US2133948A

US2133948A - Refrigeration apparatus

Info

Publication number: US2133948A
Application number: US15003A
Authority: US
Inventors: Leslie B M Buchanan
Original assignee: Westinghouse Electric and Manufacturing Co
Current assignee: CBS Corp
Priority date: 1935-04-06
Filing date: 1935-04-06
Publication date: 1938-10-25
Anticipated expiration: 1955-10-25

Description

Oct. 25 1938. L. B. M. BUCHANAN REFRIGERATION APPARATUS Filed April 6,1955

' 2 Sheets-Sheet 2' 'F1a;':o.' 64 WARNER EVRPORFITOR n I fl- 1e y 11 1% v '72 EVHPORRTDR v UNITED STATES PATE Patented Oct. 25, 1938 2,133,948 REFRIGERATION APPARATUS NT. OFFICE of Pennsylvania Application April 6, 1935, Serial-No. 15,003

20 Claims.

My invention relates to refrigeration apparatus, more particularly to refrigeration apparatus embodying a plurality of evaporators operating at different temperatures, and it has for an .object to provide improved apparatus.

A further objectis to provide apparatus of the character set forth having a minimum number of parts, particularly moving parts such as valves.

Another object is to provide such apparatus in which the higher temperature evaporator operates at higher pressure to provide increased efficiency and capacity, and which apparatus has a minimum number of moving parts.

A further object is to prevent condensation of gaseous refrigerant in the lower temperature evaporator when the higher temperature evaporator is in operation at the higher pressure.

Another object is to provide apparatus of the above type in which the mechanism for selecting the evaporator to be refrigerated may be disposed in the high side of the system rather than in the low side, so that it need not be heat insulated to prevent condensation of moisture.

In accordance with my invention, I provide a lower temperature evaporator and a higher temperature evaporator in free communication with each other, so that .the pressure therein is always substantially the same. I arrange the evaporators, and the connection between them and the supply of liquid refrigerant, in such manner that liquid refrigerant flows into the low tempera ture evaporator in preference to the higher temperature evaporator. This may be done, for example, by disposing the connection to the low temperature evaporator, at the point of division, at a lower level than the connection to the higher temperature evaporator. When refrigeration isto be effected in the lower temperature evaporator,

liquid refrigerant is supplied only to said lower temperature evaporator, the higher temperature evaporator remaining dry so that evaporation of refrigerant cannot take place therein. The superheating of the vapor in the latter does not affect the low pressure necessary for operation of the lower temperature evaporator. Whenrefrigeration is to be effected in the higher temperature evaporator, the lower temperature evapor'atoris first substantially filled with liquid refrigerant by reason of the arrangement giving it preference, andthen the higher temperature evaporator is supplied with liquid refrigerant to effect evaporation therein. By filling the lower temperature evaporator with liquid refrigerant, condensation of vaporous refrigerant therein, which would otherwise be caused by 5 the higher pressure effected by evaporation in the higher temperature evaporator, is avoided.

In the preferred form of my invention, which is claimed herein and several modifications of which are illustrated in the drawings, the refrigerating 5 system is charged with such quantity of refrigerant as will substantially fill the lower temperature evaporator and supply sufiicient liquid refrigerant to the higher temperature evaporator for operation thereof. There is also provided 10 means for retaining, in a part of the refrigerating system other than the higher temperature evaporator, suflicient refrigerant, preferably in liquid form, to prevent the higher temperature evaporator from receiving liquid refrigerant. In this 15 form, refrigeration is provided selectively in the lower temperature or the higher temperature evaporator by retaining or releasing refrigerant in said retaining means. The refrigerant vaporized in the lower temperature evaporator may be con- 20 veyed to the compressor through the higher tem perature evaporator, thereby superheating the vapor and cooling the evaporator.

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

Fig. 1 is a diagrammatic view of one form'of refrigerating system embodying my invention, showing the lower temperature evaporator in operation;

Fig. 2 is a similar partial view showing the higher temperature evaporator in operation;

Fig. 3 is a diagrammatic view of a second embodiment;

Figs. 4 and 5 are detail views of a modified form of retaining means, said figures showing the retaining means in condition for retaining liquid refrigerant and for releasing liquid refrigerant, respectively;

Figs. 6,7, and 8 are diagrammatic views showing additional embodiments of the invention;

Fig. 9 is a vertical sectional view of a twotemperature refrigerator embodying the pre- 'ferred form of refrigerating system, the latter being diagrammatically shown in parts;

Fig. 10 is a perspective view of the evaporators of Fig. 9;

Fig. 11 isa plan view of a detail, as seen from the line XI -XI of Fig. 10;

Fig. 12 is a detailsectional view of the connection between the evaporators and the refrigerant s pply;

Fig. 13 is a diagrammatic view of another form of refrigerating system representing a further development of the embodiment of Fig. 9; and

Figs. 14 and show additional forms of control systems for two-temperature refrigerators.

Referring to Fig. 1 in detail, I show a refrigerator III having a compartment II which is refrigerated to a relatively low temperature by an evaporator I2, and a compartment I3 refrigerated by an evaporator I4 to a temperature which is higher than that maintained in the compartment II. The temperature in the compartment II may be below freezing, in order to freeze ice and maintain frozen articles, while the temperature in the compartment. I3 may be above freezing but sufficiently low for the preservation of food. The evaporator I2 is refrigerated or operated, that is, refrigerant therein is evaporated, at a lower temperature and at a lower pressure than the evaporator I4, and is referred to herein as the lower temperature or colder evaporator while the latter is referred to as the higher temperature or warmer evaporator. The evaporators are operated at difierent times, rather than simultaneously; each evaporator being operated at intervals for sufficient periods of time, preferably under thermostatic control,.

to maintain the respective temperature in its compartment.

Each evaporator may be of any desired form,

eitherof the flooded type, or of the type knownv in the art as a dry evaporator, although the latter is not dry in operation but contains a mixture of liquid and vaporous refrigerant. In the present embodiment, the evaporator I2 is of the flooded type, having a header. I5 and refrigerant passages I6 extending downwardly from the lower portion of the header. The header is formed with an outlet I1 disposed above the passages I6, preferably at the top of the header, and communicating through a conduit I8 with the warmer evaporator I4. The latter is illustrated in this embodiment as of the dry type, comprising a crossefinned coil, and it preferably has sufiicient area of cooling surface to maintain the compartment I3 at the desired temperature with minimum temperature difference, so as to maintain a relatively high humidity of the air in the compartment.

The outlet end of the evaporator I4 is connected through a conduit I9 to the inlet 2I of a compressor 22, which is enclosed, together with its driving motor in a hermetically-sealed casing 23. The compressor and its motor may be of any suitable form known in the art. The outlet of the compressor is connected through a conduit 24 to a condenser 25. The latter may be air-cooled by a motor-driven fan 26. The condenser in turnis connected through a conduit 21 to a chamber 28. A conduit 29, which connects the chamber 28 with a high side float valve 3|, has one branch 32 connected to the bottom of the chamber 28 and a second branch 33, the mouth of which communicates with the chamber 28 adjacent the top. A valve 34 is provided for shutting off flow through the conduit 32. The float valve 3! communicates with the header I5 of the evaporator I2 through a conduit 35.

It will be noted that the outlet I'I, through which refrigerant is supplied to the evaporator I4, communicates with the header I5 in the upper portion thereof, so that refrigerant admitted to the header I5 from the conduit 35,

flows, by gravity, into and fills the passages I6 of the evaporator I2 in preference to the evaporator I4. Liquid refrigerant passes through the outlet I'I into the evaporator I4 only when the evaporator I2 is filled to the level of the outlet I! in the header I5. A perforated baffle 36 is preferably provided in the header I5, below the conduit 35 and the outlet l1 and above the pas sages I6, as shown in Figs. 1 and 2, for a purpose hereinafter described.

The refrigerating system is charged with a quantity of refrigerant such that, when the valve 34 is open, there is suflicient liquid refrigerant supplied to the evaporators, as shown in Fig. 2, to fill the evaporator I2 to the level of the outlet I1 and to supply sufficient liquid refrigerant to the evaporator I4 to effect evaporation throughout substantially the full length thereof. The space within the chamber 28 below the mouth of the branch conduit 33 is such as to retain, when the valve 34 is closed, a 'suflicient quantity of liquid refrigerant, as shown in Fig. 1, so that there will not be sufficient liquid 1'." frigerant delivered to the header I5 to supply the evaporator I4 but only suflicient to provide the evaporator I2 with the quantity needed to effect operation thereof. In the latter case, the liquid level in the header I5 is maintained below the top of the header in order to provide a vapor space to take care of boiling of the liquid. The quantity of liquid refrigerant retained in the chamber 28 represents substantially the quantity of liquid within the evaporator I4 when it is'in operation, plus the liquid displaced by vapor in the evaporator I2 when it is in operation.

To efiect refrigeration of the compartment. I3, operation of the compressor 22 and the fan 26 is started and the valve 34 is opened. This may be effected by a thermostatic control, a form of which will be hereinafter described. All of the condensed refrigerant now passes through the chamber 28 and the float valve 3| to the evaporators, as indicated in Fig. 2. This quantity is now sufficient to fill the evaporator I2 with liquid up to the level of the outlet II, in this case completely filling the header I5, and to supply the evaporator I4 with a suflicient quantity for effecting evaporation substantially throughout said evaporator. The liquid refrigerant in the evaporator I4 is vaporized by the heat extracted from the compartment I3 and passes through the conduit I9 to the compressor 22, wherein its pressure is increased. It is then conveyed through the conduit 24 to the condenser 25 wherein it is condensed and then discharged to the conduit 21 to be recirculated.

As the temperature of the evaporator I4 is higherthan the temperature of the evaporator I2, the pressure in the low side of the system, that is, the portion from the discharge side of the float valve to the inlet of the compressor, is higher than when-the evaporator I2 is in operation.- This pressure is not sufficiently low to effect evaporation in the evaporator I2, so that the latter remains inactive. In fact, the pressure is sumciently high so that any vapor entering the evaporator I2 would tend to condense, but this is avoided or largely minimized by fllling the evaporator I2 with liquid, which does not give off heat when its pressure is increased as does a vapor. The purpose of the baffle 36 is to guide the refrigerant from the conduit 35 as directly as possible to the outlet H with mini-' mum intermingling with the liquid in the evaporator I2. The liquid coming from the conduit 35 is at a higher temperature than that in the evaporator I2, since it is not subjected to as low 2,183,948 a temperature as that effected when the evaporator I2 is in operation. The portion of the conduits 35 and I8 within the compartment II and the upper portion of the header I5 maybe covered with heat insulating material. The refrigerating action is discontinued when the temperature of the compartment I3 has been reduced to the desired value.

To effect refrigeration of the colder compartment II, the compressor 22 and the fan 26 are started and the valve 34 is closed, this operation also'being preferably effected by a thermostatic control. The condensed refrigerant'conveyed through the conduit 21 is retained in the chamber 28 until it reaches the level of the mouth of the branch conduit 33, as indicated in Fig. 1. As the supply of liquid refrigerant to the evaporators is temporarily cut off, continued operation of the compressor effects evaporation of the liquid refrigerant in the evaporator I4 and of that in the top of the header I5. Most of the latter refrigerant is forced into the evaporator I4 and evaporated due to the boiling or evaporation that is effected in the evaporator I2 as the pressure is reduced. Evaporation takes place for the time being in both evaporators, but the amount of liquid in the evaporator I4 is gradually reduced to Zero. Thereafter, evaporation takes place only in the evaporator I2, and when the liquid level in the chamber 28 reaches themouth of the branch conduit 33, liquid refrigerant is supplied therethrough to the evaporator I2. The retaining of the liquid refrigerant in the chamber 28 reduces the effective refrigerant charge to the extent that sufficient liquid refrigerant passes into the header I5 to just supply the evaporator I2. 7

The refrigerating apparatus now operates in the usual manner of a refrigerating system embodying a flooded evaporator such as shown at I2 except that the refrigerant vaporized in the evaporator I2 and withdrawn through the outlet Il, passes through the evaporator I4. The

refrigerant vapor is superheated therein, effecting some cooling of the compartment I3,and then discharged through the conduit I9 to be compressed, condensed, and recirculated.

In Fig. 3, I show a modified form of means for retaining the necessary quantity of refrigerant to reduce the effective charge and permit evaporation in the colder evaporator I2. This means comprises a chamber 37 connected btween the evaporators I2'and I4 by

conduits

38 and 39, respectively. The conduit 39 is connected to the chamber 37 at a level high enough so that there -may be retained in the chamber 37 below said connection the necessary quantity of refrigerant, such as that retained in the chamber 28 of Fig. 1, for effecting operation of the evaporator I2. A plunger 4| is provided in the chamber 31 for displacing liquid and has a core portion 42 adapted to be actuated by a solenoid 43 for raising the plunger 4|.

To effect refrigeration of the evaporator I4 of Fig. 3, the plunger 4i is released and allowed to displace the liquid in the bottom of the chamber 3'1. The level of the liquid is raised so that it flows through the conduit 39 into the evapoevaporator 21, in this case, is connected directly to the float valve 3|. The full charge of refrigerant is effective so that sufficient liquid refrigerant will be passed through the header I5 to supply the I4. To effect operation of the evaporator I2, the solenoid 43 is energized to raise the plunger 4|. Suflicient liquid refrigerant is now retained in the chamber 37 to starve the evaporator l4, so that only the evaporator I2 receives liquid refrigerant and evaporation is thus effected therein, as will be clear.

In Figs. 4 and 5, I show another form of re frigerant retaining means. This comprises a chamber 44 pivoted to a supporting member 45 in such manner as to be movable between the two positions shown in these figures. I This chamber may be interposed in any part of the refrigerating system between the condenser and the evaporator- I4; for this example it will be assumed that it is connected between the condenser 25 and the float valve 3I flexible conduits 2'! and 29, respectively. When the chamber 44 is tilted downwardly, as shown in Fig. 4, it retains liquid refrigerant to reduce the effective charge, and, when it is raised as shown in Fig. 5, it discharges the liquid refrigerant to the float valve through the conduit 29' so as to compartment I3 increases to a value indicating need for refrigeration, the increased pressure in the bulb 46 transmitted to the bellows 48 causes the latter to raise the chamber 44 through the toggle link 49. The liquid refrigerant retained in I the chamber is released so as to supply the evaporator I4 therewith for operation thereof in the I manner previously described. When the temperaturein the compartment I3 is reduced to'the desired value, the bellows 48 contracts to move the chamber 44 downwardly to the position shown in Fig. 4. Refrigerant is retained therein for operation of the colder evaporator I2 as already described. Suitable control mechanism for starting and stopping the compressor and the condenser fan is provided for supplying the refrigeration requirements of both compartments. The thermostatic control of Fig. 4 gives preference to the warm compartment when both compartments require refrigeration.

It may be arranged to give preference to the colder compartment by placing the bulb 46 of Fig. 1 by therein and reversing its direction of operation with respect to the chamber 44; that is, upon increase in temperature in the colder compartment, the chamber 44 would be tilted downwardly as shown in Fig. 4. I

In Fig. 6, I show an embodiment of my invention in which a header 5| for the colder evaporator I2a also serves as the refrigerant retaining means.-

The header 5| is provided with two outlets Ila.

and Ill), disposed at upper and lower levels between which liquid refrigerant is retained. The outlet I'la is connected to the warmer evaporator I4a through a valve 52 and the outlet Ilb is connected thereto through a looped conduit 53 which extends to a higher level before connecting with the evaporator Ma. The low temperature evaporator I2a is shown in the form of a'coil, but it is a flooded evaporator in its operation, both ends being connected to the header 5| below the liquid level therein, though preferably at different levels. Obviously, it may be of any desired form of the flooded type.

When the valve 52 is closed, liquid refrigerant is forced through the outlet 1b to the evaporator lda until the liquid level is brought down to the outlet no, as shown at 54. This is due to the fact; that the vaporous refrigerant formed on the discharge side of the float valve 3| collects in the upper portion of the header 5|. The system is charged with sufficient refrigerant to supply the evaporator Ma under this condition, and operation thereof is effected in the same manner as already described. To effect operation of the low temperature evaporator I2a, the valve 52 is opened. The vaporous refrigerant in the upper part of the header 5| now passes through the outlet |1a to the evaporator Ma, and liquid refrigerant no longer flows through the conduit 53 but is retained in the header 5| for the reason that there is no longer a sufficient pressure difference to the outlet HD to retain the necessary quantity of I liquid refrigerant therebetween, so that the evaporator la does not receive liquid refrigerant. The

outlet |1a may be disposed at the higher liquid level now maintained in the header 5| and shown at 55, so as to draw off the lubricant at the surface of the liquid. However, it may be disposed at a higher level if desired in which case the lubricant will be removed through the outlet |I|b when the evaporator Ma is in operation, particularly in initiating operation thereof after previous operation of the low temperature evaporator |2a.

In Fig. '1, I show an embodiment of my invention in which the low temperature evaporator 56 is of the so-called dry type arranged in series ahead of the warmer evaporator Ma. Inasmuch as relatively warm refrigerant passes through the evaporator 56 when the warmer evaporator is in operation, it is disposed in the upper portion of a brine chamber 51, the lower portion of which is adapted to effect the cooling action, such as, freezing of water in the ice trays 58. The retaining means comprises a chamber 28a, substantially similar to the chamber 26 of Fig. 1, and is connected at the bottom to the float valve 3| through a conduit 32a having a valve 34a and adjacent the top through a conduit 33a.

To effect refrigeration in the low temperature evaporator 56, the valve 34a is closed so as to retain a quantity of refrigerant in the chamber 28a. Only sufficient liquid refrigerant passes on to supply the evaporator 56 so that evaporation at low pressure and temperature therein is effected. The evaporator 56 cools the brine in the chamber 51, which brine circulates by convection to the lower portion'of the chamber to cool the ice trays 58. The vaporized refrigerant is conveyed through the evaporator a. and the operation is otherwise the same as already'described. When the evaporator Ma is placed in operation by opening the valve 34a, the pressure in the low side of the system is increased due to the higher temperature .of the evaporator Ha. Consequently, relatively warm refrigerant passes through the evaporator 56 and heats the brine in the upper portion of the chamber 51. Inasmuch as the warm brine tends to remain at the top of the duit 32b to the connection 62.

chamber, this heat is not conducted to the ice trays 58 to any great extent. The arrangement of the evaporator in the upper portion of the brine chamber-so as to avoid heating of the ice trays when warm refrigerant is conveyed therethrough is the invention of Graham. S. McCloy.

In Fig. 8, I show a further embodiment including a low temperature evaporator 59 of the dry type in series with a warmer evaporator. 6|, also of the'dry type. In this embodiment, provision is made for by-passing the low temperature evaporator when the warmer temperature evaporator 6| is in operation. The retaining means comprises a chamber 28b similar to the chamber 28 of Fig. 1 but disposed between the float valve'3l and the evaporators, being connected to the former by the conduit 35. The bottom of the chamber 28b' is connected, through a conduit 32b having a valve 341), to a connection 62 between the evaporators 59 and 6|, which connection is disposed at a level above the evaporator 59. A conduit 63 connects theinlet of the evaporator 59 with the chamber 28b at the upper portion of said chamber. The chamber 281) is disposed at a level as high as or higher than the connection 62.

The operation of this embodiment is as follows. When the valve 34b in the conduit 32b is closed, liquid refrigerant is retained in the chamber 261) until the liquid level reaches the connection with the conduit 63 and then flows through said cond'uit to the colder evaporator 59. Only sufficient liquid is supplied under this condition to effect evaporation in the colder e'vaporator 59, the vaporized refrigerant being conducted through the evaporator 6| as in the previous embodiments.

To effect refrigeration in the warmer evaporator, 6|, the valve 341) is opened so as to permit the liquid in the chamber 28b to pass through the con- The liquid first completely fills the evaporator 59 and then enters the evaporator 6| 'to effect evaporation therein.. It will be noted that, with this arrangement, the colder evaporator 59 is flooded while the evaporator 6| is in operation, both the connection 62 and the chamber 28b being disposed at higher levels.

Referring to Figs. 9 to 12, I show the embodiment of my invention which is at present preferred. In this embodiment, the cabinet 64 has a food liner 65, the interior of which is divided by a horizontal insulated partition 66 into a lower,.

relatively cold or freezing chamber 61 and an upper, warmer chamber 68 for preservation of food. This arrangement is described and claimed in theapplication of Milton Kalischer, Serial No.

751,324, filed November 3, 1934. The cabinet is also formed with a machine compartment 69, in this case-shown below the food liner, for contain ing the refrigerating unit.

The colder compartment 61 is refrigerated by an evaporator 1|, comprising a plurality of tubes 12. These tubes are bent into U-shape and the ends thereof connected to a header 13. The tubes are secured to the under surface of the bottom wall portion of the food liner 65. Ice trays 14 may be disposed on the bottom of the food liner to be refrigerated-by the evaporator 1|. This arrangement is described and claimed in the application of J. H. Ashbaugh, Serial No. 751,309, filed November 3, 1934. The warmer compartment 68 is refrigerated by an evaporator 15, comprising a serpentine coil secured to the back surface of the rear wall portion of the food liner portion 65.

The evaporators 1| and 15 are connected to each otherand to the source of liquid refrigerant through a connecting chamber 16, which may be of a cylindrical form disposed with its axis extending vertically, as shown in Figs. 10, 11, and

. 12. This chamber is disposed at a higher level connects with the chamber 16 above the upper end of the conduit 11 and is preferably arranged tangentially as shown in Fig. I I. A conduit 19, which is connected to the chamber 16 below the upper end of the conduit Ti, and which is preferably arranged tangentially as shown in Fig. 11, provides communication with a float valve structure 8!.

In the present embodiment, the refrigerant retaining means is incorporated in the float valve structure 8|, which includes a chamber 82 connected to the condenser through the conduit 21, a valve 83 therein for controlling the flow of refrigerant to the evaporators through the conduit 19,.and a float member 88 for operating the valve 83. The float member 84 comprises upper and lower float elements 840. and 84b, which are fixed in vertically-spaced relation by a stern 840. A weight member 85 is also provided within the chamber 82 and adapted either to rest on the float member84 or to be lifted by a solenoid coil 86.

I also show, in Fig. 9, one form of control system, which may be applied to the other embodiments as well as to the one in Fig. 9. This system comprises. line conductors L1 and L2, the former being connected to one terminal of the compressor motor; -A thermostat 81, disposed within the warmer compartment 68, has one contact connected to the line conductor L2 and the other contact connected to one terminal of the solenoid 88 through a conductor 88, while the other terminal of the solenoid is connected through a conductor 89 to the other terminal of the compressor motor. A thermostat 9| is disposed in the cold compartment 61 and connected,

between the line conductor L2 and the conductor 89. Each of the thermostats 81 and 9| may 0bviously be of any desired type known in the art and for purposes of illustration are shown as comprising bi-metallic strips. Each thermostat is adjustable to provide any desired temperature within the respective compartment. In the illustrated embodiment, each thermostat includes a thumb screw 90, which forms the stationary contact andwhich may be adjusted to vary the temperature setting of the thermostat. It is to be understood that any suitable'form of starting relay for the compressor-motor may be used, as is fully understood in the art, and that any other usual electrical provisions may be made.

The operation cf this embodiment is as follows: Assume that the warmer compartment 88 requires refrigeration while the colder compartment 6? is sufliciently cold, so that the contacts of the thermostat 8'! are closed while the contacts of the thermostat 9| are opened. Thesolenoid 86 and the compressor motor are both energized, the circuit extending from line conductor Li through the motor, the conductor 89, the sole-' noid 86, the conductor 88, and the thermostat 81 tothe line conductor-L2. The solenoid 86 lifts the weight 85, and the motor drives the compressor 22. The float member 84 being relieved of the weight 85 maintains a lower liquid level indicated at 92. The refrigerating system is charged with a suflicient quantity of refrigerant, so that, under this condition, there is suflicient liquid refrigerant conveyed through the conduit 18 to' thechamber 16 to first completely fill the colder evaporator H through the conduit 11. and then to supply sufficient refrigerant to the warmer evaporator 15 for operation thereof. The tangential arrangement of the conduit 19 creates a rotating movement of the refrigerant in the chamber 16, thereby tending to avoid any intermingling with the liquid in the conduit 11 and the evaporator H. The tangential arrangement of the conduit I8 enables liquid to enter said conduit with minimum disturbance of the rotating movement in the chamber 16.

The refrigerating systemonow operates in the usual manner of such apparatus to effect refrigeration of the warmer compartment 68, the liquid refrigerant in the evaporator 15 being vaporized and withdrawn through the conduit l9 to the compressor 22, wherein its pressure is increased. It is then condensed in the con-'- denser and returned to the float chamber 82. Due to the higher temperature maintained in the chamber 88, evaporation of liquid refrigerant in the evaporator 15 efiects a higher pressure in the low side of the system, which higher pressure isimposed on the liquid ,refrigerant in the evaporator H. However, the increased pressure has no effect on the liquid therein, thereby avoiding condensation and heating of the colder chamber 81 which would take place if vapor under the higher pressure were admitted to the evaporator H. Assume now that the temperature in the colder compartment 81 rises to the maximum limit for which the thermostat 9| is set so as to close the contacts thereof for effecting refrigeration of said compartment. The thermostat 9| 'completes a circuit from line conductor L1 through the motor, the conductor 88, and the thermostat 9| to the conductor L2 to eflfect operation of the motor. The solenoid 86 is now deenergized'and releases the weight 85, regardless of whether the thermostat 81 is opened or closed, since, if it is closed, the solenoid is shunted by the thermostat 9|. Accordingly, the weight member 85 rests on the float member 84, so that the liquid level within the float chamber 82 must rise to a higher level, shown at 93, before the float member will rise to open the valve 83. There is thus retained in the float chamber 82 an additional quantity of liquid refrigerant filling the space between the float elements Ma and 8417, which is suflicient to reduce the effective refrigerant charge to the extent that only the colder evaporator II will receive liquid refrigerant. The liquid refrigerant remaining in the evaporator 15 from previous operation and that fllling the vapor space in the top of the header 13 are first evaporated, as described in connection with Figs. 1 and 2, while condensed refrigerant is retained in the float chamber 82 until the upper level 93 is reached. Further operation of the compressor reduces the suction pressure until evaporation in the evaporator Il takes place. 7

The refrigerant system now operates in the usual manner, the refrigerant admitted to the chamber 18 flowing through the conduit I'I into the header 13 to supply the colder evaporator 1|, inasmuch as the upper end of the conduit 11 is at a lower level than the inlet end of the conduit 18, and there is only sufflcient liquid to cause evaporation in the evaporator I The re erature in the colder compartment 61 is reduced to the lower limit for which the thermostat 9I is set, thelatter opens its contacts. If the contacts of the thermostat 81 are open at this time, operation of the refrigeration system ceases but, if they are closed, the solenoid 86 is energized and the motor continues to operate to effect refrigeration of the warmer compartment in the manner first described.

In the control system of Fig. 9, the thermostat 9I may be referred to as the preferred thermostat, since the compartment associated therewith receives refrigeration in preference to the other when both require refrigeration.

In Fig. 13, I show the application of heat exchange apparatus, for transferring heat from the condensed refrigerant in the high side to the vaporized refrigerant in the low side, applied to the embodiment of Figs. 9 to 12. One heat exchanger 94 is connected between the evaporator I5 and the inlet of the compressor, and a second heat exchanger 95 is connected between the evaporators II and I5. The float chamber 82' is divided into an upper space 96 containing the float member 84 and a lower space 91 containing the valve member 83. The condensed refrigerant is conveyed from the upper chamber 96 through a conduit 98 to the heat exchanger 94, and through a conduit 99 to the heat exchanger 95, and then through a conduit IOI to the lower chamber SII. From the latter, it is passed through the valve 83 to the conduit 19 and to the evaporators in the same manner as in Figs. 9 to 12. It will thus be seen that the liquid collecting in a body in the upper chamber 96 is passed in heat exchange relation with the vaporized refrigerant before its pressure is reduced by the valve member 83.

In Fig. 13, I also 'show a storage chamber I02 connected between the warmer evaporator 15 and the inlet of the compressor. Should evaporation take place iri both evaporators at the same time, there may be an excess of liquid returned to the compressor. It is the purpose of the chamber I02 to temporarily retain such liquid to prevent passage thereof to the compressor and possible damage thereto and loss of refrigeration. Operation of both evaporators might take place under certain conditions; for example, if preference were given to the warmer evaporator instead of the colder evaporator and the refrigerator had been shut down for a prolonged period allowing both evaporators to acquire a high temperature, evaporation would take place in both evaporators upon resuming operation of the compressor.

When the evaporator II of Fig. 13 is being refrigerated, the cold dense vapor discharged therefrom passes through the heat exchanger 95, in which it absorbs heat from the warmer liquid refrigerant being supplied to the evaporator II, and in which any'liquid particles carried in suspension are vaporized. The cooling gf the liquid refrigerant means that a smaller pertion thereof is vaporized as its pressure is reduced beyond the valve 83, thereby leaving a greater portion of liquid available for effecting refrigeration in the evaporator 1I. Thus, the refrigerating effect represented by he capa y of the cold vapor to absorb sensible heat is returned to'the evaporator 'II to be utilized therein. The use of this refrigerating effect in the colder evaporator II, rather than in the warmer evaporator I5, is advantageous since it reduces the operating time of the colder evaporator, which is at lower pressure and hence less economical,ratherthanreducing the operating time of the warmer evaporator, which may be effected more economically because it operates at higherpressure. In other words, the return of the refrigerating effect to the colder evaporator results in a greater portion of the operation being effected at the higher economy.

The vapor then passes from the heat exchanger 95 to the evaporator I5, but it does not absorb any appreciable amount of heat therein since its temperature has been raised by the heat exchanger 95. It then passes through the heat exchanger in which it extracts further heat from the liquid being supplied to the evaporator II and is further superheated.

, When the evaporator I5 is being refrigerated,

heat exchange takes place in the heat exchanger 95, but has no effect on the heat balance of the system. The vaporized refrigerant discharged from the evaporator I5, however, absorbs heat from the liquid refrigerant in the heat exchanger 94 and is superheated in the usual manner of such heat exchangers.

In Fig. 14, I show another form of control system which effects energization of an electrical element, such as a coil, when the non-preferred thermostat calls for refrigeration. This control mechanism includes a thermostat T1 which is disposed in the refrigerator compartment that is to have preference, and a thermostat T2 disposed in the other compartment. stat T1 has contacts I02 which are closed and contacts I03 which are opened when the thermostat calls for refrigeration and the thermostat T2 is provided with contacts I04 which are closed when the same calls for refrigeration. The contacts I02 and I04 are connected in parallel in one side of the line going to a starting relay I05. The starting relay is connected to the compressor motor 22 by the necessary number of conductors, including conductors I00 connected to the running winding of the motor. A circuit I01 extends from one of the conductors I06 through a coil I09 and the contacts I03 to the other conductor, I06. A core I09 is actuated by the coil I08. When the control system of Fig. 14 is applied to the apparatus of Fig. 9, the coil 86 and the core 85 constitute the coil I08 and the core I09 of Fig. 14, respectively. When it is applied to one of the embodiments having a valve for determining which "evaporator shall operate, the core I09 is connected to the valve in such manner as to effect refrigeration in the preferred evaporator when-the coil I08 is not energized, and to effect The thermorefrigeration in the non-preferred evaporator partment I3. The core I09 is connected to the valve 34 was toopen the valve when the coil I09 is energized. Assuming that the warmer compartment I3 is calling for refrigeration and that the colder compartment II is not, the contacts I03 and I04 are closed and the contacts I02 are opened. The closing of the contacts I04 effects energization of the compressor motor 22',

and of the conductors I06. The contacts I03 being closed, thecircuit I0! is now closed to energize the coil I08, thereby opening the valve 34 to supply refrigerant to the warmer evaporator I4. When the thermostat T1 in the colder compartment calls for refrigeration, the contacts I02 are closed and the contacts I03 opened. The contacts I02 effect energization of the motor and of the conductors I06, but the contacts I03 prevent energization of the'coil I08, regardless of whether the thermostat T .is calling for refrigeration. The valve 34 is thus closed to cause refrigeration in the colder evaporator I2. When the refrigeration demand of the colder compartment is satisfied, the contacts I03 are closed to enable the thermostat T2 to effect refrigeration .in the warmer compartment. With this control mechanism,

it will be noted that the coil I08 is deenergized to place the apparatus in condition for circulation of refrigerant through the preferred evaporator when neither thermostat is calling for refrigeration. In the apparatus of Figs. 1 and 2, the

valve 34 is closed.

In Fig. 15, I show another form of control mechanism comprising thermostats T1 and T2 which operate contacts I02 and I04, as in Fig. 14, but in which the thermostat T1 closes contacts I03 when calling for refrigeration. In this case, the core I09 is arranged or connected to effect operation of the preferred evaporator when the coil I08 is energized, and to effect operation of the other evaporator when the coil is deenergized, since the contacts I03 close the circuit I01 when the preferredthermostat T1 calls for refrigeration".

The operation of this embodiment is as follows: When the thermostat Tl calls for refrigeration, the contacts I02 effect energization of the compressor motor 22', and the contacts I03 energize the coil I08 to effect operation of the preferred evaporator regardless of whether the other evaporator requires refrigeration. When the.

thermostat T2 calls for refrigeration, the contacts I 04 effect energization of the compressor motor 22, but operation of the evaporator associated therewith is effected only when the thermostat T1 becomes satisfied and opens the contacts I03. In this embodiment, the apparatus is conditioned for operation of the non-preferred evaporator when neither thermostat calls for refrigeration.

The forms of control mechanism shown in Figs. 9 and 14 are suitable for the apparatus shown in Fig. 9 when the colder compartment is to have preference, and for the apparatus shown in Fig. 3 when the warmer compartment is to have pref 'erence, since the coil is energized for operation of the non-preferred evaporator. The control mechanism of Fig. 15 is suitable for the apparatus in Fig. 9 when preference is to be given to the warmer compartment and to the apparatus in Fig. 3 when preference is tobe given to the colder relation, as will be readily apparent from the above description.

In each of the above embodiments, the portions of the low side conduits outside the re-.

frigerated compartments are preferably heatinsulated or arranged in some suitable way to avoid or minimize absorptionof heat. In the embodiments of the invention shown in Figs. 1,

. 7, 9, and 13, it will be noted that the refrigerantretaining means and the valve or other means for selecting the evaporator to be operated are disposed in the high side of the system, so that it is notnecessary to heat insulate the same to prevent condensation of moisture.

therefore, that only su'ch limitations shall be.

placed thereupon as are imposed by the prior art or as are specificallyv set forth in the appended claims.

What I claim is:

1. In refrigerating apparatus, the combination of a low temperature and a higher temperature evaporator, means for condensing the refrigerant vaporized in said evaporators, means for conveying refrigerant from the condensing means to said evaporators in such man'ner that liquid refrigerant flows into the low temperature evaporator in preference to the higher temperature evaporator, and means for selectively producing the effect of increasing the refrigerant charge to the extent of causing liquid refrigerant to fill a substantial portion of the higher temperature evaporator, for effecting refrigeration at relatively high pressure and temperature in the higher temperature evaporator, or producing the effect of decreasing the refrigerant charge to the extent that the higher temperature evaporator receives substantially no liquid refrigerant, for effecting refrigeration at low pressure and tem perature in. the low temperature evaporator.

2. In refrigerating apparatus, the combination of a low temperature and a higher temperature evaporator, means for condensing the refrigerant vaporized in said evaporators, means including a connection to the higher temperature evaporator and a connect-ion at a lower level to the low temperature evaporator for conveying refrigerant from the condensing means to said evaporators, so that liquid refrigerant flows into the low temperature evaporator in preference to the higher temperature evaporator until a predetermined level is reached and then flows into the higher temperature evaporator, and means for selectively producing the effect of increasing'the refrigerant charge to the extent of causing liquid refrigerant -to fill a substantial portion of the higher temperature evaporator, for effecting refrigeration at relatively high pressure and temperature in the higher temperature evaporator, or producing theefiect of decreasing the refrigerant charge to the extent that the higher temperature evaporator receives substantially no liquid refrigerant, for effecting refrigeration at low pressure and temperature in the low temperature evaporator. I

3. A refrigerating system including two evaporators, one of which maintains a lower temperature than the other, said evaporators being so connected and arranged that liquid refrigerant flows into one evaporator until it is full and then into the other, and means for selectively decreasing or increasing the quantity of liquid refrigerant in said evaporators so that when it is decreased there is liquid being evaporated in said first evaporator while the other is dry and when it is increased said one evaporator is flooded and under suflicient pressure to prevent vaporization therein while liquid overflows into and vaporizes in said other evaporator to effect cooling therein.

4. A refrigerating system comprising a low temperature and a higher temperature evaporator, means for liquefying refrigerant vaporized in said evaporators, means for connecting the evaporators and said liquefying means so that with a predetermined effective charge of refrigerant in the system there is sufficient liquid refrigerant in the low temperature evaporator for effecting refrigeration therein while the higher temperature evaporator is dry and so that with a second and greater predetermined effective charge of refrigerant in the system there is sufficient liquid refrigerant in the higher temperature evaporator for effecting refrigeration therein and the low temperature evaporator is filled with liquid refrigerant to prevent condensation therein, and means for selectively varying the effective charge of refrigerant between said predetermined values.

5. A refrigerating system as specified in claim 4, wherein the last-mentioned means comprises means for selectively retaining in a part of the system other than the higher temperature evaporator a quantity of liquid refrigerant equal to the difference between said predetermined values.

6. A refrigerating system having a high side comprising a compressor and a condenser and a low side comprising a low temperature evaporator and a higher temperature evaporator, means for supplying condensed refrigerant from the condenser to the evaporators, the low temperature evaporator being connected to the refrigerant supply means at a lower level than the higher temperature evaporator so that the former has preference in receiving liquid refrigerant and the latter receives liquid refrigerant only when the low temperature evaporator has its full amount of liquid refrigerant, and means for selectively varying the effective charge of refrigerant in the system so that, in one condition, only the low temperature evaporator receives liquid refrigerant and, in a second condition, both the low temperature and the high temperature evaporator receive liquid refrigerant.

7'. A refrigerating system comprising a low temperature and a higher temperature evaporator, means for condensing the refrigerant vaporized in said evaporators, said evaporators and the condensing means being so connected that the low temperature evaporator receives liquid refrigerant in preference to the higher temperature evaporator until it is substantially filled, the system containing a suflicient charge of refrigerant to substantially fill the low temperature evaporator with liquid refrigerant and to supply sufficient liquid refrigerant to the higher temper-- ature evaporator to provide refrigeration therein, and means for selectively retaining in a portion of the system other than the high temperature evaporator a sufficient quantity of liquid refrigerant to cause the higher temperature evaporator to become dry while retaining sufficient liquid refrigerant in the low temperature evaporator to efiect refrigeration therein or releasing the same to effect refrigeration in the higher temperature evaporator.

8. The method of operating a refrigerating system having a low temperature and a higher temperature evaporator which comprises supplying liquid refrigerant to the low temperature evaporator and maintaining the higher temperature evaporator dry for effecting refrigeration in the low temperature evaporator, and supplying liquid refrigerant to the higher temperature evaporator and efiecting evaporation of liquid refrigerant therein at a temperature above the temperature of the low temperature evaporator and at a pressure higher than the pressure corresponding to said temperature of the low temperature evaporator, and at the same time supplying liquid refrigerant to the low temperature evaporator to fill the same for preventing condensation of vaporous refrigerant therein.

9. A refrigerating system comprising a low temperature evaporator and a higher temperature evaporator, said evaporators being so connected that liquid refrigerant flows into the low temperature evaporator in preference to the high temperature evaporator until the former is substantially filled and then flows into the latter,

means for removing the refrigerant vaporized in said evaporators and condensing the same, a high side float valve for controlling flow of refrigerant from said condensing means to said evaporators,

said float valve including a chamber and a float member therein, and means for selectively imposing additional downwarclbias on said float member to raise the liquid level within the chamber to a point where the additional liquid refrigerant retained in the float chamber prevents the higher temperature evaporator from receiving liquid refrigerant.

10. In refrigerating apparatus, the combina-'. tion of a low temperature and a higher temperature evaporator, means for condensing the refrigerant vaporized in said evaporators, and means for selectively supplying liquid refrigerant to the low temperature evaporator and maintor until the same is substantially filled with liquid refrigerant.

11. Refrigerating apparatus as defined in claim 10, wherein the liquid refrigerant in the low temperature evaporator remains in substantially static condition while refrigeration is effected in the higher temperature evaporator.

12. In refrigerating apparatus, the combination of lower temperature and higher temperature evaporators in free communication with each other so that the pressure therein is the same, means for withdrawing vaporized refrigerant from said evaporators and for condensing the same, and means for selectively supplying liquid refrigerant to the higher temperature evaporator and effecting evaporation of liquid refrigerant therein at a temperature above the temperature of the lower temperature evaporator and at a pressure higher than the pressure corresponding to said temperature of the lower temperature evaporator and atthe same time supplying liquid refrigerant to the lower tempera- 5 peration of colder evaporator and ata pressure higher than the pressure corresponding to said temperature of the colder evaporator'and at the same time preventing condensation of vaporous refrigerant in the colder evaporator, and means for supplying liquid refrigerant to the colder evaporator for operation thereof-at lower pressure and at the. same time maintaining the warmer evaporator substantially dry.

14. In refrigerating apparatus, the combination of a colder and a warmer evaporator operating at different times, means for withdrawing vaporized refrigerant from said evaporators and for condensing the same, means for supplying liquid to the colder evaporator for operation thereof at lower pressure while preventing evaporation of liquid refrigerant in the warmer evaporator.

15. In refrigerating apparatus, the combination of a low temperature and a higher temperature cooling element, and means for selectively circulating cooling medium first through the low tema perature cooling element for extracting heat therein and then through the higher temperature cooling element or circulating cooling medium through the higher temperature cooling element for extracting heat therein withoutextracting '0 any appreciable amount of heat in the low temperature cooling element.

16. A frigerating comprising, in combination, a a

cf evaporators, and means for selectively effecting either evaporator, said last-menmeans comprising means for selectively reclosing the elective refrigerant charge inthe 17. In refrigerating apparatus,the combination Q of a comprmr, a condenser. a plurality of evapcraters, a common device for said evaporators, and means forselectively eflecting operation of either evaporator comprising a chamher and means for selectively retaining a quantity of liquid refrigerant in'saidchamben-theretenflonotapredeterminedquantityofliquidrefrigin at a temperature above the temperature of the refrigerant to the warmer evaporator and effectcondenser, a plurality 18. In. refrigerating apparatus, the combination of a colder and a warmer evaporator, a compressor for withdrawing vaporized refrigerant from the evaporators, a condenser, a device for controlling flow of condensed refrigerant to the evaporators, means for conveying refrigerant from said device to said evaporators, said conveying means and said evaporators being connected and arranged so that the evaporators are in communication and at substantially the same pressure at all times, so that liquid refrigerant flows into the colder evaporator in preference to the warmer evaporator and into the warmer evaporator only after the colder evaporator is substantially filled with liquid refrigerant, so that the liquid refrigerant in the colder evaporator may remain in a substantially static condition when the colder evaporator is filled and liquid refrigerant is supplied to the warmer evaporator, so that refrigerant may flow through the warmer evaporator at all times, and so that operation of -the warmer evaporatordepends on whether there is sufficient liquid refrigerant to spill over into the warmer evaporator, and means for selectively increasing the flow of liquid refrigerant to an extent causing the same to spill over into the warmer evaporator or reducing the flow thereof to an extentpreventing such spilling over and thereby depriving the warmer evaporator of liquid refriger t.

In refrigerating apparatus, the combination of a colder and a warmer evaporator element, and means for selectively circulating refrigerant first through the colder evaporator element and extracting heat therein by evaporation of liquid reirigerant at low pressure and then through the warmer evaporator element or circulating refrigerant through the warmer evaporator element and effecting evaporation of liquid refrigerant therein at a temperature above the temperature of the colder evaporator element and at a pressure higher than the pressure corresponding to said temperature of the colder evaporator element without adding an appreciable amount of heat to the colder evaporator element.

.20. In a refrigerating system, the combination of a colder evaporator and a warmer evaporator, means including a compressor and a condenser for effecting evaporation of liquid refrigerant in said evaporators and for supplying liquid refrigerant thereto, means for selectively eifecting evaporation of liquid refrigerant in the colder evaporator by supplying liquid refrigerant to the colder evaporator only or in" the warmer evaporator' by supplying liquid refrigerant to both evaporators, and a connection providing communication between said evaporators at all times, said connection being arranged so that liquid refrigerant flows from said connection to the colder evaporator in preference to the warmer evaporator and therebyserves to prevent flow of liquid refrigerant to the warmer evaporator when said second-mentioned means is adjusted for effecting evaporation of liquid refrigerant in the colder