US20080148751A1

US20080148751A1 - Method of controlling multiple refrigeration devices

Info

Publication number: US20080148751A1
Application number: US12/001,491
Authority: US
Inventors: Timothy Dean Swofford
Original assignee: Hill Phoenix Inc; Dover Systems Inc
Current assignee: Hill Phoenix Inc; Dover Systems Inc
Priority date: 2006-12-12
Filing date: 2007-12-11
Publication date: 2008-06-26

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.

Description

CROSS REFERENCE TO RELATED PATENT APPLICATIONS

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

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.).
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.
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.
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.
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.
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.
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

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.
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.
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.
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.
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

FIG. 1 is a schematic diagram of a system having multiple refrigeration devices coupled to a refrigeration system according to an exemplary embodiment.

FIG. 2 is a schematic image of a side elevation view of a temperature controlled case according to an exemplary embodiment.

FIGS. 3A-3D are schematic images of a block diagram of a refrigeration system for a temperature controlled case according to exemplary embodiments.

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

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.
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.
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.
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.
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.
Referring to FIG. 1, a system 100 is shown schematically as generally including a first refrigeration device 10 a, a second refrigeration device 10 b and a third refrigeration device 10 c 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 26 a, 26 b, 26 c) 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 10 a, the second refrigeration device 10 b and the third refrigeration device 10 c. 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 10 a, the second temperature controlled case 10 b, and the third temperature controlled case 10 c each include one or more cooling elements.
According to an exemplary embodiment, the refrigerant flows through a refrigerant supply line 28 (e.g., discharge manifold, liquid line, etc.) to superheat valves 26 a, 26 b, 26 c at a first flow rate and is expanded by the superheat valves 26 a, 26 b, 26 c 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.
As the saturated liquid-vapor mixture of refrigerant progresses through the cooling element(s) of the respective refrigeration devices 10 a, 10 b, 10 c and absorbs heat from the air circulated from an airspace within the respective refrigeration devices 10 a, 10 b, 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.
Each refrigeration device (i.e., the first refrigeration device 10 a, the second refrigeration device 10 b and the third refrigeration device 10 c) 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 26 a, 26 b, 26 c to maintain the actual temperature within a desired temperature range and to maintain a superheat temperature of the refrigerant within a desired temperature range.
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 26 a, 26 b, 26 c to maintain the desired temperatures. To improve efficiency, particularly when at least one of the refrigeration devices 10 a, 10 b, 10 c 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 26 a, 26 b, 26 c based on signals representative of the actual temperature within the airspace of each refrigeration device 10 a, 10 b, 10 c, 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 56 a, a second temperature probe 56 b, and a third temperature probe 56 c at the refrigeration devices 10 a, 10 b, 10 c respectively for measuring the actual temperature within the devices.
In the case temperature monitoring mode of the control module, the temperature probes 56 a, 56 b, 56 c 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 26 a, 26 b, 26 c accordingly. For example, if the temperature probe 56 a provides a signal to the control module 50 for T act that is greater than the T ref for the refrigeration device 10 a, then the control module 50 will open the superheat valve 26 a (or maintain the superheat valve 26 a in an open position) to allow liquid refrigerant to passes through the cooling element. Similarly, if the temperature probe 56 a provides a signal to the control module 50 for T act that is less than the T ref for the refrigeration device 10 a, then control module 50 will close the superheat valve 26 a (or maintain the superheat valve 26 a in a closed position) to restrict the amount of liquid refrigerant passing through the cooling elements.
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 10 a, 10 b, 10 c. According to the various alternative embodiments, one or more the refrigeration devices 10 a, 10 b, 10 c may have a different configuration than that described herein or than one or more of the other devices in the system.
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.
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.
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.
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.
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.
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.
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.
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 10 a, a second refrigeration device 10 b and a third refrigeration device 10 c 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 26 a, 26 b, 26 c) 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 10 a, the second refrigeration device 10 b and the third refrigeration device 10 c. Further, in both systems the first temperature controlled case 10 a, the second temperature controlled case 10 b, and the third temperature controlled case 10 c 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.
In FIG. 1, a single control module 50 is shown for operating (e.g., opening, closing, modulating, etc.) superheat valves 26 a, 26 b and 26 c 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 50 a, control module 50 b and control module 50 c, for operating superheat valves 26 a, 26 b and 26 c respectively. Control modules 50 a, 50 b and 50 c 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.
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.
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).
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.
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).
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.
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.

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.