U.S. patent application number 12/922950 was filed with the patent office on 2011-02-24 for charge management in refrigerant vapor compression systems.
This patent application is currently assigned to Carrier Corporation. Invention is credited to Alexander Lifson, Michael F. Taras.
Application Number | 20110041523 12/922950 |
Document ID | / |
Family ID | 41319310 |
Filed Date | 2011-02-24 |
United States Patent
Application |
20110041523 |
Kind Code |
A1 |
Taras; Michael F. ; et
al. |
February 24, 2011 |
CHARGE MANAGEMENT IN REFRIGERANT VAPOR COMPRESSION SYSTEMS
Abstract
A refrigerant vapor compression system includes a compression
device, a refrigerant heat rejection heat exchanger, an expansion
device, and a refrigerant heat absorption heat exchanger disposed
in a closed-loop refrigerant circuit in serial refrigerant flow
relationship. A refrigerant storage device is connected by at least
one refrigerant line in fluid communication with the refrigerant
circuit and a flow control device interdisposed in that refrigerant
line. Refrigerant may be selectively withdrawn from and returned to
the high-pressure side of the refrigerant circuit; or withdrawn
from and returned to the low-pressure side of the refrigerant
circuit; or withdrawn from the high-pressure side of the
refrigerant circuit and returned to the low-pressure side of the
refrigerant circuit. The refrigerant may be withdrawn from and
returned to the refrigerant circuit during operation or during an
off-cycle.
Inventors: |
Taras; Michael F.;
(Fayetteville, NY) ; Lifson; Alexander; (Manlius,
NY) |
Correspondence
Address: |
MARJAMA MULDOON BLASIAK & SULLIVAN LLP
250 SOUTH CLINTON STREET, SUITE 300
SYRACUSE
NY
13202
US
|
Assignee: |
Carrier Corporation
Farmington
CT
|
Family ID: |
41319310 |
Appl. No.: |
12/922950 |
Filed: |
May 13, 2009 |
PCT Filed: |
May 13, 2009 |
PCT NO: |
PCT/US09/43770 |
371 Date: |
September 16, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61053169 |
May 14, 2008 |
|
|
|
Current U.S.
Class: |
62/77 ; 62/434;
62/498 |
Current CPC
Class: |
F25B 9/008 20130101;
F25B 45/00 20130101; F25B 2309/061 20130101; F25B 2600/17
20130101 |
Class at
Publication: |
62/77 ; 62/498;
62/434 |
International
Class: |
F25B 45/00 20060101
F25B045/00; F25B 1/00 20060101 F25B001/00; F25D 17/02 20060101
F25D017/02 |
Claims
1. A refrigerant vapor compression system comprising: a refrigerant
compression device, a refrigerant heat rejection heat exchanger for
passing refrigerant received from said compression device at a high
pressure in heat exchange relationship with a cooling medium, and a
refrigerant heat absorption heat exchanger for passing refrigerant
at a low pressure in heat exchange relationship with a medium to be
cooled disposed in serial refrigerant flow communication in a
closed-loop refrigerant circuit; an expansion device disposed in
the closed-loop refrigerant circuit downstream of said refrigerant
heat rejection heat exchanger and upstream of said refrigerant heat
absorption heat exchanger; a refrigerant storage device defining a
storage volume connected by at least one refrigerant line in fluid
communication with said closed-loop refrigerant circuit; and a
refrigerant flow control device interdisposed in said at least one
refrigerant line, said refrigerant flow control device having an
open position wherein refrigerant may flow through said at least
one refrigerant line and a closed position wherein refrigeration is
blocked from flowing through said at least one refrigerant
line.
2. The refrigerant vapor compression system as recited in claim 1
further comprising a controller operatively associated with said
refrigerant flow control device for selectively positioning said
refrigerant flow control device in either an open position or in a
closed position.
3. The refrigerant vapor compression system as recited in claim 1
wherein said at least one refrigerant line connecting the storage
volume of said refrigerant storage device in fluid communication
with said closed-loop refrigerant circuit comprises: a single
refrigerant line in fluid communication with said closed-loop
refrigerant circuit at a location on a high-pressure side of the
refrigerant system.
4. The refrigerant vapor compression system as recited in claim 1
wherein said at least one refrigerant line connecting the storage
volume of said refrigerant storage device in fluid communication
with said closed-loop refrigerant circuit comprises: a single
refrigerant line in fluid communication with said closed-loop
refrigerant circuit at a location on a low-pressure side of the
refrigerant system.
5. The refrigerant vapor compression system as recited in claim 1
wherein said at least one refrigerant line connecting the storage
volume of said refrigerant storage device in fluid communication
with said closed-loop refrigerant circuit comprises: a first
refrigerant line connecting an upper portion of the storage volume
of said refrigerant storage device in fluid communication with said
closed-loop refrigerant circuit at a location on a high-pressure
side of the refrigerant system; and a second refrigerant line
connecting a lower portion of the storage volume of said
refrigerant storage device in fluid communication with said
closed-loop refrigerant circuit at a location on a low-pressure
side of the refrigerant system.
6. The refrigerant vapor compression system as recited in claim 5
wherein a refrigerant flow control device interdisposed in said at
least one refrigerant line comprises: a first refrigerant flow
control device interdisposed in said first refrigerant line; and a
second refrigerant flow control device interdisposed in said second
refrigerant line.
7. The refrigerant vapor compression system as recited in claim 1
wherein said refrigerant vapor compression system operates in a
transcritical cycle at least for a portion of the time.
8. The refrigerant vapor compression system as recited in claim 1
wherein a refrigerant circulating throughout said refrigerant vapor
compression system is carbon dioxide.
9. A refrigerant vapor compression system comprising: a refrigerant
compression device having a refrigerant discharge outlet and a
refrigerant suction inlet, a refrigerant heat rejection heat
exchanger for passing refrigerant received from said compression
device at a high pressure in heat exchange relationship with a
cooling medium, and a refrigerant heat absorption heat exchanger
for passing refrigerant at a low pressure in heat exchange
relationship with a medium to be cooled disposed in serial
refrigerant flow communication in a closed-loop refrigerant
circuit; an expansion device disposed in the closed-loop
refrigerant circuit downstream of said refrigerant heat rejection
heat exchanger and upstream of said refrigerant heat absorption
heat exchanger; and a refrigerant storage device defining a chamber
having an upper zone and a lower zone, the upper zone connected by
a first refrigerant line in fluid communication with a
high-pressure side of said closed-loop refrigerant circuit at a
location upstream, with respect to refrigerant flow, of said
expansion device, the lower zone connected by a second refrigerant
line in fluid communication with a low-pressure side of said
closed-loop refrigerant circuit at a location downstream, with
respect to refrigerant flow, of said expansion device.
10. The refrigerant vapor compression system as recited in claim 9
further comprising: a first refrigerant flow control device
interdisposed in said first refrigerant line; and a second
refrigerant flow control device interdisposed in said second
refrigerant line.
11. The refrigerant vapor compression system as recited in claim 10
wherein each of said first and second refrigerant flow control
devices has an open position and a closed position.
12. The refrigerant vapor compression system as recited in claim 11
wherein each of said first and second refrigerant flow control
devices comprises a solenoid valve having an open position and a
closed position.
13. The refrigerant vapor compression system as recited in claim 10
further comprising a controller operatively associated with each of
said first and second refrigerant flow control devices for
selectively positioning one of said first and second refrigerant
flow control devices in an open position and simultaneously
selectively positioning the other of said first and second
refrigerant flow control devices in a closed position.
14. The refrigerant vapor compression system as recited in claim 9
wherein said refrigerant vapor compression system operates in a
transcritical cycle at least for a portion of the time.
15. The refrigerant vapor compression system as recited in claim 9
wherein a refrigerant circulating throughout said refrigerant vapor
compression system is carbon dioxide.
16. A method for managing refrigerant charge in a refrigerant vapor
compression system operating in a transcritical cycle at least for
a portion of the time, the refrigerant vapor compression system
having a refrigerant compression device, a refrigerant heat
rejection heat exchanger and a refrigerant heat absorption heat
exchanger disposed in serial refrigerant flow communication in a
closed-loop refrigerant circuit, with an expansion device disposed
in the closed-loop refrigerant circuit downstream of the
refrigerant heat rejection heat exchanger and upstream of the
refrigerant heat absorption heat exchanger, said method comprising
the steps of: selectively withdrawing refrigerant from the
closed-loop refrigerant circuit; storing the withdrawn refrigerant
in a refrigerant storage device; and returning the withdrawn
refrigerant from the refrigerant storage device to the closed-loop
refrigerant circuit.
17. The method as recited in claim 16 wherein: the step of
selectively withdrawing refrigerant from the closed-loop
refrigerant circuit is executed during an operating cycle of the
refrigerant vapor compression system; and the step of returning the
withdrawn refrigerant from the refrigerant storage device to the
closed-loop refrigerant circuit is also executed during an
operating cycle of the refrigerant vapor compression system.
18. The method as recited in claim 16 wherein: the step of
selectively withdrawing refrigerant from the closed-loop
refrigerant circuit is executed during an operating cycle of the
refrigerant vapor compression system; and the step of returning the
withdrawn refrigerant from the refrigerant storage device to the
closed-loop refrigerant circuit is executed during an off-cycle of
the refrigerant vapor compression system.
19. The method as recited in claim 16 wherein: the step of
selectively withdrawing refrigerant from the closed-loop
refrigerant circuit is executed during an off-cycle cycle of the
refrigerant vapor compression system; and the step of returning the
withdrawn refrigerant from the refrigerant storage device to the
closed-loop refrigerant circuit is executed during an operating
cycle of the refrigerant vapor compression system.
Description
FIELD OF THE INVENTION
[0001] This invention relates generally to refrigerant vapor
compression systems and, more particularly, to effective
refrigerant charge management in refrigerant vapor compression
systems, including transport refrigeration refrigerant vapor
compression systems using carbon dioxide refrigerant and operating
in a transcritical cycle.
BACKGROUND OF THE INVENTION
[0002] Refrigerant vapor compression systems are well known in the
art and commonly used in transport refrigeration applications for
refrigerating air supplied to a temperature-controlled cargo space
of a truck, trailer, container or the like for transporting frozen
or perishable items. Refrigerant vapor compression systems are also
commonly used in commercial refrigeration installations associated
with supermarkets, convenience stores, restaurants, and other
commercial establishments for refrigerating air supplied to a cold
room or a refrigerated display merchandiser for storing frozen or
perishable food items. Refrigerant vapor compression systems are
also commonly used for conditioning air to be supplied to a
climate-controlled comfort zone within a residence, office
building, hospital, school, restaurant or other facility.
Typically, such refrigerant vapor compression systems include a
compressor, an air-cooled or water-cooled refrigerant heat
rejection heat exchanger which functions as a condenser in
subcritical operation and as a gas cooler in transcritical
operation, a refrigerant heat accepting heat exchanger, which
functions as an evaporator, and an expansion device, commonly a
thermostatic or electronic expansion valve, disposed upstream, with
respect to refrigerant flow, of the heat accepting heat exchanger
and downstream of the heat rejection heat exchanger. These basic
refrigerant system components are interconnected by refrigerant
lines in a closed-loop refrigerant circuit, arranged in accord with
known refrigerant vapor compression cycles.
[0003] Traditionally, most of these refrigerant vapor compression
systems operate at subcritical refrigerant pressures. Refrigerant
vapor compression systems operating in the subcritical range are
commonly charged with conventional fluorocarbon refrigerants such
as, but not limited to, hydrochlorofluorocarbons (HCFCs), such as
R22, and more commonly hydrofluorocarbons (HFCs), such as R134a,
R410A and R407C. In today's market, greater interest is being shown
in "natural" refrigerants, such as carbon dioxide, for use in air
conditioning applications, commercial refrigeration applications,
and transport refrigeration applications, instead of HFC
refrigerants. However, because carbon dioxide has a low critical
temperature, most refrigerant vapor compression systems charged
with carbon dioxide as the refrigerant are designed to operate in
the transcritical pressure regime, at least for a portion of their
operation. For example, transport refrigerant vapor compression
systems having an air-cooled refrigerant heat rejection heat
exchanger operating in environments having ambient air temperatures
in excess of the critical temperature point of carbon dioxide,
31.1.degree. C. (88.degree. F.), must also operate at a compressor
discharge pressure in excess of the critical point pressure for
carbon dioxide, 7.38 MPa (1070 psia) and therefore will operate in
a transcritical cycle. In refrigerant vapor compression systems
operating in a transcritical cycle, the refrigerant heat rejection
heat exchanger operates as a gas cooler rather than a condenser and
operates at a refrigerant temperature and pressure in excess of the
refrigerant's critical point temperature and pressure, while the
evaporator operates at a refrigerant temperature and pressure in
the subcritical range.
[0004] On the low-pressure side of the refrigerant vapor
compression system, that is the portion between the outlet of the
evaporator expansion device and the refrigerant suction inlet to
the compression device, the refrigerant pressure and refrigerant
temperature remain coupled. However, in transcritical operation, on
the high-pressure side of the refrigerant vapor compression system,
that is the portion between the refrigerant discharge outlet of the
compression device and the inlet to the evaporator expansion
device, the refrigerant pressure and refrigerant temperature are
independent of each other. Consequently, refrigerant pressure can
be optimized for only a single design operating point. Therefore,
at off-design conditions, the refrigerant vapor compression system
operation may be sub-optimal as the refrigerant charge will be
either higher or lower than the optimal refrigerant charge at those
conditions.
[0005] U.S. Patent Application Publication No. US/2005/0132729 A1
discloses a transcritical refrigerant vapor compression system
having a refrigerant storage vessel containing a variable mass of
refrigerant, whereby the capacity of the system may be controlled.
In a disclosed embodiment, the refrigerant storage vessel is in
open fluid communication at all times through a single fluid line
with a closed-loop refrigerant circuit at a location upstream, with
respect to refrigerant flow, of the evaporator expansion device and
downstream, with respect to refrigerant flow, of the refrigerant
heat rejection heat exchanger. The mass of refrigerant within the
refrigerant storage vessel is controlled through regulation of the
temperature of the tank or regulation of the storage volume within
the tank, which requires an additional measurable amount of power
provided to a refrigerant system on a permanent or temporary
basis.
SUMMARY OF THE INVENTION
[0006] In an aspect of the invention, a refrigerant vapor
compression system includes a refrigerant compression device, a
refrigerant heat rejection heat exchanger, an expansion device, and
a refrigerant heat absorption heat exchanger disposed in serial
refrigerant flow communication in a closed-loop refrigerant
circuit, a refrigerant storage device defining a storage volume
connected by at least one refrigerant line in fluid communication
with the closed-loop refrigerant circuit, and a flow control device
interdisposed in the at least one refrigerant line. The flow
control device has an open position wherein refrigerant may flow
through the at least one refrigerant line and a closed position
wherein refrigeration is blocked from flowing through the at least
one refrigerant line. In an embodiment, a controller may be
operatively associated with the flow control device for selectively
positioning the flow control device in either an open position or
in a closed position.
[0007] In an embodiment, the storage volume of the refrigerant
storage device is connected by a single refrigerant line in fluid
communication with the closed-loop refrigerant circuit at a
location on a high-pressure side of the refrigerant vapor
compression system upstream, with respect to refrigerant flow, of
the expansion device, which is disposed in the closed-loop
refrigerant circuit downstream of the refrigerant heat rejection
heat exchanger and upstream of the refrigerant heat absorption heat
exchanger. In an embodiment, the storage volume of the refrigerant
storage device is connected by a single refrigerant line in fluid
communication with the closed-loop refrigerant circuit at a
location on a low-pressure side of the refrigerant vapor
compression system downstream, with respect to refrigerant flow, of
the expansion device.
[0008] In an aspect of the invention, a refrigerant vapor
compression system includes a refrigerant compression device, a
refrigerant heat rejection heat exchanger, an expansion device, and
a refrigerant heat absorption heat exchanger disposed in serial
refrigerant flow communication in a closed-loop refrigerant
circuit, and a refrigerant storage device defining a storage volume
having an upper zone and a lower zone, with the upper zone
connected by a first refrigerant line in fluid communication with
said closed-loop refrigerant circuit at a location on a
high-pressure side of the refrigerant vapor compression system
upstream, with respect to refrigerant flow, of the expansion
device, and the lower zone connected by a second refrigerant line
in fluid communication with the closed-loop refrigerant circuit at
a location on a low-pressure side of the refrigerant vapor
compression system downstream, with respect to refrigerant flow, of
the expansion device. A first flow control device interdisposed in
the first refrigerant line and a second flow control device
interdisposed in the second refrigerant line. Each of the flow
control devices has an open position and a closed position. In an
embodiment, each of the flow control devices may be a solenoid
valve having an open position and a closed position. The
refrigerant vapor compression system may further include a
controller operatively associated with each of the first and second
flow control devices for selectively positioning one of the first
and second flow control devices in an open position and
simultaneously selectively positioning the other of the first and
second flow control devices in a closed position.
[0009] In an aspect of the invention, a method is provided for
managing refrigerant charge in a refrigerant vapor compression
system operating in a transcritical cycle, the refrigerant vapor
compression system having a refrigerant compression device, a
refrigerant heat rejection heat exchanger and a refrigerant heat
absorption heat exchanger disposed in serial refrigerant flow
communication in a closed-loop refrigerant circuit, with an
expansion device disposed in the closed-loop refrigerant circuit
downstream of the refrigerant heat rejection heat exchanger and
upstream of the refrigerant heat absorption heat exchanger. The
method includes the steps of: selectively withdrawing refrigerant
from the closed-loop refrigerant circuit of the refrigerant vapor
compression system; storing the withdrawn refrigerant; and
returning the withdrawn refrigerant from storage to the closed-loop
refrigerant circuit of the refrigerant vapor compression
system.
[0010] If the refrigerant storage device is connected to the
closed-loop refrigerant cycle at location on a high-pressure side,
then the refrigerant is typically withdrawn from the closed-loop
refrigerant cycle during operation of the refrigerant vapor
compression system and returned to the closed-loop refrigerant
cycle during an off-cycle of the refrigerant vapor compression
system. In this embodiment of the method, refrigerant is withdrawn
from the closed-loop refrigerant circuit at a location on a
high-pressure side upstream of the expansion device and the
withdrawn refrigerant is also returned to the closed-loop
refrigerant circuit at a location upstream of the expansion
device.
[0011] If the refrigerant storage device is connected to the
closed-loop refrigerant cycle at location on a low-pressure side,
then the refrigerant is typically withdrawn from the closed-loop
refrigerant cycle during an off-cycle of the refrigerant vapor
compression system and returned to the closed-loop refrigerant
cycle during operation of the refrigerant vapor compression system.
In this embodiment of the method, refrigerant is withdrawn from the
closed-loop refrigerant circuit at a location on a low-pressure
side downstream of the expansion device and the withdrawn
refrigerant is also returned to the closed-loop refrigerant circuit
at a location downstream of the expansion device.
[0012] If the refrigerant storage device is connected to the
closed-loop refrigerant cycle at two locations, one on a
high-pressure side and the other on a low-pressure side, then the
refrigerant is typically withdrawn from the closed-loop refrigerant
cycle during operation of the refrigerant vapor compression system
and returned to the closed-loop refrigerant cycle also during
operation of the refrigerant vapor compression system. In this
embodiment of the method, refrigerant is withdrawn from the
closed-loop refrigerant circuit at a location on a high-pressure
side upstream of the expansion device and the withdrawn refrigerant
is returned to the closed-loop refrigerant circuit at a location on
a low-pressure side downstream of the expansion device.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] For a further understanding of the invention, reference will
be made to the following detailed description of the invention
which is to be read in connection with the accompanying drawing,
where:
[0014] FIG. 1 is a schematic diagram illustrating a first exemplary
embodiment of a refrigerant vapor compression system in accord with
the invention;
[0015] FIG. 2 is a schematic diagram illustrating a second
exemplary embodiment of a refrigerant vapor compression system in
accord with the invention; and
[0016] FIG. 3 is a schematic diagram illustrating a third exemplary
embodiment of a refrigerant vapor compression system in accord with
the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0017] Referring now to FIGS. 1-3, the refrigerant vapor
compression system 10 includes a compression device 20, a
refrigerant heat rejection heat exchanger 40, a refrigerant heat
absorption heat exchanger 50, also referred to herein as an
evaporator, connected in a closed-loop refrigerant circuit in
series refrigerant flow arrangement by various refrigerant lines 2,
4 and 6. Additionally, an expansion device 55, operatively
associated with the evaporator 50, is interdisposed in refrigerant
line 4 downstream, with respect to refrigerant flow, of the
refrigerant heat rejection heat exchanger 40 and upstream, with
respect to refrigerant flow, of the refrigerant heat absorption
heat exchanger 50. In the embodiments of the refrigerant vapor
compression system 10 depicted in FIGS. 1-3, the expansion device
55 comprises an electronic expansion valve. However, it is to be
understood that the expansion device may instead comprise a
thermostatic expansion valve, or a fixed orifice device, such as a
capillary tube.
[0018] When the refrigerant vapor compression system 10 is
operating in a transcritical cycle, such as for instance when
charged with carbon dioxide refrigerant and operating at a
compressor discharge pressure in excess of the critical pressure
point of carbon dioxide, the refrigerant heat rejection heat
exchanger 40 operates at supercritical pressure and functions as a
refrigerant gas cooler, but does not operate to condense the carbon
dioxide refrigerant vapor. The tube bank 42 of the heat rejection
heat exchanger 40 may comprise, for example, a plate fin and round
tube bank, such as a tube bank of a conventional round tube and
plate fin heat exchanger or a corrugated fin and multi-channel flat
tube bank of a minichannel or microchannel heat exchanger. In
traversing the refrigerant heat rejection heat exchanger 40, the
refrigerant passes through the heat exchanger tubes of the tube
bank 42 in heat exchange relationship with a secondary fluid,
typically ambient air, generally outdoor air, being drawn through
the tube bank 42 by an air mover 44, such as one or more fans,
operatively associated with the tube bank 42 of the heat rejection
heat exchanger 40.
[0019] Whether the refrigerant vapor compression system 10 is
operating in a subcritical cycle or a transcritical cycle, the
refrigerant heat absorption heat exchanger 50, being located in the
refrigerant circuit downstream, with respect to refrigerant flow,
of the expansion device 55, always operates at a subcritical
pressure and functions as an evaporator. In traversing the heat
absorption heat exchanger 50, the refrigerant passes through the
heat exchanger tubes of the tube bank 52 in heat exchange
relationship with air to be conditioned, typically air at least
partially drawn from and to be returned to a climate-controlled
environment, being drawn through the tube bank 52 by an air mover
54, such as one or more fans, operatively associated with the tube
bank 52 of the heat absorption heat exchanger 50, whereby the air
is cooled and the refrigerant is evaporated and typically
superheated. The tube bank 52 of the refrigerant heat absorption
heat exchanger 50 may comprise, for example, a finned tube heat
exchanger, such as for example a plate fin and round tube bank of a
conventional round tube and plate fin heat exchanger, or a
corrugated fin and multi-channel flat of a minichannel or
microchannel heat exchanger.
[0020] The compression device 20 functions to compress and
circulate refrigerant through the refrigerant circuit as will be
discussed in further detail hereinafter. The compression device 20
may be a single, single-stage compressor as depicted, such as for
example a scroll compressor, a reciprocating compressor, a rotary
compressor, a screw compressor, or a centrifugal compressor.
However, it is to be understood that the compression device 20 may
also be a multiple-stage compression device having at least a lower
pressure compression stage and a higher pressure compression stage
with refrigerant flow passing from the lower pressure compression
stage to the higher pressure compression stage. In such an
embodiment, the multiple-stage compression device may comprise a
single, multi-stage compressor, such as, for example, a scroll
compressor, or a screw compressor having staged compression
pockets, or a reciprocating compressor having at least a first bank
of cylinders and a second bank of cylinders, or a pair of
single-stage compressors connected in series refrigerant flow
relationship with the discharge outlet of the upstream compressor
connected in serial refrigerant flow communication with the suction
inlet of the downstream compressor. The compression device 20 may
also comprise two or more compressors operating in a parallel or
tandem configuration.
[0021] The refrigerant vapor compression system 10 further includes
a refrigerant storage device 60, also referred to as a receiver,
defining a volume wherein a variable refrigerant charge may be
stored. The receiver 60 is in fluid flow communication with the
closed-loop refrigerant circuit of the refrigerant vapor
compression system 10 through at least one refrigerant line. The
refrigerant vapor compression system 10 further includes a
controller 100 operatively associated with a refrigerant flow
control device interdisposed in the at least one refrigerant line
connecting the receiver 60 in fluid flow communication with the
closed-loop refrigerant circuit of the refrigerant vapor
compression system 10. Refrigerant flow through the at least one
refrigerant line is controlled by the selective opening and closing
of the refrigerant flow control device interdisposed therein.
[0022] Referring now to FIG. 1, in the embodiment depicted therein,
the receiver 60 defines a volume having a lower zone 63 wherein
liquid refrigerant may be collected and an upper zone 67 wherein
refrigerant vapor may reside. It is to be understood that, at
certain environmental and operating conditions, the entire internal
volume of the receiver 60 may be filled with the refrigerant vapor.
The upper zone 67 is in refrigerant flow communication through a
refrigerant line 12 with the refrigerant line 4 on the
high-pressure side of the refrigerant vapor compression system 10,
that is at a location downstream, with respect to refrigerant flow,
of the refrigerant heat rejection heat exchanger 40, and upstream,
with respect to refrigerant flow, of the refrigerant expansion
device 55. The lower zone 63 is in refrigerant flow communication
through a refrigerant line 14 with the refrigerant line 4 on the
low-pressure side of the refrigerant vapor compression system 10,
that is at a location downstream, with respect to refrigerant flow,
of the refrigerant expansion device 55, and upstream, with respect
to refrigerant flow, of the refrigerant heat absorption heat
exchanger 50. Additionally, a refrigerant flow control device 65
having an open position and a closed position is interdisposed in
refrigerant line 12 and a refrigerant flow control device 75 having
an open position and a closed position is interdisposed in
refrigerant line 14. It is to be understood that any other
locations on a high-pressure side and low-pressure side with the
refrigerant vapor compression system 10 may be selected to provide
refrigerant flow communication with the receiver 60.
[0023] In this embodiment, the controller 100 is operatively
associated with each of the respective refrigerant flow control
devices 65 and 75 interdisposed in refrigerant lines 12 and 14,
respectively, to selectively position each of the respective
refrigerant flow control devices in an open or a closed position.
The controller 100 adjusts the amount of the refrigerant charge
circulating through the closed-loop refrigerant circuit, defined by
the refrigerant lines 2, 4 and 6, as necessary to maintain at
desired refrigerant discharge pressure from the compression device
20 for a particular operating point, by selectively positioning the
flow control devices 65 and 75 between their respective open and
closed positions either to pass refrigerant from the closed-loop
refrigerant circuit into the receiver 60, thereby reducing the
amount of the refrigerant charge circulating through the
closed-loop refrigerant circuit, or pass refrigerant from the
receiver 60 into the closed-loop refrigerant circuit, thereby
increasing the amount of the refrigerant charge circulating through
the closed-loop refrigerant circuit. Thus, addition of refrigerant
into the closed-loop refrigerant circuit occurs on the low-pressure
side of the refrigerant vapor compression system 10, but removal of
refrigerant from the closed-loop refrigerant circuit occurs on the
high-pressure side of the refrigerant vapor compression system
10.
[0024] To remove refrigerant from the closed-loop refrigerant
circuit of the refrigerant vapor compression system 10, typically
during operation, the controller 100 positions the refrigerant flow
control device 65 in its open position and positions the
refrigerant flow control device 75 in its closed position. With the
refrigerant flow control devices 65 and 75 so positioned, high
pressure refrigerant vapor flows from the refrigerant line 4
through the refrigerant line 12 into the upper zone 67 of the
storage chamber of the receiver 60, but can not flow out of the
receiver 60 through the refrigerant line 14 because the refrigerant
flow control device 75 is in its closed position.
[0025] To add refrigerant to the closed-loop refrigerant circuit of
the refrigerant vapor compression system 10, which can be done
during operation or during an off-cycle, the controller 100
positions the refrigerant flow control device 65 in its closed
position and positions the refrigerant flow control device 75 in
its open position. With the refrigerant flow control devices 65 and
75 so positioned, refrigerant flows from the lower zone 63 of the
storage chamber of the receiver 60 through the refrigerant line 14
into the refrigerant line 4, but high pressure refrigerant vapor
can not enter the receiver 60 because the refrigerant flow control
device 65 is in its closed position, thereby blocking the flow of
high-pressure refrigerant vapor through the refrigerant line 12. It
is to be understood that during off-cycle at certain environmental
conditions, the refrigerant may be added to or removed from the
close-loop refrigerant circuit of the refrigerant vapor compression
system 10 though the refrigerant flow control devices 65 and
75.
[0026] The storage chamber of the receiver 60 will have an
equilibrium pressure that varies with the amount of refrigerant
stored therein, but, during operation of the refrigerant vapor
compression system 10, is always less than the high-pressure side
refrigerant pressure in the refrigerant line 4 upstream of the
evaporator expansion device 55 and greater than the low-pressure
side refrigerant pressure in the refrigerant line 4 downstream of
the evaporator expansion device 55. During operation of the
refrigerant vapor compression 10, removal of refrigerant from the
closed-loop refrigerant circuit into the receiver 60 may be carried
out by simply opening the refrigerant flow control device 65 for a
period of time so that refrigerant vapor will flow through the
refrigerant line 12 due to the pressure differential between the
refrigerant pressure at the location at which the refrigerant line
12 taps into the refrigerant line 4 upstream of the evaporator
expansion device 55 and the equilibrium pressure within the storage
chamber of the receiver 60. During operation of the refrigerant
vapor compression 10, addition of refrigerant into the closed-loop
refrigerant circuit from the receiver 60 may be carried out by
simply opening the refrigerant flow control device 75 so that
refrigerant will flow through the refrigerant line 14 due to the
pressure differential between the equilibrium pressure within the
storage chamber of the receiver 60 and the refrigerant pressure at
the location at which the refrigerant line 14 taps into the
refrigerant line 4 downstream of the evaporator expansion device
55.
[0027] It is to be understood that such refrigerant charge
management is particularly important for transcritical operation of
the refrigerant vapor compression system 10, since temperature and
pressure of the refrigerant are independent from each other, and
high-side optimum pressure would be different at each environmental
conditions.
[0028] Referring now to FIG. 2, in the exemplary embodiment of the
refrigerant vapor compression system 10 depicted therein, the
receiver 60, rather being connected in refrigerant flow
communication with both the high-pressure side and the low-pressure
side of the refrigerant vapor compression system 10, is connected
in refrigerant flow communication with the closed-loop refrigerant
circuit on the high-pressure side only through a single refrigerant
line 16 tapping into the refrigerant line 4 at location downstream
of the refrigerant heat rejection heat exchanger 40 and upstream of
the evaporator expansion valve 55. A refrigerant flow control
device 85 having an open position and a closed position is
interdisposed in the refrigerant line 16. The controller 100 is
operatively associated with the refrigerant flow control device 85
to selectively position the refrigerant flow control device 85 in
an open or a closed position.
[0029] In this embodiment, the controller 100 adjusts the amount of
the refrigerant charge circulating through the closed-loop
refrigerant circuit, defined by the refrigerant lines 2, 4 and 6,
as necessary to maintain at desired refrigerant discharge pressure
from the compression device 20 for a particular operating point, by
selectively positioning the refrigerant flow control device 85 in
its open position either to pass vapor refrigerant from the
closed-loop refrigerant circuit into the receiver 60 or to pass
refrigerant vapor from the receiver 60 back into the closed-loop
refrigerant circuit, and in its closed position to block
refrigerant flow through the refrigerant line 16. During operation
of the system 10, when the controller 100 determines that the
refrigerant charge is excessive for the current operating
conditions, the controller 100 opens the refrigerant flow control
device 85 to allow refrigerant vapor to flow into the receiver 60.
Once the refrigerant charge has been reduced as desired, the
controller 100 closes the refrigerant flow control device 85,
thereby trapping high pressure refrigerant vapor within the
receiver 60. When the system 10 is in an off-cycle, the controller
100 can return refrigerant vapor to the closed-loop refrigerant
circuit to increase the system refrigerant charge by simply opening
the refrigerant flow control device 85 to allow high pressure
refrigerant vapor to escape the receiver 60 through the refrigerant
line 16 into the refrigerant line 4 of the refrigerant circuit.
When the controller 100 determines the system refrigerant charge is
sufficient, the controller again closes the refrigerant flow
control device 85 thereby blocking refrigerant vapor from flowing
into the receiver 60 when the refrigerant vapor compression system
10 returns to operation. As previously noted, the tapping location
for the refrigerant line 16 could be anywhere on the high-pressure
side of the refrigerant vapor compression system 10.
[0030] Referring now to FIG. 3, in the exemplary embodiment of the
refrigerant vapor compression system 10 depicted therein, the
receiver 60, rather being connected in refrigerant flow
communication with both the high-pressure side and the low-pressure
side of the refrigerant vapor compression system 10, is connected
in refrigerant flow communication with the closed-loop refrigerant
circuit on the low-pressure side only through a single refrigerant
line 18 tapping into the refrigerant line 4 at location downstream
of the evaporator expansion valve 55 and upstream of the
refrigerant heat absorption heat exchanger 50. A refrigerant flow
control device 95 having an open position and a closed position is
interdisposed in the refrigerant line 18. The controller 100 is
operatively associated with the refrigerant flow control device 95
to selectively position the refrigerant flow control device 95 in
an open or a closed position.
[0031] In this embodiment, the controller 100 adjusts the amount of
the refrigerant charge circulating through the closed-loop
refrigerant circuit, defined by the refrigerant lines 2, 4 and 6,
as necessary to maintain at desired refrigerant discharge pressure
from the compression device 20 for a particular operating point, by
selectively positioning the refrigerant flow control device 95 in
its open position to pass liquid refrigerant either from the
closed-loop refrigerant circuit into the receiver 60 or to pass
liquid refrigerant from the receiver 60 back into the closed-loop
refrigerant circuit and in its closed position to block refrigerant
flow through the refrigerant lie 18. When the controller 100
determines that the refrigerant charge is excessive for the current
operating conditions, the controller 100 shuts down the refrigerant
vapor compression system 10 and, during an off-cycle of the
refrigerant vapor compression system 10, opens the refrigerant flow
control device 95 to allow refrigerant to flow through the
refrigerant line 18 into the receiver 60. Once the refrigerant
charge has been reduced as desired, the controller 100 closes the
refrigerant flow control device 95, thereby trapping refrigerant
vapor within the receiver 60, and the refrigerant vapor compression
system 10 resumes its operation. During operation of the
refrigerant vapor compression system 10, the controller 100 can
return refrigerant to the closed-loop refrigerant circuit to
increase the system refrigerant charge by simply opening the
refrigerant flow control device 95 to allow refrigerant vapor to
escape the receiver 60 through the refrigerant line 18 into the
refrigerant line 4 of the closed-loop refrigerant circuit. When the
controller 100 determines the system refrigerant charge is
sufficient, the controller again closes the refrigerant flow
control device 95 thereby blocking refrigerant from flowing from
the receiver 60. Again, the tapping location for the refrigerant
line 18 could be anywhere on the low-pressure side of the
refrigerant vapor compression system 10.
[0032] The refrigerant flow control devices 65, 75, 85 and 95 may
comprise any flow control device that is selectively positionable
in at least a first open position whereat refrigerant may flow
through the refrigerant line in which the flow control device is
disposed and a second closed position whereat refrigerant flow is
blocked through the refrigerant line in which the flow control
device is disposed. For example, each of the flow control devices
65, 75, 85 and 95 may comprise a two-position solenoid valve. In an
embodiment, to allow for more precise control of the refrigerant
amount in the refrigerant storage device 60 the flow lines 12
and/or 14 may for example be equipped with an additional orifice or
a capillary tube. The orifice or capillary tube would slow down the
migration process of the refrigerant in and/or out of the of the
refrigerant storage device 60, thus allowing for more precise
control of the amount of the refrigerant in the refrigerant storage
device. The orifice can be a part of the valve construction or a
stand-alone refrigerant flow control device.
[0033] The refrigerant vapor compression system 10 can also
include, among other features and options, economized cycle with
provisions for vapor injection into the compressor 20. The
refrigerant vapor compression system 10 can also include provisions
for liquid injection to provide cooling to the compression process
within the compressor 20. It is to be understood that the secondary
fluid moving devices 44 and 54 may also comprise pumps circulating
liquids such as water or glycol solutions in heat exchange
relationship with the refrigerant circulating through the
closed-loop refrigerant circuit of the refrigerant vapor
compression system 10.
[0034] The foregoing description is only exemplary of the teachings
of the invention. Those of ordinary skill in the art will recognize
that various modifications and variations may be made to the
invention as specifically described herein and equivalents thereof
without departing from the spirit and scope of the invention as
defined by the following claims.
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