U.S. patent application number 11/460400 was filed with the patent office on 2008-02-14 for method and system for automatic capacity self-modulation in a comrpessor.
This patent application is currently assigned to BRISTOL COMPRESSORS, INC.. Invention is credited to Eugene K. Chumley, Scott G. Hix, Joseph F. Loprete, David T. Monk.
Application Number | 20080034772 11/460400 |
Document ID | / |
Family ID | 39049199 |
Filed Date | 2008-02-14 |
United States Patent
Application |
20080034772 |
Kind Code |
A1 |
Chumley; Eugene K. ; et
al. |
February 14, 2008 |
METHOD AND SYSTEM FOR AUTOMATIC CAPACITY SELF-MODULATION IN A
COMRPESSOR
Abstract
An automatic self-modulation capacity compressor for an
HVAC&R system is disclosed. The system includes a housing, a
compressor, a motor, and a pressure sensitive control valve. The
HVAC&R system further comprises an expander and a condenser. In
the open position, the control valve permits a portion of the
pressurized gasses from the compressor to escape, creating a
partial capacity compressor within the system. Once a predetermined
set point pressure differential is met, the control valve moves to
the closed position, where all of the pressurized gasses within the
compressor are provided to the system, thereby creating a full
capacity compressor. Once the compressor is operating in full
capacity, the compressor remains in full capacity mode until the
demands of the system are met and the compressor shuts down. Upon
restart, the compressor operates in partial capacity until the
predetermined set point pressure is met once again and the
compressor begins operating in full capacity.
Inventors: |
Chumley; Eugene K.;
(Abingdon, VA) ; Loprete; Joseph F.; (Bristol,
TN) ; Monk; David T.; (Bristol, VA) ; Hix;
Scott G.; (Bristol, VA) |
Correspondence
Address: |
MCNEES WALLACE & NURICK LLC
100 PINE STREET, P.O. BOX 1166
HARRISBURG
PA
17108-1166
US
|
Assignee: |
BRISTOL COMPRESSORS, INC.
Bristol
VA
|
Family ID: |
39049199 |
Appl. No.: |
11/460400 |
Filed: |
July 27, 2006 |
Current U.S.
Class: |
62/228.5 |
Current CPC
Class: |
F25B 2500/01 20130101;
F25B 2600/0261 20130101; F25B 2700/2104 20130101; F25B 2700/1931
20130101; F04B 49/035 20130101; F25B 2700/1933 20130101; F04B
39/121 20130101; F25B 49/022 20130101 |
Class at
Publication: |
62/228.5 |
International
Class: |
F25B 49/00 20060101
F25B049/00 |
Claims
1. A method for modulating capacity in a compressor for an
HVAC&R system comprising the steps of: providing a control
valve having a first position and a second position, the control
valve being configured and disposed to permit full compressor
capacity in response to the control valve being in the second
position and being configured to permit partial compressor capacity
in response to the control valve being in the first position;
positioning the control valve in the first position upon start up
of the compressor; operating the compressor at partial capacity in
response to the control valve being in the first position;
measuring a pressure differential in the compressor; comparing the
measured pressure differential to a predetermined pressure
differential set point; switching the control valve to the second
position to operate the compressor at full capacity in response to
the measured pressure differential being equal to or greater than
the predetermined pressure differential set point; and operating
the compressor at full capacity in response to the control valve
being in the second position until a shut down of the
compressor.
2. The method of claim 1 further comprising the steps of: selecting
a temperature set point for an enclosed space; measuring an actual
temperature of the enclosed space; comparing the actual temperature
and the temperature set point; and initiating operation of the
compressor in response to the temperature set point not being
satisfied.
3. The method of claim 2 further comprising the step of
deactivating the compressor in response to the actual temperature
satisfying the temperature set point.
4. The method of claim 3 wherein the HVAC&R system is operated
in a heating mode and the step of deactivating the compressor
includes shutting down the compressor when the actual temperature
is equal to or greater than the temperature set point.
5. The method of claim 3 wherein the HVAC&R system is operated
in a cooling mode and the step of deactivating the compressor
includes shutting down the compressor when the actual temperature
is less than or equal to the temperature set point.
6. The method of claim 1 wherein the step of positioning the
control valve includes positioning the control valve in an open
position and the step of switching the control valve to the second
position includes positioning the control valve in a closed
position.
7. The method of claim 1 wherein the step of providing a control
valve includes positioning the control valve in a closed position
and the step of switching the control valve to the second position
includes positioning the control valve in an open position.
8. The method of claim 1 wherein the step of switching the control
valve to the second position occurs substantially
instantaneously.
9. The method of claim 1 wherein the step of operating the
compressor at full capacity includes continuing to operate the
compressor at full capacity when the pressure differential is less
than the predetermined pressure differential set point.
10. A compressor for an HVAC&R system comprising: a housing,
the housing having an inlet and an outlet; a compression mechanism,
the compression mechanism being configured to receive uncompressed
fluid from the inlet at a first pressure and provide compressed
fluid to the outlet at a second pressure higher than the first
pressure; and a pressure control valve having a first position and
a second position, the pressure control valve being configured to
be in the first position on startup of the compressor, to switch to
the second position in response to the difference between the first
pressure and the second pressure being greater than a predetermined
pressure differential set point, and to remain at the second
position until the compressor shuts down.
11. The compressor of claim 10 wherein the first position of the
control valve is an open position and the second position of the
control valve is a closed position.
12. The compressor of claim 11 wherein the open position of the
control valve permits fluid to return to the inlet during operation
of the compressor and the closed position of the control valve
prevents fluid from returning to the inlet.
13. The compressor of claim 12 wherein the pressure control valve
upon being in the closed position is configured to remain in the
closed position when the pressure differential is less than the
predetermined pressure differential set point.
14. The compressor of claim 10 wherein the first position of the
control valve is a closed position and the second position of the
control valve is an open position.
15. The compressor of claim 10 wherein the pressure control valve
is in fluid communication with the inlet.
16. The compressor of claim 10 wherein the switch to the second
position occurs substantially instantaneously.
17. An HVAC&R system comprising: a compressor, a condenser and
an evaporator connected in a closed refrigeration loop; a
temperature control system, the temperature control system being
configured to receive a set point temperature and a corresponding
measured temperature for an enclosed space; the compressor being
configured to receive a fluid at an inlet at a first pressure and
discharge fluid at an outlet at a second pressure higher than the
first pressure, the compressor comprising: a pressure control valve
having a first predetermined position and a second predetermined
position; and the pressure control valve being configured to be in
the first position on startup of the compressor and to switch to
the second position in response to the difference between the first
pressure and the second pressure being greater than the
predetermined set point pressure, and to remain at the second
predetermined position until the compressor shuts down.
18. The system of claim 17 wherein the system is a cooling system
and begins operation in response to the measured temperature being
greater than the set point temperature and ends operation in
response to the measured temperature being less than or equal to
the set point temperature.
19. The system of claim 17 wherein the system is a heating system
and begins operation in response to the measured temperature being
less than the set point temperature and ends operation in response
to the measured temperature being equal to or greater than the set
point temperature.
20. The system of claim 17 wherein the first position is an open
position and the second position is a closed position.
21. The system of claim 20 wherein the open position permits fluid
to return to the inlet during operation of the compressor and the
closed position prevents fluid from returning to the inlet.
22. The system of claim 21 wherein the pressure control valve is
configured to transition from the open position to the closed
position substantially instantaneously.
23. The system of claim 17 wherein the first position is a closed
position and the second position is an open position.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates generally to providing
capacity modulation for compressors. More particularly, the present
invention relates to automatic capacity modulation in a compressor
without any need for external controls.
[0002] Frequently, compressors in heating, ventilation and air
conditioning (HVAC) systems are limited to a single output
capacity. One problem with the compressor being limited to a single
output capacity is that the compressor, especially reciprocating
compressors, can produce excess capacity at reduced outdoor ambient
temperatures. The excess capacity produced by the compressor
adversely affects any system incorporating the compressor during
SEER (Seasonal Energy Efficiency Rating) testing and in subsequent
operation of the system.
[0003] One attempt to solve the excess capacity problem in a
compressor is discussed in U.S. Pat. No. 6,663,358, wherein an
internal valve in the compressor is adjusted in response to
operating conditions to effect a change in the capacity of the
compressor. The output capacity of the compressor is controlled by
a valve and biasing member within the motor cavity that responds to
the pressure of the gasses. As the pressure builds in the
compressor in response to an increasing outdoor temperature, the
valve moves to the second position allowing the compressor to
operate at the second, higher, output capacity. Once the demand
subsides and the pressure drops, the valve then returns to the
first position and operates at the first capacity. While this
solution allows for the modulation of compressor capacity, the
toggle effect between the two operational capacities during
operation results in energy and efficiency losses and low
reliability of the system.
[0004] Therefore, what is needed is a cost-effective, efficient and
easily implemented system to provide for reduced compressor
capacity at reduced outdoor ambient temperatures, but that can also
provide full compressor capacity at higher outdoor ambient
temperatures.
SUMMARY OF THE INVENTION
[0005] A method for modulating capacity in a compressor for a
heating, ventilation, air conditioning and refrigeration
(HVAC&R) system includes providing a control valve having a
first position and a second position and configured and disposed to
permit full compressor capacity in response to the control valve
being in the second position and being configured to permit partial
compressor capacity in response to the control valve being in the
first position. The method also includes positioning the control
valve in the first position upon start up of the compressor,
operating the compressor at partial capacity in response to the
control valve being in the first position and measuring a pressure
differential in the compressor. In addition, the method includes
comparing the measured pressure differential to a predetermined
pressure differential set point switching the control valve to the
second position to operate the compressor at full capacity in
response to the measured pressure differential being equal to or
greater than the predetermined pressure differential set point and
operating the compressor at full capacity in response to the
control valve being in the second position until a shut down of the
compressor.
[0006] A compressor for an HVAC&R system includes a housing
having an inlet and an outlet, a compression mechanism being
configured to receive uncompressed fluid from the inlet at a first
pressure and provide compressed fluid to the outlet at a second
pressure higher than the first pressure and a pressure control
valve having a first position and a second position and being
configured to be in the first position on startup of the
compressor. The pressure control valve is also configured to switch
to the second position in response to the difference between the
first pressure and the second pressure being greater than a
predetermined pressure differential set point, and to remain at the
second position until the compressor shuts down.
[0007] An HVAC&R system includes a compressor, a condenser and
an evaporator connected in a closed refrigeration loop. The system
also includes a temperature control system configured to receive a
set point temperature and a corresponding measured temperature for
an enclosed space; and the compressor is configured to receive a
fluid at an inlet at a first pressure and discharge fluid at a
second pressure higher than the first pressure. In addition, the
compressor includes a pressure control valve having a first
predetermined position and a second predetermined position. The
pressure control valve is configured to be in the first position on
startup of the compressor and to switch to the second position in
response to the difference between the first pressure and the
second pressure being greater than the predetermined set point
pressure, and to remain at the second predetermined position until
the compressor shuts down.
[0008] One advantage of the present invention is increased system
performance, efficiency, and capacity control at reduced outdoor
temperatures in both heating and cooling modes of operation.
[0009] Still another advantage of the present invention is
increased reliability of the system.
[0010] Another advantage of the invention is that the system shuts
down once a user-selected set point temperature is satisfied,
thereby conserving energy.
[0011] Another advantage of the present invention is that the
capacity modulation is automatic without need for external
control.
[0012] A further advantage of the present invention is that the
self-modulation from partial to full capacity occurs almost
immediately, which allows the compressor to operate at partial
capacity until the need arises for full capacity, which conserves
energy and creates a more efficient compressor.
[0013] Accordingly, the present invention is directed to improved
compressors for providing automatic capacity modulation. Other
features and advantages of the present invention will be apparent
from the following more detailed description of the preferred
embodiment, taken in conjunction with the accompanying drawings
which illustrate, by way of example, the principles of the
invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIGS. 1 and 2 illustrate schematically a refrigeration
system that can be used with the present invention.
[0015] FIG. 3 illustrates a flow chart of one embodiment of the
capacity control process of the present invention.
[0016] FIG. 4 illustrates the control valve in the first
position.
[0017] FIG. 5 illustrates the control valve in the second
position.
[0018] Wherever possible, the same reference numbers will be used
throughout the drawings to refer to the same or like parts.
DETAILED DESCRIPTION OF THE INVENTION
[0019] As shown in FIGS. 1 and 2, a heating, ventilation, air
conditioning and refrigeration (HVAC&R) system 300 includes a
compressor 302, a condenser arrangement 304, and an evaporator
arrangement 306 (FIG. 1) or a compressor 302, a reversing valve
arrangement 350, an indoor unit 354 and an outdoor unit 352 (FIG.
2). The system 300 can be operated as an air conditioning only
system, where the evaporator arrangement 306 is preferably located
indoors, i.e., as and indoor unit 354, to provide cooling to the
indoor air and the condenser arrangement 304 is preferably located
outdoors, i.e., as an outdoor unit 352, to discharge heat to the
outdoor air. The system can also be operated as a heat pump system
with the inclusion of the reversing valve arrangement 350 to
control and direct the flow of refrigerant from the compressor 302.
When the heat pump is operated in an air conditioning mode, the
reversing valve arrangement 350 is controlled for refrigerant flow
as described above for an air conditioning system. However, when
the heat pump is operated in a heating mode, the flow of the
refrigerant is in the opposite direction from the air conditioning
mode, and the condenser arrangement 304 is preferably located
indoors, i.e., as an indoor unit 354, to provide heating of the
indoor air and the evaporator arrangement 306, i.e., as an outdoor
unit 352, is preferably located outdoors to absorb heat from the
outdoor air.
[0020] The compressor 302 compresses a refrigerant vapor and
delivers the vapor to the condenser 304 through a discharge line
(and the reversing valve arrangement 350 if operated as a heat
pump). The compressor 302 is preferably a reciprocating compressor.
However, it is to be understood that the compressor 302 can be any
suitable type of compressor, e.g., scroll compressor, rotary
compressor, screw compressor, swag link compressor, turbine
compressor, or any other suitable compressor. The refrigerant vapor
delivered by the compressor 302 to the condenser 304 enters into a
heat exchange relationship with a fluid, e.g., air or water, but
preferably air, and undergoes a phase change to a refrigerant
liquid as a result of the heat exchange relationship with the
fluid. The condensed liquid refrigerant from condenser 304 flows
through an expansion device (not shown) to the evaporator 306.
[0021] The condensed liquid refrigerant delivered to the evaporator
306 enters into a heat exchange relationship with a fluid, e.g.,
air or water, but preferably air, and undergoes a phase change to a
refrigerant vapor as a result of the heat exchange relationship
with the fluid. The vapor refrigerant in the evaporator 306 exits
the evaporator 306 and returns to the compressor 302 by a suction
line to complete the cycle (and the reversing valve arrangement 350
if operated as a heat pump). It is to be understood that any
suitable configuration of condenser 304 and evaporator 306 can be
used in the system 300, provided that the appropriate phase change
of the refrigerant in the condenser 304 and evaporator 306 is
obtained. The HVAC or refrigeration system 300 can include many
other features that are not shown in FIGS. 1 and 2. These features
have been purposely omitted to simplify the drawing for ease of
illustration.
[0022] Referring now to FIG. 3, in a preferred embodiment of the
invention, operation of the self-modulation compressor in the
HVAC&R system 300 involves several steps. To begin, in Step
402, the temperature in an indoor space is measured. Next, the
measured temperature is compared to a predetermined temperature set
point in Step 404. If the measured temperature satisfies the
predetermined temperature set point requirement, the control
returns to Step 402. Otherwise, the measured temperature does not
satisfy the predetermined temperature set point requirement in Step
404, i.e., the measured temperature is less than the predetermined
temperature set point if this system is in a heating mode of
operation or the measured temperature is greater than the
predetermined temperature set point when the system is in a cooling
mode of operation. In other words, for a cooling system, this
occurs when the temperature of a space rises above the
predetermined temperature set point. For a heating system, this
occurs when the temperature of a space falls below the
predetermined temperature set point.
[0023] If the temperature set point is not satisfied in Step 404,
the control proceeds to Step 408, where the compressor is started
(if necessary) and the control valve is in the open position to
operate the compressor at partial or reduced capacity. Preferably,
the partial capacity of the compressor can range from about 70% of
full capacity to about 90% of full capacity. As the compressor
operates, the pressure within the compressor housing builds if the
heating or cooling demand is not being satisfied, thereby creating
a need for higher capacity from the compressor. In Step 410, the
pressure in the compressor is compared to a predetermined set point
of pressure differential between the suction inlet and the
discharge outlet of the compressor. In an alternate embodiment, the
pressure in the compressor is compared to a predetermined pressure
set point, e.g., suction pressure set point or discharge pressure
set point, rather than the differential pressure of the suction
inlet and discharge outlet of the compressor. If the pressure
differential in the compressor is less than the predetermined
pressure differential set point, the control returns to Step 408 to
continue operating at partial capacity. Otherwise, the control
proceeds to Step 412 to operate the compressor at full
capacity.
[0024] In a preferred embodiment, the pressure control valve within
the compressor housing is calibrated to perform the comparison Step
410 and to close from the open position to operate the compressor
at full capacity when the pressure differential of the compressor
reaches the predetermined pressure differential set point. When the
pressure differential set point is reached, the control valve
activates and closes, which generates full capacity in the
compressor. The compressor operates at full capacity until the
predetermined temperature set point is reached in Step 414. If the
predetermined temperature set point is not satisfied in Step 414,
the control returns to Step 412 to continue operating the
compressor at full capacity. However, if the predetermined
temperature set point has been satisfied in Step 414, the
compressor is shut down at Step 406 and the process begins again at
Step 402. Once the compressor is operating at full capacity, the
control valve prevents any switching to the lower capacity until
after the compressor has been shut down.
[0025] In an alternate embodiment of the invention, the control
valve can be arranged to permit operation of the compressor in full
capacity mode when the control valve is in the open position and in
partial capacity mode when the control valve is in the closed
position. In addition, the control valve can be located in any
suitable location within the compressor to control the capacity
during operation.
[0026] The control valve is activated only by pressure levels
within the compressor regardless of the temperature levels within
the compressor or surrounding the system. The transition between
partial and full capacity occurs almost instantaneously with the
control valve moving from the open to the closed position. The
almost instantaneous switch from the open to the closed position
essentially eliminates a transitional range where the valve is
neither fully open nor fully closed.
[0027] FIGS. 4 and 5 illustrate one embodiment of the pressure
control valve configuration of the present invention. FIG. 4
illustrates the pressure control valve 404 in the open position.
The pressure control valve 404 is in the open position when the
force exerted by the discharge pressure is less than the combined
force of the biasing force of the biasing member 470 plus the force
exerted by the suction pressure. A suction pressure channel 483
connects the suction side of the compressor to the low-pressure
side of the valve 404. The valve member 464 being in the first,
open, position permits flow through the opening 484 and the flow
passage 454 to the suction channel 328. When the valve member 464
is in the first position opening the flow passage 454, the
reciprocating compressor 416 operates in a reduced capacity mode.
In this mode, the fluid in the compression chamber 332 flows back
through the opening 484 into flow passage 454, and even into the
suction channel 328 in the manifold. The opening 484 and flow
passage 454 are in effect combined to provide a reexpansion area in
fluid communication with the compression chamber 332. In effect,
the fluid in the compression chamber 332 is not compressed beyond
the suction pressure, until the reciprocating piston travels beyond
the opening 484.
[0028] As illustrated in FIG. 5, when the discharge pressure
reaches a predetermined level, the force exerted by the discharge
pressure overcomes the combined force, i.e., the biasing force of
the biasing member 470 plus the force exerted by the suction
pressure channel 483, and moves the valve member 464 to the second
position and the stem portion 465 prevents flow through the flow
passage 454 (and possibly through suction pressure channel 483).
When the valve member 464 is in the second position preventing flow
through the flow passage 454, the reciprocating compressor 416
operates in a full capacity mode because no fluid exits the
compression chamber 332 through the flow passage 454. In other
words, the full stroke length of the reciprocating piston 336 is
utilized to compress the fluid entering and exiting the compression
chamber 332 through the inlet 340 and outlet 342.
[0029] Thus, by adjusting the location of the opening 484 relative
to the bottom dead center position of the reciprocating piston 336,
the reciprocating compressor 416 achieves a desired capacity
modulation. Also, by adjusting the biasing force exerted by the
biasing member 470, the reciprocating compressor 416 controls the
discharge pressure at which valve member 464 prevents flow through
the flow passage 454. Accordingly, the system efficiency of an
air-conditioning or refrigeration system can be improved by
optimizing the combination of the degree of capacity modulation and
the pressure at which the valve member 464 prevents flow through
the flow passage 454. Preferably, the location of the opening 484
is adjusted to obtain the desired reduced capacity percentage of
full capacity. The valve member may be any suitable valve
configuration or multiple valve configuration.
[0030] An alternate embodiment of the invention includes a system
with no suction pressure channel 483 connected to the low-pressure
side of the valve member 404. This embodiment allows for a
transitional period between the open position and the closed
position of the valve member 404. In one embodiment, the compressor
pressure differential is at 0 psi on start-up and builds pressure
in the compressor while operating in a reduced capacity mode. Once
the compressor reaches the lower limit (e.g., 114 psi) of the
predetermined differential pressure range, the control valve begins
to close and reaches the fully closed position at the upper limit
(e.g., 129 psi) of the predetermined differential pressure range.
The pressure in the compressor continues to build until a full
capacity steady state differential pressure (e.g., 145 psi) is
obtained in the compressor. This transitional period exists during
the time it takes the valve member to switch between the open
position and the closed position.
[0031] While the invention has been described with reference to a
preferred embodiment, it will be understood by those skilled in the
art that various changes may be made and equivalents may be
substituted for elements thereof without departing from the scope
of the invention. In addition, many modifications may be made to
adapt a particular situation or material to the teachings of the
invention without departing from the essential scope thereof.
Therefore, it is intended that the invention not be limited to the
particular embodiment disclosed as the best mode contemplated for
carrying out this invention, but that the invention will include
all embodiments falling within the scope of the appended
claims.
* * * * *