U.S. patent application number 11/832176 was filed with the patent office on 2009-02-05 for system and method of controlling fluid flow through a fluid cooled heat exchanger.
This patent application is currently assigned to LIEBERT CORPORATION. Invention is credited to Benedict J. DOLCICH, Michael Jason GLOECKNER, Gary HELMINK, Roger D. NOLL, Russell C. TIPTON.
Application Number | 20090031735 11/832176 |
Document ID | / |
Family ID | 39558708 |
Filed Date | 2009-02-05 |
United States Patent
Application |
20090031735 |
Kind Code |
A1 |
NOLL; Roger D. ; et
al. |
February 5, 2009 |
SYSTEM AND METHOD OF CONTROLLING FLUID FLOW THROUGH A FLUID COOLED
HEAT EXCHANGER
Abstract
A vapor compression cooling system having a control unit adapted
to receive working fluid pressure or temperature information to
control a condenser cooling fluid control valve to minimize flow
changes through the valve.
Inventors: |
NOLL; Roger D.; (Gahanna,
OH) ; HELMINK; Gary; (Galloway, OH) ;
GLOECKNER; Michael Jason; (Galena, OH) ; TIPTON;
Russell C.; (Westerville, OH) ; DOLCICH; Benedict
J.; (Westerville, OH) |
Correspondence
Address: |
LOCKE LORD BISSELL & LIDDELL LLP;ATTN: IP DOCKETING
600 TRAVIS STREET, 3400 CHASE TOWER
HOUSTON
TX
77002
US
|
Assignee: |
LIEBERT CORPORATION
Columbus
OH
|
Family ID: |
39558708 |
Appl. No.: |
11/832176 |
Filed: |
August 1, 2007 |
Current U.S.
Class: |
62/115 ;
62/216 |
Current CPC
Class: |
F25B 6/04 20130101; F25B
2339/047 20130101; F25B 2700/21163 20130101; F25B 2600/17 20130101;
F25B 49/027 20130101; F25B 2500/26 20130101 |
Class at
Publication: |
62/115 ;
62/216 |
International
Class: |
F25B 41/04 20060101
F25B041/04; F25B 1/00 20060101 F25B001/00 |
Claims
1. A method of controlling a vapor compression cooling system
comprising: operating a vapor compression cooling cycle comprising
a condenser; determining a pressure or temperature of a fluid
leaving the condenser; and changing a valve position in response to
the pressure or temperature to control a flow of cooling fluid
through the condenser.
2. The method of claim 1 wherein the step of: changing the valve
position using incremental valve repositions at discrete points in
time.
3. The method of claim 1 wherein the condenser is a paradenser.
4. A vapor compression cooling system comprising: a vapor
compression cooling cycle comprising a condenser and a working
fluid; a condenser cooling cycle comprising a fluid control valve
adapted to vary a cooling fluid flow through the condenser; a
transducer associated with the condenser and adapted to transduce
either pressure or temperature of the working fluid; and a
controller adapted to vary the position of the fluid control valve
in response to the transduced pressure or temperature.
5. The vapor compression cooling system of claim 4 wherein the
controller is adapted to vary the position of the fluid control
valve using incremental valve repositions at discrete points in
time in response to the transduced pressure or temperature.
6. A method of controlling a vapor compression cooling system
comprising: operating a vapor compression cooling cycle comprising
one or more condensers; determining a pressure or temperature of a
fluid leaving the one or more condensers; and changing the heat
transfer area in response to the pressure or temperature.
7. The method of claim 6 wherein the one or more condensers is one
or more paradensers.
8. A vapor compression cooling system comprising: a vapor
compression cooling cycle comprising one or more condensers and a
working fluid; a condenser cooling cycle comprising a fluid control
valve adapted to vary a cooling fluid flow through the one or more
condensers; a transducer associated with the condenser and adapted
to transduce either pressure or temperature of the working fluid; a
system associated with the one or more condensers and adapted to
direct cooling fluid flow through one or more condensers; and a
controller adapted to vary the fluid flow through the one or more
condensers to change the heat transfer area.
9. The vapor compression system of claim 8 wherein the system is a
manifold.
10. A method of controlling a vapor compression cooling system
comprising: operating a vapor compression cooling cycle comprising
one or more condensers; determining a pressure or temperature of a
fluid leaving the one or more condensers; changing a valve position
in response to the pressure or temperature to control a flow of
cooling fluid through the on or more condensers; and changing the
heat transfer area in response to the pressure or temperature.
11. The method of claim 10 wherein the one or more condensers is
one or more paradensers.
12. A vapor compression cooling system comprising: a vapor
compression cooling cycle comprising one or more condenser and a
working fluid; a condenser cooling cycle comprising a fluid control
valve adapted to vary a cooling fluid flow through the one or more
condenser; a transducer associated with the one or more condenser
sand adapted to transduce either pressure or temperature of the
working fluid; and a controller adapted to vary the position of the
fluid control valve in response to the transduced pressure or
temperature and/or vary the fluid flow through the one or more
condensers to change the heat transfer area.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] Not Applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not applicable.
REFERENCE TO APPENDIX
[0003] Not applicable.
BACKGROUND OF THE INVENTION
[0004] 1. Field of the Invention
[0005] The inventions disclosed and taught herein relate generally
to a cooling system, and more specifically to a system and method
of controlling a cooling system.
[0006] 2. Description of the Related Art
[0007] In a conventional vapor compression cooling system, a
compressor mechanically elevates the temperature and pressure of a
working fluid to achieve a desired vapor state. A heat exchanger,
typically designated as a condenser, transfers heat from the
compressed working fluid to an environment or fluid, thereby
condensing the working fluid. An expansion valve or other expansion
device lowers the pressure of the condensed working fluid as it
enters a second heat exchanger, typically designated as an
evaporator, in which heat from the environment to be cooled is
transferred to the working fluid. The heated working fluid returns
to the compressor, and the cycle is repeated.
[0008] The condenser transfers heat from the working fluid (i.e,
heat from the environment to be cooled) by transferring heat to
another environment (e.g., outdoors) or to a cooling fluid (e.g.,
chilled water/condenser fluid). A typical chilled water condenser
comprises a heat exchanger, and a fluid regulating valve. The
condenser fluid picks up heat from the refrigerant flowing through
the condenser and dumps the heat to the environment. The condenser
fluid then flows through the regulating fluid valve and then back
to the condenser. An alternate configuration would be to locate the
valve after the condenser.
[0009] A vapor compression cooling system may be designed such that
its heat removal (or cooling) capacity matches the heat load
generated by the space that is being cooled. However, the heat load
of the space to be cooled will vary according to the various
factors, including, for example, the season (outdoor temperature),
equipment operating within the space, number of people present in
the space, etc. To provide adequate cooling under all
circumstances, the cooling system must have capacity equal to the
maximum heat load of the space to be cooled. However, this will
result in selection of a cooling system with a capacity larger than
required for most operating conditions. If the cooling system is
operating at less than its rated capacity, the cooling system
(e.g., refrigerant compressor) may cycle on and off repeatedly.
[0010] The inventions disclosed and taught herein relate to an
improved cooling system, and a method and apparatus for controlling
a cooling system.
BRIEF SUMMARY OF THE INVENTION
[0011] In one aspect of the present invention, a method of
controlling a vapor compression cooling system is provided, which
comprises operating a vapor compression cooling cycle comprising a
condensing heat exchanger; determining a pressure or temperature of
a fluid leaving the condenser; determining when to change a valve
position in response to the pressure or temperature to control a
flow of cooling fluid through the condenser.
[0012] Another aspect of the present invention comprises a vapor
compression cooling system having a vapor compression cooling cycle
comprising a condenser and a working fluid; a condenser cooling
cycle comprising a fluid control valve adapted to vary a cooling
fluid flow through the condenser; a transducer associated with the
condenser and adapted to transduce either pressure or temperature
of the working fluid; and a controller adapted to determine when to
vary the position of the fluid control valve in response to the
transduced pressure or temperature.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0013] FIG. 1 illustrates one of many embodiments of a cooling
system utilizing aspects of the present invention.
[0014] FIG. 2 is a chart that illustrates an exemplary embodiment
of the bands in which the motorized ball valve of a vapor
compression system operates.
[0015] FIG. 3 illustrates another embodiment of a vapor compression
system utilizing aspects of the present invention.
DETAILED DESCRIPTION
[0016] The Figures described above and the written description of
specific structures and functions below are not presented to limit
the scope of what Applicants have invented or the scope of the
appended claims. Rather, the Figures and written description are
provided to teach any person skilled in the art to make and use the
inventions for which patent protection is sought. Those skilled in
the art will appreciate that not all features of a commercial
embodiment of the inventions are described or shown for the sake of
clarity and understanding. Persons of skill in this art will also
appreciate that the development of an actual commercial embodiment
incorporating aspects of the present inventions will require
numerous implementation-specific decisions to achieve the
developer's ultimate goal for the commercial embodiment. Such
implementation-specific decisions may include, and likely are not
limited to, compliance with system-related, business-related,
government-related and other constraints, which may vary by
specific implementation, location and from time to time. While a
developer's efforts might be complex and time-consuming in an
absolute sense, such efforts would be, nevertheless, a routine
undertaking for those of skill this art having benefit of this
disclosure. It must be understood that the inventions disclosed and
taught herein are susceptible to numerous and various modifications
and alternative forms. Lastly, the use of a singular term, such as,
but not limited to, "a," is not intended as limiting of the number
of items. Also, the use of relational terms, such as, but not
limited to, "top," "bottom," "left," "right," "upper," "lower,"
"down," "up," "side," and the like are used in the written
description for clarity in specific reference to the Figures and
are not intended to limit the scope of the invention or the
appended claims.
[0017] Particular embodiments of the invention may be described
below with reference to block diagrams and/or operational
illustrations of methods. It will be understood that each block of
the block diagrams and/or operational illustrations, and
combinations of blocks in the block diagrams and/or operational
illustrations, can be implemented by analog and/or digital
hardware, and/or computer program instructions. Such computer
program instructions may be provided to a processor of a
general-purpose computer, special purpose computer, ASIC, and/or
other programmable data processing system. The executed
instructions may create structures and functions for implementing
the actions specified in the block diagrams and/or operational
illustrations. In some alternate implementations, the
functions/actions/structures noted in the figures may occur out of
the order noted in the block diagrams and/or operational
illustrations. For example, two operations shown as occurring in
succession, in fact, may be executed substantially concurrently or
the operations may be executed in the reverse order, depending upon
the functionality/acts/structure involved.
[0018] Computer programs for use with or by the embodiments
disclosed herein may be written in an object oriented programming
language, conventional procedural programming language, or
lower-level code, such as assembly language and/or microcode. The
program may be executed entirely on a single processor and/or
across multiple processors, as a stand-alone software package or as
part of another software package.
[0019] Applicants have created a system and method of controlling
the fluid flow through a fluid cooled heat exchanger in a vapor
compression cooling system. By controlling the fluid flow through
the fluid cooled heat exchanger, the thermal capacity of the
cooling system can be optimally controlled. The fluid flow and thus
the thermal capacity of the cooling system, may be optimally
controlled in at least two ways: (1) by controlling the amount of
heat removed from the condenser by controlling the cooling fluid
flow through the condenser and (2) by controlling the amount of
heat removed from the condenser by adjusting the heat transfer area
of the condenser. For example, increasing the cooling fluid flow
through the condenser may increase the cooling capacity of the
system because more heat can be transferred from the refrigerant to
the cooling fluid. Alternately, increasing the heat transfer area,
e.g., the condenser surface area, may increase the heat transferred
from the refrigerant to the cooling fluid thereby increasing the
capacity of the cooling system. It will be appreciated that the
cooling capacity of the system can be reduced in similar fashion,
as desired.
[0020] FIG. 1 illustrates an exemplary, and one of many, embodiment
of a vapor compression cooling system 100 utilizing aspects of the
present invention. The cooling system 100 generally includes a
vapor compression cooling loop 102 comprising a compressor 120, a
liquid cooled condenser 130, an expansion mechanism 150, evaporator
(i.e. heat exchanger) 160 and transducer 190. In this particular
embodiment, the working fluid may be any two-phase refrigerant,
such as chloroflourocarbons (CFCs), hydroflourocarbons (HFCS), or
hydrochlorofluorocarbon (HCFCs) such as R-22 but not excluding
alternative refrigerants. Secondary cooling loop 104 comprises an
liquid cooler (i.e. heat exchanger) 170, a flow valve 140 and
liquid cooled condenser (i.e. heat exchanger) 130. Cooling system
100 also comprises a control unit 180 that is in communication with
valve 140 and transducer 190.
[0021] Operation of cooling system 100 may be described as follows.
Refrigerant is compressed in the compressor 120, which may be a
reciprocating, scroll, or other compressor type, and preferably is
a digital scroll compressor, such as those offered by Copeland.
After the refrigerant is compressed, it travels through a discharge
line 112 to the liquid cooled condenser 130, where heat is removed
from the refrigerant. Upon leaving liquid cooled condenser 130, the
temperature and/or pressure of the refrigerant is transduced by
transducer 190, which may be any type of pressure or temperature
transducer known to those of ordinary skill in the art. The
refrigerant travels through a first liquid line 114 to an expansion
mechanism 150. Expansion mechanism 150 may comprise a valve,
orifice or other liquid expansion device known to those of ordinary
skill in the art. The expansion mechanism 150 causes a pressure
drop in the refrigerant, as the refrigerant passes through the
mechanism.
[0022] Upon leaving the expansion mechanism, the refrigerant
travels through second liquid line 116, arriving at evaporator 160.
The low-pressure refrigerant absorbs heat from the environment to
be cooled. More specifically, air from the environment to be cooled
is passed through the evaporator coils so that heat is transferred
from the air to the refrigerant. Refrigerant carrying the heat
extracted from the environment then returns to the compressor 120
by suction line 118, completing the vapor compression cycle. It
will be appreciated that the amount of heat absorbed in the
evaporator 160 and the amount of heat transferred in the condenser
130 affect how long and how often compressor 120 must run.
Therefore, controlling the amount of heat transferred in the liquid
cooled condenser 130 directly affects the operation of compressor
120.
[0023] In the secondary cooling loop 104, liquid cooled condenser
130 transfers heat from the refrigerant to a cooling fluid, which
may be a two-phase refrigerant, glycol, water, or other type of
fluid. In the particular embodiment shown in FIG. 1, the cooling
fluid is preferably chilled water. The chilled water passes through
the first cooling fluid line 172 to cooling fluid liquid cooler 170
where the heat from the cooling fluid is rejected into the outside
environment by any known means, such as one or more cooling fans.
Chilled water then travels to valve 140, which may be an
electrically controlled motorized ball valve, solenoid proportional
valve, globe valve, or pneumatic, digital, hydraulic, analog or
other variable flow restricting device known to a person of
ordinary skill in the art. Preferably, the valve 140 is a motorized
ball valve. The cooling fluid travels through third cooling fluid
line 176 and returns to liquid cooled condenser 130 where heat is
transferred from the refrigerant to the cooling fluid.
[0024] Valve 140 may be controlled manually or by control unit 180.
Control unit 180 receives one or more inputs from transducer 190
and outputs one or more control signals to valve 140 or an actuator
that controls valve 140. Control unit 180 may use any of a number
of control routines to control the valve 140 based on the
transduced property of the refrigerant, such as pressure or
temperature. Additionally, control unit 180 can be used to control
compressor 120. For example, the control unit 180 may instruct the
compressor 120, such as a digital scroll compressor, when to cycle
on and off.
[0025] In the embodiment illustrated in FIG. 1, a control routine
is implemented in controller 180 to optimally control cooling
system 100. A valve position (or flow volume) control routine maybe
implemented by control unit 180 to control the opening and closing
of valve 140. The control unit 180 and control software may be
designed to implement a control strategy that serves to maintain
the refrigerant discharge pressure within acceptable limits with
minimal valve 140 repositions. A preferred valve position control
routine is described below. The routine assumes a variable capacity
digital scroll compressor is used as compressor 120.
[0026] One of the goals of the valve position control routine is to
avoid placing the valve, to the extent possible, into an opening
state (where the valve 140 is continuously opening) or into a
closing state (where the valve 140 is continuously closing). To
accomplish that result, the control routine implements a control
strategy that makes (or does not make) incremental valve
repositions at discrete points in time, such as, for example,
generally corresponding to the discrete points in time when the
refrigerant pressure is sampled.
[0027] Another goal is to avoid startup high pressure conditions by
opening valve 140 to a predetermined setpoint before the compressor
120 is started. As described in this embodiment, the setpoint is
preferably set to 50% along with a thirty second delay.
[0028] Another goal of the valve position control routine is to
have an efficient control strategy that can be implemented in a
system, like those associated with Copeland Digital Scroll.RTM.
compressors, where the refrigerant pressure is not substantially
stable. But rather is typically always increasing or decreasing and
where the instantaneous or near-instantaneous rate of change of the
refrigerant pressure does not provide reliable information as to
the overall direction of change of the refrigerant pressure. To
allow the valve position control routine to operate in such
environments, the valve position control routine does not use or
rely upon, the rate of change of the refrigerant discharge pressure
or whether the discharge pressure is increasing (or not) or
decreasing (or not) to control the valve 140.
[0029] In general, the valve position control routine samples the
refrigerant discharge pressure, the pressure read by discharge
transducer 190, on a predetermined basis and makes a determination
to cause (or not to cause) a valve reposition each time a
refrigerant discharge pressure reading is obtained. Alternative
embodiments of the valve position control routine could use other
readings such as the temperature of the discharge transducer 190 to
determine whether to cause (or not to cause) a valve reposition
each time a reading is obtained. These alternatives may include
using different types of refrigerant which may change the pressure
settings.
[0030] The operation of a preferred valve position control routine
may be understood with reference to FIG. 2. Referring to FIG. 2,
the valve position control routine operates, in principal, to
control the refrigerant discharge pressure such that it remains
within an "Acceptable Operating Band." This is accomplished in the
valve position control routine by defining a plurality of different
bands of detected refrigerant discharge pressures and then taking
(or not taking) action, depending on where a detected discharge
pressure falls within the defined bands.
[0031] The first band defined by the valve position control routine
is the Acceptable Operating Band. This band reflects the range of
refrigerant discharge pressures within which the system is intended
to operate. In the exemplary version of the valve position control
routine, the Acceptable Operating Band was set and fixed as the
band between 175 and 210 PSIG. In an another version of the valve
position control routine the users of the system will be able to
enter a pressure adjustment offset value that will index the
operating band by the offset value.
[0032] In addition to the Acceptable Operating Band, the valve
position control routine defines four bands reflecting discharge
pressures above the upper limit of the Acceptable Operating Band.
These bands are illustrated in FIG. 2, which is labeled to
identify: (i) a First High Band; (ii) a Second High Band; (iii) a
Third High Band; and (iv) a High Band. In the exemplary version of
the valve position control routine: (ii) a First High Band was set
as the band between 210-220 PSIG; (ii) the Second High Band was set
as the band between 220-230; (iii) the Third High Band was set as
the band between 230-350 PSIG; and (iv) the High Band was set as
the band of pressures over 350 PSIG. In another version of the
valve position control routine users of the system will be able to
enter a pressure adjustment offset value that will index all bands
except (iv) High Band by the offset value.
[0033] The valve position control routine also defines three bands
reflecting discharge pressures below the lower limit of the
Acceptable Operating Band. These bands are illustrated in FIG. 2,
which is labeled to identify: (i) a First Low Band; (ii) a Second
Low Band; and (iii) a Low Band. In the exemplary version of the
valve position control routine: (ii) the First Low Band was set as
the band between 160-175 PSIG; (ii) the Second Low Band was set as
the band between 100-160 PSIG; and (iii) the Low Band was set as
the band below 100 PSIG. In another version of the valve position
control routine the users of the system will be able to enter a
pressure adjustment offset value that will index all bands except
(iii) Low Band by the offset value.
[0034] As part of its operation, and to limit the number of
repositioning events for valve 140, the valve position control
routine keeps track of whether a repositioning event has occurred
in the First High Band, the Second High Band and/or the First Low
Band.
[0035] High Refrigerant Pressure Example. The valve position
control routine initially starts under "Initial Conditions" where
there are no recorded repositioning events for the First High Band,
the Second High Band, and/or the First Low Band. If a detected
pressure within the Acceptable Operating Band is detected when the
Initial Conditions exist, valve position control routine will take
no action with respect to the position of the valve 140 (i.e., the
position of the valve 140 will not change in response to that
detected pressure).
[0036] If, while the Initial Conditions exist, a detected pressure
above or below the upper limit of the Acceptable Operating Band is
detected, the valve position control routine may or may not
reposition the valve 140. The situation of a detected pressure
above the Acceptable Operating Band is discussed first.
[0037] If, while Initial Conditions exist, a pressure reading is
provided that is above the lower limit of the First High Band, the
valve position control routine will open the valve 140 an
incremental amount of 5% and will record a repositioning event for
the First High Band. If, while Initial Conditions exist, a pressure
reading is provided that is above the lower limit of the Second
High Band, the valve position control routine will open the valve
140 an incremental amount of 5% and will record a repositioning
event for the Second High Band. This repositioning, if made, is
additive of any repositioning made as a result of the pressure
being above the lower limit of the First High Band. Thus, if the
detected pressure is at a level above the lower limit of the Second
High Band, a 5% incremental opening will occur as a result of the
pressure above the lower limit of the First High Band and a further
5% incremental opening will occur as a result of the pressure being
above the lower limit of the Second High Band. Under these
conditions, a repositioning event will be recorded for both the
First High Band and the Second High Band.
[0038] If, while Initial Conditions exist, a pressure reading is
provided that is above the lower limit of the Third High Band, the
valve position control routine will open the valve 140 an
incremental amount of 10% and a repositioning event is recorded for
the Third High Band. This repositioning, if made, is additive of
any repositioning made as a result of the pressure being above the
lower limit of the First High Band or the Second High Band.
Finally, if, while Initial Conditions exist, a pressure reading is
provided that is above the lower limit of the High Band, the valve
140 is opened to its fully open (100%) point.
[0039] Once a repositioning event has occurred, such that Initial
Conditions no longer exist, the operation of the valve position
control routine changes the system such that the number of
repositioning events used to bring the refrigerant discharge
pressure back to within the Acceptable Operating Band is limited.
This is accomplished in the following manner.
[0040] If, once a repositioning event has occurred, a pressure is
detected that is above the lower limit of the High Band, the valve
position control routine will either: (i) open the valve 140 to its
fully open (100%) position (if the valve 140 was not at that point)
or (ii) take no action if the valve 140 is already at the 100% open
position.
[0041] If, once a repositioning event has occurred, a pressure is
detected that is between the lower and upper limits of the Third
High Band, the valve position control routine will open the valve
140 an additional 10% from its previous position (up to the 100%
open position). This 10% open repositioning will occur regardless
of the status of any prior repositioning events.
[0042] If, once a repositioning event has occurred, a pressure is
detected that is between the lower and upper limits of the Second
High Band, the valve position control routine will take (or not
take) action as follows. If there is no recorded repositioning
event for the Second High Band when the pressure is detected, the
system will open the valve 140 incrementally 5% and will record a
Second High Band repositioning event. If there is a recorded
repositioning event for the Second High Band, the valve position
control routine will take no action and will allow the valve 140 to
remain in its existing position.
[0043] If, once a repositioning event has occurred, a pressure is
detected that is between the lower and upper limits of the First
High Band, the valve position control routine will take no action
and will allow the valve 140 to remain in its existing position.
This is because, under such conditions, a repositioning event would
have been recorded for the First high Band.
[0044] As the above, indicates, once a repositioning event has
occurred, valve position control routine operates such as to avoid
placing the valve 140 in an opening state (where the valve 140 is
always opening). Specifically, in the valve position control
routine, there is only a single, one-time, 5% opening adjustment
for a detected pressure within the First High Band, and a single,
one-time, 5% opening adjustment for a detected pressure within the
Second High Band. After these single, one-time, opening adjustments
are made there are no other adjustments made on detected pressure
if the detected pressure is within the First High Band or the
Second High Band.
[0045] As a result of the fact that one opening adjustment is made
(based on detected pressure) for detected pressures within the
First High Band and the Second High Band, there is the potential in
the valve position control routine for the refrigerant discharge
pressure to settle at a point within the First High Band and the
Second High Band (after the initial opening repositioning are
made). To avoid this result, and to move the refrigerant pressure
into the Acceptable Operating Band, the valve position control
routine uses a timer based control strategy that runs in parallel
with the control strategy based on detected pressures, described
above.
[0046] In accordance with the timer-based control strategy, the
valve position control routine sets a five minute timer when a
pressure is detected that is above the lower limit of the First
High Band. Once set, the timer is reset upon: (i) the occurrence of
a repositioning event, or (ii) the detection of a pressure below
the lower limit of the First High Band. If this five-minute timer
"times out" before it is reset, the valve position control routine
will open the valve 140 an additional 5%. In this manner, the
refrigerant discharge pressure will be driven towards the
Acceptable Operating Range using a limited number of repositioning
events.
[0047] In addition to the opening repositioning events described
above, the valve position control routine may implement, under
certain circumstances, a "closing" valve repositioning, accompanied
by a clearing of the record of a repositioning for the First High
Band or the Second High Band. Specifically, if a pressure is
detected that is 5 PSIG below the lower limit of the Second High
Band and there is a record of a repositioning for the Second High
Band, the valve position control routine will: (i) determine
whether to make an adjustment to the valve and (ii) clear the
record of the repositioning for the Second High Band. Similarly, if
a pressure is detected that is 5 PSIG below the lower limit of the
First High Band and there is a record of a repositioning for the
First High Band, the valve position control routine will: (i)
determine whether to make an adjustment to the valve and (ii) clear
the record of the repositioning for the First High Band. Once the
records for any repositioning in the Second High Band and the First
High Band are cleared, such that there are no records of
repositioning, the Initial Conditions will be re-established.
[0048] Low Refrigerant Pressure Example. The above discussion
concerned the operation of the valve 140 under conditions where the
detected refrigerant pressure was above the upper limit of the
Acceptable Operating Band. The operation of the system when the
pressure is below the lower limit of the Acceptable Operating Band
is similar.
[0049] Starting at Initial Conditions, the valve position control
routine will close valve 140 4% once, for each detected pressure
that is below the upper limit of the First Low Band. A record of
such repositioning is kept to ensure that one repositioning is made
for such a detected pressure. If, after the initial 4% closure is
made in response to the detection of pressure below the upper limit
of the First Low Band, pressures are detected that are within the
First Low Band, no additional closing repositioning will be
made.
[0050] If a pressure is detected that is below the upper limit of
the Second Low Band, the valve position control routine will close
the valve 140 5% incrementally (up to a minimum closure at the 25%
open point) in response to that detected pressure, regardless of
any prior repositioning events.
[0051] If a pressure is detected that is below the upper limit of
the Low Band, the valve position control routine will close valve
140 to the 25% open position in response to that detection, if the
valve 140 is not already at the 25% open position.
[0052] In a manner like that described in connection with a high
pressure, whenever a pressure below the upper limit of the First
Low Band is detected, a five-minute timer is set. The timer will be
reset upon: (i) the detection of a pressure above the upper limit
of the First Low Band or (ii) a repositioning of the valve 140. In
this manner, timer-based repositioning events will drive the
refrigerant pressure to within the Acceptable Operating Band.
[0053] In addition to the closing repositioning events described
above, valve position control routine may implement, under certain
circumstances, an "opening" valve repositioning, accompanied by a
clearing of the record of a repositioning for the First Low Band or
the Second High Band. Specifically, if a pressure is detected that
is 5 PSIG above the upper limit of the First Low Band and there is
a record of a repositioning for the First Low Band, the valve
position control routine will: (i) determine whether to make an
adjustment to the valve and (ii) clear the record of the
repositioning for the First Low Band.
[0054] Other and further embodiments of the valve position control
routine may be implemented. For example, the system could use the
discharge temperature measured by discharge transducer 190 to
implement the control strategy. Further, an electronic timing
circuit could be designed to control the valve 140 in place of or
in addition to the valve position control routine.
[0055] The inventions disclosed and taught herein solves the
problem with, and problems associated with, the rapid fluctuations
of pressure of the fluid flowing through the fluid cooled heat
exchanger. For example, the system and method uses a control
strategy that eliminates the movements in the valve. The life of
the valve is increased due to reduced motor and valve repositions.
The cooling system performance improves because pressures and
temperatures are more stable. The life of other components that
respond to pressure change also increases. It reduces the supply
fluid pressure spikes because the valve will never position to full
close while system is operating. Servicing the valve does not
require opening the refrigerant system.
[0056] FIG. 3 illustrates alternative embodiment of a vapor
compression system utilizing aspects of the present invention. This
alternative embodiment controls the cooling capacity by controlling
the heat transfer area of the condenser(s). FIG. 3 illustrates a
portion of a traditional vapor compression cooling system 300, such
as the one describes in FIG. 1, utilizing paradenser 310, for
example the Liebert Paradenser.RTM., in the place of condenser 30.
A paradenser is a series of condensers, depicted here as condensers
310a, 310b, and 310c. In order to maximize the efficiency of the
paradenser and the vapor compression system as a whole, the system
is plumbed such that a manifold 340 is adapted to route cooling
fluid through one or more of condenser 310a, 310b, or 310c in
paradenser 310.
[0057] As described above, a control unit 380 may be adapted to
control the manifold 340 such that cooling fluid is routed to the
condensers as needed to optimize system capacity and/or to match
the heat load generated by the space that is being cooled. The
control unit 380 can direct cooling fluid flow through first fluid
flow line 302 when condensers 330b and 330c are not required to
reject heat from the refrigerant. The control unit 380 can direct
additional cooling fluid flow through second fluid flow line 304
when condenser 330c is not required to reject heat from the
refrigerant. Finally, control unit 380 can direct cooling fluid
flow through first cooling fluid line 306 when all three condensers
of the paradenser are needed to reject heat from the refrigerant.
For example, if the system needed to reject more heat from
refrigerant (based on the transduced temperature or pressure of the
working fluid), the control unit 380 would direct cooling fluid
through condenser 330c and condenser 330b. As more heat rejection
was necessary, control unit 380 could additionally direct cooling
fluid through condenser 330a. As more cooling fluid flows through
more condensers, more heat can be rejected from the refrigerant.
This embodiment could be implemented independent of or in
conjunction with the valve position control routine described
herein.
[0058] Other and further embodiments utilizing one or more aspects
of the inventions described above can be devised without departing
from the spirit of Applicant's invention. For example, instead of
using a paradenser to divert the control the cooling fluid flow, a
condenser that is divided into several parts can be utilized. The
divided condenser may be controlled so that fluid is sent to one or
more compartments to maximize the efficiency of the condenser.
Also, the controllable manifold may be used on the working fluid
side of the system to route working fluid to one or more condenser.
Further embodiments include multiple valves in multiple cooling
systems controlled by a single controller. Further, the various
methods and embodiments of the system and method of controlling a
fluid flow through a fluid cooled heat exchanger can be included in
combination with each other to produce variations of the disclosed
methods and embodiments. Discussion of singular elements can
include plural elements and vice-versa.
[0059] The order of steps can occur in a variety of sequences
unless otherwise specifically limited. The various steps described
herein can be combined with other steps, interlineated with the
stated steps, and/or split into multiple steps. Similarly, elements
have been described functionally and can be embodied as separate
components or can be combined into components having multiple
functions.
[0060] The inventions have been described in the context of
preferred and other embodiments and not every embodiment of the
invention has been described. Obvious modifications and alterations
to the described embodiments are available to those of ordinary
skill in the art. The disclosed and undisclosed embodiments are not
intended to limit or restrict the scope or applicability of the
invention conceived of by the Applicants, but rather, in conformity
with the patent laws, Applicants intend to fully protect all such
modifications and improvements that come within the scope or range
of equivalent of the following claims.
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