Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to a structure for reducing the
latent and sensible heats of warm, humid air to more acceptable
levels in an environment such as the interior of an automobile.
The structure will be described with reference to its
use as an air conditioner in an automobile but it will be
evident -that the structure lends itself to other uses.
Conventionally air conditioners in automobiles consist
of a refrigeration cycle applied to air fed into the automobile
and using mechanical work provided by a ta~e off from the
motor. This mechanical work is conventionally a pump used to
compress a refrigerant and the normal refrigeration cycle is
applied to the air in a heat exchanger where vapourisation of
the coolant removes heat from the air. In the process, the dew
point of the air is usually reached because air conditioning is
most beneicial in environments where the ambient air is both
hot and humid, Conse~uently the air is subject to an initial
drop in temperature to the dew point and then a large amount of
heat has to be removed to reduce the temperature of the air
further because most of the heat is being used to provide latent
heat of condensation as the water is condensed from the air.
The resulting cooled air is at 100% relative humidity and
consequently it is necessary to e~pend more energy to reduce the
temperature of the air to a point below the temperature required
in the automobile so that the air has an opportunity to warm to
return the relative humidity to an acceptable level.
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A further disadvantage of conventional air conditioners
is that the mechanical work is drawn directly from the running
motor: there is no buffer to store energy. As a result the
motor must be tuned and adjusted to run when idling with the
extra load of the pump. Also these tend to be sensitive moving
parts and the structure requires a refrigerant which quite often
has to be replaced.
The conventional air conditioners are capable of
cooling quite large volumes of air and are in wide use.
~owever, where smaller cooling effects are required,
thermoelectric devices have found a use. These devices are very
simple and consist essentially of hot and cold sides resulting
from an input o electrical power. The cool side is used to
cool for instance a small wine cooler whereas the hot side is
radiated to the external surroundings. The devices have found
acceptance in such uses as portable refrigerators, electronic
equipment coolers, aquarium coolers, cream dispensers, medical
intrument uses and military uses. ~owever the thermoelectical
device has been limited to these kind o~ smaller devices and has
not found a use in cooling large volumes such as that found
inside an automobile.
In theory, thermoelectric devices have many advantages
over a conventional refrigeration system. Most importantly they
are small and have no moving parts whereas refrigeration systems
include a mechanical compressor, they are noisy and they are
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quite bulky. It would therefore be desireable to implemerlt the
advantages of thermoelectric devices in an air conditioniny unit
capable of cooling an automobile for instance. Simple control,
quick response and even the possibility of using the system
without the need to operate the vehicles motor would result from
the use of such a device.
It is therefore an object of the present invention to
provide a struc~ure which is capable of controlling the air
temperature in a limited environment such as that found in an
automobile interior and to implement the advantages of
thermoelectric devices.
Accordinyly in one of its aspects, the invention
provides an air-conditioner for use in an automobile in which
the air conditioner includes a thermoelectic device having a hot
side and a cold side. A cooler is attached to the cold side, a
heat dissipator is attached to the hot side, and a drier is
provided to dehumidify the air before the air meets the cooler
to thereby limit the cooler to sensible heat removal to lower
the air temperature.
Accordiny to another of it~ aspects, the invention
provides a method o~ conditioning air in an automobile to reduce
the sensible and latent heats of intake air. ~umid and warm air
is directed into the automobile and passed through a
dehumidifying means to remove the moisture from the humid air
isothermally until the relative humidity is such that the air
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has a dew point below the temperature required for the cooled
air in the automobile. ~ext the air is passed through a cooler
; coupled to the cold side of a thermoelectric device to cool the
air before passing the cold air into the interior of the
S automobile.
The invention will be better understood with reference
to the f~llowing description taken in combination with the
drawing in which:
Fig. 1 is a schematic sectional view of a preferred
embodiment of the invention and showing also parts of a control
circuit necessary to operate the structure.
Reference is made to Fig. 1 which shows a preferred
embodiment of structure according the invention. Warm, humid
air lS received at an inlet 20 of a drier designated generally
by the numeral 22 and then, having had moisture removed, the air
is passed through a connector 24 to a cooler 26 where sensible
heat is removed before the air leaves through an ~utlet 2a. The
cooler 26 is at the cold side of a thermoelectric device 30, and
on the hot side of the device, a heat sink reservoir 32 forms
part of a heat dissipater ~4 which also includes a radiator 36.
This radiator is connected hydraulically by pipes 38 and water
or other coolant is pumped through the reservoir and radiator by
a small electric pump 40.
The thermoelectric device 30 (preferably model
CP-5-31-06L made by Materials Electronic Products Corporation)
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is sandwiched between a pair of electrical insulators 42, 44 of
a material having good thermal conductivity. Preferably the
material used is a quaternary alloy of bismuth, tellurium,
selenium and antimony with small amounts of dopant added
oriented in a polychrystalline ingot with good anistropic
thermal electric properties. These layers are also respectively
in surface-to-surface contact with a bottom plate 45 having
upstanding parallel fins 47 in the cooler 26, and with a wall 46
of the reservoir 32. Ends of the thermoelectric device are
sealed at 48, 50 to prevent moisture transfer in and out of the
device and the device and reservoir are surrounded at their
vertical extremities (as drawn) and at the bottom of the
reservoir by insulation 52. Preferably a silicone insulation is
used.
~ base 54 supports the structure and a housing 56 sits
on the base and provides openings to receive grommets S8 and 60
surrounding pipes 38 where they enter and leave to carry coolant
to and from the reservoir 32. The housing also defines an inlet
o~ening 62 and outlet opening 64 to receive air from the
connector 24 and to ~eed air to outlet 28.
The thermoelectric device 30 can be made up of a number
oE individual devices and in this instance, three are shown in
the drawing. The number will depend upon the capacity of the
device and the cooling required. The devices are connected in
an electrical circuit by two connectors 66, 68 which terminate
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at a controller 70. The arrangement will be described more
fully later.
Turning now to the drier 22, this consists of a
cylindrical outer casing 72 containing a cylindrical inner
casing 74 which can rotate on stub axles 76, 78 provided
centrally at the ends of the inner casing and rotating in
suitable mountings in the outer casing. The axle 78 terminates
in a pinion 80 coupled to a motor 82 which can be operated
through a timer 84 by the controller 70.
The inner casing defines two cavities separated by a
central wall 86 which extends diametrically across the casing.
This wall separates the casing into a first cavity 88 and a
second cavity 90 both of which contain silica gel. Ends of the
cavities are open to the passage of air with the ends nearer the
cooler having respective activated carbon filters 92, 94 to
retain particulate silica gel and prevent it being carried by
the air strea~l out of the housing.
The outer casing of the drier 22 defines a first inlet
96 and a second inlet 98 as well as a first outlet 100 and a
second outlet 102. In the position shown in Fig. 1, air
entering the inlet 96 passes through the ~irst cavity 88 and
leaves by outlet 100. Similarly, air entering via the inlet 98
will pass through the cavity 90 and leave by the outlet 102.
The first cavity is subject to warm humid air entering
the inlet 20 and removes moisture from this air to a point where
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the air leaving by the outlet 100 has a dew point lower or equal
to the tempèrature of the air leaving the outlet 28 from the
cooler 26. The silica gel in the first cavity 88 will
eventually carry sufficient moisture that it is no longer
efficient and because of this, the silica gel will have to be
rejuvenated. In practice, a timing cycle is used which on
average allows moisture to accumulate in the silica gel until it
has reached about 70% of its capacity for removing moisture. At
this point a timer 84 activates the motor 82 to rotate the inner
casing 74 through 180 thereby reversing the positions of the
first and second cavities. ~ot air is led from the motor of the
automobile through the inlet 98 and then through the silica gel
where it removes moisture and delivers it to the outlet 102 from
which it is fed to atmosphere outside the automobile. This flow
lS of hot air continues to dry the gel, thereby rejuvenating the
gel ready for the next cycle when this cavity is returned to the
position shown in E`ig. 1 to again remove moisture from the warm
humid air.
It will be evident that the drier 22 operates on energy
which i5 otherwise wasted by the vehicle. The silica gel
removes moisture from the air in an essentially isothermic
manner and this moisture is then removed from the silica gel
using hot air. Because the hot air is essentially outside air
raised to an elevated temperature, its relative humidity has
dropped to the point where more moisture can be removed from the
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gel. Consequently~ the drier operates on waste energy which
adds to the efficiency of the structure.
In operation, because the heat dissipator 34 is
self-contained, the structure can be switched on prior to engine
use or while the vehicle is parked. Obviously, it would be
possible for the cooler to get to a temperature which is too low
and similarly for the reservoir to reach a temperature which is
too high and such extreme temperatures could create unacceptable
stresses in the thermoelectric device 30. This is why a sensor
10~ is provided on the pipe 38 to carry an analogue signal to
the controller 70 indicating the temperature of the water
leaving the reservoir 32 and also why a sensor 106 is provided
on the outlet 28 to indicate the temperature of air leaving
that outlet. Should extremes be reached, then the controller
can switch off and wait for the temperatures to change to more
acceptable levels
The controller 70 is also connected to the pump 40 (by
wiring which has been omitted for clarity) so that provided an
air fan is moving air through the system, the structure can
operate independent of the automobile's motor.
In normal operation the vehicle will be moving and the
radiator 36 will dissipate heat to enhance the efficiency of the
unit. Prior to movement however, there will be some radiation
and of course there is in effect a buffer because of the volume
of coolant in the system. ~evertheless, use of the structure
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when the vehicle is standing stationary will be limited because
unacceptable temperatures levels will be reached.
As a vehicle moves along, the radiator 36 dissipates
heat from the reservoir, thereby maintaining the hot side of the
thermoelectric device at an acceptable level. Similarly, the
coolant takes up heat from the air, thereby reducing the air to
the required level as it leaves the outlet 28.
It is also possible to use the device as a heater. By
simply reversing the polarity of the DC supply to the
thermoel~ctric device, the cooler becomes a heater and outside
air can be heated for improving the ambient temperature in the
vehicle. Such a system would benefit from the use of more
chambers in the drier 22. For instance, one could b~ provided
without silica gel so that air would have free flow in the
heating mode. Similarly, more chambers of gel would permit
;cycling more often with greater time for rejuvenation of the gel
in each chamber.
: Further modifications within the scope of the invention
`would include enhancing the heat sink capability for use prior
to moving the vehicle, For instance, an intermediate structure
could be provided between the thermoelectric device and the base
42 carrying the ~ins 44. This intermediate structure would
include material with a high heat accumulating ability such as
an aerated gel. The gel would drop in temperature significantly
and as soon as the vehicle is started up there would be a boost
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of cold alr.
These and other modifications are within the scope of
the invention as described and claimed.
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