U.S. patent application number 12/956414 was filed with the patent office on 2012-03-15 for apparatus and method for monitoring super-heating of refrigerant to improve compressor efficiency and lower energy usage.
This patent application is currently assigned to GENERAL ELECTRIC COMPANY. Invention is credited to Bryan James Beckley, Jason Andrew May, Brian Michael Schork.
Application Number | 20120060525 12/956414 |
Document ID | / |
Family ID | 45805322 |
Filed Date | 2012-03-15 |
United States Patent
Application |
20120060525 |
Kind Code |
A1 |
Schork; Brian Michael ; et
al. |
March 15, 2012 |
APPARATUS AND METHOD FOR MONITORING SUPER-HEATING OF REFRIGERANT TO
IMPROVE COMPRESSOR EFFICIENCY AND LOWER ENERGY USAGE
Abstract
Apparatus and methodologies are provided to monitor temperature
from at least two locations on an evaporator in a refrigeration
system. Operational characteristics of one or more of the
compressor, condenser and evaporator cooling fans are adjusted
based on the difference in temperature between the two locations on
the evaporator. In some systems a second evaporator may be provided
along with a refrigerant control valve. Cooling air flow across the
second evaporator and refrigerant distribution between the plural
evaporators may also be control.
Inventors: |
Schork; Brian Michael;
(Louisville, KY) ; Beckley; Bryan James;
(Louisville, KY) ; May; Jason Andrew; (Prospect,
KY) |
Assignee: |
GENERAL ELECTRIC COMPANY
Schenectady
NY
|
Family ID: |
45805322 |
Appl. No.: |
12/956414 |
Filed: |
November 30, 2010 |
Current U.S.
Class: |
62/115 ; 62/180;
62/507 |
Current CPC
Class: |
F25B 2600/112 20130101;
F25B 49/02 20130101; F25D 29/00 20130101; F25D 2700/10 20130101;
Y02B 30/743 20130101; F25B 2600/111 20130101; F25B 2600/21
20130101; Y02B 30/741 20130101; F25B 2600/0253 20130101; Y02B 30/70
20130101 |
Class at
Publication: |
62/115 ; 62/507;
62/180 |
International
Class: |
F25B 1/00 20060101
F25B001/00; F25D 17/06 20060101 F25D017/06; F25D 17/02 20060101
F25D017/02; F25B 39/04 20060101 F25B039/04 |
Claims
1. A refrigerator, comprising: a controller; a compressor; a
condenser; a condenser fan configured to provide air flow across
said condenser; an evaporator; an evaporator fan configured to
provide air flow across said evaporator; and at least two
temperature sensors located on the evaporator, wherein said
controller is configured to control operating characteristics of at
least one of said compressor, said condenser fan, and said
evaporator fan based on the difference in temperature between said
first temperature sensor and said second temperature sensor.
2. A refrigerator as in claim 1, wherein said controller is
configured to modulate the speed of the compressor based on the
difference in temperature between said first temperature sensor and
said second temperature sensor.
3. A refrigerator as in claim 1, wherein said controller is
configured to adjust the speed of the evaporator fan based on the
difference in temperature between said first temperature sensor and
said second temperature sensor.
4. A refrigerator as in claim 1, wherein said controller is
configured to adjust the speed of the condenser fan based on the
difference in temperature between said first temperature sensor and
said second temperature sensor.
5. A refrigerator as in claim 1, wherein said temperature sensors
are thermistors.
6. A refrigerator as in claim 5, wherein said thermistors are
coupled together to form one or more voltage divider circuits
configured to provide reduced number of voltage inputs to said
controller representative of the difference in temperature between
the thermistors.
7. A refrigerator as in claim 1, wherein said controller is
configured to control operating characteristics in accordance with
a proportional-integral-differential (PID) control system based on
the difference in temperature between said first temperature sensor
and said second temperature sensor.
8. A refrigerator as in claim 1, further comprising: a second
evaporator; a second evaporator fan configured to provide air flow
across said second evaporator; and a refrigerant control valve
configured to control distribution of refrigerant between said
evaporator and said second evaporator, wherein said controller is
configured to control at least one of said compressor, said
condenser fan, and said evaporator fan, said second evaporator fan,
and said refrigerant control valve based on the difference in
temperature between said first temperature sensor and said second
temperature sensor.
9. A method for improving compressor efficiency and lowering energy
consumption in a refrigeration system, comprising: providing a
refrigeration system including a compressor, a condenser, and an
evaporator; monitoring temperature from at least two locations on
the evaporator; and modulating one or more of the operational speed
of the compressor and air flow across one or more of the condenser
and evaporator based on the difference in temperature between the
at least two locations on the evaporator.
10. A method as in claim 9, wherein modulating comprises modulating
the speed of the compressor based on the difference in temperature
between the at least two locations on the evaporator.
11. A method as in claim 9, wherein modulating comprises modulating
the speed of air flow across the evaporator based on the difference
in temperature between the at least two locations on the
evaporator.
12. A method as in claim 9, wherein modulating comprises modulating
the speed of air flow across the condenser based on the difference
in temperature between the at least two locations on the
evaporator.
13. A method as in claim 9, wherein monitoring temperature
comprises providing thermistors at two or more location on the
evaporator.
14. A method as in claim 13, wherein the difference in temperature
is obtained by coupling the thermistors together to form one or
more voltage dividers.
15. A method as in claim 9, further comprising: providing a second
evaporator; providing a refrigerant control valve configured to
control distribution of refrigerant between the evaporator and the
second evaporator; and modulating one or more of the operational
speed of the compressor, air flow across one or more of the
condenser, the evaporator, and the second evaporator, and
refrigerant distribution between the evaporator and the second
evaporator based on the difference in temperature between the at
least two locations on the evaporator.
Description
FIELD OF THE INVENTION
[0001] The present subject matter relates to refrigerators. More
particularly, the present subject matter relates to improved
temperature monitoring arrangements that provide increased
operational efficiency opportunities.
BACKGROUND OF THE INVENTION
[0002] Certain currently available refrigeration systems employ
banded temperature control schemes which operated as either ON/OFF
or LOW, MED, HIGH and required operational deadbands within their
temperature control systems. Such systems include certain inherent
inefficiencies due to start losses and reliability penalties
associated with starting and stopping a sealed system. In other
systems, temperature sensing only looks at exit temperature which
does not give an indication of superheat which is correlated to
evaporator/system efficiency.
[0003] U.S. Pat. No. 6,718,778 B2 to Lawrence entitled "Defrost
Control Method and Apparatus" discloses a defrost control system
that detects the variation in flow rate of refrigerant through an
evaporator while the flow is regulated to achieve a desired level
of superheat at the outlet of the evaporator. When the flow rate
becomes unstable, defrosting of the evaporator is triggered. In one
embodiment, the apparatus uses two temperature sensors to determine
the difference in temperature at a spot on the evaporator and at
the outlet of the evaporator to control a defrost cycle.
[0004] In view of these concerns, it would be advantageous to
provide a refrigeration system that could accurately monitor the
degree of evaporator superheat, so that various system component
operational aspects can be compensated to maintain an improved
balance of refrigerant and air flow to maximize the use of the
physical heat exchanger surface area.
BRIEF DESCRIPTION OF THE INVENTION
[0005] Aspects and advantages of the invention will be set forth in
part in the following description, or may be obvious from the
description, or may be learned through practice of the
invention.
[0006] The present subject matter relates to refrigeration
apparatus and methodologies for monitoring super-heating of a
refrigerant to improve compressor efficiency and lower energy usage
in a refrigerator. In a first embodiment, a refrigerator having a
controller, a compressor, a condenser, and an evaporator is
provided. The refrigerator also includes a condenser fan configured
to provide air flow across the condenser and an evaporator fan
configured to provide air flow across the evaporator.
[0007] At least two temperature sensors are mounted on the
evaporator. The controller is configured to control operating
characteristics of at least one of the compressor, the condenser
fan, and the evaporator fan based on the difference in temperature
between the temperature sensors.
[0008] In certain embodiments, the controller is configured to
modulate the speed of the compressor while in other embodiments the
controller controls the speed of the evaporator fan and/or
condenser fan.
[0009] In some embodiments the temperature sensors are thermistors,
which, in selected embodiments may be coupled together to form one
or more voltage dividers configured to provide a reduced number of
voltage inputs to the controller representative of the difference
in temperature between the thermistors.
[0010] In selected embodiments, the controller is configured to
control operating characteristics in accordance with a
proportional-integral-differential (PID) control system based on
the difference in temperature between the at least two temperature
sensors.
[0011] In certain other embodiments, the refrigerator may include a
second evaporator, a second evaporator fan configured to provide
air flow across the second evaporator, and a refrigerant control
valve configured to control distribution of refrigerant between the
evaporator and the second evaporator. In such embodiments, the
controller is configured to control at least one of the compressor,
the condenser fan, the evaporator fan, the second evaporator fan,
and the refrigerant control valve based on the difference in
temperature between the at least two temperature sensors.
[0012] The present subject matter also relates to a method for
improving compressor efficiency and lowering energy consumption in
a refrigeration system, comprising providing a refrigeration system
including a compressor, a condenser, and an evaporator. The method
monitors temperature from at least two locations on the evaporator
and modulates one or more of the operational speed of the
compressor and air flow across one or more of the condenser and
evaporator based on the difference in temperature between the at
least two locations on the evaporator.
[0013] In certain of the methods, the speed of the compressor is
modulated while in other methods the speed of the air flow across
the evaporator and/or the condenser is modulated based on the
difference in temperature between the at least two locations on the
evaporator.
[0014] In selected methods temperature is monitored by providing
two or more thermistors on the evaporator. Under certain of these
methods, a difference in temperature is obtained by coupling the
thermistors together to form one or more voltage dividers.
[0015] These and other features, aspects and advantages of the
present invention will become better understood with reference to
the following description and appended claims. The accompanying
drawings, which are incorporated in and constitute a part of this
specification, illustrate embodiments of the invention and,
together with the description, serve to explain the principles of
the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] A full and enabling disclosure of the present invention,
including the best mode thereof, directed to one of ordinary skill
in the art, is set forth in the specification, which makes
reference to the appended figures, in which:
[0017] FIG. 1 provides an illustration of an exemplary embodiment
of a refrigerator as may be used with the present subject
matter;
[0018] FIG. 2 is a schematic illustration providing an example of a
refrigeration cycle as may be used with the present subject
matter;
[0019] FIG. 3 is a schematic illustration providing an example of a
proportional-integral-derivative (PID) controlled refrigerator in
accordance with the present technology; and
[0020] FIG. 4 is a schematic representation of a thermistors
voltage divider in accordance with one embodiment of the present
subject matter.
[0021] Repeat use of reference characters throughout the present
specification and appended drawings is intended to represent same
or analogous features or elements of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0022] Reference now will be made in detail to embodiments of the
invention, one or more examples of which are illustrated in the
drawings. Each example is provided by way of explanation of the
invention, not limitation of the invention. In fact, it will be
apparent to those skilled in the art that various modifications and
variations can be made in the present invention without departing
from the scope or spirit of the invention. For instance, features
illustrated or described as part of one embodiment can be used with
another embodiment to yield a still further embodiment. Thus, it is
intended that the present invention covers such modifications and
variations as come within the scope of the appended claims and
their equivalents.
[0023] As noted in the Summary section, the present subject matter
is directed toward refrigeration apparatus and methodologies for
monitoring super-heating of a refrigerant to improve compressor
efficiency and lower energy usage in a refrigerator. In accordance
with certain aspects of the present subject matter two or more
temperature sensing devices are provided at various positions on
one or more evaporators to monitor temperature. In so doing,
effective use of heat exchanger surface area for heat transfer may
be maximized, thereby minimizing thermodynamic losses associated
with superheat, thereby maximizing the efficiency of the evaporator
resulting in the overall refrigeration cycle becoming more
efficient. The net effect of this type of operation leads to an
overall reduction in steady state energy consumption.
[0024] Referring now to the drawings, FIG. 1 provides a front view
of a representative refrigerator 10 incorporating an exemplary
embodiment of the present invention. For illustrative purposes, the
present invention is described with a refrigerator 10 having a
construction as shown and described further below. As used herein,
a refrigerator includes appliances such as a freezer,
refrigerator/freezer combination, compact, and any other style or
model of a refrigerator. Accordingly, other configurations
including multiple and different styled compartments could be used
with refrigerator 10, it being understood that the configuration
shown in FIG. 1 is by way of example only.
[0025] Refrigerator 10 includes a fresh food storage compartment 12
and a freezer storage compartment 14. Freezer compartment 14 and
fresh food compartment 12 are arranged side-by-side within an outer
case 16. Breaker strip 22 and mullion 24 form a front face, and
extend completely around inner peripheral edges of case 16. In
addition, refrigerator 10 includes shelves 28 and slide-out storage
drawers 30 which normally are provided in fresh food compartment 12
to support items being stored therein.
[0026] Refrigerator 10 is controlled by a processing device or
other controller, such as a microprocessor (not shown in FIG. 1),
according to user preference via manipulation of a control
interface 32 mounted in an upper region of fresh food storage
compartment 12 and coupled to the microprocessor. A shelf 34 and
wire baskets 36 are provided in freezer compartment 14. In
addition, an ice maker 38 may be provided in freezer compartment
14.
[0027] A freezer door 42 and a fresh food door 44 close access
openings to fresh food and freezer compartments 12, 14,
respectively. Each door 42, 44 is mounted to rotate about its outer
vertical edge between an open position, as shown in FIG. 1, and a
closed position (not shown) closing the associated storage
compartment. Freezer door 42 includes a plurality of storage
shelves 46, and fresh food door 44 includes a plurality of storage
shelves 48.
[0028] FIG. 2 is a schematic view of refrigerator 10 (FIG. 1)
including an exemplary sealed cooling system 60. In accordance with
known refrigerators, refrigerator 10 includes a machinery
compartment 62 that at least partially contains components for
executing a known vapor compression cycle for cooling air. The
components include a compressor 64, a heat exchanger or condenser
66, an expansion device 68, and an evaporator 70 connected in
series and charged with a refrigerant. Evaporator 70 is also a type
of heat exchanger which transfers heat from air passing over the
evaporator to a refrigerant flowing through evaporator 70 thereby
causing the refrigerant to vaporize. As such, cooled air is
produced and configured to refrigerate compartments 12, 14 of
refrigerator 10.
[0029] From evaporator 70, vaporized refrigerant flows to
compressor 64, which operates to increase the pressure of the
refrigerant. This compression of the refrigerant raises its
temperature, which is lowered by passing the gaseous refrigerant
through condenser 66 where heat exchange with ambient air takes
place so as to cool the refrigerant. A fan 72 is used to pull air
across condenser 66, as illustrated by arrows A, so as to provide
forced convection for a more rapid and efficient heat exchange
between the refrigerant and the ambient air.
[0030] Expansion device 68 further reduces the pressure of
refrigerant leaving condenser 66 before being fed as a liquid to
evaporator 70. Collectively, the vapor compression cycle components
in a refrigeration circuit, associated fans, and associated
compartments are sometimes referred to as a sealed refrigeration
system operable to force cold air through refrigeration
compartments 12, 14. The refrigeration system depicted in FIG. 2 is
provided by way of example only. It is within the scope of the
present invention for other configurations of the refrigeration
system to be used as well. For example, fan 74 may be repositioned
so as to push air across evaporator 70, dual evaporators may be
used with one or more fans, and numerous other configurations may
be applied as well.
[0031] With reference to FIG. 3, there is illustrated a schematic
representation of an example of a proportional-integral-derivative
(PID) controlled refrigerator 300 in accordance with the present
technology. Refrigerator 300, constructed in accordance with
present technology, may be provided with various components
including, but not limited to, controller 302, compressor 364,
evaporator 370, evaporator fan 374, condenser 366, expansion valve
368, condenser fan 372, fresh food fan 376, and damper 378.
[0032] In some embodiments of the present subject matter, as
illustrated herein generally in phantom, a second evaporator 380
may be provided along with a second evaporator fan 384. In such
embodiments, a refrigerant distribution control valve 382 may be
provided to control distribution of refrigerant between the
evaporators. Those of ordinary skill in the art will appreciate
that suitable coupling of the second evaporator 382, evaporator fan
394 and control valve 382 to the remaining portions of the
refrigeration system including the compressor 364 and control 302
are required. As such coupling would be well within the
capabilities of those of ordinary skill in the art, no further
described is deemed necessary.
[0033] Operational control devices including temperature sensor 392
within freezer compartment 314 and temperature sensor 394 within
fresh food compartment 312 may also be provided and configured to
transmit temperature signals to a controller 302. As previously
noted with reference to FIG. 1, controllers such as controller 302
may correspond to a number of different processing devices
including microprocessors or other types of microcontrollers as is
well understood by those of ordinary skill in the art.
[0034] In accordance with a significant aspect of one embodiment of
the present subject matter, by monitoring the temperature of the
evaporator, the operation of the compressor and/or other
operationally variable refrigeration components may be modulated or
adjusted so that, in the instance that the compressor speed is
modulated, the compressor Energy Efficiency Ratio (EER) may be
maximized permitting a more efficient run cycle and/or the overall
system Coefficient of Performance (COP) may be improved by
modulating the compressor and/or adjusting other operational
components by, for example, controlling the speed of one or more of
the fans.
[0035] In particular, by employing PID control to modulate the
speed of compressor 364 for example over signal line 340 from
controller 302, the compressor speed can be reduced, resulting in
less mass flow of refrigerant to the evaporator so that the
evaporator and condenser may be held at efficient core temperatures
and pressures. In so doing the extremely low evaporator
temperatures that are a natural side effect of cycling systems are
able to be substantially eliminated thereby shrinking the size of
the refrigeration cycle and minimizing cycling losses to provide a
higher compressor EER and system.
[0036] As is understood by those of ordinary skill in the art, a
proportional-integral-derivative (PID) control system may be
generally defined using the well recognized generic formula:
u ( t ) = K c ( e + 1 T i .intg. 0 t e t + T d e t )
##EQU00001##
where the three summed terms represent proportional, integral, and
derivative terms that, together with a multiplication constant,
represent the control function u(t). Such PID control systems may
be implemented in numerous manners including through hardware,
software, or combinations thereof.
[0037] In accordance with present technology, a control system,
including controller 302, is configured to monitor a temperature
difference between at least two points on evaporator 370 to provide
one or more temperature signals to controller 302. This temperature
difference between the points is then analyzed in controller 302
and used to vary the speed of compressor 364, vary the speed of one
or more fans such as evaporator fan 374 and/or condenser fan 372
via signals over control lines 334, 338, control refrigerant flow
distribution in a multiple evaporator system, or any combination
thereof, to maintain a fully flooded evaporator section against
varying heat loads. This differential signal may also be utilized
to determine when to terminate a defrost cycle.
[0038] In a first embodiment of the present subject matter, two
thermistors 396, 398 are mounted in two variable positions on
evaporator 370 as illustrated in FIG. 3. The two thermistors 396,
398 may be electrically arranged in a voltage divider circuit 400
as illustrated by thermistors 496, 498 in FIG. 4. With a supply
voltage applied across terminals 502 and ground terminal 504, a
temperature difference voltage is provided as an analog signal on
line 510 to controller 302 for feedback to a control program
stored, for example, in a memory associated with controller 302. In
this embodiment, the use of voltage divider 400 permits a solution
that requires reduces the required number of signal inputs to only
a single input to controller 302.
[0039] In accordance with a second embodiment of the present
subject matter, multiple temperature sensing devices similar to
temperature sensors 396, 398, 496, 498 may be placed at various
locations on evaporator 370 to provide multiple independent
temperature feedback signals to controller 302. In such an
instance, controller 302 is configured to calculate one or more
differences and use the result as feedback in the control program.
As with the previous embodiment, the voltage dividers may be used
to reduce the number of inputs to the controller, or may be used to
increase knowledge of the location of the gas transition point.
[0040] In all embodiments of the present subject matter, the
control program of controller 302 may include provision of feedback
control for PID control of the compressor, system fans, and/or
damper(s) positioning, but such is not a limitation of controller
302 as the controller may also provide additional control functions
relating to the overall operation of the refrigeration
apparatus.
[0041] Through implementation of the present subject matter, a
number of technical advantages may be obtained. These include
maximizing the available evaporator surface area for reduced energy
consumption of a sealed system, by ensuring a flooded evaporator(s)
section, providing a low cost method of monitoring an evaporator(s)
for superheat; permitting the use of a single channel to an
embedded controller for monitoring temperature differential;
allowing for compensation of sealed system performance due to
ambient factors such as air density (atmospheric pressure), and air
temperature and humidity; and permitting active charge management
in a multiple evaporator system. In addition, implementation of the
present subject matter provides reduced energy consumption and a
more consistently performing system in all ambient conditions.
[0042] An embodiment of the present invention can also be embodied
in the form of computer program code, for example, whether stored
in a storage medium, loaded into and/or executed by a computer, or
transmitted over some transmission medium, such as over electrical
wiring or cabling, through fiber optics, or via electromagnetic
radiation, wherein, when the computer program code is loaded into
and executed by a computer, the computer becomes an apparatus for
practicing the invention. When implemented on a general-purpose
microprocessor, the computer program code segments configure the
microprocessor to create specific logic circuits. The technical
effect of the executable code is to facilitate prediction and
optimization of modeled devices and systems.
[0043] This written description uses examples to disclose the
invention, including the best mode, and also to enable any person
skilled in the art to practice the invention, including making and
using any devices or systems and performing any incorporated
methods. The patentable scope of the invention is defined by the
claims, and may include other examples that occur to those skilled
in the art. Such other examples are intended to be within the scope
of the claims if they include structural elements that do not
differ from the literal language of the claims, or if they include
equivalent structural elements with insubstantial differences from
the literal languages of the claims.
* * * * *