U.S. patent application number 11/847534 was filed with the patent office on 2009-03-05 for refrigeration system including a flexible sensor.
This patent application is currently assigned to HUSSMANN CORPORATION. Invention is credited to Ted W. Sunderland.
Application Number | 20090056353 11/847534 |
Document ID | / |
Family ID | 40405346 |
Filed Date | 2009-03-05 |
United States Patent
Application |
20090056353 |
Kind Code |
A1 |
Sunderland; Ted W. |
March 5, 2009 |
REFRIGERATION SYSTEM INCLUDING A FLEXIBLE SENSOR
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.
Inventors: |
Sunderland; Ted W.; (Troy,
MO) |
Correspondence
Address: |
MICHAEL BEST & FRIEDRICH LLP
100 E WISCONSIN AVENUE, Suite 3300
MILWAUKEE
WI
53202
US
|
Assignee: |
HUSSMANN CORPORATION
Bridgeton
MO
|
Family ID: |
40405346 |
Appl. No.: |
11/847534 |
Filed: |
August 30, 2007 |
Current U.S.
Class: |
62/214 ;
62/498 |
Current CPC
Class: |
F25D 7/00 20130101; G01F
1/28 20130101; F25D 17/06 20130101; F25B 2700/13 20130101; G01F
23/241 20130101; F25D 29/008 20130101; G01F 23/24 20130101; F25B
2700/135 20130101; F25D 2323/0023 20130101; F25D 2700/02 20130101;
F25D 23/003 20130101; F25D 25/02 20130101; F25B 2700/04 20130101;
G01F 23/36 20130101 |
Class at
Publication: |
62/214 ;
62/498 |
International
Class: |
F25D 29/00 20060101
F25D029/00 |
Claims
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.
Description
BACKGROUND
[0001] The present invention relates to refrigeration systems and,
particularly, to refrigeration systems that include sensors to
measure properties of the refrigeration systems.
[0002] 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.
[0003] 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.
SUMMARY
[0004] 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.
[0005] 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.
[0006] 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.
[0007] Other aspects of the invention will become apparent by
consideration of the detailed description and accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a schematic of a refrigeration system according to
an embodiment of the invention.
[0009] FIG. 2A is planar view of a flexible sensor for use with the
refrigeration system shown in FIG. 1.
[0010] FIG. 2B is a planar view of another flexible sensor for use
with the refrigeration system shown in FIG. 1.
[0011] FIG. 3 is a schematic of a flexible sensor configured to
measure a liquid flow.
[0012] FIG. 4 is a schematic of a flexible sensor configured to
measure an air flow.
[0013] FIG. 5 is a schematic of a flexible sensor configured to
measure a fluid level.
[0014] FIG. 6 is a schematic of a flexible sensor configured to
measure a load on a secondary structure.
[0015] FIG. 7 is a schematic of another refrigeration system
according to an embodiment of the present invention.
[0016] FIG. 8 is a cross-sectional view of an evaporative cooler
according to an embodiment of the present invention.
DETAILED DESCRIPTION
[0017] 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.
[0018] 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. In the illustrated embodiment, 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. However, it should be readily apparent to
one skilled in the art that 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.
[0019] 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.
[0020] The condenser 18 is positioned downstream of the compressor
14 to receive the vaporous, compressed refrigerant. In the
illustrated embodiment, 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. In other embodiments, 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.
[0021] 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.
[0022] 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.
[0023] 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.
[0024] 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. In the
illustrated embodiment, 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.
[0025] In operation, 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. In some embodiments, such as the illustrated
embodiment, 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.
[0026] As shown in FIG. 1, the illustrated refrigeration system 10
also includes a plurality of flexible sensors 74A-74P. The sensors
74A-74P are shown schematically to illustrate their general
position relative to the other components of the refrigeration
system 10. Each flexible 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 the refrigeration system 10. In
some embodiments, the refrigeration system 10 may include only one
or a few of the illustrated sensors 74A-74P, depending on which
system properties the operator wishes to monitor. In other
embodiments, the refrigeration system 10 may include sensors
located at additional or alternative locations to measure other
system properties.
[0027] FIGS. 2A and 2B illustrate two constructions of flexible
sensors 82A, 82B for use with the refrigeration system 10 shown in
FIG. 1. In the illustrated embodiment, both sensors 82A, 82B
include generally the same components and function in a generally
similar manner, and, thereby, like parts are given the same
reference numerals. In some embodiments, such as the illustrated
embodiment, each flexible sensor is a Bend Sensor.RTM. provided by
Flexpoint Sensor Systems, Inc. of Draper, Utah.
[0028] Each sensor 82A, 82B 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 82A, 82B. 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.
[0029] 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 82A, 82B will output a different voltage or
current based on the degree of deflection of the material 90. In
the illustrated embodiment, 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 82A, 82B not only measures the degree of deflection, but
also the direction of deflection. For example, when the flexible
sensor 82A, 82B deflects in one direction, the sensor 82A, 82B
outputs a positive voltage. When the flexible sensor 82A, 82B
deflects in the opposite direction, the sensor 82A, 82B outputs a
negative voltage. In some embodiments, the material 90 may be a
conductive ink printed on the substrate 86.
[0030] The sleeve 94, or sheath, surrounds the substrate 86 and the
conductive material 90 to protect the flexible sensor 82A, 82B. In
the illustrated embodiment, the sleeve 94 seals the substrate 86
from the environment to inhibit contaminants (e.g., dust, frost,
liquid, etc.) from contacting conductive material 90. In some
embodiments, the sleeve 94 has bend characteristics that are
substantially similar to the flexible substrate 86.
[0031] The connection area 98 facilitates electrically coupling the
sensors 82A, 82B to the sensing and conditioning electronics 78.
Referring to the construction shown in FIG. 2A, the connection area
98 includes a plug 102 to allow quick connecting and disconnecting
with the electronics 78. Referring to the construction shown in
FIG. 2B, the connection area 98 includes electrical leads 106 to
allow the sensor 82A, 82B to be spaced further away from the
electronics 78.
[0032] FIG. 3 illustrates the first flexible sensor 82A in a fluid
conduit 110 to measure a liquid flow. In the illustrated
embodiment, the flexible sensor 82A 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 82A. Such heating
keeps the sensor 82A from adhering, or freezing, to the resistors
114, 118 or the conduit 110. As a liquid (e.g., refrigerant, oil,
etc.) flows over and past the flexible sensor 82A, the sensor 82A
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.
[0033] For example, in one construction, the flexible sensor 82A
may be used to monitor refrigerant flow in the refrigeration system
10. In such a construction, the sensor 82A 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.
[0034] In another construction, the sensor 82A may be positioned
downstream of the expansion valve 26 to monitor the status of the
valve 26. In such a construction, the sensor 82A is positioned
generally at the location of the sensor 74A in FIG. 1. Based on the
measured speed or volume of the refrigerant, the sensor 82A 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. 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, the flexible 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
the electronics 78.
[0035] In yet another construction, the sensor 82A may be
positioned downstream of the compressor 14 to monitor the status of
the compressor 14. In such a construction, the sensor 82A is
positioned generally at the location of the sensor 74B in FIG. 1.
Based on the measured refrigerant flow output by the compressor 14,
the sensor 82A and the electronics 78 can determine a run time of
the compressor 14 and output the run time to an operator.
[0036] In a further construction, the sensor 82A may be positioned
within the compressor 14 to monitor an oil flow inside the
compressor 14. In such a construction, the sensor 82A is positioned
generally at the location of the sensor 74C in FIG. 1. Based on the
oil flow measured by the sensor 82A, 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.
[0037] FIG. 4 illustrates the first flexible sensor 82A in an air
passageway 122 to measure an air flow. Similar to the construction
described above with reference to FIG. 3, the sensor 82A 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 82A, the sensor
82A 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.
[0038] In one construction, the flexible sensor 82A is used to
measure an off coil air velocity at the evaporator 30. In such a
construction, the sensor 82A is positioned generally at the
location of the sensor 74D in FIG. 1. When the evaporator 30 is
operating properly, air flows past the evaporator coil 42 and
deflects the sensor 82A. However, over time 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. When the air flow through the
coil 42 is reduced, the sensor 82A is no longer deflected (or not
deflected as much), changing the signal output to the electronics
78. 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.
[0039] In another construction, the flexible sensor 82A is used to
determine a fan failure. In such a construction, the sensor 82A is
positioned generally at the location of sensor 74E or sensor 74F in
FIG. 1 to monitor the condenser fan 38 or the evaporator fan 46,
respectively. When the fans 38, 46 are functioning properly (e.g.,
propelling air over their respective coils 34, 42), the sensors 82A
are deflected by the air flow. However, if either fan 38, 46 stops
running, the corresponding sensor 82A 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
this failure.
[0040] In yet another construction, the flexible sensor 82A is used
to determine if an air return grille 126 of the display case 50 is
blocked. In such a construction, the sensor 82A is positioned
generally at the location of the sensor 74G in FIG. 1. During
normal operation, air flows from the evaporator 30, through the air
passageway 70, through the product display area 58, and back to the
air passageway 70 through the air return grille 126. As the air
flows through the grille 126, the sensor 82A 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 82A, 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.
[0041] In a similar construction, the flexible sensor 82A is used
to determine if the condenser 18 is blocked. In such a
construction, the sensor 82A is positioned generally at the
location of the sensor 74H in FIG. 1. The sensor 82A is slightly
upstream of the condenser fan 38 to monitor when the condenser fan
38 pulls ambient air through the condenser 18. As air is pulled
through the condenser 18 by the fan 38, the sensor 82A is deflected
and outputs a corresponding signal to the electronics 78. If 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
82A 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.
[0042] FIG. 5 illustrates the first flexible sensor 82A configured
to measure a fluid level. In the illustrated embodiment, the
flexible sensor 82A is positioned adjacent to only one large body
resistor 114; however, in other embodiments, the sensor 82A may be
positioned between two resistors. Similar to the construction
described above with reference to FIG. 3, the flexible sensor 82A
is electrically coupled to the sensing and conditioning electronics
78.
[0043] As shown in FIG. 5, a float 130 is coupled to an end of the
sensor 82A opposite from a support 134, or wall. When the fluid
level rises and contacts the float 130, the float 130 rises and
deflects the sensor 82A. In some configurations, the sensor 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,
the sensor 82A may start at a bent position and move to the
substantially straight position to measure a decrease in the fluid
level. As such, the flexible sensor 82A may be used to measure when
the fluid level is greater than or less than a desired, or
acceptable, level.
[0044] In one construction, the flexible sensor 82A is used to
measure a refrigerant level (e.g., a refrigerant charge) within the
receiver 22. In such a construction, the sensor 82A is positioned
generally at the location of the sensor 741 in FIG. 1. The sensor
82A 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 82A
is deflected upwardly due to the float 130 rising with the
refrigerant, changing the signal output by the sensor 82A (e.g., to
a positive voltage) to the electronics 78. If the refrigerant level
falls, the sensor 82A deflects downwardly due to gravity, changing
the signal output by the sensor 82A (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.
Although the flexible sensor 82A is described starting at the
substantially straight position, it should be readily apparent to
one skilled in the art that the sensor 82A may start at a bent
position, either upwardly or downwardly, that corresponds to the
acceptable refrigerant level.
[0045] In another construction, the flexible sensor 82A is used to
determine if a drain 138 of the display case 50 is clogged or
blocked. In such a construction, the sensor 82A is positioned
generally at the location of the sensor 74J 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. In the illustrated embodiment,
the sensor 82A is positioned directly adjacent to the lower portion
142 of the housing 54. If 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 82A 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.
[0046] In a further construction, the sensor 82A measures an oil
level within the compressor 14. In such a construction, the sensor
82A is positioned generally at the location of the sensor 74C 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. As such, the sensor 82A
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 82A wraps around the shaft. The resistance of
the sensor 82A, and thereby the signal output to the sensing and
conditioning electronics 78, increases as the sensor 82A wraps
around the shaft. As the oil level falls, the shaft rotates in a
reverse direction so that the sensor 82A unwraps from the shaft.
The resistance of the sensor 82A, and thereby the signal output to
the electronics 78, decreases as the sensor 82A unwraps from the
shaft. Based on the signal output by the sensor 82A, 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.
[0047] FIG. 6 illustrates the second flexible sensor 82B configured
to measure an applied force or to monitor movement of a secondary
structure 146. In the illustrated embodiment, the flexible sensor
82B 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 82B. As one portion of the secondary
structure 146 moves relative to another portion of the secondary
structure 146 due to the applied force, bending, rotation, or the
like, the sensor 82B deflects a proportionate amount. Similar to
the construction discussed above with reference to FIG. 3, the
sensor 82B is electrically coupled to the sensing and conditioning
electronics 78.
[0048] In one construction, the secondary structure 146 is a hinge
that couples the door 62 to the housing 54 of the display case 50.
For example, the flexible 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 the sensor 82B is securely
fastened to a second half of the hinge. In such a construction, the
sensor 82B is positioned generally at the location of the sensor
74K in FIG. 1. When the door 62 is closed, the hinge is
substantially straight such that the sensor 82B is likewise
substantially straight. As the door 62 opens, the first half of the
hinge rotates relative to the second half, deflecting the sensor
82B and changing the signal output to the electronics 78. If the
door 62 is left open for a prolonged period of time or if the door
62 is left slightly ajar, such that the deflection of the sensor
82B is small, the electronics 78 can trigger an alarm or warning to
notify an operator to check the door 62.
[0049] In another construction, the secondary structure 146 is one
of the shelves 66 within the product display area 58 of the display
case 50. In such a construction, the sensor 82B is positioned
generally at the location of the sensors 74L in FIG. 1. The
flexible sensor 82B 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. When the shelf 66 is
filled with food product, the shelf 66 deflects, causing the sensor
82B to deflect and output a corresponding signal to the electronics
78. As the food product is removed from the shelf 66, the shelf 66
deflects less and less until the shelf 66, and thereby the sensor
82B, substantially straightens. When the shelf 66 and the sensor
82B are only deflected a small amount, the sensor 82B 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.
[0050] In yet another construction, the secondary structure 146 is
a switch of a circuit breaker 154 for the product display case 50.
In such a construction, the sensor 82B is positioned generally at
the location of the sensor 74M in FIG. 1. The illustrated circuit
breaker 154 is electrically coupled to the evaporator 30 to provide
power to the evaporator fan 46. However, it should be readily
apparent that 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 82B
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. For example, when the circuit is closed,
the switch is flipped to one side, bending the sensor 82B to output
a positive voltage. When the circuit is opened, the switch is
flipped to the other side, bending the sensor 82B 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.
[0051] In still another construction, 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. In such
a construction, the sensor 82B is positioned generally at the
location of the sensor 74N and/or the sensor 74P in FIG. 1. As
such, the sensor 82B 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 82B provides
information to an operator regarding a status of the contactors
158, 162. For example, the sensor 82B 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.
[0052] 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. Similar to the refrigeration system 10
discussed above with reference to FIG. 1, 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. In the illustrated embodiment, 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. Reference is hereby
made to the description of the refrigeration system 10 above for
discussion of the operation of the first refrigeration unit
210.
[0053] The illustrated second refrigeration unit 212, or secondary
refrigeration loop, 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.
[0054] The display cases 250 may be similar to the display case 50
discussed above with reference to FIG. 1. In the illustrated
embodiment, 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.
[0055] In operation, the second refrigerant is circulated through
the second refrigeration unit 212 by the pump 234. In other
embodiments, a compressor upstream of the evaporator 230 compresses
and circulates the second refrigerant. At the evaporator 230, 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. Then, the second
refrigerant is directed back toward the evaporator 230 to once
again remove heat from the second refrigerant with the first
refrigerant.
[0056] In the illustrated embodiment, the refrigeration system 200
also includes a flexible sensor 274 positioned in the second
refrigeration unit 212. Although only one sensor 274 is shown, it
should be readily apparent to one skilled in the art that the
refrigeration system 200 may include multiple flexible sensors
positioned throughout the second refrigeration unit 212, as well as
throughout the first refrigeration unit 210, or at any location
corresponding to the sensors 74A-74P discussed above with reference
to FIG. 1. The flexible sensor 274 is similar to the flexible
sensor 82A 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. By measuring the
speed and/or volume of the fluid flow, the sensor 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.
[0057] 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. In the
illustrated embodiment, 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. In some
embodiments, 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.
[0058] 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. In the illustrated embodiment, both the fan 332 and
the motor 336 are supported within the housing 304. In other
embodiments, 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.
[0059] 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.
[0060] 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. When the evaporative cooler 300
is running, 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.
[0061] In the illustrated embodiment, the evaporative cooler 300
also includes three flexible sensors 374A, 374B, 374C. The flexible
sensors 374A, 374B, 374C are similar to the sensor 82A discussed
above with reference to FIG. 2A and are used to measure properties
of the evaporative cooler 300. For example, the first sensor 374A
is positioned adjacent to the water supply 324 to measure the water
level within the housing 304. As such, the first sensor 374A may be
configured similar to the construction shown in FIG. 5. That is,
the first 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, the sensor
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.
[0062] The second sensor 374B and the third sensor 374C are
positioned adjacent to the outlets 344 of the water distribution
lines 340. When the evaporative cooler 300 is not in operation and
water is not being sprayed from the distribution line 340, the
sensors 374B, 374C are substantially straight. As water is sprayed
out of the distribution line 340 and onto the evaporator pads 312,
the sensors 374B, 374C are deflected by the sprayed water.
Deflecting the sensors 374B, 374C changes the resistance of the
conductive material 90 and, thereby, the signal output by the
sensors 374B, 374C 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 374B,
374C 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.
[0063] 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.
[0064] Various features and advantages of the invention are set
forth in the following claims.
* * * * *