US2603954A - Variable output refrigeration system - Google Patents

Description

July 22, 1952 w. E. DAV IS 2,603,954

VARIABLE OUTPUT REFRIGERATION SYSTEM Filed Nov. 15, 1950 |a F 2s 23 24 2s I 2| j v l2. J

n 9 -l0 22 I William E. Davis INVENTOR.

,4 TTOR/VEY Patented July 22, 1952 UNITED STATES PATENT OFFICE VARIABLE OUTPUT REFRIGERATION i r SYSTEM William E. Davis, Houston, Tex. v j Application November 15, 1950, Serial No. 195,885

1 V This invention relates to control apparatus for compressors of the gaseous fluid type andmore particularly tov control apparatus for air conditioning and refrigerating systems of the compression type in which the system, including the compressor, uses a condensable gas which is kept confined in the system. The general object of'this invention is toprovide a simple and improved'apparatus wherein the input of mechanical energy'to thev compressor and the transfer of thermal energy of the system can be controlled without stopping; the compressor or without varyingthe speed of the compressor.

It isan object or this inventionto provide a system of controlling and limiting the amount of mechanical energy used to drive the compressor and the amount of thermal energy transferred by the system, even though the compressor may be driven by a source whichnecessitates its operation over a range of speeds such as when used in connection with air conditioning or refrigerating apparatus in automobiles, trucks, railway coaches, and the like, where the compressor is driven from the motor or the wheels of the vehicle.

'It is another object of this invention tocontrol input of mechanical energy and the transferof thermal energy so that it will approach the required load conditions without stopping or varying the speed of the compressor.

Another object of this invention is to stop or limit the flow of gas through the valves of the compressor, without varyingthe speeds of 'the compressor, so that the amount of gas flowing through them will be reduced when the amount of refrigerationrequired is reduced, rather than increasing the amount of gas passingthrough the compressor as isdone bythe by-pass systems Where the outlet of the compressor is led back into the inlet of the compressor raising the back pressure and increasing the total amount of gas passing through the compressor.

Another object of this invention isto limit the power input and output ofthe compressor so that it will not be loaded beyond itsrated capacity even though it should be run at a speed which would normally causeitto overload and break down. I

Another object of this invention is .to keepthe refrigeration system itself fromibecoming overloaded or freezing up even though the speed of the compressor should exceed its normal speed.

Another object of this inventionlis to provide a method of reducing the starting load on the.

, .9 Claims (01. 62-117.;1)

compressor used in a refrigeration system of the closed compression type.

It is another object of thisinvention to provide an improved system of controlling the load of a compressor without causing excessive changes in pressure in the low side of the systemas when the gas is by-passed from the high side to the low side.

It is also an object of this invention to provide an improved system for completely shutting off the refrigerating system where it is impractical to stop the compressor driving motor-such as when largemotors are used orwhen the motor is also used for other purposes.

Other and further objects are apparent when the specificationis considered in connection with the drawings in which:

Figure 1, the single'figura'partially in section,

and partially diagrammatic, represents a typical compressor type refrigerating system employed in connection with this invention.

The refrigerating system I includes therewith a compressor! having an oil sump 3 tobe hereinafter described in connection with specific features of this invention, a shaft-4 journalled in the compressor body, a crank arm 5 rigidly connected to the shaft d, a piston rod 6 'pivotally connected to the crank 5 at l and to the piston 9 at -8. The rotation of the shaft 4 causes the piston'to reciprocate in the cylinder l0. On the down-stroke oi the piston the inletvalve l I is opened so the fluid may enter the cylinder, and on the up-stroke of the piston 9 fluid is discharged upwardly through the outlet valve I2 to pass out into the discharge line l3. a

The refrigerating system herein described operates conventionally by deliveringthe fluid in the form of a hot high pressure gas into the condenser coils M where the heat is removed therefrom with the result that the gas liquefies and is delivered, preferably by gravity, into the receiver i5 From the receiver I5 the liquid refrigerant flows outwardlyinto the connectin'g'line I6 to the expansion valve l1. This valve I1 is of the'conventional type designedto receive a flui'd'at a higher pressure and to deliver the fluid therefrom at a lower pressure. I r

From the expansion valve I! the refrigerant passes into the evaporator means, shown herein as a series ofcoils 18. These coils pass through is desired to remove a a space ill from" which it quantity of heat. i

The lowering of the refrigerant pressure re sulting from" its passage through the valve I"! causes it to evaporate and to absorb heat from the space I9 in which the evaporator 18 is located. It then passes into the return line 20.

The return line 20 connects at 23 into a valve means 24 and the outlet side of the valve means 24 is connected at 25 into the inlet chamber 2! of the compressor. The path of refrigerant then leads through the valve H into the cylinder l9 and thence through the valve I2 into the outlet chamber, 28*wh'ich communicates with the high pressure,-or discharge line l3, as has been hereinabove described.

The connection 21 is shown inserted in the re-- compressor, the total amount of refrigeration produced in the closed system will also be directly turn line 20, outwardly of, or moreproperly on the inlet side of the valve means 24. Aline 22 from H this connection 2| leads to the sump 3.

The compressor 2 should be a typewhichhas no direct or internal connection-from the inlet port or inlet chamber 21 or'iniet'vaive I! to the enclosed oil sump 3. shown as a conventionaLsingle cylinder'piston type with valves II and 12 located in the head plate 26. A multiple cylinder compressor may also be used or any other typeof compressor which has a closed oilsump and has no connection between the oil sump and the inlet of the compressor. However, a conventional piston type of compressor with inlet valve located on, or

in the piston, cannot be used. Any prime mover or source of power maybe usedto actuate the compressor. 3

Line, 20. from the evaporator, i8 is connected to the. control .valve means 24. This means may be a simple manually controlled valve of theglobe, gate, or needle valve typewhich may be either completely or partially closed. The valve means 24 also may be a solenoid operated valve which may be closed or partially'closed by any .of the variable conditions availablefor controlling the valve means. These variables may be the temperature of the space the evaporator is cooling, the discharge pressure, thespeed of the compressor, the suction pressure, the flow of gas through the suction o'rdischarge line, or any other variableswhich need belimited or controlled. An automatic-mechanical valve may be employed which is controlled by any of the available variables, or also a combination ofone or more of the above mentioned types of valves may be used, eithersingularly or in multiples.

Line 22 is connectedto line 20 preferable at 23 near the inlet to valve means 24 so that it will provide a gas pressure in the oil sump 3 which will not change rapidly when valve means 24' is operated. This line 22 is arranged so that any oil which may leak into the system will be returned, preferably by gravity, to the oil sump 3.

For convenience pressure in that portion of the system between the downstream side of the control valve 24 and the inlet valve 1 l is referred to as control pressure. 7

When valve means 241s shut pass through the compressor so there will be no refrigerant circulating through the system which will cause it to become inoperative until it is desired to start theprocess again, at which time valve means 24 is opened and the gas'is again allowed to flow. The oil then will be returned through line 22 (or 22). The energy consumed by the compressor when the valve is closed will be only that required-to overcome the losses of is partially closed, the amount of energy consumed by the compressor and the amount of heat off no gas will This compressor "2 is proportional to the weight or mass of the gas passing through the compressor. The mass of gas passing through the compressor will be determined by the mass of gas forced into each cylinder-or compression chamber at the time of maximum displacement; such maximum displacement occurring at the bottom of the stroke in a cylinder and piston type compressor.

In the range of pressures. in which 7 the inlet of the compressor operates, the density of the gas which is relatively small at this point) varies directly as the absolutepressure (Boyles law).

As the volume of gas in the cylinder or chamber,

at each time of maximum displacement, is constant, then the density. of .the gas will be directly proportional to the mass.-: ,-From this it follows that the mass or weight of gas flowing through the compressor is directlyfproportional to the absolute pressure of the ga'sat the input. Thus in a refrigeration system of this type, using a given compressor and refrigerant, the amount of refrigeration produced per stroke or revolution ofthe compressor will be'directly proportional to the absolute pressure on theinlet chamber.

Therefore, a system as outlined hereinabove has been developed wherein the inlet pressure to the compressor-may be varied without causing these variations in pressure to be transferred directly to the oil sump where the lowering of the pressure may cause such difficulties as foaming of the oil, leakage of air into the system, and inoperation of the oil pump, if used.

Broadly, therefore, this invention considers varying the amount of heat transferred in a refrigeration system and the input of mechanical energy thereunto by controlling the pressure on the inlet of the compressor, without lowering the crankcase or evaporator pressure.

What is claimed is:

1. A closed refrigeration system including a compressor having an inlet, a discharge line, and a sump for compressor oil, a refrigerant to'be supplied to the compressor through the inlet as a' low pressure gas, compressed' therein and expelled through the discharge line as a high pressure gas, a condenser connected to the discharge line, means connected to the condenser providing a restricted passage to receive refrigerant from' the condenser andto discharge itat a lowered i said return line, to provide a controlpressure between said control valve and the compressor inlet I isolated pneumaticallyand hydrostatically from the sump so that the control pressure is not communicated directly to the sump, andmeans pro- ':-viding a passage-from the'su'mp to a gasfllled (neglecting the temperature change char e. and ani il.r ta ningspace. a condenser h v n i i let c nnect d to a d compre discharge, meansconnflctedto.thQDlltlet of said condenser providing arestricted passage from the condenserand,,.-an;,evaporator connected -to the ,outlet from'said passa e a-returnlinefrom theevaporator to the compressor inlet, a control valverzmeans, interpose i sai retu n .line. n

' means providing a passage from: the oil retaina Iowpressure gas, compressed therein,-and:'expelled through the discharge line as a high pressure gas, a condenser connected to the discharge line, means connected to the condenser providing a restricted passage to receive the refrigerant from the condenser and to discharge it at a lowered pressure, an evaporator connected to the outlet from said passage to receive the refrigerant therefrom and permit it to evaporate and absorb heat from the space around the evaporator, a return line from the evaporator to the compressor inlet, a control valve means interposed in said return line to provide a control pressure space between said control valve and the compressor inlet isolated pneumatically and hydrostatically from the sump so that the control pressure is not communicated directly to the sump, said sump being in communication with a gas filled portion of the system downstream from the compressor discharge and upstream from the control valve whereby a pressure other than the control pressure is exerted on the sump and any oil which may leak into the system will be restored to the sump.

3. In a refrigeration system wherein apparatus is provided including a piston-typecompressor with one end ofa piston therein in communication with a gas-tight crankcase for the compressor which is adapted to contain a lubricating oil and wherein the opposite end of said piston is in communication with suction and discharge conduits controlled by conventional compressor suction and discharge valves, respectively, and wherein said suction and discharge conduits are respectively connected to evaporating and condensing means of a closed refrigerating system, the improvement which comprises in combination therewith of a flow control means in said suction conduit and a conduit between said crankcase and the suction conduit upstream of said control means.

4. The apparatus of claim 3 wherein the point at which said last mentioned conduit connects to said suction conduit is at a vertical level above its inlet to said crankcase whereby a lubricant in a refrigerant passing through said compressor can flow to said crankcase.

5. A compressor system which comprises, in combination, a piston-type compressor having one end of a piston therein in communication with suction and discharge conduits controlled by conventional compressor suction and discharge valves, respectively, and having a sump in communication with the other end of said piston and adapted to contain a lubricating oil, a flow control means in said suction conduit and a conduit between said sump and said suction conduit upstream of said flow control means.

6. A refrigeration system comprising in combination with a prime mover having duties requiring speeds of operation independent of the amount of refrigeration required, a compressor connected to said prime mover to be driven thereby at speeds dependent on the speed of said prime mover and having an inlet, a dising space to a portion of the system downstream from :said restricted; passage and upstream from the control valve, whereby intake to said compressor may be controlled independently of its speed without rapid variation in the pressure in said oil retaining space.

7. A refrigeration system comprising in combination with a prime mover having required speeds of operation independent of the amount of refrigeration required, a compressor connected to said prime mover to be driven thereby at speeds dependent on the speed of said prime mover and having an inlet, a discharge, and an oil retaining space, a condenser having its inlet connected to the discharge from said compressor, means connected to the outlet of said condenser providing a restricted passage from the condenser, and an evaporator connected to the outlet from said passage, a return line from the evaporator to the compressor inlet, a control valve means interposed in said return line to provide a control pressure space between said control valve and the compressor inlet isolated pneumatically and hydrostatically from the oil retaining space so that the control pressure is not communicated directly to the oil retaining space, said oil retaining space being in communication with a gas filled portion of the system downstream from the compressor discharge and upstream from the control valve whereby a pressure other than the control pressure is exerted on the oil retaining space and any oil which may leak into the system will be restored to the oil retaining space.

8. Refrigeration apparatus adapted for use in a vehicle comprising a compressor having a driving connection adapted to be connected to a part on said vehicle which moves with respect to the remainder of the vehicle as the vehicle travels from place to place, whereby said compressor will be driven at speeds depending upon the speed of movement of said part of the vehicle to which it is connected, said compressor having also an inlet, a compression space, an outlet, and an oil retaining space, a control valve connected to the inlet for controlling the intake to said compressor, and connections to the entrance of said valve and from the outlet of said compressor, said connections, valve, compression space, inlet and outlet, providing a refrigerant passage, said oil retaining space being isolated from that portion of the refrigerant passage between said control valve and said compressor outlet and being in communication with said refrig erant passage beyond the limits of that portion 7 ing space, a control valve connected to the inlet for controlling the intake to said compressor,

connections to the inlet of said valve and from' the outlet from said compressor, said connections, valve, compressor space, and inlet and outlet providing a refrigerant'passage said oil rei V taming space being isolated from that portion 7 REFERENCES CITED 7 of the refrigerant passage we Said control The following references are of record in the valve and said-oompressor outlet and said 011 fil f thi thtyre'tainingspace being in communication with 5 said refrigerant passage beyond. the limits of that UNITED STATES PATENTS portion of the; refrigerant passage downstream Number Name Date from said control valve and upstream from said 1,698,941 Davenport Jan. 15, 1929 compressor out1et.- i I a 7 1,768,602 Hull July 1, 1930 1 7 l 10 2,061,599 :Smith Nov. 24, 1936 E, DAVIS; 2,301,656 Hirche /NOV. 10, 1942

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