U.S. patent application number 12/726895 was filed with the patent office on 2010-09-30 for free cooling refrigeration system.
This patent application is currently assigned to Johnson Controls Technology Company. Invention is credited to William L. Kopko, Mustafa K. Yanik.
Application Number | 20100242532 12/726895 |
Document ID | / |
Family ID | 42309628 |
Filed Date | 2010-09-30 |
United States Patent
Application |
20100242532 |
Kind Code |
A1 |
Kopko; William L. ; et
al. |
September 30, 2010 |
FREE COOLING REFRIGERATION SYSTEM
Abstract
A refrigeration system includes a chiller with an integrated
free cooling system and refrigeration system. In certain
embodiments, the chiller may be a single package unit with all
equipment housed within the same support frame. The chiller may
generally include three modes of operation: a first mode that
employs free cooling, a second mode that employs free cooling and
implements a refrigeration cycle, and a third mode that uses the
free cooling system to remove heat from the refrigeration system. A
heat exchanger may be shared between the free cooling system and
the refrigeration system to transfer heat from the refrigeration
system to the free cooling system.
Inventors: |
Kopko; William L.; (Jacobus,
PA) ; Yanik; Mustafa K.; (York, PA) |
Correspondence
Address: |
Johnson Controls, Inc.;c/o Fletcher Yoder PC
P.O. Box 692289
Houston
TX
77269
US
|
Assignee: |
Johnson Controls Technology
Company
Holland
MI
|
Family ID: |
42309628 |
Appl. No.: |
12/726895 |
Filed: |
March 18, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61162825 |
Mar 24, 2009 |
|
|
|
Current U.S.
Class: |
62/498 ;
62/513 |
Current CPC
Class: |
F25B 40/04 20130101;
F25B 2700/21 20130101; F25B 2700/2106 20130101; F25B 41/00
20130101; F25D 16/00 20130101; F25B 25/005 20130101; F25B 2600/13
20130101; F25B 40/02 20130101; Y02B 30/70 20130101 |
Class at
Publication: |
62/498 ;
62/513 |
International
Class: |
F25B 1/00 20060101
F25B001/00; F25B 41/00 20060101 F25B041/00 |
Claims
1. A refrigeration system comprising: a free cooling system
configured to exchange heat between a cooling fluid and ambient
air; and a heat exchanger configured to receive refrigerant and to
transfer heat from the refrigerant to the cooling fluid.
2. The refrigeration system of claim 1, wherein the heat exchanger
is disposed within a high pressure side of a vapor-compression
refrigeration system.
3. The refrigeration system of claim 1, comprising a first
refrigeration system configured to implement a vapor-compression
cycle with the refrigerant.
4. The refrigeration system of claim 3, wherein the first
refrigeration system comprises: a compressor configured to compress
the refrigerant; a condenser configured to receive and to condense
the compressed refrigerant; an expansion device configured to
reduce pressure of the condensed refrigerant; and an evaporator
configured to evaporate the refrigerant by absorbing heat from the
cooling fluid prior to returning the refrigerant to the
compressor.
5. The refrigeration system of claim 4, wherein heat exchanger is
configured to condense or subcool the refrigerant exiting the
condenser or to desuperheat the compressed refrigerant prior to the
refrigerant entering the condenser.
6. The refrigeration system of claim 1, comprising an additional
heat exchanger configured to receive the refrigerant and transfer
heat to the cooling fluid, wherein the heat exchanger is configured
to partially condense the refrigerant and the additional heat
exchanger is configured to subcool the refrigerant.
7. The refrigeration system of claim 1, wherein the free cooling
system comprises an air-to-liquid heat exchanger configured to
transfer heat from the cooling fluid to the ambient air.
8. The refrigeration system of claim 1, comprising at least one
valve configured selectively to bypass the free cooling system and
to direct the cooling fluid to the free cooling system before the
cooling fluid enters an evaporator in fluid communication with the
refrigerant.
9. The refrigeration system of claim 1, wherein the free cooling
system comprises one or more valves defining a first circuit and a
second circuit, and wherein the first circuit is configured to
circulate the cooling fluid between a cooling loop and an
air-to-liquid heat exchanger in fluid communication with the
ambient air, and the second circuit is configured to circulate the
cooling fluid between the heat exchanger and the air-to-liquid heat
exchanger.
10. A refrigeration system comprising: a vapor-compression
refrigeration system comprising an evaporator configured to remove
heat from a cooling fluid circulating through a cooling loop; a
free cooling system configured to circulate the cooling fluid
through a first circuit to exchange heat between the cooling fluid
and ambient air without implementing a vapor-compression cycle; and
a second circuit disposed in the free cooling system and configured
to circulate an isolated portion of the cooling fluid through a
heat exchanger common to the vapor-compression refrigeration system
and the free cooling system.
11. The refrigeration system of claim 10, wherein the refrigeration
system is disposed within a common support frame.
12. The refrigeration system of claim 10, wherein the cooling fluid
comprises water, a brine solution, or a glycol solution.
13. The refrigeration system of claim 10, wherein the
vapor-compression refrigeration system includes a condenser and the
heat exchanger is configured to supplement the condenser by
desuperheating, subcooling, or partially condensing refrigerant
flowing within the vapor-compression refrigeration system.
14. The refrigeration system of claim 10, wherein the free cooling
system includes an air-to-liquid heat exchanger configured to
receive the cooling fluid from the first circuit and the second
circuit and to remove heat from the cooling fluid.
15. The refrigeration system of claim 14, wherein the
vapor-compression refrigeration system includes a condenser, and
wherein the condenser and the air-to-liquid heat exchanger comprise
multichannel heat exchangers configured to share a common fan.
16. The refrigeration system of claim 10, comprising a controller
configured to direct the cooling fluid through the first circuit or
through the second circuit based on a sensed temperature of the
ambient air.
17. The refrigeration system of claim 10, comprising one or more
valves or pumps configured selectively to direct the cooling fluid
through the first or second circuit.
18. A method for operating a refrigeration system, comprising:
operating a vapor-compression refrigeration system to remove heat
from a cooling fluid; and circulating an isolated portion of the
cooling fluid within a free cooling system to remove heat from the
vapor-compression refrigeration system.
19. The method of claim 18, comprising circulating the cooling
fluid to an air-to-liquid heat exchanger within the free cooling
system to remove heat from the cooling fluid.
20. The method of claim 18, comprising selecting a mode of
operation for the refrigeration system based on a sensed
temperature of ambient air, wherein the circulating an isolated
portion of the cooling fluid comprises a first mode of operation
and wherein removing heat from the free cooling system without
implementing a vapor-compression cycle comprises a second mode of
operation.
21. The method of claim 18, comprising exchanging energy between
the cooling fluid and a refrigerant within the vapor-compression
refrigeration system to partially condense or desuperheat the
refrigerant.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority from and the benefit of
U.S. Provisional Application Ser. No. 61/162,825, entitled "Free
Cooling Refrigeration System", filed Mar. 24, 2009, which is hereby
incorporated by reference.
BACKGROUND
[0002] The invention relates generally to free cooling
refrigeration systems.
[0003] Many applications exist for refrigeration systems including
residential, commercial, and industrial applications. For example,
a commercial refrigeration system may be used to cool an enclosed
space such as a data center, laboratory, supermarket, or freezer.
Very generally, refrigeration systems may include circulating a
fluid through a closed loop between an evaporator where the fluid
absorbs heat and a condenser where the fluid releases heat. The
fluid flowing within the closed loop is generally formulated to
undergo phase changes within the normal operating temperatures and
pressures of the system so that considerable quantities of heat can
be exchanged by virtue of the latent heat of vaporization of the
fluid.
[0004] Refrigeration systems may operate with a free cooling system
or loop when ambient temperatures are low. The free cooling system
may exploit the low temperature of the ambient air to provide
cooling without the need for an additional energy input from, for
example, a compressor, a thermoelectric device, or a heat source.
Typically, free cooling systems may employ a separate heat
exchanger or portion of a heat exchanger coil when operating in a
free cooling mode. When free cooling is not desired, or feasible,
the separate heat exchanger or coil portion may not be
utilized.
SUMMARY
[0005] The present invention relates to a refrigeration system with
a free cooling system configured to exchange heat between a cooling
fluid and ambient air. The refrigeration system also includes a
heat exchanger configured to receive refrigerant and to transfer
heat from the refrigerant to the cooling fluid.
[0006] The present invention also relates to a refrigeration system
with a vapor-compression refrigeration system that includes an
evaporator configured to remove heat from a cooling fluid
circulating through a cooling loop, a free cooling system
configured to circulate the cooling fluid through a first circuit
to exchange heat between the cooling fluid and ambient air without
implementing a vapor-compression cycle, and a second circuit
disposed in the free cooling system and configured to circulate an
isolated portion of the cooling fluid through a heat exchanger
common to the vapor-compression refrigeration system and the free
cooling system.
[0007] The present invention further relates to a method for
operating a refrigeration system that includes operating a
vapor-compression refrigeration system to remove heat from a
cooling fluid and circulating an isolated portion of the cooling
fluid within a free cooling system to remove heat from the
vapor-compression refrigeration system.
DRAWINGS
[0008] FIG. 1 is perspective view of an exemplary commercial or
industrial environment that employs a free cooling refrigeration
system.
[0009] FIG. 2 is a diagrammatical overview of an exemplary free
cooling refrigeration system.
[0010] FIG. 3 is an elevational view of the free cooling
refrigeration system shown in FIG. 2.
[0011] FIG. 4 is an elevational view of an exemplary free cooling
refrigeration system employing air-to-liquid heat exchangers that
share a fan.
[0012] FIG. 5 is an elevational view of an exemplary free cooling
refrigeration system employing liquid-to air heat exchangers in a
multi-slab configuration.
[0013] FIG. 6 is a diagrammatical overview of an exemplary free
cooling refrigeration system employing a heat recovery loop.
[0014] FIG. 7 is a diagrammatical overview of another exemplary
free cooling refrigeration system employing a heat recovery
loop.
[0015] FIG. 8 is a diagrammatical overview of an exemplary free
cooling refrigeration system showing an alternate location for the
common heat exchanger.
[0016] FIG. 9 is a diagrammatical overview of an exemplary free
cooling refrigeration system employing two common heat
exchangers.
[0017] FIG. 10 is a diagrammatical overview of an exemplary free
cooling refrigeration system illustrating another pump and valve
configuration.
[0018] FIG. 11 is a diagrammatical overview of an exemplary free
cooling refrigeration system illustrating yet another pump and
valve configuration.
DETAILED DESCRIPTION
[0019] FIG. 1 depicts an exemplary application for a refrigeration
system. Such systems, in general, may be applied in a range of
settings, both within the heating, ventilating, air conditioning,
and refrigeration (HVAC&R) field and outside of that field. The
refrigeration systems may provide cooling to data centers,
electrical devices, freezers, coolers, or other environments
through vapor-compression refrigeration, absorption refrigeration,
or thermoelectric cooling. In presently contemplated applications,
however, refrigeration systems may be used in residential,
commercial, light industrial, industrial, and in any other
application for heating or cooling a volume or enclosure, such as a
residence, building, structure, and so forth. Moreover, the
refrigeration systems may be used in industrial applications, where
appropriate, for basic refrigeration and heating of various
fluids.
[0020] FIG. 1 illustrates an exemplary application, in this case an
HVAC&R system for building environmental management that may
employ heat exchangers. A building 10 is cooled by a system that
includes a chiller 12 and a boiler 14. As shown, chiller 12 is
disposed on the roof of building 10 and boiler 14 is located in the
basement; however, the chiller and boiler may be located in other
equipment rooms or areas next to the building. Chiller 12 is an air
cooled or water cooled device that implements a refrigeration cycle
to cool water. Chiller 12 is housed within a single structure that
includes a refrigeration circuit, a free cooling system, and
associated equipment such as pumps, valves, and piping. For
example, chiller 12 may be single package rooftop unit that
incorporates a free cooling system. Boiler 14 is a closed vessel
that includes a furnace to heat water. The water from chiller 12
and boiler 14 is circulated through building 10 by water conduits
16. Water conduits 16 are routed to air handlers 18, located on
individual floors and within sections of building 10.
[0021] Air handlers 18 are coupled to ductwork 20 that is adapted
to distribute air between the air handlers and may receive air from
an outside intake (not shown). Air handlers 18 include heat
exchangers that circulate cold water from chiller 12 and hot water
from boiler 14 to provide heated or cooled air. Fans, within air
handlers 18, draw air through the heat exchangers and direct the
conditioned air to environments within building 10, such as rooms,
apartments or offices, to maintain the environments at a designated
temperature. A control device, shown here as including a thermostat
22, may be used to designate the temperature of the conditioned
air. Control device 22 also may be used to control the flow of air
through and from air handlers 18. Other devices may, of course, be
included in the system, such as control valves that regulate the
flow of water and pressure and/or temperature transducers or
switches that sense the temperatures and pressures of the water,
the air, and so forth. Moreover, control devices may include
computer systems that are integrated with or separate from other
building control or monitoring systems, and even systems that are
remote from the building.
[0022] FIG. 2 schematically illustrates chiller 12, which
incorporates a free cooling system. As noted above with respect to
FIG. 1, chiller 12 is housed within a single structure and may be
located outside of a building or environment, for example on a roof
top. Chiller 12 includes a cooling fluid loop 24 that circulates a
cooling fluid, such as chilled water, an ethylene glycol-water
solution, brine, or the like, to a cooling load, such as a
building, piece of equipment, or environment. For example, cooling
fluid loop 24 may circulate the cooling fluid to water conduits 16
shown in FIG. 1. Chiller 12 also includes a refrigeration system
loop 26 that is in fluid communication with cooling fluid loop 24
to remove heat from the cooling fluid circulating within the
cooling fluid loop 24. Chiller 12 further includes a free cooling
system 28 that exploits the low temperature of ambient air in order
to cool the cooling fluid circulating within cooling fluid loop 24.
In certain embodiments, the cooling fluid may circulate within the
cooling fluid loop 24 to a cooling load, such as a research
laboratory, computer room, office building, hospital, molding and
extrusion plant, food processing plant, industrial facility,
machine, or any other environments or devices in need of cooling.
Free cooling system 28 includes two circuits 30 and 32 that are
each configured to direct the cooling fluid to different portions
of free cooling system 28. Chiller 12 also includes a control
device 33 that enables chiller 12 to cool the fluid within cooling
fluid loop 24 to a prescribed temperature or prescribed range of
temperatures.
[0023] Chiller 12 may operate in three different modes of operation
depending on the requirements of the cooling load and the
temperature of the ambient air. When the outside air temperature is
low, for example, during winter in northern climates, the chiller
12 may operate in a free cooling mode that directs the cooling
fluid through free cooling system 28 before returning the fluid to
the cooling load. In this mode of operation, the cooling fluid may
be cooled by low temperature outdoor air as the cooling fluid
circulates through circuit 30 of free cooling system 28. If
additional cooling capacity is desired or needed, chiller 12 may
operate in a second mode of operation that employs mechanical
cooling, in addition to the free cooling provided by free cooling
system 28. During mechanical cooling, refrigeration system 26 may
implement a vapor-compression cycle to provide additional cooling
for the cooling fluid. For example, in this mode of operation, the
cooling fluid may first be cooled by low temperature outdoor air as
the cooling fluid circulates through circuit 30 of free cooling
system 28. After exiting free cooling system 28, the cooling fluid
may undergo further cooling by transferring heat to a refrigerant
flowing within refrigeration system 26. To provide even more
cooling capacity, chiller 12 may operate in a third mode of
operation that employs refrigeration system 26 and the second
circuit 32 of the free cooling system 28 to supplement cooling of
refrigerant in refrigeration system 26. In this mode of operation,
the cooling fluid that circulates to the cooling load may be cooled
by refrigerant flowing within refrigeration system 26. Free cooling
system 28 may be used to cool the refrigerant flowing within
refrigeration system 26. Specifically, a portion of the cooling
fluid may be separated from cooling fluid loop 24 and circulated
within circuit 32 of free cooling system 28. The cooling fluid
within circuit 32 may absorb heat from the refrigerant flowing
within refrigeration system 26 to provide additional cooling
capacity.
[0024] Regardless of the mode of operation, chiller 12 may function
to cool the cooling fluid circulating to and from a cooling load,
such as a building. The cooling fluid may enter chiller 12 through
a return line 34 that is in fluid communication with the cooling
load. A pump 36 circulates the cooling fluid through cooling fluid
loop 24 and directs the cooling fluid to a connection point 37 that
fluidly connects free cooling system 28 to cooling fluid loop 24. A
valve 38 may be located at connection point 37 and may direct the
cooling fluid to free cooling system 28. In certain embodiments,
valve 38 may be a three-way servo controlled valve configured to
direct cooling fluid through the free cooling system 28 in one
position and to bypass the free cooling system 28 in another
position. However, in other embodiments, valve 38 may be a ball
valve, rotor valve or the like controlled by electromechanical
actuators, pneumatic actuators, hydraulic actuators, or other
suitable controls.
[0025] The chiller 12 may operate in the first mode, or free
cooling mode, of operation when the ambient air temperature is
sufficiently low enough to provide free cooling. For example,
chiller 12 may operate in the free cooling mode during the winter
when outside temperatures are below approximately 12-15 degrees
Celsius. However, in other embodiments, the cooling mode
determination may depend on a variety of factors such as the
cooling requirement of the cooling load, the outside temperature
and/or humidity, the type of cooling fluid, and the cooling
capacity of the chiller 12 among other things. In the first mode,
valve 38 may direct the cooling fluid through the first circuit 30
of free cooling system 28. Within circuit 30, a pump 39 may
circulate the cooling fluid through free cooling system 28. The
pump may be any suitable type of pump such as a positive
displacement pump, centrifugal pump, or the like. From pump 39, the
cooling fluid may flow through a connection point 40 that
intersects with the second circuit 32 of free cooling system 28.
From connection point 40, the cooling fluid may enter an
air-to-liquid heat exchanger 42. Heat exchanger 42 may include a
fin and tube heat exchanger, brazed aluminum multichannel heat
exchanger, or other suitable heat exchanger. The cooling fluid may
flow through tubes of heat exchanger 42 to transfer heat to the
ambient air. A fan 44, which is driven by a motor 46, draws air
across heat exchanger 42. As the air flows across heat exchanger
42, heat may transfer from the cooling fluid to the air, thereby
cooling the cooling fluid, and producing heated air. Therefore, the
temperature of the cooling fluid exiting heat exchanger 42 may be
less than the temperature of the cooling fluid entering heat
exchanger 42.
[0026] Upon exiting heat exchanger 42, the cooling fluid may flow
to a connection point 48 that connects first circuit 30 with the
second circuit 32. However, the cooling fluid may not flow through
the second circuit in this mode of operation. From connection point
48, the cooling fluid may flow through a connection point 52 to
return to cooling fluid loop 24. The cooling fluid may then
circulate within cooling loop 24 to an evaporator 54. In this first
mode of operation, evaporator 54 may function as a reservoir
without providing any substantial evaporating cooling of the
cooling fluid. From evaporator 54, the cooling fluid may return to
the cooling load through a supply line 56. Supply line 56 may
circulate the cooling fluid to the cooling load where the cooling
fluid may be heated by the cooling load. For example, the cooling
fluid may absorb heat from air within a building or from a fluid
flowing within a device. After receiving heat from the cooling
load, the cooling fluid may enter chiller 12 through return line 34
where the cooling cycle may begin again.
[0027] Chiller 12 may operate in a second mode of operation when
the outside air temperature has increased and/or when the outside
air temperature is not cool enough to provide efficient cooling to
the cooling load. In the second mode of operation, refrigeration
system 26 may implement a vapor-compression cycle, or other type of
cooling cycle, such as absorption or a thermoelectric cycle, to
provide additional cooling for the cooling load. The cooling fluid
may flow through free cooling system 28 as previously described
with respect to the first mode of operation. As the cooling fluid
flows through free cooling system 28, the cooling fluid may
transfer heat to the ambient air through heat exchanger 42. The
cooling fluid, after being cooled by the ambient air, may flow
through connection point 52 and re-enter fluid cooling loop 24.
[0028] The cooling fluid may then flow into evaporator 56 where it
may be cooled by refrigerant from refrigeration system 26.
Evaporator 54 may be a plate heat exchanger, a shell and tube heat
exchanger, a plate and shell heat exchanger, or any other suitable
type of heat exchanger. Evaporator 54 may circulate refrigerant
flowing within a closed loop of refrigeration system 26. The
refrigerant may be any fluid that absorbs and extracts heat. For
example, the refrigerant may be a hydrofluorocarbon (HFC) based
R-410A, R-407C, or R-134a, or it may be carbon dioxide (R-744A) or
ammonia (R-717). As the refrigerant flows through evaporator 54,
the refrigerant may absorb heat from the cooling fluid flowing
within evaporator 54 to cool the cooling fluid before the cooling
fluid returns to the cooling load through supply line 56.
[0029] Within refrigeration system 26, the refrigerant may
circulate through a closed loop including a compressor 58, a heat
exchanger 60, a condenser 62, and an expansion device 63. In
operation, the refrigerant may exit evaporator 54 as a low pressure
and temperature vapor. Compressor 58 may reduce the volume
available for the refrigerant vapor, consequently, increasing the
pressure and temperature of the vapor refrigerant. The compressor
may be any suitable compressor, such as a screw compressor,
reciprocating compressor, rotary compressor, swing link compressor,
scroll compressor, or centrifugal compressor. The compressor 58 may
be driven by a motor that receives power from a variable speed
drive or a direct AC or DC power source. From compressor 58, the
high pressure and temperature vapor may flow through a heat
exchanger 60 that may function as a receiver in this second mode of
operation.
[0030] From heat exchanger 60, the high pressure and temperature
vapor may flow to condenser 62. A fan 64, which is driven by a
motor 66, draws air across the tubes of condenser 62. The fan may
push or pull air across the tubes. As the air flow across the
tubes, heat transfers from the refrigerant vapor to the air,
causing the refrigerant vapor to condense into a liquid and heating
the ambient air. The liquid refrigerant then enters an expansion
device 63 where the refrigerant expands to become a low pressure
and temperature liquid-vapor mixture. Typically, expansion device
63 will be a thermal expansion valve (TXV); however, according to
other exemplary embodiments, the expansion device may be an
electromechanical valve, an orifice, or a capillary tube. From
expansion device 63, the liquid refrigerant may enter evaporator 54
where the process may begin again, and the refrigerant may absorb
heat from the cooling fluid flowing through evaporator 54.
[0031] Refrigeration system 26 generally includes a high-pressure
side and a low-pressure side. The high-pressure side includes the
section of refrigeration system 26 that circulates the
higher-pressure refrigerant (i.e., after compression and before
expansion). Specifically, the high-pressure side includes the
section that circulates the refrigerant from compressor 58 through
heat exchanger 60, condenser 62, and expansion device 63. The
low-pressure side includes the section of refrigeration system 26
that circulates the lower-pressure refrigerant (i.e., after
expansion and before compression). Specifically, the low-pressure
side includes the portion of refrigeration system 26 that
circulates refrigerant from expansion valve 63 through evaporator
54 into compressor 58.
[0032] As described above in the second mode of operation, the
cooling fluid within cooling loop 24 may be cooled by both the free
cooling system 28 and the refrigeration system 26. Specifically,
the free cooling system 28 may circulate the cooling fluid through
the first circuit 30 to transfer heat from the cooling fluid to
ambient air through air-to-liquid heat exchanger 42. After the
cooling fluid has been cooled by the ambient air, the cooling fluid
may then flow through evaporator 54 where the refrigeration system
26 may further remove heat from the cooling fluid by absorbing heat
from the cooling fluid into refrigerant flowing within evaporator
54. In this manner, both free cooling system 28 and the
refrigeration system 26 may be used to provide cooling capacity
during this second mode of operation.
[0033] When even further refrigeration or cooling capacity is
desired, chiller 12 may operate in a third mode of operation
employing supplemental cooling. In this mode, the cooling fluid may
enter chiller 12 through return line 34, flow through pump 36, and
through valve 38 at connection point 37. From valve 38, the cooling
fluid may flow directly to connection point 52, bypassing free
cooling system 28. From connection point 52, the cooling fluid may
flow through evaporator 54 where it may be cooled by the
refrigerant flowing through the refrigeration system 26. In this
third mode of operation, the refrigeration system 26 may receive
supplemental cooling from the cooling fluid flowing through heat
exchanger 60.
[0034] When chiller 12 enters the third mode of operation, a
portion of cooling fluid from cooling fluid loop 24 may be
isolated, or partially isolated, within the second circuit 32 of
free cooling system 28. For example, pump 39 may be disengaged and
pump 68 may be enabled to draw cooling fluid through the second
circuit 32. The second circuit 32 may circulate cooling fluid from
connection point 40 through air-to-liquid heat exchanger 42, pump
68, check valve 70, and heat exchanger 60. As the cooling fluid
flows through heat exchanger 60, the cooling fluid may absorb heat
from the compressed refrigerant exiting compressor 58 and flowing
through heat exchanger 60. Heat exchanger 60 may include a plate
heat exchanger, a shell and tube heat exchanger, a plate and shell
heat exchanger, or any other suitable type of heat exchanger. In
certain embodiments, heat exchanger 60 may function to desuperheat
the compressed refrigerant before it enters condenser 62. By
transferring heat from the refrigerant to the cooling fluid within
the second circuit 32 of free cooling system 28, heat exchanger 60
may provide additional cooling capacity for refrigeration system
26.
[0035] As the cooling fluid flows through heat exchanger 60, the
cooling fluid may absorb heat from the refrigerant, thereby cooling
the refrigerant. The heated cooling fluid may exit heat exchanger
60 and flow through second circuit 32 to connection point 40. From
connection point 40, the heated cooling fluid may flow through
air-to-liquid heat exchanger 42 where the cooling fluid may be
cooled by the ambient air directed through heat exchanger 42 by fan
44. The cooling fluid may then exit heat exchanger 42 and flow
through a pump 68 and valve 70. Pump 68 may include any suitable
type of pump configured to circulate the cooling fluid through
second circuit 32. Valve 70 may include a check valve that prevents
the backward flow of cooling fluid through pump 68. However, in
other embodiments, pump 68 may include a positive displacement pump
with an integrated valve feature that prevents backwards flow. In
this embodiment, valve 70 may be eliminated. Further, in other
embodiments, valve 70 may be a manually actuated valve, solenoid
valve, gate valve, or other suitable type of valve. From valve 70,
the cooling fluid may enter heat exchanger 60 where it may again
absorb heat from the refrigerant circulating within refrigeration
system 26.
[0036] Accordingly, during the third mode of operation, heat
exchanger 60 may be used to transfer heat from refrigeration system
26 to free cooling system 28. Free cooling system 28 may circulate
the heated cooling fluid from heat exchanger 60 to air-to-liquid
heat exchanger 42 to expel the heat into the environment. In this
manner, air-to-liquid heat exchanger 42 may be used by chiller 12
to remove heat from the system even when the system is not
operating in a free cooling mode. For example, second circuit 32
may be used to remove heat from refrigeration system 26 even when
environmental air temperatures may be higher then the chilled water
supply temperature. Specifically, even though the ambient air
temperature may be high, for example above 70 degrees Fahrenheit,
the ambient air temperature still may be lower than the temperature
of the high pressure and temperature refrigerant flowing within the
refrigeration system 26. This temperature difference may enable
air-to-liquid heat exchanger 42 to transfer heat from refrigeration
system 26 to the environment, thereby increasing the cooling
capacity of refrigeration system 26.
[0037] The operation of chiller 12 may be governed by control
devices 33, which include control circuitry 72 and temperature
sensors 74 and 76. Circuitry 72 may be coupled to valve 38 and
pumps 39 and 68, which drive the first and second circuits 30 and
32, respectively. Control circuitry 72 may use information received
from sensors 74 and 76 to determine when to operate pumps 39 and
68. In some applications, control circuit 72 also may be coupled to
motors 46 and 66, which drive fans 44 and 64, respectively. In some
applications, control circuit 72 may include local or remote
command devices, computer systems and processors, and/or
mechanical, electrical, and electromechanical devices that manually
or automatically set a temperature related signal that a system
receives.
[0038] Control circuitry 72 may be configured to switch chiller 12
between the first, second, and third modes of operation based on
input received from temperature sensors 74 and 76. Temperature
sensor 74 may sense the temperature of the ambient outside air and
temperature sensor 76 may sense the temperature of the cooling
fluid returning from the cooling load. For example, temperature
sensor 76 may be disposed within cooling loop 24. In certain
embodiments, when the ambient air temperature sensed by sensor 74
is below the cooling fluid temperature sensed by temperature sensor
76, control circuitry 72 may set chiller 12 to operate in a first
mode of operation that employs free cooling by circulating the
cooling fluid through the first circuit 30 of free cooling system
28. For example, control circuitry 72 may set valve 38 to direct
cooling fluid through free cooling system 28 and may disable pump
68 and compressor 58. Control circuitry 72 may operate chiller 12
in the first mode of operation until the temperature of the ambient
air reaches a specified value or is a certain amount above the
temperature of the cooling fluid. Control circuitry 72 may then set
chiller 12 to operate in the second mode of operation that employs
refrigeration system 26, in addition to circulating the cooling
fluid through the first circuit 30 of cooling system 28. In certain
embodiments, control circuitry 72 may enable compressor 58 and
motor 66 to circulate refrigerant through refrigeration system 26.
Control circuitry 72 may operate chiller 12 in the second mode of
operation until the ambient air temperature reaches another
specified value or amount above the cooling fluid temperature or
until the cooling fluid temperature rises above a certain
threshold. Control circuitry 72 may then switch chiller 12 to the
third mode of operation that employs the second circuit 32 of free
cooling system 28 to remove heat from refrigeration system 26. For
example, control circuitry 72 may then disable pump 39 and enable
pump 68 to circulate a portion of the cooling fluid through the
second circuit 32.
[0039] The control circuitry may be based on various types of
control logic that uses input from temperature sensors 74 and 76.
Control circuitry 72 also may control other valves and pumps
disposed within the refrigeration system. Further, additional
inputs such as flow rates, pressures, and other temperature may be
used in controlling the operation of chiller 12. For example, other
devices may be included in chiller 12, such as additional pressure
and/or temperature transducers or switches that sense temperatures
and pressures of the refrigerant and cooling fluid, the heat
exchangers, the inlet and outlet air, and so forth. Further, the
examples provided for determining the mode of operation are not
intended to be limiting. Other values and set points based on a
variety of factors such as system capacity, cooling load, and the
like may be used to switch chiller 12 between the first, second,
and third modes of operation.
[0040] The pump and valve configurations included in FIG. 2 are
shown by way of example only and are not intended to be limiting.
For example, the locations, numbers, and types of pumps and valves
may vary. In one example, pump 39 may be eliminated and pump 36 may
circulate the cooling fluid through free cooling system 28. Pump 39
also may be located anywhere within first circuit 30, and pump 68
may be located anywhere within second circuit 32. In certain
embodiments, valve 38 may be eliminated, if, for example, pump 39
is equipped with a positive shutoff feature. In another example,
pumps 68 and 39 may be equipped with positive shutoff features and
valves 70 and 38 may be eliminated. In yet another example, valve
38 may be located at connection point 40, 48, or 52. Further valve
38 may be replaced by two two-way valves. For example, in one
embodiment, a first two-way valve may be located between connection
points 38 and 40 or between connection points 48 and 52 and a
second two-way valve may be located between connection points 38
and 52. Of course, many other pump and valve configurations may be
envisaged and employed in chiller 12.
[0041] FIG. 3 is an elevational view of chiller 12. Chiller 12 may
be housed completely within a single cabinet or support frame 78.
In certain embodiments, support frame 78 may be a box-shaped
structure composed of metal panels. Control circuit 72 may be
mounted on support frame 78 that houses equipment 80, such as
pumps, compressors, heat exchangers, valves, piping, and the like,
included within chiller 12. In certain embodiments, the
air-to-liquid heat exchangers 42 and 62 may be disposed in adjacent
V-shaped configurations within support frame 78. Each heat
exchanger 42 and 62 may include two heat exchanger slabs disposed
beneath fans 44 and 64. However, in other embodiments, the number
of slabs within each heat exchanger may vary. Further, additional
heat exchanger slabs may be connected in series to provide
additional cooling capacity. In certain embodiments, the free
cooling system heat exchanger 42 may be disposed towards the
outside of the cabinet 78 such that the heat exchanger 42 may
receive the coolest environmental air.
[0042] FIG. 4 shows an alternate heat exchanger configuration for
chiller 12. In this configuration, heat exchangers 42 and 62 share
a common fan 82. The heat exchangers may be disposed in a V-shaped
configuration with air-to-liquid heat exchanger 42 on one side and
condenser 62 on the other side. Shared fan 82 may draw air over
both heat exchangers 42 and 62. In certain embodiments, the use of
a common fan configuration may reduce equipment costs.
[0043] FIG. 5 illustrates another heat exchanger configuration,
where air-to-liquid heat exchanger 42 and condenser 62 are disposed
in a multi-slab configuration to share common fan 82. In this
configuration, the slabs of each heat exchanger 42 and 62 are
disposed adjacent to each other. However, the configurations
illustrated in FIGS. 3 through 5 are provided by way of example
only and are not intended to be limiting. For example, depending on
factors such as system capacity, cooling load requirements, piping
configurations, climate temperatures, and average humidity, among
other things, the number of slabs within heat exchangers 42 and 62
may vary. Further, multiple slabs may be connected in series to
provide additional cooling capacity. Moreover, the heat exchangers
may include various multi-slab configurations, additional V-shaped
configurations, and additional heat exchangers.
[0044] FIG. 6 illustrates another exemplary chiller 84 that
includes free cooling system 28, cooling loop 24, and refrigeration
system 26. Chiller 84 also includes a heat recovery loop 86
disposed within the second circuit 32 of free cooling system 28.
The heat recovery loop 86 includes a closed loop that circulates
through a heat exchanger 88 located within second circuit 32. Heat
exchanger 88 allows heat to be transferred from the cooling fluid
flowing within second circuit 32 to a device 89 in fluid
communication with heat recovery loop 86. Device 89 may be any
device that utilizes an input of heat. For example, device 89 may
be a water heater, space heater, or other device. A pump 90
circulates a fluid, such as water or any suitable refrigerant,
within closed loop 86. As the fluid flows through device 89, for
example, within a coil disposed in device 89, the fluid may
transfer heat to an interior volume of device 89. In certain
embodiments, pump 90 may be controlled by control circuitry 72 and
enabled to provide heat to device 89 when chiller 84 is operating
in the third mode of operation. Further, in certain embodiments,
device 89 may be housed outside of chiller 84 and connected to the
chiller via piping. Moreover, additional equipment, such as bypass
valve, pumps, and the like, may be included in the chiller 84.
[0045] FIG. 7 illustrates another chiller 91 that includes an
alternate heat recovery loop 92. Heat recovery loop 92 is in fluid
communication with second circuit 32 and includes a three-way valve
93 configured to direct cooling fluid exiting heat exchanger 60
through heat recovery loop 92. The cooling fluid may be circulated
through valve 93 to a device 94 to transfer heat from the cooling
fluid to device 94. Device 94 may be any device that utilizes input
of heat, such as a water heater, space heater, or other suitable
device. In certain embodiments, control circuitry 72 may be
connected to valve 93 to govern operation of valve 93. When heat is
required within device 94, the valve 93 may be set to direct fluid
to heat recovery loop 92. However, when no heat input is desired,
the valve 93 may be set to bypass heat recovery loop 92. In certain
embodiments, heat recovery loop 92 may be used to provide reheat
for humidity control within a system. For example, device 94 may be
an air duct within a building where air is cooled below a set point
to reduce humidity. The cooled air may be reheated by heat recovery
loop 92. In other embodiments, device 94 may be a water heater or a
space heater. Moreover, additional equipment, such as bypass valve,
pumps, and the like, may be included in the chiller 91.
[0046] FIG. 8 illustrates another exemplary chiller 98 that
includes a heat exchanger 100 for transferring heat from
refrigeration system 26 to free cooling system 28. Heat exchanger
100 is located downstream of condenser 62 and may be employed when
chiller 98 is operating in the third mode of operation. Heat
exchanger 100 may receive condensed, or partially condensed,
refrigerant from condenser 62 and may function to further condense
and/or subcool the refrigerant by transferring heat from the
refrigerant to the cooling fluid circulating within the second
circuit 32 of free cooling system 28.
[0047] FIG. 9 illustrates yet another exemplary chiller 102 that
employs two heat exchangers 104 and 106 that may transfer heat from
refrigeration system 26 to the second circuit 32 of free cooling
system 28. Heat exchanger 106 is located upstream of condenser 62
and may desuperheat the compressed refrigerant exiting condenser
58. From heat exchanger 106, the refrigerant may enter condenser
62, where the refrigerant may be condensed, or partially condensed.
Heat exchanger 104 is located downstream of condenser 62 and may
further condense and/or subcool the refrigerant exiting condenser
62.
[0048] As the refrigerant flows through heat exchangers 104 and
106, the refrigerant may transfer heat to the cooling fluid within
circuit 32. Chiller 102 is configured so that heat exchanger 104
receives the cooling fluid from air-to-liquid heat exchanger 42
before directing the cooling fluid to heat exchanger 106. In this
manner, the relatively cooler cooling fluid may be used for
subcooling the condensed, or partially condensed, refrigerant
exiting condenser 62. After the cooling fluid has been heated by
flowing through heat exchanger 104, the relatively warmer cooling
fluid may be used to desuperheat the higher temperature refrigerant
entering condenser 62. In other embodiments, however, the chiller
may be configured so heat exchanger 106 receives the cooling fluid
before heat exchanger 104.
[0049] As described above with respect to FIG. 2, various pump and
valve configurations may be employed within the chiller. FIG. 10
illustrates another exemplary chiller 108 incorporating an
alternate pump and valve configuration. A pump 110 may be disposed
within part of the free cooling system that is common to the first
and second circuits 30 and 32 so that only one pump may be employed
in free cooling system 28. A two-way valve 112 may be located
within the second circuit 32 and another two-way valve 114 may be
located within the first circuit 30. Two-way valves 112 and 114 may
be connected to control circuitry 72 to selectively direct the
cooling fluid to either first circuit 30 or second circuit 32,
depending on the mode of operation. When the system is operating in
the first or second modes of operation that employ free cooling,
valves 112 and 114 may be configured to circulate cooling fluid
thought the first circuit 30 as described above with respect to
FIG. 2. When the system is operating in the third mode of operation
to remove heat from refrigeration system 26, valves 112 and 114 may
be configured to circulate a portion of the cooling fluid within
the second circuit 32. Pump 110 may be disposed at the exit of
air-to-liquid heat exchanger 42. Of course, the locations of pump
110 and valves 112 and 114 may vary. For example, in other
embodiments, pump 110 may be located at the entrance to
air-to-liquid heat exchanger 42. In another example, valve 114 may
be located between connection points 39 and 40. Further, additional
pumps, valves, sensors, transducers, and the like may be included
within the exemplary chiller systems described herein.
[0050] FIG. 11 illustrates yet another exemplary chiller 116
incorporating an alternate pump and valve configuration that
employs an expansion tank 118. Expansion tank 118 is located within
the second circuit 32 of free cooling system 38 and may allow for
thermal expansion when a portion of the cooling fluid is circulated
within the second circuit 32 during the third mode of operation.
Expansion tank 118 may be any suitable type of tank or vessel, and
may normally include trapped gas to accommodate changes in liquid
volume. A check valve 120 is disposed within the first circuit 30
to prevent the cooling fluid from flowing backwards through free
cooling system 28. As described above with respect to FIG. 2,
three-way valve 38 may direct cooling fluid into free cooling
system 28. During the first and second modes of operation, the
cooling fluid may flow through the first circuit 30 of free cooling
system 28 as described above with respect to FIG. 2. During the
third mode of operation, a portion of the cooling fluid may be
isolated within the second circuit 32 and pump 68 may be engaged to
circulate the isolated cooling fluid through the second circuit 32
to remove heat from refrigeration system 26. As the temperature
changes and the cooling fluid expands or contracts, a portion of
the cooling fluid may be stored, or circulated within, expansion
tank 118. In other embodiments, the expansion tank may be disposed
within any portion of the second circuit 32. Further, the location
of the valves may vary. For example, in certain embodiments, a
three-way valve may be located at connection point 52 and check
valve 120 may be located between connection points 39 and 40.
[0051] While only certain features and embodiments of the invention
have been illustrated and described, many modifications and changes
may occur to those skilled in the art (e.g., variations in sizes,
dimensions, structures, shapes and proportions of the various
elements, values of parameters (e.g., temperatures, pressures,
etc.), mounting arrangements, use of materials, colors,
orientations, etc.) without materially departing from the novel
teachings and advantages of the subject matter recited in the
claims. The order or sequence of any process or method steps may be
varied or re-sequenced according to alternative embodiments. It is,
therefore, to be understood that the appended claims are intended
to cover all such modifications and changes as fall within the true
spirit of the invention. Furthermore, in an effort to provide a
concise description of the exemplary embodiments, all features of
an actual implementation may not have been described (i.e., those
unrelated to the presently contemplated best mode of carrying out
the invention, or those unrelated to enabling the claimed
invention). It should be appreciated that in the development of any
such actual implementation, as in any engineering or design
project, numerous implementation specific decisions may be made.
Such a development effort might be complex and time consuming, but
would nevertheless be a routine undertaking of design, fabrication,
and manufacture for those of ordinary skill having the benefit of
this disclosure, without undue experimentation.
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