US2270087A - Refrigeration apparatus - Google Patents

Description

M. G. sHoEMAKl-:R

REFRIGERATION APPARATUS l FIG.

Filed March 24. 193.9

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...BY l O ATr'zoRNl-S? Patented Jan. 13, 1942 REFRIGERATION APPARATUS Malcolm G. Shoemaker, Indianapolis, Ind., assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application March 24, 1939, Serial No. 263,838

8 Claims.

capillary' tube for this purpose is that it depends primarily on the difference in pressure between the ends thereof for regulating the ilow of refrigerant. It is, therefore, apparent that in a refrigerating system, for example of the type wherein the condenser is air-cooled and the evaporator is subjected to varying heat loads, as in the usual domestic refrigerator, the pressure drop across the tube varies considerably, with' the result that the ow of liquid refrigerant through the tube changes.

Assuming for example, that the refrigerator is designed to operate in a room at a temperature of 80 F. and with a cabinet temperature nor` mally maintained at 45 F. If the room temperature now increases, the condenser temperature and pressure will increase and will force an excessive amount of gas through the tube. Likewise, a decrease in cabinet air temperature with consequent decrease in evaporator pressure and decrease in amount of refrigerant pumped will result in an excessive amount of gas .being forced through the capillary tube. This results in a loss of eiiciency, since the gas is merely circulated through the system an'd reduces the usefulness of the work of the compressor.

If the temperature of the room. decreases below 80 F. with subsequent decrease in condensing temperature, the amount of liquid refrigerant passed by the capillary tube will temporarily decrease and liquid refrigerant will back up into the condenser with consequent increase in condensing pressure above a value desirable at this room temperature. This will result in the loss in efficiency of the system and in `addition the pull-down characteristics of the system, that is, the amount of time and work necessary to bring the cabinet down to the desired temperature are also deleteriously effected because the evaporator is starved and the machine is working less efficiently.

increases above 45 F. with consequent increase in suction pressure, the amount of refrigerant pumpedr by the compressor will increase but the amount of liquid passed by the capillary tube will not increase suillciently to take care of the increase in liquid pumped. This also results in starving the evaporator and increasing the discharge pressure with consequent loss in eciency and undesirable effect on the pull-down characteristics of the system.

One object of the invention is to improve the eciency of refrigerating systems utilizing con-v .stantly open flow restricting devices when opcontrols the electric current supplied to the motorv If the temperature of the. air in the cabinet 5:5

erating under varying temperature conditions.

A further object is to .combine a variable flow retarding device with a constantly open flow retarding device to increase the range of maximum efficiencies of refrigerating systems.

A further object, of my invention is to pass refrigerant to the evaporator at such a rate that liquid refrigerant will not appreciably back up in the condenser nor will excessive amounts of gas be passed through the capillary tube.

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

Fig. 1 is a diagrammatic view of refrigerating apparatus embodying my invention;

Fig. 2 is anenlarged sectional view of the 'variable flow retardingbelement of the apparatus;

through a conduit I4 to a condenser I5, shown asV an air-cooled condenser \by way of example, wherein .the compressed refrigerant gas is lc'on. densed by the cooling action of air forced through the-condenser I5 by a fan I6. The condensed refrigerant is conveyed to an evaporator I1 wherein it vaporizes and withdraws heat from the air in an insulated compartment I8, whereupon the vaporized refrigerant is conveyed back to the compressor II through a conduit I9, and the cycle is repeated. An electrical control 2| I2 from a source of electrical power 20, in response to the demands of the evaporator Il for cooling. 'I'he motor runs at substantially oonstant speed when operating. A suitable bulb 22 and a bellows 23 lled with an expansible uid is associated with the evaporator l1 and is responsive to temperature variations thereof. The bellows 23 actuates a switch 24 of the over-travel type to open and close the contacts 25.

The flow of refrigerant from the condenser to the evaporator is controlled by a variable flow impeding device 26 and a capillary tube 21. connected in series therewith. The variable flow impeding device 26 comprises a cylindrical chamber 28 and a cylindrical body 29 located co-axially therein. A helical spring 3| having spaced apart convolutions occupies the space between the cylindrical body 29 and the cylindrical walls of the chamber 28. The spring 3| is somewhat longer than the cylindrical body 29 and is secured at its upper end 32 to the upper portion of the cylindrical body 29 and at its lower end 33 tothe lower portion of the chamber Z8. The cylindrical body 29 has a close working lit within the spring 3| and the spring 3| likewise has a close working t with respect to the cylindrical chamber 28.

It will be apparent that this construction provides a helical passageway for the refrigerant between the convolutions of the spring 3|, and that the cylindrical body 29 is adapted to move downwardly under the iniluence of a difference in pressure between itsupper end and its lower end. This downward movement increases the length of the helical path which the refrigerant is forced to take in the cylindrical chamber 28 and also decreasing the cross-sectional area of this path by the compression of the spring 3|. The end of the tube 21 projecting into the chamber 28 is cut at an angle to prevent the body 29, when in the lowest position, from lblockingr the tube 21. A small portion of the refrigerant will also flow across the convolutions of the spring 3| along the wall of the cylindrical chamber 28 because of the clearance space required between the movable parts of the variable flow mpeding. device 26.

The variable now impeding device 26 is proportioned so that the cylindrical body 29 is in an intermediate position at some assumed average room temperature and at normal loading of the insulated compartment I8. If the temperature of the room in which the refrigerating apparatus is located increases above the assumed average temperature, the temperature of the condenser l5 will also increase and its pressure will increase correspondingly and tend to increase the flow of refrigerant through the flow impeding device 26. The increased pressure will also tend to decrease the rate at which the compressor pumps the refrigerant vapor. The increased pressure at the upper end of the cylindrical body will cause this body to move downwardly and increase the flow impeding effect of the device as previously explained, thereby tending to hold the flow of refrigerant at the rate pumped by the compressor 'I'he opposite action results if the temperature of the room drops below the average. The cylindrical body 29 will then rise and decrease the flow impeding effect of the device.

If, on the other hand, the temperature of the room remains constant and the insulated compartment I8 is loaded with warm supplies orthe door (not shown) of this compartment is left open for a prolonged period, the temperature of the evaporator I1 and correspondingly its pres#- sure will increase thereby loading the compressor piunp more fully at each intake stroke so that a greater mass of the refrigerant vapor is withdrawn from the evaporator |1 than heretofore.

`seatless float valve 4| as the variable flow lmpeding device. The seatless float valve 4| comprises a chamber 42 communicating with both the condenser l5 and with the entrance end of the capillary tube 21. 'Ihe float 43 in the chamber 42 is provided with a tapered needle 44 at its base and a tube 41 of tapered bore cooperating with the needle 44 to progressively restrict the flow of refrigerant from the' condenser l5 to the tube 21 as the float 43 and the needle 44 descend. 'I'he lowermost position of the needle 44 provides the maximum added impedance likely to be desired in the usual operation of the refrigerating apparatus. I'he lowermost position of the needle 44, therefore, Vis not the entirely closed position of this variable flow impeding device. The upper position of the float 43 and the'needle 44 is such that substantially no impedance is added to the impedance of the capillary tube 21.

'I'he operation of the device is as follows:

During the normal operation of the refrigerator in a room of average temperature, the float 43 is supported in'an intermediate position by the refrigerant in the chamber 42. If conditions arise which would ordinarily produce too rapid a flow of refrigerant through the capillary tube 21 such as an abnormally warm room temperature, the level of the refrigerant liquid in the chamber 42 is lowered, the float 43 descends and the tapered needle 44 enters farther into the tube 41 so that the refrigerant ow is held to a normal flow consistent with the pumping of the compressor If the conditions are such as to produce an 'abnormally low flow through the capillary tube 21, such as operating the refrigerator inI a very cold room and loading the insulating compartment I8 with warm foods, the refrigerant level will rise in the chamber 42 and raise the float 43 together with the tapered needle 44 to decrease the impedance of the lioat valve 4| to the flow of refrigerant.

It will be apparent from the above that this invention provides a variable Ilow control device which together with the capillary tube impedes the flow of refrigerant to a varying degree and that this device increases the eiiciency of a refrigerating system embodying a capillary tube. It will be further apparent that the variable flow impeding devices of this invention do not destroy the automatic unloading characteristic of the capillary tube because the devices are continuously open.

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 limitations shall be placed thereupon as. are imposed by the prior art olr as are specifically set forth in the appended c aims.

What I claim is:

1. In refrigerating apparatus, the combination of a compressor-for pumping refrigerant, a condenser, an evaporator, and means for impeding the flow ofvrefrigerant between the condenser and the' evaporator, said means comprising a conduit of variable cross-sectional area, amovable body responsive to the pressure differential of the refrigerant across said body, said body controlling the conduit to vary its cross-sectional area to provide a flow varying substantially with the quantity of refrigerant pumped by said compressor regardless of the .pressure differential between the condenser and the evaporator. g

2. In a refrigerating system, the combination of a compressor, a condenser, an evaporator, a constantly open ow-impeding device having unvarying friction-producing surfaces, and a float valve, said float valve and said ow-impeding device being connected in series beween the condenser and the evaporator, said float valve comprising a conduit having a continuously open elongated passage, a nely tapered needle projecting into said elongated passage, and a oat controlling the position ofsaid needle so that a relatively large movement of said float produces a relatively small change in the cross-sectional area of said passage.

3. In refrigerating apparatus, the combination of a compressor for pumping refrigerant, said compressor operating at substantially constant speed when active, a condenser, an evaporator,

a constantly-open flow-impeding device having.`

unvarying friction-producing surfaces, and a continuously open float valve connected in series with the flow-impeding device between the condenser and the evaporator, said oat valve comprising a valve seat, a float, and a nely-tapered needle actuated by said oat and closely fitting within but out of contactwith at least portions of said valve seat so that a large movement of said float produces a relatively small change in the cross-sectional area between the needle and the valve seat.

4. In refrigerating apparatus, the combination of a compressor, a condenser, an evaporator, a ow-impeding device comprising a cylindrical chamber, a helical spring having spaced-apart convolutions in said chamber, said spring tting A closely against the interior cylindrical .walls of said chamber, a cylindrical body within said spn'ng and closely fitting the interior surface thereof, one end of said spring being secured to the cylindrical chamber adjacent one end thereof and the other end of said spring being secured to the cylindrical body, a constantly-open flowimpeding device having unvarying friction-producing surfaces connecting the evaporator and the portion of the cylindrical-chamber adjacent the securement of the spring thereto, and a second conduit connecting the compressor to the portion of the cylindrical chamber adjacent the securement of the spring to the cylindrical body, said first-named flow-impeding device forming a variable restricted lpassage forv refrigerant flowing therethrough.

5. In refrigerating apparatus, the combination of a periodically-operated compressor for pumping refrigerant, a condenser, an evaporator, a

constantly-open ow-impeding device having unvarying friction-producing surfaces, and a second that said second floW-impeding device affords a substantially uniform flow oi refrigerant through said first-named flow-impeding devicewhen the compressor is operating corresponding substantially to that delivered by said. compressor over the normal range of operating conditions of said apparatus, said movable body being responsive only to a condition of the refrigerant in said second flow-impeding device.

6. In refrigerating apparatus, the combination of a periodically-operated compressor for pumping refrigerant, a condenser, an evaporator, a constantly-open now-impeding device having unvarying friction-producing surfaces, and a second flow-impeding device, said second flowimpeding device and said first-named ilow-impeding device being connected in series between the condenser and the evaporator, said second ow-impeding device having a continuously-open elongated passecond flow-impeding device for varying the friction-producing surface of said elongated passage, so that said second ow-impedng device affords substantially uniform flow of refrigerant through said first-named flow-impeding device vwhen the compressor is operating corresponding substantially to that delivered by said compressor over the normal range of operating conditions of said apparatus.

'7. In a flow-restricting device for refrigerating apparatus, the combination of a cylindrical chamcylindrical' body, and a constantly-open flowimpeding device having unvarying friction-pro-l ducing surfaces communicating with one of said openings for connection in series with said cylin drical body.

' 8. The combination as claimed in4 Vclaim 'i wherein the spring,"when at rest, holds the cylindrical body within said spring with the unsecured end of the cylindrical body spaced from the secured end of the spring. i

' 1 MALCOLM G. SHOEMIAKER.

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