U.S. patent application number 11/519433 was filed with the patent office on 2008-03-13 for system for monitoring the performance of a gas absorption cooling unit and related method.
Invention is credited to David Leistner, Santosh Nerur, Carl Onken, Wayne A. Schneider.
Application Number | 20080060366 11/519433 |
Document ID | / |
Family ID | 39168195 |
Filed Date | 2008-03-13 |
United States Patent
Application |
20080060366 |
Kind Code |
A1 |
Leistner; David ; et
al. |
March 13, 2008 |
System for monitoring the performance of a gas absorption cooling
unit and related method
Abstract
The present teachings provide control systems and methods for
monitoring the performance of an absorption refrigerator. The
system includes a temperature sensor that senses the temperature of
a generator of a cooling arrangement. The circuit may communicate
with the sensor and turn off a heat source of the cooling unit if a
sensed temperature condition of the generator exceeds a
predetermined temperature condition.
Inventors: |
Leistner; David; (Sidney,
OH) ; Schneider; Wayne A.; (Botkins, OH) ;
Onken; Carl; (Idaho Falls, ID) ; Nerur; Santosh;
(Asheville, NC) |
Correspondence
Address: |
HARNESS, DICKEY & PIERCE, P.L.C.
P.O. BOX 828
BLOOMFIELD HILLS
MI
48303
US
|
Family ID: |
39168195 |
Appl. No.: |
11/519433 |
Filed: |
September 12, 2006 |
Current U.S.
Class: |
62/148 ;
62/497 |
Current CPC
Class: |
F25B 49/043 20130101;
F25B 2333/003 20130101; F25B 2333/002 20130101 |
Class at
Publication: |
62/148 ;
62/497 |
International
Class: |
F25B 33/00 20060101
F25B033/00; F25B 15/00 20060101 F25B015/00 |
Claims
1. A control system for a refrigerator having an absorption cooling
arrangement with a generator, the control system having: a
temperature sensor adapted to sense a temperature proximate the
generator; a control device selectively operative to turn off a
heat source of the control system; and a circuit in communication
with the sensor and the control device, the circuit adapted to
determine a sensed temperature condition and control the control
device to turn off the heat source if the sensed temperature
condition exceeds a predetermined temperature condition.
2. The system according to claim 1, wherein the control device is
operative in a first mode for allowing operation of the heat source
and a second mode for preventing operation of the heat source.
3. The system according to claim 2, wherein the circuit controls
the control device to operate in the first mode when the sensed
temperature condition is above the predetermined temperature
condition and in the second mode when the sensed temperature
condition is below the predetermined temperature condition.
4. The system according to claim 3, further comprising a memory
device to store an indication of whether the circuit has operated
the control device in the second mode.
5. The system according to claim 1, wherein the control device is a
valve in line with a gas source.
6. The system according to claim 1, wherein the control device is a
switch in series with a power source for the refrigerator.
7. The system according to claim 1, wherein the sensed temperature
condition is a sensed temperature and the predetermined temperature
condition is a predetermined temperature.
8. The system according to claim 1, wherein the sensed temperature
condition is a function of time of a sensed temperature within one
or more temperature bands above a predetermined temperature.
9. The system according to claim 1, in combination with the
refrigerator.
10. An absorption refrigerator comprising: an interior volume; an
absorption system to cool the interior volume, the absorption
cooling system including a generator; a heat source to provide the
energy to drive the absorption cooling system by heating the
generator; a temperature sensor adapted to sense a temperature of
the generator; and a circuit in communication with the sensor and
the control device, the circuit adapted to determine a sensed
temperature condition and control the control device to turn off
the heat source if the sensed temperature condition exceeds a
predetermined temperature condition.
11. The absorption refrigerator of claim 10, wherein the circuit
includes a control device for turning off the heat source.
12. The absorption refrigerator of claim 11, wherein the absorption
refrigerator further comprises a power source and wherein the
control device comprises a switch in series with the power
source.
13. The absorption refrigerator of claim 10, wherein the absorption
refrigerator includes a burner flame powered by a source of fuel
and the control device comprises a valve positioned between the
source of fuel and the burner flame.
14. The absorption refrigerator of claim 10, wherein the sensed
temperature condition is a sensed temperature and the predetermined
temperature condition is a predetermined temperature.
15. The absorption refrigerator of claim 10, wherein the sensed
temperature condition is a function of time of a sensed temperature
within one or more temperature bands above a predetermined
temperature.
16. The absorption refrigerator of claim 10, wherein the
temperature sensor is positioned proximate the generator.
17. The absorption refrigerator of claim 10, further comprising a
canister, the generator and the temperature sensor disposed within
the canister.
18. The method of claim 10, wherein the generator includes a boiler
tube and a plurality of electric heater tubes, each heater tube
mounted to the boiler tube with a pair of welds extending
substantially along the length of the respective heater tube.
19. A method of controlling a cooling system of an absorption
refrigerator, the method comprising: sensing a temperature of a
generator of the cooling system; determining a sensed temperature
condition; comparing the sensed temperature condition to a
predetermined temperature condition; and turning off a heat source
of the cooling system when the sensed temperature condition is
above the predetermined temperature condition.
20. The method of claim 18, wherein the turning off a heat source
of the cooling system when the sensed temperature condition is
above the predetermined temperature condition includes one of: the
step of opening a switch positioned between a power source of the
refrigerator and the heat source; and closing a valve positioned
between a gas source and a burner flame of the cooling system.
Description
INTRODUCTION
[0001] Absorption refrigerators provide quiet operation and employ
heat to vaporize the coolant--water mixture (typically
ammonia--water) thereby driving the refrigeration loop. Popular
heat sources include electrical heaters and fuel burners. The fuel
burners typically employ propane which is readily available at
camping supply stores, barbeque supply stores, and numerous gas
stations. Though, any liquid or gaseous fuel would work well and be
controllable through simple, automated control systems.
[0002] The heat source drives a generator for heating a coolant
mixture to release ammonia vapor. The generator has an optional
temperature range. Operation of the generator outside this optional
temperature range may result in compromised performance.
[0003] It remains a need in the pertinent art to provide an
improved system for monitoring the performance of a cooling unit of
an absorption refrigerator by controlling heating of the generator
under predetermined temperature conditions.
SUMMARY
[0004] According to one aspect, the present teachings provide a
control system for a refrigerator having an absorption cooling
arrangement with a generator. The control system may include a
control circuit with a temperature sensor that senses the
temperature of a generator. The circuit may communicate with a
signal from the cooling unit that indicates when a predetermined
temperature condition has been exceeded. The circuit may also
communicate with the sensor and turn off the power to the
refrigerator upon sensing of a predetermined temperature condition.
Alternatively, the circuit may communicate with the sensor to turn
off the heat source of the cooling unit.
[0005] According to another aspect, the present teachings provide
an absorption refrigerator defining an interior volume and
including an absorption system to cool the interior volume. The
absorption system includes a generator. A heat source provides
energy to drive the absorption cooling system. A temperature sensor
may be adapted to sense a temperature of the generator. A circuit
may be in communication with the sensor. The circuit may be adapted
to turn off the heat source if a sensed temperature condition
exceeds a predetermined temperature condition.
[0006] In another aspect, the present teachings may provide a
method of controlling a cooling unit. The method may include
sensing a temperature of a generator of the cooling system and
determining a sensed temperature condition of the generator. The
method may additionally include the step of comparing the sensed
temperature condition to a predetermined temperature condition. The
method may further comprise the step of turning off a heat source
of the cooling system when the sensed temperature condition exceeds
the predetermined temperature condition.
[0007] In still yet another aspect, the present teachings may
provide a gas absorption cooling arrangement including a boiler
tube and a plurality of electric heater tubes. At least one of the
electric heater tubes may be secured to the boiler tube through a
pair of welds. The pair of welds may extend substantially along the
length of the respective electric heater tube.
[0008] Further areas of applicability of the present teachings will
become apparent from the detailed description provided hereinafter.
It should be understood that the detailed description and specific
examples, while indicating the particular embodiments of the
present teachings, are intended for purposes of illustration only
and are not intended to limit the scope of the invention.
DESCRIPTION OF THE DRAWINGS
[0009] The present teachings will become more fully understood from
the detailed description and the accompanying drawings,
wherein:
[0010] FIG. 1 is a rear perspective view of an exemplary gas
absorption refrigerator including a control system in accordance
with the present teachings.
[0011] FIG. 2 is a schematic view of the control system of an
absorption refrigerator in accordance with the present
teachings.
[0012] FIG. 3 is an enlarged detail view of a portion of the
refrigerator of an absorption refrigerator including a control
system in accordance with the present teachings, a sensor shown
mounted in close proximity to a generator of the cooling
arrangement.
[0013] FIG. 4 is an enlarged perspective view similar to FIG. 3
shown with the canister removed for purposes of illustration.
[0014] FIG. 5 is an enlarged perspective view of a sensor mounting
bracket of FIGS. 2 and 3 shown removed from the remainder of the
absorption refrigerator for purposes of illustration.
[0015] FIG. 6 is an enlarged perspective view of a canister
mounting bracket according to the present teachings.
[0016] FIG. 7 is a top view of the canister mounting bracket of
FIG. 5.
[0017] FIG. 8 is a schematic view of a control device of the
control system of the present teachings, the control device
illustrated as a switch in series with the main power (e.g., +12
VDC) that powers the refrigerator.
[0018] FIG. 9 is a schematic view of an alternative control device
of the control system of the present invention, the control device
illustrated as a valve in line with a gas source and the burner
flame.
[0019] FIG. 10 is a flow-chart illustrating a method in accordance
with the present invention for evaluating the operational
performance of an absorption refrigerator.
[0020] FIG. 11 is a front view of a portion of an absorption
cooling system in accordance with the present teachings, the
cooling system shown to include three electric heater tubes secured
to a boiler tube.
[0021] FIG. 12 is a cross-sectional view taken along the line 12-12
of FIG. 11.
DESCRIPTION OF VARIOUS ASPECTS
[0022] The following description of the present teachings is merely
exemplary in nature and is in no way intended to limit the
invention, its application, or uses.
[0023] The methods and systems described herein can be applied to a
wide variety of cooling units. For the purpose of illustration,
though, a typical absorption refrigeration system is used that has
a cold storage compartment. Those skilled in the art will
understand that the illustrative refrigeration system does not
limit the invention in any way, but is used only to explain the
invention.
[0024] With general reference to the drawings, an exemplary
absorption refrigerator 10 including a control system in accordance
with the present teachings is illustrated. The refrigerator 10
includes a cooling system 11 including an absorption cooling
arrangement 12 mounted on a back wall 14 of a cabinet 16. The
cabinet 16 encloses an insulated compartment (not specifically
shown). The cooling arrangement 12 may include conventional gas
absorption cooling components. In this regard, the cooling
arrangement 12 may include an absorber, an evaporator, a condenser
and a generator. The generator includes a boiler tube. Insofar as
the present invention is concerned, it will be understood that
these basic components of the gas absorption refrigerator 10 are
conventional in both construction and operation.
[0025] The cooling arrangement 12 may be controlled electrically or
with a gas source. In this regard, the cooling arrangement 12 may
additionally include a DC electrical heater, an AC electrical
heater and a gas burner. The cooling arrangement 12 may further
include a burner and control box 18. The generator and heaters may
be contained within a generator enclosure or canister 20 that
upwardly extends proximate the burner box 18.
[0026] As is well known in the art of absorption cooling, the
coolant mixture (typically ammonia and water) is heated in the
generator or boiler tube 22 to preferentially releasing ammonia
vapor. From the generator, the ammonia vapor flows to the
condenser. In the condenser, the ammonia vapor cools and condenses.
By gravity, the cool liquid ammonia flows from the condenser and
into the evaporator. In the evaporator, the liquid ammonia absorbs
heat from the interior of the refrigerator 10 thereby cooling the
interior of the refrigerator 10. The vaporized ammonia then flows
from the evaporator to the absorber where the partially depleted
water--ammonia mixture absorbs the ammonia vapor to complete the
refrigeration cycle.
[0027] Heat is required to vaporize the ammonia in the
ammonia--water mixture. The heat source may be an electrical
heater, a burner flame, or any other conventional heat source. More
particularly, the electric heater may be either an A/C (e.g., 240
V.A.C.) or a D.C. (e.g., 12-48 V.D.C) heater. In the alternative,
both types of electrical heaters and a burner flame may be provided
with controls to allow the user to switch between the three sources
of heat. When the refrigerator 10 is operating with the electrical
heat source a relatively large quantity of electrical power must be
supplied from a source external to the refrigerator 10 (e.g. from
the recreational vehicle electrical system or from a hook up
provided at the camp site). In certain applications, the
refrigerator 10 may automatically choose the best available energy
source upon which to operate.
[0028] It is desirable to operate the generator of the cooling
arrangement 12 within an optimum temperature range. Accordingly,
the present inventors recognized a need to monitor a temperature
condition of the generator and control the cooling arrangement 12
when the generator temperature condition is outside an optimum
temperature range, thereby improving the cooling performance
efficiency of the cooling arrangement 12 inside the refrigerator
10.
[0029] Turning now to the schematic illustration of FIG. 2, the
control system 11 defines a control circuit that communicates with
a temperature sensor 24 and a control device 26. The control
circuit 25 may include a control panel 28 having a processor 30, a
PROM, EEPROM, an ASIC chip, a hardwired circuit or the like. The
temperature sensor 24 may be a thermocouple, a thermistor, an RTD
(resistance thermal detector), or any other temperature sensing
device that is well known in the art.
[0030] The circuit 25 may operate to control the control device 24
to turn off the source of heat to generator or boiler tube 22 when
a second temperature exceeds a predetermined temperature condition.
The predetermined temperature condition may simply be a
predetermined temperature. It will be noted that the predetermined
temperature may be significantly above the optimum operating range
of the generator temperature. The circuit 25 may alternatively or
additionally operate to maintain the generator temperature
substantially within the optimum operating range. In this regard,
the circuit 25 may operate to reduce the source of heat to the
generator upon detection of a generator temperature above the
optimum operating range. The source of heat may be reduced by
temporary interruption of the power source (e.g., the power to the
unit 10 or the gas source) until such time that the generator
temperature is sufficiently within the optimal operating range.
Conversely, the circuit 25 may operate to increase the source of
heat to the generator upon detection of a generator temperature
below the optimum operating range.
[0031] In FIGS. 3 and 4, an exemplary location of the thermal
sensor 24 is shown. In FIG. 4, the canister 20 is shown removed and
the thermal sensor 24 is shown proximate the generator 22 of the
absorption cooling arrangement 12. The thermal sensor 24 may be
carried by a mounting bracket 36.
[0032] The mounting bracket 36 may include a first portion or lower
portion 38 that may be secured to the burner box 18. The lower
portion 38 may be secured with discrete fasteners 40, through
welding, or in any other suitable manner. The mounting bracket 36
may additionally include an upper portion 44 to which the sensor 24
may be mounted. The mounting bracket 36 may be constructed from
metal. Importantly, the sensor 24 is positioned within the canister
20 proximate the generator or boiler tube 22.
[0033] Turning to FIGS. 6 and 7, another sensor mounting structure
in the form of a canister bracket 50 is illustrated. The canister
bracket 50 will be understood to effectively define a lower portion
of the canister 20. In this regard, the canister bracket 50 has a
diameter roughly equivalent to the diameter of the canister 20. An
upper portion of the canister bracket 50 may be secured to the
canister 20 with fasteners 40 or welds. A lower portion of the
canister bracket 50 may be secured to the burner box 18 with
fasteners 40 or welds. The lower portion of the canister bracket 50
is provided with an apertured mounting tab 54 for this purpose.
[0034] The canister bracket 50 may include a sensor mounting
portion 56. The sensor mounting portion 56 may be inwardly
displaced from a cylindrical wall 58 of the canister bracket 50.
The sensor mounting portion 56 may include a general planar segment
60 to which the sensor 24 may be conventionally attached.
Importantly, the sensor 24 is positioned within the canister 20 for
sensing of the generator temperature.
[0035] As shown in FIGS. 6 and 7, the canister bracket 50 may be
formed of a single piece to define the sensor mounting portion 56.
Alternatively, the sensor mounting portion 56 may be a discrete
element that engages the remainder of the canister bracket 50. Such
an alternative may provide for easier manufacturing,. In either
case, the canister bracket 50 may be formed of metal.
[0036] Turning to FIG. 8, a schematic diagram illustrates one
control device 26. The control device is illustrated as a switch 26
in series with the absorption cooling arrangement 12 and a main
source of power 64 (e.g., +12 VDC) for powering the refrigerator
10. The switch 26 is controlled to open and thereby power down the
refrigerator 10 in response to detection of a generator temperature
condition outside a predetermined temperature condition.
[0037] Turning to FIG. 9, schematically illustrated is an
alternative control device 66. The control device includes a
control valve 66 positioned in line between a source of gas 66 and
a burner flame 70. The control valve 66 may be controlled to close
in response to detection of a generator temperature condition above
the predetermined temperature condition, for example.
[0038] During operation, the circuit 25 receives signals
representative of the temperature of the generator 22 from the
temperature sensor 24. If a sensed generator temperature condition
is calculated to be above the predetermined temperature condition,
the circuit 25 may operate the control device 26 or 66. In this
regard, the sensed generator temperature condition may simply be
the sensed generator temperature and the predetermined temperature
condition may simply mean a predetermined temperature.
Alternatively, the sensed temperature condition may be a function
of elapsed time within one or more temperature bands above a
predetermined temperature. In this scenario, the predetermined
temperature condition may be a predetermined time within on or more
temperature bands above the predetermined temperature. In this
regard, impact to the generator performance may be significantly
more critical at increasingly higher temperatures above the
predetermined temperature. In such an arrangement, a computer may
continuously calculate the sensed temperature condition.
[0039] The refrigerator 10 may incorporate a three-way heat supply
including both an A.C and a D.C. heater along with a fuel system
for the fire heat source. Accordingly, a relay may be provided to
open the current paths to the A.C. and D.C. heaters and to close
the valve 66, thereby ensuring that the three heat sources are each
turned off when it is desired to stop driving the generator. Note
also, that if it should become necessary to turn off the heat
source(s), the circuit 25 may illuminate a monitor (not shown) to
alert the user to the possibility that the refrigerator 10 may need
attention and/or maintenance. Thus, those skilled in the art will
recognize that reference to opening and closing the valve 66
includes turning the electric heaters off and on (e.g., through
opening and closing of the switch 26) as applicable. Conversely,
reference to turning the electric heaters off and on includes
opening and closing the valve 66.
[0040] In the event that the sensed temperature condition of the
generator remains above the predetermined temperature condition,
the circuit 25 may suspend further heating of the generator 22.
When the condition clears, the circuit 25 may resume commanding the
control device 26. In certain applications, the control system 11
may operate such that the control device 26 renders further heating
of the generator impossible until the control system 11 is reset.
For such applications, a reset switch may be provided to reset the
circuit 25. The reset switch may be a push button switch.
Alternatively, the reset switch may be a toggle switch or any other
well known device capable of generating a binary (i.e., on/off)
signal for the circuit. Upon being reset, the circuit 25 clears the
control system 11 and begins monitoring the temperature sensor 24
anew. The circuit 25 may include a memory for storing an indication
of whether the sensed temperature condition of the generator
exceeded the predetermined temperature condition. The memory may be
a flip flop, a relay, RAM or any conventional device capable of
storing a binary state. Resetting of the circuit 25 may require
authorized maintenance of the refrigerator 10.
[0041] In alternative embodiments, if the circuit closes the valve
66 or opens the switch 26 because the sensed temperature condition
of the generator 22 is above the predetermined temperature
condition, the circuit 25 may wait for pre-selected time. At the
end of the time, the circuit 25 may then re-open the valve 66 (or
the switch 26) and allow the heat source to resume driving the
cooling system 12. If the predetermined temperature condition is
again exceeded, the circuit 25 may then close the valve 66 (or open
the switch 26) again. Moreover, because two attempts to produce the
desired performance appear to have not succeeded, the circuit 25
preclude further heating of the generator.
[0042] Turning now to FIG. 10, an exemplary method in accordance
with the present invention is illustrated. The method 100 includes
sensing the temperature of the cooling system 12 proximate the
generator. In a first step 102, the sensed temperature is compared
to a predetermined temperature. If the sensed temperature is less
than the pre-determined temperature then step 102 repeats until
such time that the temperature increases above the pre-determined
temperature. When the temperature rises above the pre-determined
temperature, then step 104 operates the control device 26 or 66 to
discontinue heating of the cooling arrangement. If a reset occurs,
the method includes returning to step 102.
[0043] Accordingly, it will be understood that a control
arrangement or the present teachings may be incorporated into a
passive in-line device for a refrigerator 10. In this regard, the
present teachings may be utilized without a need to modify normal
refrigerator controls by simply interrupting a source of heating
power upon sensing of a predetermined temperature condition.
Alternatively, the present teachings may be incorporated into a
microprocessor configured to receive a signal indicative of a
predetermined sensed temperature condition. The microprocessor may
accordingly control the refrigerator otherwise in the manner
discussed herein.
[0044] Turning to FIGS. 11 and 12, a portion of a gas absorption
cooling system 120 is illustrated. The cooling system 120 includes
a boiler tube 122. A plurality of electric heater tubes 124 are
secured to boiler tube 122. The heater tubes 124 may be each
secured to the boiler tube 122 through a pair of welds 126. Through
the incorporation of multiple heater tubes 124 each with a pair of
welds 126, an arrangement is provided which reduces heat flux
across the electric heater tube welds, reduces temperatures on the
boiler and lowers thermal stress on the boiler.
[0045] The description of the invention is merely exemplary in
nature and, thus, variations that do now depart from the gist of
the invention are intended to be within the scope of the invention.
Such variations are not to be regarded as a departure from the
spirit and scope of the invention.
* * * * *