US20090056353A1 - Refrigeration system including a flexible sensor - Google Patents
Refrigeration system including a flexible sensor Download PDFInfo
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- US20090056353A1 US20090056353A1 US11/847,534 US84753407A US2009056353A1 US 20090056353 A1 US20090056353 A1 US 20090056353A1 US 84753407 A US84753407 A US 84753407A US 2009056353 A1 US2009056353 A1 US 2009056353A1
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- sensor
- refrigeration system
- bending
- refrigerant
- measure
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Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25D—REFRIGERATORS; COLD ROOMS; ICE-BOXES; COOLING OR FREEZING APPARATUS NOT OTHERWISE PROVIDED FOR
- F25D29/00—Arrangement or mounting of control or safety devices
- F25D29/008—Alarm devices
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
- G01F1/05—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using mechanical effects
- G01F1/20—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using mechanical effects by detection of dynamic effects of the flow
- G01F1/28—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using mechanical effects by detection of dynamic effects of the flow by drag-force, e.g. vane type or impact flowmeter
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F23/00—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
- G01F23/22—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water
- G01F23/24—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring variations of resistance of resistors due to contact with conductor fluid
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F23/00—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
- G01F23/22—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water
- G01F23/24—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring variations of resistance of resistors due to contact with conductor fluid
- G01F23/241—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring variations of resistance of resistors due to contact with conductor fluid for discrete levels
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F23/00—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
- G01F23/30—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by floats
- G01F23/32—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by floats using rotatable arms or other pivotable transmission elements
- G01F23/36—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by floats using rotatable arms or other pivotable transmission elements using electrically actuated indicating means
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2700/00—Sensing or detecting of parameters; Sensors therefor
- F25B2700/04—Refrigerant level
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2700/00—Sensing or detecting of parameters; Sensors therefor
- F25B2700/13—Mass flow of refrigerants
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2700/00—Sensing or detecting of parameters; Sensors therefor
- F25B2700/13—Mass flow of refrigerants
- F25B2700/135—Mass flow of refrigerants through the evaporator
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25D—REFRIGERATORS; COLD ROOMS; ICE-BOXES; COOLING OR FREEZING APPARATUS NOT OTHERWISE PROVIDED FOR
- F25D17/00—Arrangements for circulating cooling fluids; Arrangements for circulating gas, e.g. air, within refrigerated spaces
- F25D17/04—Arrangements for circulating cooling fluids; Arrangements for circulating gas, e.g. air, within refrigerated spaces for circulating air, e.g. by convection
- F25D17/06—Arrangements for circulating cooling fluids; Arrangements for circulating gas, e.g. air, within refrigerated spaces for circulating air, e.g. by convection by forced circulation
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25D—REFRIGERATORS; COLD ROOMS; ICE-BOXES; COOLING OR FREEZING APPARATUS NOT OTHERWISE PROVIDED FOR
- F25D23/00—General constructional features
- F25D23/003—General constructional features for cooling refrigerating machinery
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25D—REFRIGERATORS; COLD ROOMS; ICE-BOXES; COOLING OR FREEZING APPARATUS NOT OTHERWISE PROVIDED FOR
- F25D2323/00—General constructional features not provided for in other groups of this subclass
- F25D2323/002—Details for cooling refrigerating machinery
- F25D2323/0023—Control of the air flow cooling refrigerating machinery
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25D—REFRIGERATORS; COLD ROOMS; ICE-BOXES; COOLING OR FREEZING APPARATUS NOT OTHERWISE PROVIDED FOR
- F25D25/00—Charging, supporting, and discharging the articles to be cooled
- F25D25/02—Charging, supporting, and discharging the articles to be cooled by shelves
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25D—REFRIGERATORS; COLD ROOMS; ICE-BOXES; COOLING OR FREEZING APPARATUS NOT OTHERWISE PROVIDED FOR
- F25D2700/00—Means for sensing or measuring; Sensors therefor
- F25D2700/02—Sensors detecting door opening
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25D—REFRIGERATORS; COLD ROOMS; ICE-BOXES; COOLING OR FREEZING APPARATUS NOT OTHERWISE PROVIDED FOR
- F25D7/00—Devices using evaporation effects without recovery of the vapour
Definitions
- the present invention relates to refrigeration systems and, particularly, to refrigeration systems that include sensors to measure properties of the refrigeration systems.
- Refrigeration systems are commonly used in a variety of industrial and commercial applications to provide refrigeration to particular portions or processes of the applications.
- commercial refrigeration systems are typically used to cool or freeze food product to permit longer storage of the food product.
- it may be desirable to measure one or more properties of the refrigeration systems e.g., air flow, refrigerant flow, fluid level, etc. to monitor the status of the systems.
- air flow sensors exist that are relatively inexpensive, commercially available, and easily interfaced with control systems.
- hot wire mass air flow (MAF) sensors vane air flow (VAF) meters, and Karman vortex air flow meters are used to measure air flow properties.
- VAF vane air flow
- Karman vortex air flow meters are used to measure air flow properties.
- such sensors are commonly rendered non-functional in the presence of contaminants (e.g., dust, frost, liquid, etc.), making them less desirable for use in refrigeration systems.
- the unit cost of such sensors while being acceptable for industrial and automotive markets, is typically cost prohibitive for commercial refrigeration systems.
- the life cycle of these sensors may be less than desirable.
- the invention provides a refrigeration system including a compressor configured to compress a refrigerant, a condenser in fluid communication with the compressor and configured to remove heat from the refrigerant, and an expansion valve in fluid communication with the condenser and configured to decrease a pressure of the refrigerant.
- the refrigeration system also includes an evaporator in fluid communication with the expansion valve and configured to facilitate heat exchange between the refrigerant and another fluid, and a sensor configured to bend to measure a property of the refrigeration system.
- the sensor includes a flexible substrate and a conductive material applied to the flexible substrate. The conductive material has a resistance that changes in response to bending of the flexible substrate to generate a signal indicative of the property.
- the invention provides a method of measuring a property of a refrigeration system.
- the refrigeration system includes a compressor, a condenser in fluid communication with the compressor, an expansion valve in fluid communication with the condenser, and an evaporator in fluid communication with the expansion valve.
- the method includes providing a sensor including a flexible substrate and a conductive material applied to the flexible substrate.
- the conductive material has a resistance that changes in response to bending of the flexible substrate.
- the method also includes compressing a refrigerant with the compressor, removing heat from the refrigerant with the condenser, decreasing a pressure of the refrigerant with the expansion valve, exchanging heat between the refrigerant and another fluid with the evaporator, and bending the sensor to generate a signal indicative of a property of the refrigeration system.
- the invention provides an evaporative cooler including a housing having a least one vent and configured to contain water, a blower positioned within the housing and configured to draw air through the at least one vent, and an evaporator pad positioned adjacent to the at least one vent.
- the evaporative cooler also includes a pump configured to spray at least a portion of the evaporator pad with the water and a sensor configured to bend to measure a property of the evaporative cooler.
- the sensor includes a flexible substrate and a conductive material applied to the flexible substrate and having a resistance that changes in response to bending of the flexible substrate to generate a signal indicative of the property.
- FIG. 1 is a schematic of a refrigeration system according to an embodiment of the invention.
- FIG. 2A is planar view of a flexible sensor for use with the refrigeration system shown in FIG. 1 .
- FIG. 2B is a planar view of another flexible sensor for use with the refrigeration system shown in FIG. 1 .
- FIG. 3 is a schematic of a flexible sensor configured to measure a liquid flow.
- FIG. 4 is a schematic of a flexible sensor configured to measure an air flow.
- FIG. 5 is a schematic of a flexible sensor configured to measure a fluid level.
- FIG. 6 is a schematic of a flexible sensor configured to measure a load on a secondary structure.
- FIG. 7 is a schematic of another refrigeration system according to an embodiment of the present invention.
- FIG. 8 is a cross-sectional view of an evaporative cooler according to an embodiment of the present invention.
- FIG. 1 illustrates a refrigeration system 10 including a compressor 14 , a condenser 18 , a receiver 22 , an expansion valve 26 , and an evaporator 30 .
- the refrigeration system 10 is used in a commercial setting (e.g., a grocery store) to maintain food product at a suitable refrigerated or freezing temperature.
- a commercial setting e.g., a grocery store
- the refrigeration system 10 may be adapted or configured for use in other applications (e.g., personal refrigerators, air-conditioning systems, oil refineries, chemical plants, metal refineries, etc.) where refrigeration is desired.
- the illustrated compressor 14 is a single compressor operable to compress a vaporous refrigerant. However, the compressor 14 may be replaced by multiple compressors arranged in parallel or in series to compress the refrigerant.
- the compressor(s) 14 may be, for example, a centrifugal compressor, a rotary screw compressor, a reciprocating compressor, or the like. In the illustrated embodiment, the compressor 14 compresses a refrigerant and delivers the compressed refrigerant to the condenser 18 .
- the condenser 18 is positioned downstream of the compressor 14 to receive the vaporous, compressed refrigerant.
- the condenser 18 is an air-cooled condenser that includes a condenser coil 34 and a fan 38 .
- the fan 38 directs and propels air over the condenser coil 34 to remove heat from the refrigerant within the condenser coil 34 .
- the condenser 18 may be a water-cooled condenser. As the condenser 18 removes heat from the vaporous refrigerant, the refrigerant changes into a liquid refrigerant and is delivered to the receiver 22 .
- the receiver 22 is positioned downstream of the condenser 18 to receive the liquid refrigerant from the condenser 18 .
- the receiver 22 is configured to store or retain a supply of liquid refrigerant. As shown in FIG. 1 , a portion of the refrigerant within the receiver may also be vaporous.
- the refrigerant enters the receiver 22 through a top of the receiver 22 and exits the receiver through a bottom to ensure only liquid refrigerant leaves the receiver 22 .
- the expansion valve 26 is positioned downstream of the receiver 22 to receive the liquid refrigerant from the receiver 22 .
- the expansion valve 26 may be any suitable type of throttle valve that abruptly decreases the pressure of the liquid refrigerant. As the liquid refrigerant decreases in pressure, a portion of the refrigerant vaporizes and, thereby, further decreases in temperature. The cool refrigerant exiting the expansion valve 26 is directed toward the evaporator 30 .
- the evaporator 30 is positioned downstream of the expansion valve 26 to receive the cool refrigerant.
- the evaporator 30 includes an evaporator coil 42 and a fan 46 configured to facilitate heat exchange between the refrigerant and a secondary fluid (e.g., air) by directing and propelling the secondary fluid over the evaporator coil 42 .
- the refrigerant warms and evaporates in the evaporator 30 and is circulated back toward the compressor 14 .
- the illustrated refrigeration system 10 also includes a refrigerated display case 50 , or merchandiser, operable to store and display food product at a reduced temperature.
- the display case 50 includes a housing 54 defining a product display area 58 , a door 62 coupled to the housing 54 , and shelves 66 positioned within the product display area 58 to support the food product.
- the illustrated evaporator 30 is located within an air passageway 70 of the housing 54 such that the cool refrigerant in the evaporator coil 42 exchanges heat with air flowing through the display case 50 , thereby maintaining the reduced temperature within the product display area 58 .
- the compressor 14 compresses a gaseous refrigeration and directs the compressed refrigerant to the condenser 18 where the refrigerant is cooled and condensed into a liquid refrigerant.
- the liquid refrigerant may be temporarily stored in the receiver 22 prior to being directed toward the evaporator 30 .
- the liquid refrigerant is pulled from the receiver 22 and forced through the expansion valve 26 to convert the refrigerant into a two-phase fluid.
- the two-phase refrigerant absorbs heat from air being directed through the evaporator 30 by the fan 46 .
- the refrigerant generally leaves the evaporator 30 in a superheated condition and is routed back to the compressor 14 for recycling.
- the cooled air exiting the evaporator 30 is directed through the air passageway and is introduced into the product display area 58 , where it will remove heat from the displayed food product and maintain the food product at the desired temperature.
- the illustrated refrigeration system 10 also includes a plurality of flexible sensors 74 A- 74 P.
- the sensors 74 A- 74 P are shown schematically to illustrate their general position relative to the other components of the refrigeration system 10 .
- Each flexible sensor 74 A- 74 P measures one or more system properties and outputs the measured property to sensing and conditioning electronics 78 ( FIGS. 3 , 4 , 5 , and 6 ) to notify an operator of the current status of the refrigeration system 10 .
- the refrigeration system 10 may include only one or a few of the illustrated sensors 74 A- 74 P, depending on which system properties the operator wishes to monitor.
- the refrigeration system 10 may include sensors located at additional or alternative locations to measure other system properties.
- FIGS. 2A and 2B illustrate two constructions of flexible sensors 82 A, 82 B for use with the refrigeration system 10 shown in FIG. 1 .
- both sensors 82 A, 82 B include generally the same components and function in a generally similar manner, and, thereby, like parts are given the same reference numerals.
- each flexible sensor is a Bend Sensor® provided by Flexpoint Sensor Systems, Inc. of Draper, Utah.
- Each sensor 82 A, 82 B includes a flexible substrate 86 , a conductive material 90 coupled to the substrate 86 , a sleeve 94 positioned around the substrate 86 , and a connection area 98 .
- the substrate 86 is configured to deflect, or bend, when a force is applied to the sensor 82 A, 82 B. In the illustrated embodiment, the substrate 86 repeatably and reliably bends by various degrees proportional to the applied force. Once the force is removed or stopped, the substrate 86 moves back to a substantially straight position, as shown in FIGS. 2A and 2B .
- the conductive material 90 is coupled or applied to the substrate 86 to deflect with the substrate 86 . As the conductive material 90 bends, the resistance of the material 90 changes. Therefore, the sensor 82 A, 82 B will output a different voltage or current based on the degree of deflection of the material 90 .
- the conductive material 90 is only shown coupled to one side of the substrate 86 . However, it should be readily apparent that the material 90 may be coupled in a similar manner to the opposite side of the substrate 86 such that the sensor 82 A, 82 B not only measures the degree of deflection, but also the direction of deflection.
- the material 90 may be a conductive ink printed on the substrate 86 .
- the sleeve 94 surrounds the substrate 86 and the conductive material 90 to protect the flexible sensor 82 A, 82 B.
- the sleeve 94 seals the substrate 86 from the environment to inhibit contaminants (e.g., dust, frost, liquid, etc.) from contacting conductive material 90 .
- the sleeve 94 has bend characteristics that are substantially similar to the flexible substrate 86 .
- connection area 98 facilitates electrically coupling the sensors 82 A, 82 B to the sensing and conditioning electronics 78 .
- the connection area 98 includes a plug 102 to allow quick connecting and disconnecting with the electronics 78 .
- the connection area 98 includes electrical leads 106 to allow the sensor 82 A, 82 B to be spaced further away from the electronics 78 .
- FIG. 3 illustrates the first flexible sensor 82 A in a fluid conduit 110 to measure a liquid flow.
- the flexible sensor 82 A is positioned between first and second large body resistors 114 , 118 and electrically coupled to the sensing and conditioning electronics 78 .
- a low voltage, low current DC voltage is applied to the resistors 114 , 118 to warm the resistors 114 , 118 and, thereby, heat the sensor 82 A.
- Such heating keeps the sensor 82 A from adhering, or freezing, to the resistors 114 , 118 or the conduit 110 .
- the sensor 82 A deflects and outputs a signal to the electronics 78 indicative of the direction of flow, the speed of the flow, and/or the rate of change of the flow over time. Additionally, the signal may be used to calculate the volume of liquid flow.
- a liquid e.g., refrigerant, oil, etc.
- the flexible sensor 82 A may be used to monitor refrigerant flow in the refrigeration system 10 .
- the sensor 82 A may be positioned within any conduit, or line, of the refrigeration system 10 shown in FIG. 1 to monitor the speed and/or volume of refrigerant flowing through the conduit.
- the senor 82 A may be positioned downstream of the expansion valve 26 to monitor the status of the valve 26 .
- the sensor 82 A is positioned generally at the location of the sensor 74 A in FIG. 1 .
- the sensor 82 A can determine if the valve 26 fails to open, fails to close, or improperly throttles the refrigerant exiting the valve 26 .
- the electronics 78 may then trigger an alarm or warning to notify an operator of this valve failure.
- the alarm may be a displayed warning message, an audible noise, a flashing light, an email notification, a voice message, a pager alert, or the like.
- the flexible sensor 82 A can use the measured refrigerant flow to determine a position of the expansion valve 26 (e.g., opened, closed, or an intermediate position) and output the position information to the operator with the electronics 78 .
- the senor 82 A may be positioned downstream of the compressor 14 to monitor the status of the compressor 14 .
- the sensor 82 A is positioned generally at the location of the sensor 74 B in FIG. 1 . Based on the measured refrigerant flow output by the compressor 14 , the sensor 82 A and the electronics 78 can determine a run time of the compressor 14 and output the run time to an operator.
- the senor 82 A may be positioned within the compressor 14 to monitor an oil flow inside the compressor 14 .
- the sensor 82 A is positioned generally at the location of the sensor 74 C in FIG. 1 . Based on the oil flow measured by the sensor 82 A, the electronics 78 can notify an operator if the compressor 14 is running low on oil or if too much oil has been added to the compressor 14 .
- FIG. 4 illustrates the first flexible sensor 82 A in an air passageway 122 to measure an air flow. Similar to the construction described above with reference to FIG. 3 , the sensor 82 A is positioned between the two large body resistors 114 , 118 and electrically coupled to the sensing and conditioning electronics 78 . As air flows over and past the flexible sensor 82 A, the sensor 82 A deflects and outputs a signal to the electronics 78 indicative of the direction of flow, the speed of the flow, and/or the rate of change of the flow over time. Additionally, the signal may be used to calculate the volume of air flow.
- the flexible sensor 82 A is used to measure an off coil air velocity at the evaporator 30 .
- the sensor 82 A is positioned generally at the location of the sensor 74 D in FIG. 1 .
- water vapor in the air may condense and freeze on the surface of the evaporator coil 42 in certain ambient conditions, creating a frost build-up.
- Significant frost build-up reduces the evaporator coil performance by reducing the air flow through the coil 42 .
- the electronics 78 can then trigger or initiate a demand defrost to remove the frost from the evaporator coil. In some embodiments, the electronics 78 can trigger an alarm or warning to notify an operator to initiate the demand defrost. In other embodiments, the electronics 78 may initiate the demand defrost automatically.
- the flexible sensor 82 A is used to determine a fan failure.
- the sensor 82 A is positioned generally at the location of sensor 74 E or sensor 74 F in FIG. 1 to monitor the condenser fan 38 or the evaporator fan 46 , respectively.
- the sensors 82 A are deflected by the air flow.
- the electronics 78 may then trigger an alarm or warning to notify an operator of this failure.
- the flexible sensor 82 A is used to determine if an air return grille 126 of the display case 50 is blocked.
- the sensor 82 A is positioned generally at the location of the sensor 74 G in FIG. 1 .
- the sensor 82 A is deflected and outputs a corresponding signal to the electronics 78 . If the grille 126 becomes blocked by foreign material, air will no longer flow through the grille 126 and deflect the sensor 82 A, changing the signal output to the electronics 78 .
- the electronics 78 may then trigger an alarm or warning to notify an operator of the blockage.
- the flexible sensor 82 A is used to determine if the condenser 18 is blocked.
- the sensor 82 A is positioned generally at the location of the sensor 74 H in FIG. 1 .
- the sensor 82 A is slightly upstream of the condenser fan 38 to monitor when the condenser fan 38 pulls ambient air through the condenser 18 .
- the sensor 82 A is deflected and outputs a corresponding signal to the electronics 78 .
- the condenser 18 becomes blocked (e.g., a grille covering the fan 38 becomes blocked)
- the fan 38 will no longer pull air and the sensor 82 A will no longer be deflected, changing the signal output to the electronics 78 .
- the electronics 78 may then trigger an alarm or warning to notify an operator of the blockage.
- FIG. 5 illustrates the first flexible sensor 82 A configured to measure a fluid level.
- the flexible sensor 82 A is positioned adjacent to only one large body resistor 114 ; however, in other embodiments, the sensor 82 A may be positioned between two resistors. Similar to the construction described above with reference to FIG. 3 , the flexible sensor 82 A is electrically coupled to the sensing and conditioning electronics 78 .
- a float 130 is coupled to an end of the sensor 82 A opposite from a support 134 , or wall.
- the sensor 82 A may start at the substantially straight position (shown as a solid line) and move to a bent position (shown in phantom lines) to measure an increase in the fluid level.
- the sensor 82 A may start at a bent position and move to the substantially straight position to measure a decrease in the fluid level.
- the flexible sensor 82 A may be used to measure when the fluid level is greater than or less than a desired, or acceptable, level.
- the flexible sensor 82 A is used to measure a refrigerant level (e.g., a refrigerant charge) within the receiver 22 .
- a refrigerant level e.g., a refrigerant charge
- the sensor 82 A is positioned generally at the location of the sensor 741 in FIG. 1 .
- the sensor 82 A is coupled to a wall of the receiver 22 and extends inwardly in the substantially straight position, corresponding to an acceptable refrigerant level. If the refrigerant level rises, the sensor 82 A is deflected upwardly due to the float 130 rising with the refrigerant, changing the signal output by the sensor 82 A (e.g., to a positive voltage) to the electronics 78 .
- the sensor 82 A deflects downwardly due to gravity, changing the signal output by the sensor 82 A (e.g., to a negative voltage) to the electronics 78 .
- the electronics 78 may then trigger an alarm or warning to notify an operator of the changed refrigerant level.
- the flexible sensor 82 A is described starting at the substantially straight position, it should be readily apparent to one skilled in the art that the sensor 82 A may start at a bent position, either upwardly or downwardly, that corresponds to the acceptable refrigerant level.
- the flexible sensor 82 A is used to determine if a drain 138 of the display case 50 is clogged or blocked.
- the sensor 82 A is positioned generally at the location of the sensor 74 J in FIG. 1 .
- the drain 138 is positioned in a lower portion 142 of the housing 54 such that liquid that accumulates in the product display area 58 (e.g., melted frost, spilled liquid food product, etc.) is automatically drained from the display case 50 .
- the sensor 82 A is positioned directly adjacent to the lower portion 142 of the housing 54 .
- the drain 138 becomes blocked or clogged, liquid will no longer drain from the display case 50 and will begin to accumulate on the lower portion 142 of the housing 54 . As the liquid accumulates, the sensor 82 A deflects upwardly, changing the signal output to the electronics 78 . The electronics 78 may then trigger an alarm or warning to notify an operator to check the drain 138 .
- the sensor 82 A measures an oil level within the compressor 14 .
- the sensor 82 A is positioned generally at the location of the sensor 74 C in FIG. 1 . Due to turbulence within the compressor 14 (e.g., oil turbulence), it may be less desirable to use a float arrangement to measure the oil level in the compressor 14 .
- the sensor 82 A is coupled to a gear driven piece of the compressor 14 , such as a shaft, that rotates based on the oil level within the compressor 14 . As the oil level rises, the shaft rotates in a first direction so that the sensor 82 A wraps around the shaft.
- the resistance of the sensor 82 A, and thereby the signal output to the sensing and conditioning electronics 78 increases as the sensor 82 A wraps around the shaft. As the oil level falls, the shaft rotates in a reverse direction so that the sensor 82 A unwraps from the shaft. The resistance of the sensor 82 A, and thereby the signal output to the electronics 78 , decreases as the sensor 82 A unwraps from the shaft. Based on the signal output by the sensor 82 A, the electronics 78 may notify an operator of the current oil level or trigger an alarm or warning if the oil level rises above or falls below an acceptable level.
- FIG. 6 illustrates the second flexible sensor 82 B configured to measure an applied force or to monitor movement of a secondary structure 146 .
- the flexible sensor 82 B is disposed within an elastic material 150 and coupled to the secondary structure 146 (e.g., a hinge, a shelf, a switch, or the like) such that any movement of the secondary structure 146 is transferred to the sensor 82 B.
- the sensor 82 B deflects a proportionate amount. Similar to the construction discussed above with reference to FIG. 3 , the sensor 82 B is electrically coupled to the sensing and conditioning electronics 78 .
- the secondary structure 146 is a hinge that couples the door 62 to the housing 54 of the display case 50 .
- the flexible sensor 82 B is coupled to the hinge such that one end of the sensor 82 Bis securely fastened to a first half of the hinge, and another end of the sensor 82 B is securely fastened to a second half of the hinge.
- the sensor 82 B is positioned generally at the location of the sensor 74 K in FIG. 1 .
- the hinge is substantially straight such that the sensor 82 B is likewise substantially straight.
- the first half of the hinge rotates relative to the second half, deflecting the sensor 82 B and changing the signal output to the electronics 78 .
- the electronics 78 can trigger an alarm or warning to notify an operator to check the door 62 .
- the secondary structure 146 is one of the shelves 66 within the product display area 58 of the display case 50 .
- the sensor 82 B is positioned generally at the location of the sensors 74 L in FIG. 1 .
- the flexible sensor 82 B is used to monitor a load condition (e.g., a weight of food product) on the shelf 66 , rather than having to constantly visually monitor the shelf 66 .
- a load condition e.g., a weight of food product
- the shelf 66 deflects less and less until the shelf 66 , and thereby the sensor 82 B, substantially straightens.
- the sensor 82 B outputs a different signal to the electronics 78 .
- the electronics 78 can then trigger an alarm or warning to notify an operator to check and restock the shelf 66 , if necessary.
- the secondary structure 146 is a switch of a circuit breaker 154 for the product display case 50 .
- the sensor 82 B is positioned generally at the location of the sensor 74 M in FIG. 1 .
- the illustrated circuit breaker 154 is electrically coupled to the evaporator 30 to provide power to the evaporator fan 46 .
- the circuit breaker 154 may be electrically coupled to other components of the refrigeration system 10 and/or the display case 50 (e.g., lights, fans, etc.).
- the flexible sensor 82 B is coupled to one of the switches of the circuit breaker 154 such that an operator is given instant notification if one of the circuits becomes tripped.
- the switch when the circuit is closed, the switch is flipped to one side, bending the sensor 82 B to output a positive voltage.
- the switch When the circuit is opened, the switch is flipped to the other side, bending the sensor 82 B to output a negative voltage.
- the change in voltages from positive to negative (or vise versa) is output to the electronics 78 , which triggers an alarm or warning to notify the operator of the tripped circuit.
- the secondary structure 146 is a contactor. As shown in FIG. 1 , a first contactor 158 is electrically coupled to the compressor 14 to provide power to the compressor 14 and a second contactor 162 is electrically coupled to the condenser 18 to provide power to the condenser fan 38 .
- the sensor 82 B is positioned generally at the location of the sensor 74 N and/or the sensor 74 P in FIG. 1 . As such, the sensor 82 B is coupled to a switch of each contactor 158 , 162 to monitor the position of the switch in a similar manner to the circuit breaker 154 described above. The sensor 82 B provides information to an operator regarding a status of the contactors 158 , 162 .
- the sensor 82 B can monitor when the switches move to a position where the contactors 158 , 162 are providing power to the compressor 14 and condenser 18 , respectively, so the operator knows if the compressor 14 and the condenser 18 should be running.
- FIG. 7 illustrates another refrigeration system 200 according to an embodiment of the invention.
- the refrigeration system 200 includes a first refrigeration unit 210 and a second refrigeration unit 212 .
- the first refrigeration unit 210 or primary refrigeration loop, includes compressors 214 , a condenser 218 , a receiver 222 , an expansion valve 226 , and an evaporator 230 .
- three compressors 214 are arranged in parallel; however, it should be readily apparent that fewer or more compressors may be included, or the compressors 214 may be arranged in series.
- the first refrigeration unit 210 circulates a first, or primary, refrigerant that is in a heat exchange relationship with a second refrigerant of the second refrigeration unit 212 at the evaporator 230 .
- the illustrated second refrigeration unit 212 includes the evaporator 230 , a pump 234 , and three display cases 250 .
- the pump 234 may be any positive displacement pump, centrifugal pump, or the like suitable to move and circulate the second refrigerant.
- the illustrated pump 234 generates a driving force to draw the second refrigerant from the evaporator 230 and direct the second refrigerant toward and through the display cases 250 .
- the display cases 250 may be similar to the display case 50 discussed above with reference to FIG. 1 .
- the second refrigeration unit 212 includes three display cases 250 arranged in parallel. However, in other embodiments, the second refrigeration unit 212 may include fewer or more display cases 250 depending on the capacity of the refrigeration system 200 .
- Each display case 250 includes an evaporator or heat exchanger configured to receive the second refrigerant in a liquid or liquid/vapor state and facilitate heat exchange between the second refrigerant and air within the display case 250 .
- the display cases 250 thereby maintain a temperature suitable for refrigerating or freezing food product within the cases 250 .
- the second refrigerant is circulated through the second refrigeration unit 212 by the pump 234 .
- a compressor upstream of the evaporator 230 compresses and circulates the second refrigerant.
- the second refrigerant comes into a heat exchange relationship with the first refrigerant in the first refrigeration unit 210 to remove heat from the second refrigerant.
- the second refrigerant is then drawn through the pump 234 and directed toward the display cases 250 .
- the second refrigerant exchanges heat with the air in the display cases 250 to remove heat from the air.
- the second refrigerant is directed back toward the evaporator 230 to once again remove heat from the second refrigerant with the first refrigerant.
- the refrigeration system 200 also includes a flexible sensor 274 positioned in the second refrigeration unit 212 .
- a flexible sensor 274 positioned in the second refrigeration unit 212 .
- the flexible sensor 274 is similar to the flexible sensor 82 A discussed above with reference to FIG. 2A , and measures a property of the second refrigeration unit 212 .
- the illustrated sensor 274 is positioned to measure a fluid flow (e.g., a refrigerant flow) downstream of the pump 234 .
- the senor 274 can determine if the pump 234 is functioning properly. If necessary, the sensor 274 can trigger an alarm or warning to notify an operator that the pump 234 (or other portion of the second refrigeration unit 212 ) needs maintenance.
- FIG. 8 illustrates an evaporative cooler 300 according to an embodiment of the invention.
- the evaporative cooler 300 or swamp cooler, can be used as a stand-alone cooling system or in combination with either of the refrigeration systems 10 , 200 discussed above to provide additional or supplemental cooling.
- the illustrated evaporative cooler 300 includes a housing 304 , a blower 308 positioned within the housing 304 , evaporator pads 312 , and a pump 316 .
- the housing 304 is configured to surround, protect, and support the other components of the evaporative cooler 300 .
- the housing 304 includes vents 320 to facilitate air flow into the evaporative cooler 300 and is configured to retain a supply of water 324 .
- the housing 304 also includes a duct 328 configured to direct a cool air flow out of the evaporative cooler 300 and toward the desired location.
- the duct 328 may direct the cool air flow into a secondary heat exchanger (e.g., an evaporator) such that the cool air flow does not come into direct contact with the environment being cooled.
- a secondary heat exchanger e.g., an evaporator
- the illustrated blower 308 includes a fan 332 (e.g., a centrifugal fan) and a motor 336 coupled to the fan 332 to drive the fan 332 .
- a fan 332 e.g., a centrifugal fan
- the motor 336 may be positioned outside of the housing 204 to allow easier access to the motor 226 .
- the fan 223 draws the air flow into the evaporative cooler 300 through the vents 320 and directs the cool air flow out through the duct 328 .
- the evaporator pads 312 are positioned within the housing 304 adjacent to the vents 320 .
- the evaporator pads 312 may be composed of, for example, excelsior, melamin paper, or plastic.
- the evaporator pads 312 are configured to temporarily retain water to cool the air flow. As the air flow passes through the pads 312 , heat in the air flow evaporates the water in the pads 312 , cooling the air flow. The cool air flow then flows through the duct 328 to the desired location. As shown in FIG. 8 , the cool air flow may pass over the water supply 324 in the housing 304 to further cool and humidify the air flow prior to entering the duct 328 .
- the pump 316 is positioned within the housing 304 and is in communication with the water supply 324 .
- the pump 316 supplies water to the evaporator pads 312 to remoisten the pads 312 when the air flow evaporators the water on the pads 312 .
- a water distribution line 340 is coupled to the pump 316 to direct water from the pump 316 onto the pads 312 .
- the illustrated distribution line 340 includes two outlets 344 configured to evenly spray the water over the evaporator pads 312 .
- the pump 316 draws water from the water supply 324 and directs the water through the distribution line 340 .
- the water is ejected from the distribution line 340 at the outlets 344 and sprayed onto the evaporator pads 312 to reapply water to the pads 312 such that the air flow through the pads 312 is continuously cooled.
- the evaporative cooler 300 also includes three flexible sensors 374 A, 374 B, 374 C.
- the flexible sensors 374 A, 374 B, 374 C are similar to the sensor 82 A discussed above with reference to FIG. 2A and are used to measure properties of the evaporative cooler 300 .
- the first sensor 374 A is positioned adjacent to the water supply 324 to measure the water level within the housing 304 .
- the first sensor 374 A may be configured similar to the construction shown in FIG. 5 . That is, the first sensor 374 A may include a float and bend upwardly to notify an operator that the water level is becoming too high, or bend downwardly to notify the operator that the water level is becoming too low. Similar to the previous constructions, the sensor 374 A is coupled to sensing and conditioning electronics that trigger an alarm or warning to notify the operator of either change in the water level.
- the second sensor 374 B and the third sensor 374 C are positioned adjacent to the outlets 344 of the water distribution lines 340 .
- the sensors 374 B, 374 C are substantially straight.
- the sensors 374 B, 374 C are deflected by the sprayed water. Deflecting the sensors 374 B, 374 C changes the resistance of the conductive material 90 and, thereby, the signal output by the sensors 374 B, 374 C to the sensing and conditioning electronics.
- the electronics then notify an operator that the evaporative cooler 300 is in operation and functioning properly. If one the sensors 374 B, 374 C is not deflected during operation of the evaporative cooler 300 , the electronics can notify the operator to check the corresponding distribution line 340 for a clog or rupture.
- the sensors provide a reliable means to measure various properties of refrigeration systems.
- the sensors are impervious to the operating environment of a commercial refrigeration system.
- the sensors are not affected by dust, moisture, low operating temperatures of refrigerant, or varying temperatures of an air flow.
- the sensor can withstand in excess of thirty million cycles, but are still relatively cost effective.
- the flexible sensors include no moving parts or active electronic devices that may need servicing or replacement over time.
Abstract
A refrigeration system including a compressor configured to compress a refrigerant, a condenser in fluid communication with the compressor and configured to remove heat from the refrigerant, and an expansion valve in fluid communication with the condenser and configured to decrease a pressure of the refrigerant. The refrigeration system also includes an evaporator in fluid communication with the expansion valve and configured to facilitate heat exchange between the refrigerant and another fluid, and a sensor configured to bend to measure a property of the refrigeration system. The sensor including a flexible substrate and a conductive material applied to the flexible substrate and having a resistance that changes in response to bending of the flexible substrate to generate a signal indicative of the property.
Description
- The present invention relates to refrigeration systems and, particularly, to refrigeration systems that include sensors to measure properties of the refrigeration systems.
- Refrigeration systems are commonly used in a variety of industrial and commercial applications to provide refrigeration to particular portions or processes of the applications. For example, commercial refrigeration systems are typically used to cool or freeze food product to permit longer storage of the food product. In some applications, it may be desirable to measure one or more properties of the refrigeration systems (e.g., air flow, refrigerant flow, fluid level, etc.) to monitor the status of the systems.
- Presently, some air flow sensors exist that are relatively inexpensive, commercially available, and easily interfaced with control systems. For example, hot wire mass air flow (MAF) sensors, vane air flow (VAF) meters, and Karman vortex air flow meters are used to measure air flow properties. However, such sensors are commonly rendered non-functional in the presence of contaminants (e.g., dust, frost, liquid, etc.), making them less desirable for use in refrigeration systems. In addition, the unit cost of such sensors, while being acceptable for industrial and automotive markets, is typically cost prohibitive for commercial refrigeration systems. Furthermore, depending on the application, the life cycle of these sensors may be less than desirable.
- In one embodiment, the invention provides a refrigeration system including a compressor configured to compress a refrigerant, a condenser in fluid communication with the compressor and configured to remove heat from the refrigerant, and an expansion valve in fluid communication with the condenser and configured to decrease a pressure of the refrigerant. The refrigeration system also includes an evaporator in fluid communication with the expansion valve and configured to facilitate heat exchange between the refrigerant and another fluid, and a sensor configured to bend to measure a property of the refrigeration system. The sensor includes a flexible substrate and a conductive material applied to the flexible substrate. The conductive material has a resistance that changes in response to bending of the flexible substrate to generate a signal indicative of the property.
- In another embodiment, the invention provides a method of measuring a property of a refrigeration system. The refrigeration system includes a compressor, a condenser in fluid communication with the compressor, an expansion valve in fluid communication with the condenser, and an evaporator in fluid communication with the expansion valve. The method includes providing a sensor including a flexible substrate and a conductive material applied to the flexible substrate. The conductive material has a resistance that changes in response to bending of the flexible substrate. The method also includes compressing a refrigerant with the compressor, removing heat from the refrigerant with the condenser, decreasing a pressure of the refrigerant with the expansion valve, exchanging heat between the refrigerant and another fluid with the evaporator, and bending the sensor to generate a signal indicative of a property of the refrigeration system.
- In yet another embodiment, the invention provides an evaporative cooler including a housing having a least one vent and configured to contain water, a blower positioned within the housing and configured to draw air through the at least one vent, and an evaporator pad positioned adjacent to the at least one vent. The evaporative cooler also includes a pump configured to spray at least a portion of the evaporator pad with the water and a sensor configured to bend to measure a property of the evaporative cooler. The sensor includes a flexible substrate and a conductive material applied to the flexible substrate and having a resistance that changes in response to bending of the flexible substrate to generate a signal indicative of the property.
- Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings.
-
FIG. 1 is a schematic of a refrigeration system according to an embodiment of the invention. -
FIG. 2A is planar view of a flexible sensor for use with the refrigeration system shown inFIG. 1 . -
FIG. 2B is a planar view of another flexible sensor for use with the refrigeration system shown inFIG. 1 . -
FIG. 3 is a schematic of a flexible sensor configured to measure a liquid flow. -
FIG. 4 is a schematic of a flexible sensor configured to measure an air flow. -
FIG. 5 is a schematic of a flexible sensor configured to measure a fluid level. -
FIG. 6 is a schematic of a flexible sensor configured to measure a load on a secondary structure. -
FIG. 7 is a schematic of another refrigeration system according to an embodiment of the present invention. -
FIG. 8 is a cross-sectional view of an evaporative cooler according to an embodiment of the present invention. - Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein are for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings.
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FIG. 1 illustrates arefrigeration system 10 including acompressor 14, acondenser 18, areceiver 22, anexpansion valve 26, and anevaporator 30. In the illustrated embodiment, therefrigeration system 10 is used in a commercial setting (e.g., a grocery store) to maintain food product at a suitable refrigerated or freezing temperature. However, it should be readily apparent to one skilled in the art that therefrigeration system 10 may be adapted or configured for use in other applications (e.g., personal refrigerators, air-conditioning systems, oil refineries, chemical plants, metal refineries, etc.) where refrigeration is desired. - The illustrated
compressor 14 is a single compressor operable to compress a vaporous refrigerant. However, thecompressor 14 may be replaced by multiple compressors arranged in parallel or in series to compress the refrigerant. The compressor(s) 14 may be, for example, a centrifugal compressor, a rotary screw compressor, a reciprocating compressor, or the like. In the illustrated embodiment, thecompressor 14 compresses a refrigerant and delivers the compressed refrigerant to thecondenser 18. - The
condenser 18 is positioned downstream of thecompressor 14 to receive the vaporous, compressed refrigerant. In the illustrated embodiment, thecondenser 18 is an air-cooled condenser that includes acondenser coil 34 and afan 38. Thefan 38 directs and propels air over thecondenser coil 34 to remove heat from the refrigerant within thecondenser coil 34. In other embodiments, thecondenser 18 may be a water-cooled condenser. As thecondenser 18 removes heat from the vaporous refrigerant, the refrigerant changes into a liquid refrigerant and is delivered to thereceiver 22. - The
receiver 22 is positioned downstream of thecondenser 18 to receive the liquid refrigerant from thecondenser 18. Thereceiver 22 is configured to store or retain a supply of liquid refrigerant. As shown inFIG. 1 , a portion of the refrigerant within the receiver may also be vaporous. The refrigerant enters thereceiver 22 through a top of thereceiver 22 and exits the receiver through a bottom to ensure only liquid refrigerant leaves thereceiver 22. - The
expansion valve 26 is positioned downstream of thereceiver 22 to receive the liquid refrigerant from thereceiver 22. Theexpansion valve 26 may be any suitable type of throttle valve that abruptly decreases the pressure of the liquid refrigerant. As the liquid refrigerant decreases in pressure, a portion of the refrigerant vaporizes and, thereby, further decreases in temperature. The cool refrigerant exiting theexpansion valve 26 is directed toward theevaporator 30. - The
evaporator 30 is positioned downstream of theexpansion valve 26 to receive the cool refrigerant. Theevaporator 30 includes anevaporator coil 42 and afan 46 configured to facilitate heat exchange between the refrigerant and a secondary fluid (e.g., air) by directing and propelling the secondary fluid over theevaporator coil 42. The refrigerant warms and evaporates in theevaporator 30 and is circulated back toward thecompressor 14. - The illustrated
refrigeration system 10 also includes arefrigerated display case 50, or merchandiser, operable to store and display food product at a reduced temperature. In the illustrated embodiment, thedisplay case 50 includes ahousing 54 defining aproduct display area 58, adoor 62 coupled to thehousing 54, andshelves 66 positioned within theproduct display area 58 to support the food product. The illustratedevaporator 30 is located within anair passageway 70 of thehousing 54 such that the cool refrigerant in theevaporator coil 42 exchanges heat with air flowing through thedisplay case 50, thereby maintaining the reduced temperature within theproduct display area 58. - In operation, the
compressor 14 compresses a gaseous refrigeration and directs the compressed refrigerant to thecondenser 18 where the refrigerant is cooled and condensed into a liquid refrigerant. In some embodiments, such as the illustrated embodiment, the liquid refrigerant may be temporarily stored in thereceiver 22 prior to being directed toward theevaporator 30. The liquid refrigerant is pulled from thereceiver 22 and forced through theexpansion valve 26 to convert the refrigerant into a two-phase fluid. The two-phase refrigerant absorbs heat from air being directed through theevaporator 30 by thefan 46. The refrigerant generally leaves theevaporator 30 in a superheated condition and is routed back to thecompressor 14 for recycling. The cooled air exiting theevaporator 30 is directed through the air passageway and is introduced into theproduct display area 58, where it will remove heat from the displayed food product and maintain the food product at the desired temperature. - As shown in
FIG. 1 , the illustratedrefrigeration system 10 also includes a plurality offlexible sensors 74A-74P. Thesensors 74A-74P are shown schematically to illustrate their general position relative to the other components of therefrigeration system 10. Eachflexible sensor 74A-74P measures one or more system properties and outputs the measured property to sensing and conditioning electronics 78 (FIGS. 3 , 4, 5, and 6) to notify an operator of the current status of therefrigeration system 10. In some embodiments, therefrigeration system 10 may include only one or a few of the illustratedsensors 74A-74P, depending on which system properties the operator wishes to monitor. In other embodiments, therefrigeration system 10 may include sensors located at additional or alternative locations to measure other system properties. -
FIGS. 2A and 2B illustrate two constructions offlexible sensors refrigeration system 10 shown inFIG. 1 . In the illustrated embodiment, bothsensors - Each
sensor flexible substrate 86, aconductive material 90 coupled to thesubstrate 86, asleeve 94 positioned around thesubstrate 86, and aconnection area 98. Thesubstrate 86 is configured to deflect, or bend, when a force is applied to thesensor substrate 86 repeatably and reliably bends by various degrees proportional to the applied force. Once the force is removed or stopped, thesubstrate 86 moves back to a substantially straight position, as shown inFIGS. 2A and 2B . - The
conductive material 90 is coupled or applied to thesubstrate 86 to deflect with thesubstrate 86. As theconductive material 90 bends, the resistance of the material 90 changes. Therefore, thesensor material 90. In the illustrated embodiment, theconductive material 90 is only shown coupled to one side of thesubstrate 86. However, it should be readily apparent that thematerial 90 may be coupled in a similar manner to the opposite side of thesubstrate 86 such that thesensor flexible sensor sensor flexible sensor sensor material 90 may be a conductive ink printed on thesubstrate 86. - The
sleeve 94, or sheath, surrounds thesubstrate 86 and theconductive material 90 to protect theflexible sensor sleeve 94 seals thesubstrate 86 from the environment to inhibit contaminants (e.g., dust, frost, liquid, etc.) from contactingconductive material 90. In some embodiments, thesleeve 94 has bend characteristics that are substantially similar to theflexible substrate 86. - The
connection area 98 facilitates electrically coupling thesensors conditioning electronics 78. Referring to the construction shown inFIG. 2A , theconnection area 98 includes aplug 102 to allow quick connecting and disconnecting with theelectronics 78. Referring to the construction shown inFIG. 2B , theconnection area 98 includeselectrical leads 106 to allow thesensor electronics 78. -
FIG. 3 illustrates the firstflexible sensor 82A in afluid conduit 110 to measure a liquid flow. In the illustrated embodiment, theflexible sensor 82A is positioned between first and secondlarge body resistors conditioning electronics 78. A low voltage, low current DC voltage is applied to theresistors resistors sensor 82A. Such heating keeps thesensor 82A from adhering, or freezing, to theresistors conduit 110. As a liquid (e.g., refrigerant, oil, etc.) flows over and past theflexible sensor 82A, thesensor 82A deflects and outputs a signal to theelectronics 78 indicative of the direction of flow, the speed of the flow, and/or the rate of change of the flow over time. Additionally, the signal may be used to calculate the volume of liquid flow. - For example, in one construction, the
flexible sensor 82A may be used to monitor refrigerant flow in therefrigeration system 10. In such a construction, thesensor 82A may be positioned within any conduit, or line, of therefrigeration system 10 shown inFIG. 1 to monitor the speed and/or volume of refrigerant flowing through the conduit. - In another construction, the
sensor 82A may be positioned downstream of theexpansion valve 26 to monitor the status of thevalve 26. In such a construction, thesensor 82A is positioned generally at the location of thesensor 74A inFIG. 1 . Based on the measured speed or volume of the refrigerant, thesensor 82A can determine if thevalve 26 fails to open, fails to close, or improperly throttles the refrigerant exiting thevalve 26. Theelectronics 78 may then trigger an alarm or warning to notify an operator of this valve failure. For example, in some embodiments, the alarm may be a displayed warning message, an audible noise, a flashing light, an email notification, a voice message, a pager alert, or the like. In addition, theflexible sensor 82A can use the measured refrigerant flow to determine a position of the expansion valve 26 (e.g., opened, closed, or an intermediate position) and output the position information to the operator with theelectronics 78. - In yet another construction, the
sensor 82A may be positioned downstream of thecompressor 14 to monitor the status of thecompressor 14. In such a construction, thesensor 82A is positioned generally at the location of thesensor 74B inFIG. 1 . Based on the measured refrigerant flow output by thecompressor 14, thesensor 82A and theelectronics 78 can determine a run time of thecompressor 14 and output the run time to an operator. - In a further construction, the
sensor 82A may be positioned within thecompressor 14 to monitor an oil flow inside thecompressor 14. In such a construction, thesensor 82A is positioned generally at the location of thesensor 74C inFIG. 1 . Based on the oil flow measured by thesensor 82A, theelectronics 78 can notify an operator if thecompressor 14 is running low on oil or if too much oil has been added to thecompressor 14. -
FIG. 4 illustrates the firstflexible sensor 82A in anair passageway 122 to measure an air flow. Similar to the construction described above with reference toFIG. 3 , thesensor 82A is positioned between the twolarge body resistors conditioning electronics 78. As air flows over and past theflexible sensor 82A, thesensor 82A deflects and outputs a signal to theelectronics 78 indicative of the direction of flow, the speed of the flow, and/or the rate of change of the flow over time. Additionally, the signal may be used to calculate the volume of air flow. - In one construction, the
flexible sensor 82A is used to measure an off coil air velocity at theevaporator 30. In such a construction, thesensor 82A is positioned generally at the location of thesensor 74D inFIG. 1 . When theevaporator 30 is operating properly, air flows past theevaporator coil 42 and deflects thesensor 82A. However, over time water vapor in the air may condense and freeze on the surface of theevaporator coil 42 in certain ambient conditions, creating a frost build-up. Significant frost build-up reduces the evaporator coil performance by reducing the air flow through thecoil 42. When the air flow through thecoil 42 is reduced, thesensor 82A is no longer deflected (or not deflected as much), changing the signal output to theelectronics 78. Theelectronics 78 can then trigger or initiate a demand defrost to remove the frost from the evaporator coil. In some embodiments, theelectronics 78 can trigger an alarm or warning to notify an operator to initiate the demand defrost. In other embodiments, theelectronics 78 may initiate the demand defrost automatically. - In another construction, the
flexible sensor 82A is used to determine a fan failure. In such a construction, thesensor 82A is positioned generally at the location ofsensor 74E orsensor 74F inFIG. 1 to monitor thecondenser fan 38 or theevaporator fan 46, respectively. When thefans respective coils 34, 42), thesensors 82A are deflected by the air flow. However, if eitherfan sensor 82A will no longer be deflected, changing the signal output to theelectronics 78. Theelectronics 78 may then trigger an alarm or warning to notify an operator of this failure. - In yet another construction, the
flexible sensor 82A is used to determine if anair return grille 126 of thedisplay case 50 is blocked. In such a construction, thesensor 82A is positioned generally at the location of thesensor 74G inFIG. 1 . During normal operation, air flows from theevaporator 30, through theair passageway 70, through theproduct display area 58, and back to theair passageway 70 through theair return grille 126. As the air flows through thegrille 126, thesensor 82A is deflected and outputs a corresponding signal to theelectronics 78. If thegrille 126 becomes blocked by foreign material, air will no longer flow through thegrille 126 and deflect thesensor 82A, changing the signal output to theelectronics 78. Theelectronics 78 may then trigger an alarm or warning to notify an operator of the blockage. - In a similar construction, the
flexible sensor 82A is used to determine if thecondenser 18 is blocked. In such a construction, thesensor 82A is positioned generally at the location of thesensor 74H inFIG. 1 . Thesensor 82A is slightly upstream of thecondenser fan 38 to monitor when thecondenser fan 38 pulls ambient air through thecondenser 18. As air is pulled through thecondenser 18 by thefan 38, thesensor 82A is deflected and outputs a corresponding signal to theelectronics 78. If thecondenser 18 becomes blocked (e.g., a grille covering thefan 38 becomes blocked), thefan 38 will no longer pull air and thesensor 82A will no longer be deflected, changing the signal output to theelectronics 78. Theelectronics 78 may then trigger an alarm or warning to notify an operator of the blockage. -
FIG. 5 illustrates the firstflexible sensor 82A configured to measure a fluid level. In the illustrated embodiment, theflexible sensor 82A is positioned adjacent to only onelarge body resistor 114; however, in other embodiments, thesensor 82A may be positioned between two resistors. Similar to the construction described above with reference toFIG. 3 , theflexible sensor 82A is electrically coupled to the sensing andconditioning electronics 78. - As shown in
FIG. 5 , afloat 130 is coupled to an end of thesensor 82A opposite from asupport 134, or wall. When the fluid level rises and contacts thefloat 130, thefloat 130 rises and deflects thesensor 82A. In some configurations, thesensor 82A may start at the substantially straight position (shown as a solid line) and move to a bent position (shown in phantom lines) to measure an increase in the fluid level. In other configurations, thesensor 82A may start at a bent position and move to the substantially straight position to measure a decrease in the fluid level. As such, theflexible sensor 82A may be used to measure when the fluid level is greater than or less than a desired, or acceptable, level. - In one construction, the
flexible sensor 82A is used to measure a refrigerant level (e.g., a refrigerant charge) within thereceiver 22. In such a construction, thesensor 82A is positioned generally at the location of thesensor 741 inFIG. 1 . Thesensor 82A is coupled to a wall of thereceiver 22 and extends inwardly in the substantially straight position, corresponding to an acceptable refrigerant level. If the refrigerant level rises, thesensor 82A is deflected upwardly due to thefloat 130 rising with the refrigerant, changing the signal output by thesensor 82A (e.g., to a positive voltage) to theelectronics 78. If the refrigerant level falls, thesensor 82A deflects downwardly due to gravity, changing the signal output by thesensor 82A (e.g., to a negative voltage) to theelectronics 78. Theelectronics 78 may then trigger an alarm or warning to notify an operator of the changed refrigerant level. Although theflexible sensor 82A is described starting at the substantially straight position, it should be readily apparent to one skilled in the art that thesensor 82A may start at a bent position, either upwardly or downwardly, that corresponds to the acceptable refrigerant level. - In another construction, the
flexible sensor 82A is used to determine if adrain 138 of thedisplay case 50 is clogged or blocked. In such a construction, thesensor 82A is positioned generally at the location of thesensor 74J inFIG. 1 . Thedrain 138 is positioned in alower portion 142 of thehousing 54 such that liquid that accumulates in the product display area 58 (e.g., melted frost, spilled liquid food product, etc.) is automatically drained from thedisplay case 50. In the illustrated embodiment, thesensor 82A is positioned directly adjacent to thelower portion 142 of thehousing 54. If thedrain 138 becomes blocked or clogged, liquid will no longer drain from thedisplay case 50 and will begin to accumulate on thelower portion 142 of thehousing 54. As the liquid accumulates, thesensor 82A deflects upwardly, changing the signal output to theelectronics 78. Theelectronics 78 may then trigger an alarm or warning to notify an operator to check thedrain 138. - In a further construction, the
sensor 82A measures an oil level within thecompressor 14. In such a construction, thesensor 82A is positioned generally at the location of thesensor 74C inFIG. 1 . Due to turbulence within the compressor 14 (e.g., oil turbulence), it may be less desirable to use a float arrangement to measure the oil level in thecompressor 14. As such, thesensor 82A is coupled to a gear driven piece of thecompressor 14, such as a shaft, that rotates based on the oil level within thecompressor 14. As the oil level rises, the shaft rotates in a first direction so that thesensor 82A wraps around the shaft. The resistance of thesensor 82A, and thereby the signal output to the sensing andconditioning electronics 78, increases as thesensor 82A wraps around the shaft. As the oil level falls, the shaft rotates in a reverse direction so that thesensor 82A unwraps from the shaft. The resistance of thesensor 82A, and thereby the signal output to theelectronics 78, decreases as thesensor 82A unwraps from the shaft. Based on the signal output by thesensor 82A, theelectronics 78 may notify an operator of the current oil level or trigger an alarm or warning if the oil level rises above or falls below an acceptable level. -
FIG. 6 illustrates the secondflexible sensor 82B configured to measure an applied force or to monitor movement of asecondary structure 146. In the illustrated embodiment, theflexible sensor 82B is disposed within anelastic material 150 and coupled to the secondary structure 146 (e.g., a hinge, a shelf, a switch, or the like) such that any movement of thesecondary structure 146 is transferred to thesensor 82B. As one portion of thesecondary structure 146 moves relative to another portion of thesecondary structure 146 due to the applied force, bending, rotation, or the like, thesensor 82B deflects a proportionate amount. Similar to the construction discussed above with reference toFIG. 3 , thesensor 82B is electrically coupled to the sensing andconditioning electronics 78. - In one construction, the
secondary structure 146 is a hinge that couples thedoor 62 to thehousing 54 of thedisplay case 50. For example, theflexible sensor 82B is coupled to the hinge such that one end of the sensor 82Bis securely fastened to a first half of the hinge, and another end of thesensor 82B is securely fastened to a second half of the hinge. In such a construction, thesensor 82B is positioned generally at the location of thesensor 74K inFIG. 1 . When thedoor 62 is closed, the hinge is substantially straight such that thesensor 82B is likewise substantially straight. As thedoor 62 opens, the first half of the hinge rotates relative to the second half, deflecting thesensor 82B and changing the signal output to theelectronics 78. If thedoor 62 is left open for a prolonged period of time or if thedoor 62 is left slightly ajar, such that the deflection of thesensor 82B is small, theelectronics 78 can trigger an alarm or warning to notify an operator to check thedoor 62. - In another construction, the
secondary structure 146 is one of theshelves 66 within theproduct display area 58 of thedisplay case 50. In such a construction, thesensor 82B is positioned generally at the location of thesensors 74L inFIG. 1 . Theflexible sensor 82B is used to monitor a load condition (e.g., a weight of food product) on theshelf 66, rather than having to constantly visually monitor theshelf 66. When theshelf 66 is filled with food product, theshelf 66 deflects, causing thesensor 82B to deflect and output a corresponding signal to theelectronics 78. As the food product is removed from theshelf 66, theshelf 66 deflects less and less until theshelf 66, and thereby thesensor 82B, substantially straightens. When theshelf 66 and thesensor 82B are only deflected a small amount, thesensor 82B outputs a different signal to theelectronics 78. Theelectronics 78 can then trigger an alarm or warning to notify an operator to check and restock theshelf 66, if necessary. - In yet another construction, the
secondary structure 146 is a switch of acircuit breaker 154 for theproduct display case 50. In such a construction, thesensor 82B is positioned generally at the location of thesensor 74M inFIG. 1 . The illustratedcircuit breaker 154 is electrically coupled to theevaporator 30 to provide power to theevaporator fan 46. However, it should be readily apparent that thecircuit breaker 154 may be electrically coupled to other components of therefrigeration system 10 and/or the display case 50 (e.g., lights, fans, etc.). Theflexible sensor 82B is coupled to one of the switches of thecircuit breaker 154 such that an operator is given instant notification if one of the circuits becomes tripped. For example, when the circuit is closed, the switch is flipped to one side, bending thesensor 82B to output a positive voltage. When the circuit is opened, the switch is flipped to the other side, bending thesensor 82B to output a negative voltage. The change in voltages from positive to negative (or vise versa) is output to theelectronics 78, which triggers an alarm or warning to notify the operator of the tripped circuit. - In still another construction, the
secondary structure 146 is a contactor. As shown inFIG. 1 , afirst contactor 158 is electrically coupled to thecompressor 14 to provide power to thecompressor 14 and asecond contactor 162 is electrically coupled to thecondenser 18 to provide power to thecondenser fan 38. In such a construction, thesensor 82B is positioned generally at the location of thesensor 74N and/or thesensor 74P inFIG. 1 . As such, thesensor 82B is coupled to a switch of each contactor 158, 162 to monitor the position of the switch in a similar manner to thecircuit breaker 154 described above. Thesensor 82B provides information to an operator regarding a status of thecontactors sensor 82B can monitor when the switches move to a position where thecontactors compressor 14 andcondenser 18, respectively, so the operator knows if thecompressor 14 and thecondenser 18 should be running. -
FIG. 7 illustrates anotherrefrigeration system 200 according to an embodiment of the invention. Therefrigeration system 200 includes afirst refrigeration unit 210 and asecond refrigeration unit 212. Similar to therefrigeration system 10 discussed above with reference toFIG. 1 , thefirst refrigeration unit 210, or primary refrigeration loop, includescompressors 214, acondenser 218, areceiver 222, anexpansion valve 226, and anevaporator 230. In the illustrated embodiment, threecompressors 214 are arranged in parallel; however, it should be readily apparent that fewer or more compressors may be included, or thecompressors 214 may be arranged in series. Thefirst refrigeration unit 210 circulates a first, or primary, refrigerant that is in a heat exchange relationship with a second refrigerant of thesecond refrigeration unit 212 at theevaporator 230. Reference is hereby made to the description of therefrigeration system 10 above for discussion of the operation of thefirst refrigeration unit 210. - The illustrated
second refrigeration unit 212, or secondary refrigeration loop, includes theevaporator 230, apump 234, and threedisplay cases 250. Thepump 234 may be any positive displacement pump, centrifugal pump, or the like suitable to move and circulate the second refrigerant. The illustratedpump 234 generates a driving force to draw the second refrigerant from theevaporator 230 and direct the second refrigerant toward and through thedisplay cases 250. - The
display cases 250 may be similar to thedisplay case 50 discussed above with reference toFIG. 1 . In the illustrated embodiment, thesecond refrigeration unit 212 includes threedisplay cases 250 arranged in parallel. However, in other embodiments, thesecond refrigeration unit 212 may include fewer ormore display cases 250 depending on the capacity of therefrigeration system 200. Eachdisplay case 250 includes an evaporator or heat exchanger configured to receive the second refrigerant in a liquid or liquid/vapor state and facilitate heat exchange between the second refrigerant and air within thedisplay case 250. Thedisplay cases 250 thereby maintain a temperature suitable for refrigerating or freezing food product within thecases 250. - In operation, the second refrigerant is circulated through the
second refrigeration unit 212 by thepump 234. In other embodiments, a compressor upstream of theevaporator 230 compresses and circulates the second refrigerant. At theevaporator 230, the second refrigerant comes into a heat exchange relationship with the first refrigerant in thefirst refrigeration unit 210 to remove heat from the second refrigerant. The second refrigerant is then drawn through thepump 234 and directed toward thedisplay cases 250. The second refrigerant exchanges heat with the air in thedisplay cases 250 to remove heat from the air. Then, the second refrigerant is directed back toward theevaporator 230 to once again remove heat from the second refrigerant with the first refrigerant. - In the illustrated embodiment, the
refrigeration system 200 also includes aflexible sensor 274 positioned in thesecond refrigeration unit 212. Although only onesensor 274 is shown, it should be readily apparent to one skilled in the art that therefrigeration system 200 may include multiple flexible sensors positioned throughout thesecond refrigeration unit 212, as well as throughout thefirst refrigeration unit 210, or at any location corresponding to thesensors 74A-74P discussed above with reference toFIG. 1 . Theflexible sensor 274 is similar to theflexible sensor 82A discussed above with reference toFIG. 2A , and measures a property of thesecond refrigeration unit 212. The illustratedsensor 274 is positioned to measure a fluid flow (e.g., a refrigerant flow) downstream of thepump 234. By measuring the speed and/or volume of the fluid flow, thesensor 274 can determine if thepump 234 is functioning properly. If necessary, thesensor 274 can trigger an alarm or warning to notify an operator that the pump 234 (or other portion of the second refrigeration unit 212) needs maintenance. -
FIG. 8 illustrates anevaporative cooler 300 according to an embodiment of the invention. Theevaporative cooler 300, or swamp cooler, can be used as a stand-alone cooling system or in combination with either of therefrigeration systems evaporative cooler 300 includes ahousing 304, ablower 308 positioned within thehousing 304,evaporator pads 312, and apump 316. Thehousing 304 is configured to surround, protect, and support the other components of theevaporative cooler 300. In the illustrated embodiment, thehousing 304 includesvents 320 to facilitate air flow into theevaporative cooler 300 and is configured to retain a supply ofwater 324. Thehousing 304 also includes aduct 328 configured to direct a cool air flow out of theevaporative cooler 300 and toward the desired location. In some embodiments, theduct 328 may direct the cool air flow into a secondary heat exchanger (e.g., an evaporator) such that the cool air flow does not come into direct contact with the environment being cooled. - The illustrated
blower 308 includes a fan 332 (e.g., a centrifugal fan) and amotor 336 coupled to thefan 332 to drive thefan 332. In the illustrated embodiment, both thefan 332 and themotor 336 are supported within thehousing 304. In other embodiments, themotor 336 may be positioned outside of the housing 204 to allow easier access to themotor 226. The fan 223 draws the air flow into theevaporative cooler 300 through thevents 320 and directs the cool air flow out through theduct 328. - The
evaporator pads 312 are positioned within thehousing 304 adjacent to thevents 320. Theevaporator pads 312 may be composed of, for example, excelsior, melamin paper, or plastic. Theevaporator pads 312 are configured to temporarily retain water to cool the air flow. As the air flow passes through thepads 312, heat in the air flow evaporates the water in thepads 312, cooling the air flow. The cool air flow then flows through theduct 328 to the desired location. As shown inFIG. 8 , the cool air flow may pass over thewater supply 324 in thehousing 304 to further cool and humidify the air flow prior to entering theduct 328. - The
pump 316 is positioned within thehousing 304 and is in communication with thewater supply 324. Thepump 316 supplies water to theevaporator pads 312 to remoisten thepads 312 when the air flow evaporators the water on thepads 312. Awater distribution line 340 is coupled to thepump 316 to direct water from thepump 316 onto thepads 312. The illustrateddistribution line 340 includes twooutlets 344 configured to evenly spray the water over theevaporator pads 312. When theevaporative cooler 300 is running, thepump 316 draws water from thewater supply 324 and directs the water through thedistribution line 340. The water is ejected from thedistribution line 340 at theoutlets 344 and sprayed onto theevaporator pads 312 to reapply water to thepads 312 such that the air flow through thepads 312 is continuously cooled. - In the illustrated embodiment, the
evaporative cooler 300 also includes threeflexible sensors flexible sensors sensor 82A discussed above with reference toFIG. 2A and are used to measure properties of theevaporative cooler 300. For example, thefirst sensor 374A is positioned adjacent to thewater supply 324 to measure the water level within thehousing 304. As such, thefirst sensor 374A may be configured similar to the construction shown inFIG. 5 . That is, thefirst sensor 374A may include a float and bend upwardly to notify an operator that the water level is becoming too high, or bend downwardly to notify the operator that the water level is becoming too low. Similar to the previous constructions, thesensor 374A is coupled to sensing and conditioning electronics that trigger an alarm or warning to notify the operator of either change in the water level. - The
second sensor 374B and thethird sensor 374C are positioned adjacent to theoutlets 344 of the water distribution lines 340. When theevaporative cooler 300 is not in operation and water is not being sprayed from thedistribution line 340, thesensors distribution line 340 and onto theevaporator pads 312, thesensors sensors conductive material 90 and, thereby, the signal output by thesensors evaporative cooler 300 is in operation and functioning properly. If one thesensors evaporative cooler 300, the electronics can notify the operator to check thecorresponding distribution line 340 for a clog or rupture. - Flexible sensors provide a reliable means to measure various properties of refrigeration systems. In particular, the sensors are impervious to the operating environment of a commercial refrigeration system. For example, the sensors are not affected by dust, moisture, low operating temperatures of refrigerant, or varying temperatures of an air flow. In addition, the sensor can withstand in excess of thirty million cycles, but are still relatively cost effective. Furthermore, the flexible sensors include no moving parts or active electronic devices that may need servicing or replacement over time.
- Various features and advantages of the invention are set forth in the following claims.
Claims (46)
1. A refrigeration system comprising:
a compressor configured to compress a refrigerant;
a condenser in fluid communication with the compressor and configured to remove heat from the refrigerant;
an expansion valve in fluid communication with the condenser and configured to decrease a pressure of the refrigerant;
an evaporator in fluid communication with the expansion valve and configured to facilitate heat exchange between the refrigerant and another fluid; and
a sensor configured to bend to measure a property of the refrigeration system, the sensor including
a flexible substrate, and
a conductive material applied to the flexible substrate and having a resistance that changes in response to bending of the flexible substrate to generate a signal indicative of the property.
2. The refrigeration system of claim 1 , wherein the sensor includes a sleeve positioned around at least a portion of the flexible substrate.
3. The refrigeration system of claim 1 , wherein the property is a liquid flow within at least one component of the refrigeration system.
4. The refrigeration system of claim 3 , wherein the liquid flow is a refrigerant flow.
5. The refrigeration system of claim 3 , wherein the liquid flow is an oil flow.
6. The refrigeration system of claim 3 , wherein failure of the expansion valve is determined by measuring the liquid flow with the sensor.
7. The refrigeration system of claim 3 , wherein a position of the expansion valve is determined by measuring the liquid flow with the sensor.
8. The refrigeration system of claim 3 , wherein a run time of the compressor is determined by measuring the liquid flow with the sensor.
9. The refrigeration system of claim 1 , wherein the property is an air flow.
10. The refrigeration system of claim 9 , wherein a demand defrost is triggered by measuring the air flow with the sensor.
11. The refrigeration system of claim 9 , wherein at least one of the condenser and the evaporator includes a fan, and wherein failure of the fan is determined by measuring the air flow with the sensor.
12. The refrigeration system of claim 9 , further comprising a display case including an air return grille, wherein blockage of the air return grille is determined by measuring the air flow with the sensor.
13. The refrigeration system of claim 9 , wherein blockage of the condenser is determined by measuring the air flow with the sensor.
14. The refrigeration system of claim 1 , wherein the property is a fluid level within at least one component of the refrigeration system.
15. The refrigeration system of claim 14 , further comprising a receiver configured to hold a portion of the refrigerant, wherein the fluid level is a refrigerant level within the receiver.
16. The refrigeration system of claim 14 , wherein the fluid level is an oil level within the compressor.
17. The refrigeration system of claim 14 , further comprising a display case including a drain, wherein blockage of the drain is determined by measuring the fluid level within the display case with the sensor.
18. The refrigeration system of claim 1 , further comprising a display case including a door, wherein the property is a position of the door.
19. The refrigeration system of claim 1 , further comprising a display case including a shelf, wherein the property is a load condition of the shelf.
20. The refrigeration system of claim 1 , further comprising a circuit breaker, wherein the property is a status of the circuit breaker.
21. The refrigeration system of claim 1 , further comprising a contactor configured to transmit power to at least one component of the refrigeration system, wherein the property is a status of the contactor.
22. The refrigeration system of claim 1 , further comprising a second refrigeration unit configured to circulate a second refrigerant that exchanges heat with the first-mentioned refrigerant, wherein the property is a fluid flow within the second refrigeration unit.
23. A method of measuring a property of a refrigeration system, the refrigeration system including a compressor, a condenser in fluid communication with the compressor, an expansion valve in fluid communication with the condenser, and an evaporator in fluid communication with the expansion valve, the method comprising:
providing a sensor including a flexible substrate and a conductive material applied to the flexible substrate, the conductive material having a resistance that changes in response to bending of the flexible substrate;
compressing a refrigerant with the compressor;
removing heat from the refrigerant with the condenser;
decreasing a pressure of the refrigerant with the expansion valve;
exchanging heat between the refrigerant and another fluid with the evaporator; and
bending the sensor to generate a signal indicative of a property of the refrigeration system.
24. The method of claim 23 , wherein bending the sensor includes bending the sensor to measure a liquid flow within at least one component of the refrigeration system.
25. The method of claim 24 , wherein the liquid flow is a refrigerant flow.
26. The method of claim 24 , wherein the liquid flow is an oil flow.
27. The method of claim 24 , wherein bending the sensor to measure a liquid flow includes bending the sensor to determine a failure of the expansion valve.
28. The method of claim 24 , wherein bending the sensor to measure a liquid flow includes bending the sensor to determine a position of the expansion valve.
29. The method of claim 24 , wherein bending the sensor to measure a liquid flow includes bending the sensor to determine a run time of the compressor.
30. The method of claim 23 , wherein bending the sensor includes bending the sensor to measure an air flow within at least one component of the refrigeration system.
31. The method of claim 30 , wherein bending the sensor to measure an air flow includes bending the sensor to trigger a demand defrost.
32. The method of claim 30 , wherein at least one of the condenser and the evaporator includes a fan, and wherein bending the sensor to measure an air flow includes bending the sensor to determine a fan failure.
33. The method of claim 30 , wherein the refrigeration system further includes a display case having an air return grille, and wherein bending the sensor to measure an air flow includes bending the sensor to determine blockage of the air return grille.
34. The method of claim 30 , wherein bending the sensor to measure an air flow includes bending the sensor to determine blockage of the condenser.
35. The method of claim 23 , wherein bending the sensor includes bending the sensor to measure a fluid level within at least one component of the refrigeration system.
36. The method of claim 35 , wherein the refrigerant system further includes a receiver configured to hold a portion of the refrigerant, and wherein bending the sensor to measure a fluid level includes bending the sensor to measure a refrigerant level within the receiver.
37. The method of claim 35 , wherein bending the sensor to measure a fluid level includes bending the sensor to measure an oil level within the compressor.
38. The method of claim 35 , wherein the refrigeration system further includes a display case having a drain, and wherein bending the sensor to measure a fluid level includes bending the sensor to determine blockage of the drain.
39. The method of claim 23 , wherein the refrigeration system further includes a display case having a door, and wherein bending the sensor includes bending the sensor to determine a position of the door.
40. The method of claim 23 , wherein the refrigeration system further includes a display case having a shelf, and wherein bending the sensor includes bending the sensor to determine a load condition of the shelf.
41. The method of claim 23 , wherein the refrigeration system further includes a circuit breaker, and wherein bending the sensor includes bending the sensor to determine a status of the circuit breaker.
42. The method of claim 23 , wherein the refrigeration system further includes a contactor configured to transmit power to at least one component of the refrigeration system, and wherein bending the sensor includes bending the sensor to determine a status of the contactor.
43. The method of claim 23 , wherein the refrigeration system further includes a second refrigeration unit configured to circulate a second refrigerant that exchanges heat with the first-mentioned refrigerant, and wherein bending the sensor includes bending the sensor to measure a fluid flow within the second refrigeration unit.
44. An evaporative cooler comprising:
a housing having at least one vent and configured to contain water;
a blower positioned within the housing and configured to draw air through the at least one vent;
an evaporator pad positioned adjacent to the at least one vent;
a pump configured to spray at least a portion of the evaporator pad with the water; and
a sensor configured to bend to measure a property of the evaporative cooler, the sensor including
a flexible substrate, and
a conductive material applied to the flexible substrate and having a resistance that changes in response to bending of the flexible substrate to generate a signal indicative of the property.
45. The evaporative cooler of claim 44 , wherein the property is a water level within the housing.
46. The evaporative cooler of claim 44 , wherein the property is a spray flow from the pump.
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US11/847,534 US20090056353A1 (en) | 2007-08-30 | 2007-08-30 | Refrigeration system including a flexible sensor |
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US11/847,534 US20090056353A1 (en) | 2007-08-30 | 2007-08-30 | Refrigeration system including a flexible sensor |
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