US2718762A - Low-temperature stabilized refrigerating system - Google Patents

Description

Sept. 1955 R. c. WEBBER 2,718,762

' LOW-TEMPERATURE STABILIZED REFRIGERATING SYSTEM Filed July 7, 1952 2 Sheets-Sheet 1 I N VEN TOR.

Sept. 27, 1955 R. c. WEBBER. 72,713,752

- LOW-TEMPERATURE STABILIZED REFRIGERATING SYSTEM Filed July '7, 1952 2 Sheets-Sheet 2 172 i I V I I I I 51 j 32 I a0 27 i5 5 3a 1 .34 I

4" g I 1126 I I 177 INVENTOR.

ATTOFIVZX United? States Patent LOW-TEMPERATURE STABILIZED REFRIGERATIN G SYSTEM Robert C. Webber, Indianapolis, Ind.

Application July 7, 1952, Serial No. 297,486

7 Claims. (Cl. 62-3) The present invention relates to low-temperature refrigerating systems, and is primarily concerned with means for stabilizing such systems. The primary object of the invention is to provide, in such a system, means for insuring the contemplated operation of a thermoresponsive throttling valve in the supply line to the evaporator, in spite of the fact that the evaporator is being operated to maintain temperature below the boiling point of the control fluid in the thermo-responsive valve.

A further object of the invention is to provide means capable of supplying heat, at rates variable in accordance with the demands upon the evaporator in such a system, to the. actuating fluid in such a thermo-responsive throttling valve.

Further objects of the invention will apear as the description proceeds.

To the accomplishment of the above and related objects, my invention may be embodied in the form illustrated in the accompanying drawings, attention being called to the fact, however, that the drawings are illustrative only, and that change may be made in the specific construction illustrated and described, so long as the scope of the appended claims is not violated.

Fig. 1 is a more or less diagrammatic illustration of a low-temperature refrigerating system embodying the present invention; and

Fig. 2 is a vertical section, upon an enlarged scale, through one form of thermo-responsive throttling valve, modified in accordance with the present invention.

Referring more particularly to the drawings, it will be seen that I have illustrated a generally conventional refrigerating system comprising a compressor 10, conduit means 11 connected to conduct compressed refrigerant from the compressor to an oil trap 12, conduit means 13 connected to conduct refrigerant from the trap 12 to a condenser 14, conduit means 15 connected to conduct refrigerant from the condenser to a receiver 16, conduit means 17 connected to conduct refrigerant from the receiver 16 to an evaporator 18, and conduit means 19 connected to conduct refrigerant from the evaporator to the compressor 10. In accordance with conventional practice, a thermo-responsive throttling valve 20 is connected in the conduit means 17; and I have shown a conventional drier 21 connected in the same conduit means just ahead of the valve 20. Preferably, a heat-exchanger 22 is connected in the conduit means 17 and in the conduit means 19 to bring refrigerant approaching the evaporator 18 and refrigerant leaving the evaporator 18, into heat-exchanging relation, as will be more fully explained hereinafter.

The valve 20 may take any one of a number of well known specific forms; but I have illustrated one preferred, commercially available form of throttling valve. The illustrated valve comprises a housing 23 in which is formed a controllable port 24 with which is operatively associated a throttling-type valve body 25 carried upon a yoke 26 for reciprocation in the direction of the axis of the port 24. A bellows 27 is so mounted in the housing 2,718,752 Patented Sept. 27, 1955 23 as to be subject to the pressure efiect of refrigerant on the outlet side of the port 24. A second bellows 28 is mounted in the housing in such a position as to be unaffected by the refrigerant pressure, with its interior in communication with a capillary tube 29 carrying, at its remote end, a feeler bulb 30 suitably secured, in heatexchanging relation, to the conduit means 19, and preferably in that portion 191 of said conduit means between the evaporator 18 and the heat-exchanger 22. The bellows 28 and the feeler bulb 30 and tube 29 are filled with a suitable low-boiling-point fluid such as, for instance, one of the Freons or ethane, nitrogen or helium.

The movable wall 31 of the bellows 28 bears upon a stem 32 which, in turn, bears upon a stem 33 which is fixed to a bell 34 secured to the movable end of the bellows 27, and to the yoke 26. Thus, the yoke 26 and the valve 25 are movable in response to actions of the bellows 27 and 28 under differential variations in the pressures exerted upon the respective bellows by the fluids in contact therewith. It is conventional to use such valves in systems generally of the type here under consideration.

The boiling point of Freon 22 is ordinarily considered to be 41 F. and the boiling point of Freon 13 is ordinarily considered to be F., these being the fluids customarily used in the bellows 28 and bulb 30. It is contemplated, in such a system, of course, that the temperature of refrigerant flowing through the section 191 of the conduit means 19 will be dependent upon the load demand at the evaporator 18-an increase in the demand resulting in an increase in the temperature of that refrigerant. Such an increase in temperature will,

of course, be sensed by the bulb 30, with the result that the fluid in the thermo-responsive system will be expanded to move the valve 25 away from its seat. Contemplated operation, however, is absolutely dependent upon maintenance of the gaseous phase of the fluid in the thermal system.

When evaporator temperatures are maintained below the boiling point of the fluid in the therr'no-responsive system under conditions of relatively heavy evaporator load, the rate of flow of refrigerant through the throttling or expansion valve 20, when combined with the relatively low temperature of the refrigerant moving through the conduit section 191, frequently results in such a reduction of temperature within and about the valve housing 23 as to result in liquefaction of some or all of the fluid in the system 2829-30; resulting, of course, in closure of the valve 25 and complete loss of control of the system.

The present invention is directed to the problem of overcoming that condition.

It is not diflicult, of course, to recognize the fact that liquefaction of the thermal fluid can be prevented by supplying heat, in required amounts, to the thermal system. Various experiments toward that end have been unsuccessfully tried, by introducing externally-controlled heating elements of one kind or another to supply the required heat. I have solved the problem by means which, in retrospect, appear extremely simple once the basic concept has been envisioned.

As is well understood, the refrigerant flowing in the section 171 of the conduit means 17 is at substantially room temperature; and the rate of fiow of refrigerant through that conduit section varies in accordance with the demand upon the evaporator 18. According to the present invention, I propose to bring the refrigerant flowing through the section 171 of conduit means 17 into heat-exchanging relation with the bellows 28; and, in the illustrated embodiment of the invention, I accomplish that end by wrapping a coil 172 of that conduit means about the valve housing 23 in the region of the bellows 28. The section 173 of that conduit means then extends to the core 221 of the heat-exchanger 22, whence the section 174 leads to a branch 175 entering the drier 21, whence refrigerant is conducted, by section 176, to and through the valve 20. Conduit section 177 leads from valve through coil 181 and coil 182 of the evaporator 18, whence section 191 leads the refrigerant to the shell of the heat-exchanger 22. Conduit section 192 returns the spent refrigerant to the compressor 10.

As has been stated, an increase in the load demand upon the evaporator 18 will increase the rate of flow of refrigerant through the valve 20, thereby tending to lower the temperature of the refrigerant on the outlet side of the port 24, thereby tending to cool the entire valve 20. Such an increase in the demand also increases the rate of flow of refrigerant through the conduit section 191 and tends to lower the temperature impressed upon the bulb 30. These factors tend to frost the valve and to liquefy the thermal fluid in the system 28-2940. In order to overcome these effects, therefore, heat should be supplied to the thermal system at a rate variable in accordance with the evaporation of refrigerant in the evaporator 18. Otherwise expressed, heat should be supplied to the thermal system at a rate variable in accordance with the rate of flow of refrigerant through the valve 20, evapo' rator 18, and associated conduit system. Obviously, the rate at which heat can be absorbed from the coil 172 into the thermal system at the bellows 28 will be dependent upon the rate at which relatively warm fluid flows through the coil 172; and since that rate will be directly proportional to the rate of evaporation of refrigerant in the coils 181 and 182, it will be seen that I have provided means which will inherently and automatically supply heat to the bellows 28 at a rate variable in accordance with the need for such heat at that point.

In the illustrated system, the evaporator 18 is shown as being rectangular, with coils 181 and 182, connected in series, arranged in association with two of the walls of the evaporator. Similar .coils (not shown) are arranged in association with the other two walls of the evaporator; said similar .coils being supplied through a branch 175a leading from the conduit section 174, a valve 201: in all respects similar to the valve 20, a conduit section 177a and conduit means 19a including a section 191a opening into the shell of the heat-exchanger 22. A coil 172a of the conduit section 173, following the coil 172 in series, is-wrapped about the casing of the valve 20a in the same manner in which the coil 172 is associated with the casing of the valve 20.

It will be immediately apparent that many other expedients are possible for establishing a heat-exchanging relation between the refrigerant flowing in the conduit means 17 and the thermal fluid in the system 28-29-30; but I presently believe the illustrated means to be optimum.

I claim as my invention:

1. A system of the class described including a compressor, a condenser, a receiver, an evaporator, conduit means establishing a closed circuit for refrigerant flow through the system, a valve connected in said conduit means ahead of said evaporator, thermo-responsive means for controlling said valve comprising means providing .a variable-volume chamber having a movable wall, means connecting said movable wall to actuate said valve, a feeler bulb responsive to the temperature of refrigerant leaving said evaporator, means establishing communication between the interior of said bulb and the interior of said variable-volume chamber, said bulb, chamber and communication-establishing means being filled with an expansible fluid, means establishing heat exchange relation bet-ween refrigerant flowing from said receiver toward said valve, and the fluid in said chamber,.and means establishing heat exchange relation between refrigerant flowing from said last named means toward said valve and refrigerant flowing from said evaporator toward said compressor 2. In a system of the class described, a compressor, a condenser, a first conduit means connected to conduct refrigerant from said compressor to said condenser, a receiver, a second conduit means connected to conduct refrigerant from said condenser to said receiver, and evaporator, a third conduit means connected to conduct refrigerant from said receiver to said evaporator, a valve connected in said third conduit means to control flow of refrigerant therethrough, a fourth conduit means connected to conduct refrigerant from said evaporator to said compressor, means for controlling the position of said valve comprising a variable-volume chamber having a movable wall, means connecting said valve to move in response to movements of said movable Wall, a feeler bulb mounted in heat-exchanging relation to said fourth conduit means, the interior of said bulb being in communication with the interior of said chamber and said bulb and chamber being filled with a fluid having a boiling point below normal atmospheric temperatures but above temperatures desired to be attained at said evaporator, a portion of said third conduit means being arranged in heat-exchanging relation with said chamber, and a further portion of said third conduit means, between said firstnamed portion thereof and said valve, being arranged in heat exchange relation with a portion of said fourth conduit means.

3. In a system of the class described, a compressor, a condenser, a first conduit means connected to conduct refrigerant from said compressor to said condenser, a receiver, a second conduit means connected to conduct refrigerant from said condenser to said receiver, an evaporator, a third conduit means connected to conduct refrigerant from said receiver to said evaporator, a valve connected in said third conduit means to control flow of refrigerant therethrough, a fourth conduit means connected to conduct refrigerant from said evaporator to said compressor, means for controlling the position of said valve comprising a variable-volume chamber having a movable wall, means connecting said valve to move in response to movements of said movable wall, a feeler bulb mounted in heat-exchanging relation to said fourth conduit means, the interior of said bulb being in communication with the interior of said chamber and said bulb and chamber being filled wtih a fluid having a boiling point below normal atmospheric temperatures but above temperatures desired to be attained at said evaporator, a portion of said third conduit means between said receiver and said valve being arranged in heat-exchanging relation with said chamber, and a further portion of said third conduit means, between said first-named portion and said valve, being arranged in heat-exchanging relation with a portion of said fourth conduit means.

4. In a system of the class described, a compressor, a condenser, a first conduit means connected to conduct refrigerant from said compressor to said condenser, a receiver, a second conduit means connected to conduct refrigerant from said condenser to said receiver, an evaporator, a third conduit means connected to conduct refrigerant from said receiver to said evaporator, a valve connected in said third conduit means to control flow of refrigerant therethrough, a fourth conduit means connected to conduct refrigerant from said evaporator to said compressor, a heat exchanger connected in said third conduit means between said receiver and said valve and connected in said fourth conduit means between said evaporator and said compressor, means for controlling the position of said valve comprising a variable-volume chamber having a movable wall, means connecting said valve to move in response to movements of said movable wall, a feeler bulb mounted in heat-exchanging relation to said fourth conduit means at a point between said evaporator and said heat exchanger, the interior of said bulb being in communication with the interior of said chamber and said bulb and chamber being filled with a fluid having a boiling point below normal atmospheric temperatures but above temperatures desired to be attained at said evaporator, a portion of said third conduit means between said receiver and said heat exchanger being arranged in heat-exchanging relation with said chamber.

5. In a low temperature refrigerating system which includes a thermostatically-controlled valve controlling flow from the receiver to the evaporator, said valve being dominated by an expansible fluid subject to the temperature of refrigerant fluid flowing from the evaporator toward the compressor and acting upon a movable chamber wall mechanically connected to said valve, the invention which comprises means for impressing upon the fluid in said chamber the temperature of refrigerant flowing from the receiver toward said valve, and means for bringing the refrigerant flowing toward said valve subsequently into heat-exchange relation with refrigerant flowing from said evaporator toward said compressor.

6. In a system of the class described, a compressor,.

a condenser, a first conduit means connected to conduct refrigerant from said compressor to said condenser, a receiver, a second conduit means connected to conduct refrigerant from said condenser to said receiver, an evaporator, a third conduit means connected to conduct refrigerant from said receiver to said evaporator, a valve connected in said third conduit means to control flow of refrigerant therethrough, a fourth conduit means connected to conduct refrigerant from said evaporator to said compressor, means for controlling the position of said valve comprising an expansible bellows mechanically connected to said valve, and filled with an expansible fluid, means for impressing upon such fluid the efiect of temperature changes in said fourth conduit means, and a casing enclosing said valve and said bellows, a portion of said third conduit means being wrapped about said casing in the region occupied by said bellows, and a portion of said third conduit means between the wrapped portion thereof and said valve being arranged in heatexchange relation with a portion of said fourth conduit means.

7. In a system of the class described, a compressor, a condenser, a first conduit means connected to conduct refrigerant from said compressor to said condenser, a receiver, a second conduit means connected to conduct refrigerant from said condenser to said receiver, an evaporator, a third conduit means connected to conduct refrigerant from said receiver to said evaporator, a valve connected in said third conduit means to control flow of refrigerant therethrough, a fourth conduit means connected to conduct refrigerant from said evaporator to said compressor, means for controlling the position of said valve comprising an expansible bellows mechanically connected to said valve and filled with an expansible fluid, means for impressing upon such fluid the elfect of temperature changes in said fourth conduit means, and a casing enclosing said valve and said bellows, a portion of said third conduit means between said receiver and said valve being wrapped about said casing in the region occupied by said bellows.

References Cited in the file of this patent UNITED STATES PATENTS 2,077,865 Wile Apr. 20, 1937 2,205,166 Dube June 18, 1940 2,228,834 Kramer Jan. 14, 1941 2,326,093 Carter Aug. 3, 1943 2,391,030 Morrison Dec. 18, 1945 2,463,892 Martin Mar. 8, 1949 2,471,448 Platon May 31, 1949 2,497,677 Lathrop Feb. 14, 1950

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