CA1242086A - Highly efficient flexible two-stage refrigeration system - Google Patents
Highly efficient flexible two-stage refrigeration systemInfo
- Publication number
- CA1242086A CA1242086A CA000471641A CA471641A CA1242086A CA 1242086 A CA1242086 A CA 1242086A CA 000471641 A CA000471641 A CA 000471641A CA 471641 A CA471641 A CA 471641A CA 1242086 A CA1242086 A CA 1242086A
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- CA
- Canada
- Prior art keywords
- stage
- stage compressor
- compressors
- inter
- compressor
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B5/00—Compression machines, plants or systems, with several evaporator circuits, e.g. for varying refrigerating capacity
- F25B5/02—Compression machines, plants or systems, with several evaporator circuits, e.g. for varying refrigerating capacity arranged in parallel
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B1/00—Compression machines, plants or systems with non-reversible cycle
- F25B1/10—Compression machines, plants or systems with non-reversible cycle with multi-stage compression
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B41/00—Fluid-circulation arrangements
- F25B41/20—Disposition of valves, e.g. of on-off valves or flow control valves
- F25B41/24—Arrangement of shut-off valves for disconnecting a part of the refrigerant cycle, e.g. an outdoor part
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2400/00—General features or devices for refrigeration machines, plants or systems, combined heating and refrigeration systems or heat-pump systems, i.e. not limited to a particular subgroup of F25B
- F25B2400/07—Details of compressors or related parts
- F25B2400/075—Details of compressors or related parts with parallel compressors
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2400/00—General features or devices for refrigeration machines, plants or systems, combined heating and refrigeration systems or heat-pump systems, i.e. not limited to a particular subgroup of F25B
- F25B2400/13—Economisers
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2400/00—General features or devices for refrigeration machines, plants or systems, combined heating and refrigeration systems or heat-pump systems, i.e. not limited to a particular subgroup of F25B
- F25B2400/16—Receivers
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2400/00—General features or devices for refrigeration machines, plants or systems, combined heating and refrigeration systems or heat-pump systems, i.e. not limited to a particular subgroup of F25B
- F25B2400/22—Refrigeration systems for supermarkets
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2600/00—Control issues
- F25B2600/02—Compressor control
- F25B2600/021—Inverters therefor
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B30/00—Energy efficient heating, ventilation or air conditioning [HVAC]
- Y02B30/70—Efficient control or regulation technologies, e.g. for control of refrigerant flow, motor or heating
Landscapes
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Mechanical Engineering (AREA)
- Thermal Sciences (AREA)
- General Engineering & Computer Science (AREA)
- Control Of Positive-Displacement Pumps (AREA)
- Air Conditioning Control Device (AREA)
- Control Of Positive-Displacement Air Blowers (AREA)
- Separation By Low-Temperature Treatments (AREA)
- Devices That Are Associated With Refrigeration Equipment (AREA)
- Structures Of Non-Positive Displacement Pumps (AREA)
Abstract
HIGHLY EFFICIENT FLEXIBLE TWO-STAGE REFRIGERATION SYSTEM
Abstract of the Disclosure A refrigeration system characterized by a first stage booster compressor feeding multiple parallel connected second stage compressors in an otherwise conventional closed loop refrigeration system utilizing an economizer between the condenser and evaporator and returning economizer vapor to the inter-stage pressure point between the first stage and second stage compressors operates in a very flexible and highly efficient manner by driving the booster, first stage compressor at variable speed and the second stage compressors at constant speed, at maximum capacity, with those machines incapable of being unloaded. The control system utilizing a sensor for sensing evaporator pressure, evaporator temperature or suction pressure, varies the speed of the drive motor for the first stage booster compressor to initially slow down the booster and secondly connect or disconnect the second stage compressor from the system. The booster is always operating and the economizer is always active in the system. Since the high stage machines do not unload, they always operate at their peak efficiency.
Abstract of the Disclosure A refrigeration system characterized by a first stage booster compressor feeding multiple parallel connected second stage compressors in an otherwise conventional closed loop refrigeration system utilizing an economizer between the condenser and evaporator and returning economizer vapor to the inter-stage pressure point between the first stage and second stage compressors operates in a very flexible and highly efficient manner by driving the booster, first stage compressor at variable speed and the second stage compressors at constant speed, at maximum capacity, with those machines incapable of being unloaded. The control system utilizing a sensor for sensing evaporator pressure, evaporator temperature or suction pressure, varies the speed of the drive motor for the first stage booster compressor to initially slow down the booster and secondly connect or disconnect the second stage compressor from the system. The booster is always operating and the economizer is always active in the system. Since the high stage machines do not unload, they always operate at their peak efficiency.
Description
1242~3~36 RTY EE`FICIENT FT~TRTF~ C GE RE~IGERaTION SYSE:M
Field of the Invention mis invention relates to refrigeration and air oonditioning systems employing m~llti-stage oompressors, and re particularly, to a system utilizing an economizer for subcooling the condensed refrigerant prior to vaporization in the evaporator, and to an arrangement rendering high flexibility to multiple compressor operations while maximizing the efficiency of the refrigeration system bearing the first and second stage oompressors.
Background of the Invention Supermarkets today typically use three single stage oompressors in parallel which turn on and off on suction pressure. Such systems typically have no eoonomizer and thus the efficiency is low because the compression ratios are high and there is much cycling of the compressors and the suction pressure control band is still quite wide. These factors contribute to inefficiency and lack of reliability.
It is, therefore, a primary object of the present invention to provide an improved multi-ccmpressor refrigeration system in which the basic system still employs only three oompressors, one booster and two high stage oompressors, wherein the system employs an economizer which is oonstantly active within the system and which requires only two basic transducers for total system control.
Summary of thy Invention The present inYention is directed to a refrigeration circuit which oomprises at least one first stage oompressor, two seoond stage ~.~
` ,:.~
12~
compressors, a condenser, an economizer, an evaporator, and conduit means bearing a compressible refrigerant working fluid in connecting the first stage compressor, the second stage com-pressors as a group, the condenser, the economizer, and the evaporator, in series, in tha-t order, in a closed loop and with the second stage compressors in parallel with each o-ther.
The conduit means further comprises means for bleeding a portion of the condensed refrigerant from the closed loop downstream of the condenser and expanding it within the economizer for subcooling the liquid refrigerant within the closed loop being fed to the evaporator and for returning expanded refrigerant as relatively high pressure refrigerant vapor to an intermediate pressure point within the closed loop between the outlet of the first stage compressor and the inlet to the second stage compressors. jeans are provided for expanding the supercooled high pressure liquid refrigerant downstream of the economizer at the evaporator. Motors are provided for driving the compressors, and the system includes means for controlling opera-tion of the first and second stage compressors including means for selectively energizing the second stage compressor motors and for controlling refrigerant flow selectively to the second stage compressors. The improvement comprises driving the first stage booster compressor at a variable speed to effect a large variation in flow rate of the refrigerant passing therethrough, and wherein the second stage compressors comprise compressors fixedly operating at maximum load and thus opera-ting at their ~2~Z-~36 peak efficiency, such tnat the inter-stage pressure is maintained reasonable and wherein the control means comprises a first transducer for sensing any one of evaporating pressure, evaporating temperature or suction pressure, and second transducer means for sensing inter-stage pressure of the refrigerant circulating in the closed loop for controlling tne speed of the first stage booster compressor such that initially control is achieved by slowing down the booster and second when the inter-stage pressure reaches a predetermined minimurn, one of the second stage compressors is shut down; whereby, the inter-stage pressure automatically rises and increases the load on the remaining high stage compressor.
Any or all of the compressors may be reciprocating compressor helical screw rotary compressors, sliding vane rotary compressors, or scroll compressors. The motor for driving the first stage booster compressor may constitute an induction motor using a variable speed inverter drive, with the frequency varying between 20 to 100 Hertz.
According to a broad aspect of the invention there 0 is provided a refrigeration circuit comprising:
a first stage variable capacity compressor;
a plurality of second stage compressors;
conduit means bearing a compressible refrigerant inter-connecting said first stage compressor with said second stage compressors; and ~2~2~36 control means for modulating the capacity of said second stage compressors in response to the pressure in said conduit means between said first and second stage compressors.
Brief Description of the Drawings Figure 1 is a schematic diagram of a closed loop refrigeration circuit forming a preferred embodiment of the present invention.
Figure 2 is a plot of inter-stage pressure for -the system of Figure 1 against the system load/capacity illustrating the simplified control and flexibility of that refrigeration system.
description of the Preferred Embodiment Referring to Figure 1, there is snown a closed loop refrigeration system forming a preferred embodiment of the present invention as at 10. The closed loop system includes a first stage, -3a-12~2~86 booster compressor 12, a pair of second or high stage compressors as at 14, 16, an air cooled condenser 18, a receiver 20, an economizer 22, and an evaporator or evaporators 24 which are basic oomponents of the clofied loop refrigeration system 10. Conduit means function to connect the elements in series with the two high stage comprefisors 14, 16 in parallel as a group within the closed loop series circuit. As such, conduit 26 bearing a suitAhle refrigerant working fluid such as R-502 branches at point 27, into parallel conduits 28 and 30 to provide the fix output of the booster first stage compressor 12 at intermediate .. .
pressure to the suction side or inlets for the second stage oompressors 14, 16. The outputs of the sçcond stage compressors 14, 16 join via ro conduits 32 and 34 at junction 33~which high pressure compressed refrigerant vapor is fed to the inlet of the air oooled condenser 18 via conduit 36. The outlet of the air cooled condenser permits the condensed refrigerant to flow to receiver 20 via conduit 38. Afi indicated, thç refrigerant R in liquid form within receiver 20 flows via conduit or line 40 to the economizer 22. At point 41, a bypass or bleed line 42 permits a portion of the liquid refrigerant R to be bled from the primary d osed loop circuit and to expand via an expansion valve 44 within economizer 22 functioning to subcool the major portion of the liquid refrigerant which passes directly to the evaportor or evaporators 24 via line 46. This subcooled liquid refrigerant expands via exEansion valve 48 into and within the evaporator or evaporators 24 to perform a useful function within the refrigeration system. ffl e refrigerant vapor returning from the evaporator or evaporators 24 flows via line sn to the suction or low side of the booster first stage compressor 12, 1242~)~6 oompleting the closed loop circulation.
ble,l A; ; Meanwhile, the b~e3 refrigerant via line 42 which vaporizes within the economizer to perform the subcooling effect, pastes via line 52 to an intermediate pressure point as at 54 within the system oFening to conduit 26 connecting the outlet of the first stage compressor to the inlet of either or both second stage campressors 14, 16. It should be noted that while only two reoond or high stage oompressors 14, 16 are shown, there may be three or more high stage ccmpressors, all connected in parallel and suitably controlled. The system illustrated is purposely limited to two high stage compressors 14, 16.
The refrigeration system as illustrated allows highly efficient refrigeration to take place utilizing one or more evaporators 24 under all load conditions due to its oonstant use of an economizer cycle, i.e.
the booster firfit stage compressor 12 is always operating but the economizer 22 is always active. Purposely, two high stage oompressors 14, 16 are used in order that the inter-stage pressure variation does not beccme unmanageable. Also, the high stage machines, which may be reciprocating compressors without load capacity, do not unload and thus always operate at their peak efficiency. The booster first stage oompressor 12 may be a variable speed reciprocating oompressor, although it could be a variable speed screw oompre~sor, variable speed sliding vane rotary oompressor, etc. It is also pos~ikle to use a variable sFeed turbo oompressor, i.e. oentrifugal oompressor.
The goal of the system is the highest possible eficiency, and the system basically employs a booster compressor 12 operating at variable speed ccmbined with two or more high stage machines of fixed lZ~.2~86 capacity in order that the inter-stage pressure is maintained reasonable.
In the ;llustrated system, a tor Ml as at 56 is connected as indicated by dotted line 58 to the booster first stage oompressor 12 in order to drive the sane at variable speed and provide preferably a five to one flow range or better for the refrigerant R passing through the compressor. In turn, the second stage compressor 16 is directly driven by a second motor Mk as at 72, while motor M3 as at 74 directly drives the other second stage compressor 14.
The control system is inherently sLmple and stable. The system as illustrated employs a control panel as at 62 connected to a source S
via leads 76. Pbwer is thus supplied via the control panel 62 to motor 56 via electrical supply line 60. m e system utilizes two transducers.
The first transdu oe r 64 is a pressure transdu oe r as illustrated and senses the suction pressure to the first stage booster compressor 12 and is shown as being in line 50 supplying refrigerant from the evaporator or evaporators 24 to compressor 12 at the inlet or suction side of the booster oompressor 12. Alternatively, the transdu oe r 64 could be a transducer sensing the evaporating pressure or evaporating temperature for the evaporator or eYaporators 24. The signal for transdu oe r 64 is sent to the control panel 62 via line 66. m e second transducer 73 enses the inter-stage pressure, and in this case is connected within line 26 which feeds the discharge from the first stage compressor to the inlet side of the second stage oompressors 14, 16. Pressure transdu oe r oh 7 3 7 S
JnL :~2 supplies a signal via line to the control panel 62. In addition to line 60, which emanates from the oontrol panel 62 and whose function ~2g2~6 is to vary the speed of the drive motor 56 directly driving the booster oompressor 12, a number of other lines emanate from the control panel 62 and extend to various components of the system. In that respect, a control line 70 connects the control panel 62 to a solenoid operated valve 68 which is positioned within line 28 leading to the inlet of the second stage compressor 14 and functions to selectively cut out the second stage oompressor 14 from the system under oe rtain oonditions which will be explained hereinafter. Control line 76 ~manateR fram the control panel 62 and supplies current to the motor 72 which directly drives the second stage campressor 16. A supply line 78 extends from the control panel 62 to motor 74 functioning to directly drive the second stage oompressor 14.
Under operation, as the refrigerant reguirement falls for the evaporator or evaporators 24, the suction pressure at the inlet of the A booster oompressor 12 will drop and transducer 64 supplies a cantrol signal via line 66 to the control panel evidencing the drop in suction pressure. In turn, the oontrol panel 62 varies the current flowing to the drive motor 56 so as to slow down the booster compressor and thereby decrease the flow of refrigerant through the first stage compressor 12.
ffl e motor 56 may comprise an induction tor using a variable speed inverter drive in which case the control panel 62 will function to vary the frequency of the current flow supplied to the tor 56 via line 60.
For a fiYe to one flow range for the Wooster oompressor 12, the variance in frequency of the control signal to motor 56 may be from 20 to 100 Hertz.
When the inter-stage pressure reaches a predetermined minimum, ~Z4Z(1~136 one of the two second stage compressors will be shut down, and the inter-stage pressure will automatically rise and increase the load on the remaining high speed stage compressor or compressors. In the llustrated system, the second transducer 73 sensing inter-stage pressure will supply a signal indicative of the further ti~r~s~re p~ssv J 7 S
r'eduction in inter-stage~via line to the control panel 62. The control panel 62 will then shut down the compressor as at 14 by terminating energization of that drive motor 74 via line 78.
Simultaneously, if needed, the solenoid qperated control valve 68 will change state to shut off refrigerant flow through line 28 leading to the seoond stage compressor 14 via line 70.
The system operation is graphically illustrated in Figure 2 which is a plot inter-stage pressure against system load/capacity. m e two parallel solid plot lines P and P' are inter-stage pressure plots depending upon the operation of one or two high stage machines. Plot P
is for a single second stage compressor while plot P' covers higher system load/capacity operations from 40 to 100 peroent. Assuming, for instance, that the system is operating at conditions of low load with a single second stage compressor in operation, i.e. second stage compressor 16 and keeping in mind that the booster first stage oompressor is always operating and thus the economizer 22 is always active, when system operation is such that the inter-stage pressure reaches a high point along plot line P, i.e. for instance at a selected 60 psig point indicated at B on plot line P, the second high stage compressor 14 is cut in, the inter-stage pressure drops to a pressure of about 26 psig at point B' on the second plot line P' for two high stage _~
~2~2~6 oompressor operations. As may be appreciated, since the load iB rising, the inter-stage pressure at which high stage compressor 14 i6 restarted, Pus s 7 e f L~Jh;c,h set higher than the rebalanced inter-stage~w~ the fiecond oompressor shuts off, the shut off point on paot line P' being at A which is a pressure of about 20 psig as illustrated for the system.
It should be kept in mind that the plot shown is for an efficient and reliable supermarket refrigeration system involving one or re evaporators 24 and forms the basis for a generic control philosophy or logic diagram wherein the refrigerant may be R-502 and the system having -20 F evaporating temperature. Under the system shcwn, there is an avoidance of excess cycling of the high stage oompressors 14, 16 which will not seriously affect the system efficiency as the economizer is still always active. With the inter-stage pressure dropping along plot line P`to 20 psig and reaching point A, the system drops out the compressor 14 maintaining second stage compressor 16, and the inter-stage pressure immediately rises (for the same load) to approximately 46 psig. The single high stage oompressor 16 maintains system operation as the basic load continues to fall and the booster compressor 12 is slowed down further by suitable control from the control panel 62 to the booster drive motor 56 via line 60. As stated previously, if the load increases after system transfer to the single high stage compressor 16, the speed of rotor 56 increases appropriately proYiding an increase in the flow rate of the refrigerant through the first stage oompressor 12 until, of oourse, the inter-stage pressure reaches a level of 60 psig (point B, plot line P) wherein the second stage compressor 14 cuts in and oompresses refrigerant in parallel with _g_ ~2~2(~G
the refrigerant passing through the other second stage compressor 16.
Under the illustrated system, with falling system load, suction pressure transducer 64 causes booster compressor 12 speed to fall. When lnter-stage pressure reaches point A (plot line P'), one second stage compressor turns off and the inter-stage pressure rebalances (point A', plot line P). Rising load causes the booster compressor 12 to speed up and the second or next high stage compressor turns on at B (plot line P).
As may be appreciated, two basic transducers are the only input required for adequate control. One is required for measuring the suction pressure or its equivalent and one is required for measuring the inter-stage pressure of the closed loop refrigerant working fluid. The generic control logic is quite simple and straightforward, and a solid state control panel may be readily implemented to effect system control under the parameters disclosed herein. The refrigeration system is believed to be ideal for both commercial refrigeration as well as typical heat pumps for heating and cooling commercial and other buildings. The illustrated systemutilizesonly three compressors, one hooster and two high stage compressors. Tne system includes adequate redundancy in that the high stage compressors alone can handle about 50 percent of the maximum system load without the booster, and the booster and one high stage compressors can also handleabout 50 percent of the maximum system load as appreciated ~'J' ' .
1242~3~36 from the plots of Figure 2. The booster horsepower is so low that it may be reasonable to equip it with an inverter or a brushless DC drive to provide the variable speed necessary for the system.
While the invention has been particularly shown and described -lOa-h--I., lZ~Z086 with reference to a preferred cmboi1zent thereof, it will be understood my those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention.
Field of the Invention mis invention relates to refrigeration and air oonditioning systems employing m~llti-stage oompressors, and re particularly, to a system utilizing an economizer for subcooling the condensed refrigerant prior to vaporization in the evaporator, and to an arrangement rendering high flexibility to multiple compressor operations while maximizing the efficiency of the refrigeration system bearing the first and second stage oompressors.
Background of the Invention Supermarkets today typically use three single stage oompressors in parallel which turn on and off on suction pressure. Such systems typically have no eoonomizer and thus the efficiency is low because the compression ratios are high and there is much cycling of the compressors and the suction pressure control band is still quite wide. These factors contribute to inefficiency and lack of reliability.
It is, therefore, a primary object of the present invention to provide an improved multi-ccmpressor refrigeration system in which the basic system still employs only three oompressors, one booster and two high stage oompressors, wherein the system employs an economizer which is oonstantly active within the system and which requires only two basic transducers for total system control.
Summary of thy Invention The present inYention is directed to a refrigeration circuit which oomprises at least one first stage oompressor, two seoond stage ~.~
` ,:.~
12~
compressors, a condenser, an economizer, an evaporator, and conduit means bearing a compressible refrigerant working fluid in connecting the first stage compressor, the second stage com-pressors as a group, the condenser, the economizer, and the evaporator, in series, in tha-t order, in a closed loop and with the second stage compressors in parallel with each o-ther.
The conduit means further comprises means for bleeding a portion of the condensed refrigerant from the closed loop downstream of the condenser and expanding it within the economizer for subcooling the liquid refrigerant within the closed loop being fed to the evaporator and for returning expanded refrigerant as relatively high pressure refrigerant vapor to an intermediate pressure point within the closed loop between the outlet of the first stage compressor and the inlet to the second stage compressors. jeans are provided for expanding the supercooled high pressure liquid refrigerant downstream of the economizer at the evaporator. Motors are provided for driving the compressors, and the system includes means for controlling opera-tion of the first and second stage compressors including means for selectively energizing the second stage compressor motors and for controlling refrigerant flow selectively to the second stage compressors. The improvement comprises driving the first stage booster compressor at a variable speed to effect a large variation in flow rate of the refrigerant passing therethrough, and wherein the second stage compressors comprise compressors fixedly operating at maximum load and thus opera-ting at their ~2~Z-~36 peak efficiency, such tnat the inter-stage pressure is maintained reasonable and wherein the control means comprises a first transducer for sensing any one of evaporating pressure, evaporating temperature or suction pressure, and second transducer means for sensing inter-stage pressure of the refrigerant circulating in the closed loop for controlling tne speed of the first stage booster compressor such that initially control is achieved by slowing down the booster and second when the inter-stage pressure reaches a predetermined minimurn, one of the second stage compressors is shut down; whereby, the inter-stage pressure automatically rises and increases the load on the remaining high stage compressor.
Any or all of the compressors may be reciprocating compressor helical screw rotary compressors, sliding vane rotary compressors, or scroll compressors. The motor for driving the first stage booster compressor may constitute an induction motor using a variable speed inverter drive, with the frequency varying between 20 to 100 Hertz.
According to a broad aspect of the invention there 0 is provided a refrigeration circuit comprising:
a first stage variable capacity compressor;
a plurality of second stage compressors;
conduit means bearing a compressible refrigerant inter-connecting said first stage compressor with said second stage compressors; and ~2~2~36 control means for modulating the capacity of said second stage compressors in response to the pressure in said conduit means between said first and second stage compressors.
Brief Description of the Drawings Figure 1 is a schematic diagram of a closed loop refrigeration circuit forming a preferred embodiment of the present invention.
Figure 2 is a plot of inter-stage pressure for -the system of Figure 1 against the system load/capacity illustrating the simplified control and flexibility of that refrigeration system.
description of the Preferred Embodiment Referring to Figure 1, there is snown a closed loop refrigeration system forming a preferred embodiment of the present invention as at 10. The closed loop system includes a first stage, -3a-12~2~86 booster compressor 12, a pair of second or high stage compressors as at 14, 16, an air cooled condenser 18, a receiver 20, an economizer 22, and an evaporator or evaporators 24 which are basic oomponents of the clofied loop refrigeration system 10. Conduit means function to connect the elements in series with the two high stage comprefisors 14, 16 in parallel as a group within the closed loop series circuit. As such, conduit 26 bearing a suitAhle refrigerant working fluid such as R-502 branches at point 27, into parallel conduits 28 and 30 to provide the fix output of the booster first stage compressor 12 at intermediate .. .
pressure to the suction side or inlets for the second stage oompressors 14, 16. The outputs of the sçcond stage compressors 14, 16 join via ro conduits 32 and 34 at junction 33~which high pressure compressed refrigerant vapor is fed to the inlet of the air oooled condenser 18 via conduit 36. The outlet of the air cooled condenser permits the condensed refrigerant to flow to receiver 20 via conduit 38. Afi indicated, thç refrigerant R in liquid form within receiver 20 flows via conduit or line 40 to the economizer 22. At point 41, a bypass or bleed line 42 permits a portion of the liquid refrigerant R to be bled from the primary d osed loop circuit and to expand via an expansion valve 44 within economizer 22 functioning to subcool the major portion of the liquid refrigerant which passes directly to the evaportor or evaporators 24 via line 46. This subcooled liquid refrigerant expands via exEansion valve 48 into and within the evaporator or evaporators 24 to perform a useful function within the refrigeration system. ffl e refrigerant vapor returning from the evaporator or evaporators 24 flows via line sn to the suction or low side of the booster first stage compressor 12, 1242~)~6 oompleting the closed loop circulation.
ble,l A; ; Meanwhile, the b~e3 refrigerant via line 42 which vaporizes within the economizer to perform the subcooling effect, pastes via line 52 to an intermediate pressure point as at 54 within the system oFening to conduit 26 connecting the outlet of the first stage compressor to the inlet of either or both second stage campressors 14, 16. It should be noted that while only two reoond or high stage oompressors 14, 16 are shown, there may be three or more high stage ccmpressors, all connected in parallel and suitably controlled. The system illustrated is purposely limited to two high stage compressors 14, 16.
The refrigeration system as illustrated allows highly efficient refrigeration to take place utilizing one or more evaporators 24 under all load conditions due to its oonstant use of an economizer cycle, i.e.
the booster firfit stage compressor 12 is always operating but the economizer 22 is always active. Purposely, two high stage oompressors 14, 16 are used in order that the inter-stage pressure variation does not beccme unmanageable. Also, the high stage machines, which may be reciprocating compressors without load capacity, do not unload and thus always operate at their peak efficiency. The booster first stage oompressor 12 may be a variable speed reciprocating oompressor, although it could be a variable speed screw oompre~sor, variable speed sliding vane rotary oompressor, etc. It is also pos~ikle to use a variable sFeed turbo oompressor, i.e. oentrifugal oompressor.
The goal of the system is the highest possible eficiency, and the system basically employs a booster compressor 12 operating at variable speed ccmbined with two or more high stage machines of fixed lZ~.2~86 capacity in order that the inter-stage pressure is maintained reasonable.
In the ;llustrated system, a tor Ml as at 56 is connected as indicated by dotted line 58 to the booster first stage oompressor 12 in order to drive the sane at variable speed and provide preferably a five to one flow range or better for the refrigerant R passing through the compressor. In turn, the second stage compressor 16 is directly driven by a second motor Mk as at 72, while motor M3 as at 74 directly drives the other second stage compressor 14.
The control system is inherently sLmple and stable. The system as illustrated employs a control panel as at 62 connected to a source S
via leads 76. Pbwer is thus supplied via the control panel 62 to motor 56 via electrical supply line 60. m e system utilizes two transducers.
The first transdu oe r 64 is a pressure transdu oe r as illustrated and senses the suction pressure to the first stage booster compressor 12 and is shown as being in line 50 supplying refrigerant from the evaporator or evaporators 24 to compressor 12 at the inlet or suction side of the booster oompressor 12. Alternatively, the transdu oe r 64 could be a transducer sensing the evaporating pressure or evaporating temperature for the evaporator or eYaporators 24. The signal for transdu oe r 64 is sent to the control panel 62 via line 66. m e second transducer 73 enses the inter-stage pressure, and in this case is connected within line 26 which feeds the discharge from the first stage compressor to the inlet side of the second stage oompressors 14, 16. Pressure transdu oe r oh 7 3 7 S
JnL :~2 supplies a signal via line to the control panel 62. In addition to line 60, which emanates from the oontrol panel 62 and whose function ~2g2~6 is to vary the speed of the drive motor 56 directly driving the booster oompressor 12, a number of other lines emanate from the control panel 62 and extend to various components of the system. In that respect, a control line 70 connects the control panel 62 to a solenoid operated valve 68 which is positioned within line 28 leading to the inlet of the second stage compressor 14 and functions to selectively cut out the second stage oompressor 14 from the system under oe rtain oonditions which will be explained hereinafter. Control line 76 ~manateR fram the control panel 62 and supplies current to the motor 72 which directly drives the second stage campressor 16. A supply line 78 extends from the control panel 62 to motor 74 functioning to directly drive the second stage oompressor 14.
Under operation, as the refrigerant reguirement falls for the evaporator or evaporators 24, the suction pressure at the inlet of the A booster oompressor 12 will drop and transducer 64 supplies a cantrol signal via line 66 to the control panel evidencing the drop in suction pressure. In turn, the oontrol panel 62 varies the current flowing to the drive motor 56 so as to slow down the booster compressor and thereby decrease the flow of refrigerant through the first stage compressor 12.
ffl e motor 56 may comprise an induction tor using a variable speed inverter drive in which case the control panel 62 will function to vary the frequency of the current flow supplied to the tor 56 via line 60.
For a fiYe to one flow range for the Wooster oompressor 12, the variance in frequency of the control signal to motor 56 may be from 20 to 100 Hertz.
When the inter-stage pressure reaches a predetermined minimum, ~Z4Z(1~136 one of the two second stage compressors will be shut down, and the inter-stage pressure will automatically rise and increase the load on the remaining high speed stage compressor or compressors. In the llustrated system, the second transducer 73 sensing inter-stage pressure will supply a signal indicative of the further ti~r~s~re p~ssv J 7 S
r'eduction in inter-stage~via line to the control panel 62. The control panel 62 will then shut down the compressor as at 14 by terminating energization of that drive motor 74 via line 78.
Simultaneously, if needed, the solenoid qperated control valve 68 will change state to shut off refrigerant flow through line 28 leading to the seoond stage compressor 14 via line 70.
The system operation is graphically illustrated in Figure 2 which is a plot inter-stage pressure against system load/capacity. m e two parallel solid plot lines P and P' are inter-stage pressure plots depending upon the operation of one or two high stage machines. Plot P
is for a single second stage compressor while plot P' covers higher system load/capacity operations from 40 to 100 peroent. Assuming, for instance, that the system is operating at conditions of low load with a single second stage compressor in operation, i.e. second stage compressor 16 and keeping in mind that the booster first stage oompressor is always operating and thus the economizer 22 is always active, when system operation is such that the inter-stage pressure reaches a high point along plot line P, i.e. for instance at a selected 60 psig point indicated at B on plot line P, the second high stage compressor 14 is cut in, the inter-stage pressure drops to a pressure of about 26 psig at point B' on the second plot line P' for two high stage _~
~2~2~6 oompressor operations. As may be appreciated, since the load iB rising, the inter-stage pressure at which high stage compressor 14 i6 restarted, Pus s 7 e f L~Jh;c,h set higher than the rebalanced inter-stage~w~ the fiecond oompressor shuts off, the shut off point on paot line P' being at A which is a pressure of about 20 psig as illustrated for the system.
It should be kept in mind that the plot shown is for an efficient and reliable supermarket refrigeration system involving one or re evaporators 24 and forms the basis for a generic control philosophy or logic diagram wherein the refrigerant may be R-502 and the system having -20 F evaporating temperature. Under the system shcwn, there is an avoidance of excess cycling of the high stage oompressors 14, 16 which will not seriously affect the system efficiency as the economizer is still always active. With the inter-stage pressure dropping along plot line P`to 20 psig and reaching point A, the system drops out the compressor 14 maintaining second stage compressor 16, and the inter-stage pressure immediately rises (for the same load) to approximately 46 psig. The single high stage oompressor 16 maintains system operation as the basic load continues to fall and the booster compressor 12 is slowed down further by suitable control from the control panel 62 to the booster drive motor 56 via line 60. As stated previously, if the load increases after system transfer to the single high stage compressor 16, the speed of rotor 56 increases appropriately proYiding an increase in the flow rate of the refrigerant through the first stage oompressor 12 until, of oourse, the inter-stage pressure reaches a level of 60 psig (point B, plot line P) wherein the second stage compressor 14 cuts in and oompresses refrigerant in parallel with _g_ ~2~2(~G
the refrigerant passing through the other second stage compressor 16.
Under the illustrated system, with falling system load, suction pressure transducer 64 causes booster compressor 12 speed to fall. When lnter-stage pressure reaches point A (plot line P'), one second stage compressor turns off and the inter-stage pressure rebalances (point A', plot line P). Rising load causes the booster compressor 12 to speed up and the second or next high stage compressor turns on at B (plot line P).
As may be appreciated, two basic transducers are the only input required for adequate control. One is required for measuring the suction pressure or its equivalent and one is required for measuring the inter-stage pressure of the closed loop refrigerant working fluid. The generic control logic is quite simple and straightforward, and a solid state control panel may be readily implemented to effect system control under the parameters disclosed herein. The refrigeration system is believed to be ideal for both commercial refrigeration as well as typical heat pumps for heating and cooling commercial and other buildings. The illustrated systemutilizesonly three compressors, one hooster and two high stage compressors. Tne system includes adequate redundancy in that the high stage compressors alone can handle about 50 percent of the maximum system load without the booster, and the booster and one high stage compressors can also handleabout 50 percent of the maximum system load as appreciated ~'J' ' .
1242~3~36 from the plots of Figure 2. The booster horsepower is so low that it may be reasonable to equip it with an inverter or a brushless DC drive to provide the variable speed necessary for the system.
While the invention has been particularly shown and described -lOa-h--I., lZ~Z086 with reference to a preferred cmboi1zent thereof, it will be understood my those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention.
Claims (22)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A refrigeration circuit comprising:
variable capacity first stage compressor means;
second stage compressor means;
a condenser;
an evaporator;
conduit means bearing a compressible refrigerant interconnecting said first stage compressor means, said second stage compressor means, said condenser, and said evaporator, in series in a closed loop, in that order;
motors for driving said compressor means;
an economizer operatively disposed between said condenser and evaporator for expanding a portion of the condensed refrigerant from said closed loop downstream of said condenser for subcooling refrigerant flowing to said evaporator;
means for feeding said expanded portion of refrigerant to an inter-stage point between the outlet of said first stage compressor means and the inlet of said second stage compressor means; and control means for controlling the operation of said second stage compressor means in response to a condition at said inter-stage point.
variable capacity first stage compressor means;
second stage compressor means;
a condenser;
an evaporator;
conduit means bearing a compressible refrigerant interconnecting said first stage compressor means, said second stage compressor means, said condenser, and said evaporator, in series in a closed loop, in that order;
motors for driving said compressor means;
an economizer operatively disposed between said condenser and evaporator for expanding a portion of the condensed refrigerant from said closed loop downstream of said condenser for subcooling refrigerant flowing to said evaporator;
means for feeding said expanded portion of refrigerant to an inter-stage point between the outlet of said first stage compressor means and the inlet of said second stage compressor means; and control means for controlling the operation of said second stage compressor means in response to a condition at said inter-stage point.
2. A refrigeration circuit as claimed in claim 1, wherein said control means comprises a first sensor for sensing a condition on the suction side of the first stage and a second sensor for sensing a condition on the suction side of the second stage.
3. A refrigeration circuit as set forth in claim 2, wherein said second sensor senses inter-stage refrigerant pressure.
4. A refrigeration circuit as claimed in claim 2, wherein said control means is operable to initially vary the capacity of said first stage compressor means and secondly for varying the capacity of said second stage compressor means so that inter-stage pressure is maintained within a desired range.
5. A refrigeration circuit as claimed in claim 4, wherein the capacity of said first stage compressor means is controlled in response to a condition on the suction side of the first stage and the capacity of said second stage compressor means is controlled in response to a condition on the suction side of said second stage.
6. A refrigeration circuit as claimed in claim 1, wherein said second stage compressor means comprises at least two fixed capacity compressors.
7. The refrigeration system as claimed in claim 6, wherein said control means includes means for selectively closing off inter-stage refrigeratnt flow from said first stage compressor means to at least one of said second stage fixed capacity compre-ssors.
8. The refrigeration system as claimed in claim 6, where-in said control means comprises means for terminating energization of the drive motor for at least one of said second stage fixed capacity compressors.
9. The refrigeration system as claimed in claim 6, wherein said fixed capacity compressors are connected in parallel with each other.
10. The refrigeration system as set forth in claim 1, 2 or 5 wherein said first stage compressor motor is a variable speed motor.
11. A refrigeration circuit comprising:
a variable capacity first stage compressor;
at least two fixed capacity second stage compressors;
conduit means bearing a compressible refrigerant connecting said first stage compressor to said second stage compressors, said second stage compressors being connected in parallel with each other, motors for driving said compressors; and control means including sensing means for sensing inter-stage refrigerant pressure within said conduit means and means responsive thereto for shutting down at least one of said second stage compressors, when the inter-stage pressure reaches a predetermined minimum.
a variable capacity first stage compressor;
at least two fixed capacity second stage compressors;
conduit means bearing a compressible refrigerant connecting said first stage compressor to said second stage compressors, said second stage compressors being connected in parallel with each other, motors for driving said compressors; and control means including sensing means for sensing inter-stage refrigerant pressure within said conduit means and means responsive thereto for shutting down at least one of said second stage compressors, when the inter-stage pressure reaches a predetermined minimum.
12. A refrigeration circuit comprising:
a variable capacity first stage compressor;
variable capacity second stage compressor means;
a condenser;
an evaporator;
conduit means bearing a compressible refrigerant inter-connecting said first stage compressor, said second stage compressor means, said condenser and said evaporator, in series in a closed loop, in that order;
motors for driving said first stage compressor and second stage compressor means; and control means utilizing only two sensors for controlling capacity modulation, the first sensor sensing a condition on the suction side of the first stage, and the second sensor sensing a condition on the suction side of said second stage compressor, and means responsive to said sensors for initially varying the capacity of said first stage compressor and secondly for varying the capacity of said second stage compressor means so that the inter-stage pressure is maintained within a desired range.
a variable capacity first stage compressor;
variable capacity second stage compressor means;
a condenser;
an evaporator;
conduit means bearing a compressible refrigerant inter-connecting said first stage compressor, said second stage compressor means, said condenser and said evaporator, in series in a closed loop, in that order;
motors for driving said first stage compressor and second stage compressor means; and control means utilizing only two sensors for controlling capacity modulation, the first sensor sensing a condition on the suction side of the first stage, and the second sensor sensing a condition on the suction side of said second stage compressor, and means responsive to said sensors for initially varying the capacity of said first stage compressor and secondly for varying the capacity of said second stage compressor means so that the inter-stage pressure is maintained within a desired range.
13. A refrigeration circuit as set forth in claim 12 further comprising an economizer, said conduit means connecting said economizer between said condensor and said evaporator, and further comprising means for bleeding a portion of the condensed refrigerant from said closed loop downstream of said condenser and expanding it within said economizer for subcooling liquid refrigerant fed by said closed loop to said evaporator and for returning expanded refrigerant at relatively high pressure from said economizer to an inter-stage pressure point between the outlet of the first stage compressor and the inlet of said second stage compressor means.
14. A refrigeration circuit as claimed in claim 12, wherein said second stage compressor means comprises at least two second stage fixed capacity compressors.
15. A refrigeration circuit as set forth in claim 14 wherein said first stage compressor motor is a variable speed motor.
16. A refrigeration circuit comprising:
a variable capacity first stage compressor;
a second stage compressor;
a condenser;
an evaporator;
conduit means bearing a compressible refrigerant inter-connecting said first stage compressor, said second stage compressor, said condenser, and said evaporator, in series in a closed loop, in that order;
motors for driving said compressors; and control means comprising first sensing means for sensing a condition on the suction side of the first stage, and second sensing means for sensing inter-stage refrigerant pressure, and means responsive thereto for initially varying the capacity of said first stage compressor and secondly for shutting down said second stage compressor when the inter-stage pressure reaches a predetermined minimum.
a variable capacity first stage compressor;
a second stage compressor;
a condenser;
an evaporator;
conduit means bearing a compressible refrigerant inter-connecting said first stage compressor, said second stage compressor, said condenser, and said evaporator, in series in a closed loop, in that order;
motors for driving said compressors; and control means comprising first sensing means for sensing a condition on the suction side of the first stage, and second sensing means for sensing inter-stage refrigerant pressure, and means responsive thereto for initially varying the capacity of said first stage compressor and secondly for shutting down said second stage compressor when the inter-stage pressure reaches a predetermined minimum.
17. A refrigeration circuit comprising:
first stage compressor means;
at least two fixed capacity second stage compressors;
conduit means bearing a compressible refrigerant connecting said first stage compressor to said second stage compressors, said second stage compressors being connected in parallel with each other;
motors for driving said compressors; and control means including sensing means for sensing inter-stage refrigerant pressure within said conduit means and means responsive thereto for shutting down at least one of said second stage compressors, when the inter-stage pressure reaches a pre-determined minimum.
first stage compressor means;
at least two fixed capacity second stage compressors;
conduit means bearing a compressible refrigerant connecting said first stage compressor to said second stage compressors, said second stage compressors being connected in parallel with each other;
motors for driving said compressors; and control means including sensing means for sensing inter-stage refrigerant pressure within said conduit means and means responsive thereto for shutting down at least one of said second stage compressors, when the inter-stage pressure reaches a pre-determined minimum.
18. A refrigeration circuit comprising:
first stage compressor means;
variable capacity second stage compressor means;
a condenser;
an evaporator;
conduit means bearing a compressible refrigerant inter-connecting said first stage compressor means, said second stage compressor means, said condenser and said evaporator, in series in a closed loop, in that order;
motor means for driving said first stage compressor means and said second stage compressor means; and control means utilizing only two sensors for controlling capacity modulation, the first sensor sensing a condition on the suction side of the first stage, and the second sensor sensing inter-stage refrigerant pressure and means responsive to said sensors for varying the capacity of said second stage compressor means so that the inter-stage pressure variation is maintained within a desired range.
first stage compressor means;
variable capacity second stage compressor means;
a condenser;
an evaporator;
conduit means bearing a compressible refrigerant inter-connecting said first stage compressor means, said second stage compressor means, said condenser and said evaporator, in series in a closed loop, in that order;
motor means for driving said first stage compressor means and said second stage compressor means; and control means utilizing only two sensors for controlling capacity modulation, the first sensor sensing a condition on the suction side of the first stage, and the second sensor sensing inter-stage refrigerant pressure and means responsive to said sensors for varying the capacity of said second stage compressor means so that the inter-stage pressure variation is maintained within a desired range.
19. A refrigeration circuit comprising:
a variable capacity first stage compressor;
at least two fixed capacity second stage compressors;
conduit means bearing a compressible refrigerant connecting said first stage compressor to said second stage compressors, said second stage compressors being connected in parallel with each other;
motors for driving said compressors; and control means for controlling said first state compressor and said second stage compressors, said control means being operable to vary the capacity of said first stage compressor while said second stage compressors are operating, to shut down one of said second stage compressors when the capacity of said first stage compressor reaches a predetermined minimum and thereafter to increase the capacity of said first stage compre-ssor while continuing to operate the remaining second stage compressors.
a variable capacity first stage compressor;
at least two fixed capacity second stage compressors;
conduit means bearing a compressible refrigerant connecting said first stage compressor to said second stage compressors, said second stage compressors being connected in parallel with each other;
motors for driving said compressors; and control means for controlling said first state compressor and said second stage compressors, said control means being operable to vary the capacity of said first stage compressor while said second stage compressors are operating, to shut down one of said second stage compressors when the capacity of said first stage compressor reaches a predetermined minimum and thereafter to increase the capacity of said first stage compre-ssor while continuing to operate the remaining second stage compressors.
20. A refrigeration circuit as claimed in claim 19, wherein said control meansincludes sensing means for sensing inter-stage refrigerant pressure within said conduit means and means responsive thereto for shutting down at least one of said second stage compressors when the inter-stage pressure reaches a predetermined minimum.
21. A refrigeration circuit comprising:
a first stage variable capacity compressor;
a plurality of second stage compressors;
conduit means bearing a compressible refrigerant inter-connecting said first stage compressor with said second stage compressors; and control means for modulating the capacity of said second stage compressors in response to the pressure in said conduit means between said first and second stage compressors.
a first stage variable capacity compressor;
a plurality of second stage compressors;
conduit means bearing a compressible refrigerant inter-connecting said first stage compressor with said second stage compressors; and control means for modulating the capacity of said second stage compressors in response to the pressure in said conduit means between said first and second stage compressors.
22. A refrigeration circuit comprising:
variable capacity first stage compressor means;
second stage compressor means;
a condenser;
an evaporator;
conduit means bearing a compressible refrigerant inter-connecting said first stage compressor means, said second stage compressor means, said condenser, and said evaporator, in series in a closed loop, in that order;
motors for diring said compressor means;
an economizer operatively disposed between said condenser and evaporator for expanding a portion of the condensed refrigerant from said closed loop downstream of said condenser for subcooling refrigerant flowing to said evaporator;
means for feeding said expanded portion of refrigerant to an inter-stage point between the outlet of said first stage compressor means and the inlet of said second stage compressor means; and control means for controlling the operation of said second stage compressor means in response to a condition at said inter-stage point.
variable capacity first stage compressor means;
second stage compressor means;
a condenser;
an evaporator;
conduit means bearing a compressible refrigerant inter-connecting said first stage compressor means, said second stage compressor means, said condenser, and said evaporator, in series in a closed loop, in that order;
motors for diring said compressor means;
an economizer operatively disposed between said condenser and evaporator for expanding a portion of the condensed refrigerant from said closed loop downstream of said condenser for subcooling refrigerant flowing to said evaporator;
means for feeding said expanded portion of refrigerant to an inter-stage point between the outlet of said first stage compressor means and the inlet of said second stage compressor means; and control means for controlling the operation of said second stage compressor means in response to a condition at said inter-stage point.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US56988684A | 1984-01-11 | 1984-01-11 | |
| US569,886 | 1984-01-11 |
Publications (1)
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|---|---|
| CA1242086A true CA1242086A (en) | 1988-09-20 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000471641A Expired CA1242086A (en) | 1984-01-11 | 1985-01-08 | Highly efficient flexible two-stage refrigeration system |
Country Status (13)
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| JP (1) | JPS60159561A (en) |
| AU (1) | AU587173B2 (en) |
| BR (1) | BR8500106A (en) |
| CA (1) | CA1242086A (en) |
| DE (1) | DE3500800A1 (en) |
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| ES (1) | ES8602237A1 (en) |
| FR (1) | FR2557962B1 (en) |
| GB (1) | GB2152649B (en) |
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| MX (1) | MX161408A (en) |
| NZ (1) | NZ210800A (en) |
| ZA (1) | ZA8562B (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4787211A (en) * | 1984-07-30 | 1988-11-29 | Copeland Corporation | Refrigeration system |
| US4748820A (en) * | 1984-01-11 | 1988-06-07 | Copeland Corporation | Refrigeration system |
| US4938029A (en) * | 1989-07-03 | 1990-07-03 | Carrier Corporation | Unloading system for two-stage compressors |
| ES2092424B1 (en) * | 1992-09-16 | 1997-07-01 | Ornaque Carlos Gutierrez | MIXED BLOCK REFRIGERATION SECURITY SYSTEM. |
| DE19529763A1 (en) * | 1995-08-12 | 1997-02-13 | Ruediger Piepenhagen | Refrigeration plant - has pressure sensor for evaporation pressure and control circuitry for induction motor-driven compressor to keep this pressure constant |
| JP2985882B1 (en) * | 1998-08-21 | 1999-12-06 | ダイキン工業株式会社 | Double tube heat exchanger |
| JP2003207248A (en) * | 2002-01-15 | 2003-07-25 | Toshiba Corp | Refrigerator |
| JP3953871B2 (en) * | 2002-04-15 | 2007-08-08 | サンデン株式会社 | Refrigeration air conditioner |
| JP3951799B2 (en) * | 2002-05-14 | 2007-08-01 | 株式会社デンソー | Control device for variable capacity compressor |
| FR2864609B1 (en) * | 2003-12-29 | 2006-12-22 | Patrice Saillard | THERMAL INSTALLATION WITH MULTIPLE CONFIGURATION, AND EXCHANGER SUITABLE FOR THIS INSTALLATION. |
| JP2008025905A (en) * | 2006-07-20 | 2008-02-07 | Daikin Ind Ltd | Refrigerator |
| JP4245023B2 (en) * | 2006-09-11 | 2009-03-25 | ダイキン工業株式会社 | Refrigeration equipment |
| JP5400796B2 (en) * | 2007-12-28 | 2014-01-29 | ジョンソン コントロールズ テクノロジー カンパニー | Vapor compression system and method of operating the same |
| JP5040907B2 (en) * | 2008-09-30 | 2012-10-03 | ダイキン工業株式会社 | Refrigeration equipment |
| JP5402164B2 (en) * | 2009-03-31 | 2014-01-29 | 株式会社富士通ゼネラル | Refrigeration cycle equipment |
| KR20110004152A (en) * | 2009-07-07 | 2011-01-13 | 엘지전자 주식회사 | Air conditioner |
| JP6643632B2 (en) * | 2016-03-10 | 2020-02-12 | パナソニックＩｐマネジメント株式会社 | Air conditioner |
Family Cites Families (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2386198A (en) * | 1944-02-08 | 1945-10-09 | Gen Electric | Multistage refrigerating system |
| US2677944A (en) * | 1950-12-01 | 1954-05-11 | Alonzo W Ruff | Plural stage refrigeration apparatus |
| FR1056197A (en) * | 1952-01-09 | 1954-02-24 | Anciens Ets Brissonneau & Lotz | Advanced refrigeration system with two compression stages |
| US3238738A (en) * | 1964-02-12 | 1966-03-08 | Robert C Webber | Two-stage refrigeration system with by-pass means |
| US3759052A (en) * | 1972-02-28 | 1973-09-18 | Maekawa Seisakusho Kk | Method of controlling high stage and low stage compressors |
| JPS5223402B2 (en) * | 1973-10-12 | 1977-06-24 | ||
| US4033738A (en) * | 1976-03-12 | 1977-07-05 | Westinghouse Electric Corporation | Heat pump system with multi-stage centrifugal compressors |
| US4060997A (en) * | 1976-03-31 | 1977-12-06 | Application Engineering Corporation | Water chiller control |
| US4245476A (en) * | 1979-01-02 | 1981-01-20 | Dunham-Bush, Inc. | Solar augmented heat pump system with automatic staging reciprocating compressor |
| US4325223A (en) * | 1981-03-16 | 1982-04-20 | Cantley Robert J | Energy management system for refrigeration systems |
| US4332144A (en) * | 1981-03-26 | 1982-06-01 | Shaw David N | Bottoming cycle refrigerant scavenging for positive displacement compressor, refrigeration and heat pump systems |
| FR2513747A1 (en) * | 1981-09-25 | 1983-04-01 | Satam Brandt Froid | MULTIMOTOCOMPRESSOR REFRIGERATION SYSTEM |
| NL188479C (en) * | 1982-01-28 | 1992-07-01 | Marinus Wilhelmus Matheus Avon | COOLING DEVICE. |
-
1985
- 1985-01-03 ZA ZA8562A patent/ZA8562B/en unknown
- 1985-01-07 GB GB08500339A patent/GB2152649B/en not_active Expired
- 1985-01-08 AU AU37399/85A patent/AU587173B2/en not_active Ceased
- 1985-01-08 CA CA000471641A patent/CA1242086A/en not_active Expired
- 1985-01-09 DK DK9885A patent/DK9885A/en not_active Application Discontinuation
- 1985-01-10 JP JP60002623A patent/JPS60159561A/en active Granted
- 1985-01-10 IT IT8519070A patent/IT1212109B/en active
- 1985-01-10 MX MX204009A patent/MX161408A/en unknown
- 1985-01-10 BR BR8500106A patent/BR8500106A/en not_active IP Right Cessation
- 1985-01-10 NZ NZ210800A patent/NZ210800A/en unknown
- 1985-01-10 ES ES539449A patent/ES8602237A1/en not_active Expired
- 1985-01-11 DE DE19853500800 patent/DE3500800A1/en not_active Ceased
- 1985-01-11 FR FR858500380A patent/FR2557962B1/en not_active Expired - Lifetime
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| DE3500800A1 (en) | 1985-07-18 |
| MX161408A (en) | 1990-09-21 |
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| ZA8562B (en) | 1985-09-25 |
| BR8500106A (en) | 1985-08-20 |
| ES539449A0 (en) | 1985-11-01 |
| GB2152649B (en) | 1987-02-18 |
| FR2557962A1 (en) | 1985-07-12 |
| IT8519070A0 (en) | 1985-01-10 |
| ES8602237A1 (en) | 1985-11-01 |
| DK9885A (en) | 1985-07-12 |
| NZ210800A (en) | 1987-07-31 |
| FR2557962B1 (en) | 1990-08-31 |
| AU3739985A (en) | 1985-07-18 |
| JPS60159561A (en) | 1985-08-21 |
| IT1212109B (en) | 1989-11-08 |
| GB2152649A (en) | 1985-08-07 |
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