US2133959A - Refrigerating apparatus - Google Patents

Description

25, 1938. L. B. M. BUCHANAN 2,133 959 REFRIGERATING APPARATUS Filed Octa1, 1956 s INVENTOR 1 3;, as I Lgsu: B.M.Bucnn-n-.

a I i 2 v ATTOR Y Patented Qct. 25, 1938 UNITED STATES I signor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa.,

tion of Pennsylvania Application October 31,

11 Claims.

My invention relates to apparatus for refrigerating different zones of a refrigerator to predetermined temperatures, and it has for an object to provide improved apparatus of this kind.

A further object of my invention is to provide improved two-temperature refrigerating apparatus which will be reliable in operation and inexpensive to produce.

A still further object of the invention is to provide improved means for varying the effective cooling area of an evaporator by controlling the operation of a single valve from different portions of the evaporator.

A still further object of my invention is to provide improved means for selectively efiecting refrigeration of different zones of a refrigerator.

These and other objects are effected by my invention as will be apparent from the following description and claims, taken in connection with the accompanying drawing forming a part of this application, in which:

Fig. 1 is a diagrammatic view of a two temperature refrigerating machine constructed in.

accordance with my invention; and,

Fig. 2 is a sectional view, somewhat diagrammatic, of an expansion valve employed in the apparatus shown in Fig. 1.

Reference will now be had to the drawing wherein I disclose a refrigerator cabinet structure l0 having relatively low and high temperature chambers ll and I2 formed therein and cooled by respective evaporator elements l3 and I4. Refrigerant is circulated through the evaporators l3 and I4 by a condensing unit, generally indicated at l5, and including a compressor It, a motor H for driving the compressor, and a condenser I8, the latter being cooled in any suitable manner, such as, for example, by a fan l9. A liquid refrigerant reservoir, shown at 2|, may be connected to the condenser l8 for storing refrigerant condensed thereby. I Condensed refrigerant is conveyed to the evaporators l3 and I4 from the reservoir 2| by means of a conduit 22. Refrigerant vaporized in the evaporators l3 and I4 passes to the compressor l6 through a conduit 23. A device.- preferably a thermostatic expansion valve is arranged in the liquid supply conduit 22' for controlling the flow of condensed refrigerantto the evaporators l3 and i4 and for reducing the pressure of the refrigerant. The valve 24 will be referred to more in detail hereinafter. The refrigerating apparatus described in the foregoing is of the compressor-condenser-expander type.

PATE

NT OFFICE" a corpora- 1936, Serial No. 108,516

Liquid refrigerant, passed by the valve 24, enters a header 25 provided in the upper portion of the evaporator l3. A conduit 26 provides communication between the header 25 and an inlet header 21 formed in the evaporator |4.. The suction conduit 23 connects with an outlet header 28 formed in the evaporator l4. As shown, the evaporator l3 may include shelf portions 29 for supporting trays 3! for fluid to be congealed. The evaporator l3 operates, therefore, to congeal liquid and to reduce the temperature of the air in the chamber H to a relatively low value. The evaporator l4 may be provided with fins 32 as shown, and cools the air in the chamber l2 to a value somewhat higher than the temperature of the air in the chamber II.

From the foregoing, it will be apparent that refrigerant delivered to the header 25 will fill the evaporator l3; before flowing through .the conduit 26 to the evaporator l4. The evaporator l3, therefore, receives refrigerant in preference to the evaporator l4.

In accordance with my invention, condensed refrigerant is confined to the evaporator I3 when cooling of the chamber II is effected and, when the chamber I2 is being cooled, liquidrefrigerant substantially fills both evaporators I3 and I4. The means for obtaining this operation will now be described.

While other suitable forms of devices 24 may be employed, I prefer to employ an expansion valve including a valve structure which is actuated in response to the superheat of the vaporized refrigerant. Such-an expansion valve is shown in Fig. 2 and includes a casing 33 having a valve seat 34 formed therein. A valve member 35 cooperates with the valve seat and is actuated by a diaphragm. member 36. The casing 33 is divided into two chambers 31 and 38 which communicate, respectively, with the liquid supply conduit 22 and with the evaporator header 25.

The valve casing 33 defines a chamber 39 above the diaphragm 36 which is in communicationwith a conduit 4| having first and second bulbs or reservoirs and 43 connected therein. A suitable volatile fluid, preferably, the same as the fluid employed as a refrigerant 'in the system, is contained within the bulbs 421and: 43, eondui and the. chamber 39. 1= rn bulbsezyandf disposed in heat transfer relation-withthe re, spec'tive conduits 26v and 23,..adjacentto their. points of connection with the evaporators .13 and i4.

The diaphragm issubjected upon its top side to the pressure of the fluid in the chamber 39,

which pressure is a function of .the temperature of the liquid in the bulb 42 or 43. The pressure which is effective lsthat corresponding to the temperature of the lower temperature bulb. This condition prevails at all times due to the fact that avolatile fluid is employed, and, therefore, a higher temperature at the warmer bulb will not raise the pressure in-the chamber 39 and conduit 4| as the fluid vaporized by the higher temperature is immediately condensed in the lower temperature bulb. Accordingly, the pressure is determined by the lowest temperature :6 which the fluid is subjected. The bulb 42 is,

preferably, disposed in the low temperature chamber H and in contact with the evaporator discharge conduit 26 so that it operates at lower temperature than the bulb 43, except during certain periods as described hereinafter.

The underside of the. diaphragm 36 is subjected to the pressure of refrigerant in the evaporator 43 or 14, which pressure prevails in the chamber 38 of the valve 24. A biasing means, such as a spring 44, biases the diaphragm 36 and valve 35 upwardly and may determine the value of the superheat to which the valve responds. Preferably, the spring 44 is adjustable by any well known means (not shown) whereby the value of the superheat maintained may be varied.

During operation with the bulb 42 at a lower temperature than bulb 43, only the evaporator l3 receives condensed refrigerant ,because the valve 24 responds to the superheat of the refrigerant in conduit 26 and controls the supply of condensed refrigerant to maintain a predetermined amount of superheat, for example, 10,-

in the gas passing from the evaporator l3 to the evaporator l4 through the conduit 26. At this time some slight cooling of the evaporator 14 may be effected as the gas passing therethrough to the suction conduit 23 abstracts some heat from the evaporator l4 as the gas is further superheated. The refrigerant charge in the system is such that a substantial amount of liquid refrigerant is present in the reservoir 2| during the periods when evaporation is effected in the evaporator l3 alone.

In accordance with my invention, refrigeration of the chamber I2 is effected by.transferring the point at which superheat is controlled to the conduit 23. Accordingly, the bulb 43 is rendered efiective to determine the pressure in the chamber 39 of the valve 24. This may be effected by heating the bulb 42 to a temperature slightly in excess of the temperature of the bulb 43. Preferably, an electrical heater 45 is disposed in heat transfer relation with the bulb 42 for this purpose.

As the temperature of the fluid in the bulb 42 is heated by the heater 45, the pressure in the chamber 39 rises. Accordingly, the valve 35 is moved away from its seat 34 and refrigerant fiows from the reservoir 2| through the valve 24 to the header 25 and overflows into conduit 26- and substantially fills the evaporator l4.- The superheat present in the gas is under control of the bulb 43 and the valve 24 operates to maintain the gas passing through the conduit 23 in a superheated condition. I

As the evaporator l4 operates at pressure and temperature values higher than the values at which vaporization is effected in the evaporator l3, vaporization of refrigerant in the evaporator 43 substantially ceases, during refrigeration of the evaporator l4. It will be understood that the evaporator I3 is filled with liquid refrigerant which provides a seal for preventing gas generated in the expansion valve 24 or in the evaporator l4 from entering and condensing in the low temperature evaporator l3, which action would add heat to the latter.

Operation of the condensing unit [5 and the heater 42 is preferably automatically controlled in accordance with temperature conditions within the chambers H and i2. As shown in Fig. 1, a thermostat 46 of the gas type controls operation of the condensing unit IS in accordance with the temperature of the evaporator l3 and a thermostat 41, shown by way of example as a bimetal strip, controls the condensing unit I5 and the heater 45 in accordance with the temperature of the air in the chamber I2.

The thermostat 46 preferably includes a bellows 48 connected by a tube 49 to'the bulb St, the

latter being disposed in heat transfer relation with the evaporator [3. As is well understood, a volatile fluid is contained in the bulb 5l,'tube 49 and bellows 46 whereby the latter expands and contracts as the temperature of the evaporator l3 and bulb 5| increases and decreases. The bellows 48 actuates a switch 52 in such manner that it is closed and opened in response to predetermined high and low temperatures of the evaporator iii. The thermostat 46 is shown, for the sake of clearness, in its simplest form and it is to be understood that certain refinements. such as, for example, snap-acting switch mechanisms have been omitted.

The source of power for the compressor motor I! and the heater 45 is represented by line conductors L1 and L2. The switch 52 is connected in series in a circuit including line conductor Ll, the motor H, a conductor 53, the switch 52 and line conductor L2. As the temperature of the evaporator l3 increases to a predetermined value, the switch 52 is closed by the expanded bellows 48 and initiates operation of the motor I! and, conversely, as the temperature of the evaporator l3 decreases to a predetermined value, the switch 52 is opened by the bellows 46 and terminates operation of the motor l'l.

Thethermostat 41 includes a movable bimetallic member 54 which engages stationary contacts 55 and 56 as the temperature of the air in the chamber [2 increases to a predetermined value and which is disengaged from said contacts 55 and 56 when the temperature of the air decreases to a predetermined value. The movable member 54 is connected to the line conductor L2 and the contact 55 is connected to the conductor 53 for controlling energization of the motor H. The contact 56 is connected to one terminal of the heater 45; the other terminal of which is connected to line conductor L1. Accordingly, engagement of the movable member 54 with contacts 55 and 56 in response to a predetermined temperature within the chamber l2 effects energization of the compressor motor H and the heater 45.

Operation p As shown in the drawing, the temperatures prevailing within the chambers H and I2 are below the values at which their respective thermostats 46 and 41 operate to effect operation of the condensing unit l5. Assume that the temperature of the evaporator l3 increases to the value at which the thermostat 46 closes. The motor I! is energized and the condensing unit l5 operates to supply refrigerant to the evaporator l3. As the heater is deenergized, the bulb "is at a lower temperature than the bulb 43 and, as described heretofore, the device 24 is controlled to maintain the proper superheat in the refrigerant vaporized in the evaporator l3. Accordingly, only gaseous refrigerant circulates through the evaporator I4, the cooling effect of which is slight. As the temperature of the evaporator I3 is depressed to the desired value, the thermostat 46 operates to terminate operation of the condensing unit l5.

Assume a rise in temperature of the air in the chamber i2, the thermostat 41 operates to engage the movable member 54 with contacts 55 and 56, whereby the condensing unit I is operated and the heater 45 is energized. Therefore, the bulb 43 operates at a lower temperature than the heated bulb 42 and as described heretofore, the superheat of the vaporized refrigerant is controlled by the device 24 and bulb 43. During this operation, the device 24 admits sufficient refrigerant to fill a substantial portion of the evaporator l4.

Refrigerant is vaporized in the evaporator l4 for cooling the air in the chamber l2, the pressure of the vaporized refrigerant being at a higher value than when the evaporator I3 iscooled. The evaporator l3 and conduit 26 are filled with liquid refrigerant at this time, whereby a seal is defined forpreventing refrigerant vaporized in the evaporator M from condensing in the evaporator l3. Accordingly, undesirable heating of the evaporator I3 is prevented.

As the thermostat 41 moves to its openposition in response to a predetermined low temperature of the air in the chamber l2, the condensing unit I5 is stopped and the heater 45 is deenergized. In the event that both thermostats 48 and 41 close in response to cooling demands by the chambers H and I2, the evaporator l4 in chamber 12 is given preference due to the fact that heater 45 is energized under this condition, and therefore the superheat of the vaporized refrigerant is controlled by bulb 43. It will be understood that the evaporator l3 may be given preference over the evaporator l4 when both require cooling in accordance with my invention.

From the foregoing it will be apparent that the device 24 functions as a thermostatic expansion valve with means for controlling the superheat of the vaporized refrigerant at a plurality of selected locations along the evaporator structure. Accordingly, the effective area of an evaporator, or the portion thereof in which vaporization is effected, may be controlled in accordance with my invention. In this connection it will'be understood that the inventionis not limitedto two temperature refrigerators but may be applied to single evaporators to control the effective cooling area thereof.

It will be understood that other forms of refrigerant condensing units and control elements per so may be employed in my improved refrigerating system without departing from the spirit of the invention.

While I have shown my invention in but one.

claims.

What I claim is:

1. In apparatus for refrigerating first and second zones, the combination of first and second or as are specifically set forth in the appended spectively, means for supplying refrigerant to the evaporators, a device common to both evaporators for controlling the'admission of refrigerant thereto, first and second temperature responsive elements associated with the respective evaporators for controlling said device, and means for controlling the operation of the refrigerant supply meansand for selecting the element which is to control the device.

3. In apparatus for refrigerating first and sec-- ond zones, the combination of first and second evaporators disposed for cooling said zones, respectively, means for supplying refrigerant to the evaporators, a device common to both evaporators for selectively controlling the vaporization of refrigerant therein, first and second temperature responsive'elements associated with the respective evaporators for controlling said device, and means responsive to temperatures within the respective zones for selecting the element which is to control the device.

4. In refrigerating apparatus, the combination of first and second evaporating elements, means for supplying condensed refrigerant to said elements in such manner that it flows into the first element in preference to the second element, a device for regulating the flow of refrigerant to the elements, first and second means responsive respectively to the temperature of the refrigerant in the evaporating elements for controlling said device, and means for selectively rendering the first or second temperaturev responsive means operative to control the device.

5. In refrigerating apparatus, the combination offirst and second evaporators, means for condensing refrigerant for the evaporators, means .for conveying the condensed refrigerant to the controlling the fiow of condensed refrigerant to the evaporators and means for selecting the temperature responsive means which is to control the flow of condensed refrigerant.

6; In refrigerating apparatus, the combination of first and second evaporators, means for com densing refrigerant for the evaporators, means for conveying the condensed refrigerant to the first evaporator, a conduit for conveying refrigerant from the first evaporator to the second evaporator, a second conduit for conveying refrigerant vaporized inthe evaporators from the second evaporator to the refrigerant condensing means, a valve for controlling thefiow of condensed refrigerant conveyed by said refrigerant conveying means, means responsive to the pressure ofthe refrigerant in the evaporators for actuating said valve in one direction, temperature responsive means for actuating the valve in another direction in opposition to the pressure responsive means, and means for selectively rendering the temperature responsive means responsive to the temperature of the refrigerant discharged from the first evaporator or to the temperature of the refrigerant discharged from the secondevaporator.

'7. In refrigerating apparatus, the combination of means defining first and second chambers to be refrigerated, first and second evaporators disposed for cooling the chambers, respectively,'a common means for supplying condensed refrigerant to the evaporators in such manner that it fiows intothe first evaporator until filled and thence into the second evaporator, means for Withdrawing the refrigerant vaporized in the evaporators from the second evaporator, a first means responsive to the superheat of the refrigerant vaporized in the first evaporator for controlling the flow of condensed refrigerant to the evaporators, a, second means responsive to the superheat of the refrigerant withdrawn from-the second evaporator for controlling' the fiow of condensed refrigerant to the evaporators, means responsive to predetermined temperatures within the first and second chambers for respectively effecting operation of the refrigerant supply means, said second superheat responsive means being rendered effectiveto control the fiow of refrigerant during periods when the second temperature responsive means effects operation of the refrigerant supply means, and said first superheat responsive means being effective at other times that the refrigerant supply means is operated.

8. In refrigerating apparatus, the combination of first and secondevaporators, means for condensing refrigerant for the evaporators, means for conveying the condensed refrigerant to the first evaporator, a conduit for conveying refrigerant from the first evaporator to the second evaporator, a second conduit for conveying refrigerant vaporized in the evaporators from the second evaporator to the refrigerant condensing means, a valve for controlling the fiow of con-- densed refrigerant conveyed by said refrigerant conveying means, means responsive to the pressure of the refrigerant in the evaporators for actuating. said valve in one direction, a gas-type thermostat element for biasing the valve in opposition to said pressure responsive means, said thermostat element including an enclosed gas and liquid space having first and second liquid reservoir portions disposed in heat exchanging relation with the first and second conduits respectively, means for heating the first reservoir portion, means for effecting operation of the refrigerant condensing means and for energizing the heater during periods when the second evaporator is rendered active, and means for effecting operation of the refrigerant condensing means without energizing the heater when the first evaporator is rendered active.

9. In refrigerating apparatus, the combination of first and second evaporators, means for condensing refrigerant for the evaporators, means forconveying the condensed refrigerant to the first evaporator, a conduit for conveying refrigerant from the first evaporator to the second evaporator, a. second conduit for conveying refrigerant vaporized in the evaporators from the rality of means responsive to the superheat of;

second evaporator to the refrigerant condensing means, a valve for controlling the fiow of condensed refrigerant conveyed by said refrigerant conveying means, means responsive to the pressure of the refrigerant in the evaporators for ,5 actuating said valve in one direction, a gas-type thermostat element for biasing the valve in opposition to said pressure responsive means, said thermostat element including an enclosed gas and liquid space having first and second liquidll reservoir portions disposed in heat exchanging relation with the first and second conduits respectively, means for heating the first reservoir portion, means responsive to a predetermined temperature produced bythe second evaporatorglii for effecting operation of the refrigerant condensing means and said heating means, and

means responsive to a predetermined temperature produced by the first evaporator for energizing the refrigerant condensing means.

10. In a refrigerating system, the combination of an evaporator, circulating means for withdrawing vaporous refrigerant from the discharge end of the evaporator and for translating condensed refrigerant to the admission end thereof, 25 a valve for controlling the admission of condensed refrigerant to the evaporator, a pressure responsive element for actuating the valve and subjected to the pressure of the refrigerant in the evaporator, means defining a chamber for a vola-: tile fluid and so disposed that said pressure responsive element is biased by the pressure of said fiuid in opposition to the pressure of the refrigerant, said chamber including first and second reservoir portions for condensed fluid, said sec-t 0nd reservoir portion being disposed in heat ex-' changing relation with the discharge end of the evaporator from which vapor is withdrawn, said first reservoir portion being disposed in heat exchanging relation with a portion of the evaporator intermediate the admission and discharge ends thereof, a heater for the first reservoir portion, means for effecting operation of the heater and the circulating means whereby vaporization of refrigerant is effected throughout a substantial portion of the evaporator and said pressure responsive element is subjected to the pressure of the volatile fluid corresponding to the temperature of said second reservoir portion, and means for effecting operation of the circulating means whereby vaporization of refrigerant is effected in the portion of the evaporator between the admission end thereof and said intermediate portion and the pressure of the volatile fluid on the pressure responsive element corresponds to the. temperature of the first reservoir portion.

11. In a refrigerating system, the combination of an evaporator having a plurality of portions thereof serially arranged with respect to the flow of refrigerant, refrigerant circulating means for withdrawing vaporous refrigerant from the evaporator and for delivering condensed refrigerant thereto, a device for controlling the admission of condensed refrigerant to the evaporator, a plu- 66 the vaporous refrigerant in the respective evaporator portions for controlling said device and means for selectively rendering the superheat responsive means active to control the device so that the area of the evaporator which is effective, for cooling is varied.

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