FR2464443A1 - METHOD FOR OPERATING A REFRIGERATION FACILITY - Google Patents

Abstract

PROCESS FOR OPERATING A REFRIGERATION INSTALLATION OF THE TYPE CONTAINING A COMPRESSOR WITH SEVERAL CYLINDERS OR SEVERAL COMPRESSORS. IT CONSISTS OF OPERATING THE INSTALLATION UNDER NORMAL OPERATING CONDITIONS, DETECTING OPERATING CONDITIONS SUCH AS THE DISCHARGE PRESSURE (MANOMETRIC CAPSULE 25) OR THE AMBIENT TEMPERATURE AND PARTIALLY DISCHARGING THE COMPRESSOR 10 BY CONNECTING THE OUTPUT FROM ITS CYLINDERS 12 TO ITS INPUT, WHEN THE CONDITION DETECTED INDICATES THAT THE DISCHARGE PRESSURE, OR THE AMBIENT TEMPERATURE, EXCEEDS A PREDETERMINED LIMIT AND TO CONTINUE TO OPERATE THE REFRIGERATION SYSTEM AT REDUCED CAPACITY UNTIL THE CONDITIONS REBUILT. APPLICATION TO COOLING SYSTEMS.

Description

-1 -

  The present invention relates, from a

  in general, to a refrigeration plant and to

  a method of operating a refrigeration plant

  ration of the type which includes a compressor with several cylinders or several compressors and it relates more

  particularly to a process for regulating the functioning

  from a refrigeration installation to temperatures

  ambient temperatures that exceed the operating temperature

the installation.

  During the operation of a cooling installation, when the ambient temperature of the

  surrounding the condenser and the evaporator

  rises above predetermined limits, the temperature

  and the pressure in the condenser increases.

  When the ambient temperature increases beyond the rated temperature range of the installation, the discharge pressure or condenser pressure may

  exceed the operating limits causing the

  end of the refrigeration plant. However, he

  is desirable to maintain the refrigeration

  in operation and continue to provide some cooling during the period in which the ambient temperature exceeds the rated temperature.

  In refrigeration

  of at least two compressors or a compressor having at least two cylinders, the capacity of the compressor has been modified to adapt to the variations in the load that occur when the installation of

  Refrigeration is subject to variations in temperature.

  ambient temperature. It has been desirable in the

-2-

  of the prior art, to reduce the capac-

  the compressor (s) of the refrigeration plant

  when the load on the installation decreases and the capacity of the compressor increases when the load on the installation increases. When the time is

  usually hot, the cooling load or cooling

  that the refrigeration system must satisfy

  increase. To meet these needs, it was born

  use a larger motor to operate the compressor or use a multiple compressor system. Variable capacity refrigeration plants that include two or more compressors or compressors having at least two

  two cylinders connected in parallel are provided with

  yen to load or unload the cylinders in order to

  the capacity of the installation so that it corresponds

  meets the needs of cooling. In these facilities

  tions, the compressor is discharged when the cooling requirements decrease and it is loaded when

  cooling needs increase. This result

  This can be achieved by connecting the discharge side of the compressor to the suction side inside the compressor or by closing it by a bypass line.

  the suction side of a compressor cylinder to the in-

  compressor or by shutting down one or more of the compressors in a group of compressors. In bypass capacity offload facilities, solenoid valves are typically mounted in branch lines that extend between the

  discharge pipe of each of the cylinders of the com-

  presser and the suction line of the compressor.

  When opening the tap, a portion of the compressed gas

  flows directly from the discharge pipe

  than the suction side of the compressor without passing through the condenser and evaporator, thus reducing the

  amount of refrigerant flowing through the

  and limits the load imposed on the combustion engine.

  presser. To increase the capacity of the compressor,

  closes one or more of the valves in the

  derivation. These facilities are designed to operate within specific ambient temperature ranges. One of the aims of the present invention is

  to improve the operation of

  frigmentation when the ambient temperature increases

  above predetermined limits.

  Another object of the present invention is to

  to realize control means which operate in re-

  response to increasing ambient temperature or

  discharge pressure above pre-defined limits

  determined to maintain the refrigeration

  operating under temperature conditions.

high ambient temperatures.

  Yet another object of the present invention

  O20 is to achieve simple, reliable, fully

  automatically in refrigeration plants.

  to allow these installations to operate at ambient temperatures above a predetermined level.

  These goals as well as other goals of the pre-

  invention are achieved by detecting the temperature

  room temperature or the discharge pressure of the refrigerant and unloading the compressor in response

  at an ambient temperature or at a refilling pressure

  maximum, thus reducing the flow of fri-

  This leads to a decrease in the condenser's flow rate through the condenser. this allows

  at the facility to operate at a relative capacity

  reduced during periods of ambient temperature

high.

  Other features of the invention

  will appear on the following description

  and examining the accompanying drawing in which:

  FIG. 1 is a schematic view of an

  refrigeration plant which represents an embodiment of the invention in which the unloading of the compressor is provided by means responsive to the pressure of the high pressure side of the plant; FIG. 2 is a partial schematic view

  which represents another circuit in which the discharge-

  The refrigeration system is provided by means sensitive to ambient temperature; and FIG. 5 is a partial circuit diagram showing the connection between a switch controlled by the high pressure and unloading means for the air conditioning installation which comprises several

  rows of cylinders according to the invention.

  Reference is now made to the drawings; it can be seen that FIG. 1 represents a refrigeration installation which comprises a compressor 10 with several

  cylinders comprising two cylinders 11 and 12.

  Discharge lines 13 and 14 start respectively

  cylinder 11 and cylinder 12 and allow the flow of

  refrigerant gas from the compressor 10

only to a condenser 15.

  It should be noted that the compressor 10 is not

  limited to two cylinders but may

  other cylinders connected to the condenser 15 in the same way as the cylinders 11 and 12.

  compressors can also be used

  instead of the compressor cylinders 10.

  The hot gaseous refrigerant discharged by the compressor 10 is converted into liquid in the condenser 15 because the gaseous refrigerant circulates in the condenser in an exchange relationship.

  heat with ambient air or other

  froidissement. The liquid refrigerant then flows through an expander device 16 to a

  evaporator 17. In the evaporator, the refrigerant

  The liquid gene evaporates by absorbing the heat of the medium to cool. Refrigerant vapors

  then flow to the compressor through a

  suction pipe 19. A check valve 18 is

  mounted in line 14 to allow the fluid

  gorigene to flow from the cylinder 12 by the

  delivery line 14 to the condensate coil

  and to prevent the flow of refrigerant

  Discharge line gene 13 in the line 14. An unloading valve 20 is mounted in a bypass line 22 which connects the discharge line 14 to the suction side of the compressor. As a discharge valve 20, a conventional solenoid valve may be used. Typically, if the solenoid valve coil 20 is not energized,

  the valve plunger closes the pipe and the gas

  stepped into the discharge line 14 is not

  riveted back to the suction side of the compressor. The

  two cylinders of the compressor are in operation and the

  tallation is able to operate at full capacity.

  The solenoid coil of the valve 20 can be selectively

  excited by the electric circuit 21 shown

  in FIG. 1 which comprises a controlled switch

  property 23 and a source 24 of the electric current. The

  circuit for energizing the discharge cock

  Charging may consist of a portion of the electrical circuit used for the entire refrigeration system. The switch 25 is a normally open switch which is connected to a high pressure control, such as a bellows controlled by the pressure or pressure capsule 25. One end of the bellows is connected by a linkage to the electrical contact of the switch 23. The opposite end of the souf-flet 25

  is connected to the discharge pipe 14 of the com-

  pressure by a conduit 26 which controls the pipe 14 pressure discharge. An increase in

  pressure in line 14 causes the expan-

  bellows 25 and when a predetermined pressure

  is reached, the bellows 25 closes the switch 23.

  The bellows 25 is preset to close the switch

  23 at the highest discharge pressure

  sible for the refrigeration plant.

  Although the conduit 26 has been shown connected to the discharge line 14, it may, for the purpose of the present invention, be connected to any point on the high pressure side of the installation which

  is capable of constituting a source of refrigerant

high pressure gene.

  In use, when the ambient temperature increases, there is an increase in the load

  of cooling imposed on the installation and an

  corresponding increase in the pressure load of the

  condenser. In conditions such as temperature,

  ambient temperature exceeds a predetermined limit, the

  flet 25 reacts by closing the electrical contacts of the switch 25, thus closing an electrical circuit which causes the excitation of the valve coil 20 to

  solenoid. The excitation of the solenoid valve coil

  Noide moves the solenoid valve plunger in a direction that opens the bypass line 22. Due to the opening of the solenoid valve 20, a portion of the discharged hot gas flows into the discharge line 14. by the line 22 directly to the suction side of the compressor 10, without passing through the condenser 15, the expander 16 and the evaporator 17, thereby reducing the flow of fluid -7-

  refrigerant circulating in the refrigeration

  ration. This reduces the load on the compressor and condenser. When the flow of refrigerant flowing to the condenser is limited, the pressure in the condenser is lowered. The weakest

  pressure in the condenser allows the installation to

  refrigeration to continue to operate at a reduced capacity even if the ambient temperature exceeds

  the nominal limits of the installation as a whole

  corn. It should be noted that the compressor is discharged or stopped by a monomer controlled by the discharge pressure as the plant approaches its maximum operating pressure. The interval between the closing pressure and the opening pressure of

  this manometer is large enough that the reduction

  pressure caused by the unloading of the

  presser or the stop of a compressor does not reopen the switch, reloading or restarting, therefore, the compressor. Since there is a direct relationship between the outside temperature and the discharge pressure, a lowering of the ambient temperature is necessary before the pressure gauge reopens and recharges or re-starts the compressor. At this reduced ambient temperature, the installation works

  with the compressor fully charged. The process

  above described compressor unloading when the pressure load approaches the maximum allowed for the operation of the installation allows the facility to continue operating at a reduced capacity but

  at a higher ambient temperature.

  It should be noted that, although

  in the preferred embodiment, the solenoid valve

  placed on the outside of a driving line

  Alternatively, in the installation, a valve positioned internally in a bypass pipe extending from the discharge side to the side can be used in the installation.

  suction inside the envelope of a compres-

  sor. Fig. 2 shows a partial view of the circuit, similar to that shown in FIG. 1

  in which a normally open switch is connected

  corded to a thermostat or probe 30 detecting the temperature

  ambient temperature. The unloading of the compressor is

  in response to the temperature sensed by the thermostat 30 which is set to close the contacts of the switch 23 at a predetermined maximum ambient temperature. Fig. 3 shows an electrical diagram showing a connection between an electric switch 23 and unloading valves 20 in the case where a compressor provided with several rows of cylinders or

  several compressors are used in the installation

  tion. Fig. 3 represents, for example, a compressor

  four-cylinder. When the pressure load is

  believes in the maximum allowed for the functioning of the

  the electrical switch 23 is closed,

  the unloading valves 20.

  The number of electrical switches and

  discharge valves, used, naturally depend on

  of the particular installation and application

tion in question.

  In addition, various interruptions

  23 in combination with other

  loading and other bypass lines to produce sequential discharge of compressors

  when the ambient temperature rises.

  Although the invention has been represented in

  Referring to a preferred embodiment, it is recom-

  naltra that variations and changes can be made without departing from the scope of the invention, such as

  specified in the claims.

_c.

- REV "T DICAZCI- -;

  1 - Method of operating an installation

  A refrigeration process of the type comprising a plurality of compressors (10) or a multi-cylinder compressor (10) (11, 12) characterized in that the refrigeration plant is operated to its full capacity , to detect

  - conditions which indicate the load imposed on the installation

  partially unload the compressor when conditions indicate that the load imposed on the

  the installation is greater than the operating load

  are detected and continue to operate.

  the refrigeration plant with

  until conditions indicate that the load on the installation is reduced to

  normal operating load are detected.

  2 - Method of operating an installation

  refrigeration system according to claim 1 characterized

  in that the partial unloading of the compressor comprises the step of conveying the gas discharged by some of the cylinders or compressors directly

  to the suction line of the compressor.

  3 - Operating method of an installation

  refrigeration system according to one of claims 1 and 2

  characterized in that it further comprises the step of detecting the discharge pressure in the discharge line of the compressor and discharging

  the compressor when the discharge pressure detects

  exceeds the normal operating pressure.

  4 - Method of operating an installation

  refrigeration system according to one of claims 1

  and 2 characterized in that it comprises, besides, the step of detecting the ambient temperature and discharging the compressor when the ambient temperature

  detected exceeds the predetermined maximum temperature.

  -10- - Gas compressor control characterized by comprising a bypass line (22) connecting the discharge side of the compressor to the inlet of the compressor, a valve (20) mounted in the bypass line ( 22) to control the flow

  high pressure gases on the pressure side of the compressor

  until the compressor inlet, an electrical circuit

  cradle (21) operably connected to the valve (20) to open the valve (20), switch means (23) mounted in the electrical circuit (21) for energizing and de-energizing it thereby controlling the operation of the tap (20) and the means

  (25) condition detectors connected to the in-

  interrupters (23) to close them in response to conditions

  in which the ambient temperature exceeds

  the predetermined limit allowed for installation.

  6 - Control device for a plant

  with an evaporator (17), a compressor

  Multi-cylinder (11, 12) or

  pressers (10) and a condenser (15) connected in a closed circuit to allow the circulation of a fluid

  refrigerant, characterized in that it comprises a

  bypass duct (22) which connects the discharge line (14) of a cylinder (12) of the compressor or compressor (10) to the suction line of the compressor (10), a valve (20) to mounted solenoid

  in the branch bypass (22) to open and close

  this bypass line, an electrical circuit (21) having a switch (23) normally closed and electrically connected to the solenoid valve, a manometric capsule (25) connected to the

  discharge of the compressor (10) and operating in

  in response to a predetermined pressure load in the discharge line (14), this pressure capsule

  (25) being operably connected to the interrup-

  -11- electric unit (23) to close the electrical circuit and open the bypass line (22) to direct

  the gas discharged from some of the cylinders (12) or

  pressers (IC) to the suction line of the

  pressing member (10) when the pressure of the

  flow decreases the maximum operating pressure.