U.S. patent application number 14/012587 was filed with the patent office on 2014-03-06 for method of servicing an aircraft cooling system and aircraft cooling system.
The applicant listed for this patent is Airbus Operations GmbH. Invention is credited to Markus Piesker.
Application Number | 20140060091 14/012587 |
Document ID | / |
Family ID | 46924197 |
Filed Date | 2014-03-06 |
United States Patent
Application |
20140060091 |
Kind Code |
A1 |
Piesker; Markus |
March 6, 2014 |
Method of servicing an aircraft cooling system and aircraft cooling
system
Abstract
A method of servicing an aircraft cooling system comprises
connecting a refilling container containing a two-phase refrigerant
to a refrigerant connection provided in a cooling circuit of the
cooling system, supplying refrigerant from the refilling container
into the cooling circuit of the cooling system, and operating a
condenser disposed in the cooling circuit so as to liquefy gaseous
refrigerant flowing through the cooling circuit.
Inventors: |
Piesker; Markus; (Hamburg,
DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Airbus Operations GmbH |
Hamburg |
|
DE |
|
|
Family ID: |
46924197 |
Appl. No.: |
14/012587 |
Filed: |
August 28, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61695312 |
Aug 31, 2012 |
|
|
|
Current U.S.
Class: |
62/77 ; 62/129;
62/292 |
Current CPC
Class: |
F25B 49/022 20130101;
F25B 2341/0661 20130101; F25B 2400/06 20130101; F25B 5/02 20130101;
F25B 2345/0052 20130101; F25B 2345/001 20130101; B64D 2013/0674
20130101; F25B 45/00 20130101; B64F 1/28 20130101; F25B 40/02
20130101; F25B 7/00 20130101; F25B 49/02 20130101 |
Class at
Publication: |
62/77 ; 62/292;
62/129 |
International
Class: |
F25B 45/00 20060101
F25B045/00; F25B 49/02 20060101 F25B049/02 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 31, 2012 |
EP |
12006183.3 |
Claims
1. A method of servicing an aircraft cooling system, the method
comprising the steps: connecting a refilling container containing a
two-phase refrigerant to a refrigerant connection provided in a
cooling circuit of the cooling system, supplying refrigerant from
the refilling container into the cooling circuit of the cooling
system, and operating a condenser disposed in the cooling circuit
so as to liquefy gaseous refrigerant flowing through the cooling
circuit.
2. The method according to claim 1, including at least one of the
steps of: preventing a reflow of refrigerant from the cooling
circuit into the refilling container and liquefying the refrigerant
contained in the refilling container prior to the refrigerant being
supplied into the cooling circuit of the cooling system.
3. The method according to claim 1, including at least one of the
steps of: ceasing operation of the condenser when an amount of
refrigerant in the cooling circuit has reached a predetermined
maximum value and interrupting the supply of refrigerant from the
refilling container into the cooling circuit of the cooling system
when a pressure in the cooling circuit has reached a predetermined
value.
4. The method according to claim 1, including at least one of the
steps of: outputting a first warning signal indicating a required
supply of refrigerant into the cooling circuit when an amount of
refrigerant in the cooling circuit falls below a predetermined
warning value, and outputting a second warning signal indicating a
required supply of refrigerant into the cooling circuit when an
amount of refrigerant in the cooling circuit falls below a
predetermined minimum value, and ceasing operation of the cooling
system when an amount of refrigerant in the cooling circuit falls
below the predetermined minimum value.
5. The method according to claim 1, including the step of
dismounting a component disposed in the cooling circuit from the
cooling circuit and engaging self-sealing couplings connecting the
component to the cooling circuit to prevent refrigerant from
exiting the cooling circuit.
6. The method according to claim 1, including the steps of, prior
to dismounting a component disposed in the cooling circuit from the
cooling circuit, one of: discharging refrigerant from the cooling
circuit by releasing the refrigerant to the ambient, and conveying
refrigerant into a hermetically sealable accumulator disposed in
the cooling circuit thereby collecting the refrigerant in a storage
container.
7. The method according to claim 6, wherein after discharging
refrigerant from the cooling circuit and prior to reintroducing
refrigerant into the cooling circuit, performing at least one of
the additional steps of: evacuating the cooling circuit, and
operating the condenser of the cooling system so as to evaporate
the refrigerant prior to entering the cooling circuit and to
liquefy the gaseous refrigerant upon circulating through the
cooling circuit, including the step of heating the storage
container containing the refrigerant to support evaporation of the
refrigerant in the storage container.
8. An aircraft cooling system comprising: a cooling circuit
allowing circulation of a two-phase refrigerant therethrough, a
refrigerant connection provided in the cooling circuit which, for
servicing of the aircraft cooling system, is connectable to a
refilling container containing the two-phase refrigerant, and a
control unit adapted to operate a condenser disposed in the cooling
circuit so as to liquefy gaseous refrigerant flowing through the
cooling circuit during the supply of refrigerant from the refilling
container into the cooling circuit.
9. The aircraft cooling system according to claim 8, wherein the
refrigerant connection is configured so as to allow a flow of
refrigerant from the refilling container into the cooling circuit,
but to prevent a flow of refrigerant from the cooling circuit into
the refilling container.
10. The aircraft cooling system according to claim 8, further
comprising at least one of: the control unit being adapted to cease
operation of the condenser when an amount of refrigerant in the
cooling circuit has reached a predetermined maximum value, and the
aircraft cooling system comprising means for interrupting the
supply of refrigerant from the refilling container into the cooling
circuit of the cooling system when a pressure in the cooling
circuit has reached a predetermined value.
11. The aircraft cooling system according to claim 8, further
comprising at least one of: a warning signal output device which is
adapted to output a first warning signal indicating a required
supply of refrigerant into the cooling circuit when an amount of
refrigerant in the cooling circuit falls below a predetermined
warning value, a warning signal device which is adapted to output a
second warning signal indicating a required supply of refrigerant
into the cooling circuit when an amount of refrigerant in the
cooling circuit falls below a predetermined minimum value, and the
control unit being adapted to cease operation of the cooling system
when an amount of refrigerant in the cooling circuit falls below
the predetermined minimum value.
12. The aircraft cooling system according to claim 8, further
comprising at least one of: a component disposed in the cooling
circuit is connected to the cooling circuit via self-sealing
couplings which, upon dismounting the component from the cooling
circuit, are adapted to prevent refrigerant from exiting the
cooling circuit, and a hermetically sealable accumulator disposed
in the cooling circuit.
13. The aircraft cooling system according to claim 8, wherein the
control unit, upon reintroducing refrigerant into the cooling
circuit when the cooling circuit, after discharging refrigerant
from the cooling circuit, is evacuated, is adapted to operate the
condenser of the cooling system so as to evaporate the refrigerant
prior to entering the cooling circuit and to liquefy the gaseous
refrigerant upon circulating through the cooling circuit.
14. An arrangement comprising: an aircraft cooling system according
to claim 8, and a servicing unit for servicing the aircraft cooling
system, the servicing unit comprising a first refrigerant
connection adaptor adapted to be connected to the refrigerant
connection of the cooling system so as to connect a refilling
container containing a two-phase refrigerant to a cooling circuit
of the cooling system.
15. The arrangement according to claim 14, wherein the servicing
unit further comprises at least one of: a condenser, a conveying
device, means for interrupting the supply of refrigerant from the
refilling container into the cooling circuit of the cooling system
when a pressure in the cooling circuit has reached a predetermined
value, a second refrigerant connection adaptor adapted to be
connected to the refrigerant connection of the cooling system, an
evacuation device for evacuating the cooling circuit of the cooling
system after discharging refrigerant from the cooling circuit and
prior to reintroducing refrigerant into the cooling circuit, a
storage container, and a heater adapted to heat the storage
container.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] This application claims the benefit of the U.S. Provisional
Application No. 61/695,312, filed on Aug. 31, 2012, and of the
European patent application No. 12 006 183.3 filed on Aug. 31,
2012, the entire disclosures of which are incorporated herein by
way of reference.
BACKGROUND OF THE INVENTION
[0002] The invention relates to a method of servicing an aircraft
cooling system for operation with a two-phase refrigerant, an
aircraft cooling system for operation with a two-phase refrigerant
and an arrangement comprising the aircraft cooling system as well
as a servicing unit for servicing the aircraft cooling system.
[0003] Cooling systems for operation with a two-phase refrigerant
are known from DE 10 2006 005 035 B3, WO 2007/088012 A1, DE 10 2009
011 797 A1 and US 2010/0251737 A1 and may be used to cool various
cooling energy consumers present on board an aircraft such as, for
example, food that is intended to be supplied to the passengers or
heat generating components such as electric or electronic
components. In the cooling systems known from DE 10 2006 005 035
B3, WO 2007/088012 A1, DE 10 2009 011 797 A1 and US 2010/0251737 A1
the phase transitions of the refrigerant flowing through the
circuit that occur during operation of the system allow the latent
heat consumption that then occurs to be utilized for cooling
purposes. The refrigerant mass flow needed to provide a desired
cooling capacity is therefore markedly lower than for example in a
liquid cooling system, in which a one-phase liquid refrigerant is
used.
[0004] Consequently, the cooling systems described in DE 10 2006
005 035 B3, WO 2007/088012 A1, DE 10 2009 011 797 A1 and US
2010/0251737 A1 may have lower tubing cross sections than a liquid
cooling system with a comparable cooling capacity and hence provide
the advantages of a lower installation volume and a lower weight.
What is more, the reduction of the refrigerant mass flow makes it
possible to reduce the conveying capacity needed to convey the
refrigerant through the cooling circuit of the cooling system. This
leads to an increased efficiency of the system because less energy
is needed to operate a corresponding conveying device, such as for
example a pump, and moreover less additional heat generated by the
conveying device during operation of the conveying device has to be
removed from the cooling system.
SUMMARY OF THE INVENTION
[0005] The invention is directed to the object to provide a
reliable and efficient method of servicing an aircraft cooling
system for operation with a two-phase refrigerant. Further, the
invention is directed to the object to provide an aircraft cooling
system for operation with a two-phase refrigerant which can be
serviced in a reliable and efficient manner. Finally, the invention
is directed to the object to provide an arrangement comprising the
aircraft cooling system and a servicing unit for servicing the
aircraft cooling system in a reliable and efficient manner.
[0006] In a method of servicing an aircraft cooling system, a
refilling container containing a two-phase refrigerant is connected
to a refrigerant connection provided in a cooling circuit of the
cooling system. Preferably, the refilling container is connected to
the refrigerant connection of the cooling system in a sealed manner
via a preferably flexible line and a first refrigerant connection
adaptor. The refilling container, the flexible line and the first
refrigerant connection adaptor may be integrated into a preferably
mobile servicing unit which may be formed separate of the aircraft
and be adapted for connection to the aircraft cooling system
exclusively for servicing purposes. The aircraft cooling system
may, for example, be a cooling system which is in particular
suitable for cooling heat generating components or food on board
the aircraft and comprises a cooling circuit allowing circulation
of a two-phase refrigerant therethrough.
[0007] The two-phase refrigerant which circulates in the cooling
circuit of the cooling system is a refrigerant, which upon
releasing cooling energy to a cooling energy consumer is converted
from the liquid to the gaseous state of aggregation and is then
converted back to the liquid state of aggregation. The two-phase
refrigerant may, for example, be R134A (CH2F-CF3). Electric or
electronic systems, such as avionic systems or fuel cell systems
usually have to be cooled at a higher temperature level than food.
For cooling these systems, for example Galden.RTM. can be used as a
two-phase refrigerant. Preferably, however, CO2 is employed as the
two-phase refrigerant, since CO2 is at least substantially
environment-neutral.
[0008] Basically, the cooling system is operated with a
predetermined operating amount of refrigerant circulating in the
cooling circuit which is defined by an amount of refrigerant which
is necessarily required to properly operate the cooling system, and
an additional amount of refrigerant to compensate for leakages of
the system and system tolerances. In order to limit an amount of
refrigerant exiting the cooling system in the event of a leakage of
the system, the predetermined operating amount of refrigerant
circulating in the cooling circuit should be as low as possible.
Small leakages present in the system or service work involving
dismounting of components from the cooling system or replacing
components of the cooling system may, however, cause the amount of
refrigerant circulating in the cooling circuit to fall below a
predetermined minimum value which may, for example, be defined by
the amount of refrigerant which is necessarily required to properly
operate the cooling system.
[0009] The servicing method according to the invention therefore
comprises the step of supplying the refrigerant contained in the
refilling container from the refilling container into the cooling
circuit of the cooling system. In particular, the refrigerant
contained in the refilling container is supplied into the cooling
circuit of the cooling system while there is still a considerable
amount of refrigerant present in the cooling circuit of the cooling
system which might, however, not be sufficient to properly operate
the cooling system.
[0010] During supplying the refrigerant contained in the refilling
container from the refilling container into the cooling circuit of
the cooling system, in the method according to the invention, a
condenser disposed in the cooling circuit is operated so as to
liquefy gaseous refrigerant flowing through the cooling circuit.
Operation of the condenser causes a decrease of the temperature and
hence the pressure of the refrigerant in the cooling circuit of the
cooling system. As a result, refrigerant may be conveyed from the
refilling container into the cooling circuit of the cooling system
in a fast and efficient manner. Further, operation of the condenser
ensures that refrigerant supplied from the refilling container into
the cooling circuit of the cooling system is liquefied immediately
upon entering the cooling circuit. Hence, the period of time which
is necessary to reestablish a ready-to-operate state of the cooling
system after servicing is minimized. The method according to the
invention thus allows a cooling system operated with a two-phase
refrigerant to be serviced in a reliable, time-saving and
cost-effective manner.
[0011] Preferably, operation of the condenser is controlled such
that the pressure of the refrigerant in the cooling circuit of the
cooling system is decreased below the pressure of the refrigerant
in the refilling container. Hence, the refrigerant may be conveyed
from the refilling container into the cooling circuit of the
cooling system driven by the pressure difference between the
refilling container and the cooling circuit, i.e., the difference
between the pressure of the refrigerant in the refilling container
and the pressure of the refrigerant in the cooling circuit. The use
of an additional conveying device for conveying the refrigerant
from the refilling container into the cooling circuit thus can be
limited or even dispensed with.
[0012] In the method of servicing an aircraft cooling system a flow
of refrigerant from the refilling container into the cooling
circuit is allowed, whereas, however, a reflow of refrigerant from
the cooling circuit into the refilling container preferably is
prevented.
[0013] The reflow of refrigerant from the cooling circuit into the
refilling container may be prevented, independent of the pressure
conditions in the refilling container and the cooling circuit, for
example, by means of a check valve which may be integrated into the
refrigerant connection of the cooling circuit or the first
refrigerant connection adaptor of the servicing unit.
[0014] The pressure difference driven supply of refrigerant from
the filling container into the cooling circuit of the cooling
system may slow down or even be interrupted due to a decrease of
the temperature and hence the pressure of the refrigerant in the
refilling container which may result from a large amount of
refrigerant being discharged from the refilling container in a
short period of time. The refrigerant contained in the refilling
container then may be liquefied, for example by means of a
condenser of the servicing unit, prior to being supplied into the
cooling circuit of the cooling system. The liquid refrigerant may
be conveyed into the cooling circuit of the cooling system by means
of a suitable conveying device, such as a pump of the servicing
unit. Further, it is conceivable to also subcool the refrigerant
contained in the refilling container prior to being supplied into
the cooling circuit of the cooling system. Liquefying and optional
subcooling of the refrigerant allows continuing with the supply of
refrigerant from the filling container into the cooling circuit of
the cooling system independent of the pressure conditions in the
refilling container and the cooling circuit.
[0015] Finally, also a pressure difference driven supply of liquid
refrigerant from the refilling container into the cooling circuit
of the cooling system is conceivable. In this case, liquid
refrigerant contained in a lower region of the refilling container
is supplied into the cooling circuit, wherein the pressure in the
refilling container is built up due to the presence of a gas layer
in an upper region of the refilling container. In case the cooling
circuit of the cooling system is refilled merely by a pressure
difference driven supply of liquid refrigerant from the refilling
container into cooling circuit, a servicing unit to be connected to
the cooling system for servicing the cooling system may be or a
particularly simply design and may comprise only one refilling
container.
[0016] In a preferred embodiment of the method of servicing an
aircraft cooling system operation of the condenser is ceased when
an amount of refrigerant in the cooling circuit has reached a
predetermined maximum value. When operation of the condenser is
ceased, residual refrigerant is supplied from the refilling
container into the cooling circuit only until pressure equalization
takes place between the refilling container and the cooling
circuit, i.e., until the pressure of the refrigerant in the
refilling container corresponds to the pressure of the refrigerant
in the cooling circuit. As a result, overfilling of the cooling
circuit with refrigerant is avoided.
[0017] Ceasing operation of the condenser may be achieved by
shutting-down the condenser, for example under the control of a
suitable control unit. Alternatively or additionally thereto, it
is, however, also conceivable to design a storage volume of the
condenser such that it is capable of receiving an amount of
liquefied refrigerant which corresponds to the predetermined
maximum amount of refrigerant in the cooling circuit. When the
storage volume of the condenser is filled, i.e., the amount of
liquefied refrigerant received in the storage volume of the
condenser corresponds to the predetermined maximum amount of
refrigerant in the cooling circuit, the condenser is flooded and
hence liquefaction operation of the condenser is ceased.
[0018] The predetermined maximum value of the amount of refrigerant
in the cooling circuit may correspond to the predetermined
operating amount of refrigerant or be slightly higher than the
predetermined operating amount of refrigerant, but still low enough
to prevent an undesired pressure increase in the cooling circuit,
for example at high ambient temperatures. The amount of liquid
refrigerant in the cooling circuit may be detected by at least one
fill level sensor which may be disposed in an accumulator and/or a
storage container of the cooling system. Further, by measuring the
temperature and the pressure of the refrigerant in the cooling
circuit, the amount of gaseous refrigerant in the cooling circuit
may be derived allowing the total amount of refrigerant present in
the cooling circuit of the cooling system to be determined.
[0019] The supply of residual refrigerant from the refilling
container into the cooling circuit until pressure equalization
takes place between the refilling container and the cooling
circuit, however, still may cause an undesired pressure increase in
the cooling circuit, for example when the refrigerant in the
refilling container has a high temperature due to high ambient
temperatures. Therefore, the supply of refrigerant from the
refilling container into the cooling circuit may be interrupted
when a pressure in the cooling circuit has reached a predetermined
value. An interruption of the supply of refrigerant from the
refilling container into the cooling circuit in dependence of the
pressure in the cooling circuit may be achieved, for example, by
means of a pressure regulator which may be incorporated in the
refrigerant connection of the cooling system or the first
refrigerant connection adaptor of the servicing unit.
[0020] In the method of servicing an aircraft cooling system a
first warning signal indicating a required supply of refrigerant
into the cooling circuit may be output when an amount of
refrigerant in the cooling circuit falls below a predetermined
warning value. The predetermined warning value may be lower than
the predetermined maximum value and the predetermined operating
value of the amount of refrigerant in the cooling circuit, but
still higher than the predetermined minimum value of the amount of
refrigerant in the cooling circuit. The first warning signal may be
a visual signal or an audible signal which may indicate to the
aircraft crew and/or the aircraft service crew that servicing of
the cooling system including refilling of refrigerant into the
cooling circuit of the cooling system will be required in the near
future, but that the cooling system still is ready to operate.
[0021] Alternatively or additionally thereto, a second warning
signal indicating a required supply of refrigerant into the cooling
circuit may be output when an amount of refrigerant in the cooling
circuit falls below the predetermined minimum value. The second
warning signal may be a visual signal or an audible signal which
may indicate to the aircraft crew and/or the aircraft service crew
that servicing of the cooling system including refilling of
refrigerant into the cooling circuit of the cooling system is
required and that the cooling system is no longer ready to
operate.
[0022] Further, operation of the cooling system may be ceased, for
example under the control of a suitable control unit, when an
amount of refrigerant in the cooling circuit falls below the
predetermined minimum value. Similarly, start-up of the cooling
system may be prevented, for example under the control of a
suitable control unit, when the amount of refrigerant in the
cooling circuit is below the predetermined minimum value. Ceasing
operation and/or preventing start-up of the cooling system when the
amount of refrigerant in the cooling circuit is below the
predetermined minimum value protects the components of the cooling
system, in particular a conveying device for conveying the
refrigerant through the cooling circuit of the cooling system, from
damages caused by dry operation of these components.
[0023] Upon dismounting a component disposed in the cooling circuit
from the cooling circuit, self-sealing couplings connecting the
component to the cooling circuit may prevent refrigerant from
exiting the cooling circuit. For example, a chiller and/or the
conveying device for conveying the refrigerant through the cooling
circuit of the cooling system may be connected to the cooling
circuit via self-sealing couplings and thus may be dismounted from
the cooling circuit, for example for servicing purposes, in a
particularly safe, easy and time-saving manner without an excessive
amount of refrigerant leaking from the cooling circuit.
Self-sealing couplings, however, add to the costs and the weight of
the cooling system and also may not be actuatable at high
refrigerant pressures in the cooling circuit of the cooling
system.
[0024] In the method of servicing an aircraft cooling system, prior
to dismounting a component disposed in the cooling circuit of the
cooling system from the cooling circuit, for example for servicing
purposes, refrigerant may be discharged from the cooling circuit or
conveyed into a hermetically sealable accumulator disposed in the
cooling circuit. When the refrigerant present in the cooling
circuit of the cooling system is discharged from the cooling
circuit or conveyed into a hermetically sealable accumulator,
uncontrolled leaking of the refrigerant from the cooling circuit
upon dismounting the component from the cooling circuit is
prevented, even if the component is not connected to the cooling
circuit via self-sealing couplings or in case the self-sealing
couplings are not actuatable due to high refrigerant pressures in
the cooling circuit of the cooling system. In case the refrigerant
is collected in a hermetically sealable accumulator, the
refrigerant is maintained in the cooling circuit of the cooling
system such that it is not necessary to refill the cooling circuit
of the cooling system after the servicing work. Specific servicing
tasks, for example maintenance of the hermetically sealable
accumulator, or safety regulations, however, may require that the
refrigerant in fact is discharged from the cooling circuit.
[0025] Refrigerant discharged from the cooling circuit may either
be released to the ambient or collected in a storage container. For
discharging refrigerant from the cooling circuit of the cooling
system, a second refrigerant connection adaptor may be connected to
the refrigerant connection of the cooling system. The second
refrigerant connection adaptor may comprise a nozzle which is
adapted to control the flow of refrigerant from the cooling circuit
such that freezing of the refrigerant and hence icing of the nozzle
and/or further components of the cooling system and/or the
servicing unit is reliably prevented. Preferably, the refrigerant
is discharged from the cooling circuit of the cooling system in its
liquid state of aggregation.
[0026] The storage container may be incorporated in a servicing
unit in a releasable manner and be connected to the refrigerant
connection of the cooling system via the second refrigerant
connection adaptor and a preferably flexible line. Preferably, the
refrigerant discharged from the cooling circuit of the cooling
system is stored in the storage container in its liquid state of
aggregation and hence at a relatively low pressure. If necessary,
the refrigerant may be liquefied by means of a condenser of the
servicing unit prior to being received in the storage
container.
[0027] After discharging refrigerant from the cooling circuit and
prior to reintroducing refrigerant into the cooling circuit, the
cooling circuit preferably is evacuated. The cooling circuit may be
evacuated by means of an evacuation device such as, for example, a
vacuum pump of the servicing unit. Evacuation of the cooling
circuit allows residual air and humidity, which may affect
operation of the cooling system, to be removed from the cooling
system before refrigerant is reintroduced into the cooling circuit.
The refrigerant reintroduced into the cooling circuit may be the
refrigerant which is discharged from the cooling circuit and
received in the storage container. It is, however, also conceivable
to supply the cooling system entirely or partially with "fresh"
refrigerant which may be supplied to the storage container of the
servicing unit.
[0028] Upon reintroducing refrigerant into the evacuated cooling
circuit, the condenser of the cooling system may be operated so as
to evaporate the refrigerant prior to entering the cooling circuit
and to liquefy the gaseous refrigerant upon circulating through the
cooling circuit. A condenser of the servicing unit preferably is
not operated so as to ensure unhindered evaporation of the
refrigerant which, for example, is contained in the storage
container of the servicing unit. Preferably, the storage container
is heated so as to support evaporation of the refrigerant in the
storage container. As an alternative, it is, however, also
conceivable to convey the refrigerant from the storage container
into the cooling circuit of the cooling system in its liquid state
of aggregation, for example by means of a conveying device of the
servicing unit. Finally, also a pressure difference driven supply
of liquid refrigerant from the storage container into the cooling
circuit of the cooling system is conceivable. In this case, liquid
refrigerant contained in a lower region of the storage container is
supplied into the cooling circuit, wherein the pressure in the
storage container is built up due to the presence of a gas layer in
an upper region of the storage container.
[0029] An aircraft cooling system according to the invention
comprises a cooling circuit allowing circulation of a two-phase
refrigerant therethrough. A refrigerant connection is provided in
the cooling circuit which, for servicing of the aircraft cooling
system, is adapted to be connected to a refilling container
containing the two-phase refrigerant. The cooling system further
comprises a control unit, for example an electronic control unit,
which is adapted to operate a condenser disposed in the cooling
circuit so as to liquefy gaseous refrigerant flowing through the
cooling circuit during the supply of refrigerant from the refilling
container into the cooling circuit.
[0030] The refrigerant connection of the cooling system may be
designed so as to allow a flow of refrigerant from the refilling
container into the cooling circuit, but to prevent a flow of
refrigerant from the cooling circuit into the refilling container.
For example, a check valve may be integrated into the refrigerant
connection.
[0031] The control unit may further be adapted to cease operation
of the condenser when an amount of refrigerant in the cooling
circuit has reached a predetermined maximum value. Alternatively or
additionally thereto, a storage volume of the condenser may be
designed such that it is capable of receiving an amount of
liquefied refrigerant which corresponds to the predetermined
maximum amount of refrigerant in the cooling circuit. When the
storage volume of the condenser is filled, i.e., the amount of
liquefied refrigerant received in the storage volume of the
condenser corresponds to the predetermined maximum amount of
refrigerant in the cooling circuit, the condenser is flooded and
hence liquefaction operation of the condenser is ceased.
[0032] The control unit may further be adapted to interrupt the
supply of refrigerant from the refilling container into the cooling
circuit of the cooling system when an amount of refrigerant in the
cooling circuit has reached a predetermined maximum value. For
example, the control unit may be adapted to control a suitable
valve of the cooling system into a closed position wherein the
valve interrupts the flow of refrigerant from the refilling
container into the cooling circuit of the cooling system.
Alternatively or additionally thereto, the control unit of the
cooling system and/or a control unit of a servicing unit may be
adapted to control a suitable valve of the servicing unit into a
closed position wherein the valve interrupts the flow of
refrigerant from the refilling container into the cooling circuit
of the cooling system. Finally, the control unit of the cooling
system and/or the control unit of a servicing unit may be adapted
to cease operation of the servicing unit to interrupt the supply of
refrigerant from the refilling container into the cooling circuit
of the cooling system.
[0033] The aircraft cooling system may further comprise means for
interrupting the supply of refrigerant from the refilling container
into the cooling circuit of the cooling system when a pressure in
the cooling circuit has reached a predetermined value. An
interruption of the supply of refrigerant from the refilling
container into the cooling circuit in dependence of the pressure in
the cooling circuit may be achieved, for example, by means of a
pressure regulator incorporated in the refrigerant connection of
the cooling system.
[0034] The aircraft cooling system may further comprise a warning
signal output device which is adapted to output a first warning
signal indicating a required supply of refrigerant into the cooling
circuit when an amount of refrigerant in the cooling circuit falls
below a predetermined warning value, and/or to output a second
warning signal indicating a required supply of refrigerant into the
cooling circuit when an amount of refrigerant in the cooling
circuit falls below a predetermined minimum value.
[0035] Further, the control unit may be adapted to cease operation
of the cooling system when an amount of refrigerant in the cooling
circuit falls below the predetermined minimum value. Similarly, the
control unit may be adapted to prevent start-up of the cooling
system when the amount of refrigerant in the cooling circuit is
below the predetermined minimum value.
[0036] A component disposed in the cooling circuit, such as, for
example, a chiller or a conveying device, may be connected to the
cooling circuit via self-sealing couplings which, upon dismounting
the component from the cooling circuit, are adapted to prevent
refrigerant from exiting the cooling circuit.
[0037] Further, the aircraft cooling system may comprise a
hermetically sealable accumulator disposed in the cooling
circuit.
[0038] The control unit of the aircraft cooling system, upon
reintroducing refrigerant into the cooling circuit when the cooling
circuit, after discharging refrigerant from the cooling circuit, is
evacuated, may be adapted to operate the condenser of the cooling
system so as to evaporate the refrigerant prior to entering the
cooling circuit and to liquefy the gaseous refrigerant upon
circulating through the cooling circuit.
[0039] An arrangement according to the invention comprises an above
described aircraft cooling system and a servicing unit for
servicing the aircraft cooling system. The servicing unit comprises
a first refrigerant connection adaptor adapted to be connected to
the refrigerant connection of the cooling system so as to connect a
refilling container containing a two-phase refrigerant to a cooling
circuit of the cooling system.
[0040] The servicing unit preferably is formed separate from the
aircraft and may be designed as a movable device which, for
example, comprises a carriage onto which the components of
servicing unit are mounted. The servicing unit preferably further
comprises a condenser. The condenser may be used for liquefying
refrigerant contained in a refilling container prior to being
supplied into the cooling circuit of the cooling system, for
liquefying refrigerant discharged from the cooling circuit of the
cooling system prior to being received in a storage container
and/or for liquefying refrigerant prior to being reintroduced into
the cooling circuit when the cooling circuit, after discharging
refrigerant from the cooling circuit, is evacuated.
[0041] The servicing unit may further comprise a conveying device
which may be used for conveying refrigerant from the refilling
container into the cooling circuit of the cooling system and/or for
conveying refrigerant from the cooling circuit of the cooling
system into the storage container. Preferably, the conveying device
of the servicing unit is designed in the form of a pump and hence
should be operated with refrigerant in its liquid state of
aggregation.
[0042] The servicing unit may further comprise means for
interrupting the supply of refrigerant from the refilling container
into the cooling circuit of the cooling system, when a pressure in
the cooling circuit has reached a predetermined value. For example,
a suitable pressure regulator may be incorporated in the first
refrigerant connection adaptor of the servicing unit. Further, the
servicing unit may comprise means for interrupting the supply of
refrigerant from the refilling container into the cooling circuit
of the cooling system, when an amount of refrigerant in the cooling
circuit has reached a predetermined value.
[0043] A second refrigerant connection adaptor of the servicing
unit may be adapted to be connected to the refrigerant connection
of the cooling system so as to discharge refrigerant from the
cooling circuit of the cooling system. The second refrigerant
connection adaptor may comprise a nozzle which is adapted to
control the flow of refrigerant from the cooling circuit such that
freezing of the refrigerant and hence icing of the nozzle and/or
further components of the cooling system and/or the servicing unit
is reliably prevented.
[0044] The servicing unit may further comprise an evacuation device
such as, for example, a vacuum pump which may be adapted to
evacuate the cooling circuit of the cooling system after
discharging refrigerant from the cooling circuit and prior to
reintroducing refrigerant into the cooling circuit.
[0045] The servicing unit may also comprise a heater which is
adapted to heat the storage container of the servicing unit so as
to support evaporation of the refrigerant in the storage
container.
BRIEF DESCRIPTION OF THE DRAWINGS
[0046] FIG. 1 is a schematic drawing which depicts an arrangement
comprising an aircraft cooling system suitable for operation with a
two-phase refrigerant and a servicing unit for servicing the
aircraft cooling system.
[0047] FIG. 2 is a schematic drawing which depicts an arrangement
comprising an aircraft cooling system suitable for operation with a
two-phase refrigerant and a servicing unit for servicing the
aircraft cooling system in a second embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0048] The arrangement 100 depicted in FIG. 1 comprises a cooling
system 10 which on board an aircraft, for example, may be employed
to cool food provided for supplying to the passengers. The cooling
system 10 comprises a cooling circuit 12 allowing circulation of a
two-phase refrigerant therethrough. The two-phase refrigerant may
for example be CO2 or R134A. Four evaporators 14a, 14b, 14c, 14d
are disposed in the cooling circuit 12. Each evaporator 14a, 14b,
14c, 14d comprises a refrigerant inlet 16a, 16b, 16c, 16d and a
refrigerant outlet 18a, 18b, 18c, 18d. The refrigerant flowing
through the cooling circuit 12 is supplied to the refrigerant
inlets 16a, 16b, 16c, 16d of the evaporators 14a, 14b, 14c, 14d in
its liquid state of aggregation. Upon flowing through the
evaporators 14a, 14b, 14c, 14d the refrigerant releases its cooling
energy to a cooling energy consumer which in the embodiment of a
cooling system 10 depicted in FIG. 1 is formed by the food to be
cooled. Upon releasing its cooling energy, the refrigerant is
evaporated and hence exits the evaporators 14a, 14b, 14c, 14d at
the refrigerant outlets 18a, 18b, 18c, 18d of the evaporators 14a,
14b, 14c, 14d in its gaseous state of aggregation. The supply of
refrigerant to the evaporators 14a, 14b, 14c, 14d is controlled by
respective valves 20a, 20b, 20c, 20d which are disposed in the
cooling circuit 12 upstream of the evaporators 14a, 14b, 14c, 14d,
respectively.
[0049] Further, the cooling system 10 comprises a first, a second
and a third condenser 22a, 22b, 22c. Each condenser 22a, 22b, 22c
has two refrigerant inlets 24a, 24a', 24b, 24b', 24c, 24c' and two
refrigerant outlets 26a, 26a', 26b, 26b', 26c, 26c'. The
refrigerant which is evaporated in the evaporators 14a, 14b, 14c,
14d, via a portion of the cooling circuit 12 downstream of the
evaporators 14a, 14b, 14c, 14d and upstream of the condensers 22a,
22b, 22c, is supplied to the refrigerant inlets 24a, 24a', 24b,
24b' of the condensers 22a, 22b, 22c in its gaseous state of
aggregation. The condensers 22a, 22b, 22c are thermally coupled to
respective chillers 27a, 27b, 27c which are connected to the
cooling circuit 12 of the cooling system 10 via self-sealing
couplings. Alternatively, the condensers 22a, 22b, 22c, however,
also may be coupled to a different cold source such as, for
example, an outer skin heat exchanger of the aircraft. The cooling
energy provided by the chillers 27a, 27b, 27c in the condensers
22a, 22b, 22c is used to condense the refrigerant. Thus, the
refrigerant exits the condensers 22a, 22b, 22c at the refrigerant
outlets 26a, 26a', 26b, 26b', 26c, 26c' of the condensers 22a, 22b,
22c in its liquid state of aggregation.
[0050] The refrigerant outlets 26a, 26a', 26b, 26b', 26c, 26c' of
the condensers 22a, 22b, 22c each are connected to a storage
container 28a, 28a', 28b, 28b', 28c, 28c', 28d, 28d' which is
arranged downstream and below each one of the condensers 22a, 22b,
22c. The storage containers 28a, 28a', 28b, 28b', 28c, 28c', 28d,
28d', which may also be formed integral with the condensers 22a,
22b, 22c, are connected to subcoolers 30a, 30b, 30c which are
arranged downstream and below the storage containers 28a, 28a',
28b, 28b', 28c, 28c', 28d, 28d'. Liquid refrigerant may be conveyed
gravity-driven from the condensers 22a, 22b, 22c into the storage
containers 28a, 28a', 28b, 28b', 28c, 28c', 28d, 28d' and further
into the subcoolers 30a, 30b, 30c. The subcoolers 30a, 30b, 30c may
also be formed integral with the condensers 22a, 22b, 22c.
[0051] The cooling circuit 12 of the cooling system 10 comprises
two loops 12a, 12a' which are hermetically sealed from each other.
Two evaporators 14a, 14b are disposed in the first cooling circuit
loop 12a, and two evaporators 14c, 14d are disposed in the second
cooling circuit loop 12a'. A first conveying device 32a designed in
the form of a pump serves to convey refrigerant through the first
cooling circuit loop 12a and a second conveying device 32b also
designed in the form of a pump serves to convey refrigerant through
the second cooling circuit loop 12a'. The conveying devices 32a,
32b are connected to the cooling circuit 12 of the cooling system
10 via self-sealing couplings. Each one of the condensers 22a, 22b,
22c is connected to first and the second conveying device 32a, 32b
and hence to the first and the second cooling circuit loop 12a,
12a' so as to provide for redundancy in the event of a
malfunctioning of one of the condensers 22a, 22b, 22c.
[0052] In the first cooling circuit loop 12a a first accumulator
34a is connected to the refrigerant inlet 24a of the condenser 22a,
wherein the supply of refrigerant from the first accumulator 34a to
the condenser 22a is controlled by means of a valve 36a. In the
second cooling circuit loop 12a' a valve 36b controls the supply of
refrigerant from a second accumulator 34b to the refrigerant inlet
24c' of the condenser 22c. While the valve 36a provided in the
first cooling circuit loop 12a merely serves to control the flow of
refrigerant between the first accumulator 34a and the condenser
22a, the valve 36b disposed in the second cooling circuit loop 12a'
is designed in the form of a 3/2 control valve which may either
allow refrigerant to be conveyed into the second accumulator 34b or
the condenser 22c by the second conveying device 32b or allow
refrigerant to flow from the second accumulator 34b to the
refrigerant inlet 24c' of the condenser 22c. A pressure regulating
valve 37 is disposed upstream of the valve 36b and downstream of
the second conveying device 32b. The pressure regulating valve 37
is adapted to open or close in dependence on a pressure difference
acting on the valve 37. In the first cooling circuit loop 12a the
supply of refrigerant from the first conveying device 32a to the
first accumulator 34a is controlled by means of a valve 38.
[0053] In an alternative embodiment of the cooling system 10 the
accumulators 34a, 34b may simply be designed as an "additional
volume" which at a predetermined temperature limits the pressure in
the cooling circuit 12. The accumulators 34a, 34b then may be
connected to only a single line which opens into the accumulators
34a, 34b in a lower region, preferably at the lowest point of the
accumulators 34a, 34b and connects the accumulators 34a, 34b to the
condensers 22a, 22b, 22c.
[0054] Cooling circuit control valves 40a, 40b are disposed in the
first and the second cooling circuit loop 12a, 12a' downstream of
the evaporators 14a, 14b, 14c, 14d and upstream of the condensers
22a, 22b, 22c. Further cooling circuit control valves 42a, 42b are
disposed in the first and the second cooling circuit loop 12a, 12a'
upstream of the evaporators 14a, 14b, 14c, 14d and downstream of
the condensers 22a, 22b, 22c. In their closed state, the cooling
circuit control valves 40a, 40b, 42a, 42b seal a high pressure
section of the cooling circuit loops 12a, 12a' from a low pressure
section of the cooling circuit loops 12a, 12a'. Finally, cooling
circuit control valves 43a, 43b are disposed in the first and the
second cooling circuit loop 12a, 12a' upstream of the accumulators
34a, 34b. By closing or suitably controlling the valves 36a, 36b,
38, 43a, 43b the accumulators 34a, 34b may be hermetically
sealed.
[0055] The accumulators 34a, 34b are connected to the cooling
circuit 12 via self-sealing couplings. For dismounting the
accumulators 34a, 34b from the cooling circuit 12, the valves 36a,
36b, 38, 43a, 43b may be closed and the accumulators 34a, 34b may
be released from the cooling circuit 12 without considerable
amounts of refrigerant exiting the cooling system 10 by simply
actuating the self-sealing couplings. The accumulators 34a, 34b may
be released from the cooling circuit 12 in an empty state or also
with refrigerant received therein. If desired, an accumulator 34a,
34b which is filled with the refrigerant present in the cooling
circuit 12 of the cooling system 10 may be replaced by a
replacement accumulator 34a, 34b which is filled with a desired
amount of "fresh" refrigerant. By replacing the accumulators 34a,
34b, refilling of the cooling circuit 12 with refrigerant may be
omitted. For replacing the accumulators 34a, 34b, it may be
advantageous to relieve the pressure in the cooling circuit 12, if
necessary, to a pressure corresponding to the ambient pressure. For
relieving the pressure in the cooling circuit 12, refrigerant may
be discharged from the cooling circuit 12 by means of the servicing
unit 56 as discussed in detail below. In case the refrigerant is
environment-neutral, it is, however, also conceivable to release
the refrigerant from the cooling circuit 12 to the ambient.
[0056] In the embodiment of a cooling system 10 shown in the
drawing, the valves 36a, 36b, 38, 43a, 43b are automatically
actuatable valves. It is, however, also conceivable to design the
valves 36a, 36b, 38, 43a, 43b as manually actuatable valves. An
actuating lever for actuating manually actuatable valves 36a, 36b,
38, 43a, 43b then, however, should be designed in such a manner
that unintended misuse of the lever is prevented. For example, the
actuating lever of a valve 36a, 36b, 38, 43a, 43b could be designed
such that the lever, for actuating the valve 36a, 36b, 38, 43a,
43b, has be pressed into the valve 36a, 36b, 38, 43a, 43b and,
after the actuation of the valve 36a, 36b, 38, 43a, 43b,
automatically falls out of the valve 36a, 36b, 38, 43a, 43b or
latches in an idle position.
[0057] The cooling system 10 further comprises pressure relief
valves 44a, 44b which are connected to a respective one of the
cooling circuit loops 12a, 12a' downstream of a respective one of
the cooling circuit control valves 42a, 42b. Pressure relief valves
46a, 46b are connected to a respective one of the cooling circuit
loops 12a, 12a' upstream of a respective one of the cooling circuit
control valves 40a, 40b. Pressure relief valves 48a, 48b are
connected to a respective one of the cooling circuit loops 12a,
12a' downstream of a respective one of the cooling circuit control
valves 40a, 40b. Finally, pressure relief valves 49a, 49b are
connected to the accumulators 34a, 34b. The pressure relief valves
44a, 44b, 46a, 46b, 48a, 48b, 49a, 49b are designed as mechanically
actuatable valves which automatically open in case a pressure
difference acting on the valves 44a, 44b, 46a, 46b, 48a, 48b, 49a,
49b exceeds a threshold value which is determined by the design of
the valves 44a, 44b, 46a, 46b, 48a, 48b, 49a, 49b. It is, however,
also conceivable to design the pressure relief valves 44a, 44b,
46a, 46b, 48a, 48b, 49a, 49b in the form of burst discs or bust
discs may be provided in addition to the pressure relief valves
44a, 44b, 46a, 46b, 48a, 48b, 49a, 49b.
[0058] The cooling system 10 further is provided with refrigerant
connections 50a, 50b. The refrigerant connection 50a associated
with the first cooling circuit loop 12a is connected to the first
accumulator 34a, whereas the refrigerant connection 50a associated
with the second cooling circuit loop 12a is connected to the second
accumulator 34b. Further, the refrigerant connection 50a associated
with the first cooling circuit loop 12a is connected to an outlet
side of the first conveying device 32a, wherein a valve 51a serves
to control the supply of refrigerant from the outlet side of the
first conveying device 32a to the refrigerant connection 50a.
Similarly, the refrigerant connection 50b associated with the
second cooling circuit loop 12b is connected to an outlet side of
the second conveying device 32b, wherein a valve 51b serves to
control the supply of refrigerant from the outlet side of the
second conveying device 32b to the refrigerant connection 50b. Each
one of the refrigerant connections 50a, 50b comprises an integrated
check valve and an integrated pressure regulator (not shown in the
drawing). Operation of the cooling system 10 is controlled by means
of an electronic control unit 52. In particular, the electronic
control unit 52 controls operation of the evaporators 14a, 14b,
14c, 14d, the condensers 22a, 22b and the various valves employed
in the cooling circuit 12.
[0059] Fill level sensors (not shown in the drawing) are provided
in the accumulators 34a, 34b and/or the storage containers 28a,
28a', 28b, 28b', 28c, 28c'. The fill level sensors serve to detect
the amount of liquid refrigerant present in the cooling circuit 12.
Further, the cooling system 10 comprises sensors (also not shown in
the drawing) which serve to detect the temperature and the pressure
of the refrigerant in the cooling circuit 12 and hence allow the
amount of gaseous refrigerant present in the cooling circuit 12 to
be determined. Finally, suitable sensors (also not shown in the
drawing) are provided which detect the operating state of the
valves 36a, 36b, 38, 43a, 43b, i.e., detect whether the
accumulators 34a, 34b are hermetically sealed or connected to the
cooling circuit 12. The signals of all sensors are transmitted to
the control unit 52. Finally, a warning signal output device 54a,
54b is associated with each one of the first and the second cooling
circuit loop 12a, 12a'.
[0060] The arrangement 100 further comprises a servicing unit 56
for servicing the aircraft cooling system 10. The servicing unit 56
is designed as a movable device which comprises a carriage 57 onto
which the components of servicing unit 100 are mounted. The
servicing unit 56 comprises a first refrigerant connection adaptor
58 adapted to be connected to a refrigerant connection 50a, 50b of
the cooling system 10 so as to connect a refilling container 60
containing a two-phase refrigerant to the cooling circuit 12 of the
cooling system 10. The servicing unit 56 further comprises a
condenser 62 which is provided with cooling energy from a chiller
64 and a conveying device 66 which is designed in the form of a
pump.
[0061] A second refrigerant connection adaptor 68 of the servicing
unit 56 is adapted to be connected to a refrigerant connection 50a,
50b of the cooling system 10 so as to discharge refrigerant from
the cooling circuit 12 of the cooling system 10. The second
refrigerant connection adaptor 68 comprises a nozzle (not shown in
the drawing) which is adapted to control the flow of refrigerant
from the cooling circuit 12 such that freezing of the refrigerant
and hence icing of the nozzle and/or further components of the
cooling system 10 and/or the servicing unit 56 is prevented.
Alternatively or additionally to the check valve and the pressure
regulator integrated in the refrigerant connections 50a, 50b of the
cooling system 10, also the first and/or the second refrigerant
connection adaptor 58, 68 of the servicing unit 56 may comprise an
integrated check valve and an integrated pressure regulator (not
shown in the drawing).
[0062] The refrigerant connections 50a, 50b of the cooling system
10 are adapted to be connected to either the first or the second
refrigerant connection adaptor 58, 68 of the servicing unit 56.
When the refrigerant connections 50a, 50b of the cooling system 10
are connected to the first refrigerant connection adaptor 58 of the
servicing unit 56 for introducing refrigerant into the cooling
circuit 12, a mechanical or electrical mechanism of the refrigerant
connections 50a, 50b (not shown in the drawing), which is actuated
upon connecting the first refrigerant connection adaptor 58 to the
refrigerant connections 50a, 50b, provides for an activation of the
check valve and the pressure regulator integrated in the
refrigerant connections 50a, 50b. Hence, refrigerant is prevented
to flow from the cooling circuit 12 in the direction of the
servicing unit. In addition, built-up of excessive pressure in the
cooling circuit 12 is prevented.
[0063] When, however, the refrigerant connections 50a, 50b of the
cooling system 10 are connected to the second refrigerant
connection adaptor 68 of the servicing unit 56 for discharging
refrigerant from the cooling circuit 12, the mechanical or
electrical mechanism of the refrigerant connections 50a, 50b, which
is actuated upon connecting the second refrigerant connection
adaptor 68 to the refrigerant connections 50a, 50b, provides for a
deactivation of the check valve and the pressure regulator
integrated in the refrigerant connections 50a, 50b. Hence, a flow
of refrigerant from the cooling circuit 12 in the direction of the
servicing unit is enabled. An undesired flow of refrigerant from
the servicing unit 56 into the cooling circuit 12 and/or the
built-up of excessive pressure in the servicing unit 56 are
prevented when the second refrigerant connection adaptor 68
comprises an integrated check valve and/or an integrated pressure
regulator.
[0064] The servicing unit 56 further comprises an evacuation device
70 in the form of a vacuum pump. Finally, the servicing unit 56
comprises a heater 72 which is adapted to heat a storage container
74 of the servicing unit 56.
[0065] In the following, operation of the cooling system 10 will be
described. Upon system start-up, the control unit 52 controls the
operation of the cooling system 10 such that the chillers 27a, 27b,
27c are operated and refrigerant is liquefied in the condensers
22a, 22b, 22c and supercooled in the supercoolers 30a, 30b, 30c.
Due to the conveying devices 32a, 32b being arranged below the
condensers 22a, 22b, 22c the conveying devices 32a, 32b are flooded
by the refrigerant liquefied in the condensers 22a, 22b, 22c. Since
the conveying devices 32a, 32b are flooded before operation of the
conveying devices 32a, 32b is started, it is not necessary that the
conveying devices 32a, 32b are designed in the form of a
self-sucking pump.
[0066] When the level of the liquid refrigerant in the conveying
devices 32a, 32b has reached a level which ensures that dry
operation of the conveying devices 32a, 32b is avoided, operation
of the conveying devices 32a, 32b is started. The conveying devices
32a, 32b convey refrigerant liquefied in the condensers 22a, 22b,
22c into the accumulators 34a, 34b via valves 36a, 36b. The valves
42a, 42b are closed so as to prevent refrigerant to be conveyed to
the evaporators 14a, 14b, 14c, 14d. This operation is continued
until the amount of liquid refrigerant present in the cooling
circuit 12 and stored in the accumulators 34a, 34b is sufficient to
allow that cooling system components which are disposed downstream
of the conveying devices 32a, 32b, i.e., the tubing of the cooling
circuit 12 and the evaporators 14a, 14b, 14c, 14d can be flooded
with liquid refrigerant.
[0067] An operating state of the cooling system 10 wherein the
condensers 22a, 22b, 22c are operated so as liquefy refrigerant,
although the amount of liquid refrigerant present in the cooling
circuit 12 is already sufficient to allow the desired flooding of
cooling system components, while the supply of refrigerant to the
evaporators 14a, 14b, 14c, 14d, however, still is interrupted is
designated as a stand-by operational state of the cooling system
10. The control device 52 of the cooling system 10 controls the
operation of the cooling system 10 in such a way that the cooling
system 10 is operated in its stand-by operational state as long as
possible.
[0068] The stand-by operational state of the cooling system 10 is
terminated and normal operation of the cooling system 10 is
initiated when cooling energy has to be supplied to cooling energy
consumers. To initiate normal operation of the cooling system 10,
the valves 42a, 42b are opened such that liquid refrigerant may be
conveyed to the evaporators 14a, 14b, 14c, 14d by the conveying
devices 32a, 32b.
[0069] Further, the supply of refrigerant to the evaporators 14a,
14b, 14c, 14d is controlled by opening the valves 20a, 20b, 20c,
20d. When the valves 20a, 20b, 20c, 20d are open, the valves 36a,
36b interrupt the supply of refrigerant to the accumulators 34a,
34b such that the refrigerant exiting the condensers 22a, 22b, 22c
is exclusively conveyed to the evaporators 14a, 14b, 14c, 14d.
[0070] During further normal operation of the cooling system 10,
the valves 42a, 42b may, however, again be partially closed or
entirely closed so as to control the pressure of the refrigerant
within the cooling circuit 12 in dependence on the operating state
of the evaporators 14a, 14b, 14c, 14d, i.e., in dependence on the
cooling energy demand of the cooling energy consumers supplied with
cooling energy by the cooling system 10. Further, the pressure of
the refrigerant within the cooling circuit 12 and the supply of
refrigerant to the evaporators 14a, 14b, 14c, 14d is controlled by
appropriately controlling the speed of the conveying devices 32a,
32b. Specifically, the operating speed of the conveying devices
32a, 32b is increased when the cooling requirement of the cooling
energy consumers supplied with cooling energy by the evaporators
14a, 14b, 14c, 14d increases.
[0071] During normal operation of the cooling system 10, i.e., when
refrigerant is evaporated in the evaporators 14a, 14b, 14c, 14d so
as to supply cooling energy to respective cooling energy consumers,
the control unit 52 controls the valves 40a, 40b such that the
pressure in the cooling circuit 12 downstream of the evaporators
14a, 14b, 14c, 14d and upstream of the condensers 22a, 22b, 22c is
higher than downstream of the condensers 22a, 22b, 22c and upstream
of the evaporators 14a, 14b, 14c, 14d. Specifically, the valves
40a, 40b are operated so as to increase or decrease a flow
cross-section of the cooling circuit 12 between the evaporators
14a, 14b, 14c, 14d and the condensers 22a, 22b, 22c.
[0072] The control device 52 during normal operation of the cooling
system 10 controls the supply of refrigerant to the evaporators
14a, 14b, 14c, 14d in dependence on the operational state of the
evaporators 14a, 14b, 14c, 14d, i.e., the cooling energy
requirement of the cooling energy consumers coupled to the
evaporators 14a, 14b, 14c, 14d such that a dry evaporation of the
refrigerant occurs in the evaporators 14a, 14b, 14c, 14d. The
supply of refrigerant to the individual evaporators 14a, 14b, 14c,
14d is controlled by suitably controlling the respective valves
20a, 20b, 20c, 20d.
[0073] In the following, servicing of the cooling system 10 using
the servicing unit 56 will be described. Basically, the cooling
system 10 is operated with a predetermined operating amount of
refrigerant circulating in the cooling circuit 12 which is defined
by an amount of refrigerant which is necessarily required to
properly operate the cooling system 10, and an additional amount of
refrigerant to compensate for leakages of the system 10 and system
tolerances. Small leakages present in the system 10 or service work
involving dismounting of components from the cooling system 10 or
replacing components of the cooling system 10 may, however, cause
the amount of refrigerant circulating in the cooling circuit 12 to
fall below a predetermined minimum value which may, for example, be
defined by the amount of refrigerant which is necessarily required
to properly operate the cooling system 10.
[0074] The warning signal output units 54a, 54b of the cooling
system 10 output a first warning signal indicating a required
supply of refrigerant into the cooling circuit 12 when an amount of
refrigerant in the cooling circuit 12, which is measured by means
of the fill level sensors, the pressure sensors and the temperature
sensors of the cooling system 10, falls below a predetermined
warning value. The predetermined warning value is lower than the
predetermined operating value of the amount of refrigerant in the
cooling circuit 12, but still higher than the predetermined minimum
value of the amount of refrigerant in the cooling circuit 12. The
first warning signal may be a visual signal or an audible signal
which indicates to an aircraft crew or a service crew that
servicing of the cooling system 10 including refilling of
refrigerant into the cooling circuit 12 of the cooling system 10
will be required in the near future, but that the cooling system 10
still is ready to operate.
[0075] Further, the warning signal output units 54a, 54b of the
cooling system 10 output a second warning signal indicating a
required supply of refrigerant into the cooling circuit 12 when an
amount of refrigerant in the cooling circuit 12, which is measured
by means of the fill level sensors, the pressure sensors and the
temperature sensors of the cooling system 10, falls below the
predetermined minimum value. The second warning signal may be a
visual signal or an audible signal which indicates to an aircraft
crew or a service crew that servicing of the cooling system 10
including refilling of refrigerant into the cooling circuit 12 of
the cooling system 10 is required and that the cooling system 10 is
no longer ready to operate.
[0076] In addition, the control unit 52 ceases operation of the
cooling system 10 when an amount of refrigerant in the cooling
circuit, which is measured by means of the fill level sensors, the
pressure sensors and the temperature sensors of the cooling system
10, falls below the predetermined minimum value. Similarly,
start-up of the cooling system 10 is prevented by the control unit
52 when the amount of refrigerant in the cooling circuit 12 is
below the predetermined minimum value. Ceasing operation and/or
preventing start-up of the cooling system 10 when the amount of
refrigerant in the cooling circuit 10 is below the predetermined
minimum value protects the components of the cooling system 10, in
particular the conveying devices 32a, 32b from damages caused by
dry operation.
[0077] To refill the cooling circuit 12 of the cooling system 10
with refrigerant, the residual refrigerant present in the cooling
circuit 12 may be conveyed into the accumulators 34a, 34b.
Thereafter, the accumulators 34a, 34b may be sealed by closing the
valves 36a, 36b, 38, 43a, 43b. Finally the accumulators 34a, 34b
may be dismounted from the cooling circuit and replaced by
replacement accumulators 34a, 34b filled with a desired amount of
"fresh" refrigerant, wherein the self-sealing couplings via which
the accumulators 34a, 34b are connected to the cooling circuit 12
prevent refrigerant from leaking from the cooling circuit 12 upon
dismounting the accumulators 34a, 34b. Instead of the relatively
expensive and heavy self-sealing couplings, simple couplings may be
used for connecting the accumulators 34a, 34b to the cooling
circuit 12. In this case, for replacing the accumulators 34a, 34b,
it might be necessary to relieve the pressure in the cooling
circuit 12. For relieving the pressure in the cooling circuit 12,
refrigerant may be discharged from the cooling circuit 12 by means
of the servicing unit 56 as discussed in detail below. In case the
refrigerant is environment-neutral, it is, however, also
conceivable to release the refrigerant from the cooling circuit 12
to the ambient.
[0078] Alternatively or additionally thereto, the refilling
container 60 of the servicing unit 56, which contains a two-phase
refrigerant of the same type as the refrigerant circulating in the
cooling circuit 12 of the cooling system 10, is connected to a
refrigerant connection 50a, 50b of the cooling system 10 in a
sealed manner via the first refrigerant connection adaptor 58 and a
flexible line. Thereafter, the refrigerant contained in the
refilling container 60 is supplied from the refilling container 60
into the cooling circuit 12 of the cooling system 10 while at least
one of the condensers 22a, 22b, 22c disposed in the cooling circuit
12 of the cooling system 10, under the control of the control unit
52, is operated so as to liquefy gaseous refrigerant flowing
through the cooling circuit 12. To avoid an overfilling of the
cooling circuit 12 due to the valves 36a, 36b, 38, 43a, 43b being
unintentionally closed and sealing the accumulators 34a, 34b from
the cooling circuit 12, the at least one of the condensers 22a,
22b, 22c is operated only in case the sensors for detecting the
operating state of the valves 36a, 36b, 38, 43a, 43b detect that
the accumulators 34a, 34b are connected to the cooling circuit 12
and hence can receive refrigerant supplied into the cooling circuit
12 from the refilling container 60.
[0079] Operation of the condenser 22a, 22b, 22c causes a decrease
of the temperature and hence the pressure of the refrigerant in the
cooling circuit 12 of the cooling system 10. As a result,
refrigerant may be conveyed from the refilling container 60 into
the cooling circuit 12 of the cooling system 10 in a fast and
efficient manner. Further, operation of the condenser 22a, 22b, 22c
ensures that refrigerant supplied from the refilling container 60
into the cooling circuit 12 of the cooling system 10 is liquefied
immediately upon entering the cooling circuit 12. Hence, the period
of time which is necessary to bring the cooling system 10 into a
state ready to operate after servicing is minimized.
[0080] In particular, operation of the at least one of the
condensers 22a, 22b, 22c, by means of the control unit 52, is
controlled such that the pressure of the refrigerant in the cooling
circuit 12 of the cooling system 10 is decreased below the pressure
of the refrigerant in the refilling container 60. Hence, the
refrigerant may be conveyed from the refilling container 60 into
the cooling circuit 12 of the cooling system 10 driven by the
pressure difference between the refilling container 60 and the
cooling circuit 12, i.e., the difference between the pressure of
the refrigerant in the refilling container 60 and the pressure of
the refrigerant in the cooling circuit 12.
[0081] The check valve integrated into the refrigerant connection
50a, 50b which is connected to the first refrigerant connection
adaptor 58 of the servicing unit 52 ensures that refrigerant may
flow of from the refilling container 60 into the cooling circuit
12, but that a reflow of refrigerant from the cooling circuit 12
into the refilling container 60 is prevented.
[0082] In case the pressure difference driven supply of refrigerant
from the filling container 60 into the cooling circuit 12 of the
cooling system 10 slows down or is even interrupted due to a
decrease of the temperature and hence the pressure of the
refrigerant in the refilling container 60, the refrigerant
contained in the refilling container 60 is liquefied by means of
the condenser 62 of the servicing unit 52 and thereafter conveyed
into the cooling circuit 12 of the cooling system 10 by means of
the conveying device 66 of the servicing unit 52 in its liquid
state of aggregation.
[0083] Under the control of the control unit 52, operation of the
at least one of the condensers 22a, 22b, 22c of the cooling system
10 is ceased when an amount of refrigerant in the cooling circuit
12, which is measured by means of the fill level sensors, the
pressure sensors and the temperature sensors of the cooling system
10, has reached a predetermined maximum value. The predetermined
maximum value of the amount of refrigerant in the cooling circuit
12 corresponds to the predetermined operating amount of refrigerant
in the cooling circuit 12. When operation of the condenser 22a,
22b, 22c is ceased, residual refrigerant is supplied from the
refilling container 60 into the cooling circuit 12 only until
pressure equalization takes place between the refilling container
60 and the cooling circuit 12, i.e., until the pressure of the
refrigerant in the refilling container 60 corresponds to the
pressure of the refrigerant in the cooling circuit. As a result,
overfilling of the cooling circuit 12 with refrigerant is
avoided.
[0084] To avoid that the supply of residual refrigerant from the
refilling container 60 into the cooling circuit 12 until pressure
equalization takes place between the refilling container 60 and the
cooling circuit 12 causes an undesired pressure increase in the
cooling circuit 12, for example when the refrigerant in the
refilling container 60 has a high temperature due to high ambient
temperatures, the supply of refrigerant from the refilling
container 60 into the cooling circuit 12 is interrupted when a
pressure in the cooling circuit 12, which is measured by means of
the pressure sensors of the cooling system 10 has reached a
predetermined value. The interruption of the supply of refrigerant
from the refilling container 60 into the cooling circuit 12 in
dependence of the pressure in the cooling circuit 12 is achieved by
means of a pressure regulator incorporated in the refrigerant
connection 50a, 50b of the cooling system 10.
[0085] In case one of the chillers 27a, 27b, 27c or one of the
conveying devices 32a, 32b has to be dismounted from the cooling
circuit 12, for example for servicing purposes, the self-sealing
couplings connecting these components to the cooling circuit 12
prevent refrigerant from exiting the cooling circuit 12. If,
however, a component of the cooling system 10, which is not
connected to the cooling circuit 12 via self-sealing couplings,
should be dismounted from the cooling system 10, refrigerant is
discharged from the cooling circuit 12 or conveyed into one or both
of the hermetically sealable accumulators 34a, 34b. Refrigerant
received in the accumulators 34a, 34b does not have to be replaced,
but simply is maintained in the cooling circuit 12 of the cooling
system 10.
[0086] If, for example for safety reasons or for ease of the
dismounting procedure, it is decided to discharge the refrigerant
present in the cooling circuit 12 of the cooling system 10 from the
cooling circuit 12, the refrigerant may either be released to the
ambient or collected in the storage container 74 of the servicing
unit 52. For discharging refrigerant from the cooling circuit 12 of
the cooling system 10 the second refrigerant connection adaptor 68
is connected to a refrigerant connection 50a, 50b of the cooling
system 10. The nozzle of the second refrigerant connection adaptor
68 controls the flow of refrigerant from the cooling circuit 12
such that freezing of the refrigerant and hence icing of the nozzle
and/or further components of the cooling system 10 and/or the
servicing unit 52 is prevented.
[0087] In particular, the refrigerant is discharged from the
cooling circuit 12 of the cooling system 10 in its liquid state of
aggregation. For example, the refrigerant, after being liquefied,
may be conveyed from the storage containers 28a, 28a', 28b, 28b',
28c, 28c', 28d, 28d' to the refrigerant connections 50a, 50b of the
cooling system 10 by means of the conveying devices 32a, 32b. To
prevent a flow of refrigerant from the storage containers 28a,
28a', 28b, 28b', 28c, 28c', 28d, 28d' to the accumulators 34a, 34b,
and to enable a flow of refrigerant from the storage containers
28a, 28a', 28b, 28b', 28c, 28c', 28d, 28d' to the refrigerant
connections 50a, 50b, respective valves 37, 38, 42a, 42b, 51a, 51b
are suitably controlled, i.e., valves 37, 38, 42a, 42b, are closed,
whereas valves 51a, 51b are opened.
[0088] The refrigerant discharged from the cooling circuit 12 of
the cooling system 10 is stored in the storage container 74 of the
servicing unit 52 in it liquid state of aggregation and hence at a
relatively low pressure. If necessary, the refrigerant may be
liquefied by means of a condenser 64 of the servicing unit 52 prior
to being received in the storage container 74. Discharging the
refrigerant from the cooling circuit 12 of the cooling system 10 in
its liquid state of aggregation allows to compensate for pressure
differences between the cooling circuit 12, in particular the
accumulators 34a, 34b and the storage container 74 of the servicing
unit 52. In addition, the refrigerant experiences only a small
temperature decrease.
[0089] After discharging refrigerant from the cooling circuit 12
and prior to reintroducing refrigerant into the cooling circuit 12
so as to return the cooling system to a ready to operate state, the
cooling circuit 12 is evacuated by means of the evacuation device
70 of the servicing unit 60. Evacuation of the cooling circuit 12
allows residual air and humidity, which may affect operation of the
cooling system 10, to be removed from the cooling system 10 before
refrigerant is reintroduced into the cooling circuit 12. The
refrigerant reintroduced into the cooling circuit 12 may be the
refrigerant which is discharged from the cooling circuit 12 and
received in the storage container 74. It is, however, also
conceivable to supply the cooling system 10 entirely or partially
with "fresh" refrigerant which may be supplied to the storage
container 74 of the servicing unit.
[0090] Upon reintroducing refrigerant into the evacuated cooling
circuit 12, at least one of the condensers 22a, 22b, 22c of the
cooling system 10 is operated under the control of the control unit
52 so as to evaporate the refrigerant prior to entering the cooling
circuit 12 and to liquefy the gaseous refrigerant upon circulating
through the cooling circuit 12. The condenser 62 of the servicing
unit 52 is not operated so as to ensure unhindered evaporation of
the refrigerant contained in the storage container 74 of the
servicing unit 52. If necessary, the storage container 74 is heated
by means of the heating device 72 so as to support evaporation of
the refrigerant in the storage container 74. As an alternative, it
is, however, also possible to convey the refrigerant from the
storage container 74 into the cooling circuit 12 of the cooling
system 10 in its liquid state of aggregation by means of a
conveying device 66 of the servicing unit 52.
[0091] Basically, the cooling system 10 may comprise only the
accumulators 34a, 34b as described above, which may serve to store
liquid refrigerant exiting the condensers 22a, 22b, 22c and to
reduce the system pressure in the cooling circuit 12.
Alternatively, the accumulators 34a, 34b may be dispensed with, but
the cooling system 10 may be equipped with a storage container. In
such a cooling system 10 the storage container may fulfill the
double function of storing liquid refrigerant exiting the
condensers 22a, 22b, 22c and of reducing the system pressure in the
cooling circuit 12. It is, however, also conceivable to equip the
cooling system 10 with one or two accumulators 34a, 34b and an
additional storage container, wherein either both components or
only one of the accumulator(s) 34a, 34b and the storage container
may serve to store liquid refrigerant exiting the condensers 22a,
22b, 22c and to reduce the system pressure in the cooling circuit
12. Finally, a configuration of the cooling system 10 is
conceivable, wherein the at least one of the accumulators 34a, 34b
serves to collect and to store liquid refrigerant, whereas the
storage container, due to its additional volume, serves to reduce
the system pressure.
[0092] In case the functions "storing liquid refrigerant" and
"reducing system pressure" in the cooling system 10 are provided by
two separate components, these components may be installed at
different positions within the cooling circuit 12, allowing to more
efficiently use the available installation space and to limit the
size of the individual components of the cooling system 10.
However, as shown in FIG. 2, the pressure reducing storage
container 80a then preferably is installed in a high pressure
portion of the cooling circuit 12 in order to reliably prevent the
pressure in the high pressure portion of the cooling circuit 12
from exceeding a predetermined maximum value.
[0093] Further, in case the storage container 80a merely serves to
control the pressure in the cooling system 10, it is not necessary
to provide for a direct fluid connection between an accumulator
34a, 34b and the storage container. Instead, the storage container
80a may be connected to the cooling circuit 12 via only a single
line 82 or multiple lines 82a, branching off from the cooling
circuit 12, for example, upstream of the condensers 22a, 22b, 22c
and downstream of the evaporators 14a, 14b, 14c, 14d. The line 82
connecting the storage container 82a to the cooling circuit 12
preferably is connected to the storage container at a geodetic
lowest point 84 of the storage container 82a. This configuration
ensures that the storage container 82a is supplied only with
gaseous refrigerant which is discharged from the cooling circuit 12
due to the pressure in the cooling circuit 12 exceeding a
predetermined value. Of course, if desired, also more than one
storage container 82a, 82b may be provided in the cooling system
10, wherein each storage container may be connected to the cooling
circuit 12 via a line 82, 86 branching off from the cooling circuit
12 upstream of a condenser 22a, 22b, 22c and downstream of an
evaporator 14a, 14b, 14c, 14d.
[0094] As is apparent from the foregoing specification, the
invention is susceptible of being embodied with various alterations
and modifications which may differ particularly from those that
have been described in the preceding specification and description.
It should be understood that I wish to embody within the scope of
the patent warranted hereon all such modifications as reasonably
and properly come within the scope of my contribution to the
art.
* * * * *