U.S. patent application number 12/650249 was filed with the patent office on 2010-04-29 for system and method for controlling working fluid charge in a vapor compression air conditioning system.
This patent application is currently assigned to TRANE INTERNATIONAL INC.. Invention is credited to Jonathan David DOUGLAS, James Thomas SCHAEFER, JR., Gregory F. WALTERS.
Application Number | 20100101246 12/650249 |
Document ID | / |
Family ID | 38947869 |
Filed Date | 2010-04-29 |
United States Patent
Application |
20100101246 |
Kind Code |
A1 |
DOUGLAS; Jonathan David ; et
al. |
April 29, 2010 |
System and Method For Controlling Working Fluid Charge In A Vapor
Compression Air Conditioning System
Abstract
Vapor compression air conditioning systems are provided with a
flow restrictor for transferring working fluid to and from at least
one of the compressor low pressure inlet conduit and compressor
high pressure outlet conduit to provide for accurate charge
adjustment to achieve predetermined fluid sub-cooling. Pressure and
temperature measurements are taken at a condenser fluid outlet
conduit and provided to a microcontroller for determining fluid
sub-cooling and comparing sub-cooling with a predetermined target
sub-cooling. A charge addition or recovery apparatus may include a
solenoid valve controlled by the microcontroller to more accurately
control the addition or recovery of refrigerant fluid charge.
Inventors: |
DOUGLAS; Jonathan David;
(Bullard, TX) ; SCHAEFER, JR.; James Thomas;
(Tyler, TX) ; WALTERS; Gregory F.; (Tyler,
TX) |
Correspondence
Address: |
CONLEY ROSE, P.C.
5601 GRANITE PARKWAY, SUITE 750
PLANO
TX
75024
US
|
Assignee: |
TRANE INTERNATIONAL INC.
Piscataway
NJ
|
Family ID: |
38947869 |
Appl. No.: |
12/650249 |
Filed: |
December 30, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11486874 |
Jul 14, 2006 |
|
|
|
12650249 |
|
|
|
|
Current U.S.
Class: |
62/77 ;
62/149 |
Current CPC
Class: |
F25B 2345/002 20130101;
F25B 2700/21163 20130101; F25B 2700/195 20130101; F25B 41/40
20210101; F25B 2345/001 20130101; F25B 2345/003 20130101; F25B
45/00 20130101 |
Class at
Publication: |
62/77 ;
62/149 |
International
Class: |
F25B 45/00 20060101
F25B045/00 |
Claims
1. A method for adjusting the charge of working fluid in a vapor
compression air conditioning system including a compressor, a low
pressure conduit, a high pressure conduit, a condenser unit
operably connected to said high pressure conduit and to a condenser
discharge conduit, a pressure sensor and a temperature sensor
operably associated with said condenser discharge conduit for
measuring a pressure and a temperature of the working fluid, the
temperature and the pressure being related to a working fluid
sub-cooling, a working fluid flow restrictor device operably
associated with at least one of said conduits for at least one of
transferring fluid to and from said system, said method comprising:
measuring the temperature and the pressure of the working fluid
within the condenser discharge conduit, the temperature and the
pressure corresponding to sub-cooling of the working fluid flowing
through said system; comparing said sub-cooling with a target
sub-cooling operating condition of said working fluid to determine
if a charge of working fluid should be added to said system or
recovered from said system; and carrying out at least one of adding
working fluid to said system and recovering working fluid from said
system by restricting the flow of working fluid with said flow
restrictor device.
2. The method set forth in claim 1 including the step of:
determining system running time prior to measuring said one or more
working fluid parameters.
3. The method set forth in claim 1 including the step of:
determining the variance of sub-cooling of said working fluid over
a predetermined interval of time.
4. The method set forth in claim 1 including the step of: providing
a signal to an operator of said system of a need to one of recover
working fluid from said system and add working fluid to said
system.
5. The method set forth in claim 4 including the step of one of:
recovering working fluid and adding working fluid continuously
until a predetermined amount of sub-cooling is measured indicating
a desired charge of working fluid.
6. The method set forth in claim 3 including the step of: providing
a fluid charge adding apparatus including a reservoir, a conduit
connected to said reservoir and a valve interposed in said conduit;
and providing a signal indicating a condition requiring providing
working fluid to said system from said apparatus.
7. The method set forth in claim 6 wherein: said valve is motor
operated and said signal is provided to said valve to provide
operation thereof to control flow of working fluid to said
system.
8. A method of charging a vapor compression air conditioning
system, comprising: measuring a temperature of a working fluid
exiting a condenser of the system; measuring a pressure of the
working fluid exiting the condenser; determining a working fluid
sub-cooling value based on the measured temperature and the
measured pressure; and comparing said determined working fluid
sub-cooling with a target sub-cooling to determine if a charge of
working fluid should be added to said system or recovered from said
system.
9. The method of claim 8, further comprising: adding working fluid
to the system in response to a result of the comparing the
determined working fluid sub-cooling with the target
sub-cooling.
10. The method of claim 9, wherein the working fluid is added into
the system through a flow restriction device.
11. The method of claim 8, further comprising: evacuating working
fluid from the system in response to a result of the comparing the
determined working fluid sub-cooling with the target
sub-cooling.
12. The method of claim 11, wherein the working fluid is evacuated
from the system through a flow restriction device.
13. A method of correcting a working fluid charge of an air
conditioning system, comprising: measuring each of a pressure and a
temperature of a working fluid as the working fluid exits a
condenser of the system; calculating one of an actual sub-cooling
of the working fluid or a pressure representation thereof;
calculating a charge error by comparing either the actual
sub-cooling of the working fluid or the pressure representation
thereof to a target sub-cooling; and adjusting an amount of working
fluid within the system in response to the calculated charge
error.
14. The method of claim 13, further comprising: removing a portion
of the working fluid from the system if the charge error indicates
excessive sub-cooling.
15. The method of claim 13, further comprising: adding working
fluid to the system if the charge error indicates insufficient
sub-cooling.
16. The method of claim 13, wherein working fluid is passed through
a flow restriction device during the adjusting the amount of
working fluid within the system.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This is a divisional application of the prior filed and
co-pending U.S. patent application Ser. No. 11/486,874 filed Jul.
14, 2006 and entitled "System And Method For Controlling Working
Fluid Charge In A Vapor Compression Air Conditioning System" which
is incorporated herein by reference for all purposes.
BACKGROUND OF THE INVENTION
[0002] Vapor compression refrigeration, air conditioning and
heating (heat pump) systems have long been plagued with less than
optimum operating efficiencies due to an inadequate or excessive
working fluid charge within the system. Vapor compression air
conditioning and heat pumps systems, for example, typically are
designed to operate with a working fluid charge which provides a
small amount of sub-cooling of the working fluid in its condensed
state. However, initial installation, servicing and repair
operations are difficult to carry out with respect to providing a
proper fluid charge within the system. For example, when removing
fluid or adding fluid to the system, there is often inadequate
control of flow of the fluid (refrigerant) resulting in an
excessive charge of fluid to a system or a system which is
undercharged. Historically, it has been necessary to add or
subtract fluid and operate the system to "wait and see" if the
system comes into a balanced condition or achieves the desired
amount of sub-cooling of the fluid in its condensed state. However,
the present invention overcomes the inaccuracies and excessive
delays in providing properly charged vapor compression air
conditioning systems, in particular.
SUMMARY OF THE INVENTION
[0003] The present invention provides a vapor compression air
conditioning (heating, cooling or both heating and cooling) or
refrigeration system adapted for optimum operating efficiency with
respect to the proper quantity or charge of working fluid disposed
in the system. The present invention also provides a method,
particularly, for adding working fluid to a vapor compression-type
air conditioning or refrigeration system. However, a method of
extracting fluid is also contemplated.
[0004] In accordance with one aspect of the present invention, a
vapor compression air conditioning or refrigeration system is
adapted for connection to a fluid adding or fluid extracting unit
which may include at least one reservoir of working fluid and one
or more conduits for connection to fluid conduits associated with
the working fluid compressor of the air conditioning system. A
fluid flow restrictor device may be provided in one or more
conduits adapted to be connected to the so-called low pressure side
of a compressor as well as the high pressure side for adding fluid
to or removing fluid from the system circuit, respectively. The
flow restrictor device may be adapted for throttling fluid flow in
one direction while providing for substantially unrestricted flow
of fluid in an opposite direction. The flow restrictor devices may
be connected to a portable fluid adding and fluid extracting unit
or the devices may be permanently connected to the working fluid
conduits associated with or connected to the compressor of a vapor
compression air conditioning or refrigeration system.
[0005] In accordance with another aspect of the present invention,
a vapor compression-type air conditioning system or refrigeration
system is adapted to include a control circuit or controller and
associated instrumentation which monitors the operating condition
of the system during a working fluid charge adding or extracting
process to calculate actual sub-cooling of the working fluid as it
leaves a condenser unit of the system. The controller is operable
to provide a suitable output signal indicating the need to remove
additional fluid, add additional fluid or indicate no action
needed. Still further, the controller may be adapted to
automatically shutoff the flow of working fluid to the system when
an optimum operating or selected operating condition is
reached.
[0006] In accordance with yet a further aspect of the present
invention, an improved method is provided for adding working fluid
to or subtracting working fluid from a vapor compression air
conditioning or refrigeration system which achieves an optimum
fluid charge, or at least a fluid charge providing a selected
amount of sub-cooling of the working fluid flowing in the
system.
[0007] Those skilled in the art will further appreciate the
above-mentioned advantages and superior features of the invention
as well as other important aspects thereof upon reading the
detailed description which follows in conjunction with the
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a schematic diagram of a vapor compression air
conditioning system including a working fluid charge adding and
evacuating unit and a controller in accordance with the
invention;
[0009] FIG. 2 is a longitudinal central section view of one
preferred embodiment of a flow restrictor device in accordance with
the invention and for use with the system of the invention;
[0010] FIG. 3 is a detail section view taken generally along the
line 3-3 of FIG. 2;
[0011] FIG. 4 is a flow diagram illustrating at least the major
steps in a process for adding or subtracting working fluid with
respect to a vapor compression air conditioning or refrigeration
system in accordance with the invention; and
[0012] FIG. 5 is a schematic diagram of an alternate embodiment of
a system in accordance with the invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0013] In the description which follows like elements are marked
throughout the specification and drawings with the same reference
numerals, respectively. The drawing figures are not necessarily to
scale and certain features may be shown in generalized or schematic
form in the interest of clarity and conciseness.
[0014] Referring to FIG. 1, there is illustrated a schematic
diagram of a vapor compression-type air conditioning system which
may also be configured as a refrigeration system, and generally
designated by the numeral 10. The system 10 includes respective
heat exchangers 12 and 14 operably interconnected by a compressor
16. For the sake of discussion, the system 10 may be considered to
be an air conditioning (cooling) system although it will be
understood by those skilled in the art that the invention may be
used in connection with a so called heat pump system, both
reversible and nonreversible and the invention may also be used in
connection with a refrigeration system used for purposes other than
conditioning ambient air for human comfort or the like.
[0015] The compressor 16 is connected to heat exchanger 14 acting
as a condenser by way of a high pressure discharge conduit 18 and
condenser 14 is connected to heat exchanger 12, acting as an
evaporator unit, by way of a further high pressure conduit 20 and
an expansion device 22. Typically, the heat exchanger 12, expansion
device 22 and a portion of a conduit 24 interconnecting the
compressor 16 with the heat exchanger 12 are located within the
interior of a structure being cooled. A system controller 26 is
operably connected to certain components including an indoor fan or
blower, not shown, and a second portion 28 of the controller is
provided for controlling on and off operation of compressor 16 and
for controlling flow of air over heat exchanger 14 by way of a
motor driven fan 30. A heat exchange medium other than forced air
may be used to control heat exchange by one or both of the heat
exchangers 12 and 14. When used as an air conditioning or heat pump
system, the system 10 also includes a thermostat 32 connected to
controller units 26 and 28. Controller unit 26 is also connected to
a source of electrical power via conductor means 36 and for
communicating such power to controller unit 28.
[0016] Conduit 24 is considered a so-called low pressure conduit
leading to compressor 16 for delivering working fluid thereto for
compression to a higher pressure. Conduit 24 includes a suitable
releasable connector 25a associated therewith disposed in proximity
to the compressor 16 and including a one way poppet valve 25c, or
so-called Schrader valve known in the art, for conducting
refrigerant fluid to or from the system 10, which fluid may be one
of several types known to those skilled in the art and used as the
working fluid in vapor compression systems. A second releasable
connector 27a is connected to high pressure conduit or so called
liquid line 20, but may be connected to conduit 18, alternatively.
Connector 27a includes a Schrader valve 27c. Conduit 18 is
connected to the so-called high pressure side of compressor 16 for
conducting heated vapor to heat exchanger 14 for at least partial
condensation therein and then discharge to conduit 20.
[0017] Accordingly, working fluid flowing out of the heat exchanger
14 through conduit 20 to expansion device 22 is typically in liquid
form and the pressure and temperature of such fluid may be sensed
by respective temperature and pressure sensors 40 and 42, as shown
in FIG. 1. Sensors 40 and 42 may include direct readout displays or
gauges 40a and 42a and are operatively connected to a further
controller unit or circuit 44 which may be operably connected to
the controller unit 28 to receive power therefrom and deliver
certain control signals thereto. Controller 44 may be a suitable
programmable microcontroller or an application specific integrated
circuit previously programmed for operation in accordance with the
invention. Controller 44 includes a part 45 including visual
indicators 46 and 48 for indicating the status of a refrigerant or
working fluid charge in the system 10. A visual display 48a may
also be provided for displaying information to a user. The
controller part 45 is also adapted to provide an electric output
signal to conductor means 50 which may be releasably connected to
the controller part 45 at a plug or connector 52.
[0018] Referring further to FIG. 1, a working fluid adding and
evacuation or subtracting apparatus is illustrated and generally
designated by the numeral 54. The apparatus 54 includes a pressure
vessel and reservoir 56 for new working fluid, such as one of the
common refrigerant fluids previously mentioned. A conduit 58 is
connected to reservoir 56 and to a motor operated or solenoid type
valve 60 connected to conductor means 50 and to the controller part
45 via the connector 52. Conduits 62, 64 and 66 are operable to be
in communication with the reservoir 56 by way of the valve 60.
Suitable manual or remotely controllable valves 63, 65 and 67 may
be arranged as illustrated for controlling the flow of working
fluid between the new fluid reservoir 56, a fluid recovery
reservoir 70 and connector parts 25b and 27b which are operable to
connect the apparatus 54 to the conduit 24 and the conduit 20,
respectively. Connector parts 25a and 27a are associated with
Schrader valves 25c and 27c operably connected to the respective
conduits 24 and 20, as illustrated and previously described. When
connectors 25a and 25b are engaged, valve 25c is open and when
connectors 27a and 27b are engaged, valve 27c is open.
[0019] Referring to FIGS. 2 and 3, a flow restrictor 72 is shown in
one preferred and exemplary embodiment and is characterized by a
housing 74 having suitable ports 76 and 78 opening to opposed
housing end faces 77 and 79, respectively. An enlarged, internal,
longitudinal passage 80 is provided in housing 74 in communication
with ports 76 and 78. Suitable guide bosses 82 are opposed to each
other, as illustrated in FIGS. 2 and 3, for journaling a flow
restrictor element in the form of a somewhat bullet-shaped movable
plug or closure member 84 slidably disposed in passage 80 and
operable to engage a seat 86 formed in housing 74 adjacent port 78.
Plug or closure member 84 is also operable to engage internal stops
88 opposed to each other and aligned with the guide bosses 82 when
the closure member moves in a direction toward the port 76. Housing
74 would normally be fabricated in two or more parts to enable
insertion and removal of plug 84. A conical or tapered wall 90
remains spaced from the closure plug 84 when the plug engages the
stops 88 to provide a substantially unrestricted flow path from
port 78 to port 76. However, when the closure member 84 engages
seat 86, flow from port 76 to port 78 is restricted and must flow
through a reduced diameter passage 85 formed in the closure member
84, as shown. Alternatively, fixed orifice type flow restrictors or
capillary (small diameter) tubes could be used in place of devices
72 for restricting fluid flow.
[0020] As previously mentioned, flow restrictor devices 72 may be
interposed in conduits 62 and 66, as illustrated or mounted on and
connected to conduits 24 and 20. One preferred arrangement for the
devices 72 is to be interposed in the conduits 62 and 66, as
indicated in FIG. 1, wherein when the conduit 62 is connected to
the conduit 24 via connector parts 25a and 25b and Schrader valve
25c, flow of working fluid into conduit 24 is restricted since the
closure member 84 will move to the position shown in FIG. 2 forcing
working fluid to flow through the restricted passage 85 from port
76 through port 78 into conduit 24. Typically, when adding fluid to
system 10 via conduit 62, valves 65 and 67 are closed and valves 60
and 63 are opened, see FIG. 1. However, if device 72 connected to
conduit 62 is arranged as shown in FIG. 1, or mounted permanently
on system 10 and oriented in the same direction, and it is desired
to evacuate fluid from the system by way of conduit 24, for
example, substantially unrestricted flow of fluid will occur since
the closure member 84 will move to the left, viewing FIG. 2,
allowing such unrestricted flow of fluid between ports 78 and port
76.
[0021] If it is desired to evacuate working fluid from the system
10 in the event of a fluid overcharge, conduit 66 may be connected
to conduit 20 via connector parts 27a and 27b and the arrangement
of the flow restrictor device 72 interposed in conduit 66 is such
as to provide restricted flow of fluid from conduit 20 to conduit
66 so that control of evacuation of working fluid from the system
10 may be more closely maintained than if there was substantially
no restriction to flow of fluid from conduit 20 to conduit 66. When
evacuating fluid, valve 67 is opened, valve 65 or valves 60 and 63
are closed, and fluid flows from conduit 66 through valve 67 and
conduit 69 to recovery reservoir 70. Accordingly, the flow
restrictor devices 72 may be arranged as illustrated in FIG. 1 or
may be mounted directly on the conduits 20 and 24 in the
orientation shown and described for a permanent installation in the
system 10. Moreover, the arrangements of the flow restrictor
devices 72 may be reversed if desired to provide flow restriction
in one direction of flow and substantially unrestricted flow in the
opposite direction.
[0022] Accordingly, the devices 72, whether mounted permanently on
system 10 in communication with the conduits 24 and 20, or mounted
on a fluid charge adding and evacuation apparatus, such as the
apparatus 54, assist in providing an improved method for adjusting
the charge of working fluid in a vapor compression system, such as
the system 10 or an equivalent. Thanks to the provision of the
programmable controller unit 44, including part 45, a process may
be carried out for adding a charge of working fluid to the system
10 or evacuating a portion of the charge of working fluid from the
system 10 to provide the desired degree of sub-cooling of the fluid
as it exits a heat exchanger, such as the condenser 14. By
monitoring the temperature and pressure of the fluid flowing
through the conduit 20, for example, restricted flow of fluid into
or out of the system allows for adjusting a steady state operating
condition and the desired degree of sub-cooling of the fluid.
[0023] In accordance with a preferred process of the present
invention, the controller unit 44, 45 is operable to monitor the
addition or subtraction of working fluid with respect to the system
10 by causing the controller to enter the so-called charging mode
at step 100, see FIG. 4. At step 102 the controller 44, 45 and
system 10 are caused to become ready to check the charge condition
by querying whether or not the system has been running more than a
preset period of time, such as "y" minutes indicated at step 104.
If the system 10 has been running less than a preset period of time
and the variance of sub-cooling of the fluid, as measured by the
sensors 40 and 42, is less than a "z" predetermined amount for "x"
predetermined period of time, as measured at step 106, or if the
run time at step 104 is greater than the preset period of time, the
process proceeds to step 108. If steps 104 and 106 are both
"false", the process repeats itself as indicated by step 110 and a
signal may be provided to the user indicating time to complete the
process.
[0024] At step 108, controller unit 44, 45 reads the fluid pressure
and temperature and calculates the actual fluid sub-cooling or a
pressure representation thereof. The process proceeds to step 112
to determine if the actual sub-cooling of the working fluid is
greater than or less than a so-called target sub-cooling condition
and a charge error is calculated at step 114. If the charge error
indicates excessive sub-cooling at step 116, a suitable indicator
is illuminated, such as one of the indicators 46 or 48, or a
message is provided at visual display 48a, indicating the need to
reduce the charge of working fluid in the system 10, as indicated
at step 118. Such may be carried out by pumping fluid or allowing
the bleeding of fluid through device 72 connected to conduit 66 for
recovery into the reservoir 70. Thanks to the restriction of fluid
flow through the device 72 connected to conduit 66 the rate of
change of sub-cooling can be closely monitored. In fact, as the
process continues to monitor removal of fluid until the total
charge is correct at step 120 and the process repeats itself, the
controller 44 may generate a suitable control signal or a visual or
audible signal.
[0025] However, if it is determined at step 116 that recovery or
evacuation of working fluid from system 10 is not required but
addition of fluid is required, such as indicated at step 122,
controller unit 44 may energize valve 60, FIG. 1, for example,
causing same to open and to allow fluid to flow from pressure
vessel or reservoir 56 through conduit 62 and device 72 at a
restricted flow rate to add working fluid to system 10 via valve
25c and conduit 24 until the total fluid charge is correct, as
measured by the amount of sub-cooling at sensors 40 and 42 and
monitored by controller 44, 45. Steps 124 and 126 reflect this
process.
[0026] If no addition of working fluid is required at step 122, a
suitable indicator is illuminated, such as indicator 46, or a
message is displayed at display 48a at step 128 advising the
operator or user to cease adding fluid to or removing fluid from
the system 10, as indicated at step 130. The process is then
completed as indicated at step 132. Operation of the valves 63, 65
and 67 to allow flow of fluid between reservoirs 56 and 70 and the
system 10, as required by the process described above, is believed
to be within the purview of one skilled in the art.
[0027] Referring briefly to FIG. 5, a system 10a, illustrated
schematically, is substantially like that shown and described with
regard to FIG. 1 with the exception that the devices 72 are
essentially permanently mounted to the system in communication with
the conduits 24 and 20 in the manner illustrated whereby restricted
flow of fluid into the system 10a is provided by the device 72
connected to conduit 24 but substantially unrestricted flow out of
the system may be provided when the connector 25a is connected to a
modified charge addition or evacuation apparatus 54a, for example.
In like manner restricted flow of fluid out of the system 10a may
be provided by the so-called permanent connection between a device
72 and conduit 20 for purposes of fluid evacuating at a controlled
or restricted rate from the system if an overcharge, and consequent
excessive sub-cooling, is occurring.
[0028] In the arrangement of FIG. 5, a charge addition and
subtraction apparatus 54a may be connected to either connector 25a
or 27a and the aforementioned check valves or so-called Schrader
valves 25c and 27c may be interposed the respective connectors 25a
and 27a and the devices 72, as shown in FIG. 5. The valves 25c and
27c are, of course, held open by the connectors 25a, 25b and 27a,
27b when such are engaged in a known manner. In all other respects
the system 10a and the charge addition or evacuation apparatus 54a
are substantially like the system 10 and apparatus 54.
[0029] Accordingly, in accordance with the systems and process
described above, vapor compression air conditioning and
refrigeration systems may be properly charged with working fluid to
prevent flooding of the compressor, provide a faster method of
charging and greater accuracy of obtaining the proper charge of
working fluid in a system of the types described. Although
preferred embodiments of a system and method have been disclosed in
detail herein, those skilled in the art will appreciate that
various substitutions and modifications may be made without
departing from the scope and spirit of the appended claims.
* * * * *