U.S. patent application number 11/504382 was filed with the patent office on 2008-02-21 for method and apparatus for cooling.
This patent application is currently assigned to American Power Conversion Corporation. Invention is credited to Ozan Tutunoglu.
Application Number | 20080041077 11/504382 |
Document ID | / |
Family ID | 39100053 |
Filed Date | 2008-02-21 |
United States Patent
Application |
20080041077 |
Kind Code |
A1 |
Tutunoglu; Ozan |
February 21, 2008 |
Method and apparatus for cooling
Abstract
A cooling unit includes a first module having a first intake
opening and a first exhaust opening formed therein. At least one
first air moving device may be configured to draw air along a first
flow path from the first intake opening to the first exhaust
opening. A first heat exchanger may be positioned in the first flow
path. The cooling unit may further include a second module having a
second intake opening and a second exhaust opening. At least one
second air moving device may be configured to draw air along a
second flow path from the second intake opening and direct air to
the second exhaust opening. A second heat exchanger may be
positioned in the second flow path. A conduit system is in fluid
communication with the first heat exchanger and the second heat
exchanger. The conduit system may be configured to deliver coolant
from the first heat exchanger of the first module to the second
heat exchanger of the second module and from the second heat
exchanger of the second module to the first heat exchanger of the
first module. Methods of cooling a space with a cooling unit are
further disclosed.
Inventors: |
Tutunoglu; Ozan; (O'Fallon,
MO) |
Correspondence
Address: |
LOWRIE, LANDO & ANASTASI, LLP
ONE MAIN STREET, SUITE 1100
CAMBRIDGE
MA
02142
US
|
Assignee: |
American Power Conversion
Corporation
West Kingston
RI
|
Family ID: |
39100053 |
Appl. No.: |
11/504382 |
Filed: |
August 15, 2006 |
Current U.S.
Class: |
62/186 ;
62/259.2 |
Current CPC
Class: |
H05K 7/20827 20130101;
H05K 7/20836 20130101; F25D 19/00 20130101 |
Class at
Publication: |
62/186 ;
62/259.2 |
International
Class: |
F25D 17/04 20060101
F25D017/04; F25D 23/12 20060101 F25D023/12 |
Claims
1. A cooling unit comprising: a first module including a first
intake opening and a first exhaust opening formed therein, at least
one first air moving device configured to draw air along a first
flow path from the first intake opening to the first exhaust
opening, and a first heat exchanger positioned in the first flow
path; a second module including a second intake opening and a
second exhaust opening, at least one second air moving device
configured to draw air along a second flow path from the second
intake opening and direct air to the second exhaust opening, and a
second heat exchanger positioned in the second flow path; and a
conduit system in fluid communication with the first heat exchanger
and the second heat exchanger, the conduit system being configured
to deliver coolant from the first heat exchanger of the first
module to the second heat exchanger of the second module and from
the second heat exchanger of the second module to the first heat
exchanger of the first module.
2. The cooling unit of claim 1, wherein the first module and the
second module are contained within a housing, and wherein the first
module is positioned over the second module.
3. The cooling unit of claim 2, further comprising a tray to
support the at least one first air moving device of the first
module, the tray being releasably secured to the housing.
4. The cooling unit of claim 3, wherein the tray is disposed on a
generally horizontal plane.
5. The cooling unit of claim 4, wherein the at least one first air
moving device of the first module includes a fan, and wherein the
tray is configured to receive at least one fan.
6. The cooling unit of claim 5, further comprising a control device
coupled to the fan.
7. The cooling unit of claim 6, wherein the fan is a variable speed
fan, and wherein the control device is configured to control the
speed of the fan.
8. The cooling unit of claim 4, wherein the first module comprises
a first plenum disposed along a generally vertical axis in fluid
communication with the first intake opening, and a second plenum
disposed along a generally horizontal axis and configured to direct
air from the first plenum to the tray.
9. The cooling unit of claim 4, further comprising at least one
support rail configured to secure the tray to the first module.
10. The cooling unit of claim 1, wherein the first module comprises
a top having the first intake opening and the first exhaust opening
formed therein, a first plenum disposed along a generally vertical
axis in fluid communication with the first intake opening, and a
second plenum disposed along a generally horizontal axis and
configured to direct air taken from the first plenum to the at
least one first air moving device of the first module, and wherein
the second module comprises a first side having the second intake
opening and a second side, opposite the first side, having the
second exhaust opening, the arrangement being such that the first
flow path is along a generally horizontal axis.
11. The cooling unit of claim 10, wherein the first heat exchanger
of the first module is disposed at an acute angle with respect to
the flow of air from the second plenum to the first exhaust opening
of the first module, and wherein the second heat exchanger of the
second module is disposed at an acute angle with respect to the
flow of air from the first side to the second side of the second
module.
12. The cooling unit of claim 1, wherein the first heat exchanger
comprises a condenser unit, and wherein the second heat exchanger
comprises an evaporator unit.
13. The cooling unit of claim 12, further comprising a compressor
to deliver coolant to the condenser unit.
14. The cooling unit of claim 13, further comprising a bypass valve
provided in the conduit system, the bypass valve being configured
to divert a portion of coolant from the compressor to the
evaporator unit.
15. The cooling unit of claim 12, further comprising an expansion
valve, disposed between the condenser unit and the evaporator
unit.
16. A cooling unit comprising: a housing having a top with an
intake opening and at least one exhaust opening formed therein; at
least one air moving device configured to be coupled to the housing
and configured to draw air along a flow path from the intake
opening to the at least one exhaust opening; a heat exchanger
configured to be coupled to the housing between the at least one
air moving device and the at least one exhaust opening within the
flow path; and a conduit system in fluid communication with the
heat exchanger, the conduit system being configured to deliver
coolant to the heat exchanger, wherein coolant flowing through the
heat exchanger is adapted to be cooled by the heat exchanger.
17. The cooling unit of claim 16, further comprising a tray to
support the at least one air moving device, the tray being
releasably secured to the housing.
18. The cooling unit of claim 17, wherein the tray is disposed on a
generally horizontal plane.
19. The cooling unit of claim 18, wherein the at least one air
moving device includes a fan, and wherein the tray is configured to
receive at least one fan.
20. The cooling unit of claim 19, further comprising a control
device coupled to the fan.
21. The cooling unit of claim 20, wherein the fan is a variable
speed fan, and wherein the control device is configured to detect a
speed of each fan.
22. The cooling unit of claim 18, wherein the housing comprises a
first plenum disposed along a generally vertical axis in fluid
communication with the intake opening, and a second plenum disposed
along a generally horizontal axis and configured to direct air
taken from the first plenum to the tray, the first and second
plenums defining the flow path, wherein air being directed by the
at least one air moving device over the heat exchanger is
heated.
23. The cooling unit of claim 18, further comprising at least one
support rail configured to releasably secure the tray to the
housing.
24. The cooling unit of claim 16, wherein the heat exchanger is
disposed at an acute angle with respect to the flow of air to the
at least one exhaust opening.
25. A method of cooling a space with a modular cooling unit, the
method comprising: drawing air into a first module of the cooling
unit; directing the air over a first heat exchanger of the first
module of the cooling unit to cool coolant flowing through the
first heat exchanger; exhausting the air out of the first module of
the cooling unit; directing the cooled coolant from the first heat
exchanger to a second heat exchanger; drawing air into a second
module of the cooling unit; directing the air over the second heat
exchanger of the second module of the cooling unit to cool the air;
and exhausting the cooled air out of the second module of the
cooling unit.
26. The method of claim 25, further comprising positioning the
first module on top of the second module.
27. The method of claim 26, wherein drawing air into the first
module includes drawing air from a top of the first module, and
wherein drawing air into the second module includes drawing air
from a side of the second module.
28. The method of claim 25, the method further comprising directing
coolant from the second heat exchanger to the first heat
exchanger.
29. The method of claim 28, the method further comprising diverting
a portion of coolant being directed from the second heat exchanger
to the first heat exchanger back to the second heat exchanger.
30. A cooling unit comprising: a housing; a compressor coupled to
the housing; a first heat exchanger coupled to the housing; at
least one first air moving device coupled to the housing and
configured to direct air along a first flow path, the first heat
exchanger being located along the first flow path; a second heat
exchanger coupled to the housing; at least one second air moving
device coupled to the housing and configured to direct air along a
second flow path, the second heat exchanger being located along the
second flow path; a conduit system in fluid communication with the
compressor, the first heat exchanger, the second heat exchanger,
and back to the compressor; and a bypass valve provided in the
conduit system, the bypass valve being configured to divert a
portion of coolant from the compressor to the second heat
exchanger.
31. The cooling unit of claim 30, wherein the first heat exchanger
comprises a condenser unit, and wherein the second heat exchanger
comprises an evaporator unit.
Description
BACKGROUND OF INVENTION
[0001] 1. Field of Invention
[0002] Embodiments of the invention relate generally to devices and
methods for cooling a room, such as a data center, equipment room
or wiring closet. Specifically, aspects of the present invention
relate to data centers containing racks and enclosures used to
house data processing, networking and telecommunications equipment,
and more particularly to cooling systems and methods used to cool
equipment housed by such racks and enclosures.
[0003] 2. Discussion of Related Art
[0004] Over the years, a number of different standards have been
developed to enable equipment manufacturers to design rack
mountable equipment that can be mounted in standard racks
manufactured by different manufacturers. A standard rack typically
includes front mounting rails to which multiple units of electronic
equipment, such as servers and CPUs, are mounted and stacked
vertically within the rack. An exemplary industry standard rack is
approximately six to six-and-a-half feet high, by about twenty-four
inches wide, and about forty inches deep. Such a rack is commonly
referred to as a "nineteen inch" rack, as defined by the
Electronics Industries Association's EIA-310-D standard.
[0005] Nineteen inch racks are used extensively in the data centers
and other large facilities described above. With the proliferation
of the Internet, it is not uncommon for a data center to contain
hundreds of these racks. Further, with the ever decreasing size of
computer equipment, and in particular, computer servers and blades,
the number of electrical devices mounted in each rack has been
increasing, raising concerns about adequately cooling the
equipment.
[0006] Heat produced by rack-mounted equipment can have adverse
effects on the performance, reliability and useful life of the
equipment components. In particular, rack-mounted equipment, housed
within an enclosure, may be vulnerable to heat build-up and hot
spots produced within the confines of the enclosure during
operation. The amount of heat generated by a rack of equipment is
dependent on the amount of electrical power drawn by equipment in
the rack during operation. In addition, users of electronic
equipment may add, remove, and rearrange rack-mounted components as
their needs change and new needs develop.
[0007] Previously, in certain configurations, data centers have
been cooled by computer room air conditioner ("CRAC") units that
are typically hard piped, immobile units positioned around the
periphery of the data center room. These CRAC units intake air from
the fronts of the units and output cooler air upwardly toward the
ceiling of the data center room. In other embodiments, the CRAC
units intake air from near the ceiling of the data center room and
discharge cooler air under a raised floor for delivery to the
fronts of the equipment racks. In general, such CRAC units intake
room temperature air (at about 72.degree. F.) and discharge cold
air (at about 55.degree. F.), which is blown into the data center
room and mixed with the room temperature air at or near the
equipment racks.
[0008] The rack-mounted equipment typically cools itself by drawing
air along a front side or air inlet side of a rack, drawing the air
through its components, and subsequently exhausting the air from a
rear or vent side of the rack. A disadvantage of the CRAC-type air
conditioning system is that cool air is mixed with the room
temperature air, which is inefficient. Ideally, to make the system
as efficient as possible, and to utilize as little energy and floor
space as possible, the highest possible temperature air should be
drawn into the CRAC units and the outlet air generated by the CRAC
should be a few degrees below room temperature. In addition,
airflow requirements can vary considerably as a result of different
numbers and types of rack-mounted components and different
configurations of racks and enclosures.
[0009] For large data centers requiring CRAC units at or near the
middle or center of the data center room, delivery of coolant to
the CRAC units must be located within the raised floor since it is
undesirable to secure coolant piping to the ceiling of the data
center due to risks involved with the possible failure of the
piping joints. Specifically, with traditional CRAC systems, the
piping of the units requires significant cutting and hand soldering
of pipes. Leaks are common and leaking water or coolant in a data
center may result in risk of damage to equipment housed within the
equipment racks. For at least these reasons, most data center
designers and operators are unwilling to consider overhead piping
for cooling a data center.
SUMMARY OF INVENTION
[0010] One aspect of the invention is directed to a cooling unit
comprising a first module including a first intake opening and a
first exhaust opening formed therein. At least one first air moving
device may be configured to draw air along a first flow path from
the first intake opening to the first exhaust opening. A first heat
exchanger may be positioned in the first flow path. The cooling
unit may further comprise a second module including a second intake
opening and a second exhaust opening. At least one second air
moving device may be configured to draw air along a second flow
path from the second intake opening and direct air to the second
exhaust opening. A second heat exchanger may be positioned in the
second flow path. A conduit system is in fluid communication with
the first heat exchanger and the second heat exchanger. The conduit
system may be configured to deliver coolant from the first heat
exchanger of the first module to the second heat exchanger of the
second module and from the second heat exchanger of the second
module to the first heat exchanger of the first module.
[0011] In one embodiment, the first module and the second module
may be contained within a housing, with the first module being
positioned over the second module. The cooling unit may further
comprise a tray to support the at least one first air moving device
of the first module, with the tray being releasably secured to the
housing. In a certain embodiment, the tray may be disposed on a
generally horizontal plane and supported by at least one support
rail configured to secure the tray to the first module. The
arrangement is such that the at least one first air moving device
of the first module includes a fan, and the tray is configured to
receive at one fan. The cooling unit may be configured to comprise
a control device coupled to the fan. In one embodiment, the fan is
a variable speed fan, and the control device is configured to
control the speed of the fan. The first module may comprise a first
plenum disposed along a generally vertical axis in fluid
communication with the first intake opening, and a second plenum
disposed along a generally horizontal axis and configured to direct
air from the first plenum to the tray. The first module may further
comprise a top having the first intake opening and the first
exhaust opening formed therein, a first plenum disposed along a
generally vertical axis in fluid communication with the first
intake opening, and a second plenum disposed along a generally
horizontal axis and configured to direct air taken from the first
plenum to the at least one first air moving device of the first
module. The second module may further comprise a first side having
the second intake opening and a second side, opposite the first
side, having the second exhaust opening. The arrangement is such
that the first flow path is along a generally horizontal axis. In
another embodiment, the first heat exchanger of the first module is
disposed at an acute angle with respect to the flow of air from the
second plenum to the first exhaust opening of the first module, and
the second heat exchanger of the second module is disposed at an
acute angle with respect to the flow of air from the first side to
the second side of the second module. The first heat exchanger may
comprise a condenser unit, and the second heat exchanger may
comprise an evaporator unit. The cooling unit may be further
configured to comprise a compressor to deliver coolant to the
condenser unit and a bypass valve provided in the conduit system.
The bypass valve may be configured to divert a portion of coolant
from the compressor to the evaporator unit. In a certain
embodiment, an expansion valve is disposed between the condenser
unit and the evaporator unit.
[0012] Another aspect of the invention is directed to a cooling
unit comprising a housing having a top with an intake opening and
at least one exhaust opening formed therein. At least one air
moving device may be configured to be coupled to the housing to
draw air along a flow path from the intake opening to the at least
one exhaust opening. A heat exchanger may be configured to be
coupled to the housing between the at least one air moving device
and the at least one exhaust opening within the flow path. A
conduit system, in fluid communication with the heat exchanger, may
be configured to deliver coolant to the heat exchanger. Coolant
flowing through the heat exchanger may be adapted to be cooled by
the heat exchanger.
[0013] In a certain embodiment, a tray may be provided to support
the at least one air moving device, the tray being releasably
secured to the housing. The tray may be disposed on a generally
horizontal plane by at least one support rail configured to
releasably secure the tray to the housing. The at least one air
moving device may include a fan and the tray may be configured to
receive at least one fan. A control device may be coupled to the
fan. In one embodiment, the fan is a variable speed fan and the
control device is configured to detect a speed of each fan. The
housing may comprise a first plenum disposed along a generally
vertical axis in fluid communication with the intake opening, and a
second plenum disposed along a generally horizontal axis and
configured to direct air taken from the first plenum to the tray,
the first and second plenums defining the flow path. Air that is
directed by the at least one air moving device over the heat
exchanger is heated. The heat exchanger may be disposed at an acute
angle with respect to the flow of air to the at least one exhaust
opening.
[0014] A further aspect of the invention is directed to a method of
cooling a space with a modular cooling unit. The method may
comprise: drawing air into a first module of the cooling unit;
directing the air over a first heat exchanger of the first module
of the cooling unit to cool coolant flowing through the first heat
exchanger; exhausting the air out of the first module of the
cooling unit; directing the cooled coolant from the first heat
exchanger to a second heat exchanger; drawing air into a second
module of the cooling unit; directing the air over the second heat
exchanger of the second module of the cooling unit to cool the air;
and exhausting the cooled air out of the second module of the
cooling unit. In one embodiment, the method may further comprise
positioning the first module on top of the second module. Drawing
air into the first module may include drawing air from a top of the
first module, and drawing air into the second module may include
drawing air from a side of the second module. The method may
further comprise directing coolant from the second heat exchanger
to the first heat exchanger and diverting a portion of coolant
being directed from the second heat exchanger to the first heat
exchanger back to the second heat exchanger.
[0015] In yet another embodiment, a cooling unit comprises a
housing, a compressor coupled to the housing, a first heat
exchanger coupled to the housing, and at least one first air moving
device coupled to the housing and configured to direct air along a
first flow path. The first heat exchanger may be located along the
first flow path. A second heat exchanger may be coupled to the
housing. At least one second air moving device may be coupled to
the housing and configured to direct air along a second flow path.
The second heat exchanger is located along the second flow path. A
conduit system may provide fluid communication between the
compressor, the first heat exchanger, the second heat exchanger,
and the compressor. A bypass valve may be provided in the conduit
system. The bypass valve may be configured to divert a portion of
coolant from the compressor to the second heat exchanger. In one
embodiment, the first heat exchanger comprises a condenser unit and
the second heat exchanger comprises an evaporator unit.
BRIEF DESCRIPTION OF DRAWINGS
[0016] The accompanying drawings, are not intended to be drawn to
scale. In the drawings, each identical or nearly identical
component that is illustrated in various figures is represented by
a like numeral. For purposes of clarity, not every component may be
labeled in every drawing. In the drawings:
[0017] FIG. 1 is a perspective view of a cooling unit of an
embodiment of the present invention;
[0018] FIG. 2 is a perspective view of components of the cooling
unit shown in FIG. 1;
[0019] FIG. 3 is a front elevational view of the cooling unit with
a front panel of the cooling unit removed;
[0020] FIG. 4 is a view similar to FIG. 3 illustrating a bottom air
blocking panel removed;
[0021] FIG. 5 is a perspective view of the cooling unit shown in
FIG. 4 with a fan tray assembly partially removed from the cooling
unit;
[0022] FIG. 6 is a perspective view similar to FIG. 1 with side
panels of the cooling unit removed;
[0023] FIG. 7 is a system block diagram of the cooling unit of an
embodiment of the invention;
[0024] FIG. 8 is a system block diagram of the operational states
and modes of the cooling unit;
[0025] FIG. 9 is a system block diagram of the condensate
state;
[0026] FIG. 10 is a system block diagram of the hot gas bypass
valve state;
[0027] FIG. 11 is a system block diagram of the hot gas bypass
valve control;
[0028] FIG. 12 is a system block diagram of the condenser fans
speed control;
[0029] FIG. 13 is a system block diagram of the evaporator fans
speed control; and
[0030] FIGS. 14-17 are flow charts showing the calculation of
cooling capacity using equations of embodiments of the
invention.
DETAILED DESCRIPTION
[0031] This invention is not limited in its application to the
details of construction and the arrangement of components set forth
in the following description or illustrated in the drawings. The
invention is capable of other embodiments and of being practiced or
of being carried out in various ways. Also, the phraseology and
terminology used herein is for the purpose of description and
should not be regarded as limiting. The use of "including,"
"comprising," or "having," "containing", "involving", and
variations thereof herein, is meant to encompass the items listed
thereafter and equivalents thereof as well as additional items.
[0032] At least one embodiment of the present invention is directed
to a modular cooling system that is selectively configurable to
cool electronic equipment housed within equipment enclosures or
racks of a data center. As used herein, "enclosures" and "racks"
are used to describe apparatus designed to support electronic
equipment. Such a cooling system is capable of employing one or
more cooling units on an as needed basis to provide localized
cooling within the data center. Specifically, multiple cooling
units may be interspersed in a row of equipment racks to more
efficiently cool the data center. The circulation path of warm air
generated by the electronic equipment is greatly reduced, thereby
nearly eliminating the mixing of hot and cold air within the data
center.
[0033] Data centers are typically large rooms designed, in certain
instances, to house hundreds of electronic equipment racks arranged
in rows within the data center. The rows of equipment racks are
arranged in such a manner that there are cold aisles and hot
aisles. The cold aisles provide access to the fronts of the
enclosures where the electronic equipment is typically accessed.
The hot aisles provide access to the backs of the equipment racks.
As requirements change, the number of equipment racks may be
increased or decreased depending on the functional requirements of
the data center. At least one embodiment of the cooling system is
modular and scalable, and may take the form of a kit designed to
meet these changing needs. Also, although relatively large data
centers are discussed as an intended use for such a cooling system,
as mentioned above, the system of the present invention is scalable
and may be employed in smaller rooms on a smaller scale and for
applications other than data center.
[0034] In one embodiment, the cooling system may comprise a
plurality of cooling units, each cooling unit having a housing
adapted to support components of the cooling system. For example,
the components of the cooling unit may include first and second
heat exchangers coupled to a conduit system configured to deliver
coolant to the heat exchangers. Fans may be provided to move air
across the heat exchangers. The cooling unit may be disposed within
a row of equipment racks and configured to intake the hot air
within the data center from a hot aisle, for example, to cool the
air to slightly below ambient temperature. This configuration
eliminates the inefficiency of mixing hot air with the room
temperature air to obtain a warm air mixture. This configuration
may also decrease the latent cooling provided by the data center's
air conditioning system thereby decreasing the need for
humidification.
[0035] In certain embodiments, the components of the cooling unit
may be provided in kit form so that the person installing the
cooling unit does not require specialized tools. The modular nature
of the cooling unit allows the user to optimize the location of
each cooling unit since each cooling unit includes the ability to
sense and display the capacity of the system, the flow rate,
coolant and air inlet and outlet temperatures, and pressure
differentials obtained from pressure readings taken throughout the
cooling unit. Thus, the cooling unit may be employed and redeployed
for maximum efficiency and optimal use within the data center.
[0036] A typical data center includes a room designed to house a
plurality of equipment racks. In one embodiment, each equipment
rack may be constructed in accordance with the teachings disclosed
in U.S. patent application Ser. No. 10/990,927, entitled EQUIPMENT
ENCLOSURE KIT AND ASSEMBLY METHOD, filed on Nov. 17, 2004, which is
owned by the assignee of the present invention and is incorporated
herein by reference. Further, cabling between the equipment racks
may be implemented using cable distribution troughs contained on
the roofs of the racks as disclosed in U.S. Pat. No. 6,967,283,
which is incorporated herein by reference and assigned to the
assignee of the present invention.
[0037] Specifically, the equipment rack includes a frame or housing
adapted to support electronic components, such as data processing,
networking and telecommunications equipment. The housing includes
front, back, sides, bottom and top. The front of each equipment
rack may include a front door so as to enable access into the
interior of the equipment rack. A lock may be provided to prevent
access into the interior of the equipment rack and the equipment
housed by the rack. The sides of the equipment rack may include at
least one panel configured to cover a side to enclose the interior
region of the rack. The back of the equipment rack may also include
at least one panel or a back door to provide access to the interior
of the equipment rack from the back of the rack. In certain
embodiments, the side and back panels, as well as the front door
and the rear door, may be fabricated from perforated sheet metal,
for example, to allow air to flow into and out of the interior
region of the equipment rack. Otherwise, the panels may be
fabricated from solid material.
[0038] The equipment racks are modular in construction and
configured to be rolled into and out of position, e.g., within a
row of the data center. Casters are secured to the bottom of each
equipment rack to enable the rack to roll along the floor of the
data center. Once positioned, leveling feet may be deployed to
securely ground the equipment rack in place within the row. An
example of casters and leveling feet employed on such an equipment
rack is disclosed in detail in U.S. patent application Ser. No.
10/990,927.
[0039] Once in position, electronic equipment may be positioned in
the interior region of the equipment rack. For example, the
equipment may be placed on shelving secured within the interior
region of the equipment rack. Cables providing electrical and data
communication may be provided through the top of the equipment rack
either through a cover (or "roof" as described in U.S. Pat. No.
6,967,283) at the top of the equipment rack having openings formed
therein or through an open top of the equipment rack. In this
embodiment, the cables may be strung along the roofs of the rack or
be provided in the aforementioned cable distribution trough. In
another embodiment, the cables may be disposed within a raised
floor and connected to the electronic equipment through the bottom
of the equipment rack. With both configurations, power and
communication lines are provided to the equipment racks.
[0040] As discussed above, data centers are typically configured
with rows of equipment racks arranged such that cool air is drawn
into the racks from a cool aisle and warm or hot air is exhausted
from the racks into a hot aisle. The equipment racks may be
arranged in two rows with the fronts of the equipment racks in a
near row being arranged in a forward direction and the backs of the
equipment racks in a far row being arranged in a rearward
direction. However, as stated above, in a typical data center,
there are multiple rows of equipment racks wherein the rows may be
arranged with the fronts of the equipment racks facing one another
to define the cold aisle and with the backs of the equipment racks
facing one another to define the hot aisle.
[0041] In order to address the heat build-up and hot spots within
the data center, and to address climate control issues within the
data center in general, a modular cooling unit is provided in one
embodiment. As discussed above, due to cooling requirements within
the data center or room, a plurality of cooling units may be
provided. In one embodiment, the arrangement is such that there is
a cooling unit for every two equipment racks provided in the data
center. However, it should be understood that a person of ordinary
skill in the art, given the benefit of this disclosure, may provide
more or less cooling units within the data center based on
environmental conditions of the data center. Further in some
embodiments, the concentration and locations of cooling units may
be adjusted based on the locations of the hottest racks in the data
center, or based on information obtained and analyzed by a data
center information management system. Additionally, cooling units
of embodiments of the invention may be used in combination with
other types of cooling systems, such as cooling systems of the
types disclosed in U.S. patent application Ser. Nos. 11/335,874,
11/335,856 and 11/335,901, each entitled COOLING SYSTEM AND METHOD
and filed on Feb. 10, 2006, which are owned by the assignee of the
present invention and incorporated herein by reference.
[0042] A cooling unit of embodiments of the invention may be
configured to have two sections or modules, which together define a
closed loop cooling system that may be configured within a data
center, equipment room or wiring closet to cool electrical
components housed by equipment storage racks. In one embodiment, a
lower module of the cooling unit includes a set of evaporator fans
that are configured to draw heated air taken from a "hot" aisle,
for example, which is generated by the electrical components. This
heated air is drawn through an evaporator having a coil containing
a coolant medium (e.g., a refrigerant) to cool the air. The
arrangement is such that warm air drawn into the lower module by
the evaporator fans flows over the evaporator to cool the air. The
cooled air is forced back into the environment through a front of
the cooling unit. Based on cooling requirements, other airflow
patterns may be provided.
[0043] The heat absorbed by the coolant contained in the coil of
the evaporator is transported to an upper module, which rests on
the lower module. This upper module has a condenser adapted to cool
the heated coolant delivered to the upper module from the lower
module. In addition to the condenser, the upper module includes a
set of condenser fans and a first, generally vertical plenum that
is in fluid communication with an opening formed in a top of the
upper module to draw relatively cooler air into the upper module. A
second, generally horizontal plenum takes air directed by the first
plenum to the set of condenser fans, which directs the air over the
condenser. The relatively cooler air is heated as it flows over the
condenser. Once heated, the air flows through one of two openings
formed in the top of the upper module. The liquid coolant is
directed back to the evaporator, where the cycle begins again. A
compressor, such as a rotary compressor, pumps evaporated coolant
from the evaporator to the condenser. The compressor, evaporator
fans and condenser fans are all controlled by a controller. In one
embodiment, to improve capacity control and efficiency, warmer
coolant being delivered by the compressor unit to the condenser may
be diverted to the evaporator by a bypass valve.
[0044] It should be understood that, in embodiments of the
invention, the lower module may be configured to perform the
condensing function described above and the lower module may be
configured to perform the evaporating function described above.
[0045] In one embodiment, the controller is adapted to control the
operation of the cooling system based on environmental parameters
obtained by the controller. Generally speaking with prior cooling
systems, the individual cooling units can not communicate with one
another. For example, the controller may embody a plurality of
controllers provided in the cooling units that communicate with one
another over a controller area network (CAN) Bus. In other
embodiments, a master controller may be provided to control the
operation of the controllers of the cooling units. Each cooling
unit may be provided with a display, which is operably coupled to
the controller. The display is adapted to display the environmental
conditions of the data room, such as, and not limited to, the
temperature and the humidity of the data center at the cooling
unit, the temperature of the air entering into and exiting out of
the cooling unit, the temperature of coolant entering into and
exiting out of the cooling unit, the flow rate of coolant entering
the cooling unit, and the cooling capacity of the cooling unit.
Suitable monitors and/or gauges may be provided to acquire such
information. Alternatively, or in addition to the foregoing
embodiment, the environmental conditions may be displayed on a unit
provided with an integrated data center control and monitoring
system.
[0046] Referring now to FIGS. 1-6, and more particularly to FIG. 1,
there is generally indicated at 10 a cooling unit of an embodiment
of the invention. As shown, the cooling unit 10 comprises a lower
module 12 and an upper module 14 configured to treat air within a
room. In one embodiment, the cooling unit 10 includes a frame or
housing 16, which may be configured in two separate housings
forming the frames of the lower and upper modules, or as a single,
unitary housing. The cooling unit 10 includes a front 18, a back
20, opposite sides 22, 24, a bottom 26 and a top 28. Each side 22,
24 of the cooling unit may include at least one panel (not
designated) configured to cover the side to enclose the interior
region of the cooling unit. The front and the back of the cooling
unit may include at least one removable panel or door to provide
access to the interior of the cooling unit. In certain embodiments,
the front and back panels may be fabricated from perforated sheet
metal, for example, to allow air to flow into and out of the
interior region of the cooling unit. Casters and leveling feet
(both not shown) may be provided to enhance the mobility of the
cooling unit and to set the cooling unit in a secure position.
Other details of the cooling unit 10 shown in FIG. 1 will be
discussed in greater detail below as the description of the cooling
unit proceeds.
[0047] Turning to FIG. 2, the internal components of the cooling
unit 10 are illustrated without showing the housing 16 and panels
of the cooling unit. The components of the cooling unit 10 are
suitably secured to and contained within the housing 16 of the
cooling unit in the manner shown and described herein. The air flow
within the cooling unit will be discussed in greater detail below
with reference to other drawings, including FIG. 6 in particular.
One purpose of FIG. 2 is to illustrate the flow of a coolant medium
(e.g., a liquid coolant, such as R134A and R410A coolants) through
the working components of the cooling unit.
[0048] As shown, a compressor 30 is provided for delivering hot gas
coolant under pressure to the components of the cooling unit 10.
The pressurized coolant travels through a discharge pipe 32, which
connects the compressor 30 to a condenser 34. A temperature sensor
(not shown) and a first pressure transducer 36 may be provided
adjacent to the condenser 34 to measure the temperature and the
pressure of the coolant as it enters the condenser. The purpose of
the temperature sensor and the pressure transducer 36 will be
discussed in greater detail below. A high pressure switch 38 may be
further provided to de-energize the compressor thereby stopping the
delivery of coolant to the condenser should the coolant experience
an out of tolerance pressure condition that requires power to the
compressor to be cut off. The condenser 34 includes a coil 40
having thermally conductive fins (not shown) configured to cool the
heated coolant within the coil of the condenser. The air flow over
the condenser coil 40 will be discussed in greater detail below
with reference to drawings directed to the air flow configuration
of the cooling unit 10 (e.g., FIG. 6). Once the coolant is cooled
within the condenser 34 (e.g., transitioning the coolant from an
evaporated state to a condensed state), the coolant travels through
another liquid pipe 42 to an evaporator 44. The coolant first
travels through a filter drier 46 to eliminate impurities and to
remove unwanted non-condensables within the coolant. Once through
the filter drier 46, the coolant travels through a thermal
expansion valve 48 to condition the coolant prior to entering the
evaporator 44.
[0049] Next, the low pressure coolant enters a distributor 50 and
is distributed to the evaporator by one of several (e.g., three)
conduits, each indicated at 52 in FIG. 2. As shown, one conduit 52
delivers coolant to the evaporator 44 near the top of the
evaporator. A second conduit 52 delivers coolant to a middle of the
evaporator 44. And finally, a third conduit 52 delivers coolant to
a bottom of the evaporator 44. This configuration ensures that
coolant is evenly distributed to the evaporator 44, which is
designed to include a coil 54 in thermal communication with metal
fins (not shown) so that heat may be absorbed from relatively warm
air flowing over the evaporator. Once heated by warm air passing
over the evaporator 44, the evaporated coolant travels back to the
compressor 30 via a section of suction piping 56. However, prior to
entering the compressor 30, the coolant passes through a compressor
suction accumulator 58, which ensures that coolant enters into the
compressor 30 in an evaporated state. Another temperature sensor 60
and another pressure transducer 62 may be provided adjacent to the
compressor 30, the purpose of which will be discussed in greater
detail below. A condensate pan 35 may be disposed below the
evaporator 44 to collect condensate generated by the
evaporator.
[0050] The arrangement is such that high temperature coolant flows
from the compressor 30 to the condenser 34. Pressure and
temperature readings of the coolant are taken prior to the coolant
entering the condenser 34. The condenser 34 cools the coolant by
virtue of relatively cool air passing over the condenser coil 40.
Once cooled, the coolant travels to the evaporator 44. A bypass
valve 64 may be provided to divert coolant normally directed to the
condenser 34 from the compressor 30 to the evaporator 44 via a
discharge pipe 66. By opening the bypass valve 64, a portion of
coolant traveling to the condenser is diverted to the evaporator by
way of distributor 50. The operation of the bypass valve 64, which
may sometimes be referred to as a hot gas bypass valve, may be
manipulated to regulate the capacity of the cooling unit 10. As
will be discussed in greater detail below, by closely monitoring
the pressure and/or temperature of the coolant entering into the
condenser 34, the efficiency of the cooling unit 10 may be
optimized by bypassing coolant that travels from the condenser to
the evaporator. In one embodiment, the compressor may embody a
rotary compressor, such as a 208-230/1/50 or 208-230/1/60 rotary
compressor offered by Carrier of Syracuse, N.Y. When employing a
rotary compressor, the pressure differential between the
evaporating pressure and the condensing pressure, in certain
embodiments, must be less than a predetermined pressure difference,
such as 7.2 psig, to restart the compressor. To expedite the
pressure equalization between evaporating and condensing pressures,
the hot gas bypass valve 64 may be open until the compressor
re-starts.
[0051] Referring to FIGS. 3-6, and more particularly to FIG. 6, the
lower module 12 has a plurality of evaporator fans (sometimes
referred to herein as air moving devices), each indicated at 68,
which are located at the front of the lower module of the cooling
unit 10. The arrangement is such that air may be drawn from the
back of the lower module 12 of the cooling unit over the evaporator
44 through either an open back or through perforations in a back
panel by the evaporator fans 68. In one embodiment, there may be
three such fans 68 (as shown) to draw air through the lower module
12 in the manner shown in FIG. 6. However, any number of fans 68
may be employed, depending on the size of the fans and on how much
air is required to be drawn across the evaporator 44. In one
embodiment, the evaporator fans 68 may be 200 mm mixed flow fans
provided by EBM Industries of Farmington, CT. The evaporator fans
68 may be configured as part of a fan tray arrangement secured
vertically to the front 18 of the cooling unit 10, or be secured
individually to the housing 16 at the front 18 of the cooling unit.
As shown best in FIG. 6, the air drawn through the lower module by
the evaporator fans 68 (indicated by arrows A) flows over the coil
and the fins of the evaporator 44 to heat the coolant flowing
through the coil. The resultant is that cool air is blown out of
the evaporator fans 68 at the front of the cooling unit 10 to cool
the space adjacent the front of the cooling unit.
[0052] In one embodiment, one or more cooling units 10 may be
positioned so that the backs 20 of the cooling units are adjacent a
hot aisle. Depending on the cooling requirements of the data
center, more than one cooling unit 10 may be provided to cool warm
air deposited in the hot aisle by the equipment enclosures.
[0053] In a particular configuration, the upper module 14 of the
cooling unit 10 may be configured to include the top 28 of the
cooling unit, which has three openings formed therein.
Specifically, there may be provided an intake opening 70 and two
exhaust openings 72, 74 in the top 28 of the cooling unit 10. As
best shown in FIG. 6, an interior wall 76 and a blocking panel 78
define a first plenum 80 that extends along a generally vertical
axis. The first plenum 80 is in fluid communication with the intake
opening 70 to draw air from the intake opening to a second plenum
82 located along a generally horizontal axis at the bottom of the
upper module 14.
[0054] Further provided in the upper module 14 is a tray 84 that is
releasably secured to the housing of the cooling unit 10, the tray
having three condenser fans, each indicated at 86, secured thereto.
The arrangement is such that the tray 84 and the condenser fans 86
are disposed along a generally horizontal plane to define an upper
wall of the second plenum 82. The condenser fans 86 are configured
to draw relatively cool air from the first plenum 80 to the second
plenum 82 and blow the air across the condenser 34 so as to cool
coolant running through the condenser coil. Air flows through the
condenser 34 and out of the two exhaust openings 72, 74 formed in
the top 28 of the upper module 14 of the cooling unit 10. The
airflow path through the upper module 14 is depicted by arrows B in
FIG. 6. In one embodiment, the exhaust openings 72, 74 may be in
fluid communication with exhaust ducts (not shown) to transfer the
warm air out of the data center or room. In another embodiment, the
air may be directed to the top of the data center or room, away
from the equipment enclosures. In a further embodiment one exhaust
opening or more than two exhaust openings may be provided. It
should be understood that one skilled in the art, given the benefit
of this disclosure, may configure the cooling unit in any desired
manner consistent with the teachings herein.
[0055] As shown best in FIG. 6, the condenser fans 86 draw air from
the intake opening 70 along a first flow path defined by the first
and second plenums 80, 82 to the exhaust openings 72, 74, as
indicated by arrows B. As shown in dashed lines, air may also be
drawn from a dropped ceiling arrangement. The condenser 34 is
positioned within the upper module 14 at an acute angle with
respect to the first flow path. The evaporator fans 68 draw air
from the intake opening defined by the open end 20 of the lower
module 12 of the cooling unit 10 along a second flow path shown by
arrows A to an exhaust opening defined by the opposite open end 18
of the lower module of the cooling unit. The evaporator 44 is
positioned within the lower module 12 at an acute angle with
respect to the second flow path. In the claims, the upper module 14
may be referred to as a first module and the lower module 12 may be
referred to as a second module. The acute angles of the condenser
34 and the evaporator 44 may be selected to maximize the surface
areas of the condenser and the evaporator, respectively.
[0056] In one embodiment, a controller may be operably coupled to a
display unit 88 (see FIG. 1), such as a display unit shown and
disclosed in U.S. patent application Ser. Nos. 11/335,874,
11/335,856 and 11/335,901 discussed above. In a certain embodiment,
the display unit 88 has a liquid crystal display, for example, to
display certain environmental conditions, such as temperature and
humidity of the data center, the temperature of air entering into
and exiting out of the cooling unit, the temperature of coolant
entering into and exiting out of the evaporator and condenser of
the cooling unit, and the flow rate of coolant within the cooling
unit. A plurality of control buttons and status indicators are
further provided on the display unit 88 to enable the operator to
manipulate the operation of the cooling system and to quickly
determine the status of a certain condition, respectively. As
shown, the display unit 88 may be secured to the front 18 of the
cooling unit 10 within an opening formed in the front of the
cooling unit by means of a sealing gasket and a mounting bracket in
which screw fasteners may be provided to secure the display
assembly to the front panel within the opening.
[0057] FIGS. 3-5 illustrate the removal of the tray 84 having the
condenser fans 86. Specifically, FIG. 3 illustrates the front panel
or door of the cooling unit 10 removed from the cooling unit. As
shown, the display unit 88 is secured to the housing 16 of the
cooling unit. In a configuration having only one panel, the panel
and the display unit 88 may be removed either together or
separately, depending on the particular design. In the shown
embodiment, at least two air blocking panels, 90, 92 are secured to
the housing 16 of the cooling unit 10 to contain air within the
upper module 14 of the cooling unit. FIG. 4 illustrates the lower
air blocking panel 90 removed so that the second plenum 82 of the
cooling unit is revealed. Once the lower air blocking panel 90 is
removed, the fan tray 84 may be removed from the housing 16 of the
cooling unit 10 by simply pulling the fan tray from the front of
the cooling unit 10. The fan tray 84 is configured to rest on a
pair of support rails 94, 96, which are secured to the housing 16
within the upper module 14 of the cooling unit 10. The condenser
fans 86, as well as the evaporator fans 68, may be variable speed
fans that are independently operable under the control of a
controller. The arrangement is such that the fan tray 84 may be
easily removed from the cooling unit 10 to replace or repair a fan,
for example.
[0058] In other embodiments, as described above, the panels 90 and
92 may be combined to create a single panel. With this
configuration, the display unit 88 must be separately removed so as
to access the fan tray 84.
[0059] As mentioned above, a controller may be configured to
control the operation of the cooling unit 10 as well as provide
communication with external devices. In one embodiment, the
controller may be a separately dedicated unit that controls the
operation of multiple cooling units 10. In another embodiment, the
controller may be provided in one of the cooling units 10, with the
cooling unit having the controller functioning as the main cooling
unit and the other cooling units functioning as subservient cooling
units. In yet another embodiment, the operation of the cooling unit
10 may be operated under the control of an integrated data center
control and monitoring system with each cooling unit having a
controller unit that communicates with the other cooling units over
the network. In one such embodiment, the controller may communicate
with a data center control system to provide status of the
components of the cooling system and to receive control commands
for the data center control system. In one particular embodiment
each cooling unit 10 includes a controller that communicates with
the data center controller over a network, such as a CAN Bus
network, and in one such embodiment, the data center controller may
be implemented using the integrated data center control and
monitoring system, such as the InfraStruXure.TM. data center
manager sold by American Power Conversion Corporation of West
Kingston, R.I., the assignee of the present invention.
Notwithstanding the particular configuration, the controller is
adapted to control the flow of coolant from the compressor 30 to
the condenser 34 and the evaporator 44 depending on the temperature
and pressure readings of the cooling unit.
[0060] FIG. 7 illustrates a system block diagram of the cooling
unit 10, showing the major interfaces between the cooling unit and
potential external devices. As shown, a heat load 98 is applied to
the cooling unit 10 in which a temperature sensor 100 detects and
transmits a signal to an embedded controller 102 of the cooling
unit. In one embodiment, the embedded controller 102 may be a
Philips XAG49 microprocessor (running at 16 MHz, 512 Kbytes of
flash memory, 128 Kbytes of battery backed static RAM, 16 Kbytes of
EEPROM, and having a real-time clock). As shown, the embedded
controller 102 may communicate with a network manager 104 by means
of a CAN, for example. The network manager 104 may communicate with
the display unit 88, a building management system 106, if provided,
a data center manager 108 by means of a local area network 110
(LAN), for example, or a local test port 112. In a certain
embodiment, the network manager may employ a network management
card containing ASIC, 4 Mbytes of static RAM, 16 Kbytes of EEPROM,
a real time clock and a CAN controller. In one embodiment, the ASIC
includes an Intel 186 microprocessor, running at 50 MHz, and a
10/100 Base-T network interface controller (NIC).
[0061] During operation, the cooling unit 10 may be configured to
function between several states, including, but not limited to, a
main operational state, a condensate state and a hot gas bypass
valve state. In the main operational state, which is illustrated in
FIG. 8, the operation of the cooling unit proceeds as follows: (a)
un-powered; (b) start-up delay; (c) off/standby; (d) idle
operation; (e) failed operation; (f) warm-up operation; (g) running
operation; (h) firmware download; and (i) test. Specifically, once
power is provided, the cooling unit operationally moves from an
un-powered condition at 114 to an initial powered condition at 116
in which initialized state variables are set. Once initialized, the
cooling unit moves to a start-up delay condition at 118 in which no
action is taken. After a predetermined time period (as determined
by a delay timer, for example) and the synchronization of a stepper
motor, the cooling unit transitions to an off/standby condition at
120 in which the hot gas bypass valve is fully opened. In this
condition, the temperature and discharge pressure threshold alarms
are disabled (except when employing a rack containment system,
wherein only the temperature threshold alarms are disabled) and the
fan speeds (evaporator and condenser) are set to idle (except when
employing a rack containment system or when the machine is in
proportional spot configuration mode wherein the fans are kept
running at a minimum speed). In the off/standby mode 120, the
cooling unit 10 is ready for operation.
[0062] As shown, the mode of operation may transition from either
the off/standby condition 120 or an idle operation mode 122 to a
pre-run operation mode at 124. The transition occurs if all of the
following conditions are met: (1) the delay timer is not running;
(2) the device has been commanded upon by the controller; (3) the
suction and discharge pressures are equalized; (4) there is no idle
requested due to a leak; and (5) the cooling unit inlet
temperature, when employing in-row or air containment
configurations, or return air temperature, when employing a spot
cooling configuration, exceeds a predetermined cool set point and a
dead band (i.e., a tolerance that prevents the unwanted transition
to back to off/standby or idle modes). The transition to pre-run
operation mode 124 may also occur when the forgoing transition does
not occur, and the device has been commanded upon the controller.
When in idle operation mode 122, the transition may also occur when
(1) the delay timer is not running, (2) the suction pressure is
above a predetermined threshold, e.g., 92 psig, (3) the condensate
pan is not full, (4) there is no idle requested due to a leak, (5)
the line pressure has equalized, and (6) the cooling unit inlet
temperature (for in-row or containment configurations) or return
air temperature (for spot cooling configurations) exceeds the
predetermined cool set point and dead band.
[0063] During pre-run mode 124, the hot gas bypass valve is fully
closed to clear any events that are no longer active. The
temperature and discharge pressure threshold alarms are enabled and
the evaporator and condenser fans are operated at full (maximum)
speed. A delay timer is set for a predetermined time period, e.g.,
twenty seconds. When warming up at 126, the cooling unit is
providing environmental control functionality in which the
compressor is running. In this state, the evaporator and condenser
fans are run at full (maximum) speed and the bypass valve is closed
to allow the system to warm up and stabilize prior to attempting to
control the system. Once warmed up, the cooling unit may be
operated at 128 to provide the cooling operation described above.
If failure occurs, which is indicated at 130 in FIG. 8, at either
at the pre-run 124, warm-up 126 or running 128 modes, the pre-run
routine 124 may be started again. The cooling unit may be further
configured to conduct firmware download operations at 132 and
manufacturing testing at 134, either during operation, or while
powering up.
[0064] Transition to idle mode 122 may occur when upon one of the
following events: (1) the condensate pan is full; (2) if there is
an idle requested due to leak; (3) when employing a spot cooling
configuration, the return air temperature is less than or equal to
the cool set point; (4) when employing an in-row or containment
system configurations, the cooling unit inlet temperature is below
a cool set point, e.g., 90.degree. F.-sec; (5) if high head
pressure input is asserted (and not the third such event in thirty
minutes); or (6) suction pressure is below a predetermined
threshold, e.g., 92 psig (and not the third such event in thirty
minutes). Transition from either warm-up mode 126 or running mode
128 to failure mode 130 may occur when the cooling unit is
commanded upon by the controller and an analog sensor has failed,
or there were three high head pressure events in thirty minutes,
for example, or there were three low suction pressure events in
thirty minutes, for example.
[0065] In one embodiment, transition from failure mode 130 to
pre-run mode 124 may occur when all of the following conditions are
met: (1) the cooling unit is commanded upon by the controller; (2)
the delay timer is not running; (3) the condensate pan is not full;
(4) no analog sensors have failed; (5) the three high head pressure
in thirty minutes event is cleared, for example; and (6) the three
low suction pressure in thirty minutes event is clear, for example.
Transition back to off/standby mode 120 may occur when the unit is
commanded upon by the controller. Transition from warm-up mode 126
to idle mode 122 may occur upon one of the following events: (1) if
the condensate pan is full; (2) there is an idle requested due to
leak; (3) when in discrete mode, the return air temperature is less
than or equal to the cool set point, or, when in proportional mode,
the rack inlet temperature is below the cool set point for
90.degree. F.-sec, for example; or (4) if the high head pressure
input is asserted and it is not the third such event in thirty
minutes.
[0066] Referring to FIGS. 9 and 10, the condensate state mode is
illustrated in FIG. 9 and the hot gas bypass valve state mode is
illustrated in FIG. 10. With particular reference to FIG. 9, when
referencing the condensate state, the cooling unit transitions from
an un-powered condition at 140 to a powered condition at 142. Once
powered on, a normal condensate level is indicated at 144. When the
condensate pan becomes full, the condition of the cooling unit
transitions from the normal mode 144 to a full mode 146. When in
full mode 146, a signal may be transmitted to the controller or
some other visual or audible alarm to discharge the condensate pan.
When a predetermined period of time expires, e.g., ten minutes, the
state of the cooling unit transitions to a full timeout mode at
148. All other failures are indicated at 150 in FIG. 9. For
example, fail mode 150 may be triggered when a sensor, e.g., a
float sensor, fails to deliver a signal to the controller. As with
mode 148, upon the expiration of a predetermined period of time,
e.g., ten minutes, the state of the cooling unit transitions to a
full timeout mode at 152. The failures indicated at 146, 148, 150
and 152 may be cured in which the cooling unit returns to its
normal state at 144.
[0067] With reference to FIG. 10, when referencing the hot gas
bypass valve state, the cooling unit transitions from an un-powered
condition at 160 to a powered condition at 162. Once powered on, a
command is issued (e.g., by the controller or network manager) to
the bypass valve to a synchronized closed position at 164 in which
a delay timer is set. Once synchronized, indicated at 166 in FIG.
10, the cooling unit transitions to a post-synchronized mode at 168
in which the bypass valve is reset to a position where it was
before synchronization, if commanded by the controller or network
manager. Upon a predetermined delay as determined by the delay
timer, for example, the mode transitions from 168 to a ready mode
at 170 in which the bypass valve position is recorded and
re-commanded to synchronize. From this position, the cooling unit
transitions back to mode 166 in which the bypass valve receives a
command to synchronize. This command may include how long to keep
the bypass valve closed and whether to return the valve to the
previous position after synchronization.
[0068] While operating, the cooling unit 10 is configured to
provide the system operator with the ability to set the operating
environment to one of the following: spot cooling within a space;
hot aisle cooling within a row of equipment racks; or rack air
containment cooling, which is described in U.S. patent application
Ser. Nos. 11/335,874, 11/335,856 and 11/335,901 discussed above.
When configured for spot cooling, the controller may be selected to
one of the following control methods: proportional control, which
modulates the bypass valve and fan speeds at certain set points and
dead bands; or discrete control (e.g., energy saving), which closes
the bypass valve and the compressor runs when the return or remote
air temperature at the cooling unit exceeds a certain threshold.
When employing a remote air sensor in in-row configurations, the
sensor is located adjacent the front of the rack. The compressor is
turned off when the temperature at the cooling unit is less than or
equal to the threshold temperature. When configured for hot aisle
and cold aisle environments, the proportional control method may be
employed. Similarly, when configured for rack air containment, the
proportional control method may be used. When in operation, the
cooling unit may be configured to protect and maximize the life of
the compressor.
[0069] The controller and/or system manager of the cooling unit 10
may be configured to monitor and control other aspects of the
cooling unit. For example, the controller and/or system manager may
be configured to monitor and control power management, event
management, user interfaces, testing requirements, condensate
monitoring, leak monitoring, run hour counters, maintenance alarms,
fault alarms and user inputs and outputs.
[0070] Specifically, with certain prior art cooling systems, the
compressor has a tendency to cycle on and off during operation,
thereby creating a situation in which hot air flows from the hot
aisle to the cold aisle since the evaporator fans are operating
when the compressor is turned off. As discussed above, in order to
address unwanted cycling of the compressor, the cooling unit 10
includes the bypass valve 64 and evaporator fans 68. In a certain
embodiment, the bypass valve 64 is an electronic expansion valve
offered by Sporlan Division of Parker-Hannifin Corporation of
Washington, MO. The temperature of air entering into the lower
module 12 may be monitored and used as a set temperature. Cooling
capacity control may be achieved in one of three modes. They are:
(1) spot-proportional mode (e.g., in a data closet); (2) in-row
mode (e.g., in hot aisle/cold aisle applications within a data
center); and (3) rack air containment systems (RACS; e.g., in
enclosed systems having at least one equipment rack and at least
one cooling unit).
[0071] In circumstances where the cooling load is minimal, the
temperature of the air entering the cooling unit 10 may drop so
that the temperature approximates the unit's set temperature. In
circumstances where the air temperature entering into the lower
module 12 approaches the set temperature, the cooling unit's
cooling capacity is reduced by bypassing hot gas back to the
evaporator 44 with the bypass valve 64 via conduit 66. There are
two methods used to reduce (or regulate) the cooling unit's cooling
capacity. They are: (1) use of the hot gas bypass valve; and (2)
use of the variable evaporator fan speed and the hot gas bypass
valve together.
[0072] In another embodiment, by reducing the speed of the
evaporator fans, the capacity of the cooling unit 10 is reduced.
This results in the reduction of supply air temperatures, with the
bypass valve regulating supply air temperature in proportional
mode. Specifically, in a particular embodiment, the default supply
air set point in spot-proportional modes may be 57.degree. F. In
another particular embodiment, the default supply air set point in
in-row and containment air system mode may be 68.degree. F. As
discussed above, the temperature sensor e.g., sensor 60, installed
within the system adjacent the input of the compressor 30 may
monitor the return gas temperature of coolant entering into the
compressor. To keep the return coolant less than a predetermined
temperature (e.g., 68.degree. F.) so as to ensure the protection of
the compressor 30, the bypass valve 64 may be throttled and the
evaporator fan speed may be reduced, even when there is a demand
for coolant bypass.
[0073] Under certain circumstances, while the bypass valve 64
bypasses hot gas coolant, coolant velocities within the pipes are
reduced. This reduction of coolant velocities may limit the ability
of compressor oil contained within the coolant from returning to
the compressor 30. As is well known, a predetermined amount of oil
may be provided in the coolant to protect the working components of
the compressor 30. In a certain embodiment, the bypass valve 64 may
be configured to close for a short period of time, e.g.,
approximately ten seconds, every twenty minutes or so when the
bypass valve is operating in an open position. By closing the
bypass valve 64 periodically for a short duration, relatively high
coolant velocities may be achieved within the pipes so that any oil
trapped within the pipes is forced back to the compressor 30.
[0074] During operation, low evaporating temperatures may be
encountered in systems in which the filter drier 46 or an air
filter become clogged, thus reducing the cooling capacity of the
cooling unit 10. Low evaporating temperatures may reach a critical
condition and cause damage to the compressor 30 by virtue of liquid
coolant entering into the compressor. In one embodiment, to
alleviate this potential concern, the evaporator fans 68 of the
cooling unit 10, as discussed above, may embody multiple (e.g.,
three) variable speed, DC fans that work with the pressure
transducer 62 located adjacent the accumulator 58. The pressure
transducer 62 is configured to obtain an evaporating pressure
reading of the coolant entering into the compressor 30. In one
example, when the evaporating temperature drops below a
predetermined temperature, e.g., 40.degree. F., for example, as
detected by the pressure transducer 62, a saturation temperature of
the coolant is determined from a look up table embedded in the
firmware of the controller. The temperature sensor 60 measures
return gas temperature flowing to the compressor 30. The cooling
unit 10 will increase evaporator air flow rate by increasing the
speed of the evaporator fans 68 via a program control loop (e.g., a
PID control loop) written in the firmware of the controller. If
increasing the evaporator air flow rate (by increasing evaporator
fan speed) does not result in the increase of the evaporating
coolant temperature, and the temperature drops below a second
predetermined temperature, 37.degree. F., for example, the bypass
valve 64 will bypass coolant hot gas to increase the evaporating
temperature. The controller may be configured to trigger an alarm
if the evaporating temperature drops below a third predetermined
temperature, e.g., 34.degree. F.
[0075] Conversely, the cooling unit 10 of embodiments of the
invention may also be configured to address the issue of high
return coolant gas temperatures entering into the compressor 30 as
a result of high heat loads in the data center or equipment room.
Such high temperatures may reduce the life of the compressor 30 or
cause compressor damage if prolonged. In one embodiment, the
cooling unit 10 may be configured so that the temperature sensor 60
adjacent the compressor 30 detects coolant temperature entering the
compressor. When the coolant gas temperature reaches a
predetermined temperature, e.g., 68.degree. F., the controller may
reduce the evaporator air flow by decreasing the speed of the
evaporator fan speed 68 via a control loop (e.g., a PID loop)
written in the firmware of the controller.
[0076] In certain environments, it may be difficult to control the
air temperature entering the condenser through the intake opening
70 when the data center or equipment room includes a dropped
ceiling or when hoses or ducts are used to move air to ambient
since there is no temperature control within a dropped ceiling
configuration. This restriction may result in low air temperatures
being exerted on the condenser 34 and thus low coolant temperatures
being generated by the condenser. In certain conditions, extremely
low condensing temperatures may cause the coolant to flood back to
the compressor 30 in liquid condition and damage the compressor. In
one embodiment, the condenser fans 86 may embody three variable
speed DC condenser fans that operate in cooperation with the
pressure transducer 36 adjacent the condenser 34. In other
embodiments, the condenser fans may be AC with VFD or SC PSC with a
sine wave chopper. The condensing temperature may be calculated
from readings taken from the pressure transducer 36 or from the
temperature sensor. The controller may be configured to maintain
the temperature above a predetermined temperature, e.g., 95.degree.
F., for example, by a control loop (e.g., a PID loop) written in
the firmware of the controller. In another embodiment, the
discharge pressure of coolant discharged by the condenser 34
through discharge pipe 42 may be monitored to control the condenser
fans 86 speed. Specifically, a discharge pressure set point, e.g.,
420 psig, may be achieved by regulating the fan speed by a control
loop (e.g., a PID loop).
[0077] Conversely, when the air temperature in the dropped ceiling
(or in situation in which a flexible hose supplies air to the
condenser via intake opening 70, which may reduce the flow rate of
air to the condenser) is higher than a predetermined temperature,
e.g., above 100.degree. F., for example, a resulting elevated
condensing pressure may occur. This may result in a high pressure
cutout switch 38 cutting off power to the compressor 30, thus
causing total loss of cooling. In one embodiment, the condensing
pressure may be measured by the pressure transducer 36. For
example, the cooling unit 10 may be configured so that the high
pressure cutout switch 38 cuts off the power to the compressor 30
when the condensing pressure reaches a predetermined pressure,
e.g., 550 psig. In one method (in spot-discrete mode), if the
condensing pressure reaches a predetermined pressure, e.g., 520
psig, the bypass valve 64 opens and bypasses the coolant to the
evaporator 44 via conduit 66. The reduced coolant mass flow rate to
the condenser 34 reduces the heat rejection and the condensing
pressure is prevented from reaching the predetermined cutoff
pressure. While a slight pressure drop in the system may result,
the cooling unit 10 is still operating to provide the requisite
cooling. In another method (in spot-proportional, in-row and rack
air containment applications), if the condensing pressure reaches a
predetermined pressure, e.g., 520 psig, the speed of the evaporator
fans 68 is reduced to reduce the cooling capacity and heat
rejection in the condenser which will assist in reducing the
discharge pressure. The bypass valve 64 may also be manipulated to
increase or decrease the discharge pressure. Reducing evaporator
air flow will reduce the supply air temperature, which is regulated
by the bypass valve.
[0078] As discussed above, in certain embodiments, the following
control strategies may be employed when in running mode, e.g., mode
128 in FIG. 8. When controlling the bypass valve in discrete
capacity control mode, the bypass valve is normally held closed. If
the discharge pressure exceeds a certain threshold, e.g., 520 psig,
the bypass valve is opened linearly to a maximum of fifty percent
at an elevated predetermined pressure, e.g., 550 psig. With
reference to FIG. 11, when controlling the bypass valve in
proportional capacity control mode, the bypass valve is regulated
by a PID controller, for example, to (1) maintain the evaporating
temperature within a safe range, e.g., between 38.degree. F. and
56.degree. F., and (2) maintain the supply air temperature at the
predetermined, user-configurable supply air set point, e.g.,
between 52.degree. F. and 73.degree. F.
[0079] In certain other embodiments, and with reference to FIG. 12,
in all modes (discrete capacity and proportional capacity modes),
the condenser fans speed may be regulated by a PID controller to
maintain a predetermined discharge pressure, e.g., 425 psig.
Similarly, with reference to FIG. 13, the evaporator fans speed, in
discrete capacity mode, the evaporator fans are normally run at a
constant speed. The user may specify the evaporator fans speed by
setting the preferences within the controller user interface, e.g.,
the display unit. Specifically, in one embodiment, the user may
select one of five fan speeds when in spot-discrete mode, e.g.,
high, medium-high, medium, medium-low and low. In other
embodiments, the fan may be configured to operate in any number of
fan speeds. In addition, if the suction discharge temperature
exceeds a predetermined limit, e.g., 68.degree. F., the evaporator
fans speed may be lowered linearly to a minimum of fifty percent of
their normal speed at a predetermined temperature, e.g., 75.degree.
F., for example. In proportional capacity control mode, which may
be employed in spot cooling or in-row configurations, the
evaporator fans speed may be regulated by a PID controller to
maintain the cooling rack inlet temperature at a predetermined
user-configurable set point. Additionally, the evaporator fans
speed may be scaled down to alleviate certain abnormal conditions.
Specifically, the evaporator fans speed may be post-scaled under
the following conditions. When detecting high head pressure, the
evaporator fans speed may be scaled one hundred percent up to a
predetermined discharge pressure, e.g., 520 psig, down to a minimum
of sixty-five percent at an elevated predetermined temperature,
e.g., 550 psig, for example. The rate of the scaling may be
configured to be linear. When detecting high suction temperature,
the evaporator fans speed may be scaled one hundred percent up to a
predetermined suction temperature, e.g., 68.degree. F., down to a
minimum of fifty percent at an elevated predetermined temperature,
e.g., 75.degree. F., for example. As with high head pressure
detection, the rate of the scaling factor may be configured to be
linear. Should high head pressure and high suction temperature
abnormalities be detected simultaneously, the numerically lowest
scaling factor may be used to scale the evaporator fans speed.
[0080] In a particular embodiment having a proportional capacity
control configuration or in an air containment configuration, the
evaporator fans speed may be controlled by employing the following
equation:
T.sub.R=((Q.sub.actual*3415)/(CFM.sub.actual*1.08))+T.sub.S (1)
where [0081] T.sub.R--theoretical return air temperature; [0082]
Q.sub.actual--actual power output in Watts; [0083]
CFM.sub.actual--airflow through the evaporator in cubic feet per
minute; [0084] T.sub.S--supply air temperature in .degree. F.;
[0085] 3415--converts kW to BTU per hour; and [0086] 1.08--power
constant.
[0087] Next, the theoretical air return temperature may be averaged
with the actual air return temperature by using the following
equation:
T.sub.R=T.sub.R+T.sub.Ractual (2)
[0088] Next, the power demand for the air containment system is
calculated by using the following equation:
Q.sub.DMD=(.DELTA.T*CFM.sub.actual*1.08)/3415 (3)
where [0089] Q.sub.DMD--power demand; [0090] .DELTA.T=
T.sub.R-T.sub.setp; [0091] T.sub.setp--supply air set point in
.degree. F.; and [0092] CFM.sub.actual--airflow through the
evaporator in cubic feet per minute.
[0093] Next, the air containment system airflow demand is
calculated by employing the following equation:
CFM.sub.DMD=(Q.sub.DMD*3415)/(.DELTA.T.sub.set*1.08) (4)
where [0094] CFM.sub.DMD--air containment system airflow power
demand; and [0095] .DELTA.T.sub.set--desired temperature delta
across the cooling unit.
[0096] And finally, the desired evaporator fans speed may be
calculated by employing the following equation:
Speed.sub.percent=(CFM.sub.DMD/1200)*100 (5)
where [0097] Speed.sub.percent--evaporator fans speed; and [0098]
1200--maximum airflow in cubic feet per minute.
[0099] Based on the foregoing manipulation of the condenser fans
and the evaporator fans, the cooling unit 10 may be configured to
optimize its cooling capacity. Specifically, cooling capacity may
be calculated by the following equation:
Cooling Capacity = Compressor Cooling Capacity - Evaporator Fan
Heat - Latent Cooling ( 6 ) ##EQU00001##
[0100] The controller and the components of the cooling unit 10 may
be configured, by employing a polynomial equation having
coefficients unique to the compressor 30, coolant evaporating
temperature and coolant condensing temperature. Specifically, for
each cooling unit 10 used in the data center or equipment room, the
compressor 30 has a set of coefficients to calculate cooling
output, mass flow rate, energy efficiency rating, and current draw.
Each set may consist of up to ten coefficients, and as a result,
the compressor cooling capacity may be calculated by firmware
provided in the controller. The coolant pressures are measured by
the pressure transducers, and evaporating and condensing
temperatures may be calculated from the coolant evaporating and
condensing pressures and/or by temperature sensors.
[0101] To determine cooling capacity based on the fundamental
equation (6), one of four equations may be used. In one embodiment,
the cooling capacity may be determined by employing the following
equation:
P.sub.c=(Q.sub.comp-Q.sub.comp
loss-1052.6*C.sub.R*0.2928104-P.sub.f)/1000 (7)
where [0102] P.sub.c--net sensible cooling capacity; [0103]
Q.sub.comp--compressor performance; [0104] Q.sub.comp
loss--compressor heat loss; [0105] 1052.6--amount of energy
required to condense one pound of water; [0106] C.sub.R--condensate
production rate; [0107] 0.2928104--converts BTU/hour to Watts; and
[0108] P.sub.f--fan power.
[0109] Equation (7) relies on industry-standard ARI-540 compressor
cooling coefficients. Specifically, and with reference to FIG. 14,
when employing equation (7), the coolant pressure at the pressure
transducers is measured in psig at 200 and manipulated to calculate
the absolute coolant suction and discharge pressures (by adding
14.7 psi to the gauge pressures) at 202. The pressure measurements
are next converted from I-P units to SI units at 204. At 206, the
coolant evaporating and condensing temperatures may be calculated.
At 208, the ARI-540 polynomial equation may be calculated as
follows:
X=C1+C2*(S)+C3*D+C4*(S2)+C5*(S*D)+C6*(D2)+C7
*(S3)+C8*(D*S2)+C9*(S*D2)+C10*(D3) (8)
Where
[0110] X--can be (1) compressor capacity, (2) coolant mass flow
rate, (3) compressor input power or current, (4) or energy
efficiency ratio (EER); [0111] C--equation coefficient representing
compressor performance; [0112] S--suction dew point temperature in
.degree. C.; and [0113] D--discharge dew point temperature in
.degree. C.
[0114] Next, at 210, the compressor performance (Q.sub.comp) may be
calculated by inserting selected compressor performance
coefficients (in SI units) to the ARI-540 polynomial equation (8).
At 212, the compressor power input may be calculated by inserting
selected power coefficients (in SI units) to the ARI-540 polynomial
equation (8). Based on these calculations, the thermal heat
rejection component may be calculated at 214 in Watts by adding
Q.sub.comp and P.sub.comp. And finally, at 216, the compressor heat
loss may be calculated. Based on the results obtained above, the
cooling capacity of the cooling unit may be determine. It should be
noted that the compressor coefficients may be provided in both
metric (SI) and English units. When taking Celsius (.degree. C.)
temperature readings for evaporating and condensing temperatures,
the compressor coefficients are represented in metric units. When
taking Fahrenheit (.degree. F.) readings for evaporating and
condensing temperatures, the compressor coefficients are
represented in English units. It should further be noted that if
the compressor is not in the evaporator air stream, the Q.sub.comp
loss component of equation (7) is omitted.
Example
[0115] Using polynomial equation (7), which employs ARI-540
polynomial equation (8), the capacity of a cooling unit may be
calculated as follows. Equation (8) is employed, assuming the
following coefficients for a cooling unit using a 60 Hz
compressor:
TABLE-US-00001 Compressor Cooling Coefficient Capacity C1 2.206E+04
C2 3.403E+02 C3 -2.265E+02 C4 4.067E+00 C5 -8.068E-01 C6 1.352E+00
C7 1.309E-02 C8 -1.900E-02 C9 -2.813E-03 C10 -3.881E-03
[0116] The following estimated values for fan power, condensate
production rate and compressor heat loss may be assumed:
[0117] P.sub.f--300 Watts;
[0118] C.sub.R--1.6 pounds/hour; and
[0119] Q.sub.comp loss--150 Watts.
[0120] And finally, the following test measurements may be employed
for determining the coolant suction and discharge dew point
temperatures:
[0121] Evaporating Pressure--136 psig;
[0122] Discharge Pressure--438 psig;
[0123] Suction Dew Point Temperature--47.1.degree. F.; and
[0124] Discharge Dew Point Temperature--123.9.degree. F.
[0125] Based on the foregoing, cooling capacity is calculated as
follows:
Q.sub.comp=6393 Watts
P.sub.c=(6393-150-1052.6*1.6*0.2928104-300)/1000
P.sub.c=5.45 kW
[0126] In another embodiment, the cooling capacity of the cooling
unit may be determined by employing the following equation:
P.sub.c=((SCFM*0.075*60)*C.sub.p*DT.sub.air/3.415-Q.sub.comp
loss-P.sub.f)/1000 (9)
where [0127] P.sub.c--net sensible cooling capacity; [0128]
1000--converts Watts to Kilowatts; [0129] C.sub.p--specific heat of
air in BTU/lb-.degree. F.; [0130] Q.sub.comp loss--compressor heat
loss; [0131] DT.sub.air--supply and return air temperature
difference; [0132] SCFM--estimated standard volume flow rate at
given fan speeds [0133] 0.075--density of standard air in
lb/ft.sup.3; and [0134] P.sub.f--fan power.
[0135] With reference to FIG. 15, at 220, the return and supply air
temperatures of the cooling unit are measured. Next, at 222, the
average return and supply temperatures are determined. At 224, the
temperature differential (DT.sub.air) is calculated based on the
average return and supply temperatures. At 226, the evaporator coil
standard air flow rate at a given speed is calculated to determine
SCFM, assuming a specific heat C.sub.p at 0.243 BTU/lb-.degree. F.
The mass flow rate may be calculated at 228, followed by the
calculation of sensible cooling capacity at 230 and 232.
[0136] In yet another embodiment, cooling capacity of the cooling
unit may be determined by using the following equations:
Q.sub.thr=(SCFM*0.075*60)*C.sub.p*DT.sub.air/3.415 (10)
Q.sub.comp=O.sub.thr-P.sub.comp (11)
P.sub.c=(Q.sub.comp-1052.6C.sub.R*0.2928104-C.sub.comp
loss-P.sub.f)/1000 (12)
where [0137] Q.sub.thr--heat rejection at condenser coil; [0138]
P.sub.c--net cooling capacity; [0139] Q.sub.comp--compressor
performance; [0140] Q.sub.comp loss--compressor heat loss; [0141]
1052.6--amount of energy required to condense one pound of water;
[0142] 0.2928104--converts BTU/hour to Watts; [0143] P.sub.f--fan
power; [0144] C.sub.R--condensate production; [0145]
C.sub.p--specific heat of air; [0146] DT.sub.air--condenser
entering and leaving air temperature difference; [0147]
P.sub.comp--compressor power consumption; [0148] 1000--converts
Watts to Kilowatts; [0149] SCFM--estimated standard volumetric flow
rate at given fan speeds; and [0150] 0.075--density of standard
air.
[0151] Referring to FIG. 16, the method of calculating cooling
capacity with equations (10)-(12) is as follows. At 240, the
temperature of air entering into and exiting out of the condenser
is measured. At 242, the temperature differential between the air
entering into and exiting out of the condenser is calculated to
arrive at DT.sub.air. Next, at 244, the condenser coil standard
flow rate (SCFM) is estimated, assuming a specific heat (C.sub.p)
of 0.243 BTU/lb-ft. At 246, the mass flow rate (in lb/hr) is
calculated. At 248, the condenser heat rejection is calculated and
converted to watts by dividing the result by 3.415. The compressor
power input is calculated by inserting selected compressor power
input coefficients (in SI units) at 250 to the ARI-540 polynomial
equation (8) at 252. At 254 and 256, the compressor cooling output
and the cooling capacity is calculated, respectively. With respect
to the cooling capacity, the latent capacity, fan heat and
compressor heat loss are subtracted from the compressor cooling
output to determine the sensible cooling capacity.
[0152] And finally, in another embodiment, the cooling capacity may
be determined by utilizing the following equations:
P.sub.c=(Q.sub.total-Q.sub.comp
loss-1052.6*C.sub.R*0.2928104-P.sub.f)/1000 (13)
Q.sub.total=M*(h.sub.suction gas-h.sub.liquid) (14)
where [0153] P.sub.c--net sensible cooling capacity; [0154]
Q.sub.total--total cooling capacity; [0155] Q.sub.comp
loss--compressor heat loss; [0156] 1052.6--amount of energy
required to condense one pound of water; [0157] C.sub.R--condensate
production; [0158] 0.2928104--converts BTU/hr to Watts; [0159]
P.sub.f--fan power; [0160] 1000--converts Watts to Kilowatts;
[0161] Q.sub.total--total cooling capacity; [0162] M--coolant mass
flow rate; [0163] h.sub.suction gas--enthalpy of coolant at
evaporator coil outlet; and [0164] h.sub.liquid--enthalpy of
coolant at thermostatic expansion valve inlet.
[0165] Turning to FIG. 17, at 260, coolant gauge suction and
discharge pressures are measured at the suction and discharge
pipes. At 262, absolute coolant suction pressure (otherwise
referred to as evaporating pressure) and discharge pressure
(otherwise referred to as condensing pressure) are calculated by
adding 14.7 psi to the gauge pressures obtained in 260. At 264, the
units are converted to SI units. Next, at 266, dew point
evaporating and condensing temperatures are calculated. At 268, the
ARI-540 polynomial equation (3) is employed. At 270, the compressor
coolant mass flow rate is calculated by inserting selected
compressor performance coefficients. At 272, enthalpies of the
coolant at the thermostatic expansion valve inlet and evaporator
coil outlet are calculated by using coolant pressures and
temperatures. And finally, at 274 and 276, the total cooling
capacity and the net cooling capacity may be determined.
[0166] In a certain embodiment, the cooling unit may be configured
to provide uninterruptible cooling. Specifically, it has been
discovered that by bypassing coolant from high pressure hot gas
side to low temperature to the pressure suction side before the
discharge pressures reach the predetermined cutoff pressure, the
coolant flow rate to the condenser is reduced to reduce the
discharge pressure of coolant exiting the condenser. In certain
applications in which air temperature entering the condenser coil
is relatively high, e.g., 100.degree. F. or higher, the blockage of
air flow into the condenser may occur. This may result in very high
condensing pressures that require the high pressure cutoff switch
to activate thereby cutting off power to the compressor. Obviously,
the exposure to elevated temperatures may result in damage to the
electronic equipment housed in the equipment storage racks.
[0167] In one embodiment, the pressure transducer at the discharge
pipe may be employed to measure pressure of coolant entering the
condenser. As discussed above, the cooling unit may be provided
with a pressure cutoff switch, such as switch 38, which cuts off
the power when the condensing pressure reaches a predetermined
pressure, e.g., 550 psig. If, for example, the condensing pressure
reaches a threshold predetermined pressure, e.g., 525 psig, the
cooling unit may be configured to have the bypass valve open to
allow a portion of the high pressure coolant to return back to the
condenser. The coolant mass flow rate to the condenser coil is
reduced with the heat rejection and the condenser pressure is
limited so that the pressure within the condenser is below 550
psig. As a result, there may be a drop in cooling capacity, but
total loss of cooling may be prevented since the compressor remains
in operation.
[0168] Thus, it should be observed that by controlling the speed of
the condenser fans, the condensing pressure may be reduced as
needed, extremely high or low evaporating temperatures may be
avoided, and high suction temperatures to the compressor may be
avoided. In addition, the capacity of the cooling unit may be
controlled. By manipulating the hot gas bypass valve, the
condensing pressure may be reduced to prevent the cooling unit from
reaching a high threshold (cutoff) pressure, the evaporating
temperature may be controlled and the air temperature may be
controlled as well. Also, the hot gas bypass valve may be
manipulated to open during a compressor "off cycle" to expedite the
coolant pressure equalization for faster and quieter compressor
restarts. By closing the hot gas bypass valve periodically, the
delivery of coolant to the condenser may be increased to force the
delivery of oil that may be trapped back to the compressor.
[0169] As discussed, the cooling unit 10 is modular and scalable so
that a person designing a cooling system for the data center may
select individual components. Specifically, depending on the
electronic equipment deployed within the data center, and the
optimum operating conditions required for the equipment, the person
may employ any number of cooling units to provide primary or
supplemental cooling to the particular data center. In one
embodiment, the location of the cooling units within the room may
be determined using a computer aided design tool. Reference is made
to U.S. patent application Ser. No. 11/120,137, entitled "METHODS
AND SYSTEMS FOR MANAGING FACILITY POWER AND COOLING," filed on Apr.
7, 2005 and U.S. Provisional Patent Application No. 60/719,356,
entitled "METHODS AND SYSTEMS FOR MANAGING FACILITY POWER AND
COOLING," filed on Sep. 22, 2005, which are assigned to the
assignee of the present application and incorporated herein by
reference. These applications generally disclose systems and
methods for designing data centers and for managing equipment
contained within the data center.
[0170] In one configuration, the cooling units may be packaged and
shipped to the data center from a manufacturing or distribution
facility. Once received, the cooling units may be assembled and
otherwise installed within the data center. Specifically, the
cooling units are suitably connected to a power source (not shown)
and the controller to complete the installation.
[0171] As referenced above, in one embodiment, the controller may
be a separately dedicated unit that controls the operation of one
or more of the cooling units. In another embodiment, a main
controller may be provided in one of the cooling units in place of
one of the subservient controller units, with the cooling unit
having the controller functioning as the main cooling unit and the
other cooling units functioning as subservient cooling units. In
yet another embodiment, the operation of the cooling unit may be
under the control of an integrated data center control and
monitoring system with each cooling unit rack having a controller
that communicates with the other cooling units over the network. In
one such embodiment, the controller may communicate with a data
center control system to provide status of the components of the
cooling system and to receive control commands for the data center
control system. In one embodiment, each cooling unit includes a
controller that communicates with the data center controller over a
network, such as a CAN Bus network, and in one such embodiment, the
data center controller may be implemented using the integrated data
center control and monitoring system, such as the InfraStruXure.TM.
data center manager sold by American Power Conversion Corporation
of West Kingston, R.I., the assignee of the present invention.
[0172] In certain embodiments, the cooling unit may take the form
of a kit for cooling a data center. Depending on the volume of
space of the data center, the components of the kit are scalable to
meet the cooling requirements of the data center. In one
embodiment, the kit comprises a predetermined number of cooling
units adapted to be interspersed within rows of equipment racks in
the data center. The cooling units may embody the cooling unit
described above.
[0173] Thus, it should be observed that cooling units of
embodiments of the present invention are particularly configured
for scalable and modular implementation within a data center. The
cooling system may be provided in kit form that may be installed by
personnel having no particular training in cooling system
installation and no specialized tools. One benefit of the cooling
unit is that it may be movable within a data center, or to another
data center, when environmental conditions or needs within the data
center change. Another advantage is that each cooling unit is
self-contained, in that only power and communication needs to be
delivered to each unit. No external cooling systems are
required.
[0174] In addition, since the cooling unit may be provided as an
in-row product, the cooling unit may be positioned to intake the
hottest air in the data center and to cool it slightly below
ambient temperature. This design feature eliminates the
inefficiency of mixing hot air with the room temperature air to get
a warm mixture. The design also significantly decreases latent
cooling provided by the air conditioner, thereby potentially
eliminating the need for humidification. The improvements to
efficiency may best be seen by the fact that the foot print of a
cooling unit (e.g., cooling unit 10) may be decreased (e.g., by up
to thirty percent) to obtain the same cooling performance.
Specifically, the provision of movable cooling units having casters
and leveling feet improves the efficiency and the scalability of
the cooling system. To assist the operator in optimizing the
locations of the cooling units, the cooling capacity of each unit
may be monitored by the operator, along with the flow rate, coolant
and air inlet and outlet temperatures, and pressure differentials.
These readings enable the operator to place the cooling units where
each cooling unit may neutralize the maximum amount of heat, while
providing higher flexibility to the operator in the room design and
layout and removing the constraint of having air conditioners
positioned around the periphery of the data center. From a power
perspective, each cooling unit operates under direct current, thus
providing some level of flexibility to the input power provided.
Thus, a cooling unit no longer needs to be built for a specific
voltage.
[0175] As described above, the cooling unit of embodiments of the
invention may be further provided as part of an integrated data
center control and monitoring system. When used with such an
integrated control and monitoring system, the cooling unit is
easily removable for service and relocation to another position
within the data center. The cooling unit may also be integrated
into an existing cooling system of the building housing the data
center, for example and used in conjunction with one or more CRAC
units to provide additional cooled air where needed in the data
center.
[0176] The cooling unit may be provided with a predictive failure
determination module by utilizing a number of factors.
Specifically, through the controller, each cooling unit may be
designed to notify the data center operator when certain parts,
such as motors, fans, or any other part subject to wear, are near
the ends of their useful life. The provision of such a module will
enable a reasonably timed preventative maintenance action to be
performed and to save possible downtime. The notification may be
delivered to the display of the cooling unit, or provided to the
operator of the data center through the integrated control and
monitoring system. In addition, a controller of the cooling unit
configured as a main controller may compensate for a failure of a
particular cooling unit by increasing the output of other cooling
units positioned near the failed cooling unit.
[0177] With the cooling unit of embodiments of the present
invention, it is observed that the need for a raised floor is
eliminated. By eliminating the raised floor, costs associated with
designing and providing the raised floor are eliminated. In
addition, the equipment housed by the equipment racks may be better
anchored to the floor of the data center for enhanced earthquake
resistance. The number of suitable sites for server rooms or data
centers is increased because rooms with relatively low headroom may
now be utilized. Additionally, the need for raised floor ramps is
eliminated.
[0178] The cooling unit of embodiments of the present invention is
faster to install than prior systems. Since the cooling unit
includes a closed loop cooling system, only power and communication
need be connected to the cooling unit. Thus, the data center looks
more professional.
[0179] Having thus described several aspects of at least one
embodiment of this invention, it is to be appreciated various
alterations, modifications, and improvements will readily occur to
those skilled in the art. Such alterations, modifications, and
improvements are intended to be part of this disclosure, and are
intended to be within the spirit and scope of the invention.
Accordingly, the foregoing description and drawings are by way of
example only.
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