U.S. patent application number 13/652992 was filed with the patent office on 2013-04-25 for high performance refrigerator having evaporator outside cabinet.
This patent application is currently assigned to THERMO FISHER SCIENTIFIC (ASHEVILLE) LLC. The applicant listed for this patent is Thermo Fisher Scientific (Asheville) LLC. Invention is credited to Christopher Bruchs, Robert Bruker, J. Antonio Contreras, Lafaire, Ralph Hegedus, Todd Swift.
Application Number | 20130098075 13/652992 |
Document ID | / |
Family ID | 47324691 |
Filed Date | 2013-04-25 |
United States Patent
Application |
20130098075 |
Kind Code |
A1 |
Hegedus; Ralph ; et
al. |
April 25, 2013 |
HIGH PERFORMANCE REFRIGERATOR HAVING EVAPORATOR OUTSIDE CABINET
Abstract
A high performance refrigerator includes a cabinet with a
refrigerated interior, a refrigeration fluid circuit having an
evaporator located within an insulated evaporator compartment
outside the cabinet, and at least one damper that opens to permit
air circulation from the refrigerated interior through the
evaporator compartment. The refrigerator also includes a eutectic
member configured to melt at an operating temperature of the
refrigerator. The evaporator cools the refrigerated interior to a
temperature below the operating temperature so that the eutectic
member melts to cool the refrigerated interior or the evaporator
compartment during a defrost cycle. The insulated evaporator cover
limits heat transfer into the refrigerated interior during the
defrost cycle to avoid temperature spikes in the refrigerated
interior.
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) LLC; |
Asheville |
NC |
US |
|
|
Assignee: |
THERMO FISHER SCIENTIFIC
(ASHEVILLE) LLC
Asheville
NC
|
Family ID: |
47324691 |
Appl. No.: |
13/652992 |
Filed: |
October 16, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61548807 |
Oct 19, 2011 |
|
|
|
Current U.S.
Class: |
62/80 ; 62/151;
62/156; 62/426 |
Current CPC
Class: |
F25D 16/00 20130101;
F25D 17/067 20130101; F25D 2317/066 20130101; F25D 21/08 20130101;
F25D 17/045 20130101; F25D 2317/067 20130101; F25D 2317/0654
20130101 |
Class at
Publication: |
62/80 ; 62/426;
62/151; 62/156 |
International
Class: |
F25D 21/06 20060101
F25D021/06; F25B 1/00 20060101 F25B001/00; F25D 21/08 20060101
F25D021/08; F25D 17/06 20060101 F25D017/06; F25D 21/02 20060101
F25D021/02 |
Claims
1. A refrigerator, comprising: a cabinet having a refrigerated
interior; a refrigeration fluid circuit for circulating a
refrigerant, the circuit including a compressor, a condenser, an
expansion device, and an evaporator located within an insulated
evaporator compartment outside the cabinet, and including an
evaporator coil and an evaporator fan producing air flow through
the evaporator coil; at least one damper that may open to permit
air circulation from the refrigerated interior through the
evaporator compartment; and a eutectic member configured to melt at
an operating temperature of the refrigerator, wherein the
evaporator cools the refrigerated interior to a temperature below
the operating temperature such that when the at least one damper is
closed for a defrost cycle, the eutectic member cools at least one
of the refrigerated interior and the evaporator compartment by
melting.
2. The refrigerator of claim 1, wherein the cabinet includes side
walls and a top wall, the at least one damper is formed in the top
wall, and the eutectic member is mounted along one of the side
walls.
3. The refrigerator of claim 1, wherein the eutectic member is a
plate-shaped member.
4. The refrigerator of claim 1, wherein the operating temperature
is about -32.degree. C.
5. The refrigerator of claim 1, wherein the cabinet includes a top
wall, the at least one damper is formed in the top wall, and the
eutectic member is mounted along the top wall.
6. The refrigerator of claim 1, wherein the eutectic member is
mounted within the evaporator compartment such that the eutectic
member cools the evaporator compartment by melting during a defrost
cycle.
7. The refrigerator of claim 1, wherein the cabinet further
includes: a top wall adjacent the insulated evaporator compartment,
a door, a rear wall including an inlet duct in communication with
the evaporator and a plurality of inlet ports leading into the
refrigerated interior, and side walls extending between the rear
wall and the door, each side wall including an outlet duct in
communication with the evaporator and a plurality of outlet ports
leading from the refrigerated interior, wherein the at least one
damper is a valve controlling flow between the evaporator and the
refrigerated interior via the inlet duct and the outlet ducts.
8. A refrigerator, comprising: a cabinet having a refrigerated
interior; a refrigeration fluid circuit for circulating a
refrigerant, the circuit including a compressor, a condenser, an
expansion device, and an evaporator located within an insulated
evaporator compartment outside the cabinet and including an
evaporator coil, an evaporator fan producing air flow through the
evaporator coil, and a defrost heater; at least one damper that may
open to permit air circulation from the refrigerated interior
through the evaporator compartment; 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 compartment 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.
9. The refrigerator of claim 8, 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 coil; starting the
compressor after the remaining moisture drips off the evaporator
coil; 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.
10. The refrigerator of claim 9, wherein the first target
temperature is about 10.degree. C. and the second target
temperature is about -25.degree. C.
11. The refrigerator of claim 8, 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 compartment
from the refrigerated interior, the second damper in an open
position permitting air flow from the evaporator compartment into
the refrigerated interior.
12. The refrigerator of claim 8, wherein the insulated evaporator
compartment further includes a plurality of vacuum insulated
panels.
13. The refrigerator of claim 8, further comprising: a eutectic
member located within the cabinet and configured to melt at an
operating temperature of the refrigerator, wherein the evaporator
cools the refrigerated interior to a temperature below the
operating temperature such that when the at least one damper is
closed for a defrost cycle, the eutectic member cools the
refrigerated interior by melting.
14. The refrigerator of claim 13, wherein the cabinet includes side
walls and a top wall, the at least one damper is formed in the top
wall, and the eutectic member is mounted along one of the side
walls.
15. The refrigerator of claim 13, wherein the cabinet includes a
top wall, the at least one damper is formed in the top wall, and
the eutectic member is mounted along the top wall.
16. The refrigerator of claim 13, wherein the operating temperature
is about -30.degree. C.
17. The refrigerator of claim 8, further comprising: a eutectic
member located within the evaporator compartment and configured to
melt at an operating temperature of the refrigerator, wherein the
evaporator cools the refrigerated interior to a temperature below
the operating temperature such that when the at least one damper is
closed for a defrost cycle, the eutectic member cools the
evaporator compartment by melting.
18. The refrigerator of claim 8, wherein the cabinet further
includes: a top wall adjacent the insulated evaporator compartment,
a door, a rear wall including an inlet duct in communication with
the evaporator and a plurality of inlet ports leading into the
refrigerated interior, and side walls extending between the rear
wall and the door, each side wall including an outlet duct in
communication with the evaporator and a plurality of outlet ports
leading from the refrigerated interior, wherein the at least one
damper is a valve controlling flow between the evaporator and the
refrigerated interior via the inlet duct and the outlet ducts.
19. 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 an
insulated evaporator compartment outside the cabinet and having an
evaporator fan and defrost heater, the refrigerator further
including at least one damper configured to separate the evaporator
compartment 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 compartment 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.
20. The method of claim 19, 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 coil; starting
operation of the compressor after the remaining moisture drips off
the evaporator coil; 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.
21. The method of claim 20, wherein the first target temperature is
about 10.degree. C. and the second target temperature is about
-25.degree. C.
22. The method of claim 19, wherein the system further includes a
eutectic member located within the cabinet or the evaporator
compartment and configured to melt at an operating temperature of
the refrigerator, and the method further comprises: cooling the
refrigerated interior with the evaporator to a temperature below
the operating temperature before a defrost cycle; and melting the
eutectic member to cool at least one of the refrigerated interior
and the evaporator compartment during the defrost cycle.
23. A refrigerator, comprising: a cabinet having a refrigerated
interior; a refrigeration fluid circuit for circulating a
refrigerant, the circuit including a compressor, a condenser, an
expansion device, and an evaporator located within an evaporator
compartment outside the cabinet and including an evaporator coil
and an evaporator fan producing air flow through the evaporator
coil; and at least one valve that may open to permit air
circulation from the refrigerated interior through the evaporator
compartment, wherein the cabinet further includes: a top wall
adjacent the evaporator compartment, a door, a rear wall including
an inlet duct in communication with the evaporator and a plurality
of inlet ports leading into the refrigerated interior, and side
walls extending between the rear wall and the door, each side wall
including an outlet duct in communication with the evaporator and a
plurality of outlet ports leading from the refrigerated interior,
wherein the at least one valve controls flow between the evaporator
and the refrigerated interior via the inlet duct and the outlet
ducts.
24. The refrigerator of claim 23, wherein the cabinet includes a
bottom wall, and the inlet duct and outlet ducts each extend
between the top wall and the bottom wall.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] The present application claims the priority benefit of U.S.
Provisional Patent Application No. 61/548,807 (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 an insulated evaporator compartment outside the
cabinet. The evaporator includes an evaporator coil and an
evaporator fan producing air flow through the evaporator coil. The
refrigerator includes at least one damper which opens to permit air
circulation from the refrigerated interior through the evaporator
compartment. The refrigerator also includes a eutectic member that
melts at an operating temperature of the refrigerator. The
evaporator cools the refrigerated interior to a temperature below
the operating temperature such that when the at least one damper is
closed for a defrost cycle, the eutectic member melts to cool at
least one of the refrigerated interior and the evaporator
compartment.
[0009] In one aspect, the eutectic member is mounted along one of
the side walls of the cabinet or along the top wall of the cabinet.
The at least one damper is also formed in the top wall such that
the eutectic member acts as a temperature ballast as well as a cold
generation device. In another aspect, the eutectic member is
mounted within the evaporator compartment such that the eutectic
member melts to cool the evaporator compartment during operation of
a defrost heater within the evaporator compartment.
[0010] In another 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 an insulated evaporator compartment outside the
cabinet. The evaporator includes an evaporator coil, an evaporator
fan producing air flow through the evaporator coil, and a defrost
heater. The refrigerator includes at least one damper which opens
to permit air circulation from the refrigerated interior through
the evaporator compartment. The refrigerator also 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 compartment 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.
[0011] 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 and any remaining moisture is allowed to drip off the
evaporator coil. After any remaining moisture drips off the
evaporator coil, 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.
[0012] In yet another embodiment of the invention, 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 an insulated evaporator
compartment outside the cabinet. The evaporator includes an
evaporator coil and an evaporator fan producing air flow through
the evaporator coil. The refrigerator includes at least one valve
which opens to permit air circulation from the refrigerated
interior through the evaporator compartment. The cabinet includes a
top wall adjacent the evaporator compartment, a door, a rear wall,
and side walls (including a rear wall) extending between the rear
wall and the door. The rear wall includes an inlet duct in
communication with the evaporator and a plurality of inlet ports
leading into the refrigerated interior. The side walls include an
outlet duct in communication with the evaporator and a plurality of
outlet ports leading from the refrigerated interior. The at least
one valve controls flow between the evaporator and the refrigerated
interior via the inlet duct and the outlet ducts.
[0013] In another embodiment of the invention, a method of
operating a refrigerator is provided, the refrigerator including a
cabinet with a refrigerated interior and a refrigeration fluid
circuit including a compressor, a condenser, and an evaporator
located in an insulated evaporator cover outside the cabinet. The
evaporator includes an evaporator fan and a defrost heater. The
refrigerator also includes at least one damper separating the
evaporator compartment 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 compartment from the refrigerated interior. A defrost
heater starts operation to remove moisture from evaporator. The
refrigerated interior remains thermally isolated from the
evaporator during operation of the defrost heater.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The accompanying drawings, which are incorporated in and
constitute a part of this specification, illustrate embodiments of
the invention and, together with a general description of the
invention given above, and the detailed description of the
embodiments given below, serve to explain the principles of the
invention.
[0015] FIG. 1 is a perspective view of a refrigerator including an
evaporator located outside the cabinet according to an exemplary
embodiment.
[0016] FIG. 2 is a schematic representation of the refrigeration
fluid circuit used with the refrigerator of FIG. 1.
[0017] FIG. 3 is a perspective view of the insulating evaporator
cover (shown in phantom) and dampers used with the refrigerator of
FIG. 1.
[0018] 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.
[0019] FIG. 5 is a cross-sectional side view of the refrigerator of
FIG. 1 along line 5-5, with the dampers in a closed position and
eutectic plates located in the evaporator compartment and the
cabinet.
[0020] FIG. 6 is a cross-sectional side view of the refrigerator of
FIG. 5, with the dampers in an open position.
[0021] FIG. 7 is a cross-sectional side view of another embodiment
of a refrigerator including an evaporator located outside the
cabinet and air ducts through the walls of the cabinet.
[0022] FIG. 8 is a cross-sectional front view of the refrigerator
of FIG. 7.
[0023] FIG. 9 is a schematic diagram of the controller and damper
or valve drive elements used with the refrigerators of FIGS. 1 and
7.
[0024] FIG. 10 is a schematic flowchart illustrating an operational
sequence of a controller associated with the refrigerators of FIGS.
1 and 7.
DETAILED DESCRIPTION
[0025] 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 comprising 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. The
refrigerator 10 also includes an upper compartment 21 disposed
above the cabinet 12 and configured to contain the components of
the refrigeration fluid circuit 20 as described in further detail
below.
[0026] 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.
[0027] 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.
[0028] 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.
[0029] 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.
[0030] 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 FIGS. 9 and
10, 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.
[0031] 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.
[0032] With reference to FIGS. 3-6 and in particular FIG. 3, the
refrigerator 10 includes an insulated cover 70 located outside the
cabinet 18 and inside the upper compartment 21. The insulated cover
70 encloses an insulated evaporator compartment 72 which is
isolated from a refrigerated portion 74 within the interior 18 of
the cabinet 12. The refrigerated portion 74 is defined by a top
wall 76, side walls 78 (including a rear wall 78a and side walls
78b), and a bottom wall 80 collectively forming the cabinet housing
14. The insulated cover 70 is coupled to the top wall 76 of the
cabinet housing 14 such that the first and second dampers 66, 68
open flow into the refrigerated interior 18. More particularly, the
insulated cover 70 is coupled to the top wall 76 of the cabinet
housing 14 to thermally isolate the evaporator compartment 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 is a rectilinear box-shaped member
including a plurality of vertical panel portions 82 extending
between two horizontal panel portions 84, one of which is located
adjacent to the top wall 76 of the cabinet housing 14. The vertical
panel portions 82 and the horizontal panel portions 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.
[0033] As shown in FIG. 3, the evaporator 30 mounts into a divider
panel 88 located generally centrally within the evaporator
compartment 72 so as to divide the evaporator compartment 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
bottom-side 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.
[0034] 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. 9 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 compartment 72 and the evaporator
30.
[0035] 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 compartment 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 compartment 72.
[0036] 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).
[0037] With reference to FIGS. 5 and 6, the placement of the
evaporator 30 within the evaporator compartment 72 outside the
cabinet 12 is further shown. The upper compartment 21 contains the
evaporator compartment 72 and 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 21
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 side horizontal panel portion 82 of the insulated
cover 70 to deliver refrigerant 36 between the components in the
upper compartment 21 and the evaporator 30 in the evaporator
compartment 72.
[0038] 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
compartment 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 compartment 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 compartment 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 120.
Thus, relatively warm air enters the evaporator compartment 72
through the inlet aperture 94 and relatively cold air exits the
evaporator compartment 72 through the outlet aperture 96 in this
operating state of the refrigerator 10.
[0039] The refrigerator 10 also includes one or more eutectic
members 122 as shown in FIGS. 5 and 6. The eutectic members 122 are
eutectic plates 122 mounted in close proximity to the insulated
cover 70. The eutectic plate 122 is configured to melt at a
predetermined operating temperature based on the material forming
the eutectic plate 122. In this regard, the eutectic plate 122 may
be configured to melt around the intended operating temperature of
the refrigerator, such as -30.degree. C. Thus, the evaporator 30
operates to cool the interior 18 of the cabinet 12 below the
operating temperature such that the eutectic plate 122 is
maintained in a solid state during normal operation of the
refrigerator 10. When a defrost cycle is initiated, the dampers 66,
68 close and the defrost heater 114 begins warming the evaporator
compartment 72. The insulated cover 70 helps prevent the heat
energy generated by the defrost heater 114 from entering the
refrigerated interior 18, thereby reducing any temperature spike
encountered by the interior 18 during the defrost cycle.
[0040] The eutectic plate 122 may be mounted along the side walls
78 or the top wall 76 within the cabinet 12. In these embodiments,
any heat energy that enters the interior 18 or is generated within
the interior 18 is counteracted by the melting of the eutectic
plate 122, which acts as a supplemental cooling device during the
defrost cycle. To this end, the eutectic plate also limits the
temperature spike within the cabinet 12. When the eutectic plate
122 is located along the top wall 76 of the cabinet housing 14, the
eutectic plate 122 may operate as a temperature ballast or
additional insulation between the refrigerated interior 18 and the
evaporator compartment 72.
[0041] In another embodiment, the eutectic plate 122 may
alternatively be mounted within the evaporator compartment 72.
Similar to the previous embodiment, the eutectic plate 122 melts to
counteract the detrimental heating effects of the defrost heater
114. In this regard, the defrost heater 114 heats the evaporator
coil 112 to melt frost from the evaporator coil 112 but the heat
energy fills the remainder of the evaporator compartment 72 where
the heat energy is unnecessary. Once the defrost cycle is
completed, the melting of the eutectic plate 122 assists the
refrigerant 36 flowing through the evaporator coil 112 to more
rapidly cool the evaporator compartment 72 back to the intended
operating temperature of the refrigerator 10. Consequently, the
eutectic plate 122 may reduce any temperature spike encountered
within the cabinet 12 during a defrost cycle or may reduce the
overall length of a defrost cycle by more rapidly cooling the
evaporator compartment 72 at the end of such a defrost cycle.
[0042] An alternative embodiment of the refrigerator 130 is shown
in FIGS. 7 and 8. The refrigerator 130 of this embodiment includes
many of the same components of the previously-described
refrigerator 10, and these elements are indicated by the same
reference numbers in FIGS. 7 and 8. The primary difference of this
embodiment of the refrigerator 130 is that the dampers 66, 68 have
been replaced by an air duct and valve assembly. To this end, the
evaporator compartment 72 includes an outlet valve 132 for air flow
as shown in FIG. 7. The outlet valve 132 communicates with an inlet
or supply duct 134 extending along the length of the rear wall 78a
of the cabinet housing 14. The inlet or supply duct 134 includes a
plurality of inlet ports 136 for delivering chilled air flow
(indicated by arrows 138) into all levels of the refrigerated
interior 18 of the cabinet 12. In contrast to the first embodiment,
the chilled air flow enters the cabinet 12 along the entire height
of the cabinet 12.
[0043] In a similar manner, each of the side walls 78b extending
between the rear wall 78a and the door 16 includes an outlet or
return duct 140 with a plurality of outlet ports 142 disposed along
the length of the side walls 78b. To this end, a return flow of
warmed air (indicated by arrows 144) flows from the interior 18
through the outlet ports 142 and the outlet or return ducts 140 to
inlet valves 146 at the insulated cover 70. Thus, the inlet valves
146 and the outlet valve 132 control air flow through the
evaporator 30 via the inlet duct 134 and the outlet ducts 140.
Because the inlet duct 134 and the outlet ducts 140 extend from the
top wall 76 to the bottom wall 80 of the cabinet housing 14, the
air duct and valve assembly of this embodiment of the refrigerator
130 enable more thorough air flow through the cabinet 12.
[0044] FIG. 9 schematically illustrates the control and actuation
mechanisms for the first and second dampers 66, 68 (or the valves
132, 146). More specifically, the first and second dampers 66, 68
are connected to the damper/valve 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/valve drive mechanism 100, for example. Thus, the
controller 50 functions to actuate operation of the damper/valve
drive mechanism 100.
[0045] As previously described with reference to the refrigerator
10 of FIG. 1, 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. Similarly, a valve drive
mechanism 100 for the refrigerator 130 of FIG. 7 may also include
various types of actuators as readily understood.
[0046] An exemplary operation of the refrigerator 10 (or 130) is
shown schematically in the flowchart of FIG. 10. 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.
[0047] Returning to FIG. 10, 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 (or the outlet valve 132 and the inlet valves 146)
at step 206 to thermally isolate the evaporator compartment 72 from
the refrigerated portion 74 of the cabinet 12. With the evaporator
compartment 72 thermally isolated from 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. During the operation of the defrost heater 114, the cabinet
12 continues to be cooled by the melting of the eutectic plate 122
at step 210.
[0048] 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 212, 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 214.
After this "drip time" has occurred, the controller 50 starts the
compressor 22 to cause refrigerant flow through the evaporator 30
again at step 216, thereby cooling the evaporator compartment
72.
[0049] At step 218, 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 (or the
outlet valve 132 and inlet valves 146) at step 220. 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
compartment 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 and/or the melting of the eutectic plate 122, 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.
[0050] 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.
[0051] While the present invention has been illustrated by a
description of exemplary embodiments and while these embodiments
have 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. For
example, the air ducts 134, 140 may be combined with the eutectic
plates 122 shown in the various embodiments 10, 130 of the
refrigerator. 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.
* * * * *