Note: Descriptions are shown in the official language in which they were submitted.
CA 02509452 2005-06-08
EVAPORATOR ARRANGEMENT FOR AN AIR CONDITIONING SYSTEM
OF AN AIRCRAFT
Field of the invention
The present invention relates to air conditioning in an aircraft. In
particular, the
present invention relates to an evaporator arrangement for an air conditioning
system
of an aircraft, to an air conditioning system for an aircraft, to an
evaporator pad for
use in a direct evaporator in an air conditioning system of an aircraft, and
to a method
for operating an evaporator arrangement of an air conditioning system of an
aircraft.
Technological background
Especially in pressurised cabins of commercial aircraft and transport
aircraft, the
humidity of the air can drop during flight. For example the humidity of the
air can
drop to as little as 3% relative humidity (% RH) at room temperature.
Passengers may
consider such low humidity uncomfortable.
In order to increase thermal comfort, the cabin air can be humidified in part
or in
whole. US 5,359,692 describes a system which uses electrical energy for
evaporating
water. US 4,272,014 and EP 0 031701 describe systems which use hot air to
evaporate water. In these systems the water vapour is mixed with the cooled
air and is
supplied to the air conditioning unit. These systems are associated with a
disadvantage in that the thermal load in the cabin is increased by mixing
water vapour
with hot air.
Furthermore, there are air humidifiers which are based on the principle of
cold
evaporation, such as for example the diaphragm humidifier described in US
5,595,690. EP 0 779 207 B1 describes an atomiser and an evaporator with a
porous
dripper bed.
In particular in aircraft engineering, individual components have to be highly
reliable
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Summary of the invention
According to an embodiment of the present invention, an evaporator arrangement
for
an air conditioning system of an aircraft is provided, which air conditioning
system
comprises a main air conduit, a bypass conduit and an evaporator. The
evaporator is
arranged in the main air conduit in such a way that an airflow in the main air
conduit
flows through the evaporator. If required, the bypass conduit can be connected
in such
a way that at least part of the airflow bypasses the evaporator.
This may make possible safe operation of the evaporator arrangement to the
effect
that when the evaporator is blocked, for example by ice crystals or dirt, the
airflow
can continue to be maintained because it is directed past the blocked
evaporator. The
aircraft's air conditioning system can therefore continue to operate even if
the
evaporator is blocked, so that only the humidification of the air ceases to
operate.
According to a further embodiment of the present invention, a safety valve is
arranged
between the main air conduit and the bypass air conduit, which safety valve
opens the
bypass air conduit at least in part if a predefined pressure in the main
conduit
upstream of the evaporator is exceeded, so that at least part of the air from
the main
air conduit bypasses the evaporator.
This may ensure automatic operation without the need for the safety valve to
be
activated by an operator.
According to a further exemplary embodiment of the present invention, a
diffuser is
provided in the air conduit upstream of the evaporator, which diffuser forms
the
airflow in such a way that the airflow comprises flow lines of essentially
identical
speed.
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This may make possible an as homogeneous a load of the evaporator as possible
because the flow lines of the airflow impinging on the evaporator are
essentially of
identical speed.
According to a further exemplary embodiment of the present invention, between
the
diffuser and the evaporator a grille or grid, for example comprising a
honeycomb
structure, can be provided in order to further even out the flow of the
airflow. This can
generate a particularly homogeneous airflow that impinges on the evaporator.
According to a further exemplary embodiment of the present invention, a
temperature
sensor is provided. According to one aspect of this embodiment, the
temperature
sensor is arranged in a flow direction of the airflow upstream of the
evaporator. The
temperature sensor may detect excessive temperatures in the airflow upstream
of the
evaporator, for example in order to prevent damaging the evaporator or the air
conditioning system, or to prevent injury to passengers.
According to a further exemplary embodiment of the present invention, the
evaporator
has a flow direction. The flow direction is a direction in which air can flow
through
the evaporator with the least amount of resistance. According to one aspect of
this
embodiment, the evaporator is arranged in the main air channel such that the
flow
direction of the evaporator is not arranged so as to be orthogonal in relation
to the
flow direction of the airflow impinging on the evaporator. In other words, the
evaporator is arranged so as to be across the airflow direction or inlined to
the airflow
impinging onto the evaporator. An angle between the flow direction of the
evaporator
and the airflow impinging on the evaporator can be between 0° and
somewhat less
than 90°.
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According to a further exemplary embodiment of the present invention, a
deflector
comprising a honeycomb structure can be provided on the evaporator in order to
deflect flow lines of the air flow into the evaporator. This may make possible
homogeneous and even use of the evaporator since the airflow is introduced to
the
evaporator essentially evenly across the surface of said evaporator. Dead
zones, i.e.
zones in which there is no airflow through the evaporator, may be avoided.
According to a further exemplary embodiment of the present invention, the
evaporator
arrangement comprises a housing. The housing may be designed so as to be sound
absorbent.
This embodiment of the present invention may make it possible for the
evaporator
arrangement to be integrated on positions of sound absorbers. The sound
absorber at
the same time has an insulating effect so that the temperature loss across the
evaporator can be kept low.
According to a further exemplary embodiment of the present invention, the
evaporator
is a direct evaporator comprising an absorbent porous, inorganic material,
such as for
example glass fibres bound in inorganic adhesives.
This may make possible a sturdy and capable evaporator which can be produced
at
low cost.
Furthermore, the present invention relates to an air conditioning system for
an aircraft,
comprising an evaporator arrangement according to one of the above
embodiments.
The air conditioning system can also comprise components, such as for example
a
control unit or various mixers.
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According to a further exemplary embodiment of the present invention, an
evaporator
pad for arrangement in a direct evaporator in an air conditioning system of an
aircraft
is provided. The evaporator pad comprises an absorbent element with a flow-
through
direction which, as discussed above, is the direction of the absorbent
element, along
which flow-through direction an airflow can flow through the absorbent element
with
minimum resistance. For arrangement in the direct evaporator, the absorbent
element
is adapted in such a way that the flow-through direction is not necessarily
aligned so
as to be orthogonal or perpendicular to the direction of flow of an airflow
impinging
on the absorbent element. Furthermore, for arrangement, the absorbent element
can be
designed such that air can bypass the absorbent or absorptive element, for
example in
a bypass conduit.
According to a further exemplary embodiment of the present invention, a flow
direction device comprising a honeycomb structure can be arranged on the
absorbent
element in order to make possible clean, even guide-in of the airflow into the
absorbent element.
According to a further exemplary embodiment of the present invention, a method
for
operating an evaporator arrangement for an air conditioning system of an
aircraft is
stated, wherein according to the method the evaporator is operated in the main
conduit
in such a way that an airflow in the main air conduit flows through the
evaporator.
When required, for example if the evaporator becomes blocked as a result of
ice or
dirt, the bypass conduit can be connected such that at least part of the
airflow
bypasses the evaporator.
In this way, operation of the air conditioning system or of the evaporator
arrangement
can be made possible even if the evaporator is blocked.
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According to a further exemplary embodiment of the present invention, the
temperature of the airflow is measured upstream of the evaporator. The
measured
temperature is used to control the temperature in the air conditioning system.
This can help to prevent overheating of various components in the air
conditioning
system.
The present invention may make possible humidification of cabin air in an
aircraft by
means of a direct evaporator, as well as integration of the direct evaporator
in the air
conditioning system. The present invention may make it possible for the
available
space to be optimally used, or for the design height and design width of the
evaporator
arrangement to be minimised. Above all, the present invention may make it
possible,
in applications in an aircraft, to avoid any loss of pressure, in particular
in the case of
limited functionality of the air conditioning system. Furthermore, for example
in the
case of failure or partial failure of the evaporator, it may be ensured that
the
functionality of the air conditioning system is not impeded. In particular the
present
invention is believed to make it possible to detect excessive temperatures and
to take
early countermeasures. Such excessive temperatures may occur on parts or
components of the air conditioning system.
Short description of the drawines
Below, exemplary embodiments of the present invention are described in more
detail
with reference to the figures stated.
Fig. 1 shows a diagrammatic representation of an embodiment of an air
conditioning
system for an aircraft, according to the present invention.
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Fig. 2 shows a diagrammatic section view of an embodiment of an evaporator
arrangement according to the present invention, as can be arranged in
particular in air
conditioning systems for aircraft.
Detailed description of exemplary embodiments
In the following description of Figures 1 and 2 identical or corresponding
elements
are designated using the same reference figures.
Fig. 1 is a diagrammatic representation of an air conditioning system for an
aircraft
according to an exemplary embodiment of the present invention. Fig. 1 in
particular
shows the way in which, according to the present invention, a direct
evaporator is
integrated in the air conditioning system of a commercial aircraft or
transport aircraft.
Reference number 1 designates a central or decentralised mixer unit 1 which
mixes
two airflows which can comprise recirculated air and outside air. According to
a
variant of this embodiment, the mixer unit 1 can also be designed to mix two
recirculating airflows. From the mixer unit 1, one or several airflows 2
emanate,
whose temperature can be adjusted by means of admixing hot air 5. The hot air
5 can
for example be engine bleed air. A valve 4 is provided for dosing the hot air
S. The
valve is connected to a control device (not shown in Fig. 1 ) which evaluates
temperature data from the cabin and from the temperature sensors 6 and 10
installed
in the air conditioning plant, and adjusts the valve position to the actual
and desired
temperature values. The temperature sensor 6 may make it possible to detect
excessive temperatures in the air conditioning pipe, i.e. in the air conduit
which leads
to the humidifier unit 3. As shown in Fig. 1, the temperature sensor 6 is
arranged in
the airflow upstream of the humidifier unit 3.
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The further temperature sensor 10, which is arranged in the air conduit
continuing
downstream of the humidifier unit 3, is not only designed to read the
temperature but
also the humidity of the air. Advantageously, the temperature sensor 10 can in
this
way be used for regulating the temperature when the cabin temperature reacts
too
slowly.
The humidifier unit 3, which can for example be designed as a direct
evaporator, can
take the water to be evaporated from the on-board fresh water system or from a
separate water system. To separate the humidification system from the water
system
in this context, an automatic check valve 7 is provided which controls the
water flow
in a water pipe 8 to the humidifier unit 3. Advantageously, the water pipe 8
between
the check valve 7 and the humidifier unit 3 is self draining. For example this
can be
achieved in that the diameter of the water pipe 8 is designed large enough,
e.g.
measuring at least one inch, or the valve 7 is designed to deaerate the water
pipe 8.
In order to disinfect the entire humidification system or air conditioning
system as
shown in Fig. 1, and in order to prevent water ingress into the air
conditioning system,
the humidifier unit 3 is connected to an aircraft drainage system 9. To
prevent return
flow of the grey water and permanent air leakage of the air conditioning
system, a
protective component 14 can be integrated in the drainage system. This
protective
component 14 prevents return flow of the grey water and permanent air leakage
of the
air conditioning system. Although in Fig. 1 the protective component 14 is
integrated
in the drainage system which comprises the components 9 and 14 (for the sake
of
clarity, the entire drainage system is not shown in Fig. 1), the protective
component
14 can also be arranged in or integrated in the humidifier unit 3.
Reference number 13 designates a controller which, as shown in Fig. 1, is
connected
to the temperature sensor 10 by means of a line 11. Furthermore, the
controller 13 can
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be connected to the humidifier unit 3 by means of the line 12. As stated
above, the
temperature sensor 10 can also be designed for measuring the humidity of the
air so
that the controller 13 can be designed for controlling the humidifier unit 3.
Furthermore, the controller 13 can be connected to the temperature sensor 6,
the valve
4, the valve 7 and the protective component 14 and can control the function of
the
individual elements. Advantageously, the controller 13 controls operation of
the air
conditioning system such that humidification is controlled by means of a
closed
control loop. Moreover, the controller 13 can be connected to a data system of
the
aircraft (not shown in Fig. 1) and can for example transfer data for display
in the
cockpit.
Fig. 2 shows a diagrammatic section view of an evaporator arrangement
according to
the present invention as can also be used for example in an alr conditioning
system as
shown in Fig. 1.
As shown in Fig. 2, the airflows provided by a central or decentralised mixer
unit are
fed in an air conduit to an evaporator unit or evaporator arrangement. The
feeding air
conduit comprises a diffuser 16, which can for example be designed as a throat
in the
air conduit. The temperature sensor 6 is provided in the air conduit,
downstream of
the diffuser 16. The airflow fed from the air conduit then passes an air
direction
device or a grille 21. The diffuser 16 is designed in such a way that it
generates flow
lines in the airflow which essentially move at the same speed. The grille 21,
which
can for example comprise a honeycomb structure, is arranged to further even
out or
adjust the flow speed of the airflow. In this way it can advantageously be
achieved
that the flow lines between the grille 21 and a flow direction device 17 are
essentially
parallel in relation to each other. Reference number 15 designates a direct
evaporator
which is arranged downstream of the flow direction device 17. According to one
aspect of the present invention, the direct evaporator has a preferred flow-
through
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direction, i.e. a direction in which an airflow can flow with very little
resistance
through the direct evaporator. According to the present invention, this
direction is not
necessarily orthogonal in relation to the flow direction of the airflow which
is directed
through the diffuser 16 and the grille 21 so as to provide long contact times
between
the volume flow and the evaporator surface. In Fig. 2 the flow direction
device and
the direct evaporator 15 are arranged at an angle of approximately 20°
in relation to
the direction of flow of the airflow. According to the present invention, this
angle can
be between 0° and approximately 90°.
As indicated by means of the arrows in Fig. 2, the air flowing from the direct
evaporator 15 is fed to a further air conduit and is for example fed to
further elements
of an air conditioning system or directly into the cabin.
Reference number 18 designates a safety valve. The safety valve 18 is arranged
between the air conduit for feeding the airflow to the air humidifier 15 and a
bypass
conduit. This makes it possible, for example, for the valve 18 to be opened
when the
grille 21, the flow direction device 17 or the direct evaporator 15 becomes
blocked, so
that the air can bypass these three elements.
The direct evaporator 15 can comprise an absorbent material which for example
meets
the relevant specifications relating to hygiene and safety in aircraft
engineering. For
example, such a material can be a conventional inorganic material, such as for
example glass fibres bound in inorganic adhesives. The direct evaporator 15
can
however also be made from polymer or metallic components. Moreover, polymer
materials that are combustion resistant, temperature resistant and not
biologically
degradable can be used. A porous evaporator structure of the direct evaporator
15
advantageously comprises flow conduits 0.5 to 2 cm in diameter, which flow
conduits
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do not necessarily have to be aligned so as to be orthogonal in relation to
the inlet
face.
According to one aspect of the present invention, the direct evaporator 15 is
arranged
at an inclination in relation to the flow direction. In other words, the
absorbent
material of the direct evaporator 15 is arranged across the flow direction.
This may
make possible a design of the evaporator arrangement, which design saves a
great
deal of space, as well as making possible easy integration in the air
conditioning
system. Furthermore, the inclined installation results in the cross-sectional
area of the
direct evaporator or of the evaporator unit being very large, so that the flow
speed of
the airflow through it is reduced and in turn the danger of particles or
droplets being
carried along is reduced.
As already indicated, a diffuser 16 can be arranged at the entry to the
humidifier,
which diffuser 16 slows down the flow speed of the airflow and evens it out so
as to
optimally use the existing surface of the direct evaporator 15.
Advantageously,
arranging the diffuser 16 with or without the grille 21 makes it possible to
prevent
different flow speeds which can lead to short flows in the front inlet region
and to
banking up in the rear region of the direct evaporator 15. In particular, by
arranging
the diffuser 16 and the grille 21, the occurrence of dead areas, for example
in the
acute angle in the end region of the direct evaporator 15 (in the region of
reference
number 17) may be prevented.
A temperature sensor 6, for example a hot-air temperature sensor, may be
arranged
downstream of the diffuser 16. This may allow to detect an overtemperature of
the
infed airflow. Arranging the temperature sensor between the diffuser and the
direct
evaporator 15 may be advantageous in a hot-air infeed just upstream of the
evaporator
(such as for example line 5, which leads into the air conduit just upstream of
the
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evaporator arrangement), because the mixing distance between the fed-in hot
air and
the airflow is very short.
In order to achieve a further improvement in the flow through the porous
surface of
the direct evaporator 15, a honeycomb structure 17 of approx. 2 cm honeycomb
diameter and 1 to 2 cm in depth is provided upstream of the direct evaporator
1 S. It
should be mentioned that geometric shapes other than honeycomb shapes are also
possible. At the sharp edge, the honeycomb structure suddenly deflects the
flow lines
of the airflow and leads the airflow through the porous evaporator structure,
i. e.
through the direct evaporator 15.
The safety valve 18 mentioned earlier can for example comprise a calibrated
spring-
loaded flap. In the case of a blockage in the porous evaporator structure,
i.e. a
blockage of the grille 21 or in particular a blockage of the flow direction
device 17 or
of the direct evaporator 15, this flap is designed to maintain the safety-
relevant
function of providing cabin air. To this effect, the flap 18 can for example
be designed
or arranged such that if a certain pressure in the air conduit is reached, the
bypass
conduit is opened so that the air bypasses the elements 15, 17 and 21. In
particular, a
situation can be brought about in which the air does not have to flow through
the
direct evaporator 15.
A blockage can for example occur as a result of lodgement of extraneous matter
introduced with the outside air, for example pieces of plastic, plastic foil
or snow or
ice issuing from the mixer unit. Above all on the ground on hot and humid
days, snow
might issue from the mixer unit so that in unfavourable cases the evaporator
might get
blocked.
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Advantageously, the grille (or grid) 21 with the honeycomb structure can be
adapted
in such a way that apart from evening out the airflow it also provides
additional
mechanical protection to the direct evaporator 15.
The evaporator arrangement comprises a housing 19 in which a service flap 20
is
provided. Both the housing 19 and the service flap 20 can comprise sound
protection.
In this way it is possible for the evaporator arrangement to be integrated on
positions
of sound absorbers. The sound protection can at the same time have an
insulating
effect so that any temperature loss above the evaporator arrangement can be
kept to a
minimum. However, it should be pointed out that embodiments are imaginable in
which only one side of the evaporator arrangement can comprise a sound
absorber or
heat insulation.
The service flap can facilitate the exchange of the direct evaporator 15 and
of other
components.
Due to the very confined installation situation in the vicinity of the mixer
unit, two or
several temperature zones can be integrated in a common evaporator unit. To
this
effect, the volume flows to be humidified are separate from each other, e.g.
arranged
one on top of the other, or one below the other, or one beside the other. This
combination of temperature zones in a unit is believed to offer an advantage
in that
the number of the mechanical and hydraulic interfaces is reduced.
In this way an air conditioning system or an evaporator arrangement is
provided
which is able to generate humidity of the air from 20 to 60% relative humidity
at
room temperature, without introducing an additional heat load into the cabin.
By
increasing the humidity of the air, the thermal comfort of the cabin air
during flight
can be improved.
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The evaporator arrangement according to an exemplary embodiment of the present
invention can be integrated in an air conditioning system to form an air
conditioning
system according to the invention. This may make it possible to reduce the
installation
space so that the height and the width can also be minimised. Furthermore, by
providing a bypass conduit, a very safe arrangement may be provided because
even a
malfunction of the direct evaporator is believed to not impede the
functionality of the
entire air conditioning system.
Although the present invention has been described with reference to a
humidifier
arrangement in an air conditioning system for an aircraft, it should be
pointed out that
the present invention can also be applied to vehicle engineering generally.
In addition, it should be pointed out that "comprising" does not exclude any
other
elements or steps, and that "one" does not exclude a plural number.
Furthermore, it
should be pointed out that characteristics or steps which have been described
with
reference to one of the above embodiments can also be used in combination with
other characteristics or steps of other embodiments described above. Any
reference
characters in the claims are not to be seen as limitations.
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