indicated, at 2 4, in the drawing. The auxiliary capillary tube 23 is so designed that when the system is operating at maximum load, said tube will pass approximately one-third of the total amount of refrigerant supplied to the evaporator, and therefore the restriction of the auxiliary capillary tube should be correspondingly higher than the restriction of the main capillary tube i6.

Moreover, in accordance with the present invention, the auxiliary capillary tube 23 is so constructed that the refrigerant passing therethrough is placed in heat exchange relation with refrigerant emerging from said tube 23. For that purpose, said tube 23 has a port on 23a disposed for heat exchanged relation with the expander 20, so that the refrigerant passing through the auxiliary capillary tube is in heat exchanged relation with the refrigerant which has passed through said tube and discharged into the ex pander.

Operation of conventional systems at high evaporating pressure or at low con en in pressure, normally results in blocking the condenser.

exposed to room air so that heat may be abstractbecause the restriction of the ordinary capillary ed from the compressed: refrigerant to condense the same back to liquid state-From the condenser, the liquid refrigerant flows to the evaporator through conduit means in the manner to be hereso and the source of energy 8. A spring i 3 is pro vided to o pose the force exerted by the bellows i0. and is adjustable by means of a knob it so that the avera e evaporator temperature may be varied; within limits, at the will of the user.

In the svstem as shown in the drawing, liquid refri erant from the conden er 3 passes first throu h a fi ter i5 and then through a main capillarlv tube I6. This capillary tube is connected with the outlet i? of the filter i 5 and discharges into the inlet i! of the eva orator I. As is customary. a portion Ilia of the capi lary tube It is arran ed in heat exchanged relation with a portion 5a of the suction conduit 5.

tube would prevent passage of the limiid at a rate commensurable with the rate at which the liquid condenses, so that the liquid would then back up into the condenser. However. this Working of +he condenser is overcome by the provision of the auxiliary capillary tube 23, because the liquid (which would ordinari y back up in the con denser), passes through said auxiliary capillary tube and through the expander Ml. In passing through the expander 20, the liquid removes flash gas and. therefore, subcools the refrigerant in port on l6b of the main capillary tube l6 and in a portion 23a of the auxiliary capillary tubr 23. thereby reducing the restrictive effect of both 30 tubes so that more refrigerant passes into the evaporator when the system is operating at high evaporating pressure due to a rise in evaporator temperature, or when the system is operating at low condensing pressure due to a drop in room temperature. It is pointed out that when the svstem operates under these conditions, the arran ement of portion 23a in heat exchange relation with the expander, assures that liquid. will be discharged into the expander in'quantit es sufflcient to provide adequate heat-exchan e with the refrigerant passing through both the auxiliary and the main capillary tubes. It will be understood that this feature results from the fact that refrigerant which emerges from the auxiliary capillary tube 23, expands upon entering the expander 20 and. thus, produces a cooling effect on the refrigerant passing through portion 23a of the auxiliary capillary tube. Therefore, the amount of liquid refrigerant passed by said tube is greater than the amount which the tube would normally allow to pass.

Operation of conventional systems at low evaporating pressure or at high condensing pressure normally results in gas blowing through to the evaporator. because then less refrigerant would be condensed and therefore less liquid would be available at the entrance of the ordinary capillary tube, so that the available liquid would soon be exhausted and an excessive amount of gas would pass through said capillary tube into the evaporator. However, the passage of an excessive amount of gas through the main capillary' tube I6 is prevented by the provision of the auxiliary capillary tube 23, because the latter will then deliver saturated gaseous refrigerant, to the expander. Thus the refrigerant passing through the expander will have but slight cooling effect on the refrigerant pass ng through portion I 6b of the main capillary tube IGand through portion23a on auxiliary capillary tube 23 resulting n increasing the restrictive effect of said main ca illary tube and therefore preventing a rush of l quid therethrough and an exhaustion of the liquid at the entrance thereof. In this manner, the quantity of liquid refri erant supplied to the .evaporator is substantially the same as the qu ntity pumped by the compressor, so that the efli iency of the system is effectively maintained. The fact that the restrictive effect of the auxiliary capillary tube 23 is also controlled when the system is operating at low evaporating pressure or at higlr con ensing pres ure. is an essent al factor in establishing and maintaining the operat o al ef iciency of the svstem. Th s result is obtainable because, in accordance with the invention. the flow of gaseous refrigerant. which normally would impair the operation of the system. is highly restricted when the s stem is sub jected to low evaporat or to high condensing pressure conditions. This feature of the invention results from the fact that by lacing the refrigerant, passing through the auxiliary capillarv tube, in heat exchange relat on with refri erant emerg ng from sa d tube. it is possible to provide the system with a high restriction and to reduce the restrictive effect in response to chan es in temperature-pressure conditions within the s stem so that, for any given condit on. the amount of gas discharged into the,

evaporator is efiectivelv decreased. This hi h restriction is particularly advantageous in that it revents an excessive amount of gas from ent ring the evaporator when the system is o erating at low evaporating pressure due to a d op in eva o tor tem erature. or when the s s em is operating at high condensing pressure due to a rise in room temperature. The gas, wh ch is held back due to the high restriction in t e svstem, accumulates at the condenser and thus tends to increase the temperature of the refrigerant and. therefore. to raise the condensing ressure. As a result, the condensation process is re nlt a ed sooner than if the gas were allowed to blow through the evaporator in the usual manner. Thus, the proper balance between head and suction pressures is quickly restored so that loss in the efficiency of the system is minimized.

It is particularly pointed out that the overall efficiency of the system depends upon the perby placing the portion 23a thereof in heat exchange relation with the beginning portion 20a of the expander 20 and by placing the portion IGb of the main capillary tube in heat exchange relation with the remaining portion 20b of said expander. In this manner, the presence of liquid refrigerant within the expander in a quantity suflicient to effect heat exchange with the refrigerant passing through the main capillary tube is ensured, particularly because the refrigerant tube from the auxiliary capillary tube is effectively cooled at the beginning of the expander, the cool refrigerant being subsequently made available in the remaining portion of the expander with which the main capillary tube is in heat exchange relation.

It will be appreciated that the vaporation process which takes place in the expander 20 results in subcoolin the refrigerant flowing through both capillary tubes. This vaporization process occurs particularl when the conditions within the system are such that the condenser would tend to block up with condensed refrigerant. When such conditions occur, the mentioned vaporization process is initiated and continues until the liquid level in the condenser falls below the entrance to the auxiliary capillary tube. In actuality this function of the system is periodic and varies only in intensity to accommodate various load conditions;

From the foregoing, it will be understood that a refrigeration system constructed in accordance with the invention will adapt itself to varying temperature-pressure conditions so that the proper flow of refrigerant, for any given condition, is automatically initiated and effectively maintained throughout the system. Moreover, the system is capable of quickly adjusting the refrigerant flow to a change in suction pressure or in head pressure or both, when variations in evaporator or in room temperature, have affected such pressures. The quick adjustment of the refrigerant flow results particularly from controlling the restrictive effect of the auxiliary or pilot capillary tube as well as the restrictive effect of the main capillary tube. This characteristic feature of the invention assures operation of the system at optimum efficiency over a wide temperature range and therefore minimizes the possibilities of refrigeration failures, in the system, due to changes in temperature-pressure conditions.

It is to be understood that modifications may be made in the construction of the system without departing from the spirit of the invention. Therefore, the invention is not limited to what is shown in thedrawing and described in the specification, but is subject only to such limitations as are imposed by the prior art or are particularly indicated in the ap nded claims.

I claim:

1. In a refrigeration system, an evaporator, a condensing unit, and a pair of conduits each conveying refrigerant from the condensing unit to the evaporator, one of said conduits having an expander portion arranged in heat exchange relation with another portion of said one conduit.

2. In a refrigeration system, an evaporator, a condensing unit, and a pair of conduits each conveying refrigerant from the condensing unit to the evaporator, one of said conduits having an expander portion arranged in heat exchange relation with another portion of said one conduit, and with a portion of the other of said conduits.

3. In a refrigeration system, an evaporator, a condensing unit, a main and an auxiliary conduit each conveying refrigerant from the condensing unit to the evaporator, the auxiliary conduit having an expander portion disposed for heat exchange with another portion of said auxiliary conduit, and the main conduit having a portion arranged for heat exchange with said expander portion of the auxiliary conduit.

4. In a refrigeration system, an evaporator, a condensing unit, and means for conveying refrigerant from the condensing unit to the evaporator, said means including an expander and a pair of capillary tubes, one of said tubes communicating with the evaporator through the expander and disposed for heat exchange relation with the latter, and the other of said tubes communicating directly with the evaporator and also disposed for heat exchange relation with the expander.

5. In a refrigeration system, an evaporator, a condensing unit, and means for conveying refrigerant from the condensing unit to the evaporator, said means including an expander 8. having its outlet arranged for communication with the inlet of the evaporator, a capillary tube having its outlet arranged for communicationwith the inlet of the expander and provided with a portion disposed for heat exchange relation with the beginning portion of said expander, and another capillary tube having its outlet arranged for communication with the inlet of the evaporator and provided with a portion disposed for heat exchange relation with the remaining portion of the expander.

6. In a refrigeration system, an evaporator, a condensing unit, and a pair of conduits each adapted to pass and to restrict the flow of refrigerant from the condensing unit to'the evaporator, one of said conduits terminating with an expander portion discharging into the evaporator and arranged in heat-exchange relationship with a portion of each conduit.

ELMER W. ZEARFOSS, JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,183,343 Alsing Dec. 12, 1939 2,183,346 Buchanan Dec. 12, 1939 2,404,010 Urban July 16,1946

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