U.S. patent application number 10/827018 was filed with the patent office on 2005-10-20 for compression cooling system and method for evaluating operation thereof.
Invention is credited to Hrejsa, Peter Brian, Olsen, Mark William.
Application Number | 20050229612 10/827018 |
Document ID | / |
Family ID | 35094846 |
Filed Date | 2005-10-20 |
United States Patent
Application |
20050229612 |
Kind Code |
A1 |
Hrejsa, Peter Brian ; et
al. |
October 20, 2005 |
Compression cooling system and method for evaluating operation
thereof
Abstract
A method for evaluating operation of a compression cooling
system includes the steps of: (a) in no particular order: (1)
measuring a first temperature of the refrigerant in a saturated
state; and (2) measuring a second temperature of the refrigerant in
a liquid state; and (b) calculating a difference between the first
temperature and the second temperature to determine the extant
amount of subcooling to which the refrigerant is subjected.
Inventors: |
Hrejsa, Peter Brian; (The
Colony, TX) ; Olsen, Mark William; (Carrollton,
TX) |
Correspondence
Address: |
LAW OFFICE OF DONALD D. MONDUL
6631 LOVINGTON DRIVE
DALLAS
TX
75252
US
|
Family ID: |
35094846 |
Appl. No.: |
10/827018 |
Filed: |
April 19, 2004 |
Current U.S.
Class: |
62/149 |
Current CPC
Class: |
F25B 2500/19 20130101;
F25B 2700/21163 20130101; F25B 49/005 20130101; F25B 2600/07
20130101; F25B 45/00 20130101; F25B 2700/2116 20130101 |
Class at
Publication: |
062/149 |
International
Class: |
F25B 045/00; F25D
017/02 |
Claims
I claim:
1. A method for evaluating operation of a compression cooling
system; the method comprising the steps of: (a) in no particular
order: (1) measuring a first temperature of said refrigerant in a
saturated state; and (2) measuring a second temperature of said
refrigerant in a liquid state; and (b) calculating a difference
between said first temperature and said second temperature to
determine the extant amount of subcooling to which said refrigerant
is subjected.
2. A method for evaluating operation of a compression cooling
system as recited in claim 1 wherein the method comprises the
further step of: (c) comparing said extant amount of subcooling
with a predetermined acceptable amount of subcooling.
3. A method for evaluating operation of a compression cooling
system as recited in claim 2 wherein the method comprises the
further step of: (d) changing amount of refrigerant in said cooling
system when said extant amount of subcooling differs from said
predetermined acceptable amount of subcooling by greater than a
predetermined amount.
4. A method for evaluating operation of a compression cooling
system as recited in claim 1 wherein the method comprises the
further step of: (c) adding refrigerant to said cooling system when
said extant amount of subcooling is less than a predetermined
acceptable amount of subcooling.
5. A method for evaluating operation of a compression cooling
system as recited in claim 3 wherein the method comprises the
further step of: (e) repeating steps (a) through (d) until said
extant amount of subcooling differs from said predetermined
acceptable amount of subcooling by less than said predetermined
amount.
6. A method for evaluating operation of a compression cooling
system as recited in claim 4 wherein the method comprises the
further step of: (d) repeating steps (a) through (c) until said
extant amount of subcooling differs from said predetermined
acceptable amount of subcooling by less than a predetermined
amount.
7. A method for evaluating refrigerant charge in a compression
cooling system; said system including a first system portion in
which said refrigerant is substantially always in a saturated state
and a second system portion in which said refrigerant is
substantially always in a liquid state; the method comprising the
steps of: (a) in no particular order: (1) measuring a first
temperature of said refrigerant in said first system portion; and
(2) measuring a second temperature of said refrigerant in said
second system portion; (b) calculating a difference between said
first temperature and said second temperature to determine the
extant amount of subcooling effected by said system.
8. A method for evaluating refrigerant charge in a compression
cooling system as recited in claim 7 wherein the method comprises
the further step of: (c) comparing said extant amount of subcooling
with a predetermined acceptable amount of subcooling.
9. A method for evaluating refrigerant charge in a compression
cooling system as recited in claim 8 wherein the method comprises
the further step of: (d) changing amount of refrigerant in said
cooling system when said extant amount of subcooling differs from
said predetermined acceptable amount of subcooling by greater than
a predetermined amount.
10. A method for evaluating refrigerant charge in a compression
cooling system as recited in claim 7 wherein the method comprises
the further step of: (c) adding refrigerant to said system when
said extant amount of subcooling differs from said predetermined
acceptable amount of subcooling by less than a predetermined
amount.
11. A method for evaluating refrigerant charge in a compression
cooling system as recited in claim 9 wherein the method comprises
the further step of: (e) repeating steps (a) through (d) until said
extant amount of subcooling differs from said predetermined
acceptable amount of subcooling by less than said predetermined
amount.
12. A method for evaluating refrigerant charge in a compression
cooling system as recited in claim 10 wherein the method comprises
the further step of: (d) repeating steps (a) through (c) until said
extant amount of subcooling differs from said predetermined
acceptable amount of subcooling by less than a predetermined
amount.
13. A compression cooling system comprising: (a) a compressor, an
evaporator and a condenser fluidly coupled by at least one fluid
carrying line containing a refrigerant; (b) a first temperature
measuring device connected with said system for measuring a first
temperature of said refrigerant in a saturated state; and (c) a
second temperature measuring device connected with said system for
measuring a second temperature of said refrigerant in a liquid
state.
14. A compression cooling system as recited in claim 13 wherein the
system further comprises: (d) a calculating device coupled with
said first temperature measuring device and said second temperature
measuring device; said calculating device calculating a difference
between said first temperature and said second temperature to
determine an extant amount of subcooling effected by said
system.
15. A compression cooling system as recited in claim 14 wherein the
system further comprises: (e) fluid access fittings in said fluid
carrying line for effecting fluid communication with the system
from without the system; said fluid access fittings being
configured to accommodate a user coupling a refrigerant source with
said fittings for changing charge of said refrigerant within said
system when said extant amount of subcooling differs from a
predetermined acceptable amount of subcooling by greater than a
predetermined amount.
16. A compression cooling system as recited in claim 15 wherein
said predetermined acceptable amount of subcooling is provided to
said user by a tool; said tool being external of said system.
17. A compression cooling system as recited in claim 15 wherein
said predetermined acceptable amount of subcooling is provided to
said user by said calculating device.
18. A compression cooling system as recited in claim 13 wherein the
system further comprises: (e) fluid access fittings in said at
least one fluid carrying line for effecting fluid communication
with the system from without the system; said fluid access fittings
being configured to accommodate a user coupling a refrigerant
source with said fittings for changing charge of said refrigerant
within said system when said extant amount of subcooling differs
from a predetermined acceptable amount of subcooling by greater
than a predetermined amount.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention is directed to compression
conditioning systems, and especially to a vapor compression
conditioning system, such as a heat pump or air conditioner, that
does not require breaching the system to evaluate operation of the
system, such as for evaluating state of charge of refrigerant in
the system.
[0002] Proper charge of refrigerant is a crucial requirement for
maintaining efficient operation of a compression cooling system.
Servicemen visit cooling systems on-site in order to check
refrigerant level and to refill or recharge systems that are found
to have a low refrigerant charge. Typical measurements performed by
a service representative in checking a system involve hauling
heavy, unwieldy pressure gauges to the condenser unit of the system
(usually located outside the cooled premises, such as on a roof or
in a yard). The pressure gauges are hooked up to the refrigerant
line of the cooling system so that pressure in the refrigerant
fluid line may be measured. This connection of pressure gauges
necessarily involves breaching the cooling system, which involves a
risk that the sealed nature of the system may be compromised and
refrigerant may be lost to the atmosphere. The serviceman also
measures temperature of the refrigerant in its liquid state. Then a
table or other reference is consulted by the serviceman using his
pressure and temperature measurements to determine the amount of
refrigerant needed to configure the cooling system for efficient
operation.
[0003] It would be useful for the serviceman to be able to more
straightforwardly check condition of the cooling system without
having to breach the system and risk losing refrigerant.
[0004] If checking of the refrigerant level could be carried out
automatically, then results of such testing could be employed to
make decisions regarding whether to recharge the system. The actual
recharging could be initiated in response to a command entered from
a location remote from the system or from a control or calculating
device co-located with the system.
[0005] It would be useful for checking of the condition of the
cooling system to be conducted automatically with a capability to
replenish refrigerant when a need for replenishment is
indicated.
[0006] It would also be useful for checking of the condition of the
cooling system to be conducted from a location remote from the
cooling system.
[0007] Attempts have been made to simplify checking charge of
refrigerant in cooling systems. U.S. Pat. No. 6,308,523 to Scaringe
for "Simplified Subcooling or Superheated Indicator and Method for
Air Conditioning and Other Refrigeration Systems", issued Oct. 30,
2001 (hereinafter referred to as "Scaringe"), discloses an
indicator that can be attached to a pipe at an appropriate location
in a cooling system. The indicator uses temperature-indicating
crystals or a thermometer to show the superheat or subcooling of
the system without requiring saturation curves or tables. The
indicator can be scaled between a selected maximum and minimum
pressure and laid out so that the corresponding saturation
temperature for respective pressure intervals is indicated by the
temperature-indicating crystals or thermometer. Scaringe proposes
measuring evaporator exit air temperature or condenser inlet air
temperature to approximate saturation temperature in the evaporator
or the condenser. In any event, Scaringe requires arranging
temperature indicating devices to represent a scale of the
saturation temperatures of pressures within a predetermined maximum
and minimum pressure.
[0008] U.S. patent application Publication US2003/0182958 by Mei at
al. for "Non-Intrusive Refrigerant Charge Indicator", published
Oct. 2, 2003 (hereinafter referred to as "Mei"), discloses
measuring temperature at an outside surface of a two-phase
refrigerant line section, and using complicated third-order
calculations, tables or charts to convert the measured temperature
to a refrigerant pressure within the line section.
[0009] Neither Scaringe nor Mei have much reduced the complexity
involved in evaluating operation of a compression cooling system.
Nor do either Scaringe or Mei, individually or in any combination,
contribute to remote automatic control and recharging of a cooling
system.
[0010] There is a need for a compression cooling system and method
for evaluating operation thereof that permits a serviceman to
straightforwardly check the condition of the cooling system without
having to breach the system and risk losing refrigerant.
[0011] There is also a need for a compression cooling system and
method for evaluating operation thereof that permits checking of
condition of the cooling system to be conducted automatically with
a capability to replenish refrigerant when a need for replenishment
is indicated.
[0012] There is also a need for a compression cooling system and
method for evaluating operation thereof that permits checking of
condition of the cooling system to be conducted from a location
remote from the cooling system.
SUMMARY OF THE INVENTION
[0013] A method for evaluating operation of a compression cooling
system includes the steps of: (a) in no particular order: (1)
measuring a first temperature of the refrigerant in a saturated
state; and (2) measuring a second temperature of the refrigerant in
a liquid state; and (b) calculating a difference between the first
temperature and the second temperature to determine the extant
amount of subcooling to which the refrigerant is subjected.
[0014] A compression cooling system includes: (a) a compressor, an
evaporator and a condenser fluidly coupled by a fluid carrying line
containing a refrigerant; (b) a first temperature measuring device
connected with the system for measuring a first temperature of the
refrigerant in a saturated state; and (c) a second temperature
measuring device connected with the system for measuring a second
temperature of the refrigerant in a liquid state.
[0015] It is therefore an object of the present invention to
provide a compression cooling system and method for evaluating
operation thereof that permits a serviceman to straightforwardly
check the condition of the cooling system without having to breach
the system and risk losing refrigerant.
[0016] It is a further object of the present invention to provide a
compression cooling system and method for evaluating operation
thereof that permits checking of condition of the cooling system to
be conducted automatically with a capability to replenish
refrigerant when a need for replenishment is indicated.
[0017] It is yet a further object of the present invention to
provide a compression cooling system and method for evaluating
operation thereof that permits checking of condition of the cooling
system to be conducted from a location remote from the cooling
system.
[0018] Further objects and features of the present invention will
be apparent from the following specification and claims when
considered in connection with the accompanying drawings, in which
like elements are labeled using like reference numerals in the
various figures, illustrating the preferred embodiments of the
invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is a schematic diagram illustrating a compression
cooling system configured according to the present invention.
[0020] FIG. 2 is a flow diagram illustrating the method of the
present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0021] FIG. 1 is a schematic diagram illustrating a compression
cooling system configured according to the present invention. In
FIG. 1, a cooling system 10 includes a compressor 12, an evaporator
14 and a condenser 16. A fluid line 18 fluidly couples evaporator
14 with compressor 12. A fluid line 20 fluidly couples compressor
12 with condenser 16. A fluid line 22 fluidly couples condenser 16
with an expansion valve 24. A fluid line 26 fluidly couples
expansion valve 24 with evaporator 14. By "fluidly couples" it is
meant that fluid flows substantially freely within fluid lines 18,
20, 22, 26 to transport refrigerant (not shown separately in FIG.
1) among evaporator 14, condenser 112, condenser 16 and expansion
valve 24. A blower fan 28 draws air across evaporator 14 generally
in the direction indicated by arrow 30. A blower fan 32 draws air
across condenser 16 generally in the direction indicated by arrow
34.
[0022] A building wall 40 bounds a building interior space 42 that
is cooled by cooling system 10. Preferably, evaporator 14 and
blower fan 28 are situated within building interior space 42.
Expansion valve 24 may also be situated within building interior
space 42, if desired.
[0023] A control unit 44 is configured to include a calculating
device (not shown in detail in FIG. 1) and is coupled to a
thermostat 46 located in building interior space 42. Other
monitoring capabilities may also be carried out by control unit 44,
such as monitoring temperature or air flow near blower fan 32, as
indicated by a monitoring line 48.
[0024] Refrigerant is provided to compressor 12 at a compressor
intake 50. Compressed refrigerant is output or exhausted by
compressor 12 at a compressor exhaust 52. Compressed refrigerant
proceeds from compressor exhaust 52 to condenser intake 54.
Refrigerant condenses within condenser 16 to a saturated condition
within condenser 16 and is further subcooled below saturation
condition of the refrigerant. Refrigerant is exhausted from
condenser 196 at a condenser exhaust 56 in a liquid state and
traverses fluid line 22 to expansion valve 24. Refrigerant leaves
expansion valve 24 via fluid line 26 and enters evaporator 14.
Blower fan 28 draws cold air from about an evaporator coil 15 in
evaporator 14 to provide cool air to building interior space 42.
Refrigerant is exhausted from evaporator 14 via fluid line 18 to
return to compressor intake 50.
[0025] When cooling system 10 is properly charged with refrigerant,
refrigerant arriving at condenser intake 54 is 100% in a vapor
state. Condenser 16 includes a condenser coil 17 that presents a
plurality of fluid line loops for refrigerant to traverse en route
to condenser exhaust 56. As refrigerant traverses condenser coil 17
from condenser intake 54 to condenser exhaust 56, refrigerant
condenses and becomes saturated. Depending upon the amount of
refrigerant present (i.e., the refrigerant charge) in cooling
system 10, refrigerant may condense from 100% vapor (at condenser
intake 54) and desuperheat to begin condensing somewhere in the
region of locus 55 in condenser coil 17. The term "superheat"
refers to warming of a refrigerant to a temperature above
saturation temperature T.sub.SATURATION. To desuperheat is to cool
to a temperature less than or equal to saturation temperature
T.sub.SATURATION.
[0026] The amount of charge in cooling system 10 may vary the locus
at which condensation occurs in condenser coil 17 toward condenser
intake 54 or toward condenser exhaust 56. Refrigerant leaving
condenser 16 at condenser exhaust 56 is 100% in a liquid state, and
is at a temperature lower than temperature of saturated refrigerant
in the interior coils of condenser coil 17. That is, at a locus in
condenser coil 17 proximal to condenser exhaust 56 (e.g., locus
57), refrigerant traversing condenser coil 17 begins subcooling
(i.e., cooling to a temperature below the temperature of saturated
refrigerant in the interior of condenser coil 17). The amount of
charge in cooling system 10 may vary the locus at which subcooling
begins toward condenser intake 54 or toward condenser exhaust 56.
The point to note here is that there is an interior portion of
condenser coil 17 in which refrigerant is always saturated. By way
of example and not by way of limitation, a saturation-assured
portion 58 of condenser coil 17 is established between loci 55,
57.
[0027] Installing a temperature sensing device 60 in
saturation-assured portion 58 assures that temperatures measured by
temperature sensing device 60 are indicating saturated temperature
(T.sub.SATURATED) of refrigerant within cooling system 10.
Installing a temperature sensing device 62 between condenser
exhaust 56 and expansion valve 24 assures that temperatures
measured by temperature sensing device 62 are indicating liquid
temperature (T.sub.LIQUID) of refrigerant within cooling system 10.
It is preferred that temperature sensing device 62 be placed as
close to condenser exhaust 56 as possible.
[0028] Subcooling is defined in a compression cooling system as the
difference between saturated temperature and liquid temperature of
refrigerant in the cooling system. That is,
SUBCOOLING=T.sub.SATURATED-T.sub.LIQUID [1]
[0029] As mentioned earlier herein, a serviceman nowadays measures
pressure in fluid lines in a cooling system and consults tables,
charts or similar references to determine saturation temperature
T.sub.SATURATED. In contrast, the present invention contemplates
using subcooling as the primary indicator by which a one may
evaluate operation of a compression cooling system, without
requiring any complex conversion, calculation or consulting of
references to determine another parameter for use in evaluating the
operation of the cooling system. Using the apparatus and method of
the present invention, one may read temperature from temperature
sensing devices 60, 62 and use expression [1] to simply and
straightforwardly ascertain the extant level of subcooling effected
by cooling system 10. If the extant level of subcooling is less
than a predetermined acceptable level of subcooling (provided, by
way of example and not by way of limitation, by a reference book,
posted on a cabinet containing cooling system 10, or stored in
control unit 44), then refrigerant may be introduced into a fluid
line 18, 20, 22, 26 while observing variance of saturation
temperature T.sub.SATURATION and liquid temperature T.sub.LIQUID.
Expression [1] may be employed to straightforwardly dynamically
monitor and control adding refrigerant to achieve a desired level
of subcooling that has been established as indicating a properly
operating cooling system.
[0030] Coupling temperature sensing devices 60, 62 to control unit
44, for example, provides a capability for automatically effecting
checks of subcooling. Control unit 44 may include a calculating
device and a memory storage (not shown in detail in FIG. 1) for
treating indications received from temperature sensing devices 60,
62 using expression [1], ascertaining whether the extant level of
subcooling thereby determined is at least equal with a
predetermined acceptable level of subcooling stored in memory in
control unit 44. If the extant level of subcooling indicates a need
for adding refrigerant, a control signal may be automatically sent
from control unit 44 to a valve control unit 70. Communication with
valve control unit 70 by control unit 44 may be carried out via a
wired connection or via wireless connection, as indicated at
connection locus 72. Valve control unit 70 responds to signals from
control unit 44 to open valve 74 so that refrigerant may flow from
a refrigerant reserve or reservoir 75 to fluid line 20 (other fluid
lines 18, 22, 24 may be used for refrigerant addition if
desired).
[0031] Control unit 44 may be co-located with cooling system 10.
Alternatively, control system 44 may be remotely co-located from
cooling system 10 (not shown in FIG. 1). In yet another alternate
configuration, control unit 44 may be co-located with cooling
system 10 but may be communication with a remote station (not shown
in FIG. 1) and respond to commands from the remote station.
Communication among control unit 44, valve control unit 70 and a
remote location (if provided) may be carried out via a wired
connection or via wireless connection (as indicated at connection
locus 72). Evaluation of operation of cooling system 10 may be
carried out from the remote location. Refrigerant may be added on
command from the remote location if desired. Alternatively, cooling
system 10 may be configured to permit return of refrigerant to
reservoir 75 when control unit 44 determines that subcooling has
cooled the refrigerant to too cool a temperature.
[0032] FIG. 2 is a flow diagram illustrating the method of the
present invention. In FIG. 2, a method 100 for evaluating operation
of a compression cooling system begins at a START locus 102. Method
100 continues with the step of, in no particular order, (1)
measuring a first temperature of the refrigerant in a saturated
state, as indicated by a block 104; and (2) measuring a second
temperature of the refrigerant in a liquid state, as indicated by a
block 106.
[0033] Method 100 continues with the step of calculating a
difference between the first temperature and the second temperature
to determine the extant amount of subcooling to which the
refrigerant is subjected, as indicated by a block 108.
[0034] Method 100 may continue with the step of posing a query
whether the extant amount of subcooling is less than a
predetermined acceptable amount of subcooling, as indicated by a
query block 110. If the extant amount of subcooling is less than
the predetermined acceptable amount of subcooling, method 100
continues via YES response line 112 and refrigerant is added to the
cooling system, as indicated by a block 114. Method 100 thereafter
returns to a locus 115 from which method 100 proceeds to carry out
method steps indicated by blocks 104, 106, 108, 110.
[0035] If the extant amount of subcooling is not less than the
predetermined acceptable amount of subcooling, method 100 continues
via NO response line 116 and method 100 terminates at an END locus
118.
[0036] It is to be understood that, while the detailed drawings and
specific examples given describe preferred embodiments of the
invention, they are for the purpose of illustration only, that the
apparatus and method of the invention are not limited to the
precise details and conditions disclosed and that various changes
may be made therein without departing from the spirit of the
invention which is defined by the following claims:
* * * * *