U.S. patent application number 12/001491 was filed with the patent office on 2008-06-26 for method of controlling multiple refrigeration devices.
Invention is credited to Timothy Dean Swofford.
Application Number | 20080148751 12/001491 |
Document ID | / |
Family ID | 39540944 |
Filed Date | 2008-06-26 |
United States Patent
Application |
20080148751 |
Kind Code |
A1 |
Swofford; Timothy Dean |
June 26, 2008 |
Method of controlling multiple refrigeration devices
Abstract
A refrigeration system for use with a plurality of temperature
controlled cases is disclosed. The refrigeration system includes a
cooling system having at least one compressor and a condenser for
supplying liquid refrigerant to a cooling element associated with
each case. Each cooling element receives liquid refrigerant through
a liquid refrigerant supply line and returns vapor refrigerant
through a suction line. The refrigeration system further includes a
control module having a stored reference temperature (T ref) for
each case, a temperature sensor disposed in each case for
generating a signal representative of the actual temperature within
the case (T act), and an expansion device provided at the liquid
refrigerant supply line side of each case. The control module
compares T ref with T act and moves the expansion devices between
an open position and a closed position accordingly to obtain or
maintain the desired temperature in each temperature controlled
case.
Inventors: |
Swofford; Timothy Dean;
(Midlothian, VA) |
Correspondence
Address: |
FOLEY & LARDNER LLP
777 EAST WISCONSIN AVENUE
MILWAUKEE
WI
53202-5306
US
|
Family ID: |
39540944 |
Appl. No.: |
12/001491 |
Filed: |
December 11, 2007 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
60869657 |
Dec 12, 2006 |
|
|
|
Current U.S.
Class: |
62/210 ; 62/246;
62/252 |
Current CPC
Class: |
F25D 2700/12 20130101;
F25B 2700/1933 20130101; F25B 2600/21 20130101; F25B 2400/22
20130101; F25B 41/31 20210101; F25B 5/02 20130101; F25B 1/10
20130101; F25B 2600/2513 20130101; F25B 2700/21151 20130101 |
Class at
Publication: |
62/210 ; 62/246;
62/252 |
International
Class: |
A47F 3/04 20060101
A47F003/04; F25B 41/00 20060101 F25B041/00 |
Claims
1. In a refrigeration system having at least one compressor and a
condenser for supplying liquid refrigerant to a plurality of
cooling elements, the cooling element being associated with
different temperature controlled cases for maintaining a desired
temperature in each temperature controlled case, each cooling
element receiving liquid refrigerant through a liquid refrigerant
supply line and returning vapor refrigerant through a suction line,
the improvement comprising: a control module having a case
temperature monitoring function including a case temperature
setpoint for each temperature controlled case, and a superheat
monitoring function including a superheat temperature setpoint for
each temperature controlled case; a sensor disposed in each
temperature controlled case and configured to provide the control
module with a signal representative of the actual case temperature
within each temperature controlled case; at least one of a
temperature sensor and a pressure sensor proximate an outlet of the
cooling elements and configured to provide the control module with
a signal representative of an actual superheat temperature of the
refrigerant exiting the cooling element; and an expansion device
provided at the supply line of each temperature controlled case,
wherein the control module compares the signals received from the
sensors with the temperature setpoints for the respective
temperature controlled cases and moves the expansion devices
between an open position and a closed position in response to the
signals to obtain or maintain a desired case temperature and a
desired superheat temperature.
2. The system of claim 1 wherein the case temperature monitoring
function of the control module is further configured to modulate
the position of each expansion device when in the open position so
that a flow rate of refrigerant through the cooling device
corresponds to the desired case temperature.
3. The system of claim 2 wherein the temperature controlled cases
comprises a first temperature controlled case and a second
temperature controlled case, the first temperature controlled case
being configured to operate as a low temperature case and the
second temperature controlled case being configured to operate as a
medium temperature case.
4. The system of claim 3 wherein the first temperature controlled
case is configured to be maintained at a temperature within a range
of approximately negative 15 degrees F. to approximately 15 degrees
F.
5. The system of claim 3 wherein the second temperature controlled
case is configured to be maintained at a temperature within a range
of approximately 20 degrees F. to approximately 40 degrees F.
6. The system of claim 2 wherein the superheat monitoring function
of the control module is configured to limit an open position of
the expansion device to maintain the desired superheat temperature
and prevent liquid refrigerant carryover at the outlet of the
cooling element.
7. The system of claim 6 wherein the sensing arrangement comprises
a temperature sensor and a pressure sensor located at the suction
line side of the cooling element.
8. The system of claim 6 wherein the sensing arrangement comprises
a first temperature sensor located proximate an inlet of the
cooling element and a second temperature sensor located proximate
an outlet side of the cooling element.
9. The system of claim 1 wherein the expansion device is a
superheat control valve.
10. A refrigeration device comprising: a case having a space
configured to receive products to be cooled; a case temperature
sensor located within the space; at least one cooling element
coupled to the case and configured to provide cooling to the space;
a refrigeration system having a supply line and a return line
configured to circulate a refrigerant through the cooling element;
a superheat temperature sensor arrangement coupled to at least one
of the supply line and the return line; an expansion device coupled
to the supply line; and a control module operable to maintain a
desired temperature within the space by moving the expansion device
between an open position and a closed position based on a signal
received from the case temperature sensor and by modulating the
expansion device when in the open position based on a signal
received from the superheat temperature sensor arrangement.
11. The device of claim 10 wherein the superheat temperature sensor
arrangement is a temperature/pressure sensing arrangement
comprising a temperature sensor and a pressure sensor located at
the return line.
12. The device of claim 10 wherein the sensor arrangement is a
temperature/temperature sensing arrangement comprising a second
temperature sensor located proximate an inlet of the cooling
element and a third temperature sensor located at the return
line.
13. The device of claim 10 wherein the expansion device is a
superheat control valve.
14. The device of claim 10 wherein the refrigeration device is
coupled to a second refrigeration device and the two refrigeration
devices are coupled in parallel and share a common refrigeration
system.
15. The device of claim 14 wherein the refrigeration device
operates as a low temperature refrigeration device and the second
refrigeration device operates as a medium temperature refrigeration
device.
16. The device of claim 15 wherein the refrigeration system
provides liquid refrigerant to the supply line based on the cooling
requirements of the first refrigeration device rather than the
cooling requirements of the second refrigeration device.
17. A method of controlling temperature within more than one
temperature controlled case coupled to a shared refrigeration
system and operating at different desired temperatures, the method
comprising: providing a plurality of cases, each having a space
configured to receive products to be cooled; providing a case
temperature sensor located within the space of each case; providing
at least one cooling element coupled to each case and configured to
provide cooling to the space of the respective case; providing a
refrigeration system having refrigerant supply line and a
refrigerant suction line; coupling the cooling elements in parallel
to the refrigeration system; providing a superheat temperature
sensor arrangement at one of the supply line and the suction line
for each case; providing a superheat valve for each case coupled at
the supply line; and providing a control module operable to
maintain the desired temperatures within each space by moving the
respective superheat valve between an open position and a closed
position based on a signal received from the respective case
temperature sensor and by modulating the respective superheat valve
when in the open position based on a signal received from the
respective superheat temperature sensor arrangement.
18. The method of claim 17 further comprising operating at least
one of the plurality of cases as a low temperature case and
operating at least another one of the plurality of cases as a
medium temperature case.
19. The method of claim 17 further comprising utilizing the sensor
arrangement and the control module to provide a defrost mode.
20. A refrigeration system, comprising: a cooling system having at
least one compressor and a condenser for supplying refrigerant to a
plurality of parallel branch lines, each branch line having a
supply line with a superheat valve and a return line coupled to a
separate temperature controlled case, each temperature controlled
case having a cooling element through which the refrigerant is
configured to flow to provide cooling to a space within the
temperature controlled space; a control module having a case
temperature setpoint representative of a desired storage
temperature within the space for each temperature controlled case,
where the temperature setpoint for at least one of the temperature
controlled cases is different from the setpoint for the other
temperature controlled cases, and a superheat temperature setpoint
representative of a desired refrigerant superheat temperature
proximate the outlet of the cooling element; a case temperature
sensor disposed in each temperature controlled case and configured
to provide the control module with a signal representative of the
actual case temperature within each temperature controlled case; a
superheat temperature sensor arrangement configured to provide a
signal representative of an actual superheat temperature of the
refrigerant proximate an outlet of the cooling element; wherein the
control module is operable to compare the signal representative of
the actual case temperature with the case temperature setpoint for
each temperature controlled case, and to compare the signal
representative of the actual superheat temperature with the
superheat temperature setpoint, and provide an output signal to
each superheat valve to obtain or maintain the desired storage
temperature in each temperature controlled case and to maintain the
desired refrigerant superheat temperature, so that a single cooling
system is operable to maintain different storage temperatures in a
plurality of temperature controlled cases.
21. The system of claim 20 wherein the control module is a
centralized control module operable for use with all of the
temperature controlled case.
Description
CROSS REFERENCE TO RELATED PATENT APPLICATIONS
[0001] This application claims the benefit under 35 U.S.C. 119(e)
of U.S. Provisional Application No. 60/869,657, having a filing
date of Dec. 12, 2006, titled "Method of Controlling Multiple
Refrigeration Devices," the complete disclosure of which is hereby
incorporated by reference.
BACKGROUND
[0002] The present disclosure relates to a refrigeration system for
and a method of controlling temperature within more than one
refrigeration device (e.g. temperature controlled case,
refrigerated storage unit, merchandiser, cooler, etc.). More
particularly, the present disclosure relates to a refrigeration
system for and a method of controlling temperature within more than
one refrigeration device operating at different temperatures (e.g.,
a low temperature device, a medium temperature device, etc.).
[0003] It is generally known to provide refrigeration devices
(e.g., temperature controlled cases, refrigerated storage units,
merchandisers, coolers, etc.) having a refrigeration system for
circulating a refrigerant or coolant through one or more cooling
elements within the device to maintain items (such as food products
and the like) within a certain desirable temperature range. It is
also generally known to provide a single refrigeration system
(e.g., refrigeration rack, etc.) for controlling temperature within
more than one refrigeration device. Such a configuration is most
commonly used in a commercial setting, such as a grocery store or
supermarket.
[0004] Refrigeration systems configured to be used with more than
one refrigeration device generally utilize one or more compressors
in parallel and at least one condenser. Refrigerant vapor enters
the compressors and is discharged as a highly pressurized
superheated refrigerant vapor, which is in turn passed through the
condenser during which time the refrigerant undergoes a phase
change from vapor to liquid. Each refrigeration device is typically
provided with a separate cooling element (e.g., evaporator, cooling
coil, etc.) configured to receive the liquid refrigerant discharged
from the condenser. As the liquid refrigerant passes through the
cooling element, the liquid refrigerant evaporates to the gaseous
state with absorption of heat. A fan blows air over the cooling
elements and into the display area of the refrigeration device,
while the refrigerant vapor returns to the compressors to begin the
cycle again.
[0005] The desirable temperature range for each refrigeration
device will vary depending on the type of items that are received
by the particular refrigeration device. For example, the
refrigeration device may be a "low temperature" refrigeration
device or a "medium temperature" refrigeration device. Low
temperature refrigeration devices are generally used to display or
otherwise support items (e.g., frozen food products, etc.) at a
temperature ranging between approximately -15 degrees Fahrenheit
(F) and approximately 15 degrees F. Medium temperature
refrigeration devices are generally used to display or otherwise
support items (e.g., fresh food products, etc.) at a temperature
ranging between approximately 20 degrees F. and 40 degrees F.
[0006] To maintain the refrigeration devices at the desirable
temperature range, the refrigeration system typically includes a
control module configured to regulate the positioning of an
expansion device (e.g., valve, etc.) to modulate the flow of
refrigerant that is supplied to the refrigeration devices. In
conventional systems, an evaporator pressure regulator ("EPR")
valve on the suction side adjusts the flow of refrigerant gas to
maintain a preset suction pressure across the valve, which in turn
maintains a desired temperature with the refrigeration device.
During a cooling mode, the EPR valve is generally open or
modulating. Use of an EPR valve may not be the most efficient and
accurate way of regulating temperature.
[0007] Accordingly, it would be desirable to provide a
refrigeration system that can regulate temperature within a
refrigeration device more efficiently and/or accurately than with
an EPR valve. It would also be desirable to provide a refrigeration
system with an expansion device (e.g., superheat device, etc.) at
an inlet side (i.e., liquid refrigerant side) of a cooling element.
It would further be desirable to provide a refrigeration system
capable of regulating temperature in more than one refrigeration
device. It would also be desirable to provide a refrigeration
system capable of regulating temperature in refrigeration devices
configured to operate at different temperatures (e.g., a low
temperature cooling mode, a medium temperature cooling mode, etc.).
It would be further desirable to provide a refrigeration system
having a control module that modulates the flow of refrigerant
through a cooling element based at least in part on a signal
representative of the actual temperature within the refrigeration
device.
[0008] Accordingly, it would be desirable to provide a
refrigeration system for a temperature controlled case having any
one or more of these or other desirable features.
SUMMARY
[0009] According to one embodiment, a refrigeration system includes
at least one compressor and a condenser for supplying liquid
refrigerant to a plurality of cooling elements. The cooling
elements are associated with different temperature controlled cases
for maintaining a desired temperature range in each temperature
controlled case. Each cooling element receives liquid refrigerant
through a liquid refrigerant supply line and returns vapor
refrigerant through a suction line. The refrigeration system
further includes a control module having a temperature setpoint for
each temperature controlled case, a sensor disposed in each
temperature controlled case and configured to provide the control
module with a signal representative of the actual temperature
within each temperature controlled case, and an expansion device
provided at the liquid refrigerant supply line side of each
temperature controlled case. The control module compares the
signals received from the sensors with the temperature setpoints
for the respective temperature controlled case and moves the
expansion devices between an open position and a closed position in
response to the signals.
[0010] According to another embodiment, a refrigeration device
includes a case having a space configured to receive products to be
cooled, a temperature sensor located within the space, at least one
cooling element coupled to the case and configured to provide
cooling to the space, a refrigeration system having a supply line
and a return line configured to circulate a refrigerant through the
cooling element, a sensor arrangement coupled to at least one of
the supply line and the return line, an expansion device coupled to
the supply line, and a control module operable to maintain a
desired temperature within the space by moving the expansion device
between an open position and a closed position based on a signal
received from the temperature sensor and by modulating the
expansion device when in the open position based on a signal
received from the sensor arrangement.
[0011] According to another embodiment, a refrigeration system
includes at least one compressor and a condenser for supplying
liquid refrigerant to a plurality of cooling elements. The cooling
elements are associated with different temperature controlled cases
for maintaining a desired temperature range in each temperature
controlled case. Each cooling element receives liquid refrigerant
through a liquid refrigerant supply line and returns vapor
refrigerant through a suction line. The refrigeration system
further includes a control module for each temperature controlled
case. The control modules have a temperature setpoint for the
particular temperature controlled case. The refrigeration system
further includes a sensor disposed in each temperature controlled
case and configured to provide the control module with a signal
representative of the actual temperature within each temperature
controlled case, and an expansion device provided at the liquid
refrigerant supply line side of each temperature controlled case.
The control modules compare the signals received from the sensors
with the temperature setpoints for the respective temperature
controlled case and move the expansion devices between an open
position and a closed position in response to the signals. Each
control module changes the positioning of the expansion device
independent of the remaining expansion valves.
[0012] According to another embodiment, a method of controlling
temperature within more than one temperature controlled case
coupled to a shared refrigeration system and operating at different
desired temperatures includes the steps of providing a plurality of
cases, each having a space configured to receive products to be
cooled, providing a temperature sensor located within the space of
each case, providing at least one cooling element coupled to each
case and configured to provide cooling to the space of the
respective case, providing a refrigeration system having
refrigerant supply line and a refrigerant suction line, coupling
the cooling elements in parallel to the refrigeration system,
providing a sensor arrangement at one of the supply line and the
suction line for each case, providing a superheat valve for each
case coupled at the supply line, and providing a control module
operable to maintain the desired temperatures within each space by
moving the respective superheat valve between an open position and
a closed position based on a signal received from the respective
temperature sensor and by modulating the respective superheat valve
when in the open position based on a signal received from the
respective sensor arrangement.
[0013] According to another embodiment, a refrigeration system
includes a cooling system having at least one compressor and a
condenser for supplying refrigerant to a plurality of parallel
branch lines. Each branch line has a supply line with a superheat
valve and a return line coupled to a separate temperature
controlled case. Each temperature controlled case has a cooling
element through which the refrigerant is configured to flow to
provide cooling to a space within the temperature controlled space.
The refrigeration system also includes a control module having a
temperature setpoint representative of a desired storage
temperature within the space for each temperature controlled case.
The temperature setpoint for at least one of the temperature
controlled cases is different from the setpoint for the other
temperature controlled cases. The refrigeration system further
includes a sensor disposed in each temperature controlled case and
configured to provide the control module with a signal
representative of the actual temperature within each temperature
controlled case. The control module is operable to compare the
signal representative of the actual temperature with the
temperature setpoint for each temperature controlled case, and to
provide an output signal to each superheat valve to obtain or
maintain the desired storage temperature in each temperature
controlled case, so that a single cooling system is operable to
maintain different storage temperatures in a plurality of
temperature controlled cases.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a schematic diagram of a system having multiple
refrigeration devices coupled to a refrigeration system according
to an exemplary embodiment.
[0015] FIG. 2 is a schematic image of a side elevation view of a
temperature controlled case according to an exemplary
embodiment.
[0016] FIGS. 3A-3D are schematic images of a block diagram of a
refrigeration system for a temperature controlled case according to
exemplary embodiments.
[0017] FIG. 4 is a schematic diagram of a system having multiple
refrigeration devices coupled to a refrigeration system according
to another exemplary embodiment.
DETAILED DESCRIPTION
[0018] Referring generally to the FIGURES, a refrigeration system
for controlling the temperature within more than one refrigeration
device, such as a plurality of temperature controlled cases, is
shown according to one embodiment. The refrigeration system
generally has one or more compressors (e.g., a rack of compressors,
etc.) and a condenser. The refrigeration system is in fluid
communication with an outlet conduit or supply line (e.g.,
manifold, liquid refrigerant line, etc.) to which a cooling element
(e.g., coil, finned-coil, heat exchanger, flow-through pan, etc.)
of each temperature controlled case is coupled to in parallel. An
expansion device (e.g., a throttling device such as a superheat
valve, etc.) is provided at the inlet side of each cooling element.
Suitable sensors (e.g., a combination of temperature and pressure
sensors, etc.) are provided for controlling (e.g., modulating,
etc.) the circulation of a fluid (such as a refrigerant or coolant)
through the cooling element to maintain the temperature of
products, such as food products within a storage area of the case,
at a relatively constant storage temperature. The system further
includes one or more control modules that interface with the
sensors and the expansion device to achieve a desired temperature
range and maintain the storage area of the case within such
temperature range during a cooling mode.
[0019] According to an exemplary embodiment, the refrigeration
system is coupled to a plurality of temperature controlled cases,
at least one of which is configured to operate at a different
temperature than another case in the system. For example, a first
temperature controlled case may be configured to operate as a low
temperature case, while a second temperature controlled case may be
configured to operate as a medium temperature case. Low temperature
cases are generally used to display or otherwise support items
(e.g., frozen food products, etc.) at a temperature ranging between
approximately negative (-) 15 degrees Fahrenheit (F.) and
approximately 15 degrees F., and may include cases operating at a
variety of "low" temperatures for various product storage
requirements (for example, ice cream cases and frozen food cases,
where the ice cream case typically operates at a temperature that
is lower (e.g. 8-10 degrees F., etc.) than the frozen food case).
Medium temperature cases are generally used to display or otherwise
support items (e.g., fresh food products, etc.) at a temperature
ranging between approximately 20 degrees F. and approximately 40
degrees F., and may include cases operating at a variety of
"medium" temperatures for various product storage requirements (for
example, meat cases, dairy cases and produce cases, where the meat
case typically operates at a temperature that is lower (e.g. 8-10
degrees F., etc.) than the dairy case, and the dairy case typically
operates at a temperature that is lower than produce case).
According to the various alternative embodiments, the cases may be
configured to operate within any range of temperature that may be
desirable. In such an embodiment, the refrigeration system is setup
to maintain the desired temperature in the lowest temperature case
in the system (e.g., a low temperature case, etc.). The same
refrigeration system can be used to regulate the temperature of a
higher temperature case (e.g., a medium temperature case, etc.) by
modulating the expansion device utilizing the above-mentioned
control module and suitable sensors, so that the expansion device
reduces the flow of refrigerant through the cooling element in the
case so that the temperature within the case increases to a desired
higher operating temperature for a particular case.
[0020] According to an exemplary embodiment, the same refrigeration
system can be used more efficiently and accurately to regulate the
temperature of one or more higher temperatures case by having a
configuration capable of completely closing the expansion device
for a given case. According to such an embodiment, the control
module has a case temperature monitoring function and a super heat
temperature monitoring function. In the case temperature monitoring
function, the control module maintains a desired temperature within
a particular case by comparing an actual temperature reading within
the case (T act) to a predetermined reference range or setpoint
(e.g., a temperature range or setpoint, etc.) programmed or
otherwise stored within the control module (T ref) for each case.
If T act is less than T ref, the control module closes the
expansion device by sending a signal to the expansion device
provided at the inlet side of the cooling element. If T act is
greater than T ref, the control module opens the expansion device
provided at the inlet side of the cooling element and modulates the
positioning of the expansion device using the remaining sensor
devices so as not to go below a preset superheat valve. In the
superheat temperature monitoring function, the control module also
monitors a superheat temperature of the refrigerant proximate the
outlet of the cooling element to ensure that refrigerant exiting
the cooling element is in a vapor state (e.g. to prevent damage to
the compressor, etc.). The control module also includes a superheat
setpoint (typically about 5 degrees F. for low temperature cases
and about 8 degrees F. for medium temperature cases) and sends a
signal to the expansion device when appropriate to prevent the
expansion device from opening to a point that might correspond to
liquid refrigerant exiting the cooling coil.
[0021] According to an exemplary embodiment, the sensor device used
to obtain T act is a temperature probe located within each case.
Utilizing a temperature probe (or other suitable sensor) to
determine the actual temperature of a case, and to send a signal
representative of the measured temperature to a control module
operably coupled to a throttling device (e.g., superheat valve,
etc.), may improve efficiency and accuracy of temperature
regulation with the case in comparison to a system utilizing an
evaporator pressure regulator (EPR) valve for temperature
regulation. Advantageously, the above-described system may be added
to an existing system (e.g., provided as a retrofit, etc.)
utilizing an EPR valve in an attempt to improve efficiency and
accuracy of temperature regulation with the case. According to such
an embodiment, the EPR valve can be set to an open position so that
the EPR valve has no effect on the flow of refrigerant through the
cooling element.
[0022] Providing the expansion device (e.g., superheat valves,
etc.) on the inlet side of the cooling elements, rather than on the
suction side (e.g., gas line, etc.) of the cooling elements,
advantageously allows the refrigeration system to be more
effectively used when regulating temperature within cases of
different temperature.
[0023] Referring to FIG. 1, a system 100 is shown schematically as
generally including a first refrigeration device 10a, a second
refrigeration device 10b and a third refrigeration device 10c
coupled to a shared (e.g., central, common, etc.) refrigeration
system 20. The refrigeration system 20 circulates a refrigerant
through a closed loop system including one or more compressors for
compressing a refrigerant vapor, a condenser for cooling and
condensing the compressed refrigerant vapor, and an expansion
metering device (e.g. throttle valve, electronic expansion valve,
etc.--shown as a superheat valves 26a, 26b, 26c) for "expanding"
the liquid refrigerant to a low-temperature saturated liquid-vapor
mixture for use in one or more cooling elements for cooling an
airspace and products within the first refrigeration device 10a,
the second refrigeration device 10b and the third refrigeration
device 10c. While not illustrated in FIG. 1, the refrigeration
system 20 generally includes the one or more compressors and the
condenser, while the first temperature controlled case 10a, the
second temperature controlled case 10b, and the third temperature
controlled case 10c each include one or more cooling elements.
[0024] According to an exemplary embodiment, the refrigerant flows
through a refrigerant supply line 28 (e.g., discharge manifold,
liquid line, etc.) to superheat valves 26a, 26b, 26c at a first
flow rate and is expanded by the superheat valves 26a, 26b, 26c to
form a liquid-vapor mixture at a "saturation temperature" within
the cooling element(s) to maintain the temperature of the food
products at a desired storage or display temperature, consistent
with store or industry food safety codes or guidelines.
[0025] As the saturated liquid-vapor mixture of refrigerant
progresses through the cooling element(s) of the respective
refrigeration devices 10a, 10b, 10c and absorbs heat from the air
circulated from an airspace within the respective refrigeration
devices 10a, 10b, 10 c, the vapor percentage of the liquid-vapor
mixture increases, and usually becomes completely vaporized. When
the refrigerant is completely vaporized within a portion of the
cooling element(s) (e.g. usually at or near an outlet portion of
the cooling element, such as the last one or several tube passes of
a coil), the refrigerant temperature increases above the
refrigerant's saturation temperature as the refrigerant continues
to circulate through the cooling element(s). The amount of
temperature increase above the saturation temperature is referred
to herein as the "superheat temperature." The vapor refrigerant is
discharged from the cooling element(s) and flows through a suction
line 30 (e.g., vapor return line, etc.) back to the compressors of
the refrigeration system 20 to start the cycle again.
[0026] Each refrigeration device (i.e., the first refrigeration
device 10a, the second refrigeration device 10b and the third
refrigeration device 10c) may be configured to operate at the same
temperature, or alternatively, may be configured to operate at
different temperatures relative to one or more of the other
refrigeration devices. To assist in maintaining the refrigeration
devices at the desired temperatures, system 100 is further shown as
including a control module 50. The function of control module 50 is
to open, close, and/or modulate the position of the superheat
valves 26a, 26b, 26c to maintain the actual temperature within a
desired temperature range and to maintain a superheat temperature
of the refrigerant within a desired temperature range.
[0027] As detailed below, the control module 50 includes a suitable
computing device configured to receive signals representative of
temperature and pressure at various locations throughout the
system. These signals are used by the control module 50 to modulate
the positioning of superheat valves 26a, 26b, 26c to maintain the
desired temperatures. To improve efficiency, particularly when at
least one of the refrigeration devices 10a, 10b, 10c is configured
to operate at a different (e.g., higher, etc.) temperature than
another device, the control module 50 is also able to open and/or
close the superheat valves 26a, 26b, 26c based on signals
representative of the actual temperature within the airspace of
each refrigeration device 10a, 10b, 10c, and based on signals
representative of the superheat temperature of the refrigerant
exiting the cooling element. According to an exemplary embodiment,
a temperature sensing arrangement for maintaining the air (and
product) temperature within the case is shown as including a first
temperature probe 56a, a second temperature probe 56b, and a third
temperature probe 56c at the refrigeration devices 10a, 10b, 10c
respectively for measuring the actual temperature within the
devices.
[0028] In the case temperature monitoring mode of the control
module, the temperature probes 56a, 56b, 56c provide a signal
representative of actual temperature of the respective
refrigeration devices (T act). Programmed or otherwise stored
within the control module 50 is a separate predetermined desired
range or setpoint for the temperature of each device (T ref). The
control module 50 compares T act to T ref and adjusts (e.g., opens,
closes, etc.) the superheat valves 26a, 26b, 26c accordingly. For
example, if the temperature probe 56a provides a signal to the
control module 50 for T act that is greater than the T ref for the
refrigeration device 10a, then the control module 50 will open the
superheat valve 26a (or maintain the superheat valve 26a in an open
position) to allow liquid refrigerant to passes through the cooling
element. Similarly, if the temperature probe 56a provides a signal
to the control module 50 for T act that is less than the T ref for
the refrigeration device 10a, then control module 50 will close the
superheat valve 26a (or maintain the superheat valve 26a in a
closed position) to restrict the amount of liquid refrigerant
passing through the cooling elements.
[0029] Referring to FIG. 2, a refrigeration device is shown
according to an exemplary embodiment as a temperature controlled
case 10. For the sake of brevity only one refrigeration device is
described herein. It should be noted that the case 10 may be used
for any of the refrigeration devices 10a, 10b, 10c. According to
the various alternative embodiments, one or more the refrigeration
devices 10a, 10b, 10c may have a different configuration than that
described herein or than one or more of the other devices in the
system.
[0030] The case 10 is shown as a rear-access, service-type case,
but may be any suitable enclosure for maintaining a temperature
controlled environment for the storage of objects such as food
products and the like (such as open front or open top cases, closed
door cases, etc.). The case 10 is shown to include a product
support surface 12 within an airspace 14 for storage of products
16, and cooling element(s) 40 configured to cool air circulated
with the airspace 14 by a fan 18. Liquid refrigerant discharged
from the refrigeration system 20 enters the cooling element 40
through the refrigerant supply line 28, while vapor refrigerant
exits the cooling element 40 through the suction line 30. FIG. 1
also illustrates the positioning of the temperature probe 56
according to an exemplary embodiment. According to various
alternative embodiments, the cooling element(s) may be positioned
at any suitable location within the airspace and the air may be
circulated by any type of forced or natural circulation.
[0031] Referring to FIGS. 3A-3D, the superheat monitoring function
of the control module 50, used to modulate the position of the
superheat valve during a cooling mode (and/or a defrost mode) to
maintain a desired superheat temperature of the refrigerant exiting
the cooling element, is shown according to an exemplary embodiment.
Control module 50 includes a suitable computing device (such as a
microprocessor or programmable logic controller 52) configured to
receive signals representative of temperature and/or pressure from
the components of the case and to provide output signals for
controlling the position of the superheat valve 26 provided at the
inlet side of the cooling element 40 to maintain the superheat
temperature of the refrigerant within a desired range. The
superheat monitoring function of the control element 50 is intended
to limit the opening of the superheat valve 26 to prevent an
excessive amount of refrigerant from flowing through the cooling
coil 40 and resulting in liquid carryover at the outlet of the
cooling element 40. In other words, if the case temperature
monitoring function of the control module calls for cooling the
case by opening the superheat valve 26, the superheat monitoring
function of the control element is intended to ensure that the
superheat valve open position is limited to a point that will
maintain the refrigerant in a superheated vapor state at the outlet
of the cooling element (e.g. by at least approximately 5-8 degrees
F. or more). If the expansion device is opened too far (e.g. in an
attempt to lower the temperature within the case), then the heat
available within the case may not be sufficient to vaporize all of
the refrigerant passing through the cooling element. The superheat
monitoring function of the control element monitors the superheat
temperature of the refrigerant exiting the cooling element and
limits the extent to which the expansion device can be opened by
the case temperature monitoring function of the control module, so
that refrigerant vapor in a superheated state is maintained at the
cooling element outlet.
[0032] Referring to FIGS. 3A and 3C in particular, a superheat
temperature sensing arrangement for maintaining the superheat
temperature of the refrigerant exiting the cooling coil 40 is shown
as including a temperature/pressure sensing arrangement including a
temperature sensor 32 and a pressure sensor 34 provided on the
refrigerant return line 30 (e.g. "suction" line, etc.) adjacent to
the exit of the cooling element(s) 40. The pressure sensor 34
provides a signal representative of refrigerant pressure to the
control module 50, which calculates a corresponding saturation
temperature (T sat) of the refrigerant at the exit of the cooling
element(s) 40. The temperature sensor 32 provides a signal
representative of actual temperature of the refrigerant at the exit
of the cooling element(s) 40 (T exit). The control module 50
calculates the difference between T exit and T sat to determine the
actual superheat temperature of the refrigerant (i.e. the
temperature difference of the superheated refrigerant vapor above
the refrigerant's saturation temperature at that location). The
control module 50 compares the actual superheat temperature of the
refrigerant to a predetermined desired range or setpoint for the
superheat temperature (e.g. at least approximately 5 degrees F. for
low temperature cases and 8 degrees F. for medium temperature
cases) and sends an output signal to modulate the position of the
superheat valve 26 to attain or maintain the desired superheat
temperature at the exit of the cooling element(s) 40. According to
one exemplary embodiment, the temperature sensor 32 is a
commercially available thermistor (but could be a thermocouple or
RTD or the like) and the pressure sensor 34 is a commercially
available pressure transducer.
[0033] Referring to FIGS. 3B and 3D in particular, an alternative
superheat temperature monitoring function is shown to include a
temperature/temperature sensing arrangement including a first
temperature sensor 36 located at an inlet area of the cooling
element(s) (e.g. on a first pass of a coil 42 of a cooling element,
etc.) and a second temperature sensor 32 located adjacent to the
exit of the cooling element(s) 40. The first temperature sensor 36
is intended to provide a signal that is reasonably representative
of the saturation temperature (T sat) of the refrigerant to the
control module 50. The second temperature sensor 32 is intended to
provide a signal representative of the actual temperature of the
refrigerant at the exit of the cooling element(s) 40 (T exit). The
control module 50 calculates the difference between T exit and T
sat to determine the actual superheat temperature of the
refrigerant. The control module 50 compares the actual superheat
temperature of the refrigerant to a predetermined desired
(reference) range or setpoint for the superheat temperature (e.g.
at least approximately 5 degrees F. for low temperature cases and 8
degrees F. for medium temperature cases) and sends an output signal
to modulate the position of the superheat valve to attain or
maintain the desired superheat temperature at the exit of the
cooling element. According to alternative embodiments, the
temperature and/or pressure sensors may be provided at any suitable
location and on any suitable component to provide signals
sufficient to control the superheat temperature of the refrigerant
as the refrigerant passes through the cooling element.
[0034] The pressure/temperature arrangement and the
temperature/temperature arrangement detailed above may be used to
modulate the positioning of the superheat valve 26 during the
cooling mode (and/or a defrost mode), and is intended to limit the
extent to which the superheat valve may be opened by the case
temperature monitoring function of the control element to prevent
liquid carryover at the exit of the cooling element. According to
the various alternative embodiments, such pressure/temperature and
temperature/temperature arrangements may be replaced or
supplemented with any suitable sensing arrangement capable of
providing signals to the control module 50 that can be used to
modulate the positioning of the superheat valve 26 to maintain a
desired superheat temperature at the outlet of the cooling
element(s) 40.
[0035] In addition to the pressure/temperature and/or
temperature/temperature arrangement used to modulate the
positioning of the superheat heat valve in the superheat
temperature monitoring function of the control module, case 10
further includes a case temperature sensing arrangement, shown as
the temperature probe 56, suitable for measuring the actual
temperature within the case 10 and sending a signal representative
of that value to the control module 50 for opening and/or closing
the superheat valve 26 in the case temperature monitoring mode of
the control module. Programmed or otherwise stored within the
control module 50 is a separate predetermined desired range or
setpoint for the desired temperature of the case 10. During the
cooling mode, the control module 50 compares the signal received
from temperature probe 56 with the case temperature reference
setpoint. If the signal received from the temperature probe 56 is
greater than the case temperature reference setpoint, the control
module 50 moves the superheat valve 26 to an open position (or
retains the superheat valve in the open position--as limited as
necessary by the superheat temperature monitoring function of the
control module to prevent liquid carryover at the outlet of the
cooling element). If the signal received from the temperature probe
56 is less than the reference setpoint, the control module 50 moves
the superheat valve 26 to a closed position (or retains the
superheat valve in the closed position) to increase the air/product
temperature within the case. The temperature probe 56 may be
provided at any of a number of locations within the case 10 to
provide a signal representative of the temperature of the air space
and/or product stored in the case. According to an exemplary
embodiment, the temperature probe is located where the cooling air
is discharged into the airspace 14.
[0036] The case 10 may also include a defrost system intended to
minimize or generally eliminate the accumulation frost and/or ice
on the surfaces of the cooling element 40. According to an
exemplary embodiment, the case 10 may include a defrost system such
as that disclosed in U.S. Pat. No. 7,275,376 titled "Defrost System
for a Refrigeration Device," the disclosure of which is hereby
incorporated by reference in its entirety. If a defrost system is
provided, the control module 50 may further include a timer 54
(shown in FIGS. 3A-3D) operably coupled to controller 52 for
initiating and terminating a defrost cycle (e.g., mini-defrosts,
etc.) according to a predetermined schedule. Timer 54 may be
adjusted locally or remotely to "tune" or adjust the parameters of
the defrost cycle as necessary due to changing conditions.
[0037] Referring to FIG. 4, system 100 is shown according to
another exemplary embodiment. System 100 illustrated in FIG. 4 is
similar to system 100 illustrated in FIG. 1 in that both systems
are shown as including a first refrigeration device 10a, a second
refrigeration device 10b and a third refrigeration device 10c
coupled to a shared (e.g., central, common, etc.) refrigeration
system 20. Both systems also include one or more compressors for
compressing a refrigerant vapor and a condenser for cooling and
condensing the compressed refrigerant vapor, an expansion metering
device (e.g. throttle valve, electronic expansion valve,
etc.--shown as a superheat valves 26a, 26b, 26c) for "expanding"
the liquid refrigerant to a low-temperature saturated liquid-vapor
mixture for use in one or more cooling elements for cooling an
airspace and products within the first refrigeration device 10a,
the second refrigeration device 10b and the third refrigeration
device 10c. Further, in both systems the first temperature
controlled case 10a, the second temperature controlled case 10b,
and the third temperature controlled case 10c each include one or
more cooling elements. The difference between the exemplary
embodiment illustrated in FIG. 4 and the exemplary embodiment
illustrated in FIG. 1 relates to the control module 50.
[0038] In FIG. 1, a single control module 50 is shown for operating
(e.g., opening, closing, modulating, etc.) superheat valves 26a,
26b and 26c to maintain the temperature in the case within a
desired temperature range, while maintaining the superheat
temperature of the refrigerant within a desired temperature range
at the cooling element outlet for each case. According to the
embodiment illustrated in FIG. 4, each refrigeration system 20 is
provided with a separate control module, shown as a control module
50a, control module 50b and control module 50c, for operating
superheat valves 26a, 26b and 26c respectively. Control modules
50a, 50b and 50c are each configured to receive signals from the
various temperature and/or pressure sensors on the inlet line
and/or outlet line of the cooling element, and the temperature
sensor in the case.
[0039] With reference to all of the FIGURES, a method of
controlling temperature within more than one temperature controlled
case coupled to a refrigeration rack will be described according to
an exemplary embodiment. The method includes providing a plurality
of temperature controlled cases, each having an enclosure with a
space configured to receive products to be cooled, one or more
cooling elements (e.g., coils, etc.) to maintain the temperature of
products in a particular case at a relatively constant storage
temperature, an expansion device (e.g., superheat control valve,
etc.) located at a inlet side (i.e., liquid refrigerant side) of
the cooling element, and suitable sensors measuring temperature
and/or pressure for circulating a refrigerant through the cooling
element. According to the embodiment illustrated, each case
includes a pressure transducer or sensor and a first temperature
sensor provided at a vapor refrigerant return or suction line and a
second temperature sensor provided within the airspace of the case
(or on a simulated product mass within the case). The method
further includes coupling the temperature controlled cases in
parallel to a refrigeration system having one or more compressors,
a condenser and a control module.
[0040] The method further includes programming the control module
to calculate the actual superheat temperature of the refrigerant at
the outlet of the cooling element for each case and to compare the
actual superheat temperature of the refrigerant (based on signals
received from the pressure sensor and the first temperature sensor)
to a predetermined superheat setpoint. The method further includes
regulating (e.g., modulating, etc.) the position of each superheat
control valve based on the comparisons of the actual superheat
temperatures to the predetermined superheat setpoints for
modulating the flow of refrigerant to the cooling elements.
According to an exemplary embodiment, one or more of the cases is
configured to operate at a different temperature than another case.
For example, a first case is configured to operate as a low
temperature case, while a second case is configured to operate as a
medium temperature case. By further way of example, the cases may
all be "low" temperature cases operating at various low
temperatures (e.g. for ice cream, frozen food, etc. applications)
or the cases may all be "medium" temperature cases operating at
various medium temperatures (e.g. for meat, dairy, produce, etc.
applications).
[0041] The method further includes providing the control module
with a predetermined temperature setpoint (T ref) for each case,
which is used in determining whether the expansion devices should
be moved to an open position or a closed position for maintaining a
desired temperature of the air/products within the case, as opposed
to the superheat setpoint which is used to limit the open
positioning of the expansion valves to prevent refrigerant liquid
carryover at the outlet of the cooling element. The method further
includes comparing the signals received from the second temperature
sensor with the predetermined setpoints for each case and opening
and/or closing each expansion device accordingly in view of the
comparison. If the cases include an EPR valve located at the
suction side of the cooling elements, the method further includes
the step of moving the EPR valve to an open position so that it
does not influence temperature regulation with the cases.
[0042] It is also important to note that the construction and
arrangement of the elements of the refrigeration system for a
temperature controlled case as shown schematically in the
embodiments is illustrative only. Although only a few embodiments
have been described in detail in this disclosure, those skilled in
the art who review this disclosure will readily appreciate that
many modifications are possible (e.g., variations in the ranges of
the different cooling modes for a low temperature cooling mode and
a medium temperature cooling mode, variations in superheat
temperature during the different cooling modes, values of
parameters, etc.) without materially departing from the novel
teachings and advantages of the subject matter recited. For
example, the use of a temperature sensor within a refrigeration
device to generate a signal for moving an expansion device at a
inlet side of a cooling element to an open or closed position may
also be used with a stand alone refrigeration device. For such an
embodiment, the refrigeration system 20 may be self-contained
within the case (as shown schematically in FIGS. 3C and 3D) or a
portion of the refrigeration system may be located remotely from
the case (as shown schematically in FIG. 3A-3B).
[0043] It should also be noted that suitable sensors may be
provided within the case or integrally (or otherwise operably
coupled) with the cooling elements(s) to provide input to the
refrigeration control system. For example, one or more temperature
sensing devices (e.g. thermocouples, RTDs, etc.) may be provided at
suitable location(s) within, or on the top side or underside of
shelves or other product support surfaces to provide a signal
representative of temperature of the product support surface and/or
food products to the refrigeration control system. The control
module may include a processor such as a microprocessor,
programmable logic controller or the like for receiving and
monitoring input signals, sending output signals, permitting change
or adjustment of setpoints, providing appropriate indications (e.g.
alarms, status, temperature, fluid flow rates, mode of operation
(such as a first cooling mode or a second cooling mode), etc.) and
to interface with local or remote monitoring equipment or stations.
The control module may also be configured to initiate a conversion
between different cooling modes in any suitable manner.
Accordingly, all such modifications are intended to be included
within the scope of the present inventions. Other substitutions,
modifications, changes and omissions may be made in the design,
operating conditions and arrangement of the preferred and other
exemplary embodiments without departing from the spirit of the
present inventions.
[0044] The order or sequence of any process or method steps may be
varied or re-sequenced according to alternative embodiments. In the
claims, any means-plus-function clause is intended to cover the
structures described herein as performing the recited function and
not only structural equivalents but also equivalent structures.
Other substitutions, modifications, changes and omissions may be
made in the design, operating configuration and arrangement of the
preferred and other exemplary embodiments without departing from
the spirit of the present inventions as expressed in the appended
claims.
* * * * *