U.S. patent application number 11/483258 was filed with the patent office on 2007-02-15 for electrically controlled defrost and expansion valve apparatus.
Invention is credited to Ran Luo, Kenneth W. Owen.
Application Number | 20070033955 11/483258 |
Document ID | / |
Family ID | 39033457 |
Filed Date | 2007-02-15 |
United States Patent
Application |
20070033955 |
Kind Code |
A1 |
Luo; Ran ; et al. |
February 15, 2007 |
Electrically controlled defrost and expansion valve apparatus
Abstract
A cooling system that has an electrical controller that controls
an electric expansion valve and the defrost cycle using a reversing
valve. The need for heater circuit to achieve defrost is
eliminated. The system permits the defrosting the evaporator system
in less time required for conventional defrost methods. The cooling
system also eliminates the need for a head pressure control valve
and check valves. Due to the less wiring and lower operating costs,
the invention provides significant cost savings.
Inventors: |
Luo; Ran; (New Albany,
MS) ; Owen; Kenneth W.; (New Albany, MS) |
Correspondence
Address: |
William B. Ritchie;Law Office of William B. Ritchie
1411 Northern Heights Drive NE
Rochester
MN
55906-4045
US
|
Family ID: |
39033457 |
Appl. No.: |
11/483258 |
Filed: |
July 7, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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10888561 |
Jul 9, 2004 |
7073344 |
|
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11483258 |
Jul 7, 2006 |
|
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60485836 |
Jul 10, 2003 |
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Current U.S.
Class: |
62/150 ; 62/151;
62/160 |
Current CPC
Class: |
F25B 2700/21174
20130101; F25B 2700/21175 20130101; F25D 21/006 20130101; F25B
47/025 20130101; F25B 13/00 20130101; F25B 2700/2104 20130101 |
Class at
Publication: |
062/150 ;
062/160; 062/151 |
International
Class: |
F25D 21/00 20060101
F25D021/00; F25D 21/06 20060101 F25D021/06; F25B 13/00 20060101
F25B013/00 |
Claims
1. A refrigeration system for a cooling a space comprising: a
compressor to compress a refrigerant gas; a reversing valve
connected to said compressor; a condenser connected to said
reversing valve which receives the hot pressurized refrigerant gas
provided by said compressor; wherein said condenser finctions as a
heat exchanger to allow the refrigerant gas to dissipate the heat
of pressurization such that the refrigerant condenses into a
liquid; an electric expansion valve connected to said condenser
wherein the refrigerant passing through said expansion valve
expands and evaporates; a controller electrically connected to said
electric expansion valve and to said reversing valve; an evaporator
connected to said electric expansion valve wherein the evaporating
refrigerant absorbs heat from a space to be cooled; and wherein
said controller modulates a superheat temperature provided by said
evaporator until a predetermined temperature is reached; and
wherein once said controller is set to defrost cycle, said
controller causes said reversing valve to reverse, said electrical
expansion valve is further opened, and said refrigeration system
enters a defrost mode.
2. The refrigeration system of claim 1 wherein said controller can
be set to defrost in accordance with a predetermined time that
elapses between defrost cycles.
3. The refrigeration system of claim 1 wherein said controller can
be set to defrost by actuating a manual setting.
4. The refrigeration system of claim 1 wherein said controller can
be set to defrost by demand defrost as determined by said
controller.
5. The refrigeration system of claim 1 wherein said controller
further comprises: a cooling space temperature sensor that
indicates the temperature in the cooled space so that said
controller can control the cooling cycle of said refrigeration
system.
6. The refrigeration system of claim 5 wherein said controller
further comprises: a first evaporator temperature sensor positioned
adjacent to the evaporator on the connection between said
evaporator and said electric expansion valve.
7. The refrigeration system of claim 6 wherein said controller
further comprises; a second evaporator temperature sensor
positioned on the connection between said evaporator and said
compressor wherein said second evaporator temperature sensor is
adjacent to said evaporator but outside the cooled space.
8. The refrigeration system of claim 7 wherein the superheat of
said evaporator is determined by said controller by measuring said
first evaporator temperature sensor and said second evaporator
temperature sensor.
9. The refrigeration system of claim 8 wherein during a defrost
cycle, said controller causes said electrical expansion valve to
open ranging 40 to 60% of the maximum open position.
10. The refrigeration system of claim 8 wherein if said second
evaporator temperature sensor indicates to said controller that the
temperature is greater than or equal to a defrost termination
temperature set in said controller, said controller ends the
defrost cycle and causes said refrigeration system to enter a drip
mode.
Description
[0001] This application is a continuation application of U.S.
patent application Ser. No. 10/888,561 filed on Jul. 9, 2004, to be
issued on Jul. 11, 2006 as U.S. Pat. No. 7,073,344 which claims the
benefit of U.S. Provisional Application No. 60/485,836 filed Jul.
10, 2003.
FIELD OF THE INVENTION
[0002] This invention relates generally to space cooling systems,
in particular to apparatus for controlling a space cooling system
with respect to the defrost cycle.
BACKGROUND OF THE INVENTION
[0003] A typical space cooling system includes at least one
evaporator system contained within the space that is to be cooled,
a condenser system that is located outside of the cooled space, and
a compressor positioned between the condenser system outlet and the
evaporator system inlet and, finally, an expansion valve which
completes the loop joining together the condenser system outlet and
the evaporator system inlet. A refrigerant is circulated within the
loop which cools the space as follows. The refrigerant is
compressed by the compressor which raises the temperature and
pressure of the refrigerant. The hot pressurized refrigerant gas
then flows through the condenser system which serves as heat
exchanger to allow the refrigerant to dissipate the heat of
pressurization. The refrigerant condenses into a liquid and then
flows through the expansion valve, where the liquid refrigerant
moves from a high pressure zone into a low pressure zone, thus
expanding and evaporating. In evaporating, the refrigerant becomes
cold where it then passes into coils of the evaporator, thus
absorbing heat from inside the space that is to be cooled and the
cycle then repeats until the space reaches the desired
temperature.
[0004] In addition to these major components, additional components
are also included. A fan assist the heat transfer from the cooled
space to the coils of the evaporator system and another fan is used
to assist the heat transfer from the coils of the condenser to
outside environment. A negative pressure differential is present on
the evaporator outlet when the device is operating in a
refrigeration mode thereby suctioning the gas refrigerant to the
compressor. Further, thermistor sensors are placed at the inlet and
outlet of the evaporator system for measuring the level of
superheat across the evaporator. A sensor located on the outlet
side of the compressor measures the discharge temperature of
compressor. The ambient temperature of the spaced to be cooled is
measured by still another sensor. Finally, the need to defrost the
evaporator from any ice build-up due to the cooling process is
determined by another sensor that is associated with evaporator so
that defrosting procedures can be monitored.
[0005] There are two basic options for providing a defrost cycle.
U.S. Pat. No. 5,551,248, issued to Derosier on Sep. 3, 1996,
discloses the use of a controller to control the operation of a
space cooling system. While this device permits the use of an
electrically controlled expansion valve, either utilizing an
electrically operated solenoid or an electrically operated step
motor, Derosier also teaches the use of heater which is activated
on a programmed time schedule, either a time between successive
defrost cycles or a compressor run time. The use of heater for
providing defrost function requires the additional expense of the
heater as well as associated valving, piping and supply wiring
connections. Additionally, there must a pumpdown condition present
before defrost procedures can begin and the fans must remain on
during pumpdown.
[0006] Another option is disclosed by Russell of Brea, Calif. in
its HIGH SIERRA model refrigeration device. This device teaches the
use of reversing valve which permits the elimination of the heater.
However, the HIGH SIERRA model requires the use of check valve at
the outlet of the compressor and another check valve in the drain
pan circuit as well as additional piping and connection fittings.
Most importantly, the HIGH SIERRA model does not disclose or
suggest the use of an electrical controller which permits, among
other things, the use of electrically controlled expansion valve
such as taught by Derosier.
[0007] An refrigeration apparatus that has both an electrical
controller that responds to evaporator superheat and return air
temperature to the expansion valve as well as controls a reversing
valve which provides for a defrosting cycle, eliminates the need
for electric heaters, check valves, head pressure control valve as
well as the associated piping and connections is not found in the
prior art.
SUMMARY OF THE INVENTION
[0008] It is an aspect of the invention to provide a refrigeration
system that provides an electrical controller that controls the
electric expansion valve and the defrost cycle using a reversing
valve.
[0009] It is another aspect of the invention to provide a
refrigeration system that eliminates the need for a heater circuit
to achieve a defrost of the evaporator system.
[0010] It is still another aspect of the invention to provide a
refrigeration system that permits defrosting the evaporator system
in less than the time required for a conventional electronic
defrost system.
[0011] Further, another aspect of the invention is to provide a
refrigeration system that leaves the evaporator coil virtually
clean after each defrost cycle.
[0012] It is another aspect of the invention to provide a
refrigeration system that eliminates the need for a head pressure
control valve.
[0013] Another aspect of the invention is to provide a
refrigeration system that eliminates the need for check valves and
an expansion valve at the condenser.
[0014] Still another aspect of the invention is to provide a
refrigeration system that has less wiring and is less expensive to
produce and operate than present devices.
[0015] It is another aspect of the invention to provide a
refrigeration system that requires no pumpdown before the defrost
cycle has been initiated.
[0016] It is another aspect of the invention to provide a
refrigeration system that enables the compressor to run during
defrost.
[0017] It is still another aspect of the invention to provide a
refrigeration system wherein the need to defrost is determined by
the controller and defrost will only occur when it is necessary
thus saving energy costs associated with unnecessary defrost.
[0018] Finally, it is another aspect of the invention to provide a
refrigeration system that prevents steaming and heat from being
introduced into the cooled space during the defrost cycle.
[0019] These and other aspects of the invention will become
apparent in light of the detailed description of the invention
which follows.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 is a schematic of the most basic embodiment of the
invention operating during a refrigeration cycle.
[0021] FIG. 2 is a schematic of the embodiment shown in FIG. 1
operating during a defrost cycle.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0022] While certain representative embodiments of the invention
have been described herein for the purposes of illustration, it
will be apparent to those skilled in the art that modification
therein may be made without departure from the spirit and scope of
the invention. Like parts are referenced in the specification and
accompanying figures with the same reference call out numbers. Note
that the drawings are not necessarily to scale and that some
elements may be larger or smaller or otherwise oriented to more
clearly depict the important features of the invention.
[0023] As shown in FIG. 1. which depicts the basic elements of the
invention 10, the refrigeration cycle is similar to that discussed
above for the typical space cooling device discussed in the
background. However, note that unlike prior art devices, invention
10 includes both a controller 12 and a reversing valve 24 which are
discussed below. Refrigerant (not shown) is compressed by the
compressor 26. The temperature and pressure of the refrigerant is
raised. The hot pressurized refrigerant gas then flows through the
reversing valve 24 to the condenser system 22. As above, condenser
system 22 functions as a heat exchanger to allow the refrigerant to
dissipate the heat of pressurization. The refrigerant condenses
into a liquid and then flows through the expansion valve 20, where
the liquid refrigerant moves from a high pressure zone into a low
pressure zone, thus expanding and evaporating. Electric expansion
valve 20 is preferably a step motor such as manufactured by
companies such as Sporlan, Alco, Parker or Danfoss. The refrigerant
flow of the electric expansion valve 20 is controlled by controller
12 and is modulated to control the superheat of the evaporator 28.
The superheat of evaporator 28 is determined by measuring sensor 16
and 18 using techniques well known in the art. In evaporating, the
refrigerant then passes into coils of the evaporator 28, thus
absorbing heat from inside the space 30 that is to be cooled and
the cycle then repeats until the space reaches the desired
temperature as provided by sensor 14.
[0024] The controller 12 can be set to defrost mode that is either
electric (using standard heater technology) or reverse cycle
(utilizing the instant invention). When the reverse cycle defrost
option is selected, the following sequence will be used as shown in
FIG. 2.
[0025] When there is a demand for defrost whether by set time
schedule or manual defrost or demand defrost as determined by the
controller 12, the controller 12 sends a signal to reverse valve
assembly 24. Reverse valve assembly 24 is readily available from
companies such as Ranco, Alco, Danfoss and Sanhua. This type of
valve is typically used on heat pumps. As shown in FIG. 2, the
refrigerant flows change from refrigerating cycle to defrost
cycle.
[0026] Simultaneously, the electrical expansion valve 20 is forced
open ranging from 40% to 60% of maximum. Controller 12 then checks
sensors 16 and 18. If the temperature at sensor 18 indicates that
it is greater than or equal to the defrost termination temperature
(DTT), the defrost ends and then goes to a drip mode. The default
setting on controller 12 is preferably ranges from 40.degree. F. to
approximately 50.degree. F. If 40.degree. F.>Sensor
16-DTT>20.degree. F., expansion valve 20 is changed ranging from
20% to 30% of the fully open position. The temperature monitored at
sensor 16 will keep rising. If 99.degree. F.>sensor
16>=40.degree. F.+DTT, the controller 12 will again close the
expansion valve 20 ranging from 5% to 15% of the fully open
position. Sensor 18 will continue to be monitored to determine
whether the DTT temperature has been reached. As noted, once it
has, the defrost ends. This process will repeat until sensor 18
indicates that the DTT temperature has been reached and then
defrost ends.
[0027] The sensor 18 is monitored continuously by controller 12 to
determine the coil temperature rise of evaporator 28 relative to
the DTT temperature. When the temperature reading on sensor 18 is
greater than or equal to the pre-set DTT, defrost is considered to
be complete and controller 12 will enter the drip mode and close
the expansion valve 20 completely. Compressor 26 may pumpdown the
refrigerant and may be cut off by the low-pressure control of
compressor 26. While the compressor 26 is engaged in the pumpdown
mode, the evaporator fans (not shown) remain off. Compressor 26 may
also be shut off by controller 12 if so wired.
[0028] Reversing valve assembly 24 is not de-energized until the
end of the drip mode. The refrigerant flows change from defrost
cycle to refrigerating cycle when controller 12 enters the fan
delay mode (cool mode if the fan delay mode is skipped) after drip
mode. If the pumpdown after a defrost cycle takes longer than drip
mode, the controller 12 will enter fan delay mode even though the
pumpdown may not be completed. For example, if a pumpdown takes 4
minutes to complete and the drip time is pre-set to 3 minutes, when
the 3 minute drip time expires, controller 12 will enter fan delay
mode and expansion valve 20 will be modulating. Note the compressor
26 may be running through pumpdown mode, drip mode and fan delay
mode. A reverse cycle defrost is considered complete when the
controller 12 enters the fan delay mode. As noted above, when there
is no defrost, all operations are the same as current version of
the applicant's electric expansion valve refrigeration control
system which is well known in the art.
[0029] Although the present invention has been described in
considerable detail with reference to certain preferred versions
thereof, other versions would be readily apparent to those of
ordinary skill in the art. Therefore, the spirit and scope of the
appended claims should not be limited to the description of the
preferred versions contained herein.
* * * * *