U.S. patent application number 13/922013 was filed with the patent office on 2013-12-26 for aircraft comprising a cooling system for operation with a two-phase refrigerant.
The applicant listed for this patent is AIRBUS OPERATIONS GMBH. Invention is credited to Ahmet Kayihan Kiryaman, Markus PIESKER, Martin Sieme.
Application Number | 20130340470 13/922013 |
Document ID | / |
Family ID | 46331058 |
Filed Date | 2013-12-26 |
United States Patent
Application |
20130340470 |
Kind Code |
A1 |
PIESKER; Markus ; et
al. |
December 26, 2013 |
AIRCRAFT COMPRISING A COOLING SYSTEM FOR OPERATION WITH A TWO-PHASE
REFRIGERANT
Abstract
An aircraft includes a cooling system having a cooling circuit
to circulate a two-phase refrigerant therethrough, an evaporator
disposed in a first section of the cooling circuit and having a
refrigerant inlet and outlet, a condenser disposed in a second
section of the cooling circuit and having a refrigerant inlet and
outlet, a first cooling circuit control valve disposed in the
cooling circuit between the refrigerant outlet of the evaporator
and the refrigerant inlet of the condenser, and a second cooling
circuit control valve disposed in the cooling circuit between the
refrigerant outlet of the condenser and the refrigerant inlet of
the evaporator. The first and the second cooling circuit control
valves in their closed state seal the first section of the cooling
circuit from the second section of the cooling circuit. The second
section of the cooling circuit is installed in an unpressurized
region of the aircraft.
Inventors: |
PIESKER; Markus; (Hamburg,
DE) ; Sieme; Martin; (Hamburg, DE) ; Kiryaman;
Ahmet Kayihan; (Hamburg, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
AIRBUS OPERATIONS GMBH |
Hamburg |
|
DE |
|
|
Family ID: |
46331058 |
Appl. No.: |
13/922013 |
Filed: |
June 19, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61662368 |
Jun 21, 2012 |
|
|
|
Current U.S.
Class: |
62/515 |
Current CPC
Class: |
B64D 2013/0674 20130101;
F25B 39/02 20130101; Y02T 50/56 20130101; F25B 49/005 20130101;
B64D 13/06 20130101; Y02T 50/50 20130101 |
Class at
Publication: |
62/515 |
International
Class: |
F25B 49/00 20060101
F25B049/00; F25B 39/02 20060101 F25B039/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 21, 2012 |
EP |
12 172 981.8 |
Claims
1. Aircraft comprising a cooling system, wherein the cooling system
comprises: a cooling circuit allowing circulation of a two-phase
refrigerant therethrough, an evaporator disposed in a first section
of the cooling circuit and having a refrigerant inlet and a
refrigerant outlet, a condenser disposed in a second section of the
cooling circuit and having a refrigerant inlet and a refrigerant
outlet, a first cooling circuit control valve disposed in the
cooling circuit between the refrigerant outlet of the evaporator
and the refrigerant inlet of the condenser, and a second cooling
circuit control valve disposed in the cooling circuit between the
refrigerant outlet of the condenser and the refrigerant inlet of
the evaporator, the first and the second cooling circuit control
valve in their closed state being adapted to seal the first section
of the cooling circuit from the second section of the cooling
circuit, wherein the second section of the cooling circuit is
installed in an unpressurized region of the aircraft.
2. Aircraft according to claim 1, wherein the cooling system
further comprises at least one of: a first bleed valve arrangement
which in its open state is adapted to discharge refrigerant from
the first section of the cooling circuit to at least one of the
aircraft environment and an unpressurized region of the aircraft,
and a second bleed valve arrangement which in its open state is
adapted to discharge refrigerant from the second section of the
cooling circuit to at least one of the aircraft environment and an
unpressurized region of the aircraft.
3. Aircraft according to claim 1, wherein a control device of the
cooling system is configured to control at least one of the first
and the second cooling circuit control valve, the first bleed valve
arrangement and the second bleed valve arrangement in dependence on
at least one sensor signal supplied to the control device, the
sensor signal being indicative of at least one of a pressure of the
refrigerant in the cooling circuit of the cooling system, a
concentration of the refrigerant in the ambient air in a
pressurized region of the aircraft, an amount of refrigerant
present in the cooling circuit of the cooling system, a system
failure affecting proper operation of the cooling system, and a
predefined operating state of the aircraft.
4. Aircraft according to claim 1, wherein at least one component of
the cooling system which is installed in a pressurized region of
the aircraft comprises an encasement, the encasement being adapted
to receive refrigerant leaking from the least one component of the
cooling system.
5. Aircraft according to claim 1, wherein a control device of the
cooling system is configured to control the operation of the
cooling system upon system start-up such that refrigerant is
liquefied in the condenser while the first cooling circuit control
valve and the second cooling circuit control valve are closed so as
to separate the first section of the cooling circuit from the
second section of the cooling circuit until the amount of liquid
refrigerant is sufficient to allow a flooding of cooling system
components which are disposed in the cooling circuit downstream of
a conveying device for conveying refrigerant through the cooling
circuit with liquid refrigerant.
6. Aircraft according to claim 1, wherein a control device of the
cooling system is configured to control the supply of refrigerant
to the evaporator in dependence on the operational state of the
evaporator such that a dry evaporation of the refrigerant occurs in
the evaporator.
7. Aircraft according to claim 1, wherein a control device of the
cooling system is configured to control the operation of the
cooling system upon system shut-down such that the supply of
refrigerant to the evaporator is interrupted while liquefaction of
refrigerant in the condenser is continued until a pressure of the
refrigerant in the cooling system has reached a predetermined set
value.
8. Aircraft according to claim 7, wherein the predetermined set
value of the pressure of the refrigerant in the cooling system is
lower than a value of the pressure of the refrigerant in the
cooling system during normal operation of the cooling system.
9. Aircraft according to claim 7, wherein a control device of the
cooling system is configured to close the first and the second
cooling circuit control valve so as to separate the first section
of the cooling circuit from the second section of the cooling
circuit when the pressure of the refrigerant in the cooling system
has reached the predetermined set value.
10. Aircraft according to claims 1, wherein a control device of the
cooling system is configured to control the operation of the
cooling system upon system shut-down such that refrigerant which is
liquefied in the condenser is stored in an accumulator which is
installed in an unpressurized region of the aircraft.
11. Aircraft according to claim 1, wherein a pipe burst safety
valve is associated with each one of the first and the second
cooling circuit control valve.
12. Aircraft according to claim 1, wherein the cooling circuit
comprises two first sections which are at least partially installed
in a pressurized region of the aircraft, wherein an evaporator is
disposed in each of the two first sections, and wherein two first
cooling circuit control valves as well as two second cooling
circuit control valves in their closed state are adapted to seal
the two first sections of the cooling circuit from the second
section of the cooling circuit.
13. Aircraft according to claim 12, wherein a control device of the
cooling system is configured to control at least one of the two
first cooling circuit control valves and the two second cooling
circuit control valves in such a manner that only one of the two
first sections of the cooling circuit is connected to the second
section of the cooling circuit if the amount of refrigerant
circulating in the cooling circuit is not sufficient to satisfy the
demand of both first cooling circuit sections.
14. Aircraft according to claim 1, wherein the cooling system
further comprises a first additional cooling circuit control valve
connected in series with at least one of the first cooling circuit
control valve and a second additional cooling circuit control valve
connected in series with the second cooling circuit control valve,
and/or wherein at least one cooling system component which is
susceptible to pipe burst is disposed between a respective pair of
additional pipe burst valves.
15. Aircraft according to claim 1, wherein the cooling system
further comprises a bypass line bypassing the evaporator, wherein
at least one of a pressure relief valve and a control valve may be
adapted to control the refrigerant flow through the bypass line.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is entitled to and claims the benefit of
European Application No. 12 172 981.8 filed Jun. 21, 2012 and U.S.
Provisional Application No. 61/662,368, filed Jun. 21, 2012, the
disclosures of each of which, including the specification, claims,
drawings and abstract, are incorporated herein by reference in
their entirety.
FIELD
[0002] The invention relates to an aircraft comprising a cooling
system for operation with a two-phase refrigerant.
BACKGROUND
[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 have
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.
[0005] A cooling system for operation with a two-phase refrigerant
which is installed in an aircraft usually serves to provide cooling
energy to cooling energy consumers arranged in a cabin of the
aircraft. The two-phase refrigerant therefore has to be conveyed
into and through a region of the aircraft which is occupied with
passengers and crew members. Typical two-phase refrigerants for use
in aircraft cooling systems such as, for example, CO.sub.2 or R134A
(CH.sub.2F--CF.sub.3) evaporate when being subjected to the ambient
conditions prevailing in an aircraft cabin during normal operation
of the aircraft. A leakage of refrigerant from the cooling system,
for example due to a defect or a malfunctioning of the cooling
system, and in particular a leakage of the cooling system in the
region of the aircraft cabin is undesirable.
SUMMARY
[0006] The invention is directed to the object to provide an
aircraft equipped with a cooling system for operation with a
two-phase refrigerant which allows preventing refrigerant leaking
from the cooling system in the pressurized region of the aircraft.
This object is achieved by an aircraft having features of attached
claims.
[0007] In the context of the present application the term
"pressurized region" designates an aircraft region which during
flight may be pressurized so as to increase the pressure in said
aircraft region above the low pressure prevailing outside the
aircraft at high altitudes. The pressurized region of the aircraft
may comprise a cabin of the aircraft, the cabin including for
example a passenger cabin area, a cockpit, a crew rest compartment,
a freight compartment, etc. Of course, the aircraft region which
herein is designated as a pressurized region of the aircraft during
certain operational phases of the aircraft, for example during
ground operation or during flight at low altitudes may also be not
pressurized. To the contrary, the term "unpressurized region" in
the context of the present application designates an aircraft
region which also during flight at high altitudes is not
pressurized. The pressure prevailing in the pressurized region of
the aircraft thus during all operational phases of the aircraft
corresponds to the pressure prevailing outside the aircraft. The
unpressurized region of the aircraft may, for example, comprise a
belly fairing or a tail cone of the aircraft. The term "ambient
air" in the context of the present application designates the air
in the pressurized region of the aircraft.
[0008] An aircraft according to the invention comprises a cooling
system which is in particular suitable for cooling heat generating
components or food. The cooling system comprises a cooling circuit
allowing circulation of a two-phase refrigerant therethrough. The
two-phase refrigerant circulating in the cooling circuit 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
(CH.sub.2F--CF.sub.3). 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.
[0009] Preferably, however, CO.sub.2 is employed as the two-phase
refrigerant. Although not being non-hazardous to the health of
people staying in a cabin of the aircraft in the event of a leakage
of the cooling system, CO.sub.2 is at least substantially
environment-neutral. If desired, an odorant may be mixed to the
refrigerant so that refrigerant leaking from the cooling system due
to a defect or a malfunctioning of the cooling system may be
smelled by people being subjected to the refrigerant vapor.
[0010] An evaporator of the cooling system, which forms an
interface between the cooling circuit and a cooling energy
consumer, is disposed in a first section of the cooling circuit and
has a refrigerant inlet and a refrigerant outlet. The evaporator
may, for example, be a heat exchanger which provides for a thermal
coupling of the refrigerant flowing through the cooling circuit and
a fluid to be cooled, such as for example air to be supplied to
mobile transport containers for cooling food stored in the mobile
transport containers or any heat generating component on board the
aircraft. The two-phase refrigerant is supplied to the refrigerant
inlet of the evaporator in its liquid state of aggregation. Upon
releasing its cooling energy to the cooling energy consumer, the
refrigerant is evaporated and thus exits the evaporator at the
refrigerant outlet in its gaseous state of aggregation.
[0011] The cooling system further comprises a condenser, which is
disposed in a second section of the cooling circuit and has a
refrigerant inlet and a refrigerant outlet. The refrigerant which
is evaporated in the evaporator, via a portion of the cooling
circuit downstream of the evaporator and upstream of the condenser,
is supplied to the refrigerant inlet of the condenser in its
gaseous state of aggregation. In the condenser, the refrigerant is
condensed and hence exits the condenser at the refrigerant outlet
of the condenser in its liquid state of aggregation. The condenser
may be a part of a chiller or can be supplied with cooling energy
from a chiller. For example, the condenser may comprise a heat
exchanger which provides for a thermal coupling of the refrigerant
flowing through the cooling circuit and a cooling circuit of a
chiller.
[0012] Refrigerant condensed in the condenser may be immediately
directed back to the evaporator. It is, however, also conceivable
to provide the cooling system with at least one accumulator which
may be disposed in the second section of the cooling circuit
downstream of the condenser and thus can be supplied with liquid
refrigerant from the condenser. Suitable valves may be provided for
controlling the supply of refrigerant from the condenser to the
accumulator(s) and/or from the accumulator(s) to the evaporator.
Moreover, a super-cooler may be associated with the condenser which
serves to super-cool the liquid refrigerant and to thus prevent an
undesired evaporation of the refrigerant.
[0013] A first cooling circuit control valve is disposed in the
cooling circuit between the refrigerant outlet of the evaporator
and the refrigerant inlet of the condenser. Further, a second
cooling circuit control valve is disposed in the cooling circuit
between the refrigerant outlet of the condenser and the refrigerant
inlet of the evaporator. In their closed state, the first and the
second cooling circuit control valve are adapted to seal the first
section of the cooling circuit from the second section of the
cooling circuit. The second section of the cooling circuit together
with the cooling system components disposed in the second section
of the cooling circuit is installed in an unpressurized region of
the aircraft. For example, the second section of the cooling
circuit may be in installed in the tail cone or the belly fairing
of the aircraft.
[0014] The first section of the cooling circuit may also be
installed in an unpressurized region of the aircraft. In practice,
it is, however, preferable to install the first section of the
cooling circuit or at least some of the cooling system components
disposed in the first section of the cooling circuit in a
pressurized region, i.e. a cabin of the aircraft. For example, at
least the evaporator of the cooling system may be installed in the
aircraft cabin when said evaporator serves to provide cooling
energy to a cooling energy consumer which is also installed in the
aircraft cabin.
[0015] In the event of a leakage occurring in the cooling system,
by closing the first and the second cooling circuit control valve,
the first and the second section of the cooling circuit can be
sealed from each other. Hence, the maximum amount of refrigerant
exiting the cooling system in the event of a leakage of the cooling
system is reduced to the amount of refrigerant contained in the
section of the cooling circuit which is affected by the leakage,
i.e. either the first or the second section of the cooling circuit.
If desired, the cooling system may comprise more than two valves
which are adapted to seal selected areas of the cooling circuit
from each other so as to further reduce the maximum amount of
refrigerant exiting the cooling system in the event of a leakage of
the cooling system.
[0016] Further, the installation of the second section of the
cooling circuit including the cooling system components disposed in
said second cooling circuit section in an unpressurized region of
the aircraft enables refrigerant exiting from the cooling system
due to a leakage of the second section of the cooling circuit to be
vented to the environment without harming people staying in the
aircraft cabin, i.e. a pressurized region of the aircraft. In
particular cooling system components containing a large amount of
refrigerant, such as accumulators, storage containers and the like,
preferably should be disposed in the second section of the cooling
circuit and thus installed in an unpressurized region of the
aircraft so as to allow the refrigerant to be vented to the
environment in the event of a leakage of the second section of the
cooling circuit. The aircraft according to the invention thus
allows to considerably minimize the health risk for people staying
in the aircraft cabin due to a contamination of the ambient air in
the aircraft cabin with refrigerant leaking from the cooling
system, for example due to a defect or a malfunctioning of the
cooling system.
[0017] The cooling system employed in the aircraft according to the
invention may further comprise a first bleed valve arrangement
which in its open state is adapted to discharge refrigerant from
the first section of the cooling circuit to the aircraft
environment and/or to an unpressurized region of the aircraft.
Alternatively or additionally thereto, the cooling system may
comprise a second bleed valve arrangement which in its open state
is adapted to discharge refrigerant from the second section of the
cooling circuit to the aircraft environment and/or to an
unpressurized region of the aircraft.
[0018] By venting refrigerant from the cooling circuit of the
cooling system to the aircraft environment and/or to an
unpressurized region of the aircraft, the amount of refrigerant
which in the event of a defect or a malfunctioning of the cooling
system may enter the aircraft cabin and harm people staying in the
aircraft cabin can further be minimized. Further, by discharging
refrigerant from the cooling system to the aircraft environment
and/or to an unpressurized region of the aircraft, an uncontrolled
pressure increase in the cooling system or selected cooling system
components may be prevented which may otherwise result from liquid
refrigerant being enclosed in the first or the second section of
the cooling circuit as a result of the closing of the first and the
second cooling circuit control valve.
[0019] The cooling system may further comprise a control device
which is configured to control the first and/or the second cooling
circuit control valve, the first bleed valve arrangement and/or the
second bleed valve arrangement in dependence on at least one sensor
signal supplied to the control device. The sensor signal may for
example be indicative of a pressure of the refrigerant in the
cooling circuit of the cooling system. For example, a sudden
pressure drop occurring during normal operation of the cooling
system, by the control device, may be interpreted as indicative of
a leakage of the cooling system and, hence, cause the control
device to close the first and the second cooling circuit control
valve so as to seal the first and the second section of the cooling
system cooling circuit from each other. To the contrary, when the
first and the second cooling circuit control valve are closed, a
pressure increase in the first and/or the second section of the
cooling circuit above a predetermined threshold value may trigger
the control device to control the first bleed valve arrangement
and/or the second bleed valve arrangement in its/their open state
so as to discharge refrigerant from the first and/or the second
section of the cooling circuit.
[0020] Alternatively or additionally thereto, the control device
may be adapted to evaluate a sensor signal indicative of a
concentration of the refrigerant in the ambient air in a
pressurized region of the aircraft. For example, at least one
sensor for measuring the concentration of the refrigerant in the
ambient air may be installed in the aircraft cabin. This sensor may
be associated exclusively to the cooling system, but also may form
a part of the air quality monitoring system of an aircraft air
conditioning system. In case CO.sub.2 is employed in the cooling
system as the two-phase refrigerant, a sensor for measuring the
CO.sub.2 concentration in the ambient air in the aircraft cabin,
due to the specific weight of CO.sub.2 being higher than the
specific weight of air, preferably is placed close to the floor of
the aircraft cabin.
[0021] In case a concentration of the refrigerant in the ambient
air in the pressurized region of the aircraft exceeds a
predetermined threshold value, the control device may close the
first and the second cooling circuit control valve so as to seal
the first and the second section of the cooling system cooling
circuit from each other. Further, the control device may control
the first and/or the second bleed valve arrangement so as to allow
refrigerant to be vented from the cooling system. Additionally or
alternatively thereto, the control device may also be adapted to
output a visually or acoustically recognizable warning signal.
Further, the control device may be adapted to control an actuating
mechanism of an oxygen mask system of the aircraft. The actuating
mechanism may cause oxygen masks to drop from a ceiling of the
aircraft cabin so as to become accessible to the passengers and the
crew members staying in the aircraft cabin, if the refrigerant
concentration in the breathing air in the aircraft cabin exceeds a
predetermined threshold value.
[0022] The control device may further be adapted to evaluate a
sensor signal or a plurality of sensor signals indicative of an
amount of refrigerant present in the cooling circuit of the cooling
system. For example, the amount of refrigerant present in the
cooling circuit of the cooling system may be determined by
measuring the level of the refrigerant in an accumulator, the
pressure of the refrigerant, and the temperature of the
refrigerant. The amount of refrigerant present in the cooling
circuit of the cooling system may be determined continuously or at
specific time intervals. If desired, a first measurement upon
start-up of the system may be used as a reference measurement and
compared at least to a measurement performed during or after system
shut-down.
[0023] A considerable decrease of the amount of refrigerant in the
cooling circuit of the cooling system during operation of the
cooling system may be indicative of a leakage of the cooling
system. In case the refrigerant loss is low, the control device may
simply initiate shut-down of the operation of the cooling system.
In the event of a refrigerant leakage which may cause harm to
people on board the aircraft, the control device, however, may also
control the first and the second cooling circuit control valve so
as to seal the first and the second section of the cooling system
cooling circuit from each other and/or to discharge refrigerant
from the cooling system to the aircraft environment and/or to an
unpressurized region of the aircraft by means of the first and/or
the second bleed valve arrangement.
[0024] Moreover, the control device may be adapted to evaluate at
least one sensor signal indicative of a system failure affecting
proper operation of the cooling system. For example, the control
device may be adapted to close the first and the second cooling
circuit control valve so as to seal the first and the second
section of the cooling system cooling circuit from each other
and/or control the first and/or the second bleed valve arrangement
so as to discharge refrigerant from the cooling system cooling
circuit to the aircraft environment and/or to an unpressurized
region of the aircraft in the event of a power failure or a
malfunctioning of the condenser.
[0025] Finally, the control device may be adapted to evaluate at
least one sensor signal indicative of a predefined operating state
of the aircraft. The predefined operating state of the aircraft may
be an emergency operating state, for example prior to an intended
emergency landing or in case of a fire on board the aircraft. For
example, the control device may be adapted to close the first and
the second cooling circuit control valve so as to seal the first
and the second section of the cooling system cooling circuit from
each other and/or control the first and/or the second bleed valve
arrangement so as to discharge refrigerant from the cooling system
cooling circuit to the aircraft environment and/or to an
unpressurized region of the aircraft when an emergency operating
state of the aircraft is detected.
[0026] At least one component of the cooling system which is
installed in a pressurized region of the aircraft may comprise an
encasement. The encasement may be adapted to receive refrigerant
leaking from the at least one component of the cooling system. The
at least one component of the cooling system may, for example, be a
tubing, in particular a tubing forming a component of the first
section of the cooling circuit or the evaporator. The encasement
may be sealed against the environment so as to avoid refrigerant
leaking from the encased component to contaminate the ambient air
in the pressurized region of the aircraft. Preferably, the
encasement is connectible to the aircraft environment and/or an
unpressurized region of the aircraft so as to be able to vent
refrigerant from the encasement to the aircraft environment and/or
the unpressurized region of the aircraft. At least one sensor for
measuring the pressure and/or the concentration of the refrigerant
in the encasement may be provided. The signals of the at least one
sensor may be evaluated by the control unit for controlling the
first and/or the second cooling circuit control valve, the first
bleed valve arrangement and/or the second bleed valve
arrangement.
[0027] The installation of cooling system components in an
encasement preventing refrigerant leaking from the cooling system
components to enter a pressurized region of the aircraft allows to
significantly reduce the risk that people staying in a pressurized
region of the aircraft are harmed by a refrigerant contamination of
the breathing air in the pressurized region of the aircraft.
Further, in particular when at least one sensor for measuring the
pressure and/or the refrigerant concentration in the encasement is
present, localization of a leakage of the cooling system is
simplified. Encasements, however, undesirably add to the weight of
the cooling to system.
[0028] A control device of the cooling system preferably is
configured to control the operation of the cooling system upon
system start-up such that refrigerant is liquefied in the condenser
while the first cooling circuit control valve and the second
cooling circuit control valve are closed so as to separate the
first section of the cooling circuit from the second section of the
cooling circuit. In other words, the condenser is operated so as to
liquefy refrigerant while the refrigerant still is not conveyed to
the evaporator. The liquefaction of the refrigerant in the
condenser is continued until the amount of liquid refrigerant is
sufficient to allow a flooding of cooling system components which
are disposed in the cooling circuit downstream of a conveying
device for conveying refrigerant through the cooling circuit with
liquid refrigerant. The liquid refrigerant may be stored in an
accumulator.
[0029] Advantageously, the control device is configured to operate
the condenser during the start-up operational phase of the cooling
system at a low operating temperature, i.e. an operating
temperature that is lower than the operating temperature of the
condenser during normal operation of the cooling system, so as to
allow super-cooling of the liquid refrigerant. Alternatively or
additionally thereto, a separate super-cooler or a super-cooler
which is integrated into the condenser may be employed so as to
ensure the desired super-cooling of the refrigerant during the
start-up operational phase of the cooling system.
[0030] An operating state of the cooling system wherein the
condenser is operated so as liquefy refrigerant, although the
amount of liquid refrigerant present in the cooling circuit is
already sufficient to allow the desired flooding of cooling system
components, while the supply of refrigerant to the evaporator,
however, still is interrupted, in the following is designated as a
stand-by operational state of the cooling system. When the cooling
system is in the stand-by operational state, the desired flooding
of the cooling system components with liquid refrigerant and the
supply of liquid refrigerant to the evaporator may be initiated so
as to allow start of normal operation of the cooling system wherein
the cooling system provides cooling energy to at least one cooling
energy consumer. It is, however, also possible to simply cease
operation of the condenser of a cooling system operating in the
stand-by operational state so as to shut-down the cooling
system.
[0031] Preferably, a control device of the cooling system is
configured to control the operation of the cooling system in such a
way that the cooling system is operated in its stand-by operational
state as long as possible. Operation of the cooling system in the
stand-by operational state allows to immediately recognize
operational failures and, in particular, leakages of the system
which may not be noticed when the system is shut off. The
operational safety of the cooling system operated in its stand-by
operational state, however, still is particularly high, since the
supply of refrigerant to the first section of the cooling circuit
and thus into a pressurized region of the aircraft still is
interrupted.
[0032] System start-up until the stand-by operational state of the
cooling system is reached therefore may be initiated by the control
device, although there are still no cooling energy requirements
from cooling energy consumers supplied with cooling energy by the
cooling system during normal operation of the cooling system. For
example, initiating the start-up procedure of the cooling system
may be made subject of a checklist which is processed during a
flight preparation operational phase of the aircraft. The stand-by
operation of the cooling system may be terminated and normal
operation of the cooling system including operation of the
evaporator may be started as soon as cooling energy has to be
supplied to the cooling energy consumers provided with cooling
energy by the cooling system.
[0033] A control device of the cooling system may further be
configured to control the supply of refrigerant to the evaporator
during normal operation of the cooling system in dependence on the
operational state of the evaporator, i.e. the cooling energy
requirement of the cooling energy consumer coupled to the
evaporator, such that a dry evaporation of the refrigerant occurs
in the evaporator. This allows an operation of the cooling system
with a limited amount of refrigerant circulating in the cooling
circuit. As a result, the static pressure of the refrigerant
prevailing in the cooling circuit in the non-operating state of the
cooling system is low, even at high ambient temperatures. In
addition, the health risk for people staying in the aircraft cabin
due to a contamination of the ambient air in the aircraft cabin
with refrigerant leaking from the cooling system is further
reduced.
[0034] The supply of refrigerant to the evaporator may be is
controlled by suitably controlling a respective valve which is
disposed in the cooling circuit upstream of the evaporator. The
valve may comprise a nozzle for spraying the refrigerant into the
evaporator and to distribute the refrigerant within the evaporator.
The spraying of the refrigerant into the evaporator may be
achieved, for example, by supplying refrigerant vapor from the
evaporator to the nozzle of the valve and/or by evaporation of the
refrigerant due to a pressure decrease of the refrigerant
downstream of the valve.
[0035] To ensure occurrence of a dry evaporation in the evaporator,
a predetermined amount of refrigerant may be supplied to the
evaporator by appropriately controlling the valve. Then, a
temperature TK1 of the refrigerant at the refrigerant inlet of the
evaporator and a temperature TA2 of the fluid to be cooled by the
evaporator, for example air supplied to the cooling energy
consumer, may be measured, preferably while a fan conveying the
fluid to be cooled to the cooling energy consumer is running.
Further, the pressure of the refrigerant in the evaporator or at
the refrigerant outlet of the evaporator may be measured. If a
temperature difference between the temperature TA2 of the fluid to
be cooled by the evaporator and the temperature TK1 of the
refrigerant at the refrigerant inlet of the evaporator exceeds a
predetermined threshold value, for example 8K, and the pressure of
the refrigerant in the evaporator lies within a predetermined
range, the refrigerant supplied to the evaporator is thoroughly
evaporated and possibly also super-heated by the evaporator. Hence,
the valve again may be controlled so as to supply a further
predetermined amount of refrigerant to the evaporator.
[0036] A control device of the cooling system further may be
configured to control the operation of the cooling system upon
system shut-down such that the supply of refrigerant to the
evaporator is interrupted, while liquefaction of refrigerant in the
condenser is continued. During this operational phase of the
cooling system the first and the second cooling circuit control
valve, however, are still open such that the first and the second
section of the cooling circuit are still connected to each other.
The continued liquefaction of the refrigerant present in the
cooling system results in a pressure decrease in the cooling
circuit, and thus in an evaporation of residual liquid which may be
present, in particular, in the first section of the cooling
circuit. An evaporation of residual liquid present in the first
section of the cooling circuit and the removal of this refrigerant
from the first section of the cooling circuit allows to prevent
that this refrigerant evaporates when the cooling system is shut
off, for example due to high ambient temperatures, and causes the
built-up of an undesirable high pressure in the first section of
the cooling circuit.
[0037] Preferably, the control device is configured to operate the
condenser at a low operating temperature, i.e. an operating
temperature which is lower than the operating temperature of the
condenser during normal operation of the cooling system. A low
operating temperature of the condenser increases the pressure drop
occurring in the cooling system during the shut-down procedure and,
as a result, supports the evaporation of residual liquid present in
cooling circuit.
[0038] The operating temperature of the condenser and thus the
amount of refrigerant which may be liquefied in the condenser,
however, is limited by the design of the condenser and the
thermodynamic properties of the refrigerant. Further, the pressure
of the refrigerant in the cooling system or at specific locations
in the cooling system may be measured with a higher accuracy than
the temperature of the refrigerant in the cooling system or at
specific locations in the cooling system. Therefore, the control
device is configured to use the pressure of the refrigerant in the
cooling system or at specific locations in the cooling system as a
control parameter for controlling the operation of the cooling
system, in particular the operation of the condenser and the
operation of control valves which control the flow of refrigerant
through the cooling circuit. Specifically, the control device may
be configured to continue the shut-down procedure involving an
interruption of the supply of refrigerant to the evaporator and a
continued liquefaction of refrigerant in the condenser until a
pressure of the refrigerant in the cooling system which may be
measured at different locations in the cooling system or at a
specific location in the cooling system has reached a predetermined
set value.
[0039] The predetermined set value of the pressure of the
refrigerant in the cooling system preferably is lower than a value
of the pressure of the refrigerant in the cooling system during
normal operation of the cooling system. By continuing the shut-down
procedure until the pressure of the refrigerant in the cooling
system is lower than during normal operation of the cooling system,
the desired evaporation of residual liquid refrigerant as described
above is ensured.
[0040] A control device of the cooling system preferably further is
configured to close the first and the second cooling circuit
control valves so as to separate the first section of the cooling
circuit from the second section of the cooling circuit when the
pressure of the refrigerant in the cooling system has reached the
predetermine set value. In this operational state of the cooling
system, an essential amount of refrigerant present in the cooling
system is liquefied, i.e. only a small amount of refrigerant
remains in the first section of the cooling circuit. Hence, in the
event of a leakage of the cooling system in the region of the first
section of the cooling circuit, only a small amount of refrigerant
will enter the pressurized region of the aircraft. When the first
and the second cooling circuit control valve are closed, operation
of the cooling system in its standby operational state may be
continued, i.e. liquefaction of the refrigerant in the condenser
may be continued, although the first and the second section of the
cooling circuit are sealed from each other. It is, however, also
possible to completely shut off the cooling system, i.e. to also
cease the operation of the condenser.
[0041] A control device of the cooling system preferably is
configured to control the operation of the cooling system upon
system shut-down such that refrigerant which is liquefied in the
condenser is stored in an accumulator which is installed in an
unpressurized region of the aircraft. As a result, after complete
shut off of the cooling system, the major part of the refrigerant
present in the cooling system is stored outside of the pressurized
region of the aircraft, i.e. the aircraft cabin. This ensures that
in the event of a leakage, the major part of refrigerant present in
the cooling system may be discharged to the unpressurized region of
the aircraft and finally the aircraft environment without harming
people staying in the pressurized region of the aircraft.
[0042] The control functions performed during operation of the
cooling system as described above may be carried out be a single
control unit, for example a central control unit of the cooling
system. It is, however, also conceivable to equip the cooling
system with a plurality of control units, each of which carries out
only selected control tasks.
[0043] A pipe burst safety valve may be associated with each one of
the first and the second cooling circuit control valve. A pipe
burst safety valve associated with the first cooling circuit
control valve may be arranged in the cooling circuit upstream of
the first cooling circuit control valve. A pipe burst safety valve
associated with the second cooling circuit control valve may be
arranged in the cooling circuit downstream of the second cooling
circuit control valve. In case a pipe bust should occur in the
tubing of the cooling circuit, in particular in the tubing of the
first section of the cooling circuit, the pipe burst safety valves
immediately close such that the amount of refrigerant exiting the
cooling system due to the pipe burst is limited.
[0044] The cooling circuit of the cooling system may comprise at
least two first sections which are formed separate from each other
and which may be sealed from each other. Preferably, the two first
sections are at least partially installed in a pressurized region
of the aircraft. An evaporator may be disposed in each of the two
first cooling circuit sections. For example, at least the
evaporators may be installed in a pressurized region of the
aircraft. The evaporators disposed in the two first cooling circuit
sections may be operated independently from each other, i.e. it is
possible to operate an evaporator disposed in one first cooling
circuit section, but not to operate an evaporator disposed in the
other first cooling circuit section. This allows a particularly
energy efficient operation of the cooling system in case only
selected cooling energy consumers associated with selected
evaporators require the supply of cooling energy. Further, the
system operational reliability of a cooling system comprising two
first cooling circuit sections is improved, since in case of an
operational failure caused by a lack of refrigerant in the cooling
circuit, for example due to a leakage of the cooling system, it may
still be possible to operate at least one of two first cooling
circuit sections. It is, of course, also conceivable to provide the
cooling system with more than two first cooling circuit
sections.
[0045] A control device of the cooling system may be configured to
control the two first cooling circuit control valves and/or the two
second cooling circuit control valves in such a manner that only
one of the two first sections of the cooling circuit is connected
to the second section of the cooling circuit if the amount of
refrigerant circulating in the cooling circuit is not sufficient to
satisfy the demand of both first cooling circuit sections. Such a
control of the cooling system prevents that a lack of refrigerant
circulating in the cooling circuit, i.e. a lack of cooling energy
produced by the cooling system, leads to a sudden failure of the
entire system. Instead, the cooling energy produced by the cooling
system is directed to a selected one of the two first cooling
circuit sections so as to at least supply of cooling energy to said
selected one of the two first cooling circuit sections.
[0046] Two first cooling circuit control valves as well as two
second cooling circuit control valves may be provided and, in their
closed state, may be adapted to seal the two first section of the
cooling circuit from the second section of the cooling circuit,
preferably independently from each other. This allows to further
reduce the amount of refrigerant exiting the cooling system and
entering a pressurized aircraft region in the event of a leakage of
the cooling system. In addition, localization of a cooling system
leakage may be simplified by the possibility to independently seal
two first cooling circuit sections from the second cooling circuit
section.
[0047] The cooling system may further comprise a first additional
cooling circuit control valve connected in series with the first
cooling circuit control valve. Alternatively or additionally
thereto, the cooling system may further comprise a second
additional cooling circuit control valve connected in series with
the second cooling circuit control valve. Two cooling circuit
control valves connected in series improve system redundancy in
case of a failure of one of the cooling circuit control valves. In
a cooling system comprising two first cooling circuit sections,
cooling circuit control valves connected in series may be employed
to seal either both or only one of the two first cooling circuit
sections from the second cooling circuit section.
[0048] At least one cooling system component which is susceptible
to pipe burst, for example the evaporator, may be disposed between
a respective pair of additional pipe burst valves so as to increase
the operational safety of the cooling system 10.
[0049] The cooling system may further comprises a bypass line
bypassing the evaporator. A pressure relief valve and/or a control
valve may be adapted to control the refrigerant flow through the
bypass line.
BRIEF DESCRIPTION OF DRAWINGS
[0050] Preferred embodiments of the invention now are described in
more detail with reference to the enclosed schematic drawings,
wherein
[0051] FIG. 1 depicts an overview over a first embodiment of an
aircraft cooling system suitable for operation with a two-phase
refrigerant,
[0052] FIG. 2 depicts an overview over a second embodiment of an
aircraft cooling system suitable for operation with a two-phase
refrigerant,
[0053] FIG. 3 depicts an overview over a third embodiment of an
aircraft cooling system suitable for operation with a two-phase
refrigerant,
[0054] FIG. 4 depicts an overview over a fourth embodiment of an
aircraft cooling system suitable for operation with a two-phase
refrigerant,
[0055] FIG. 5 depicts an overview over a fifth embodiment of an
aircraft cooling system suitable for operation with a two-phase
refrigerant, and
[0056] FIG. 6 depicts an alternative cooling circuit control valve
arrangement which may be employed in the cooling system of FIG.
5.
DETAILED DESCRIPTION
[0057] FIG. 1 depicts 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 CO.sub.2
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.
[0058] Further, the cooling system 10 comprises a first and a
second condenser 22a, 22b. Each condenser 22a, 22b has two
refrigerant inlets 24a, 24a, 24b, 24b' and a refrigerant outlet
26a, 26b. 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, is supplied to the refrigerant inlets 24a,
24a', 24b, 24b' of the condensers 22a, 22b in its gaseous state of
aggregation. The condensers 22a, 22b are thermally coupled to a
chiller (not shown in FIG. 1). The cooling energy provided by the
chiller in the condensers 22a, 22b is used to condense the
refrigerant. Thus, the refrigerant exits the condensers 22a, 22b at
the refrigerant outlets 26a, 26b of the condensers 22a, 22b in its
liquid state of aggregation.
[0059] The condensers 22a, 22b may be tube bundle heat exchangers.
Tube bundle heat exchangers are robust and may be provided with a
receiving space for buffering liquefied refrigerant when the
condensers 22a, 22b during operation of the cooling system 10 are
at least partially flooded to super-cool the liquefied refrigerant.
It is, however, also conceivable to design the condensers 22a, 22b
as plate heat exchangers, in particular if a separate super-cooler
for super-cooling the liquefied refrigerant is associated with at
least one of the condensers 22a, 22b.
[0060] Refrigerant circulating in the cooling circuit 12 may be
directly supplied to each one of the condensers 22a, 22b. The
condensers 22a, 22b, however, are connected in series such that
refrigerant exiting the condenser 22a is directed through the
condenser 22b so as to ensure sufficient super-cooling of the
refrigerant. An accumulator 28 is connected to a refrigerant inlet
24a', 24b' of each one of the condensers 22a, 22b, wherein the
supply of refrigerant from the accumulator 28 to the condensers
22a, 22b is controlled by means of a valve 30. Further, the
refrigerant outlets 26a, 26b of the condensers 22a, 22b are
connected to the accumulator 28 allowing refrigerant liquefied in
the condensers 22a, 22b to be supplied into the accumulator. The
supply of refrigerant from the condensers 22a, 22b to the
accumulator 28 is controlled by means of a valve 32.
[0061] The accumulator 28 comprises an adaptor connector 33 having
a pressure regulating function via which refrigerant may be
introduced into the cooling system 10 or discharged from the
cooling system 10, for example during maintenance of the cooling
system 10. A conveying device 34, which is embodied in the form of
a pump, serves to convey the refrigerant through the cooling
circuit. If desired, an air vessel (not shown in FIG. 1) may be
provided in the cooling circuit 12 downstream of the conveying
device 34 so as to dampen pressure surges resulting from the
operation of the conveying device 34 or the cooling system valves.
Specifically, the air vessel may be arranged in the cooling circuit
12 in a manner that it is not possible to flood the air vessel with
liquid refrigerant so as to ensure that the air vessel contains a
sufficient amount of gas during all operational phases of the
cooling system 10.
[0062] The accumulator 33 is installed above the condensers 22a,
22b and the conveying device 34 is installed below the condensers
22a, 22b. Hence, the conveying device 34 is arranged relative to
the accumulator 33 and the condensers 22a, 22b in such a position
that for the conveying device 34 a positive minimum inflow level,
which is defined by the level of a liquid column above an inflow
edge of a blade of the conveying device 34, is maintained. The
gravity of the liquid column causes a defined pressure increase in
the refrigerant supplied to the conveying device 34 thus providing
for a super-cooling of the refrigerant and thereby preventing
evaporation of the refrigerant due to the pressure reduction caused
by the conveying device 34. Consequently, cavitation of the
conveying device 34 is avoided.
[0063] A first cooling circuit control valve 36 is disposed in the
cooling circuit 12 downstream of the evaporators 14a, 14b, 14c, 14d
and upstream of the condensers 22a, 22b. A second cooling circuit
control valve 38 is disposed in the cooling circuit 12 upstream of
the evaporators 14a, 14b, 14c, 14d and downstream of the condensers
22a, 22b. In their closed state, the first and the second cooling
circuit control valves 36, 38 seal a first section 12a of the
cooling circuit 12 from a second section 12b of the cooling circuit
12b. The dash-dotted line in FIG. 1 indicates the boundary between
the first and the second section 12a, 12b of the cooling circuit
12. The second section 12b of the cooling circuit 12, together with
the cooling system components disposed in the second section 12b of
the cooling circuit 12, is installed in an unpressurized region 40
of the aircraft. For example, the second section 12b of the cooling
circuit 12 may be in installed in the tail cone or the belly
fairing of the aircraft. The unpressurized region 40 of the
aircraft is connected to the aircraft environment, for example by
louvers or suitable vent openings.
[0064] The first section 12a of the cooling circuit 12 is at least
partially installed in a pressurized region, i.e. a cabin 42 of the
aircraft. In particular, the evaporators 14a, 14b, 14c, 14d, tubing
portions employed in the cooling circuit 12 and the valves 20a,
20b, 20c, 20d are installed in the aircraft cabin 42.
[0065] The cooling system 10 further comprises a first pressure
relief valve 44 which, via a connecting line 48 is connected to the
cooling circuit 12 downstream of the first cooling circuit control
valve 36 and a second pressure relief valve 46 which is connected
to the accumulator 38. The first pressure relief valve 44 thus is
associated with the first section 12a of the cooling circuit 12,
while the second pressure relief valve 46 is associated with the
second section 12b of the cooling circuit 12. Both pressure relief
valves 44, 46 are designed as mechanically actuatable valves which
automatically open in case a pressure difference acting on the
valves 44, 46 exceeds a threshold value which is determined by the
design of the valves 44, 46. It is, however, also conceivable to
design the pressure relief valves 44, 46 in the form of burst discs
or bust discs may be provided in addition to the pressure relief
valves 44, 46.
[0066] The pressure relief valves 44, 46 thus prevent a pressure in
the cooling system 10 to exceed a desired threshold value
independent of the operational state of the cooling system 10. It
should be noted that the first pressure relief valve 44, although
being associated with the first section 12a of the cooling circuit
12 is installed in the unpressurized region 40 of the aircraft.
Thus, in the event of an undesired pressure increase in the first
section 12a of the cooling circuit 12, the refrigerant present in
the first section 12a of the cooling circuit 12, via the first
pressure relief valve 44, is discharged into the unpressurized
region 40 of the aircraft, where it does not harm people staying in
the aircraft cabin 42. Further, the first pressure relief valve 44
acts as a safety valve for the conveying device 34, for example in
case of a control failure resulting in an undesired increase of the
pressure in the conveying device 34. The first pressure relief
valve 44 thus aids to prevent a leakage and/or damage of the
conveying device 34.
[0067] In the cooling system 10 of FIG. 1 the arrangement of the
second pressure relief valve 46 close to the accumulator 38 is
advantageous, since the accumulator 38 forms an interface between a
plurality of cooling system components. Further, the volume of the
accumulator 38 allows to dampen pressure variations occurring in
the cooling circuit 12. It is, however, also conceivable to install
the second pressure relief valve 46 in the aircraft outer skin such
that refrigerant discharged from the cooling system 10 via the
second pressure relief valve 46 is vented directly to the aircraft
environment. A second pressure relief valve 46 installed in the
aircraft outer skin may be closed by means of a plug arranged flush
with the aircraft outer skin. Absence of the plug then immediately
indicates that the second pressure relief valve 46 has been
opened.
[0068] The cooling system 10 further is provided with a bleed valve
arrangement 50 which in its open state serves to discharge
refrigerant from the second section 12b of the cooling circuit 12
to the unpressurized region 40 of the aircraft. In the cooling
system 10 of FIG. 1 the bleed valve arrangement 50 is formed by an
electrically actuatable safety valve which is connected to the
accumulator 28. 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.
[0069] As becomes apparent from FIG. 1, the evaporator 14d is
received within an encasement 54 which is adapted to receive
refrigerant leaking from the evaporator 14d. The encasement 54 is
sealed against the environment so as to avoid refrigerant leaking
from the evaporator 14d to contaminate the ambient air in the cabin
42 of the aircraft. The encasement 54, however, via a line 56 is
connected to the unpressurized region 40 of the aircraft. A control
valve 58 is disposed in the line 56 and serves to either open the
interior of the encasement 54 to the unpressurized region 40 of the
aircraft or to seal the interior of the encasement 54 from the
unpressurized region 40 of the aircraft.
[0070] 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 refrigerant is
liquefied in the condensers 22a, 22b, while the first cooling
circuit control valve 36 and the second cooling circuit control
valve 38 are closed so as to separate the first section 12a of the
cooling circuit 12 from the second section 12b of the cooling
circuit 12. Further, under the control of the control unit 52, the
valves 20a,20b, 20c, 20d and 30 are closed, while valve 32 is open.
The condensers 22a, 22b are operated until the condensers 22a, 22b
are at least partially flooded resulting in a super-cooling of the
refrigerant. Specifically, the condensers 22a, 22b are operated at
a low operating temperature, i.e. an operating temperature that is
lower than the operating temperature of the condensers 22a, 22b
during normal operation of the cooling system so as to support
super-cooling of the refrigerant. Due to the conveying device 34
being arranged below the condensers 22a, 22b the flooding of the
condensers 22a, 22b entails that also the conveying device 34 is
flooded. Further, since the conveying device 34 is flooded before
operation of the conveying device 34 is started, it is not
necessary that the conveying device 34 is designed in the form of a
self-sucking pump.
[0071] When the level of the liquid refrigerant in the conveying
device 34 has reached a level which ensures that dry operation of
the conveying device 34 is avoided, operation of the conveying
device 34 is started. In particular, the operation of the conveying
device 34 is started in dependence on a signal indicative of the
level of the liquid refrigerant being supplied to the control unit
52. The level of liquid refrigerant may be measured in the
condensers 22a, 22b, in the conveying device 34 or downstream of
the conveying device 34. Any suitable procedure for measuring the
level of the liquid refrigerant may be employed. For example, the
level of the liquid refrigerant may be measured using a float gauge
or by detecting a physical parameter such as the electrical
connectivity or the heat conductivity of the refrigerant. Further,
inductive, piezoelectric or ultrasonic measurements may be
performed. Finally, it is also conceivable to determine the volume
of refrigerant which is already liquefied by means of the
condensers 22a, 22b based on a measurement of the pressure
difference in the cooling system 10 and the development of the
system pressure after starting operation of the condensers 22a,
22b.
[0072] When operation of the conveying device 34 is started, the
conveying device 34 is operated with a low speed. If desired, the
conveying device 34 may be adapted to be operated with a
continuously varying speed. It might, however, also be sufficient
to set three fixed speeds at which the conveying device 34 may be
operated. In this case, the conveying device 34 during a start-up
of the cooling system 10 is operated at the lowest speed.
[0073] The conveying device 34 conveys refrigerant liquefied in the
condensers 22a, 22b into the accumulator 28. This operation is
continued until the amount of liquid refrigerant present in the
cooling circuit 12 and stored in the accumulator 28 is sufficient
to allow that cooling system components which are disposed
downstream of the conveying device 34, i.e. the tubing of the
cooling circuit 12 and the evaporators 14a, 14b, 14c, 14d can be
flooded with liquid refrigerant. The fill level of the liquid
refrigerant in the accumulator 28 is measured so as to determine
whether enough liquid refrigerant is present to allow the desired
flooding of the cooling system components. Further, based on these
fill level measurements and based on measurements of the pressure
and the temperature of the refrigerant in the cooling system 10,
the total amount of refrigerant in the cooling system 10 may be
determined.
[0074] An operating state of the cooling system 10 wherein the
condensers 22a, 22b 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.
[0075] 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 first and the second cooling circuit control valves 36, 38 are
opened so as to connect the first section 12a of the cooling
circuit 12 to the second section 12b of the cooling circuit 12 and
to provide for a pressure equalization between the first and the
second section 12a, 12b of the cooling circuit 12. Thereafter,
valve 30 is opened such that liquid refrigerant gravity-driven is
supplied from the accumulator 28 to the condensers 22a, 22b and
further to the components of the cooling system 10 arranged
downstream of the condensers 22a, 22b. Upon flowing through the
condensers 22a, 22b the refrigerant is super-cooled. Operation of
the conveying device 34 is continued.
[0076] 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, valve 32 is closed such
that refrigerant exiting the condensers 22a, 22b is exclusively
conveyed to the evaporators 14a, 14b, 14c, 14d. During further
normal operation of the cooling system 10, valve 32 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 device 34. Specifically, the operating speed of
the conveying device 34 is increased when the cooling requirement
of the cooling energy consumers supplied with cooling energy by the
evaporators 14a, 14b, 14c, 14d increases.
[0077] During normal operation of the cooling system 10, the second
section 12b of the cooling circuit 12 may be considered as a
thermodynamically closed system, wherein the refrigerant is in the
state of a wet vapor as soon as the first drop of the refrigerant
is condensed. Liquefaction of the refrigerant in this closed system
substantially follows the isochores, wherein a pressure drop in the
second section 12b of the cooling circuit 12 is limited by
operating the condensers 22a, 22b at a low temperature. The
evaporators 14a, 14b, 14c, 14d should be operated at an evaporation
temperature of approximately -5.degree. C. The associated pressure
in the wet vapor region is approximately 30.5 bar.
[0078] 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 first cooling circuit control
valve 36 such that the pressure in the cooling circuit 12
downstream of the evaporators 14a, 14b, 14c, 14d and upstream of
the condensers 22a, 22b is higher than downstream of the condensers
22a, 22b and upstream of the evaporators 14a, 14b, 14c, 14d.
Specifically, the first cooling circuit control valve 36 is
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.
[0079] 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.
[0080] To shut-down the cooling system 10, the control device 52
controls the operation of the cooling system 10 such that the
supply of refrigerant to the evaporators 14a, 14b, 14c, 14d is
interrupted, while liquefaction of refrigerant in the condensers
22a, 22b is continued. Liquid refrigerant exiting the condensers
22a, 22b is conveyed into the accumulator 28 through open valve 32.
During this operational phase of the cooling system 10 the first
and the second cooling circuit control valve 36, 38, however, are
still open such that the first and the second section 12a, 12b of
the cooling circuit 12 are still connected to each other. The
continued liquefaction of the refrigerant present in the cooling
system 10 results in a pressure decrease in the cooling circuit 12,
and thus in an evaporation of residual liquid which may be present,
in particular, in the first section 12a of the cooling circuit
12.
[0081] Specifically, the control device 52 controls the condensers
22a, 22b so as to operate at a low operating temperature, i.e. an
operating temperature which is lower than the operating temperature
of the condensers 22a, 22b during normal operation of the cooling
system 10. A low operating temperature of the condenser increases
the pressure drop occurring in the cooling system 10 during the
shut-down procedure and, as a result, supports the evaporation of
residual liquid present in cooling circuit 12.
[0082] The control device 52 uses the pressure of the refrigerant
in the cooling system 10 or as a control parameter for controlling
the operation of the cooling system 10. In particular, the control
device 52 continues the shut-down procedure involving an
interruption of the supply of refrigerant to the evaporators 14a,
14b, 14c, 14d and a continued liquefaction of refrigerant in the
condensers 22a, 22b until a pressure of the refrigerant in the
cooling system 12 which may be measured at different locations in
the cooling system 12 or at a specific location in the cooling
system 12 has reached a predetermined set value. The predetermined
set value of the pressure of the refrigerant in the cooling system
12 is lower than a value of the pressure of the refrigerant in the
cooling system 12 during normal operation of the cooling system
[0083] When the pressure of the refrigerant in the cooling system
12 has reached the predetermine set value, the control device 52
closes the first and the second cooling circuit control valves 36,
38 so as to separate the first section 12a of the cooling circuit
12 from the second section 12b of the cooling circuit 12. In this
operational state of the cooling system 10, an essential amount of
refrigerant present in the cooling system is liquefied, i.e. only a
small amount of refrigerant remains in the first section 12a of the
cooling circuit 12. The major part of the refrigerant present in
the cooling system 12 is stored in the accumulator 28 which is
installed outside of the aircraft cabin 42 in the unpressurized
region 40 of the aircraft. The cooling system 10 may be completely
shut off by finally ceasing operation of the condensers 22a,
22b.
[0084] Further, at least one of the valves 20a, 20b, 20c, 20d may
again be opened so as to avoid that the portion of the cooling
circuit 12 between the first cooling circuit control valve 36 and
the valves 20a, 20b, 20c, 20d is sealed from the first pressure
relief valve 44. By opening at least one of the valves 20a, 20b,
20c, 20d the portion of the cooling circuit 12 between the first
cooling circuit control valve 36 and the valves 20a, 20b, 20c, 20d
may be protected against excess pressure, since refrigerant may be
discharged from the portion of the cooling circuit 12 between the
first cooling circuit control valve 36 and the valves 20a, 20b,
20c, 20d via the first pressure relief valve 44.
[0085] When a leakage occurs in the cooling system 10 while the
system 10 is shut off, the amount of refrigerant which may exit the
cooling system 10 and contaminate the ambient air in the aircraft
cabin 42 is limited to the small amount of refrigerant prevailing
in the first section 12a of the cooling circuit 12 after system
shut-down. In case a leakage occurs in the cooling system 10 during
normal system operation, the control device 52 closes the first and
the second cooling circuit control valve 36, 38 so as to seal the
first and the second section 12a, 12b of the cooling system cooling
circuit 12 from each other. The amount of refrigerant which may
exit the cooling system 10 and contaminate the ambient air in the
aircraft cabin 42 then again is limited to the amount of
refrigerant present in the first section 12a of the cooling circuit
12. In addition, the control device 52 opens the bleed valve
arrangement 50 so as to discharge refrigerant from the second
section 12b of the cooling circuit 12 into the unpressurized region
40 of the aircraft and to thus minimize the overall amount of
refrigerant present in the cooling system 10.
[0086] The control unit 52 may control the operation of the first
and the second cooling circuit control valve 36, 38 and the bleed
valve arrangement 50 in dependence on various sensor signals
supplied to the control unit 52. The sensor signals supplied to the
control unit 52 may be indicative of a pressure of the refrigerant
in the cooling circuit 12 of the cooling system 10, the
concentration of the refrigerant in the ambient air in the aircraft
cabin 42, an amount of refrigerant present in the cooling circuit
12 of the cooling system 10 and a system failure affecting proper
operation of the cooling system. Further, the control unit 52 may
close the first and the second cooling circuit control valve 36, 38
and/or open the bleed valve arrangement 50 in dependence on a
sensor signal indicative of a predefined operating state of the
aircraft, in particular an emergency operating state. For example,
the control unit 52 may initiate that the refrigerant is discharged
from the cooling system 10 when an emergency landing of the
aircraft is intended or in case of a fire on board the
aircraft.
[0087] In case a leakage occurs in the evaporator 14d, the
refrigerant exiting the evaporator 14d is received within the
encasement 54. This refrigerant may be discharged to the
unpressurized region 40 of the aircraft via line 56 by opening
valve 58. In particular, the control unit 52 opens valve 58 in
dependence on a sensor signal indicative of a pressure in the
encasement 54 or a refrigerant concentration in the encasement
54.
[0088] The cooling system 10 according to FIG. 2 differs from the
arrangement of FIG. 1 in that a storage container 60a, 60b is
arranged downstream and below each one of the condensers 22a, 22b.
The storage containers 60a, 60b, which may also be formed integral
with the condensers 22a, 22b are connected to a further accumulator
62 which is arranged downstream and below the storage containers
60a, 60b. Liquid refrigerant may be conveyed gravity-driven from
the accumulator 28 and the storage containers 60a, 60b into the
further accumulator 62. Valve 30 present in the arrangement of FIG.
1 is dispensed with. The storage containers 60a, 60b and the
accumulators 28, 62 are dimensioned so as to be able to receive the
entire amount of refrigerant present in the cooling system 10 in
its liquid state of aggregation. Thus, during system start-up and
during stand-by operation of the cooling system, the condensers
22a, 22b may be operated so as to liquefy refrigerant without it
being necessary to operate the conveying device 34.
[0089] The cooling system 10 further comprises two super-coolers
64a, 64b which are arranged in series in the cooling circuit 12
downstream of the further accumulator 62. The conveying device 34
is installed above the storage containers 60a, 60b and the further
accumulator 62 and therefore is designed in the form of a
self-sucking pump. Further, the conveying device 34 no longer is
disposed upstream, but instead downstream of the second cooling
circuit control valve 38. In other words, the conveying device 34
no longer is disposed in the second section 12b of cooling circuit
12, but in the first section 12a of the cooling circuit 12.
Therefore the conveying device 34 is less susceptible to leakages
and also may be designed so as to be less pressure resistant than
in the arrangement of FIG. 1. Finally, valve 32 is designed in the
form of a mechanically actuated pressure relief valve.
[0090] Otherwise, the structure and the operating principle of the
cooling system 10 according to FIG. 2 correspond to the structure
and the operating principle of the arrangement of FIG. 1.
[0091] The cooling system 10 according to FIG. 3 differs from the
arrangement of FIG. 2 in that the conveying device 34, like in the
arrangement according to FIG. 1, again is disposed upstream of the
second cooling circuit control valve 38 and thus arranged in the
second section 12b of cooling circuit 12. Further, each one of the
first and the second cooling circuit control valve 36, 38 is
associated with an additional pipe burst safety valve 66a, 66b. The
pipe burst safety valve 66a associated with the first cooling
circuit control valve 36 is arranged upstream of the first cooling
circuit control valve 36. The pipe burst safety valve 66b
associated with the second cooling circuit control valve 38 is
arranged downstream of the second cooling circuit control valve 38.
In case a pipe bust should occur in the tubing of the cooling
circuit 12, in particular in the tubing of the first section 12a of
the cooling circuit 12, the pipe burst safety valves 66a, 66b
immediately close such that the amount of refrigerant exiting the
cooling system 10 due to the pipe burst is limited.
[0092] The cooling system 10 of FIG. 3 further comprises an
additional pressure relief valve 68 disposed in the cooling circuit
12 between the evaporators 14a, 14b, 14c, 14d and the first cooling
circuit control valve 36. Like the pressure relief valves 44, 46,
the additional pressure relief valve 68 is designed as mechanically
actuatable valve which automatically opens in case a pressure
difference acting on the valve 68 exceeds a threshold value which
is determined by the design of the valve 68. Due to the presence of
the additional pressure relief valve 68 it is no longer necessary
to maintain at least one of the valves 20a, 20b, 20c, 20d open when
the system 10 is shut off so as to prevent built-up of an excess
pressure in the portion of the cooling circuit 12 between the
evaporators 14a, 14b, 14c, 14d and the first cooling circuit
control valve 36.
[0093] Finally, the cooling system 10 of FIG. 3 comprises a bleed
valve arrangement 70 which in its open state serves to discharge
refrigerant from the first section 12a of the cooling circuit 12 to
the unpressurized region 40 of the aircraft. The bleed valve
arrangement 70 is formed by an electrically actuatable safety valve
which is connected to the first section 12a of the cooling circuit
12 via a connecting line 72. The bleed valve arrangement 70 may be
controlled by the control unit 52 as described above in connection
with the bleed valve arrangement 50. The additional pressure relief
valve 68 and the bleed valve arrangement 70 are connected to a gas
line of the cooling circuit 12 extending downstream of the
evaporators 14a, 14b, 14c, 14d and thus having a larger flow cross
section than a liquid line of the cooling circuit 12 extending
upstream of the evaporators 14a, 14b, 14c, 14d. As a result, a
large amount of refrigerant can be quickly discharged from the
cooling system 10 via the additional pressure relief valve 68 and
the bleed valve arrangement 70.
[0094] Otherwise, the structure and the operating principle of the
cooling system 10 according to FIG. 3 correspond to the structure
and the operating principle of the arrangement of FIG. 2.
[0095] The cooling system 10 according to FIG. 4 differs from the
arrangement of FIG. 3 in that the cooling circuit 12 of the cooling
system 10 comprises two first sections 12a, 12a' which are formed
separate from each other. Two evaporators 14a, 14b are disposed in
the first cooling circuit section 12a, and two evaporators 14c, 14d
are disposed in the first cooling circuit section 12a'. A first and
a second cooling circuit control valve 36, 38 in their closed state
serve to seal the first cooling circuit section 12a from the second
cooling circuit section 12b. A first and a second cooling circuit
control valve 36', 38' in their closed state serve to seal the
first cooling circuit section 12a' from the second cooling circuit
section 12b. Pipe burst safety valves 66a, 66a', 66b, 66b' are
associated with each of the first and the second cooling circuit
control valves 36, 36', 38, 38'. The pipe burst safety valves 66a,
66a', 66b, 66b' may be disposed in the cooling circuit 12 at the
positions shown in FIG. 4. It is, however, advantageous to install
the pipe burst safety valves 66a, 66a', 66b, 66b' in the
unpressurized aircraft region 40 so as to allow refrigerant
discharged from the cooling system via the pipe burst safety valves
66a, 66a', 66b, 66b' to be vented to the unpressurized aircraft
region 40 and finally the aircraft environment.
[0096] The cooling system 10 further comprises two first pressure
relief valves 44, 44' wherein the first pressure relief valves 44
is associated with the first cooling circuit section 12a, and
wherein the first pressure relief valves 44' is associated with the
first cooling circuit section 12a'. In addition an additional
pressure relief valve 68 is associated with the first cooling
circuit section 12a, whereas an additional pressure relief valve
68' is associated with the first cooling circuit section 12a'.
Finally two bleed valve arrangements 70, 70' are present, wherein
the bleed valve arrangement 70 is associated with the first cooling
circuit section 12a, whereas the bleed valve arrangement 70' is
associated with the first cooling circuit section 12a'.
[0097] The evaporators 14a, 14b, 14c, 14d disposed in the two first
cooling circuit sections 12a, 12a' may be operated independently
from each other, i.e. it is possible to operate an evaporator 14a,
14b, 14c, 14d disposed in one first cooling circuit section 12a,
12a', but not to operate an evaporator 14a, 14b, 14c, 14d disposed
in the other first cooling circuit section 12a, 12a'. Further, by
suitable controlling the cooling circuit control valves 36, 36',
38, 38', the two first cooling circuit sections 12a, 12a' may be
sealed from the second cooling circuit section 12b independently
from each other.
[0098] Otherwise, the structure and the operating principle of the
cooling system 10 according to FIG. 4 correspond to the structure
and the operating principle of the arrangement of FIG. 3.
[0099] The cooling system 10 according to FIG. 5 differs from the
arrangement of FIG. 4 in that an additional line is provided for
connecting an outlet of the conveying device 34 to the accumulator
28. An additional valve 32' is provided to control the supply of
refrigerant from the conveying device 34 to the accumulator 28.
This arrangement increases redundancy in case of a failure of one
of the valves 32, 32'. Further, also for increasing system
redundancy, beside the cooling circuit control valves 36, 36', 38,
38', additional cooling circuit control valves 74, 76 are provided
which, in their closed state, allow to seal both first cooling
circuit sections 12a, 12a' from the second cooling circuit section
12b.
[0100] Moreover, additional bleed valve arrangements 78, 78'
further improve the operational safety of the cooling system 10,
wherein the bleed valve arrangement 78 is associated with the first
cooling circuit section 12a, whereas the bleed valve arrangement
78' is associated with the first cooling circuit section 12a'.
Further additional pressure relief valves 80, 80' also improve the
operational safety of the cooling system 10. Since the evaporators
14a, 14b, 14c, 14d may be susceptible to pipe burst, each one of
the evaporators 14a, 14b, 14c, 14d is disposed between a respective
pair of additional pipe burst valves 82, 82'. Bypass lines 84, 86,
84', 86' are provided for bypassing the evaporators 14a, 14b and
the evaporators 14c, 14d, respectively, wherein the refrigerant
flow through bypass lines 84, 84' is controlled by respective
pressure relief valves 88, 88', whereas the refrigerant flow
through bypass lines 86, 86' is controlled by respective control
valves 90, 90'.
[0101] Otherwise, the structure and the operating principle of the
cooling system 10 according to FIG. 5 correspond to the structure
and the operating principle of the arrangement of FIG. 4.
[0102] As an alternative to the cooling circuit control valve
arrangement shown in FIG. 5, an arrangement according to FIG. 6 can
be employed in the cooling system of FIG. 5. The modular
arrangement according to FIG. 6 comprises two cooling circuit
control valves, for example cooling circuit control valves 74 and
36, which are connected in series with a volume 92. Additional
pressure relief valves 94, 96 may be employed in the modular
arrangement according to FIG. 6.
[0103] The features of the different cooling system embodiments
described above with reference to FIGS. 1 to 6 may be combined in
an arbitrary manner. Further, selected features of the exemplary
embodiments described herein may be dispensed with. For example,
the cooling system of FIG. 5 does not necessarily have to comprise
all the features depicted in FIG. 5. Instead, selected components
such as for example lines, valves and the like may be dispensed
with as desired.
[0104] In the embodiments of a cooling system 10 described above,
the accumulator 28 fulfills the double function of storing liquid
refrigerant exiting the condensers 22a, 22b and, in addition
thereto, of reducing the system pressure in the cooling circuit 12.
The pressure reducing effect of the accumulator 28 results from the
additional volume the accumulator 28 adds to the volume of the
cooling circuit 12 and becomes more and more significant, as the
volume of the accumulator 28 increases. The importance of the
pressure reduction function of the accumulator 28 increases as the
operating temperature of the cooling system 10 and hence the
pressure in the cooling circuit 12 increases and is of particular
relevance if the cooling system 10 is operated with a refrigerant
causing a high system pressure such as, for example, CO.sub.2.
[0105] Basically the cooling system 10 may comprise only the
accumulator 28 as described above, which may serve to store liquid
refrigerant exiting the condensers 22a, 22b and to reduce the
system pressure in the cooling circuit 12. Alternatively, the
accumulator 28 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 and of reducing
the system pressure in the cooling circuit 12. It is, however, also
conceivable to equip the cooling system 10 with the accumulator 28
and an additional storage container, wherein either both components
or only one of the accumulator 28 and the storage container may
serve to store liquid refrigerant exiting the condensers 22a, 22b
and to reduce the system pressure in the cooling circuit 12.
Finally, a configuration of the cooling system 10 is conceivable,
wherein the accumulator 28 serves to collect and to store liquid
refrigerant, whereas the storage container, due to its additional
volume, serves to reduce the system pressure.
[0106] 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, the pressure reducing storage container 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.
[0107] Further, in case the storage container merely serves to
control the pressure in the cooling system 10, it is not necessary
to provide for a direct fluid connection between the accumulator 28
and the storage container. Instead, the storage container may be
connected to the cooling circuit 12 via only a single line
branching off from the cooling circuit 12, for example, upstream of
the condensers 22a, 22b and downstream of the evaporators 14a, 14b,
14c, 14d. The line connecting the storage container to the cooling
circuit 12 preferably is connected to the storage container at the
geodetic lowest point of storage container. This configuration
ensures that the storage container 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, two storage containers may be
provided, in the cooling system 10, wherein a first storage
container may be connected to the cooling circuit 12 via a line
branching off from the cooling circuit 12 upstream of the first
condenser 22a and downstream of the evaporators 14a, 14b, 14c, 14d
and wherein a second storage container may be connected to the
cooling circuit 12 via a line branching off from the cooling
circuit 12 upstream of the second condenser 22b and downstream of
the evaporators 14a, 14b, 14c, 14d.
* * * * *