U.S. patent application number 11/436342 was filed with the patent office on 2007-11-22 for automatic refill system for an air conditioning system.
Invention is credited to Charles E. Goodremote, Jianmin Yin.
Application Number | 20070266717 11/436342 |
Document ID | / |
Family ID | 38710728 |
Filed Date | 2007-11-22 |
United States Patent
Application |
20070266717 |
Kind Code |
A1 |
Goodremote; Charles E. ; et
al. |
November 22, 2007 |
Automatic refill system for an air conditioning system
Abstract
An automatic recharge system (22) is provided for a
transcritical cooling system (10). The recharge system (22)
includes a refrigerant container (30) capable of storing a
refrigerant charge at a higher pressure that can be accommodated on
the low pressure side of the cooling system (10), and a control
valve (34) connected between an outlet (36) of the container (30)
and the low pressure side of the cooling system (10) to
automatically control the release of refrigerant form the
refrigerant container (30) for circulation in the cooling system
(10).
Inventors: |
Goodremote; Charles E.;
(Racine, WI) ; Yin; Jianmin; (Racine, WI) |
Correspondence
Address: |
MICHAEL BEST & FRIEDRICH LLP
100 E WISCONSIN AVENUE, Suite 3300
MILWAUKEE
WI
53202
US
|
Family ID: |
38710728 |
Appl. No.: |
11/436342 |
Filed: |
May 18, 2006 |
Current U.S.
Class: |
62/149 ;
62/77 |
Current CPC
Class: |
F25B 2309/061 20130101;
B60H 1/00978 20130101; F25B 45/00 20130101; F25B 2345/001 20130101;
B60H 1/00585 20130101; F25B 9/008 20130101 |
Class at
Publication: |
62/149 ;
62/77 |
International
Class: |
F25B 45/00 20060101
F25B045/00 |
Claims
1. A transcritical cooling system comprising: a compressor to
provide pressurized refrigerant to the system; a gas cooler
connected downstream from the compressor to receive pressurized
refrigerant therefrom and to supply cooled, pressurized refrigerant
to the system; an expansion device connected downstream from the
gas cooler to receive cooled, pressurized refrigerant therefrom and
to supply reduced pressure, two-phase refrigerant to the system; an
evaporator connected downstream from the expansion device to
receive reduced pressure, two-phase refrigerant therefrom and
connected upstream from the compressor to supply heated, reduced
pressure refrigerant thereto; and an automatic refrigerant recharge
system connected to the cooling system downstream from the
evaporator and upstream from the compressor to automatically supply
additional refrigerant for circulation through the system; the
refrigerant recharge system comprising a refrigerant container for
storing a charge of refrigerant at a pressure greater than a
pressure of the refrigerant exiting the evaporator, and a control
valve connected between the container and the remainder of the
system to control the release of refrigerant from the refrigerant
container for circulation in the cooling system.
2. The system of claim 1 further comprising an accumulator
connected downstream from the evaporator to receive heated
refrigerant therefrom and upstream from the compressor to supply
gas phase refrigerant thereto; and wherein the control valve is
connected to the accumulator to supply refrigerant thereto from the
refrigerant container.
3. The system of claim 2 wherein the refrigerant recharge system is
carried by the accumulator.
4. The system of claim 1 further comprising a low pressure conduit
connected between the evaporator and the compressor to transfer
refrigerant from the evaporator to the compressor; and wherein the
refrigerant container is a cylindrical tube extending along an
exterior of the low pressure conduit.
5. The system of claim 1 wherein the control valve comprises a
bleed valve having a preselected bleed rate into the cooling system
based on anticipated refrigerant leakage from the system.
6. The system of claim 1 wherein the control valve comprises a
normally off valve that is responsive to a signal from the cooling
system to temporarily open and supply a discrete amount of
refrigerant to the cooling system.
7. The system of claim 6 further comprising a plurality of sensors
to monitor system parameters, and a control connected to the
sensors and the control valve to provide the signal to the control
valve in response to information from the sensors.
8. The system of claim 1 wherein the compressor is a variable
displacement compressor.
9. A method of automatically recharging a transcritical cooling
system that has leaked refrigerant, the cooling system comprising a
compressor, a gas cooler, an expansion device, an evaporator and an
accumulator volume all connected in series in a refrigerant loop,
the method comprising the steps of: a) storing a refrigerant in a
recharge volume that is hydraulically isolated from the accumulator
volume and at a pressure that is greater than the refrigerant
pressure in the accumulator volume, the recharge volume being part
of the cooling system during normal operation of the cooling
system; and b) automatically releasing refrigerant from the
recharge volume into the system to replace refrigerant that has
leaked from the system.
10. The method of claim 9 wherein step b) comprises continuously
bleeding refrigerant into the cooling system from the recharge
volume during normal operation of the cooling system.
11. The method of claim 9 further comprising the step of
automatically monitoring the cooling system to determine if
refrigerant should be released from the recharge volume into the
cooling system; and wherein step b) further comprises releasing the
refrigerant into the cooling system in response to the step of
automatically monitoring.
12. The method of claim 9 wherein the step of monitoring comprises
monitoring a suction line pressure of the cooling system,
monitoring an ambient temperature, and monitoring a displacement of
the compressor.
13. The method of claim 9 further comprising the step of
periodically replacing the recharge volume after the refrigerant
has been depleted therefrom.
14. A method of automatically recharging a transcritical cooling
system that has leaked refrigerant, the cooling system comprising a
compressor, a gas cooler, an expansion device, and an evaporator
all connected in series in a refrigerant loop, the method
comprising the steps of: a) storing a refrigerant in a recharge
volume at a pressure that is greater than the refrigerant pressure
in a suction side of the refrigerant loop, the recharge volume
being part of the cooling system during normal operation of the
cooling system; and b) automatically releasing refrigerant from the
recharge volume into the system to replace refrigerant that has
leaked from the system.
15. The method of claim 14 wherein step b) comprises continuously
bleeding refrigerant into the cooling system from the recharge
volume during normal operation of the cooling system.
16. The method of claim 14 further comprising the step of
automatically monitoring the cooling system to determine if
refrigerant should be released from the recharge volume into the
system; and wherein step b) further comprises releasing the
refrigerant into the cooling system in response to the step of
automatically monitoring.
17. The method of claim 14 wherein the step of monitoring comprises
monitoring a suction line pressure of the cooling system,
monitoring an ambient temperature, and monitoring a displacement of
the compressor.
18. The method of claim 14 further comprising the step of
periodically replacing the recharge volume after the refrigerant
has been depleted therefrom.
Description
FIELD OF THE INVENTION
[0001] This invention relates to air conditioning systems, and in
more particular applications, to transcritical air conditioning
systems that utilize refrigerant, such as CO.sub.2.
BACKGROUND OF THE INVENTION
[0002] In cooling systems such as vapor compression type air
conditioning systems, refrigerant leakage can take place over time,
thereby reducing system performance and increasing the chance of
damage to the compressor. While refrigerant leakage can take place
in any cooling system and cause a loss of performance, such leakage
can be particularly troublesome in transcritical cooling systems
that utilize a variable displacement compressor. In such systems,
if the refrigerant charge amount falls below a certain level due to
leakage, the system will not be able to function normally and will
experience a suction pressure that is below the normal operating
limit, too much superheat from the evaporator, and a reduced
displacement in the variable displacement compressor. As a result,
the system will have a very small cooling capacity. In this regard,
in systems that utilize an accumulator, it is known to provide
extra volume in the accumulator in order to accommodate more
refrigerant than is required to operate the system satisfactorily
so that, as refrigerant leaks form the system, the additional
refrigerant that is contained in the accumulator is circulated in
the system to make up the lost refrigerant. While such systems may
work satisfactorily for their intended purpose, they tend to
increase the system size and weight because of the required
increase in the size of the accumulator to accommodate the extra
refrigerant.
SUMMARY OF THE INVENTION
[0003] In accordance with one feature of the invention, a
transcritical cooling system is provided and includes a compressor
to provide pressurized refrigerant to the system; a gas cooler
connected downstream from the compressor to receive pressurized
refrigerant therefrom and to supply cooled, pressurized refrigerant
to the system; an expansion device connected downstream from the
gas cooler to receive cooled, pressurized refrigerant therefrom and
to supply reduced pressure, two-phase refrigerant to the system; an
evaporator connected downstream from the expansion device to
receive reduced pressure, two-phase refrigerant therefrom and
connected upstream from the compressor to supply heated, reduced
pressure refrigerant thereto; and an automatic refrigerant recharge
system connected to the cooling system downstream from the
evaporator and upstream from the compressor to automatically supply
additional refrigerant for circulation through the system. The
refrigerant recharge system includes a refrigerant container for
storing a charge of refrigerant at a pressure greater than a
pressure of the refrigerant exiting the evaporator, and a control
valve connected between the container and the remainder of the
system to control the release of refrigerant from the refrigerant
container for circulation in the cooling system.
[0004] In one feature, the cooling system further includes an
accumulator connected downstream from the evaporator to receive
heated refrigerant therefrom and upstream from the compressor to
supply gas phase refrigerant thereto. The control valve is
connected to the accumulator to supply refrigerant thereto from the
refrigerant container. In a further feature, the refrigerant
recharge system is carried by the accumulator.
[0005] As one feature, the cooling system further includes a low
pressure conduit connected between the evaporator and the
compressor to transfer refrigerant from the evaporator to the
compressor, and the refrigerant container is provided as a
cylindrical tube extending along an exterior of the low pressure
conduit.
[0006] According to one feature, the control valve includes a bleed
valve having a preselected bleed rate into the cooling system based
on anticipated refrigerant leakage from the cooling system.
[0007] In accordance with one feature, the control valve includes a
normally off valve that is responsive to a signal from the system
to temporarily open and supply a discrete amount of refrigerant to
the cooling system. As a further feature, the cooling system
further includes a plurality of sensors to monitor system
parameters, and a control connected to the sensors and the control
valve to provide the signal to the control valve in response to
information from the sensors.
[0008] As one feature, the compressor is a variable displacement
compressor.
[0009] In accordance with one feature of the invention, a method is
provided for automatically recharging a transcritical cooling
system that has leaked refrigerant, wherein the cooling system
includes a compressor, a gas cooler, an expansion device, an
evaporator and an accumulator volume all connected in series in a
refrigerant loop. The method including the steps of:
[0010] a) storing a refrigerant in a recharge volume that is
hydraulically isolated from the accumulator volume and at a
pressure that is greater than the refrigerant pressure in the
accumulator volume, the recharge volume being part of the cooling
system during normal operation of the cooling system; and
[0011] b) automatically releasing refrigerant from the recharge
volume into the system to replace refrigerant that has leaked from
the cooling system.
[0012] As one feature, step b) includes continuously bleeding
refrigerant into the cooling system from the recharge volume during
normal operation of the cooling system.
[0013] In one feature, the method further includes the step of
automatically monitoring the cooling system to determine if
refrigerant should be released from the recharge volume into the
cooling system, and step b) further includes releasing the
refrigerant into the cooling system in response to the step of
automatically monitoring. As a further feature, the step of
automatically monitoring includes monitoring a suction line
pressure of the cooling system, monitoring an ambient temperature,
and monitoring a displacement of the compressor.
[0014] According to one feature, the method further includes the
step of periodically replacing the recharge volume after the
refrigerant has been depleted therefrom.
[0015] In accordance with one feature of the invention, a method is
provided for automatically recharging a transcritical cooling
system that has leaked refrigerant. The cooling system comprising a
compressor, a gas cooler, an expansion device, and an evaporator
all connected in series in a refrigerant loop. The method
comprising the steps of:
[0016] a) storing a refrigerant in a recharge volume at a pressure
that is greater than the refrigerant pressure in a suction side of
the refrigerant loop, the recharge volume being part of the cooling
system during normal operation of the cooling system; and
[0017] b) automatically releasing refrigerant from the recharge
volume into the system to replace refrigerant that has leaked from
the system.
[0018] Other objects, features, and advantages of the invention
will become apparent from a review of the entire specification,
including the appended claims and drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is a diagrammatic representation of an automotive air
conditioning system including an automatic recharge system
embodying the present invention;
[0020] FIG. 2 is a diagrammatic representation similar to FIG. 1,
but showing an alternate embodiment of the automatic refill system;
and
[0021] FIG. 3 is a graph of ambient temperature versus pressure
inside a refrigerant charge cylinder showing the plots for the
different volumes required to accommodate a 120 gram extra charge
of CO.sub.2 refrigerant.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0022] With reference to FIG. 1, a transcritical cooling system 10
is shown and includes a refrigerant flow path or loop 12; a
variable displacement compressor 14 to deliver pressurized
refrigerant (typically carbon dioxide ("CO.sub.2")) to the flow
path 12; a gas cooler 16 connected to the compressor 14 to receive
the pressurized refrigerant therefrom; an expansion device 18
connected in the refrigerant flow path 12 downstream from the gas
cooler 16 to receive cooled, pressurized refrigerant therefrom and
to supply reduced pressure, liquid phase refrigerant to the flow
path 12, often in the form of a two-phase refrigerant flow that
includes the liquid phase refrigerant; an evaporator 20 connected
to the expansion device 18 to receive reduced pressure, liquid
phase refrigerant therefrom and deliver heated refrigerant back to
the system 10; and an automatic refill or recharge system 22
connected to the low pressure side of the refrigerant flow path 12
between the evaporator 20 and the compressor 14 to automatically
deliver refrigerant to the system 10 during normal operation of the
system 10 as required by the leakage of refrigerant from the system
10. While not absolutely required, it is highly preferred that the
system 10 further include an accumulator 24 connected downstream
from the evaporator 20 to receive heated refrigerant therefrom and
upstream from the compressor 14 to deliver gas phase refrigerant
thereto. The accumulator 24 encloses an accumulator volume 25 for
storing refrigerant and for separating liquid phase and gas phase
refrigerant so as to supply gas phase refrigerant to the compressor
14. Again, while not absolutely required, it is also highly
preferred that the system 10 further include a suction line heat
exchanger, shown at 26, to transfer heat from the refrigerant in
the high pressure side of the refrigerant flow path 12 to the
refrigerant in the low pressure side of the refrigerant flow path
12. In this regard, the suction line heat exchanger 26 can either
be integrated into the accumulator 24 as shown, or can be a
separate heat exchanger, as is known.
[0023] The automatic refill system 22 will preferably include a
refrigerant container 30, preferably in the form of a cylindrical
housing 32, and a control valve 34 connected between an outlet 36
of the container 30 and the low pressure side of the refrigerant
flow path 12 to control the flow of refrigerant from the container
30 into the remainder of the system 10. The container 30 encloses a
recharge volume 38 that stores a mass of refrigerant for recharging
the system 10, and preferably stores an adequate mass of
refrigerant to recharge the system 10 over a number of years of
operation.
[0024] In one of the most simple embodiments of the recharge system
22, the control valve 34 is provided in the form of a bleed valve
having a bleed rate that would be set to allow a certain number of
grams of refrigerant per year to bleed into the system in order to
automatically compensate for the anticipated system leakage. For
example, in one embodiment of the system 10, it would be
anticipated that a bleed rate through the valve 34 should be about
20 grams of CO.sub.2 refrigerant per year in order to automatically
compensate for system leakage.
[0025] In another embodiment of the recharge system 22, the control
valve 34 is provided in the form of a normally off valve, such as a
solenoid valve, that is responsive to a signal from the system 10
to temporarily open and supply a discrete amount of refrigerant to
the system 10. In this regard, sensors 42, 44 and 46 are preferably
provided to monitor the suction pressure, compressor displacement,
and ambient temperature during operation of the system 10 and to
provide a signal to a controller 48. If the suction pressure goes
below a predetermined level P.sub.L for a certain period of time
t.sub.P (for example, five minutes after the system 10 is turned
on) at moderate to high ambient temperature conditions (for
example, ambient temperatures above 30.degree. C.) while the
compressor 14 is in partial displacement, the controller 48 would
command the control valve 34 to open for a very short period of
time (for example, one half of a second) to thereby supply a
discrete amount of refrigerant to the system 10 in order to
complete one automatic charge. After this, the system 10 will
continue monitoring for the time period t.sub.P and if the suction
pressure is still below P.sub.L, the system will repeat the
process. Otherwise, the recharge system 22 will be in waiting mode
where the system 22 monitors the parameters from the sensors 42, 44
and 46 in order to determine if another automatic charge is
required. At low ambient temperature conditions, the system 22
would stay in the waiting mode with the valve 34 closed.
[0026] The recharge system 22 is integrated as part of the cooling
system 10 so that it can function during normal operation of the
cooling system 10. In this regard, the refrigerant container 30 and
valve 34 of the recharge system 22 can be mounted on or carried by
the accumulator 24. However, it should be appreciated that there
are many possibilities for integrating the recharge system 22 into
the cooling system 10. For example, with reference to FIG. 4, an
alternate embodiment of the system 10 is shown wherein the
container 30 is provided in the form of a cylindrical tube 50,
preferably of a small diameter (such as for example as small as 20
mm in diameter), that extends along a low pressure conduit 52
connected between the evaporator 20 and the compressor 14. In this
regard, while the container 30 and conduit 52 are shown upstream of
the accumulator 24, they could also be provided downstream of the
accumulator 24.
[0027] It should be appreciated that all of the above described
components for the system 10, including the components of the
recharge system 22, have been described generically because there
are many suitable forms for each of the components of the system 10
and the particular configuration selected will be highly dependent
upon the requirements for each particular application, as can be
determined by one skilled in the art. It should also be appreciated
that by providing the control valve 34, the recharge system 22 can
automatically provide refrigerant to the cooling system 10 while
the transcritical cooling system is operating to make up for
refrigerant loss due to leakage without requiring any human
intervention.
[0028] While not shown, a quick disconnect, or other suitable fluid
connection can be provided, preferably between the container 30 and
the valve 34, to allow for the container 30 to be manually replaced
when it has been depleted of its refrigerant charge, preferably
after a number of years of operation of the cooling system 10.
[0029] FIG. 3 is a plot showing the differences in charge storage
capacity based on the ambient temperature surrounding the system 10
and the pressure capacity of the container for the refrigerant. The
plot assumes a 120 gram charge of extra refrigerant that can be
used to compensate for refrigerant leakage over a five year period.
Each line in the plot represents a different storage volume
available for the 120 gram charge of refrigerant. It can be seen
from the chart that the greater the pressure capability of the
refrigerant container, the smaller the required volume for the
refrigerant charge. For example, if the refrigerant container has a
pressure limit of 110 Bar at 80.degree. C. (as may be somewhat
typical for an accumulator), a volume of 460 cm.sup.2 is required
to accommodate the 120 gram charge of refrigerant, but if the
pressure limit of the storage volume is increased to 200 bar, the
volume of the refrigerant container can be reduced to 200 cm.sup.2.
Thus, by providing a separate container 30 for the charge of
refrigerant, the system 22 can store the refrigerant at a higher
pressure than can be accommodated on the low pressure side of the
system 10 and, therefore, can store the required charge of
refrigerant in a much smaller volume than would be allowed in the
accumulator 24. This can allow for a smaller system size and weight
in comparison to a cooling system that attempts to accommodate
system leakage by providing extra volume in the accumulator 24.
* * * * *