U.S. patent application number 13/993847 was filed with the patent office on 2013-11-14 for thermodynamic system provided with a plurality of compressors.
This patent application is currently assigned to DANFOSS COMMERCIAL COMPRESSORS. The applicant listed for this patent is Patrice Bonnefoi, Fabien Gall. Invention is credited to Patrice Bonnefoi, Fabien Gall.
Application Number | 20130298594 13/993847 |
Document ID | / |
Family ID | 45401096 |
Filed Date | 2013-11-14 |
United States Patent
Application |
20130298594 |
Kind Code |
A1 |
Bonnefoi; Patrice ; et
al. |
November 14, 2013 |
THERMODYNAMIC SYSTEM PROVIDED WITH A PLURALITY OF COMPRESSORS
Abstract
The thermodynamic system includes a circuit for circulating a
refrigerant including a compression device including a first and a
second compressors each including a sealed enclosure including a
low-pressure portion containing a motor and an oil pan positioned
at the bottom of the enclosure, and a refrigerant intake opening
leading into the low-pressure portion, a refrigerant dispensing
device arranged to connect an evaporator to the intake opening of
the first compressor, an oil level equalization conduit putting the
oil pans of the first and second compressors in communication, a
connecting device putting the low-pressure portion of the first
compressor in communication with the intake opening of the second
compressor, and control means arranged to control the starting and
stopping of the first and second compressors according to four
control modes.
Inventors: |
Bonnefoi; Patrice; (Saint
Didier Au Mont D'or, FR) ; Gall; Fabien; (Cailloux
Sur Fontaines, FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Bonnefoi; Patrice
Gall; Fabien |
Saint Didier Au Mont D'or
Cailloux Sur Fontaines |
|
FR
FR |
|
|
Assignee: |
DANFOSS COMMERCIAL
COMPRESSORS
TREVOUX
FR
|
Family ID: |
45401096 |
Appl. No.: |
13/993847 |
Filed: |
November 28, 2011 |
PCT Filed: |
November 28, 2011 |
PCT NO: |
PCT/FR11/52783 |
371 Date: |
July 24, 2013 |
Current U.S.
Class: |
62/468 |
Current CPC
Class: |
F04B 39/121 20130101;
F25B 41/00 20130101; F25B 2600/0251 20130101; F04C 28/02 20130101;
F25B 1/10 20130101; F04C 18/0215 20130101; F04B 41/06 20130101;
F04C 28/065 20130101; F04C 2270/24 20130101; F25B 2400/075
20130101; F04C 23/001 20130101; F25B 31/004 20130101; F04C 2240/806
20130101; F25B 49/022 20130101; F04B 39/0207 20130101; F04B 49/02
20130101; F04C 23/008 20130101 |
Class at
Publication: |
62/468 |
International
Class: |
F25B 1/10 20060101
F25B001/10; F25B 41/00 20060101 F25B041/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 13, 2010 |
FR |
1060418 |
Claims
1. A thermodynamic system, comprising: a circuit for circulating a
refrigerant successively including a condenser, an expander, an
evaporator and a compression device connected in series, the
compression device comprising at least one first compressor and one
second compressor mounted in parallel, each compressor comprising a
sealed enclosure including on the one hand a low-pressure portion
containing a motor and an oil pan positioned at the bottom of the
enclosure, and on the other hand a refrigerant intake opening
leading into the low-pressure portion, and a refrigerant dispensing
device arranged to connect the evaporator to an intake opening of
the first compressor, an oil level equalization conduit putting the
oil pans of the first and second compressors in communication, a
connecting device putting the low-pressure portion of the first
compressor in communication with the intake opening of the second
compressor, such that all of the refrigerant penetrating the
low-pressure portion of the second compressor comes from the
low-pressure portion of the first compressor, and control means
arranged to control the starting and stopping of the first and
second compressors, wherein the control means are arranged to
control the starting and stopping of the first and second
compressors according to: a first control mode, in which the
control means control the starting of the first and second
compressors, a second control mode, in which the control means
control the starting of the first compressor and the stopping of
the second compressor, a third control mode, in which the control
means control the stopping of the first compressor and the starting
of the second compressor, and a fourth control mode, in which the
control means control the stopping of the first and second
compressors, and the oil level equalization conduit includes an end
portion turned toward the first compressor side and protruding
inside the sealed enclosure of said first compressor, said end
portion including an end wall extending transversely to the
longitudinal direction of said end portion and an opening formed
above the end wall such that, when the oil level in the oil pan of
the first compressor extends above the upper level of said end
wall, oil flows through said opening toward the second
compressor.
2. The thermodynamic system according to claim 1, wherein at least
one of the first and second compressors is a variable-capacity
compressor, or wherein the first and second compressors are
fixed-capacity compressors and have a capacity ratio comprised
between 1.5 and 3.
3. The thermodynamic system according to claim 1, wherein the oil
level equalization conduit is arranged and sized such that, when
the system is in the overheated steady state, an upper portion of
the flow cross-section of the equalization conduit is situated
above the oil levels in the oil pans of the first and second
compressors so as simultaneously to allow the transfer of oil and
refrigerant between the first and second compressors.
4. The thermodynamic system according to claim 1, wherein the end
portion of the oil level equalization conduit turned toward the
first compressor side includes an oil return opening formed in a
lower part of said end portion situated below the upper level of
the end wall.
5. The thermodynamic system according to claim 1, wherein one of
the first and second compressors is a variable-capacity compressor,
and the other of the first and second compressors is a
fixed-capacity compressor.
6. The thermodynamic system according to claim 5, wherein the
thermodynamic system comprises controlling means arranged to
modulate the capacity of the variable-capacity compressor between a
minimum capacity value and a maximum capacity value.
7. The thermodynamic system according to claim 1, wherein the first
and second compressors are fixed-capacity compressors, the capacity
of the first compressor being larger than that of the second
compressor.
8. The thermodynamic system according to claim 1, wherein the
compression device comprises a third compressor mounted in series
with the first compressor and upstream therefrom, the dispensing
device comprising a first dispensing conduit putting the evaporator
in communication with the intake opening of the third compressor,
and the second dispensing conduit putting the low-pressure portion
of the third compressor in communication with the intake opening of
the first compressor such that all of the refrigerant penetrating
the low-pressure portion of the first compressor comes from the
low-pressure portion of the third compressor.
9. The thermodynamic system according to claim 1, wherein the
compression device comprises a fourth compressor mounted in
parallel with the second compressor, the connecting device
comprising a connecting conduit connected to the low-pressure
portion of the first compressor, a first bypass conduit putting the
connecting conduit in communication with the intake opening of the
second compressor, and a second bypass conduit putting the
connecting conduit in communication with the intake opening of the
fourth compressor.
10. The thermodynamic system according to claim 1, wherein the
connecting device comprises a connecting conduit putting the
low-pressure portion of the first compressor in communication with
the intake opening of the second compressor.
11. The thermodynamic system according to claim 10, wherein the end
of the connecting conduit turned toward the first compressor
protrudes inside the enclosure of the first compressor.
12. The thermodynamic system according to claim 1, wherein each
compressor is a scroll refrigeration compressor.
13. The thermodynamic system according to claim 12, wherein the
first compressor comprises a fixed volute and a moving volute
following an orbital movement, a body on which the moving volute
bears, an intermediate casing fixed on the body and inside which
the motor is mounted, and at least one oil return conduit extending
at least partially over the outer wall of the intermediate casing,
the oil return conduit including a first end turned toward the body
and inserted in an opening formed in the body, and a second end
leading near the oil pan.
14. The thermodynamic system according to claim 1, wherein at least
the first compressor comprises first deflecting means positioned in
the sealed enclosure of said first compressor and whereof at least
one portion is positioned across from the intake opening of said
first compressor, the first deflecting means being arranged to
orient at least a portion of the refrigerant penetrating the
low-pressure portion of the first compressor along at least one
portion of the inner wall of the sealed enclosure of said first
compressor.
15. The thermodynamic system according to claim 1, wherein at least
the first compressor comprises second deflecting means positioned
in the sealed enclosure of said first compressor and whereof at
least one portion is positioned across from the end of the
connecting device turned toward the first compressor side, the
second deflecting means being arranged to orient the refrigerant
penetrating the low-pressure portion of the first compressor
following an ascending, then descending movement before the flow
thereof through the connecting device.
Description
[0001] The present invention relates to a thermodynamic system
provided with a plurality of compressors.
[0002] A thermodynamic system, and more particularly a
refrigeration system, comprises, in a known manner:
[0003] a circuit for circulating a refrigerant successively
including a condenser, an expander, an evaporator and a compression
device connected in series, the compression device comprising at
least one first compressor and one second compressor mounted in
parallel, each compressor comprising an enclosure including a
low-pressure portion containing a motor and an oil pan positioned
at the bottom of the enclosure on the one hand, and a refrigerant
intake opening leading into the low-pressure portion on the other
hand, and
[0004] a refrigerant dispensing device comprising a dispensing
conduit connected to the evaporator, a first bypass conduit putting
the dispensing conduit in communication with the intake opening of
the first compressor, and a second bypass conduit putting the
dispensing conduit in communication with the intake opening of the
second compressor.
[0005] In order to ensure proper operation and reliability of such
a refrigeration system, it is necessary to balance the oil levels
in the oil pans of the two compressors. This balancing of the oil
levels is advantageously obtained by connecting the oil pans of the
two compressors using an oil level equalization conduit favoring
the transfer of oil between the two compressors, and connecting the
low-pressure portions of the two compressors by means of a pressure
equalization conduit favoring the transfer of refrigerant between
the two compressors.
[0006] Such a refrigeration system has the drawback of requiring a
complex dispensing device and a pressure equalization conduit due
to the parallel assembly of the first and second compressors.
[0007] Document U.S. Pat. No. 3,785,169 describes a refrigeration
system comprising:
[0008] a circuit for circulating a refrigerant successively
including a condenser, an expander, an evaporator and a compression
device connected in series, the compression device comprising at
least one first compressor and one second compressor, each
compressor comprising an enclosure including a low-pressure portion
containing a motor and an oil pan positioned in the bottom of the
enclosure on the one hand, and a refrigerant intake opening leading
into the low-pressure portion on the other hand,
[0009] a refrigerant dispensing device arranged to connect the
evaporator to the intake opening of the first compressor,
[0010] an oil level equalization conduit putting the oil pans of
the first and second compressors in communication,
[0011] a connecting device putting the low-pressure portion of the
first compressor in communication with the intake opening of the
second compressor, such that all of the refrigerant penetrating the
low-pressure portion of the second compressor comes from the
low-pressure portion of the first compressor, and
[0012] control means arranged to control the starting and stopping
of the first and second compressors.
[0013] Such an assembly of the first and second compressors makes
it possible to ensure satisfactory balancing of the oil levels in
each compressor, without needing to provide a pressure equalization
conduit between the latter and a complex dispensing device. This
results in obtaining a refrigeration system with a simpler and more
cost-effective structure.
[0014] However, such a refrigeration system has the drawback of
only having two capacity stages, due to the fact that the control
means are arranged necessarily to control the starting of the first
compressor under operating conditions of the system.
[0015] This results in a refrigeration system that may be
relatively ineffective under certain operating conditions.
[0016] The present invention aims to resolve this drawback.
[0017] The technical problem at the base of the invention therefore
consists of providing a thermodynamic system, and in particular a
refrigeration system, that has a simple and cost-effective
structure, while preserving satisfactory efficiency irrespective of
the operating conditions of the refrigeration system.
[0018] To that end, the present invention relates to a
thermodynamic system of the aforementioned type, characterized in
that the control means are arranged to control the starting and
stopping of the first and second compressors according to:
[0019] a first control mode, in which the control means control the
starting of the first and second compressors,
[0020] a second control mode, in which the control means control
the starting of the first compressor and the stopping of the second
compressor,
[0021] a third control mode, in which the control means control the
stopping of the first compressor and the starting of the second
compressor, and
[0022] a fourth control mode, in which the control means control
the stopping of the first and second compressors,
[0023] and in that the oil level equalization conduit includes a
portion turned toward the first compressor side and protruding
inside the enclosure of said first compressor, said end portion
including an end wall extending transversely to the longitudinal
direction of said end portion and an opening formed above the end
wall such that, when the oil level in the oil pan of the first
compressor extends above the upper level of said end wall, oil
flows through said opening toward the second compressor.
[0024] In the case where at least one of the first and second
compressors is a variable-capacity compressor, or in the case where
the first and second compressors are fixed-capacity compressors and
have a capacity ratio comprised between 1.5 and 3, controlling the
starting and stopping of the first and second compressors according
to the third control mode makes it possible to obtain an additional
capacity stage, which makes it possible to improve the efficiency
of the compression system under certain operating conditions
thereof. For example, when the first compressor is a
variable-capacity compressor and the second compressor is a
fixed-capacity compressor larger than the maximum capacity of the
first compressor, it is possible, using this third control mode, to
obtain an intermediate capacity between that obtained with the
first compressor at maximum capacity and the second compressor
stopped and that obtained with the first compressor at minimum
capacity and the second compressor running.
[0025] The control of the starting and stopping of the first and
second compressors according to the third control mode also makes
it possible to favor the use of the second compressor when the
latter has better efficiency than the first compressor for given
operating conditions, for example when the first and second
compressors are scroll compressors and the second compressor has a
different compression ratio from the first compressor, or the
second compressor has at least one bypass valve associated with the
bypass passage formed in the plate of the fixed volute and arranged
to put a discharge chamber in communication with an intermediate
compression chamber defined by the scrolls of the fixed and moving
volutes.
[0026] Controlling the starting and stopping of the first and
second compressors according to the third control mode also makes
it possible to favor the use of the second compressor during cycle
inversions so as to provide better protection for the system
against liquid "blows."
[0027] Furthermore, the configuration of the end portion of the oil
level equalization conduit turned toward the first compressor, and
more particularly the arrangement of an opening above the end wall
of the end portion, allows the flow of oil from the first
compressor toward the second compressor when the quantity of oil in
the first compressor exceeds a predetermined value, and prevents or
at least limits such a flow of oil when the quantity of oil in the
first compressor is below a predetermined value. These arrangements
thus make it possible to ensure the presence of a minimum quantity
of oil in the first compressor when the second compressor is
running.
[0028] Advantageously, the thermodynamic system is a refrigeration
system, and advantageously a reversible refrigeration system.
[0029] When the first and second compressors are fixed-capacity
compressors, the capacity ratio between the first and second
compressors is preferably comprised between 1.5 and 2.5, and
advantageously between 1.7 and 2.3. Given the value range from
which the capacity ratio can be chosen, one of the first and second
compressors necessarily has a so-called "higher" capacity and the
other compressor has a so-called "lower" capacity, one or the other
of the first and second compressors being able to have a higher or
lower capacity. The capacity ratio then refers to the ratio of the
upper capacity to the lower capacity.
[0030] Advantageously, the first compressor includes a connecting
opening leading into the low-pressure portion of the first
compressor, the connecting device putting the connecting opening of
the first compressor in communication with the intake opening of
the second compressor.
[0031] Advantageously, the oil level equalization conduit is
arranged and sized such that, when the system is in the overheated
steady state, an upper portion of the flow cross-section of the
equalization conduit is situated above the oil levels in the oil
pans of the first and second compressors so as simultaneously to
allow the transfer of oil and refrigerant between the first and
second compressors.
[0032] The overheated steady state refers to a steady state of the
thermodynamic system in which the suction temperature of the
refrigerant at the intake opening of the first compressor is higher
than the saturation temperature of the refrigerant at the suction
pressure of the refrigerant at said intake opening, i.e., a
permanent state in which the refrigerant at the intake opening of
the first compressor has no refrigerant in liquid form (the latter
may, however, include oil droplets).
[0033] Such a configuration of the oil level equalization conduit
ensures a transfer of oil between the enclosures of the first and
second compressors, as well as a limitation of the pressure
deviations between the latter. Such a configuration also makes it
possible to reduce the flow speed of the refrigerant at the end of
the connecting device turned toward the first compressor side, and
therefore to decrease the quantity of oil driven toward the second
compressor by means of said connecting device.
[0034] Preferably, the oil level equalization conduit is
substantially horizontal and includes two ends positioned
substantially at the same altitude, said altitude being
predetermined so as to ensure a minimal oil level in each
compressor.
[0035] Preferably, the opening extends over at least one portion of
the side wall of said end portion. This results in a reduction of
the speed of the refrigerant at the free surface of the oil pan,
and therefore a limitation of the quantity of oil driven by the
first compressor toward the second compressor when the second
compressor is running.
[0036] Preferably, the end portion of the oil level equalization
conduit turned toward the first compressor side includes an oil
return opening formed in the lower part of said end portion
situated below the upper level of the end wall. These arrangements
ensure a return of oil toward the oil pan of the first compressor
when the second compressor is stopped, and thereby prevent oil
storage beyond a predetermined level inside the enclosure of the
second compressor.
[0037] According to a first alternative of the invention, one of
the first and second compressors is a variable-capacity compressor,
and the other of the first and second compressors is a
fixed-capacity compressor.
[0038] According to this first alternative of the invention, the
thermodynamic system comprises controlling means arranged to
modulate the capacity of the variable-capacity compressor,
preferably continuously, between a minimum capacity value and a
maximum capacity value.
[0039] Preferably, the first compressor is the variable-capacity
compressor. According to one embodiment, the second fixed-capacity
compressor has a higher capacity than the maximum capacity of the
first compressor.
[0040] Advantageously, the motor of the variable-capacity
compressor is a variable-speed motor. In this case, the controlling
means are arranged to modulate the speed of the motor of the
variable-capacity compressor between a minimum speed and a maximum
speed.
[0041] According to a second alternative of the invention, the
first and second compressors are fixed-capacity compressors, the
capacity of the first compressor being larger than that of the
second compressor.
[0042] According to one embodiment, the compression device
comprises a third compressor mounted in series with the first
compressor and upstream therefrom, the dispensing device comprising
a first dispensing conduit putting the evaporator in communication
with the intake opening of the third compressor, and the second
dispensing conduit putting the low-pressure portion of the third
compressor in communication with the intake opening of the first
compressor such that all of the refrigerant penetrating the
low-pressure portion of the first compressor comes from the
low-pressure portion of the third compressor.
[0043] According to one embodiment, the compression device
comprises a fourth compressor mounted in parallel with the second
compressor, the connecting device comprising a connecting conduit
connected to the low-pressure portion of the first compressor, a
first bypass conduit putting the connecting conduit in
communication with the intake opening of the second compressor, and
a second bypass conduit putting the connecting conduit in
communication with the intake opening of the fourth compressor.
[0044] The connecting conduit and the bypass conduits for example
have a substantially identical flow cross-section.
[0045] According to another embodiment, the connecting device
comprises a connecting conduit putting the low-pressure portion of
the first compressor in communication with the intake opening of
the second compressor.
[0046] Advantageously, the oil level equalization conduit has a
flow cross-section of approximately 0.5 to 1 times the flow
cross-section of the connecting conduit.
[0047] Advantageously, the end of the connecting conduit turned
toward the first compressor protrudes inside the enclosure of the
first compressor.
[0048] Preferably, each compressor is a scroll refrigeration
compressor. Preferably, the first compressor comprises a fixed
volute and a moving volute following an orbital movement, a body on
which the moving volute bears, an intermediate casing fixed on the
body and inside which the motor is mounted, and at least one oil
return conduit extending at least partially over the outer wall of
the intermediate casing, the oil return conduit including a first
end leading, preferably sealably, into the body, and a second end
leading near the oil pan. These arrangements make it possible to
further limit the quantity of oil driven from the first compressor
toward the second compressor through the connecting device.
[0049] According to one embodiment of the invention, at least the
first compressor comprises first deflecting means positioned in the
enclosure of said first compressor and whereof at least one portion
is positioned across from the intake opening of said first
compressor, the deflecting means being arranged to orient at least
a portion of the refrigerant penetrating the low-pressure portion
of the first compressor along at least one portion of the inner
wall of the sealed enclosure of said first compressor. These
arrangements make it possible to increase the journey of the
refrigerant inside the first compressor, and therefore the
separation of the oil/refrigerant mixture in the enclosure of the
first compressor. This results in limiting the quantity of oil
driven from the first compressor toward the second compressor.
[0050] Preferably, the first deflecting means include a sintered
plate fastened on the inner wall of the sealed enclosure so as to
define a refrigerant circulation passage therewith.
[0051] According to one embodiment of the invention, at least the
first compressor comprises second deflecting means positioned in
the enclosure of said first compressor and whereof at least one
portion is positioned across from the end of the connecting device
turned toward the first compressor side, the deflecting means being
arranged to orient the refrigerant penetrating the low-pressure
portion of the first compressor following an ascending, then
descending movement before the flow thereof through the connecting
device. These arrangements make it possible to reduce the speed of
the refrigerant inside the enclosure of the first compressor, and
therefore to improve the separation of the oil/refrigerant mixture
in the enclosure of the first compressor. This results in still
further limiting the quantity of oil driven from the first
compressor toward the second compressor.
[0052] In any case, the invention will be well understood using the
following description in reference to the appended diagrammatic
drawing showing, as non-limiting examples, several embodiments of
this thermodynamic system.
[0053] FIG. 1 is a diagrammatic view of a thermodynamic system
according to a first alternative embodiment of the invention.
[0054] FIG. 2 is a partial diagrammatic view of the thermodynamic
system of FIG. 1.
[0055] FIG. 3 is a partial cross-sectional diagrammatic view of the
thermodynamic system of FIG. 1.
[0056] FIGS. 4a and 4b are respectively perspective and top views
of an end portion of the connecting device of a thermodynamic
system according to a second alternative embodiment of the
invention.
[0057] FIG. 5 is a partial cross-sectional diagrammatic view of the
thermodynamic system according to a third alternative embodiment of
the invention.
[0058] FIG. 6 is a transverse cross-sectional view of the first
compressor of the thermodynamic system of FIG. 5.
[0059] FIG. 7 is a diagrammatic view of a thermodynamic system
according to a fourth alternative embodiment of the invention.
[0060] FIG. 8 is a perspective view of the deflecting means
equipping the first compressor of the thermodynamic system of FIG.
7.
[0061] FIG. 9 is a diagrammatic view of a thermodynamic system
according to a fifth alternative embodiment of the invention.
[0062] FIG. 10 is a diagrammatic view of a thermodynamic system
according to a sixth alternative embodiment of the invention.
[0063] FIG. 11 is a diagrammatic view of a thermodynamic system
according to a seventh alternative embodiment of the invention.
[0064] FIG. 1 diagrammatically shows the main components of a
thermodynamic system 1 according to the invention, and more
particularly of a refrigeration system.
[0065] The refrigeration system 1 comprises a circuit 2 for
circulating refrigerant successively including a condenser 3, an
expander 4, an evaporator 5 and a compression device 6 connected in
series.
[0066] The compression device 6 comprises a first variable-capacity
compressor 7 and a second fixed-capacity compressor 8. Each
compressor 7, 8 is advantageously a scroll refrigeration
compressor. Each compressor 7, 8 comprises a sealed enclosure 9
including a low-pressure portion 11 containing the motor 12 and an
oil pan 13 positioned at the bottom of the sealed enclosure, and a
high-pressure portion 14, positioned above the low-pressure portion
11, containing a compression stage.
[0067] The sealed enclosure 9 of each compressor also includes a
refrigerant intake opening 15 leading into an upper portion of the
low-pressure portion 11, an equalization opening 16 leading into
the oil pan 13, and a discharge opening 17 leading into the
high-pressure portion 14.
[0068] The sealed enclosure 9 of the first compressor 7 also
comprises a connecting opening 18 leading into an upper portion of
the low-pressure portion 11 of the first compressor.
[0069] The refrigeration system 1 also comprises a refrigerant
dispensing device. The dispensing device comprises a dispensing
conduit 19 putting the evaporator 5 in communication with the
intake opening 15 of the first compressor 7.
[0070] The refrigeration system 1 also comprises an oil level
equalization conduit 21 connecting the equalization openings 16 of
the two compressors and thereby putting the oil pans 13 of the
first and second compressors 7, 8 in communication.
[0071] The refrigeration system 1 also comprises a connecting
device including a connecting conduit 22 connecting the connecting
opening 18 of the first compressor with the intake opening 15 of
the second compressor and thereby putting the low-pressure portions
11 of the first and second compressors in communication, such that
all of the refrigerant penetrating the low-pressure portion of the
second compressor comes from the low-pressure portion of the first
compressor. The end of the connecting conduit 22 turned toward the
first compressor side preferably protrudes inside the sealed
enclosure of the first compressor 7. The connecting conduit 22 is
preferably generally S-shaped.
[0072] The refrigeration system 1 also comprises a refrigerant
discharge device 24. The discharge device 24 comprises a discharge
conduit 25 connected to the condenser 3, the first bypass conduit
26 putting the discharge conduit 25 in communication with the
discharge opening 17 of the first compressor 7, the second bypass
conduit 27 putting the discharge conduit 25 in communication with
the discharge opening 17 of the second compressor 8.
[0073] The refrigeration system 1 also comprises control means 28
arranged to control the starting and stopping of the first and
second compressors, and controlling means 29 arranged to modulate
the speed of the motor 12 of the first compressor 7 between a
minimum speed and a maximum speed.
[0074] The control means 28 are preferably arranged to control the
starting and stopping of the first compressors according to four
control modes, i.e.:
[0075] a first control mode, in which the control means control the
starting of the first and second compressors,
[0076] a second control mode, in which the control means control
the starting of the first compressor and the stopping of the second
compressor,
[0077] a third control mode, in which the control means control the
stopping of the first compressor and the starting of the second
compressor, and
[0078] a fourth control mode, in which the control means control
the stopping of the first and second compressors.
[0079] When the control means control the starting and stopping of
the first and second compressors according to the second control
mode, all of the refrigerant penetrating the low-pressure portion
11 of the first compressor 7 is suctioned in the high-pressure
portion 14 of the first compressor so as to be compressed in the
compression stage thereof, whereas when the control means control
the starting and stopping of the first and second compressors
according to the third control mode, all of the refrigerant
penetrating the low-pressure portion 11 of the first compressor 7
is suctioned in the low-pressure portion 11 of the second
compressor 8 by means of the connecting conduit 22 so as to be
compressed in the compression stage of the second compressor 8.
[0080] When the control means control the starting and stopping of
the first and second compressors according to the first control
mode, a first portion of the refrigerant penetrating the
low-pressure portion 11 of the first compressor 7 is suctioned in
the high-pressure portion 14 of the first compressor so as to be
compressed in the compression stage thereof and a second portion of
the refrigerant penetrating the low-pressure portion 11 of the
first compressor 7 is suctioned in the low-pressure portion 11 of
the second compressor 8 by means of the connecting conduit 22 so as
to be compressed in the compression stage of the second
compressor.
[0081] According to one alternative embodiment of the refrigeration
system shown in FIGS. 4a and 4b, the oil level equalization conduit
21 includes an end portion 31 turned toward the side of the first
compressor 7 and protruding inside the enclosure 9 of the first
compressor. The end portion 31 includes an end wall 32 extending
transversely to the longitudinal direction of the end portion 31
and an opening 33 formed above the end wall 32 such that, when the
oil level in the oil pan 13 of the first compressor 7 extends above
the upper level of the end wall 32, oil flows through the opening
33 toward the second compressor. Preferably, the opening 33 extends
over a portion of the side wall 34 of the end portion 31.
[0082] The end portion 31 also includes an oil return opening 35
formed in the lower portion of the end portion 31 situated below
the upper level of the end wall 32. This position of the oil return
opening 35 ensures a return of oil toward the oil pan 13 of the
first compressor 7 when the second compressor 8 is stopped, and
thereby avoids oil being stored beyond a predetermined level inside
the enclosure of the second compressor.
[0083] According to one alternative embodiment of the refrigeration
system shown in FIGS. 5 and 6, the first compressor 7 comprises
first deflecting means positioned in the enclosure 9 of the first
compressor 7 and whereof a portion is positioned across from the
intake opening 15 of the first compressor, the deflecting means
being arranged to orient at least one portion of the refrigerant
penetrating the low-pressure portion 11 of the first compressor 7
along at least one portion of the inner wall of the sealed
enclosure 9 of the first compressor. Preferably, the first
deflecting means include a sintered plate 40 fixed on the inner
wall of the sealed enclosure 9 so as to define a refrigerant
circulation passage 41 therewith.
[0084] According to one alternative embodiment of the refrigeration
system shown in FIG. 7, the first compressor comprises deflecting
means positioned in the enclosure 9 of the first compressor 7 and
whereof at least one portion is positioned across from the end of
the connecting device turned toward the first compressor side, the
deflecting means being arranged to orient the refrigerant
penetrating the low-pressure portion of the first compressor in an
ascending, then descending movement before it flows through the
connecting device. Preferably, as shown in FIG. 8, the deflecting
means include a plate 42 fastened on the inner wall of the sealed
enclosure 9.
[0085] According to another alternative embodiment of the
refrigeration system shown in FIG. 9, the first compressor
comprises a fixed volute 43 and a moving volute 44 following an
orbital movement, a body 45 on which the moving volute bears, an
intermediate casing 46 fixed on the body 45 and inside which the
motor 12 is mounted, and an oil return conduit 47 extending on the
outer wall of the intermediate casing, the oil return conduit
including a first end leading, preferably sealably, into the body,
and a second end leading near the oil pan 13 of the first
compressor.
[0086] According to another alternative embodiment of the
refrigeration system shown in FIG. 10, the compression device 6
comprises a third compressor 48 mounted in series with the first
compressor 7 and upstream therefrom, the dispensing device
comprising a first dispensing conduit 19a putting the evaporator 5
in communication with the intake opening 15 of the third compressor
48, and a second dispensing conduit 19b putting the low-pressure
portion of the third compressor 48 in communication with the intake
opening 15 of the first compressor 7 such that all of the
refrigerant penetrating the low-pressure portion of the first
compressor 7 comes from the low-pressure portion of the third
compressor 48. According to this alternative embodiment, the
refrigeration system also comprises an oil level equalization
conduit 21' putting the oil pans 13 of the first and third
compressors in communication, and the discharge device 24 also
comprises a third bypass conduit 49 putting the discharge conduit
25 in communication with the discharge opening 17 of the third
compressor 48.
[0087] According to another alternative embodiment of the
refrigeration system shown in FIG. 11, the compression device 6
comprises a fourth compressor 50 mounted in parallel with the
second compressor 8, the connecting device comprising a connecting
conduit 22a connected to the low-pressure portion of the first
compressor 7, a first bypass conduit 22b putting the connecting
conduit 22a in communication with the intake opening 15 of the
second compressor 8, and a second bypass conduit 22c putting the
connecting conduit 22a in communication with the intake opening 15
of the fourth compressor 50. According to this alternative
embodiment, the refrigeration system also comprises an oil level
equalization device putting the oil pans 13 of the first, third and
fourth compressors in communication. The oil level equalization
device comprises the oil level equalization conduit 22 and a bypass
conduit 51 putting the oil level equalization conduit 22 in
communication with the oil pan 13 of the fourth compressor 50.
[0088] The discharge device 24 also comprises a third bypass
conduit 52 putting the discharge conduit 25 in communication with
the discharge opening 17 of the fourth compressor 50.
[0089] It should be noted that the control means 28 are arranged to
control the starting and stopping of the third and/or fourth
compressors.
[0090] The invention is of course not limited solely to the
embodiments of this thermodynamic system described above as
examples, but on the contrary encompasses all alternative
embodiments.
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