U.S. patent application number 14/132366 was filed with the patent office on 2014-06-26 for refrigerator with no-frost freezer.
This patent application is currently assigned to WHIRLPOOL CORPORATION. The applicant listed for this patent is WHIRLPOOL CORPORATION. Invention is credited to CAROLINA BIOTTI, RAMEET SINGH GREWAL, MATTEO LUCIANO VANELLI.
Application Number | 20140174100 14/132366 |
Document ID | / |
Family ID | 47603057 |
Filed Date | 2014-06-26 |
United States Patent
Application |
20140174100 |
Kind Code |
A1 |
BIOTTI; CAROLINA ; et
al. |
June 26, 2014 |
REFRIGERATOR WITH NO-FROST FREEZER
Abstract
A refrigeration appliance comprises a freezer compartment in
which air cooled by an evaporator is circulated by a fan and a
thermoelectric device having a hot side in heat exchange
relationship with the evaporator or with the freezer compartment
and a cold side in heat exchange relationship with air within at
least a portion of the freezer compartment in order to reduce
temperature oscillations in the freezer compartment or in said
portion thereof during evaporator defrost cycle.
Inventors: |
BIOTTI; CAROLINA;
(Cassinetta, IT) ; GREWAL; RAMEET SINGH; (Pune,
IN) ; VANELLI; MATTEO LUCIANO; (Cassinetta,
IT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
WHIRLPOOL CORPORATION |
Benton Harbor |
MI |
US |
|
|
Assignee: |
WHIRLPOOL CORPORATION
Benton Harbor
MI
|
Family ID: |
47603057 |
Appl. No.: |
14/132366 |
Filed: |
December 18, 2013 |
Current U.S.
Class: |
62/3.4 ;
62/3.6 |
Current CPC
Class: |
F25B 2321/0252 20130101;
F25B 2321/023 20130101; F25D 2400/34 20130101; F25D 17/042
20130101; F25D 21/14 20130101; F25D 21/04 20130101; F25D 25/028
20130101; F25D 2317/04131 20130101; F25D 21/06 20130101; F25D
2317/04111 20130101; F25B 21/02 20130101 |
Class at
Publication: |
62/3.4 ;
62/3.6 |
International
Class: |
F25B 21/02 20060101
F25B021/02 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 20, 2012 |
EP |
12198390.2 |
Claims
1. Refrigeration appliance comprising: a freezer compartment in
which air cooled by an evaporators is circulated by a fan; at least
one thermoelectric device having a hot side in thermal
communication with the evaporator and a cold side in thermal
communication with air within at least a portion of the freezer
compartment in order to reduce temperature oscillations the portion
during evaporator defrost.
2. Refrigeration appliance according to claim 1, wherein the
portion of the freezer compartment is defined by a box-shaped
sub-compartment.
3. Refrigeration appliance according to claim 1, further comprising
a water tray disposed within the freezer compartment, wherein the
hot side of the thermoelectric device is also in thermal
communication with the water tray for keeping water in a liquid
state in order to control relative humidity within the freezer
compartment.
4. Refrigeration appliance according to claim 3, further comprising
a second thermoelectric device, wherein the hot side in thermal
communication with the water tray belongs to the second
thermoelectric device.
5. Refrigeration appliance according to claim, further comprising
an auxiliary heater for defrost.
6. Refrigeration appliance according to claim 4, wherein the second
thermoelectric device placed in a sub-compartment contained within
the freezer compartment and containing the water tray.
7. Refrigeration appliance according to claim 6, wherein the
sub-compartment comprises an auxiliary fan in order to define an
air flow on water tray.
8. Refrigeration appliance according to claim 7, wherein the
sub-compartment comprises an internal wall defining an air plenum
with apertures for the air flow.
9. Refrigeration appliance according to claim 6, wherein the second
thermoelectric device comprises a cold side in thermal
communication with a metal shelf disposed above the water tray.
10. Method for decreasing freezing burns in food items contained in
a freezer compartment comprising: heating the evaporator (12)
during a defrost phase with the help of a hot side of a
thermoelectric device; utilizing a cold side of the thermoelectric
device to reduce temperature oscillations within the freezer
compartment.
11. Method according to claim 10, further comprising the step of
controlling relative humidity within the freezer compartment
through the use of hot side of the thermoelectric device in thermal
communication with a quantity of water disposed within a water tray
to maintain the water in the water tray in a liquid state.
12. Method according to claim 10, further comprising the step of
placing food items within a sub-compartment which does not contain
the hot side of the thermoelectric device and contains the cold
side of the thermoelectric device.
13. A refrigerator comprising: an evaporator; a freezer
compartment; a water reservoir disposed in the freezer compartment
containing a quantity of water in liquid state; a first
thermoelectric device comprising a hot side and a cold side,
wherein the hot side of the first thermoelectric device is in
thermal communication with the evaporator and a cold side in
thermal communication with the freezer compartment; a second
thermoelectric device comprising a hot side and a cold side,
wherein the hot side is in thermal communication with the water
reservoir;
14. The refrigerator of claim 13, wherein the freezer compartment
further comprises a subcompartment.
15. The refrigerator of claim 14, wherein the subcompartment
further comprises a fan configured to force air over the quantity
of water in the water reservoir.
16. The refrigerator of claim 15, wherein the subcompartment
further comprises apertures configured to allow air to pass between
the fan and the water reservoir.
17. The refrigerator of claim 14, wherein the water reservoir is
disposed within the subcompartment.
18. The refrigerator of claim 13, further comprising a metal shelf
disposed above the water reservoir.
19. The refrigerator of claim 18, wherein the cold side of the
second thermoelectric device is in thermal communication with the
metal shelf.
20. The refrigerator of claim 13, further comprising an auxiliary
heater configured to activate when the refrigerator enters a
defrost mode.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application claims priority to EP 12198390.2, filed on
Dec. 20, 2012, entitled "Refrigerator with no-frost freezer," the
disclosure of which is hereby incorporated herein by reference in
its entirety.
BACKGROUND OF THE DISCLOSURE
[0002] The present invention relates to a refrigeration appliance
comprising a freezer compartment in which air cooled by an
evaporator is circulated by a fan. These refrigeration appliances,
known also as no-frost refrigerators, may have the evaporator
within the freezer compartment itself or in a different "ad-hoc"
compartment.
[0003] It is well known in the art of freezers the problems related
to defects of frozen food items. In particular, when spoiling
caused by freezing occurs, food surface is characterized by opaque
dehydrated areas or spots which show a decrease of original color.
Moreover such changes in food appearance are linked to the presence
of frost formation on food surface or internal food packaging. The
main responsible for these changes is moisture migration occurring
during storage. In fact, freezer temperature is not constant and
such fluctuation causes changes into air freezer temperature and so
air vapor pressure. In case of significant temperature
fluctuations, when temperature decreases the water pressure of air
surrounding food (that is packaging headspace) is lower than the
one of the ice on food surface so that ice sublimates from food
surface leading to opaque dehydrated areas on food called "freezing
burns". Freezer burns increase oxygen contact with the food surface
area due to the formation of tiny cavities left behind the
sublimated ice and raise oxidative reactions that alter color
(discoloration that is brown spots on red meat), texture and
flavor. After leaving the food surface, moisture condensates on
food packaging turning into frost. When temperature increases, only
part of the moisture diffuse back to the surface of food. In no
frost refrigerators every defined period of time (for instance
every 72 hours) it is planned an automatic evaporator defrost for
about 15 minutes to a half hour. The cycle can be controlled by an
electric or electronic timer, as well as by mechanical device such
as a bi-metal plate. This procedure will support consumer in not
performing manually defrost hence the energy consumption doesn't
increase with time (due to the insulation effect of frost on
evaporator). The defrost heater is switched off when the
temperature on the evaporator is higher than 0.degree. C.,
including a safety margin to ensure that the entire evaporator has
been defrosted. During defrost "on" cycle, the temperature in the
freezer chamber can reach temperatures significantly higher than
the one at the start of the cycle, approximately in the range from
-15.degree. C. to -5.degree. C., depending on the thermal inertia
of the cavity.
[0004] Locally, in regions of the compartment closer to the
evaporator, the temperature increase is usually more severe. As a
consequence of such temperature increase and subsequent decrease,
moisture migration from and to food changes and could leave to
surface defects.
SUMMARY OF THE DISCLOSURE
[0005] An object of the present invention is to provide a
refrigeration appliance which does not present the above drawbacks
and which improves the storing performances in storing frozen food
items.
[0006] Since the presence of freezing burns is also related to
oscillations of relative humidity in the freezer compartment, a
further object of the present invention is to provide a
refrigeration appliance which can control the relative humidity
level within the compartment.
[0007] The above objects are reached thanks to features listed in
the appended claims.
[0008] One of the main innovative feature of the present invention
is the use of a thermoelectric device inside the freezer
compartment and preferably connected in parallel with the defrost
heater when this latter is present. The thermoelectric device is
preferably positioned in the freezer back wall in order to have one
side thermally coupled to the evaporator and the other side
thermally coupled to the freezer cavity, i.e. in heat transfer
relationship with the air in the freezer cavity. The thermoelectric
device, usually a thermoelectric Peltier generator, is switched ON
during defrost phase when a current will pass through the Peltier
electrical connection leading to the creation of two temperature
conditions on the two sides. The side exposed to the evaporator is
warmed up and drives or contributes to drive the defrost action
carried out by the heater while the colder one is exposed to the
refrigerator cavity. In particular, this cold side will be the key
element in reducing temperature fluctuation of the air in the
freezer cavity. In fact, thermoelectric device will cool down air
working against the natural temperature increase given by the
combination of compressor off phase and heating element action.
Indeed the thermoelectric elements dimension should be designed and
dimensioned in order to avoid air temperature to exceed a gradient
higher than 2.degree. C. in the whole freezer cavity or, at least,
in a selected part of the freezer cavity, which will be the one
dedicated to storage of food particularly sensitive to freezer
burns. After the defrost cycle, the control system will switch off
the current to the thermoelectric device (and to the heater as
well, when present).
[0009] Another embodiment of the invention is presented, to include
the case in which the temperature difference between the two sides
of the thermoelectric module results too high. Since the efficiency
of the module is in inverse proportion to the difference in
temperature among the two sides, and since the heater could require
in some cases a significant heating effect from the hot side, this
can drive to a decrease of efficiency. In this case (assessed
according to the efficiency of the device used), the hot side can
be placed inside the freezer compartment, outside from the area
dedicated to freezing burns avoidance. The hot side will be cooled
down by the surrounding, while the cold side will work as cooling
booster for the no freezing-burns area.
[0010] According to another feature of the invention, the relative
humidity level within the freezer cavity can be maintained
accurately by fine tuning of cooling/heating done with the help of
the thermoelectric device which is used to heat water in a tray in
order to melt ice and to maintain the desired relative humidity in
the compartment. The Peltier hot side delivers heat that is used to
melt the ice in the tray and provide a source of humidity. In some
cases fan would be required to run to speed up the moisture
addition process.
[0011] Further features and advantages according to the present
invention will be clear from the following detailed description
with reference to the attached drawings in which:
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a schematic representation of how the
refrigeration appliance according to the invention works;
[0013] FIG. 2 is a cross section of a portion of a refrigeration
appliance according to a first embodiment of the present
invention;
[0014] FIG. 3 is a perspective view of a portion of a refrigeration
appliance according to a second embodiment of the invention;
and
[0015] FIG. 4 is an exploded perspective view of the embodiment
according to FIG. 3.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0016] With reference to the drawings, a refrigerator 10 comprises
a freezer compartment FZ and a fresh food compartment FC. The
freezer compartment FZ comprises an evaporator 12 which is part of
a refrigerating circuit whose only a condenser 14 is shown. The
evaporator 12 is of the no-frost type, i.e. it comprises a fan 16
and a defrosting heater 18. Both the heater 18 and the fan 16 are
controlled through a control unit 20.
[0017] According to the invention, a Peltier module 22 is mounted
on the evaporator 12. In detail, its hot side 22a is in contact
with the evaporator 12 while its cold side 22b is in heat exchange
relationship with the air flow inside the freezer compartment FZ.
The Peltier module 22 is driven through the control unit 20.
[0018] The cyclic process according to the invention is shown in
FIG. 1, where step A represents the defrost count down; step B
represents the condition when the compressor (not shown) is
switched off at the beginning of the defrost phase, in which the
heater 18 is switched on and the Peltier module 22 is switched on
too; step C represents the condition in which warm air from the
heater 18 and Peltier module hot side 22a both carry out the
defrost of the evaporator 12, and in which cold air from Peltier
module cold side 22b avoids a too high increase of air temperature
in the freezer compartment FZ; and step D represents the end of the
defrost phase (usually 30 minutes), when both heater 18 and Peltier
module 22 are switched off.
[0019] Tests carried out by the applicant have shown that by
adopting the solution according to the invention freezer burns can
be reduced or even eliminated. According to a second embodiment of
the invention, the thermoelectric device can be used not only for
heating the evaporator during the defrost phase, but also for
keeping water contained in a tray in the liquid state in order to
control relative humidity inside the freezer compartment. Of course
the same thermoelectric device 22 used in the first embodiment can
be also used for reaching the technical object according to the
second embodiment, even if a second independent Peltier module is
preferred in order to not interfere with the normal function of the
evaporator 12.
[0020] According to FIG. 3, a sub-compartment 24 shaped as a metal
box is preferably used, which is contained within the freezer
compartment FZ. The sub-compartment 24 has a door 24a and it is
also provided with fins 26 on the outside to enhance heat
transfer.
[0021] The sub-compartment 24 presents an internal wall 28 with an
upper aperture 28a for an auxiliary fan 30, and a bottom seat 28b
for a Peltier module 32 having a hot side in contact with a bent
end portion 34a of a metal tray 34 placed on the bottom of the
sub-compartment 24. The internal wall 28, which is placed at a
predetermined distance above the tray 34, defines an air plenum P
between an end wall of the sub-compartment 24 and the wall 28.
[0022] The tray 34 receives water from a water source 36 which can
be a reservoir for defrost water from evaporator 12 or water for
supplying ice maker. In order to maintain the proper humidity level
in the sub-compartment 24, water is fed to the tray 34, which may
have a level sensor in order to control water filling. The
auxiliary fan 30 drives cold air over water in the tray 24 in order
to increase relative humidity in the sub-compartment 24. By
switching on and off the auxiliary fan 30 the relative humidity can
be controlled within a narrow band.
[0023] Of course the tray 34 is also provided with a metal shelf
(not shown) above the water level for placement of frozen food
items; a plurality of metal shelves can be used as well in the
sub-compartment 24. The metal shelf may also be provided with an
extension in contact with the cold side of the Peltier module 32 in
order to cool down the whole shelf, while the hot side thereof is
in contact with the tray 34 for transferring heat to the water
contained therein and keeping it in a liquid state.
[0024] The tray 34 is also provided with an overflow conduit (not
shown). Arrows F in FIG. 3 shows air circulation in the
sub-compartment, while reference 38 shows a temperature and
humidity sensor inside the sub-compartment 24.
[0025] Of course the second embodiment according to the present
invention can be also implemented in the whole freezer compartment
FZ and not only in a sub-compartment thereof. The use of a
sub-compartment 24 is particularly advantageous for food items
placed in the freezer compartment without any packaging or
container, i.e. in cases where the food items are more subjected to
freezing burns.
[0026] According to a further embodiment (not shown), particularly
when the sub-compartment 24 does occupy only part of the freezer
compartment, in said sub-compartment 24 it is placed only the cold
side 22b of the thermoelectric device 22, while the hot side is
outside the sub-compartment 24 (which is actually the area for
avoiding freezing burns) and it is cooled down by air in the
freezer compartment FZ. This embodiment has the advantage of
increasing the efficiency of the thermoelectric device and of using
the cold side thereof as a cooling booster for the sub-compartment
24.
* * * * *