U.S. patent application number 12/675997 was filed with the patent office on 2010-08-12 for thermoelectric device for defogging and defrosting applications.
This patent application is currently assigned to CARRIER CORPORATION. Invention is credited to Alexander Lifson, Richard G. Lord, Michael F. Taras.
Application Number | 20100199686 12/675997 |
Document ID | / |
Family ID | 40718007 |
Filed Date | 2010-08-12 |
United States Patent
Application |
20100199686 |
Kind Code |
A1 |
Taras; Michael F. ; et
al. |
August 12, 2010 |
THERMOELECTRIC DEVICE FOR DEFOGGING AND DEFROSTING APPLICATIONS
Abstract
A controlled surface having a direct contact with a flow of cold
air circulating within a climate-controlled space is provided. A
thermoelectric device is associated with the controlled surface and
has a hot junction positioned upstream in the path of the air
stream moving over the controlled surface and a cold junction
positioned downstream in the path of the air stream. This
arrangement provides defogging, defrosting or condensate
evaporation for the controlled surface, while the temperature in
the climate-controlled space is not appreciably altered, and at
least some amount of moisture is removed from the air stream by the
thermoelectric device.
Inventors: |
Taras; Michael F.;
(Fayetteville, NY) ; Lifson; Alexander; (Manlius,
NY) ; Lord; Richard G.; (Murfreesboro, TN) |
Correspondence
Address: |
CARLSON, GASKEY & OLDS, P.C.
400 WEST MAPLE ROAD, SUITE 350
BIRMINGHAM
MI
48009
US
|
Assignee: |
CARRIER CORPORATION
Syracuse
NY
|
Family ID: |
40718007 |
Appl. No.: |
12/675997 |
Filed: |
December 3, 2007 |
PCT Filed: |
December 3, 2007 |
PCT NO: |
PCT/US2007/086232 |
371 Date: |
March 2, 2010 |
Current U.S.
Class: |
62/3.4 |
Current CPC
Class: |
H05B 3/84 20130101; F25D
21/04 20130101; F25B 21/02 20130101 |
Class at
Publication: |
62/3.4 |
International
Class: |
F25B 21/02 20060101
F25B021/02 |
Claims
1. A thermoelectric device and controlled surface combination
wherein: said thermoelectric device provides one of or a
combination of defogging, defrosting or condensate evaporation for
the controlled surface.
2. The combination as set forth in claim 1, wherein said
thermoelectric device and said controlled surface are positioned
within a climate-controlled environment.
3. The combination as set forth in claim 2, wherein a hot junction
of said thermoelectric device is positioned in an air stream prior
to the air stream having contact with said controlled surface.
4. The combination as set forth in claim 3, wherein a cold junction
of said thermoelectric device is also positioned in the air stream
but downstream along the controlled surface.
5. The combination as set forth in claim 3, wherein the air stream
is an air curtain.
6. The combination as set forth in claim 2, wherein said
climate-controlled environment is one of a refrigerated enclosure
and an air conditioned space.
7. The combination as set forth in claim 2, wherein said
climate-controlled environment is one of a stationary type and a
mobile type.
8. The combination as set forth in claim 1, wherein said controlled
surface is one of a glass door, a window and a mirror.
9. The combination as set forth in claim 1, wherein said
thermoelectric device is an add-on device.
10. The combination as set forth in claim 1, wherein said
thermoelectric device is incorporated into a controlled surface
structure.
11. The combination as set forth in claim 1, wherein said
thermoelectric device is actuated on demand.
12. The combination as set forth in claim 11, wherein said
thermoelectric device is actuated based on at least one of a timer
and a humidity sensor feedback.
13. The combination as set forth in claim 1, wherein a power supply
for said thermoelectric device is an adjustable power supply
allowing for variable amounts of heating and cooling respectively
provided at a hot junction and at a cold junction of the
thermoelectric device.
14. The combination as set forth in claim 2, wherein the polarity
of said thermoelectric device is reversed to selectively assist in
cooling.
15. A method of operating a thermoelectric device and controlled
surface combination including the steps of: (a) providing one of or
a combination of defogging, defrosting or condensate evaporation
for the controlled surface by positioning a hot junction of the
thermoelectric device at desired locations.
16.-25. (canceled)
Description
BACKGROUND OF THE INVENTION
[0001] This application relates to the use of a thermoelectric
cooler for providing defogging or defrosting of cold surfaces
associated with a climate-controlled space, while not appreciably
affecting conditions in the climate-controlled space.
[0002] Various enclosure and cabinet structures include surfaces
that may be transparent or reflective and typically need to
maintain this transparency or reflection functionality over a
lifetime, particularly during air conditioning or refrigeration
equipment operation. As an example, in grocery stores, items are
often displayed in refrigerated cases. In a refrigerated case, a
glass door typically seals an enclosed refrigerated space from the
outside environment, and at the same time, allows for the content
of the refrigerated case to be displayed and be accessible. Cooled
air is circulated within the climate-controlled space of the
refrigerated case. The door faces the hotter, and typically more
humid outside environment on one face, and the cold or refrigerated
air of the enclosure on its other face. In fact, an air curtain is
often delivered along the inner face of the door to prevent
intrusion of the outside air, for instance, during periods of time
when the door is opened. Although the glass doors of the
refrigerated cases are typically well insulated, frequent opening
of the doors, as well as respiration of the produce inside the
refrigerated case, can lead to fogging of the glass doors, which is
highly undesirable.
[0003] Various other transparent or reflective cold surfaces
associated with climate-controlled spaces may experience a similar
problem. For example, windows or mirrors in stationary
applications, such as bottle coolers, wending machines,
merchandisers, bathrooms, etc., and mobile applications, such as
commercial and personal vehicles, mobile refrigerators, etc., can
become fogged. Similarly, some of these type surfaces can be
exposed to frost.
[0004] One option which has been recently proposed for
incorporation into refrigerant systems is the use of thermoelectric
coolers. The thermoelectric cooler essentially takes advantage of
specific thermoelectric properties of dissimilar semiconductor
materials and is based on two phenomena--the Peltier effect and
Seebeck effect, concurrently taking place during operation of the
thermoelectric device. The Peltier effect is associated with the
release or absorption of a finite heat flux at the junction of two
electrical conductors, made from different materials and kept at
constant temperature, at the presence of electric current.
Similarly, the Seebeck effect is related to the same arrangement,
where the two junctions are maintained at different temperatures,
which would create a finite potential difference, and an
electromotive force that would drive an electric current in the
closed-loop electric circuit.
[0005] The Peltier and Seebeck effects are presented simultaneously
in the thermoelectric cooler that is preferably made from materials
that have dissimilar absolute thermoelectric powers. The finite
electric current passing through the two junctions triggers two
heat transfer interactions with two cold and hot reservoirs kept at
different temperatures. For steady thermoelectric cooler operation,
heat fluxes associated with the two junctions should have opposite
signs. If the external system maintains potential difference and
drives electric current against this difference, the two junction
system becomes a thermoelectric cooling device.
[0006] A typical thermoelectric cooler consists of an array of
P-type and N-type semiconductor elements that act as the two
dissimilar conductors. The P-type material has an insufficient
number of electrons and the N-type material has extra electrons.
These electrons in the N-type material and so-called "holes" in the
P-type material, in addition to carrying an electric current,
become a transport media to move the heat from the cold junction to
the hot junction. The heat transport rate depends on the current
passing through the circuit and the number of moving electron-hole
couples. As an electric current is passed through one or more pairs
of P-N elements, there is a decrease in temperature at the cold
junction resulting in the absorption of heat from the object to be
cooled. The heat is carried through the thermoelectric cooler by
electron transport and released at the hot junction as the
electrons move from a high to a low energy state.
[0007] Although the thermoelectric devices are inherently
irreversible, since heat and electric current must flow through the
circuit during their operation, they do not have moving parts that
makes them extremely reliable and quiet.
[0008] Thermoelectric devices have not been applied to providing
defogging or defrosting of cold surfaces associated with a
climate-controlled space, to address the problems mentioned above,
while not appreciably affecting conditions in the
climate-controlled space.
SUMMARY OF THE INVENTION
[0009] In a disclosed embodiment of this invention, a controlled
surface having a direct contact with a flow of cold air circulating
within a climate-controlled space is provided. Air conditioning or
refrigeration equipment supplies the flow of cold air to the
climate-controlled space. A thermoelectric device is associated
with the controlled surface and maintains it without formation of
fog, frost or condensate. The controlled surface may be
predominantly transparent or reflective and will sustain these
properties during air conditioning or refrigeration equipment
operation without fogging or frosting. On the other hand, the
controlled surface may be made of conventional construction
materials, such as aluminum, steel or plastic, and will not allow
formation of any condensate to cause dripping and wet spot
initiation in undesired locations within the climate-controlled
space.
[0010] A thermoelectric device associated with the controlled
surface is located within the climate-controlled space, with its
hot junction positioned in the path of the airflow, and provides
defogging, defrosting or condensate evaporation for the controlled
surface. A cold junction of the thermoelectric device may be
positioned downstream of the hot junction on the path of the
airflow to reduce the air temperature towards its original value
and relieve the air stream from at least some amount of moisture.
This condensate collected on the cold junction is directed to a
drain pan and removed from the climate-controlled space, while the
controlled surface is defogged, defrosted or dried out. This
defogging or defrosting functionality is provided by the
thermoelectric device without interruption of the cooling mode of
operation.
[0011] A thermoelectric device may be continuously operated or it
may be activated on demand, for instance, based on a timer setting
or a sensor feedback. Such sensors are generally known in the
industry and could be of a chilled mirror type, capacitance type,
resistance type or any other type. Furthermore, a thermoelectric
device may be provided with a variable power supply, and therefore
various amounts of heating and cooling can be transferred
respectively by a hot junction and a cold junction to the passing
airflow, for instance, by varying voltage to the power supply, in
order to adjust thermoelectric device operation to variable
environmental conditions.
[0012] A thermoelectric device and its junctions may be
incorporated into the controlled surface structure or may be
applied as an add-on device.
[0013] If a power supply polarity for a thermoelectric device is
reversed, the hot junction and the cold junction are swapped. This
in turn allows for additional cooling to be provided by the cold
junction of the thermoelectric device to the associated controlled
surface.
[0014] This invention can be applied to any transparent or
reflective controlled surface, such as glass doors, windows or
mirrors, or any other general purpose controlled surface positioned
within the climate-controlled environment. These and other features
of the present invention can be best understood from the following
specification and drawings, the following of which is a brief
description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 schematically shows a refrigerated enclosure
incorporating the present invention.
[0016] FIG. 2 is an enlarged view of a portion of the FIG. 1
refrigerated enclosure.
[0017] FIG. 3 shows a generic representation of a controlled
surface incorporating the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0018] FIG. 1 shows a refrigerated enclosure 20 incorporating a
glass door 22 allowing access to the refrigerated produce as well
as providing a transparency function for a consumer to observe the
content of the refrigerated enclosure 20. The refrigerated
enclosure 20 may include various construction elements such as
shelves 24 and the like. Cold air is circulated within the
climate-controlled space of the refrigerated enclosure 20 to
provide cooling to the produce that may be placed inside the
refrigerated enclosure 20. In addition, an air curtain is provided
along the glass door 22 to prevent intrusion of the outside air as
well as escape of the cold air to the ambient environment during
the door openings.
[0019] A return air duct 18 delivers air from the
climate-controlled space of the refrigerated enclosure 20 to a
refrigeration system heat accepting heat exchanger, such as an
evaporator 30. The air then returns through a return air duct 32
and through vents 36 and 37 into the climate-controlled space of
the refrigerated enclosure 20. The vent 37 is generally positioned
to provide the air curtain 26. The evaporator 30 is incorporated
within a refrigeration system including at least basic components
such as a heat rejecting heat exchanger, a compressor, an expansion
device and a pair of air-moving devices associated with heat
rejection heat exchanger and evaporator 30. The refrigeration
system may be an integral component of the refrigerated enclosure
20 or may be of a slide-in configuration. An air-moving device,
such as fan 28, associated with and typically positioned downstream
of the evaporator 30, provides cold airflow to the
climate-controlled space of the enclosure 20 that is cooled and
often dehumidified while passing through the evaporator 30.
[0020] The air curtain 26 is thus typically at the same cold
temperature as the air circulated within the interior of the
refrigerated enclosure 20. The glass door 22 has its outer face
exposed to the ambient environment 100 and its inner face in
contact with the air curtain 26. Typically, the air curtain 26 has
much lower temperatures and moisture content than the ambient
environment 100. Therefore, it is typical that the glass door 22
can become fogged, for instance, during the door openings. The
glass door 22 may also become fogged due to respiration of the
produce placed within the refrigerated enclosure 20.
[0021] The present invention positions a thermoelectric device 44
associated with the glass door 22 and the air curtain 26 within the
climate-controlled space of the refrigerated enclosure 20 such as
the hot junction 38 of the thermoelectric device 44 is in the path
of the air leaving the vent 37 and before it flows over the glass
door 22. Due to heat transfer interaction between the curtain air
stream leaving the vent 37 and the hot junction 38 of the
thermoelectric device 44, the air curtain 26 will be at a higher
temperature than the rest of the air circulating within the
interior of the refrigerated enclosure 20. Therefore, the warmer
air of the air curtain 26 will be able to absorb moisture that
could accumulate on the interior face of the glass door 22 in the
form of fog, condensate or frost. As a result, the transparency
function for the glass door 22 will be maintained, as desired.
[0022] The cold junction 40 of the thermoelectric device 44 is
positioned near the end of the air path of the air curtain 26, and
will serve to cool the air toward the original temperature, as well
as dehumidify the air, as it returns to flow through the evaporator
30. The condensate removed from the air stream by the cold junction
40 of the thermoelectric device 44 is collected in a drain pan 45
and then removed from the refrigerated enclosure 20.
[0023] The airflow in the air curtain 26 over the hot junction 38
is shown in detail in FIG. 2. It has to be pointed out that both
the hot junction 38 and the cold junction 40 of the thermoelectric
device 44 are shown schematically and may have any shape or
configuration. For instance, to enhance heat transfer, the hot
junction 38 and the hot junction 40 may have airflow channels of
any suitable cross-section, extended secondary heat transfer
surface, such as heat transfer fins or ribs, and heat transfer
enhancement elements, such as louvers or boundary layer disruptors.
Generally, these heat transfer enhancement elements are known in
the art. Further, the cold junction 40 may have incorporated
condensate drainage paths in the form of troughs or valleys that
may be shielded from the airflow to prevent condensate carryover.
Further, elements of the thermoelectric device 44, such as the hot
junction 38 and the cold junction 40, may be attached to the
structure of the glass door 22 or may be even integrated into the
door structure, for instance, in the form of lamination positioned
close or at the inner face of the glass door 22.
[0024] It should be understood that the thermoelectric device 44
can provide defogging or defrosting functionality without
interruption of the cooling mode of operation for the refrigeration
unit associated with the refrigerated enclosure 20. Moreover, the
thermoelectric device 44 may be continuously operated or it may be
activated on demand, for instance, based on a timer setting or a
sensor feedback. Such sensors are generally known in the industry
and could be of a chilled mirror type, capacitance type, resistance
type or the like. Furthermore, a thermoelectric device may be
provided with a variable power supply, and therefore various
amounts of heating and cooling can be transferred respectively by a
hot junction and a cold junction to the passing airflow, for
instance, by varying voltage to the power supply, in order to
adjust thermoelectric device operation to variable environmental
conditions. Such variable environmental conditions may be caused,
for instance, by less or more frequent door openings, higher or
lower respiration items placed into refrigerated enclosure and
changing ambient conditions.
[0025] Moreover, if a power supply polarity for a thermoelectric
device 44 is reversed, the hot junction 38 and the cold junction 40
will be swapped. This in turn allows for additional cooling to be
provided by the cold junction (now 38) of the thermoelectric device
44 to the associated controlled surface, such as the glass door 22,
and to the entire climate-controlled environment of the
refrigerated enclosure 20. This mode of operation could be executed
during the periods of time when defogging or defrosting of the
glass door 22 is not required. The heat generated by the hot
junction (now 40) in this mode of operation, will be removed by the
refrigeration unit associated with the refrigerated enclosure
20.
[0026] As shown in FIG. 3, rather than the glass door 22, other
controlled surfaces 46 associated with the thermoelectric device 44
may benefit from the positioning along the path of the airflow
moving over a hot junction 48, and then over the cool junction 50,
in sequence. Surfaces such as windows, glass partitions and
separators or mirrors in stationary or transport applications can
benefit from this invention. Also, any general purpose controlled
surface 46 positioned within the climate-controlled environment
that tends to accumulate condensate, fog or frost can benefit from
the invention. Some examples may include, but are not limited to,
windows in buildings, mirrors in the bathrooms, glass partitions in
the refrigerated displays, windows and mirrors in the cars, shelves
in the merchandisers and many others. In addition, in appropriate
circumstances, this invention can be utilized to defrost or remove
condensate from the controlled surface 46.
[0027] While several embodiments and applications are disclosed, a
worker of ordinary skill in this art would recognize that the
disclosed applications are exemplary and many other applications
could benefit from the disclosed invention. For that reason, the
following claims should be studied to determine the true scope and
content of this invention.
* * * * *