US2586454A - Refrigerating machine or heat pump unit of the multiple compression type - Google Patents

Description

Feb. 19, 1952 "r BRANDIN 2,586,454

REFRIGERATING MAC HINE OR HEAT PUMP UNITS OF THE MULTIPLE COMPRESSION TYPE Filed June 13, 1949 2 SHEETS-SHEET l n VIIIIIIIIIJ 1 r 'llllllllllllll Feb. 19, 1952 T. BRANDIN REFRIGERATING MACHINE OR HEAT PUMP UNITS OF THE MULTIPLE COMPRESSION TYPE 2 SHEETS-SHEET 2 Filed June 13, 1949 1 E f l 9 equal in both cases.

Patented Feb. 19, 1952 REFRIGERATING MACHINE OR HEAT PUMP UNIT OF THE MULTIPLE COIVIPRESSION TYPE Tore Brandin, Finspong, Sweden, assignor to Svenska Turbinfabriks Aktiebolajet Ljungstrom, Finspong, Sweden, a Swedish joint-stock company Application June 13, 1949, Serial No. 98,723 I In Denmark June 30, 1948 1 Claim. (01. 62-3) Thepresent invention relates to refrigerating machines, and mor particularly to refrigerating machines of the compression type.

In order to allow a refrigerating machinery of the compression type to operate at acceptable efiiciencies in the event of a great difference between the condensing temperature and the evaporating temperature is is necessary to effect the compression in two or more stages. Hitherto known refrigerating machineries of this type in which two compression stages are used, comprise as a rule either two compressors or a single special compressor the volume of stroke of which is afforded by a high pressure cylinder or cylinders and a low pressure cylinder or cylinders. An example of such a well known refrigerating machinery having two compressors is diagrammatically illustrated in Fig. 1 of the accompanying drawings. Referring to this figure, the reference character I-I indicates the high pressure compressor, L is the low pressure compressor, HF is the evaporator of the high pressure system, and LF is the evaporator of the low pressure system. The two pressure systems are connected in cascade, the evaporator HF of the high pressure system cooling the condenser of the low pressure system, while the evaporator LF of the low pressure system yields the cooling effect desired.

The present invention has for its object to provide a refrigerating machinery of the compression type or a heat pump unit, the characteristic feature of which resides in the use of a single compressor alternately operating as a high pressure compressor and a low pressure compressor (if desired, also as an intermediate pressure compressor if more than two compressor stages are used). Thus, in other words, the invention resides in replacing the well-known division of the compression on space basis by a division of the compression on time basis.

A comparison between a plant according to this invention and a well-known plant, such as, for instance, the cascade coupled two-stage plant above mentioned, shows amongst others that the refrigerating capacity will be the same in both cases provided the total volumes of stroke are It is thus seen that the relation between the running periods of the plant according to the invention will correspond to the relation between the volumes of stroke of the It is thus seen that under the conditions above mentioned the invention affords a plant equiva'- lent with a well-known plant having two compressors but only requiring a single compressor of standard type. This in its turn permits a considerable reduction of the cost of erection of the plant and a more simple control as compared with a unit having two separate compressors or a special type of two stage compressor.

The invention is illustrated by some examples in Figs. 2-5 of the accompanying drawings. Fig. 2 is a diagrammatic view of a principal scheme for an intermittently operating two stage machinery according to the,invention. Fig. 3 is a working diagram for the unit shown in Fig. 2. Fig. 4 is a diagrammatic View of a fully automatic refrigerating unit according to the invention. Fig. 5 is a diagrammatic view of a heat pump unit to which the present invention has been applied.

With reference to Fig. 2, the reference numeral l indicates the compressor, which may be of standard type, as hereinbefore stated. Extending from the compressor is a circulation conduit 2 leading to the condenser coil 3, from there via an expansion valve 4 to an evaporator coil 5 and thence via a shut off valve 6 back to the compressor. Inserted in a. shunt pass said valve 4 is a shut off valve 1 and inserted in a shunt past valve 6 is a second evaporator coil 8 between an expansion valve 9 in front of the coil and a shut off valve l0 behind the coil. The evaporator coil 5 is located in a heat insulated receptacle A and the evaporator coil 8 is disposed in a heat insulated receptacle B.

This refrigerating unit operates in two time spaced stages, hereinafter referred to as the high pressure stage and the low pressure stage, respectively. In the high pressure stage the shut off valves 1 and H] are closed and the shut off valve 6 is open. I J

The compressor pumps hot high pressure gas into the coil 3, where the gas condenses. The liquid resulting passes through the expansion valve 4 and evaporates incoil 5. The evaporated refrigerant is drawn back to the compressor via valve 6. After the heat magazine A is cooled to a temperature aboutmidway between the condensing temperature and the evaporating temperature desired in the low pressure stage, the low pressure stage starts.

h Shifting to the low pressure stage is'effected by-opening the valves land I!) and closing 'the valve 6. The compressor 1 forces the evaporated refrigerant through coil 3 and via valve 1 to coil 5 now acting as a condenser. The condensate back to the low pressure stageandiso on. It is" thus seen that the heat is pumped from B torA and thence to the condenser 3 which delivers its heat contents to air or cooling water.

The relation between the durationsof .the periods at a given condensing; temperature-in the condenser 3 and a given evaporating temperature in the evaporator 8 is determined substantially by the average temperature prevailingx-the' heat magazine A. The real duration of thepe riod depends on the heat capacity of the insulated volumes A and B and the allowable variations of; temperaturetherein. In order to obtain within a-small volume asufficient heatcapacity the coils 5 and 8 may be immersed into a. brine of such a-cQncentratiOn. as to allow accumulation of cold by ice production. In connection with the-receptacle B incoming and outgoing conduits are-indicated at H and I2, respectively, in Fig. 2, belonging" to a conduit for passing brine between a cooling place and the receptacle 3.

If an eutectic brine is used, then an approximately, constanttemperature may be obtained in themagazines A and B.

Fig. 3 shows a- TS-diagram for indicating the changes of stat during the two working stages appearing at the plant shown in Fig. 2, and a similar diagram is obtained in case of a wellknown plant in cascade connection; it is thus seen that the plant according to the invention from thermodynamic point of view is equivalent to the well-known plant.

In order to reduce-the leakage of heat through the insulations it is preferred. to arrange the receptacle A'concentrically aroundthe receptacle B', so that B, which affords the lowest temperature will bein the centre. Fig. 4 illustrates such ae-unit and alsoshows an example of an automatic plant.

In Fig; 4 the same reference characters are used as in Fig. 2 to indicateelements common toboth plants. It is assumed that, for the rest, the system shown in Fig. 4 may be best understood from a description of its operation which is, principally, equal to that described in connection with Fig. 2.

Athermostat I3 is adjusted to maintain the temperature in A between two predetermined limits. When the machinery operateson the low pressure stage the flow. of the refrigerant takes placeas indicated by the full arrows. As a result, the magazine A is heated and the magazine B is. cooled. As soon as the temperature in A reaches the upperlimit forwhich the thermostat i3 .is-adjusted, thethermostat operates the solenoidv valves 1 and 6 for shifting to the high pressurestage, during which the flow ofthe refrigerant takes place in the direction indicated by the dottedarrows. During the high pressure stage the magazine Ais cooled, and this continues until. the temperature in. A reaches the lower limit determined by the thermostat which then controls shifting to thelow pressure stage.

AlSOrlIlIGSDBCt of the magazin ;Bfa thermostat M-is provided for maintaining. thetemperature in B-within.thelimits desired- Said thermostat controls the magnet valve 10. If thetem- 4 is? perature in B rises beyond the predetermined upper limit, then the thermostat opens valve l0; if the temperature sinks below the predetermined lower limit, the thermostat closes valve I0.

It is to be noted, however, that-the thermostat l4 and the valve 10 are required only if an exact adjustment of the temperature in B is desired, since a high and low pressure relay I5 for starting and stopping the compressor also controls the temperatureprevailing in the magazine B.

In addition to the elements above referred to, the unit shown in Fig. 4 includes a motor l6 for driving the compressor l and a rheostat I! for this motor. Furthermore, an oil separator may be inserted in theconduit 2 behind the compressor, as indicated at l8.

Instead of'efi'ecting the shifting between the low pressure stage and the high pressure stage by means of thermostat controlled valves, as hereinbefore described with reference to Fig. 4. other controlling. mechanisms may be used, as for instance, a time clock, which eflects shifting from one pressure stage to another at'certain predeterminedintervals. Another expedient is toutilize the variations of the evaporizing pressures for determining the operative periods by the aid of pressure relays or magnet valves.

In a-refrigerating machine heat is absorbed at low temperature in the evaporator and. pumped to a higher temperature level where the same amount of heat together with the heat produced by the compression is supplied tothe condenser. If, instead of the cooling. eifect obtained in the evaporator it is desired to utilize the heateffect obtained in the condenser, the plant is generally termed a heat pump. As there is no difference of principal nature as regards the operation of those. two kinds of machinery, it is evident that theinvention may also be applied to heat pumps. An example of such a plant is illustrated in Fig. 5 in adiagrammatic way'similar to that. used inFig. 2..

In Fig. 5 the numeral l indicates the compressor of the plant. Leading from said compressor is a conduit 2 which extends to and through the condenser 3 and from there via an expansion valve 4 to the evaporator coil 5..fr0m where the conduit via theshut ofi' valve 6 leads back to the compressor. As in Fig. 2 an evaporator coil 8 is inserted in a shunt past valve 6, saidv shunt also containing an expansion valve 9 in front-of said coil andashutofi valve (0 behind thecoil. In this case coil 5 is positioned inan insulated tank B which represents a heat magazine, and. coil 8 is positioned in a magazine A-which may comprise some suitablesource of heat, as for instance, sea orriver water.

During the low pressure stage heat is pumped by the compressor from the source of heat A directly through an additional conduit 20 intothe coil 5 in the heat magazine B, as indicated by thefull arrows. During-the high pressure periods theflow takes place in-the direction indicated by the dotted arrows. It is thusseen that the heat is pumped from source A via magazine B to the condenser 3where the heat of the warm water. is recovered to.be used forheating purposes,.as for instance, by means of radiatorsfor room heating.

Ifin case of heat pumps for room heating purposes .the intermediate temperature in. the magazine 13 isadjustedtoayalue approximately equalftothat of theroom-temperature (the tank 35 may beassumed to be locatedin acellanhaving a temperature approximately. equal to. the

room temperature) the losses to which the heat magazine B may be subjected may be, practically, fully eliminated. The heat magazine may, if built in a suitable size, be utilized for equalizing of variations of load.

What I claim is:

In refrigerating machinery of the compression type for operation at two pressure stages, the combination of a compressor for alternate operation as a low pressure compressor and as a high pressure compressor during successive periods, a circulation system for the refrigerant acted on by the compressor, two evaporators includedin said circulating system, one for each pressure stage, two concentric 'cold magazines concentrically surrounding each other, the inner magazine being provided for enclosing the evaporator belonging to the low pressure stage and for storing the cold developed during said stage, the outer magazine being provided for enclosing the evaporator belonging to the high pressure stage and for storing the cold developed during said high pressure stage, means for utilizing during the low pressure period, at least partially, the cold stored in the outer magazine during the high pressure period, a condenser provided in the circulation system in front of the evaporator of the high pressure stage and its magazine, and

6 means adapted upon the shifting from the high pressure stage to the low pressure stage by setting the evaporator of the low pressure stage into operation, to effect a simultaneous settin of the evaporator of the high pressure stage into operation to act as a condenser for the low pressure stage.

TORE BRANDXN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,123,497 Buchanan July 12, 1938 2,185,515 Neeson Jan, 2, 1940 2,252,979 Reiter et a1. Aug. 17, 1941 2,293,482 AmbrOSe Aug. 18, 1942 2,482,569 Zearfoss Sept. 20, 1949 2,500,688 Kellie Mar. 14, 1950 2,515,825 Grant July 18, 1950 FOREIGN PATENTS Number Country Date 123,576 Switzerland Dec. 3, 1926 440,306 Great Britain Dec. 24, 1935

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