U.S. patent application number 13/652951 was filed with the patent office on 2013-04-25 for high performance refrigerator having insulated evaporator cover.
This patent application is currently assigned to THERMO FISHER SCIENTIFIC (ASHEVILLE) L.L.C.. The applicant listed for this patent is Thermo Fisher Scientific (Asheville) L.L.C.. Invention is credited to Christopher BRUCHS, Robert BRUKER, J. Antonio CONTRERAS LAFAIRE, Ralph HEGEDUS, Todd SWIFT.
Application Number | 20130098074 13/652951 |
Document ID | / |
Family ID | 47324694 |
Filed Date | 2013-04-25 |
United States Patent
Application |
20130098074 |
Kind Code |
A1 |
HEGEDUS; Ralph ; et
al. |
April 25, 2013 |
HIGH PERFORMANCE REFRIGERATOR HAVING INSULATED EVAPORATOR COVER
Abstract
A high performance refrigerator includes a cabinet with a
refrigerated interior, an insulating cover separating a portion of
the cabinet from the refrigerated interior, and a refrigeration
fluid circuit having an evaporator located within the portion of
the cabinet separated by the insulating cover from the refrigerated
interior. The refrigerator also includes a controller that commands
the refrigerator to perform a defrosting cycle when the evaporator
coil requires defrosting. This defrosting cycle includes closing
dampers in the insulating cover during the defrosting of the
evaporator coil, thereby keeping the refrigerated interior
thermally isolated from the evaporator during the defrost cycle.
The controller is also operable to stop operation of a defrost
heater when the evaporator reaches a first target temperature above
the freezing point of water, and to re-open the dampers when the
evaporator reaches a second target temperature above the freezing
point of water.
Inventors: |
HEGEDUS; Ralph; (Candler,
NC) ; BRUKER; Robert; (Biltmore Lake, NC) ;
CONTRERAS LAFAIRE; J. Antonio; (Fletcher, NC) ;
SWIFT; Todd; (Weaverville, NC) ; BRUCHS;
Christopher; (Asheville, NC) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Thermo Fisher Scientific (Asheville) L.L.C.; |
Asheville |
NC |
US |
|
|
Assignee: |
THERMO FISHER SCIENTIFIC
(ASHEVILLE) L.L.C.
Asheville
NC
|
Family ID: |
47324694 |
Appl. No.: |
13/652951 |
Filed: |
October 16, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61548795 |
Oct 19, 2011 |
|
|
|
Current U.S.
Class: |
62/80 ; 62/151;
62/156 |
Current CPC
Class: |
F25D 17/045 20130101;
F25B 2700/2117 20130101; F25D 21/08 20130101 |
Class at
Publication: |
62/80 ; 62/151;
62/156 |
International
Class: |
F25D 21/06 20060101
F25D021/06 |
Claims
1. A refrigerator, comprising: a cabinet having a refrigerated
interior; a refrigeration fluid circuit for circulating a
refrigerant, the refrigeration fluid circuit including a
compressor, a condenser, an expansion device, and an evaporator
located within the cabinet and including an evaporator coil, an
evaporator fan producing air flow through the evaporator coil, and
a defrost heater; an insulating cover separating a portion of the
cabinet containing the evaporator from the refrigerated interior,
the insulating cover including at least one damper that may open to
permit air circulation from the refrigerated interior through the
evaporator; and a controller operable to command the refrigerator
to perform the following steps when the evaporator coil requires
defrosting: stop operation of the compressor and the evaporator
fan; close the at least one damper to thermally isolate the
evaporator from the refrigerated interior; and start operation of
the defrost heater, wherein the refrigerated interior remains
thermally isolated from the evaporator during operation of the
defrost heater.
2. The refrigerator of claim 1, further comprising a temperature
sensor for detecting the temperature of the evaporator, and wherein
the controller is further operable to command the refrigerator to
perform the following steps during defrosting of the evaporator:
when the temperature sensor detects that the evaporator has reached
a first target temperature above the freezing point of water,
stopping operation of the defrost heater and allowing for any
remaining moisture to drip off the evaporator coils; starting the
compressor after the remaining moisture drips off the evaporator
coils; and when the temperature sensor detects that the evaporator
has reached a second target temperature below the freezing point of
water, opening the at least one damper and starting operation of
the evaporator fan.
3. The refrigerator of claim 2, wherein the first target
temperature is about 10.degree. C. and the second target
temperature is about -25.degree. C.
4. The refrigerator of claim 1, wherein the at least one damper
includes a first damper and a second damper, the first damper in an
open position permitting air flow into the evaporator from the
refrigerated interior, the second damper in an open position
permitting air flow from the evaporator into the refrigerated
interior.
5. The refrigerator of claim 1, wherein the insulated cover further
includes a plurality of insulated panels that collectively divide
the cabinet into an evaporator chamber and the refrigerated
interior when the at least one damper is closed.
6. The refrigerator of claim 5, wherein each of the insulated
panels is a vacuum insulated panel.
7. The refrigerator of claim 1, wherein the expansion device
includes at least one of a capillary tube or a valve.
8. The refrigerator of claim 1, wherein the refrigeration fluid
circuit further includes an accumulator operatively connected to
the evaporator and the compressor.
9. The refrigerator of claim 1, wherein the refrigeration fluid
circuit further includes a filter/dryer operatively connected to
the condenser and the expansion device.
10. The refrigerator of claim 1, wherein the controller is operable
to modify an amount of time between defrost cycles and to modify an
amount of time the defrost heater is operating during a defrost
cycle based on at least one measurable operating parameter.
11. A method of operating a refrigerator including a cabinet having
a refrigerated interior, a refrigeration fluid circuit including a
compressor, a condenser, and an evaporator located within the
cabinet and having an evaporator fan and defrost heater, the
refrigerator further including an insulating cover with at least
one damper configured to separate the evaporator from the
refrigerated interior of the cabinet, and the method comprises:
stopping operation of the compressor and the evaporator fan;
closing the at least one damper to thermally isolate the evaporator
from the refrigerated interior; and starting operation of the
defrost heater, wherein the refrigerated interior remains thermally
isolated from the evaporator during operation of the defrost
heater.
12. The method of claim 11, further comprising: when the evaporator
has reached a first target temperature above the freezing point of
water, stopping operation of the defrost heater and allowing for
any remaining moisture to drip off the evaporator coils; starting
the compressor after the remaining moisture drips off the
evaporator coils; and when the evaporator has reached a second
target temperature below the freezing point of water, opening the
at least one damper and starting operation of the evaporator
fan.
13. The method of claim 12, wherein the first target temperature is
about 10.degree. C. and the second target temperature is about
-25.degree. C.
14. The method of claim 11, wherein the at least one damper
includes a first damper and a second damper, the first damper in an
open position permitting air flow into the evaporator from the
refrigerated interior, the second damper in an open position
permitting air flow from the evaporator into the refrigerated
interior, and the first and second dampers are simultaneously
closed by the refrigerator when the operation of the evaporator fan
is stopped.
15. A method of operating a refrigerator including a cabinet having
a refrigerated interior, a refrigeration fluid circuit including a
compressor, a condenser, and an evaporator located within the
cabinet and having an evaporator fan and defrost heater, the
refrigerator further including an insulating cover with at least
one damper configured to separate the evaporator from the
refrigerated interior of the cabinet, and the method comprises:
starting the operation of the defrost heater when the at least one
damper is closed; and when the evaporator has reached a first
target temperature above the freezing point of water, stopping
operation of the defrost heater and starting operation of the
compressor; and when the evaporator has reached a second target
temperature below the freezing point of water, opening the at least
one damper and starting operation of the evaporator fan.
16. The method of claim 15, wherein the first target temperature is
about 10.degree. C. and the second target temperature is about
-25.degree. C.
17. The method of claim 15, wherein the at least one damper
includes a first damper and a second damper, the first damper in an
open position permitting air flow into the evaporator from the
refrigerated interior, the second damper in an open position
permitting air flow from the evaporator into the refrigerated
interior, and the first and second dampers are simultaneously
opened by the refrigerator when the operation of the evaporator fan
is started.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] The present application claims the priority benefit of U.S.
Provisional Patent Application No. 61/548,795 (pending), filed Oct.
19, 2011, the disclosure of which is hereby incorporated by
reference in its entirety herein.
FIELD OF THE INVENTION
[0002] The present invention relates generally to refrigerators or
freezers and, more particularly, to refrigeration systems for use
with high performance blood bank refrigerators or plasma
freezers.
BACKGROUND OF THE INVENTION
[0003] Refrigeration systems are known for use with laboratory
refrigerators and freezers of the type known as "high performance
refrigerators," which are used to cool their interior storage
spaces to relative low temperatures such as about -30.degree. C. or
lower, for example. These high performance refrigerators are used
to store blood and/or plasma, in one example.
[0004] Known refrigeration systems of this type include a single
loop circulating a refrigerant. The system transfers energy (i.e.,
heat) from the refrigerant to the surrounding environment through a
condenser, and the system transfers heat energy to the refrigerant
from the cooled space (e.g., a cabinet interior) through an
evaporator. The refrigerant is selected to vaporize and condense at
a selected temperature close to the desired temperature for the
cooled space, such that the refrigeration system can maintain the
cooled space near that selected temperature during operation.
[0005] One common problem with known refrigeration systems is that
the evaporator includes coils that tend to produce and accumulate
frost along the outer surface if any moisture is ambient within the
cooled space. If enough frost accumulation occurs, the ability of
the evaporator to remove heat from the cooled space is
detrimentally impacted. Consequently, known refrigeration systems
require a defrost cycle where the evaporator coils are heated to
remove the frost. This defrost cycle may be a manual defrost or an
automatic defrost, but both types of defrost cycles are undesirable
for various reasons.
[0006] In a manual defrost cycle, all of the products stored in the
cabinet are removed and the cooled space is left exposed to the
ambient environment to heat up the evaporator coils and melt the
frost. This cycle is undesirable because the products stored in the
cabinet need to be stored in an alternative refrigerator for the
duration of the defrost cycle, and also because the melting process
can produce a significant amount of moisture that needs to be
removed from the cabinet. In an automatic defrost cycle, the
evaporator coils are rapidly heated by a local heating unit or hot
gas flow to remove the frost, which is collected by a trough and
delivered out of the cooled space. The cooled space necessarily
undergoes a temperature spike during this automatic defrost cycle,
which can jeopardize the products stored in the cabinet.
[0007] There is a need, therefore, for a refrigerator that
substantially minimizes or eliminates a temperature spike within
the cooled space during a defrost cycle.
SUMMARY OF THE INVENTION
[0008] In one embodiment, a refrigerator includes a cabinet with a
refrigerated interior and a refrigeration fluid circuit for
circulating a refrigerant. The refrigeration fluid circuit includes
a compressor, a condenser, an expansion device, and an evaporator
located within the cabinet. The evaporator includes an evaporator
coil, an evaporator fan producing air flow through the evaporator
coil, and a defrost heater. The refrigerator also includes an
insulating cover separating a portion of the cabinet containing the
evaporator from the refrigerated interior. The insulating cover
includes at least one damper which opens to permit air circulation
from the refrigerated interior through the evaporator.
[0009] The refrigerator further includes a controller operable to
command the refrigerator to perform a series of steps defining a
defrost cycle when the evaporator coil requires defrosting. The
series of steps includes stopping operation of the compressor and
the evaporator fan, closing the at least one damper to thermally
isolate the evaporator from the refrigerated interior, and starting
operation of the defrost heater. The refrigerated interior remains
thermally isolated from the evaporator during operation of the
defrost heater.
[0010] In one aspect, the refrigerator also includes a temperature
sensor for detecting the temperature of the evaporator. The
controller operates during defrosting as follows: when the
temperature sensor detects that the evaporator has reached a first
target temperature above the freezing point of water, the defrost
heater stops. After any remaining moisture drips off the evaporator
coils, the compressor starts. When the temperature sensor detects
that the evaporator has reached a second target temperature below
the freezing point of water, the at least one damper opens and the
evaporator fan starts. In one example, the first target temperature
is about 10.degree. C. and the second target temperature is about
-25.degree. C. The controller may also be operable to perform the
defrost cycle steps as an adaptive defrost cycle, which includes
varying time periods between defrost cycles and varying lengths of
defrost cycles dependent upon multiple operating parameters.
[0011] In another embodiment of the invention, a method of
operating a refrigerator is provided, the refrigerator including a
cabinet with a refrigerated interior, a refrigeration fluid circuit
including a compressor, a condenser, and an evaporator, and an
insulating cover with at least one damper separating the evaporator
from the refrigerated interior. The method includes stopping
operation of the compressor and an evaporator fan. The at least one
damper closes to thermally isolate the evaporator from the
refrigerated interior. A defrost heater starts operation to remove
moisture from evaporator coils. The refrigerated interior remains
thermally isolated from the evaporator during operation of the
defrost heater.
[0012] In yet another embodiment, a method of operating a
refrigerator is provided, the refrigerator including a cabinet with
a refrigerated interior, a refrigeration fluid circuit including a
compressor, a condenser, and an evaporator, and an insulating cover
with at least one damper separating the evaporator from the
refrigerated interior. The method includes starting operation of a
defrost heater when the at least one damper is closed. When the
evaporator reaches a first target temperature above the freezing
point of water, the defrost heater is stopped and the compressor is
started. When the evaporator reaches a second target temperature
below the freezing point of water, the at least one damper opens
and an evaporator fan starts operating.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The accompanying drawings, which are incorporated in and
constitute a part of this specification, illustrate an embodiment
of the invention and, together with a general description of the
invention given above, and the detailed description of the
embodiment given below, serve to explain the principles of the
invention.
[0014] FIG. 1 is a perspective view of a refrigerator including an
insulating cover according to an exemplary embodiment.
[0015] FIG. 2 is a schematic representation of the refrigeration
fluid circuit used with the refrigerator of FIG. 1.
[0016] FIG. 3 is a perspective view of the insulating cover (shown
in phantom) and dampers used with the refrigerator of FIG. 1.
[0017] FIG. 4 is a perspective view of an evaporator used with the
refrigerator of FIG. 1, with some of the side panels shown in
phantom to reveal interior elements.
[0018] FIG. 5 is a cross-sectional side view of the refrigerator of
FIG. 1, with the dampers in a closed position.
[0019] FIG. 6 is a cross-sectional side view of the refrigerator of
FIG. 5, with the dampers in an open position.
[0020] FIG. 7 is a schematic diagram of the controller and damper
drive elements used with the refrigerator of FIG. 1.
[0021] FIG. 8 is a schematic flowchart illustrating an operational
sequence of a controller associated with the refrigerator of FIG.
1.
DETAILED DESCRIPTION
[0022] With reference to the figures, and more specifically to FIG.
1, an exemplary high performance refrigerator 10 according to one
embodiment of the present invention is illustrated. Although the
terms "high performance refrigerator" and "refrigerator" are used
throughout the specification, it will be understood that the
invention encompasses any type of cooling device, including a
refrigerator that comprises a freezer. The refrigerator of FIG. 1
includes a cabinet 12 for storing items that require cooling to
temperatures of about -30.degree. C. or lower, for example. The
cabinet 12 includes a cabinet housing 14 defining a generally
rectangular cross-section and a door 16 providing access into an
interior 18 of the cabinet 12. The cabinet 12 supports one or more
components that jointly define a single-stage refrigeration fluid
circuit 20 (FIG. 2) that thermally interacts with the air within
the cabinet 12 to cool the interior 18 thereof. In this regard, the
refrigeration fluid circuit 20 described in further detail below
interacts with warmed air in the interior 18 and cools this air to
maintain a desired cold temperature in the cabinet 12.
[0023] With reference to FIG. 2, details of the exemplary
refrigeration fluid circuit 20 are illustrated. The refrigeration
fluid circuit 20 includes, in sequence, a compressor 22, a
condenser 24, a filter/dryer 26, an expansion device 28, an
evaporator 30, and a suction/accumulator 32. Each of these elements
of the refrigeration fluid circuit 20 is coupled by piping or
tubing 34 configured to circulate the refrigerant 36 passing
through the refrigeration fluid circuit 20. A plurality of sensors
S.sub.1 through S.sub.5 are arranged to sense different conditions
of the fluid circuit 20 and/or properties of the refrigerant (shown
by arrows 36) at various locations within the fluid circuit 20.
Each of these sensors S.sub.1 through S.sub.5 is operatively
coupled to a controller 50 accessible through a controller
interface 52, which permits controlling of the operation of the
fluid circuit 20. It will be appreciated that more or fewer sensors
may be provided than the number shown in the exemplary embodiment
of the fluid circuit 20.
[0024] The refrigeration fluid circuit 20 is configured to
circulate the refrigerant 36 between the condenser 24 and the
evaporator 30. Generally speaking, heat energy in the refrigerant
36 is transferred to ambient air outside the cabinet 12 at the
condenser 24. Heat energy is removed from the interior 18 of the
cabinet 12 and transferred to the refrigerant 36 at the evaporator
30. Thus, circulating the refrigerant 36 through the fluid circuit
20 continuously removes heat energy from the interior 18 to
maintain a desired internal temperature, such as, for example
-30.degree. C.
[0025] The refrigerant 36 enters the compressor 22 in a vaporized
state and is compressed to a higher pressure and higher temperature
gas in the compressor 22. The fluid circuit 20 of this exemplary
embodiment also includes an oil loop 54 for lubricating the
compressor 22. Specifically, the oil loop 54 includes an oil
separator 56 in fluid communication with piping 34 downstream of
the compressor 22 and an oil return line 58 directing oil back into
the compressor 22. It will be understood that the oil loop 54 may
be omitted in some embodiments of the fluid circuit 20.
[0026] Upon leaving the compressor 22, the vaporized refrigerant 36
travels to the condenser 24. A fan 60 controlled by the control
interface 52 directs ambient air across the condenser 24 and
through a filter 62 so as to facilitate the transfer of heat from
the refrigerant 36 to the surrounding environment. The air flow
through the condenser 24 is shown by arrows in FIG. 2. The
refrigerant 36 condenses within the condenser 24 as a result of
this heat transfer. The liquid-phase refrigerant then passes
through the filter/dryer 26 and into the expansion device 28. In
this embodiment, the expansion device 28 is in the form of a
capillary tube, although it is contemplated that it could instead
take another form such as, and without limitation, an expansion
valve (not shown). The expansion device 28 causes a pressure drop
in the refrigerant 36 immediately before the refrigerant 36 enters
the evaporator 30.
[0027] In the evaporator 30, the refrigerant 36 receives heat from
the interior 18 through a plurality of evaporator coils (not shown
in FIG. 2). An evaporator fan 64 controlled by the control
interface 52 forces air flow from the interior 18 of the cabinet 12
through the evaporator coils when first and second dampers 66, 68
are opened. The first and second dampers 66, 68 are also controlled
by the control interface 52. The control of the first and second
dampers 66, 68 is further described with reference to FIG. 8,
below. By virtue of the lowered pressure and the heat transfer from
the cabinet 12, the refrigerant 36 vaporizes within the evaporator
30. The vaporized refrigerant 36 is then directed to the
suction/accumulator device 32. The suction/accumulator 32 passes
the refrigerant 36 in gaseous form to the compressor 22, while also
accumulating excessive amounts of the refrigerant 36 in liquid form
and feeding it to the compressor 22 at a controlled rate.
[0028] The refrigerant 36 used in the refrigeration fluid circuit
20 may be chosen based on several factors, including the expected
operating temperature within the cabinet 12 and the boiling point
and other characteristics of the refrigerant 36. For example, in
refrigerators with an expected cabinet temperature of about
-30.degree. C., an exemplary refrigerant 36 suitable for the
presently described embodiment includes refrigerants commercially
available under the respective designations R404A. Moreover, in
specific embodiments, the refrigerant 36 may be combined with an
oil to facilitate lubrication of the compressor 22. For example,
and without limitation, the refrigerant 36 may be combined with
Mobil EAL Arctic 32 oil. It will be understood that the precise
arrangement of the components illustrated in the figures is
intended to be merely exemplary rather than limiting.
[0029] With reference to FIGS. 3-6 and in particular FIG. 3, the
refrigerator 10 includes an insulated cover 70 that divides the
interior 18 of the cabinet 12 into an evaporator portion 72 and a
refrigerated portion 74. The insulated cover 70 is coupled to one
or more of the top wall 76, the side walls 78 (including a rear
wall 78), and/or the bottom wall 80 collectively defining the
cabinet housing 14. More particularly, the insulated cover 70 is
coupled to the top wall 76 and the side walls 78 of the cabinet
housing 14 to thermally isolate the evaporator portion 72 from the
heat energy within the interior 18 as that heat energy rises within
the interior 18 of the cabinet 12. The insulated cover 70 of the
illustrated embodiment includes a vertical panel portion 82
extending downwardly from the top wall 76 of the cabinet housing 14
and a horizontal panel portion 84 extending between the vertical
panel portion 82 and the side walls 78 of the cabinet housing 14.
The vertical panel portion 82 and the horizontal panel portion 84
are formed from one or more thermally insulating panels, such as
the hollow vacuum insulated panel 86 shown in FIG. 3. It will be
understood that other types of insulating panels may be used in
other embodiments of the invention, including but not limited to
foam-based panels.
[0030] As shown in FIG. 3, the evaporator portion 72 is defined as
a generally rectilinear space by the vertical panel portion 82, the
horizontal panel portion 84, the side walls 78, and the top wall
76. The evaporator 30 mounts into a divider panel 88 located
generally centrally within the evaporator portion 72 so as to
divide the evaporator portion 72 into an inlet side 90 and an
outlet side 92. The divider panel 88 is another vacuum insulated
panel or foam-based insulated panel in this embodiment, although it
will be understood that other types of dividing panels may also be
used in other embodiments. The horizontal panel portion 82 of the
insulated cover 70 includes an inlet aperture 94 on the inlet side
90 of the divider panel 88 and an outlet aperture 96 on the outlet
side 92 of the divider panel 88. The first damper 66 includes an
insulated panel that is operable to rotate to open or close flow
through the inlet aperture 94 between the inlet side 90 and the
refrigerated interior 18 of the cabinet 12. Similarly, the second
damper 68 includes an insulated panel that is operable to rotate to
open or close flow through the outlet aperture 96 between the
outlet side 92 and the refrigerated interior 18 of the cabinet 12.
Thus, the first and second dampers 66, 68 may be operated to enable
flow through the evaporator 30.
[0031] Also shown in FIG. 3, the first and second dampers 66, 68
are operatively connected to a damper drive mechanism 100 such as
respective first and second servo motors 102, 104 and first and
second drive shafts 106, 108. The control and operation of the
damper drive mechanism 100 is further described in detail with
reference to FIG. 7 below. It will be understood that the first and
second drive shafts 106, 108 may be connected by a conventional
drive linkage (not shown) in some embodiments so that only a single
servo motor would be required to open and close the first and
second dampers 66, 68. In this regard, the first and second dampers
66, 68 are typically opened (or closed) simultaneously so that flow
is enabled through the evaporator portion 72 and the evaporator
30.
[0032] Turning to FIG. 4, the evaporator 30 is shown in further
detail. To this end, the evaporator 30 includes an evaporator
housing 110 enclosing an evaporator coil 112 extending in a
serpentine manner across a width of the evaporator 30. The
evaporator coil 112 is operatively connected to the piping 34 of
the refrigeration fluid circuit 20, which carries liquid-phase
refrigerant to the evaporator coil 112 and removes vaporized and
any remaining liquid-phase refrigerant from the evaporator coil
112. The evaporator fan 64 is mounted along the evaporator housing
110 at the inlet side 90 of the evaporator portion 72 so as to
actuate air flow through the evaporator housing 110 and through the
evaporator coil 112. After flowing through the evaporator coil 112,
cooled air exits the evaporator housing 110 and enters the outlet
side 92 of the evaporator portion 72.
[0033] The evaporator 30 also includes a defrost heater 114 for
removing frost build up on the evaporator coil 112 as needed or on
a regular basis. The defrost heater 114 is shown mounted adjacent
to the evaporator coil 112 in FIGS. 4 and 5, but it will be
appreciated that the defrost heater 114 may be mounted anywhere
within the evaporator housing 110. The defrost heater 114 is
operated by the controller 50 and the control interface 52
previously described with reference to FIG. 2 to heat up the
evaporator coil 112 and melt any frost. The evaporator housing 110
further includes a drip pan 116 located below the evaporator coil
112 and configured to collect and dispose of melted frost to a
location outside the refrigerator 10. In this regard, the drip pan
116 is generally angled from a horizontal orientation so that
moisture dripping from the evaporator coil 112 automatically flows
to a moisture outlet (not shown).
[0034] With reference to FIGS. 5 and 6, the refrigerator 10 further
includes an upper compartment 120 located above the top wall 76 of
the cabinet housing 14. The upper compartment 120 contains elements
of the refrigeration fluid circuit 20 other than the evaporator 30
(e.g., the compressor 22, the condenser 24, etc.), thereby removing
most of the space-using or heat generating components from the
interior 18 of the cabinet 12. These other elements located within
the upper compartment 120 are not shown in FIGS. 5 and 6, although
they are schematically shown in FIG. 2. The piping 34 for the
refrigerant 36 extends through the top wall 76 to deliver
refrigerant between the components in the upper compartment 120 and
the evaporator 30 in the cabinet 12.
[0035] FIGS. 5 and 6 also illustrate two operating states for the
refrigerator 10. More particularly, in FIG. 5 the first and second
dampers 66, 68 are closed, which thermally isolates the evaporator
portion 72 from the refrigerated portion 74. The evaporator fan 64
is generally inactive when the first and second dampers 66, 68 are
closed because air cannot be circulated into and out of the
evaporator portion 72. The defrost heater 114 is only operated in
this operational state of the refrigerator 10 so that substantially
all of the heat energy generated by the defrost heater 114 remains
within the evaporator portion 72 during a defrost cycle or process.
To this end, the temperature spike within the refrigerated portion
74 of the interior 18 is reduced or eliminated during the defrost
cycle. In contrast, the first and second dampers 66, 68 are open in
FIG. 6 so that air from the refrigerated portion 74 may flow
through the evaporator 30 and the evaporator coil 112 for cooling.
The air flow actuated by the evaporator fan 64 is schematically
shown in FIG. 6 by arrows 122. Thus, relatively warm air enters the
evaporator portion 72 through the inlet aperture 94 and relatively
cold air exits the evaporator portion 72 through the outlet
aperture 96 in this operating state of the refrigerator 10.
[0036] FIG. 7 schematically illustrates the control and actuation
mechanisms for the first and second dampers 66, 68. More
specifically, the first and second dampers 66, 68 are connected to
the damper drive mechanism 100, which is coupled to the controller
50. As understood in the art, the controller 50 may include at
least one central processing unit ("CPU") coupled to a memory. Each
CPU is typically implemented in hardware using circuit logic
disposed on one or more physical integrated circuit devices or
chips. Each CPU may be one or more microprocessors,
micro-controllers, field programmable gate arrays, or ASICs, while
memory may include random access memory (RAM), dynamic random
access memory (DRAM), static random access memory (SRAM), flash
memory, and/or another digital storage medium, and also typically
implemented using circuit logic disposed on one or more physical
integrated circuit devices, or chips. As such, memory may be
considered to include memory storage physically located elsewhere
in the refrigerator 10, e.g., any cache memory in the at least one
CPU, as well as any storage capacity used as a virtual memory,
e.g., as stored on a mass storage device such as a hard disk drive,
another computing system, a network storage device (e.g., a tape
drive), or another network device coupled to the controller 50
through at least one network interface by way of at least one
network. The computing system, in specific embodiments, is a
computer, computer system, computing device, server, disk array, or
programmable device such as a multi-user computer, a single-user
computer, a handheld computing device, a networked device
(including a computer in a cluster configuration), a mobile
telecommunications device, a video game console (or other gaming
system), etc. The controller 50 includes at least one serial
interface to communicate serially with an external device, such as
the damper drive mechanism 100, for example. Thus, the controller
50 functions to actuate operation of the damper drive mechanism
100.
[0037] As previously described, the damper drive mechanism 100 may
be one or more servo motors 102, 104 connected to the first and
second dampers 66, 68 via corresponding drive shafts 106, 108.
However, the damper drive mechanism 100 may include other types of
actuation mechanisms and devices in other embodiments. For example,
the damper drive mechanism 100 may be hydraulically driven,
pneumatically driven, or mechanically driven such as by various
types of motors. The damper drive mechanism 100 may be configured
to rotate the dampers 66, 68 between open and closed positions as
shown in the illustrated embodiment, but it will be understood that
the damper drive mechanism 100 may alternatively slide or otherwise
move the dampers 66, 68 in non-rotational manners as well.
[0038] An exemplary operation of the refrigerator 10 is shown
schematically in the flowchart of FIG. 8. In this regard, the
controller 50 is operable to command the refrigerator 10 to execute
the steps of the method 200 shown in that Figure. To this end, the
controller 50 determines whether a defrost cycle is necessary at
step 202. For example, in a time-based defrost cycle, the
controller 50 at step 202 determines whether a predetermined amount
of time has elapsed since the most recent defrost cycle. If so,
then the controller 50 begins the defrost cycle at step 204. If
not, then the controller 50 continues to wait and periodically
checks to see if the predetermined amount of time has elapsed. In
one example, the refrigerator 10 may defrost every six hours, in
which case the predetermined amount of time would be six hours.
Alternatively, the controller 50 may be operable to perform
adaptive defrosts that are spaced by varying amounts of time
depending on operational characteristics measured between defrost
cycles, as described in further detail below.
[0039] Returning to FIG. 8, when a defrost cycle is required to
remove frost build up from the evaporator coil 112, the controller
50 stops the compressor 22 and the evaporator fan 64 at step 204.
This stops refrigerant flow through the refrigeration fluid circuit
20 and the evaporator 30 and also stops air flow through the
evaporator 30. The controller 50 then closes the first and second
dampers 66, 68 at step 206 to thermally isolate the evaporator
portion 72 from the refrigerated portion 74 of the cabinet 12. With
the evaporator portion 72 thermally isolated from the remainder of
the cabinet 12, the controller 50 starts operation of the defrost
heater 114 at step 208. The defrost heater 114 warms the evaporator
30 and the evaporator coil 112 to melt frost and cause the moisture
to drip onto the drip pan 116 for removal from the evaporator 30.
The operational state of the refrigerator 10 at this point is shown
in FIG. 5.
[0040] One of the sensors S.sub.3 connected to the evaporator 30
may be configured to measure the temperature of the evaporator 30.
At step 210, the controller 50 determines whether that sensor
S.sub.3 is reading a temperature of the evaporator 30 which is at
or exceeding a first target temperature above the freezing point of
water (0.degree. C.). In one example, this first target temperature
may be about 10.degree. C. If the evaporator 30 is not at or above
that first target temperature, then the controller 50 continues to
operate the defrost heater 114 to remove frost from the evaporator
coil 112. If the evaporator 30 is at or above the first target
temperature, then the controller 50 turns off the defrost heater
114 and allows a set period of time for additional moisture to drip
off the evaporator coil 112 onto the drip pan 116 at step 212.
After this "drip time" has occurred, the controller 50 starts the
compressor 22 to cause refrigerant flow through the evaporator 30
again at step 214, thereby cooling the evaporator portion 72.
[0041] At step 216, the temperature sensor S.sub.3 measures the
temperature of the evaporator 30 and the controller 50 determines
whether this temperature is at or below a second target temperature
below the freezing point of water (0.degree. C.). In one example,
this second target temperature may be about -25.degree. C. If the
evaporator 30 is not at or below the second target temperature, the
controller 50 continues to operate the compressor 214 to cool the
evaporator 30. Once the controller 50 determines that the
evaporator 30 is at or below the second target temperature, then
the controller 50 opens the first and second dampers 66, 68 at step
218. The controller 50 also starts the evaporator fan 64 at step
220, to thereby force air flow from the refrigerated portion 74
through the evaporator portion 72 and the evaporator 30 for further
cooling. This final step of the defrost cycle or method 200 returns
the refrigerator 10 to the operational state shown in FIG. 6, which
is the normal cooling operational state. As a result of the
insulated cover 70, the defrost cycle does not cause a significant
temperature spike within the refrigerated interior 18 of the
cabinet 12, and the refrigerator 10 therefore is advantageous over
conventional refrigerator designs.
[0042] As briefly noted above, in one alternative embodiment the
defrost cycle will be an adaptive defrost cycle selectively
actuated at step 202 of the method 200. In this adaptive defrost
cycle, the period between defrost cycles and the time duration of
the defrost cycles are modified based on a plurality of operational
parameters monitored by the controller 50. For example, the
conventional time-based defrost cycle may operate the defrost
heater 114 for 10 minutes every six hours. By contrast, the
adaptive defrost cycle may monitor the actual temperature being
maintained in the cabinet 12, as well as the number of door
openings and amount of total time the door is open. These and other
factors are considered to determine how long the period should be
before the next defrost cycle is started, and also how long the
defrost heater 114 should be operated in the next defrost cycle. In
this regard, if the door of the cabinet 12 is not opened often
during a six hour period and the evaporator 30 is having little
trouble maintaining the desired temperature within the refrigerated
portion 74, then the next defrost cycle may be delayed by an
additional number of hours and/or shortened in duration. Thus, the
adaptive defrost cycle is highly energy efficient because the
evaporator coil 112 is only defrosted when that cycle becomes
necessary. Moreover, the adaptive defrost cycle automatically
adjusts the refrigerator 10 for proper and efficient operation in a
variety of environmental conditions.
[0043] While the present invention has been illustrated by a
description of an exemplary embodiment and while this embodiment
has been described in considerable detail, it is not the intention
of the applicant to restrict or in any way limit the scope of the
appended claims to such detail. Additional advantages and
modifications will readily appear to those skilled in the art. The
invention in its broader aspects is therefore not limited to the
specific details, representative apparatus and method, and
illustrative example shown and described. Accordingly, departures
may be made from such details without departing from the spirit or
scope of applicant's general inventive concept.
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