US2186984A - Refrigerating apparatus - Google Patents

Description

Jan. 16, 1940. G. s. MccLoY REFRIGERATING APPARATUS Filed April 25, 1958 "-lo o DEGREES F.

Patented Jan. 16, 1940 UNITED STATES PATENT OFFICE REFRIGERATING APPARATUS Application April 23, 1938, Serial No. 203,806

8 Claims.

'temperature exteriorly of the refrigerated zone,v

i which mechanism may embody elements of a conventional gas type thermostat.

Another object of the invention is to provide a thermostat for controlling the operation of a refrigerator and including a single gas type theri mostatic element that responds to temperaturer changes within the refrigerated zone and exteriorly thereof.

'I'hese 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: e I

Fig. 1 is a diagrammatic view of a refrigerator controlled in accordance with my invention;

Fig. 2 is a diagrammatic view similar to Fig. 1 anddlsclosing a'second embodiment of the invention; and, i Fig. 3 is a diagram showing the pressure-temperature characteristics of the'uids in the thermostatic element for three different ambient temperatures.

Reference will now be had to Fig. 1 of the drawing wherein I have shown my invention applied to a domestic type refrigerator employing a refrigerating machine of the compressor-condenser-expander type. A refrigerator cabinet indicated at I0 defines a heat insulated zone or v chamber II from which heat is abstracted by an evaporator I2 which may be constructed in any suitable manner. Refrigerant vaporized in the evaporator I2 is withdrawn through a conduit I3 by means of a compressor I4 driven by a motor I5. The compressed refrigerant gas is discharged through a conduit IB in a condenser I1 and is cooled in any suitable manner, suclfas, for example, by means of a motor driven fan I9. Refrigerant liquefied in the condenser is delivered to the evaporator 'I2 through a conduitl I9 having a suitable expansion device 2| connected therein for reducing the pressure of the liquefied refrigerant to the pressure of vaporization maintained within the evaporator I2.

'I'he motor I5 is supplied with electrical energy from a suitable source indicated by the line conductors L1 and La under control of a snap-acting l switch"'mechanism 22. The switch 22 deflnesan element of a gas type thermostat, generally indicated at 23 and including a bellows 24, that moves a main pivoted lever 25 upwardly and downwardly as it expands and contracts. An l0 over-center spring 26 may connect the lever 25 to the switch mechanism 22 for imparting snap action to the switch 22 in a well-understood manner. The pressure within the bellows 24 at which the switch is opened and closed may be 15 determined by a spring 21 which provides a bias on the bellows. The bias of the spring 21 may be varied by an adjusting device indicated at 29. The bellows 24 is connected by means of a conduit 29 to a bulb or reservoir 3l disposed within the refrigerated zone II and, preferably, in contact with the evaporator I2 so that its temperature varies with the temperature of the evaporator I2.

In accordance with my invention, means is provided for varying the temperature of the evaporator I2 at which the thermostat mechanism 23 operates the switch 22, in `response to changes in temperature exteriorly of the refrigerated zone II. A second conduit 32 provides communication between the conduit 29 and a second expansible bellows 33 that is disposed within a fluid 34 and container 35. The container 35 is disposed in the atmosphere exteriorly of the zoneII so that the fluid 34 will expand and contract with increases and decreases in the temperature of the outside atmosphere.

The bellows-33 and 24, the conduits 29 and 32 and the bulb or reservoir 3I denne a closed chamber for containing first and second uids, one of which is a volatile fluid whose pressure varies with the temperature of the evaporator I2l and bulb 3|. The second fluid is, preferably, an inert gas whose pressure is substantially unaffected by the temperature of the evaporator I2. The bellows 24 is subjected to the combined pressures of the two fluids. As the bulb 3i denes thecoldest portion of the structure containing the two fluids, the liquid portion of the volatile fluid is always present in the bulb 3| and the pressure of the volatile fluid-is a function of the temperature of the liquid portion thereof. The second non-condensable fluid or inert gas is diffused with the gas of the volatile fluid and its pressure varies with expansion and contraction of the bellows 33. As the outside or room temperature increases and decreases, the expansion and contraction of the fluid 34 contracts and expands the bellows 33. Accordingly, the pressure of the inert gas increases and decreases with respective increases and decreases in the temperature of the atmosphere exteriorly of the zone II. The pressure exerted by the primary or volatile uid is not affected by room temperature changes as its pressure is a function of the temperature of the liquid portion thereof.

My invention will bc best understood by referring to the curves shown in Fig. 3. The curve A shows the pressure temperature-characteristics for the primary or volatile fluid employed in the thermostat. The total pressures in the thermostat, or the sums of the pressures of the volatile fluid and the inert gas, for three different ambient temperatures are shown at B, C, and D. The curve B represents the variation in total pressure in the thermostat when the lowest expected ambient temperature obtains. When this condition prevails, the pressure of the inert gas is minimum. The curves C and D show the variations in total vpressures for progressively higher ambient temperatures with correspondingr progressive increases in the pressure of the inert gas. It will be apparent that, as the ambient temperature increases, the portion of the total pressure which is exerted by the secondary or inert gas is increased, and vice versa.

As an example, any of the inert gases such as, nitrogen, may be used with a. volatile fluid such as, sulphur dioxide (SO2) in effecting the control decribed heretofore. When a uid having a low boiling point is employed as a secondary gas, or the gas whose pressure changes with variations in outside temperature, satisfactory operation is provided by the use of sulphur dioxide SO2 as the primary fluid and dichlorodiiiuoromethane CCIQF: as the secondary fluid. The latter may be charged at a pressure of 5 lbs. per square inch so that it would provide compensation at evaporator temperature of 8 F, and above. The conditions to be fulfilled in the latter combination are that the two constituents are inert toward each other and are not miscible in each other and that the secondary gas be charged into the system at a pressure such that condensation of the gas would not occur at the evaporator temperature at which the machine operates. Accordingly, the secondary gas, or the dichlorodifluoromethane in the example cited, is in a superheated condition at all 4normal evaporator temperatures.

The thermostat 23 operates to close and open its switch 22 for starting and stopping operation of the compressor I4 when respective predetermined high and low total pressures obtain in the bellows 24.

Operation It will be assumed that the control thermostat 23 1s adjusted to initiate and terminate operation started and stopped in response to evaporatortemperatures of 28 F. and 2 F., respectively,

when the temperature of the room is relatively low.

An increase in the temperature of the air in the room causes expansion of the fluid 34 in the container 35 and, therefore, contraction of the bellows 33, whereby the inert gas is compressed and its pressure increased. It will be assumed the room temperature increase is such that the pressure of the gas is increased 2 lbs. per sq. in. The control still functions to close and open the switch 22 at 20 lbs. and 3 lbs., respectively, total pressure. As shown by the curvo C in Fig. 3, these pressures correspond to evaporator temperatures of 25 F. and 10 F., respectively. The evaporator I2, therefore, is operated at a lower temperature with a high room temperature and compensates for the higher heat leakage into the zone II due to the higher room temperature.

A further increase in the ambient temperature elects a further increase in the pressure exerted by the secondary fluid, so that the evaporator is operated in accordance with the pressure temperature characteristics of curve D. As shown by curve D, the temperature of the evaporator, corresponding to 20 lbs. pressure in the bellows 24 is 20 F., at which temperature the compressor I4 is started. The temperature of the evaporator corresponding to a total pressure of 3 lbs. in the bellows is 18 F. at which temperature the compressor is stopped.

The gures which I have employed in connection with thek curves in Fig. 3 are approximate and have been used for illustrative purposes only.

It will be apparent from the foregoing description that the evaporator is operated at temperatures which vary inversely with changes in ambient temperature whereby compensation is provided for different rates of heat leakage into the refrigerated zone to maintain the temperature of the refrigerated media substantially constant.

Description-Fig. 2

In Fig. 2 I have disclosed a second embodiment of the invention wherein different means are employed for obtaining the pressure variation in the bellows due to a change in room temperature. The refrigerating system is similar to that shown in Fig. l and similar elements are designated by like reference characters. Also, the thermostat is of similar construction to the thermostat structure 23 except for the element which is `subjected to room temperature and its contents. Parts common to the thermostats of Figs. 1 and 2 are designated by like reference characters.

In the embodiment shown in Fig. 2, I employ, in addition to the volatile fluid whose pressure varies with evaporator temperature, a gas which is soluble in an absorbing material 4I in amounts bearing a relation to the temperature of such material. The absorbent material 4I is contained in a container 42 that communicates with the bellows 24 and conduit 29 by a tube or conduit 43. As the temperature of the absorbent material 4I increases, gas is driven therefrom and increases the pressure in the bellows 24. Conversely, as the temperature of the material 4I decreases, the gas is absorbed by the material and the pressure in the bellows 24 is decreased. Accordingly, the relation between the total pressure in the bellows 24 and the temperature of the volatile fluid in the bulb 3I is varied for the purpose of varying the temperatures of the evaporator l2 at which the bellows 24 effects opening and closing of the motor control switch 22. The result of this operation has been described heretofore in connection with Fig. l and need not be repeated.

'I'he soluble gas employed in Fig. 2 may be ammonia with calcium chloride as the absorbent.

Dichlorodiiluoromethane (CCLzFz) gas may be employed with oil as the absorbent. Where dichlorodifluoromethane is used as the secondary gas and oil as the absorbent, any volatile fluid may be employed as the primary fluid, provided it is not mscible in the oil to any material degree and that it does not react with dichlorodiiluoromethane. Sulphur dioxide SO2 may be satisfactorily employed as the primary fluid in this combination of fluids. When ammonia gas' and calcium chloride are used as the secondary fluid and absorbent, it is necessary that the primaryy gas is non-absorbent in calcium chloride and inert toward ammonia. Dichlorodifluoromethane may be employed in this combination of fluids.

In both of the systems described heretofore, the total pressure obtaining in the bellows is the sum of the partial pressures of the volatile fluid and the secondary gas so that the switch is operated in response to predetermined values of said totalyv Ipressure.

When the ambient temperature is high, the partial pressure exerted by the secondary gas is .relatively high so that the pressure of the volatile fluid and temperature of the evaporator are relatively low when the switch is actuated. When the ambient temperature is reduced, the partial pressure of the secondary gas is reduced and the partial pressure of the volatile fluid and the temperature of the evaporator are Arelatively high as the switch is actuated.

From the foregoing, it will be apparent that I have provided an improved refrigerating system wherein compensation is eilected forl different rates of heat yleakage into the refrigerated chamber due to varying temperatures exteriorly of the chamber, so that the temperature of the refrigerated media is maintained substantially constant.

I have described my invention in connection with a refrigerating system of the compression type, but it is to be understood that it is not so limited and may be applied equally well to other forms of thermostatically controlled refrigerating apparatus.

While I have shown my invention in several forms, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various other changes and modifications without departing from the spirit thereof,- and I desire, therefore, that only such limitation shall be placed thereupon as are imposed by the `prior art or as are specifically set forth in the appended claims.

What I claim is:

l. In refrigerating apparatus, the combination of means defining a zone to be refrigerated, a cooling element for abstracting heat from said zone, means for circulating refrigerant through the cooling element, a control device for starting and stopping operation of the circulating means, expansible means having a portion thereof disposed in heat transfer relation with the cooling Aelement and enclosing first and second uids, one

of which is a volatile fluid whose partial .pressure is a function of the temperature of said'cooling element at normal operating temperatures and the other fluid being non-condensable at normal operating temperatures, said expansible means being effective to operate said control device to initiate and terminate operation of the circulating means when the expansible means is subjected to predetermined high and low total pressures, re-

`spectively, and means for varying the partial pressure of said non-condensable fluid in response to changes in temperature exteriorly of the refrigerated zone.

2. In refrigerating apparatus, thecombination of means defining a zone to be refrigerated, a cooling element for abstracting heat from said zone, means for circulating refrigerant through the cooling element, expansible means having a portionY thereof extending into the refrigerated zone and defining a chamber for containing first and second fluids, said first fluid being condensable at normal operating temperatures of the zone so that the pressure thereof varies with the temperature of the zone and said second fluid being non-condensable at normal operating temperatures of the zone so that its partial pressure is substantially unaffected byy temperature changes in the zone, a control device actuated by the expansible means for rendering the circulati ing means active and inactive in response to predetermined high and low total pressures within said expansible means, and means for varying the partial pressure of said non-condensable fluid in response to changes in temperature exteriorly of the refrigerated zone whereby the relation bezone, means for circulating refrigerant through said element, a switch movable to closed and open position for respectively energizing and deenergizing the circulating means, expansible means having a portion thereof disposed in heat transfer relation with the cooling element for closing and opening the switch when respective predetermined high and low pressures prevail within the expansible means, said expansible means containing both a volatile fluid, the pressure of which is a function of the temperature within the refrigerated zone and a second fluid, the pressure of which is substantially unaffected by the temperature of the refrigerated zone, and means responsive to the temperature exteriorly of the zone for Varying the pressure of the second fluid whereby the relation between the total pressures within the expansible means at which the switch is operated and the temperature of the volatile fluid is varied.

4. In refrigerating apparatus, the combination of means defining a zone to -be refrigerated, a cooling element for abstracting heat from said zone, means for circulating refrigerant through said element, a switch movable to closed and open position for respectively energizing and deenergizing the circulating means, expansible means having a portion thereof disposed in heat 1 temperature exteriorly of the zone for varying the relation between the pressures exerted by the volatile fluid and the inert gas, whereby the temperatures and pressures of the volatile fiuid at which the switch is operated are varied with changes in temperature exterior of the zone.

5. In refrigerating apparatus, the combination of means defining a zone to be refrigerated, a cooling element for abstracting heat from said zone, means for circulating refrigerant through the cooling element, an expansible bellows, a conduit connected to said bellows and disposed in heat transfer relation with the cooling element, said bellows and conduit defining a closed chamber for enclosing both a volatile fluid whose pressure vari'es with the temperature of the cooling element and an inert gas whose pressure is substantially unaiected by the temperature of the cooling element, a switch for controlling operation of the circulating means and closed and opened by said bellows in response to respective predetermined high and low pressures therein, and means for varying the pressure of the inert gas in response to changes in temperature exteriorly of the Zone, whereby the relation between the total pressure in the closed chamber and the temperature of the volatile fluid therein is varied as the temperature exteriorly of the zone varies 6. In refrigerating apparatus, the combination of means defining a zone to be refrigerated, a cooling element for abstracting heat from said zone, means for circulating refrigerant through said element, a switch movable to closed and open position for respectively energizing and deenergizing the circulating means, a bellows for closing and opening the switch in response to predetermined high and low pressures in the bellows, a conduit communicating with the bellows and disposed in heat transfer relation with the cooling element, an expansible member disposed exteriorly of the refrigerated zone and communicating with said bellows and conduit, means for compressing and expanding the expansible member in response to respective increases and decreases in temperature exterior of the zone, said bellows, expansible member and conduit dening a closed chamber for containing both a volatile fluid whose pressure is a function of the. temperature of the cooling element and an inert gas whose pressure varies with expansion and contraction of the expansible member, and is substantially independent of the temperature and pressure of the volatile fluid.

7. In refrlgerating apparatus, the combination of means defining a zone to be refrigerated, a cooling element for abstracting heat from said zone, means for circulating refrigerant through said element, a switch movable to closed and open position for respectively energizing and deenergizing the circulating means, a bellows for closing and opening the switch in response to predetermined high and low pressures in the bellows, a conduit communicating with thcl bellows and disposed in heat transfer relation with the cooling element, and a vessel disposed in heat transfer relation with the atmosphere exteriorly of said zone, said bellows, conduit and vessel defining a closed chamber for containing both a volatile fluid whose pressure is a function of the temperature of the cooling element and a gas whose pressure is substantially unaffected by the temperature of the cooling element, said vessel containing an absorbent material in which the gas is soluble in amounts bearing a relation to the temperature of the absorbent material, whereby the relation between the pressures of the gas and fluid in the bellows varies with changes in ternperature exteriorly of said zone, and, therefore, the temperature of the cooling element at which the circulating means is started and stopped is varied inversely with the changes in the exterior temperature.

8. In a temperature control system, the combination of means dening a zone whose temperature is to be maintained within predetermined limits, heat transfer apparatus associated with said zone, expansible means for controlling the operation of said heat transfer apparatus, a portion of said expansible means being subjected to the temperature produced by said apparatus, said expansible means containing a volatile fluid whose pressure is a function of the temperature produced by the heat transfer apparatus and also containing a gas whose pressure is substantially unaffected by the temperature produced by the heat transfer apparatus, and means responsive to the temperature of a region exteriorly of said zone for varying the pressure of the gas within the expansible means whereby the relation between the total pressure in the expansible means and the pressure of the volatile fluid therein is varied as the temperature of the region exterior of said zone varies.

GRAHAM S. MCCLOY.

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