U.S. patent application number 13/444979 was filed with the patent office on 2012-11-01 for environmental control of liquid cooled electronics.
This patent application is currently assigned to IBM CORPORATION. Invention is credited to RAVI K. ARIMILLI, MICHAEL J. ELLSWORTH, JR., EDWARD J. SEMINARO.
Application Number | 20120273185 13/444979 |
Document ID | / |
Family ID | 42980125 |
Filed Date | 2012-11-01 |
United States Patent
Application |
20120273185 |
Kind Code |
A1 |
ARIMILLI; RAVI K. ; et
al. |
November 1, 2012 |
ENVIRONMENTAL CONTROL OF LIQUID COOLED ELECTRONICS
Abstract
A method, system, and computer program product are provided for
controlling liquid-cooled electronics, which includes measuring a
first set point temperature, T.sub.a, wherein the T.sub.a is based
on a dew point temperature, T.sub.dp of a computer room. A second
set point temperature, T.sub.b, is measured, wherein the T.sub.b is
based on a facility chilled liquid inlet temperature, T.sub.ci, and
a rack power, P.sub.rack, of an electronics rack. A Modular Cooling
Unit (MCU) set point temperature, T.sub.sp, is selected. The
T.sub.sp is the higher value of said T.sub.a and said T.sub.b.
Responsive to the selected T.sub.sp, a control valve is regulated.
The control valve controls a flow of liquid that passes through a
heat exchanger.
Inventors: |
ARIMILLI; RAVI K.; (AUSTIN,
TX) ; ELLSWORTH, JR.; MICHAEL J.; (LAGRANGEVILLE,
NY) ; SEMINARO; EDWARD J.; (MILTON, NY) |
Assignee: |
IBM CORPORATION
Armonk
NY
|
Family ID: |
42980125 |
Appl. No.: |
13/444979 |
Filed: |
April 12, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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12425210 |
Apr 16, 2009 |
|
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13444979 |
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Current U.S.
Class: |
165/287 |
Current CPC
Class: |
G05D 23/1931
20130101 |
Class at
Publication: |
165/287 |
International
Class: |
G05D 23/00 20060101
G05D023/00 |
Goverment Interests
[0005] This invention was made with United States Government
support under Agreement No. HR0011-07-9-0002 awarded by DARPA. The
Government has certain rights in this invention.
Claims
1. A method for controlling liquid-cooled electronics, said method
comprising: measuring a first set point temperature, T.sub.a,
wherein said T.sub.a is based on a dew point temperature, T.sub.dp
of a computer room; measuring a second set point temperature,
T.sub.b, wherein said T.sub.b is based on a facility chilled liquid
inlet temperature, T.sub.ci, and a rack power, P.sub.rack, of an
electronics rack; selecting a Modular Cooling Unit (MCU) set point
temperature, T.sub.sp, wherein said T.sub.sp is the higher value of
said T.sub.a and said T.sub.b; and regulating a control valve that
controls a flow of liquid that passes through a heat exchanger,
wherein said regulating is responsive to said selected
T.sub.sp.
2. The method of claim 1, said method further comprising: selecting
a default value of said T.sub.sp, in response to determining said
T.sub.a and said T.sub.b are not rationalized.
3. The method of claim 2, said method further comprising: selecting
said default value for T.sub.a in response to determining said
T.sub.dp is not rationalized.
4. The method of claim 2, said method further comprising: selecting
said default value for T.sub.b in response to determining said
T.sub.ci is not rationalized.
5. The method of claim 1, wherein said T.sub.a is set to a first
temperature constant of 15 degrees Celsius if T.sub.dp is less than
a threshold temperature of 12 degrees Celsius, and wherein said
T.sub.a is set to a first sum of: said T.sub.dp and a second
temperature constant of 3 degrees Celsius if said T.sub.dp is
greater or equal to said threshold temperature.
6. The method of claim 1, wherein said T.sub.b is equal to a second
sum of: said T.sub.ci, a product of 0.000032 and said P.sub.rack,
and a third temperature constant of 1.4 degrees Celsius.
7. The method of claim 1, said method further comprising: reducing
a number of revolutions per minute (RPMs) of a liquid inlet pump of
said MCU in response to a reduction in said T.sub.sp.
8. The method of claim 1, wherein said T.sub.b is equal to a second
sum of: said T.sub.ci, a product of 0.000032 and said P.sub.rack,
and a third temperature constant of 1.4 degrees Celsius.
Description
[0001] This application is a continuation of U.S. patent
application Ser. No. 12/425,210 entitled "ENVIRONMENTAL CONTROL OF
LIQUID COOLED ELECTRONICS" by Ravi K. Arimilli et al. filed Apr.
16, 2009, the disclosure of which is hereby incorporated herein by
reference in its entirety for all purposes.
CROSS REFERENCE TO RELATED APPLICATIONS
[0002] The present application is related to the following United
States Patent Applications, which are hereby incorporated by
reference in their entirety:
[0003] 1) U.S. patent application Ser. No. 11/942,207, filed Nov.
19, 2007; and
[0004] 2) U.S. patent application Ser. No. 12/425,226, filed Apr.
16, 2009.
TECHNICAL FIELD
[0006] The present invention relates in general to apparatuses and
methods for facilitating greater power efficiency and reliability
in the operation of liquid-cooled, rack-mounted assemblages of
individual electronics units, such as rack-mounted computer server
units.
BACKGROUND OF THE INVENTION
[0007] The power dissipation of integrated circuit chips, and the
modules containing the chips, continues to increase in order to
achieve increases in processor performance. This trend poses a
cooling challenge at both module and system level. Increased
airflow rates are needed to effectively cool high power modules and
to limit the temperature of the air that is exhausted into the
computer center.
[0008] In many large server applications, processors along with
their associated electronics (e.g., memory, disk drives, power
supplies, etc.) are packaged in removable drawer configurations
stacked within a rack or frame. In other cases, the electronics may
be in fixed locations within the rack or frame. Typically, the
components are cooled by air moving in parallel airflow paths,
usually front-to-back, impelled by one or more air moving devices
(e.g., fans or blowers). In some cases it may be possible to handle
increased power dissipation within a single drawer by providing
greater airflow, through the use of a more powerful air moving
device or by increasing the rotational speed (i.e., RPMs) of an
existing air moving device. However, this approach is becoming
problematic at the rack level in the context of a computer
installation (i.e., data center).
[0009] The sensible heat load carried by the air exiting the rack
is stressing the availability of the computer room air-conditioning
to effectively handle the load. This is especially true for large
installations with "server farms" or large banks of computer racks
close together. In such installations, liquid cooling (e.g., water
cooling) is an attractive technology to manage the higher heat
fluxes. The liquid absorbs the heat dissipated by the
components/modules in an efficient manner. Typically, the heat is
ultimately transferred from the liquid to an outside environment,
whether air or other liquid coolant.
[0010] Power consumption is also another variable that is
considered when addressing heat dissipation in an enterprise server
installation. In this regard, a data center operator is concerned
not only with the electricity costs associated with the operation
of the computer electronics, but also with the associated
electricity costs to cool the electronics operating within the
electronics racks. Such electricity costs include the cost to
operate chillers, condensers, pumps, fans, cooling towers, and
other related cooling components. Considering that a typical server
rack enclosure may require 250 kW of power, one can readily
appreciate the amount of heat that can be generated from several
tens or hundreds of electronics racks operating in an enterprise
server installation.
SUMMARY OF THE INVENTION
[0011] The shortcomings of the prior art are overcome and
additional advantages are provided through provision of a system
for facilitating cooling of electronics. The system includes: an
electronics rack having at least one heat-generating electronics
subsystem. The system also includes at least one Modular Cooling
Unit (MCU) associated with the electronics rack. The MCU is
configured to provide system coolant to the at least one
heat-generating electronics subsystem for facilitating cooling.
Moreover, the system includes at least one heat exchanger, at least
one control valve; and at least one system controller. The system
controller is coupled to the at least one control valve that
controls a flow of liquid that passes through the at least one heat
exchanger. The system controller is configured for measuring a
first set point temperature, T.sub.a, wherein T.sub.a is based on a
dew point temperature, T.sub.dp of a computer room. The system
controller is further configured for measuring a second set point
temperature, T.sub.b, wherein T.sub.b is based on a facility
chilled liquid inlet temperature, T.sub.ci, and a rack power,
P.sub.rack, of an electronics rack. Moreover, the system controller
is configured for selecting a Modular Cooling Unit (MCU) set point
temperature, T.sub.sp, wherein T.sub.sp is the higher value of
T.sub.a and T.sub.b. Responsive to the selected T.sub.sp, the
system controller is configured for regulating a control valve that
controls a flow of liquid that passes through a heat exchanger.
[0012] In another aspect, a computer program product for
controlling liquid-cooled electronics is provided. The computer
program product includes a computer-readable medium and program
instructions stored on the computer-readable medium that when
executed on a processing system, cause the processing system to
perform several functions. These functions include measuring a
first set point temperature, T.sub.a, wherein T.sub.a is based on a
dew point temperature, T.sub.dp of a computer room. Moreover, a
second set point temperature, T.sub.b, is measured, wherein the
T.sub.b is based on a facility chilled liquid inlet temperature,
T.sub.ci, and a rack power, P.sub.rack, of an electronics rack.
Another function includes selecting a Modular Cooling Unit (MCU)
set point temperature, T.sub.sp. The is the higher value of T.sub.a
and T.sub.b. Responsive to the selected T.sub.sp, a control valve
is regulated. The control valve controls a flow of liquid that
passes through a heat exchanger.
[0013] In a further aspect, a method for controlling liquid-cooled
electronics is provided. The method includes: measuring a first set
point temperature, T.sub.a, wherein T.sub.a is based on a dew point
temperature, T.sub.dp of a computer room; measuring a second set
point temperature, T.sub.b, wherein T.sub.b is based on a facility
chilled liquid inlet temperature, T.sub.ci, and a rack power,
P.sub.rack, of an electronics rack; selecting a Modular Cooling
Unit (MCU) set point temperature, T.sub.sp, wherein T.sub.sp, is
the higher value of T.sub.a and T.sub.b; and regulating a control
valve that controls a flow of liquid that passes through a heat
exchanger, wherein the regulating is responsive to the selected
T.sub.sp.
[0014] Further, additional features and advantages are realized
through the techniques of the present invention. Other embodiments
and aspects of the invention are described in detail herein and are
considered a part of the claimed invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The subject matter which is regarded as the invention is
particularly pointed out and distinctly claimed in the claims at
the conclusion of the specification. The foregoing and other
objects, features, and advantages of the invention are apparent
from the following detailed description taken in conjunction with
the accompanying drawings in which:
[0016] FIG. 1 depicts one embodiment of a conventional raised floor
layout of an air-cooled computer installation;
[0017] FIG. 2 depicts one problem addressed by the present
invention, showing recirculation airflow patterns in one
implementation of a raised floor layout of an air-cooled computer
installation, in accordance with an aspect of the present
invention;
[0018] FIG. 3 is a cross-sectional plan view of one embodiment of
an electronics rack utilizing at least one air-to-liquid heat
exchanger disposed at the air outlet side of the electronics rack,
in accordance with an aspect of the present invention;
[0019] FIG. 4 is a front elevational view of one embodiment of a
liquid-cooled electronics rack comprising multiple electronics
subsystems cooled by an apparatus, in accordance with an aspect of
the present invention;
[0020] FIG. 5 is a schematic of one embodiment of an electronics
subsystem of an electronics rack, wherein an electronics module is
liquid-cooled by system coolant provided by one or more modular
cooling units disposed within the electronics rack, in accordance
with an aspect of the present invention;
[0021] FIG. 6 is a schematic of one embodiment of a modular cooling
unit disposed within a liquid-cooled electronics rack, in
accordance with an aspect of the present invention;
[0022] FIG. 7 is a plan view of one embodiment of an electronics
subsystem layout illustrating an air and liquid cooling subsystem
for cooling components of the electronics subsystem, in accordance
with an aspect of the present invention;
[0023] FIG. 8 depicts one detailed embodiment of a partially
assembled electronics subsystem layout, wherein the electronics
subsystem includes eight heat-generating electronics components to
be actively cooled, each having a respective liquid-cooled cold
plate of a liquid-based cooling system coupled thereto, in
accordance with an aspect of the present invention;
[0024] FIG. 9 is a schematic of one embodiment of a system
comprising a liquid-cooled electronics rack and a cooling system
associated therewith, wherein the cooling system includes two
modular cooling units (MCUs) for providing in parallel liquid
coolant to the electronics subsystems of the rack, and to an
air-to-liquid heat exchanger disposed, for example, at an air
outlet side of the electronics rack for cooling air egressing there
from, in accordance with an aspect of the present invention;
[0025] FIG. 10 is a flowchart of one embodiment of processing
implemented by the system controller of FIG. 9 for facilitating
detection of a failure at MCU 1, and responsive thereto, shutting
off of MCU 1 and shutting off flow of coolant to the air-to-liquid
heat exchanger, in accordance with an aspect of the present
invention;
[0026] FIG. 11 is a flowchart of one embodiment of processing
implemented by the MCU control 1 of FIG. 9, which facilitates
monitoring of system coolant temperature, shut down of MCU 1 upon
detection of a failure thereof, and shut off of isolation valve 1,
in accordance with an aspect of the present invention;
[0027] FIG. 12 is a flowchart of one embodiment of processing
implemented by the system controller of FIG. 9 for facilitating
detection of a failure at MCU 2, and responsive thereto, shutting
off of MCU 2 and shutting off flow of coolant through the
air-to-liquid heat exchanger, in accordance with an aspect of the
present invention; and
[0028] FIG. 13 is a flowchart of one embodiment of processing
implemented by the MCU control 2 of FIG. 9, which facilitates
monitoring of system coolant temperature, shut down of MCU 2 upon
detection of a failure thereof, and shut off of isolation valve 2,
in accordance with an aspect of the present invention.
[0029] FIG. 14 is a flowchart of one embodiment of processing
implemented by the system controller 970 of FIG. 9, which
facilitates control of a MCU set point temperature, T.sub.sp, in
accordance with an aspect of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0030] As used herein, the terms "electronics rack," "rack-mounted
electronic equipment," and "rack unit" are used interchangeably,
and unless otherwise specified include any housing, frame, rack,
compartment, blade server system, etc., having one or more
heat-generating components of a computer system or electronics
system, and may be, for example, a stand alone computer processor
having high, mid or low end processing capability. In one
embodiment, an electronics rack may comprise multiple electronics
subsystems, each having one or more heat-generating components
disposed therein requiring cooling. "Electronics subsystem" refers
to any sub-housing, blade, book, drawer, node, compartment, etc.,
having one or more heat-generating electronic components disposed
therein. Each electronics subsystem of an electronics rack may be
movable or fixed relative to the electronics rack, with the
rack-mounted electronics drawers of a multidrawer rack unit and
blades of a blade center system being two examples of subsystems of
an electronics rack to be cooled.
[0031] "Electronic component" refers to any heat-generating
electronic component of, for example, a computer system or other
electronics unit requiring cooling. By way of example, an
electronic component may comprise one or more integrated circuit
dies and/or other electronic devices to be cooled, including one or
more processor dies, memory dies and memory support dies. As a
further example, the electronic component may comprise one or more
bare dies or one or more packaged dies disposed on a common
carrier. As used herein, "primary heat-generating component" refers
to a primary heat-generating electronic component within an
electronics subsystem, while "secondary heat-generating component"
refers to an electronic component of the electronics subsystem
generating less heat than the primary heat-generating component to
be cooled. "Primary heat-generating die" refers, for example, to a
primary heat-generating die or chip within a heat-generating
electronic component comprising primary and secondary
heat-generating dies (with a processor die being one example).
"Secondary heat-generating die" refers to a die of a multi-die
electronic component generating less heat than the primary
heat-generating die thereof (with memory dies and memory support
dies being examples of secondary dies to be cooled). As one
example, a heat-generating electronic component could comprise
multiple primary heat-generating bare dies and multiple secondary
heat-generating dies on a common carrier. Further, unless otherwise
specified herein, the term "liquid-cooled cold plate" refers to any
conventional thermally conductive structure having a plurality of
channels or passageways formed therein for flowing of liquid
coolant there through. In addition, "metallurgically bonded" refers
generally herein to two components being welded, brazed or soldered
together by any means.
[0032] As used herein, "air-to-liquid heat exchange assembly" means
any heat exchange mechanism characterized as described herein
through which liquid coolant can circulate; and includes, one or
more discrete air-to-liquid heat exchangers coupled either in
series or in parallel. An air-to-liquid heat exchanger may
comprise, for example, one or more coolant flow paths, formed of
thermally conductive tubing (such as copper or other tubing) in
thermal or mechanical contact with a plurality of air-cooled
cooling fins. Size, configuration and construction of the
air-to-liquid heat exchange assembly and/or air-to-liquid heat
exchanger thereof can vary without departing from the scope of the
invention disclosed herein. A "liquid-to-liquid heat exchanger" may
comprise, for example, two or more coolant flow paths, formed of
thermally conductive tubing (such as copper or other tubing) in
thermal or mechanical contact with each other. Size, configuration
and construction of the liquid-to-liquid heat exchanger can vary
without departing from the scope of the invention disclosed herein.
Further, "data center" refers to a computer installation containing
one or more electronics racks to be cooled. As a specific example,
a data center may include one or more rows of rack-mounted
computing units, such as server units.
[0033] One example of facility coolant and system coolant is water.
However, the concepts disclosed herein are readily adapted to use
with other types of coolant on the facility side and/or on the
system side. For example, one or more of the coolants may comprise
a brine, a fluorocarbon liquid, a liquid metal, or other similar
coolant, or refrigerant, while still maintaining the advantages and
unique features of the present invention.
[0034] Reference is made below to the drawings, which are not drawn
to scale for reasons of understanding, wherein the same reference
numbers used throughout different figures designate the same or
similar components.
[0035] As shown in FIG. 1, in a raised floor layout of an air
cooled computer installation 100 typical in the prior art, multiple
electronics racks 110 are disposed in one or more rows. A computer
installation such as depicted in FIG. 1 may house several hundred,
or even several thousand microprocessors. In the arrangement of
FIG. 1, chilled air enters the computer room via floor vents from a
supply air plenum 145 defined between the raised floor 140 and a
base or sub-floor 165 of the computer room. Cooled air is taken in
through louvered covers at air inlet sides 120 of the electronics
racks and expelled through the back (i.e., air outlet sides 130) of
the electronics racks. Each electronics rack 110 may have an air
moving device (e.g., fan or blower) to provide forced
inlet-to-outlet air flow to cool the electronic components within
the drawer(s) of the rack. The supply air plenum 145 provides
conditioned and cooled air to the air inlet sides of the
electronics racks via perforated floor tiles 160 disposed in a
"cold" aisle of the computer installation. The conditioned and
cooled air is supplied to plenum 145 by one or more conditioned air
units 150, also disposed within the computer installation 100.
Computer room air is taken into each conditioned air unit 150 near
an upper portion thereof. This computer room air comprises in part
exhausted air from the "hot" aisles of the computer installation
defined by opposing air outlet sides 130 of the electronics racks
110.
[0036] Due to the ever increasing air flow requirements through
electronics racks, and limits of air distribution within the
typical computer room installation, recirculation problems within
the computer room may occur. This is shown in FIG. 2 for a raised
floor layout, wherein hot air recirculation 200 occurs from the air
outlet sides 130 of the electronics racks back to the cold air
aisle defined by the opposing air inlet sides 120 of the
electronics rack. This recirculation can occur because the
conditioned air supplied through tiles 160 is typically only a
fraction of the air flow rate forced through the electronics racks
by the air moving devices disposed therein. This can be due, for
example, to limitations on the tile sizes (or diffuser flow rates).
The remaining fraction of the supply of inlet side air is often
made up by ambient computer room air through recirculation 200.
This re-circulating flow is often very complex in nature, and can
lead to significantly higher rack unit inlet temperatures than
might be expected.
[0037] The recirculation of hot exhaust air from the hot aisle of
the computer room installation to the cold aisle can be detrimental
to the performance and reliability of the computer system(s) or
electronic system(s) within the racks. Data center equipment is
typically designed to operate with rack air inlet temperatures in
the 18-35.degree. C. range. For a raised floor layout such as
depicted in FIG. 1, however, temperatures can range from
1520.degree. C. at the lower portion of the rack, close to the
cooled air input floor vents, to as much as 45-50.degree. C. at the
upper portion of the electronics rack, where the hot air can form a
self-sustaining recirculation loop. Since the allowable rack heat
load is limited by the rack inlet air temperature at the "hot"
part, this temperature distribution correlates to a lower
processing capacity. Also, computer installation equipment almost
always represents a high capital investment to the customer.
[0038] Thus, it is of significant importance, from a product
reliability and performance view point, and from a customer
satisfaction and business perspective, to maintain the temperature
of the rack inlet air within an acceptable range to avoid
condensation, overheating, and/or power efficiency issues. The
efficient cooling of such computer and electronic systems, and the
amelioration of localized hot air inlet temperatures to one or more
rack units due to recirculation of air currents, are addressed by
the apparatuses and methods disclosed herein.
[0039] FIG. 3 depicts one embodiment of a cooled electronics
system, generally denoted 300, in accordance with an aspect of the
present invention. In this embodiment, electronics system 300
includes an electronics rack 310 having an inlet door cover 320 and
an outlet door cover 330 which have openings to allow for the
ingress and egress of external air from the inlet side to the
outlet side of the electronics rack 310. The system further
includes at least one air moving device 312 for moving external air
across at least one electronics drawer unit 314 positioned within
the electronics rack. Disposed within outlet door cover 330 is a
heat exchange assembly 340. Heat exchange assembly 340 includes an
air-to-liquid heat exchanger through which the inlet-to-outlet air
flow through the electronics rack passes. A computer room water
conditioner (CRWC) 350 is used to buffer heat exchange assembly 340
from the building/facility/utility or local chilled coolant 360,
which is provided as input to CRWC 350. The CRWC 350 provides
system water or system coolant to heat exchange assembly 340. Heat
exchange assembly 340 removes heat from the exhausted
inlet-to-outlet air flow through the electronics rack for transfer
via the system water or coolant to CRWC 350. Advantageously,
providing a heat exchange assembly with an air-to-liquid heat
exchanger such as disclosed herein at the outlet door cover of one
or more electronics racks in a computer installation can
significantly reduce heat loads on the current computer room air
supply within the computer installation, and facilitating the
cooling of computer room air that is recirculated into the
rack-mounted electronics units.
[0040] FIG. 4 depicts one embodiment of a liquid-cooled electronics
rack 400 which employs a cooling system to be monitored and
operated utilizing the systems and methods described herein. In one
embodiment, liquid-cooled electronics rack 400 comprises a
plurality of electronics subsystems 410, which are processor or
server nodes. A bulk power regulator 420 is shown disposed at an
upper portion of liquid-cooled electronics rack 400, and two
modular cooling units (MCUs) 430 are disposed in a lower portion of
the liquid-cooled electronics rack. In the embodiments described
herein, the coolant is assumed to be water or an aqueous-based
solution, again, by way of example only.
[0041] Typically, server racks will include one or more MCUs which
are configured to provide system coolant (i.e., water or other
coolant) to the heat-generating electronics subsystem contained in
the server rack. Typically, MCUs set the system coolant temperature
to a fixed set point temperature, or T.sub.sp. However, by fixing
the set point temperature, MCUs do not take into account other
environmental and operating variables, which can permit higher set
point temperatures. These variables include computer room air
temperature and relative humidity (which when combined, determine
room dew point temperature, T.sub.dp), rack power (P.sub.rack), and
facility chilled water inlet temperature (T.sub.ci). If these
variables were accounted for, greater power efficiency can be
gained by raising the set point temperature that is necessary to
cool the heat-generating electronics.
[0042] Use of higher set point temperatures in a cooling system may
also prevent air in or around the system from falling below its
liquid saturation point, i.e., its dew point, and condensing.
Condensation can damage the electronics equipment in the server
rack and result in costly repairs and/or replacements. Allowing for
higher set point temperatures may, in certain circumstances,
provide benefits both in efficiency and in operations of the
system. Efficiency benefits may be obtained because creating
condensation requires much more energy than simply cooling air, so
that systems creating condensation may use a large amount of
electricity or other energy. Thus, the use of higher set point
temperatures may result in a cooling system that is operated at a
lower operating cost than could otherwise be achieved at a fixed
set point temperature.
[0043] In addition to MCUs 430, the cooling system includes a
system water supply manifold 431, a system water return manifold
432, and manifold-to-node fluid connect hoses 433 coupling system
water supply manifold 431 to electronics subsystems 410, and
node-to-manifold fluid connect hoses 434 coupling the individual
electronics subsystems 410 to system water return manifold 432.
Each MCU 430 is in fluid communication with system water supply
manifold 431 via a respective system water supply hose 435, and
each MWCU 430 is in fluid communication with system water return
manifold 432 via a respective system water return hose 436.
[0044] As illustrated, heat load of the electronics subsystems is
transferred from the system water to cooler facility water supplied
by facility water supply line 440 and facility water return line
441 disposed, in the illustrated embodiment, in the space between a
raised floor 145 and a base floor 165.
[0045] FIG. 5 schematically illustrates operation of the cooling
system of FIG. 4, wherein a liquid-cooled cold plate 500 is shown
coupled to an electronics module 501 of an electronics subsystem
410 within the liquid-cooled electronics rack 400. Heat is removed
from electronics module 501 via the system coolant circulated via
pump 520 through cold plate 500 within the system coolant loop
defined by liquid-to-liquid heat exchanger 521 of modular water
cooling unit 430, lines 522, 523 and cold plate 500. The system
coolant loop and modular water cooling unit are designed to provide
coolant of a controlled temperature and pressure, as well as
controlled chemistry and cleanliness to the electronics module(s).
Furthermore, the system coolant is physically separate from the
less controlled facility coolant in lines 440, 441, to which heat
is ultimately transferred.
[0046] FIG. 6 depicts a more detailed embodiment of a modular water
cooling unit 430, in accordance with an aspect of the present
invention. As shown in FIG. 6, modular water cooling unit 430
includes a first cooling loop wherein building chilled, facility
coolant is supplied 610 and passes through a control valve 620
driven by a motor 625. Control valve 620 determines an amount of
facility coolant to be passed through heat exchanger 521, with a
portion of the facility coolant possibly being returned directly
via a bypass orifice 635. The modular water cooling unit further
includes a second cooling loop with a reservoir tank 640 from which
system coolant is pumped, either by pump 650 or pump 651, into the
heat exchanger 521 for conditioning and output thereof, as cooled
system coolant to the electronics rack to be cooled. The cooled
system coolant is supplied to the system water supply manifold and
system water return manifold of the liquid-cooled electronics rack
via the system water supply hose 435 and system water return hose
436.
[0047] FIG. 7 depicts one embodiment of an electronics subsystem
410 component layout wherein one or more air moving devices 711
provide forced air flow 715 to cool multiple components 712 within
electronics subsystem 713. Cool air is taken in through a front 731
and exhausted out a back 733 of the drawer. The multiple components
to be cooled include multiple processor modules to which
liquid-cooled cold plates 720 (of a liquid-based cooling system)
are coupled, as well as multiple arrays of memory modules 730
(e.g., dual in-line memory modules (DIMMs)) and multiple rows of
memory support modules 732 (e.g., DIMM control modules) to which
air-cooled heat sinks are coupled. In the embodiment illustrated,
memory modules 730 and the memory support modules 732 are partially
arrayed near front 731 of electronics subsystem 410, and partially
arrayed near back 733 of electronics subsystem 410. Also, in the
embodiment of FIG. 7, memory modules 730 and the memory support
modules 732 are cooled by air flow 715 across the electronics
subsystem.
[0048] The illustrated liquid-based cooling system further includes
multiple coolant carrying tubes connected to and in fluid
communication with liquid-cooled cold plates 720. The
coolant-carrying tubes comprise sets of coolant-carrying tubes,
with each set including (for example) a coolant supply tube 740, a
bridge tube 741 and a coolant return tube 742. In this example,
each set of tubes provides liquid coolant to a series-connected
pair of cold plates 720 (coupled to a pair of processor modules).
Coolant flows into a first cold plate of each pair via the coolant
supply tube 740 and from the first cold plate to a second cold
plate of the pair via bridge tube or line 741, which may or may not
be thermally conductive. From the second cold plate of the pair,
coolant is returned through the respective coolant return tube
742.
[0049] FIG. 8 depicts in greater detail an alternate electronics
drawer layout comprising eight processor modules, each having a
respective liquid-cooled cold plate of a liquid-based cooling
system coupled thereto. The liquid-based cooling system is shown to
further include associated coolant-carrying tubes for facilitating
passage of liquid coolant through the liquid-cooled cold plates and
a header subassembly to facilitate distribution of liquid coolant
to and return of liquid coolant from the liquid-cooled cold plates.
By way of specific example, the liquid coolant passing through the
liquid-based cooling subsystem is chilled water.
[0050] As noted, various liquid coolants significantly outperform
air in the task of removing heat from heat-generating electronic
components of an electronics system, and thereby more effectively
maintain the components at a desirable temperature for enhanced
reliability and peak performance. As liquid-based cooling systems
are designed and deployed, it is advantageous to architect systems
which maximize reliability and minimize the potential for leaks
while meeting all other mechanical, electrical and chemical
requirements of a given electronics system implementation. These
more robust cooling systems have unique problems in their assembly
and implementation. For example, one assembly solution is to
utilize multiple fittings within the electronics system, and use
flexible plastic or rubber tubing to connect headers, cold plates,
pumps and other components. However, such a solution may not meet a
given customer's specifications and need for reliability.
[0051] Thus, presented herein in one aspect is a robust and
reliable liquid-based cooling system specially preconfigured and
prefabricated as a monolithic structure for positioning within a
particular electronics drawer.
[0052] FIG. 8 is an isometric view of one embodiment of an
electronics drawer and monolithic cooling system, in accordance
with an aspect of the present invention. The depicted planar server
assembly includes a multi-layer printed circuit board to which
memory DIMM sockets and various electronic components to be cooled
are attached both physically and electrically. In the cooling
system depicted, a supply header is provided to distribute liquid
coolant from a single inlet to multiple parallel coolant flow paths
and a return header collects exhausted coolant from the multiple
parallel coolant flow paths into a single outlet. Each parallel
coolant flow path includes one or more cold plates in series flow
arrangement to cool one or more electronic components to which the
cold plates are mechanically and thermally coupled. The number of
parallel paths and the number of series-connected liquid-cooled
cold plates depends, for example on the desired device temperature,
available coolant temperature and coolant flow rate, and the total
heat load being dissipated from each electronic component.
[0053] More particularly, FIG. 8 depicts a partially assembled
electronics system 813 and an assembled liquid-based cooling system
815 coupled to primary heat-generating components (e.g., including
processor dies) to be cooled. In this embodiment, the electronics
system is configured for (or as) an electronics drawer of an
electronics rack, and includes, by way of example, a support
substrate or planar board 805, a plurality of memory module sockets
810 (with the memory modules (e.g., dual in-line memory modules)
not shown), multiple rows of memory support modules 832 (each
having coupled thereto an air-cooled heat sink 834), and multiple
processor modules (not shown) disposed below the liquid-cooled cold
plates 820 of the liquid-based cooling system 815.
[0054] In addition to liquid-cooled cold plates 820, liquid-based
cooling system 815 includes multiple coolant-carrying tubes,
including coolant supply tubes 840 and coolant return tubes 842 in
fluid communication with respective liquid-cooled cold plates 820.
The coolant-carrying tubes 840, 842 are also connected to a header
(or manifold) subassembly 850 which facilitates distribution of
liquid coolant to the coolant supply tubes and return of liquid
coolant from the coolant return tubes 842. In this embodiment, the
air-cooled heat sinks 834 coupled to memory support modules 832
closer to front 831 of electronics drawer 813 are shorter in height
than the air-cooled heat sinks 834' coupled to memory support
modules 832 near back 833 of electronics drawer 813. This size
difference is to accommodate the coolant-carrying tubes 840, 842
since, in this embodiment, the header subassembly 850 is at the
front 831 of the electronics drawer and the multiple liquid-cooled
cold plates 820 are in the middle of the drawer.
[0055] Liquid-based cooling system 815 comprises a preconfigured
monolithic structure which includes multiple (pre-assembled)
liquid-cooled cold plates 820 configured and disposed in spaced
relation to engage respective heat-generating electronic
components. Each liquid-cooled cold plate 820 includes, in this
embodiment, a liquid coolant inlet and a liquid coolant outlet, as
well as an attachment subassembly (i.e., a cold plate/load arm
assembly). Each attachment subassembly is employed to couple its
respective liquid-cooled cold plate 820 to the associated
electronic component to form the cold plate and electronic
component assemblies. Alignment openings (i.e., thru-holes) are
provided on the sides of the cold plate to receive alignment pins
or positioning dowels during the assembly process. Additionally,
connectors (or guide pins) are included within attachment
subassembly which facilitate use of the attachment assembly.
[0056] As shown in FIG. 8, header subassembly 850 includes two
liquid manifolds, i.e., a coolant supply header 852 and a coolant
return header 854, which in one embodiment, are coupled together
via supporting brackets. In the monolithic cooling structure of
FIG. 8, the coolant supply header 852 is metallurgically bonded and
in fluid communication to each coolant supply tube 840, while the
coolant return header 854 is metallurgically bonded and in fluid
communication to each coolant return tube 852. A single coolant
inlet 851 and a single coolant outlet 853 extend from the header
subassembly for coupling to the electronics rack's coolant supply
and return manifolds (not shown).
[0057] FIG. 8 also depicts one embodiment of the preconfigured,
coolant-carrying tubes. In addition to coolant supply tubes 840 and
coolant return tubes 842, bridge tubes or lines 841 are provided
for coupling, for example, a liquid coolant outlet of one
liquid-cooled cold plate to the liquid coolant inlet of another
liquid-cooled cold plate to connect in series fluid flow the cold
plates, with the pair of cold plates receiving and returning liquid
coolant via a respective set of coolant supply and return tubes. In
one embodiment, the coolant supply tubes 840, bridge tubes 841 and
coolant return tubes 842 are each preconfigured, semi-rigid tubes
formed of a thermally conductive material, such as copper or
aluminum, and the tubes are respectively brazed, soldered or welded
in a fluid-tight manner to the header subassembly and/or the
liquid-cooled cold plates. The tubes are preconfigured for a
particular electronics system to facilitate installation of the
monolithic structure in engaging relation with the electronics
system.
[0058] Liquid cooling of heat-generating electronics components
within an electronics rack can greatly facilitate removal of heat
generated by those components. However, in certain high performance
systems, the heat dissipated by certain components being
liquid-cooled, such as processors, may exceed the ability of the
liquid cooling system to extract heat. For example, a fully
configured liquid-cooled electronics rack, such as described
hereinabove may dissipate approximately 250 kW of heat. Half of
this heat may be removed by liquid coolant using liquid-cooled cold
plates such as described above. The other half of the heat may be
dissipated by memory, power supplies, etc., which are air-cooled.
Given the density at which electronics racks are placed on a data
center floor, existing air-conditioning facilities are stressed
with such a high air heat load from the electronics rack. Thus, a
solution presented herein is to incorporate an air-to-liquid heat
exchanger, for example, at the air outlet side of the electronics
rack, to extract heat from air egressing from the electronics rack.
This solution is presented herein in combination with liquid-cooled
cold plate cooling of certain primary heat-generating components
within the electronics rack. To provide the necessary amount of
coolant, two MCUs are associated with the electronics rack, and
system coolant is fed from each MCU to the air-to-liquid heat
exchanger in parallel to the flow of system coolant to the
liquid-cooled cold plates disposed within the one or more
electronics subsystems of the electronics rack. Note that if
desired, flow of system coolant to the individual liquid cooled
cold plates may be in any one of a multitude of series/parallel
arrangements.
[0059] Also, for a high availability system, techniques are
described herein below for maintaining operation of one modular
cooling unit, notwithstanding failure of another modular cooling
unit of an electronics rack. This allows continued provision of
system coolant to the one or more electronics subsystems of the
rack being liquid-cooled. To facilitate liquid cooling of the
primary heat-generating electronics components within the
electronics rack, one or more isolation valves are employed (upon
detection of failure at one MCU of the two MCUs) to shut off
coolant flow to the air-to-liquid heat exchanger, and thereby,
conserve coolant for the direct cooling of the electronics
subsystems. The above-summarized aspects of the invention are
described further below with reference to the system and method
embodiment of FIGS. 9-13.
[0060] In addition, techniques are described herein below for
controlling an MCU set point temperature (T.sub.sp) depending upon
other environmental and operational variables, which include dew
point temperature (T.sub.dp), inlet temperature of the facility
chilled liquid that enters the MCU (T.sub.ci), and power required
by the electronics rack (P.sub.rack). The above-summarized aspects
of the invention are described further below with reference to the
system and method embodiment of FIGS. 9 and 14.
[0061] FIG. 9 illustrates one embodiment of a system wherein an
electronics rack 900 includes a plurality of heat-generating
electronic subsystems 910, which are liquid-cooled employing a
cooling system comprising at least two modular cooling units (MCUs)
920, 930 labeled MCU 1 & MCU 2, respectively. The MCUs are
configured and coupled to provide system coolant in parallel to the
plurality of heat-generating electronic subsystems for facilitating
liquid cooling thereof. Each MCU 920, 930 includes a
liquid-to-liquid heat exchanger 921, 931, a first coolant loop 922,
932, and a second coolant loop, 923, 933, respectively. The first
coolant loops 922, 932 are coupled to receive chilled coolant, such
as facility coolant, via (for example) facility water supply line
440 and facility water return line 441. Each first coolant loop
922, 932 passes at least a portion of the chilled coolant flowing
therein through the respective liquid-to-liquid heat exchanger 921,
931. Each second coolant loop 923, 933 provides cooled system
coolant to the plurality of heat-generating electronic subsystems
910 of electronics rack 900, and expels heat via the respective
liquid-to-liquid heat exchanger 921, 931 from the plurality of
heat-generating electronic subsystems 910 to the chilled coolant in
the first coolant loop 922, 932.
[0062] The second coolant loops 923, 933 include respective coolant
supply lines 924, 934, which supply cooled system coolant from the
liquid-to-liquid heat exchangers 921, 931 to a system coolant
supply manifold 940. System coolant supply manifold 940 is coupled
via flexible supply hoses 941 to the plurality of heat-generating
electronics subsystems 910 of electronics rack 900 (e.g., using
quick connect couplings connected to respective ports of the system
coolant supply manifold). Similarly, second coolant loops 923, 933
include system coolant return lines 925, 935 coupling a system
coolant return manifold 950 to the respective liquid-to-liquid heat
exchangers 921, 931. System coolant is exhausted from the plurality
of heat-generating electronics components 910 via flexible return
hoses 951 coupling the heat-generating electronics subsystems to
system coolant return manifold 950. In one embodiment, the return
hoses may couple to respective ports of the system coolant return
manifold via quick connect couplings. Further, in one embodiment,
the plurality of heat-generating electronics subsystems each
include a respective liquid-based cooling subsystem, such as
described above in connection with FIGS. 7 & 8, coupled to
flexible supply hoses 941 and flexible return hoses 951 to
facilitate liquid cooling of one or more heat-generating
electronics components disposed within the electronics
subsystem.
[0063] In addition to supplying and exhausting system coolant in
parallel to the plurality of heat-generating electronics subsystems
of the electronics rack, the MCUs 920, 930 also provide in parallel
system coolant to an air-to-liquid heat exchanger 960 disposed, for
example, for cooling air passing through the electronics rack from
an air inlet side to an air outlet side thereof. By way of example,
air-to-liquid heat exchanger 960 is a rear door heat exchanger
disposed at the air outlet side of electronics rack 900. Further,
in one example, air-to-liquid heat exchanger 960 is sized to cool
substantially all air egressing from electronics rack 900, and
thereby reduce air-conditioning requirements for a data center
containing the electronics rack. In one example, a plurality of
electronics racks in the data center are each provided with a
cooling system such as described herein and depicted in FIG. 9.
[0064] In the embodiment of FIG. 9, system coolant flows to and
from air-to-liquid heat exchanger 960 via a coolant supply line 961
coupling system coolant supply manifold 940 to air-to-liquid heat
exchanger 960, and a coolant return line 962 coupling the
air-to-liquid heat exchanger to system coolant return manifold 950.
Quick connect couplings may be employed at the inlet and outlet of
air-to-liquid heat exchanger 960 and/or at corresponding ports at
the system coolant supply and return manifolds to facilitate
connection of coolant supply and return lines 961, 962. In one
embodiment, it is assumed that one MCU of the two MCUs illustrated
is incapable of being sized to function within required design
parameters as a primary MCU (with the other MCU being a backup MCU)
to extract the full heat load from both the plurality of
heat-generating electronics subsystems and the air-to-liquid heat
exchanger. Therefore, the two MCUs 920, 930 are assumed in normal
operation to be functioning in parallel. This also ensures a
measure of redundancy to the cooling system.
[0065] As shown, the cooling system further includes a system
controller 970, and an MCU control 1 980 and an MCU control 2 990,
which cooperate together to monitor system coolant temperature of
each MCU, and automatically isolate air-to-liquid heat exchanger
960 upon detection of failure of one MCU (as well as to ensure shut
down of a failing MCU) so as not to degrade cooling capability of
the system coolant provided by the remaining operational MCU to the
electronics subsystems of the rack. In one embodiment, the MCU
control 1 and the MCU control 2 are control cards, each associated
with a respective MCU.
[0066] As shown, system controller 970 is coupled to both MCU
control 1 and the MCU control 2. MCU control 1 980 is coupled to a
temperature sensor T.sub.1 981, which is disposed to sense system
coolant temperature within system coolant supply line 924, for
example, near a coolant outlet of liquid-to-liquid heat exchanger
921 within MCU 1 920. Additionally, MCU control 1 980 is coupled to
a solenoid-actuated isolation valve 982, which in the embodiment
depicted, is disposed within coolant supply line 961 coupling in
fluid communication system coolant supply manifold 940 to
air-to-liquid heat exchanger 960. Similarly, MCU control 2 990
couples to MCU 2 930, as well as to a second temperature sensor
T.sub.2 991, disposed for sensing system coolant temperature within
system coolant supply line 934, and to a second isolation valve
S.sub.2 992, which in the example depicted, is coupled to coolant
return line 962 coupling air-to-liquid heat exchanger 960 to
coolant supply return manifold 950. System controller 970 is
coupled to a third temperature sensor T.sub.3 983 disposed for
sensing facility chilled liquid inlet temperature (T.sub.ci). In
addition, system controller 970 is coupled to a fourth temperature
sensor T.sub.4 994 for sensing the computer room's air temperature,
a hygrometer, H.sub.1 995 for sensing the relative humidity in the
computer room, and a wattmeter W.sub.1 996 for sensing the
electrical power consumed by the rack. System controller 970
includes a processor and computer-readable storage memory for
storing processor-executable instructions associated with the
control of MCU set point temperature (T.sub.sp), as described in
FIG. 14. System controller 970 is electrically coupled to control
valve 620 (FIG. 6).
[0067] FIGS. 10-13 are flowcharts which illustrate processing
implemented by system controller 970, MCU control 1 980 and MCU
control 2 990. Table 1 describes variables used in the example
flowcharts of FIGS. 10-13, as well as possible values and initial
conditions for each variable when the cooling system is operating
normally.
TABLE-US-00001 TABLE 1 Initial Variable Description Value = 1 Value
= 0 Condition TS Temperature within In Out of 1 specification?
specification specification ST MCU ON or OFF? ON OFF 1 SV Isolation
valve Open Closed 1 open or closed? FS Has MCU been shut Has been
Has not been 0 down? shut down shut down FV Has isolation valve Has
been Has not been 0 been closed? closed closed
[0068] The variables are further qualified in FIGS. 10-13 with the
number "1" or the number "2", representative of whether the
variable applies to the first or second temperature sensor, first
or second MCU, or first or second isolation valve.
[0069] In the below discussion, although described with reference
to processing within system controller 970 (FIG. 9) and MCU control
1 card 980 and MCU control 2 card 990, one skilled in the art will
understand that the processing described herein could readily be
implemented by a single controller coupled to each temperature
sensor, isolation valve and MCU. In the illustrated embodiment,
FIGS. 10 & 12 depict processing implemented within system
controller 970, while FIG. 11 describes processing of MCU control 1
980 and FIG. 13 processing of MCU control 2 990 (by way of example
only).
[0070] Beginning with FIG. 10, the system controller receives as
input variable TS 1 from MCU control 1 1000, which indicates
whether system coolant being output from MCU 1 is within
specification (i.e., within a defined range). The system controller
initially determines whether MCU 1 is running (that is, whether the
variable ST1=1) 1005. If "no", then processing returns to MCU
control 1 1030 with the system controller sending current ST1 and
SV 1 values back to MCU control 1.
[0071] Assuming that MCU 1 is running, then the system controller
determines whether the temperature sensed at temperature sensor T1
is within specification (i.e., whether TS 1=1) 1010. If "yes",
processing returns to MCU control 1 1030. Assuming that system
coolant temperature sensed by temperature sensor T1 is out of
specification, then the system controller determines whether MCU 2
has been shut down (i.e., ST2=0?) 1015. If "no", then the variable
ST1 is set to zero to indicate that MCU 1 should be shut down 1020,
and the variable SV1 is set to zero to direct closing of isolation
valve S.sub.1 1025. These new values are returned to MCU control 1
1030, which acts on the new values as described herein below.
[0072] Assuming that MCU 2 has been shut down, then processing
inquires whether isolation valve S.sub.1 has been closed (FV1=1?)
1035. If "no", then the variable SV1 is set to zero to instruct
closing of isolation valve S.sub.1 1040, after which processing
returns to MCU control 1 with the new SV1 value to effectuate
closing of isolation valve S.sub.1. If isolation valve S.sub.1 has
been closed, then the system controller sets the variable ST1 equal
to zero to shut down MCU 1 1045 and issues an alarm (e.g., to a
data center operator) indicating that the cooling system for the
associated electronics rack is shutting down 1050, after which
processing returns to MCU control 1 to effectuate the MCU 1 shut
down.
[0073] As noted, FIG. 11 depicts one embodiment of processing
implemented by MCU control 1 980 (FIG. 9). MCU control 1 receives
as input the variables ST1 and SV1 from the system controller 1100,
and initially determines whether MCU 1 has been shut down (FS1=1?)
1105. If "yes", then processing returns to the system controller
1145. If "no", then processing determines whether MCU 1 is to be
shut down (ST1=0?) 1110. If "yes", MCU control 1 shuts down MCU 1
1115 and sets the variable FS1 equal to 1 1120, indicating that MCU
1 has been shut down, after which processing returns to the system
controller 1145.
[0074] Assuming that MCU 1 is not to be shut down, then processing
determines whether isolation valve S.sub.1 has been shut (FV 1=0?)
1125. If "yes", processing waits time t 1130 before reading
temperature sensor T1 1135. By way of example, time t might be
15-30 seconds in operation. Processing then determines whether the
value of temperature sensor T.sub.1 is within specification (e.g.,
is T.sub.1 greater than a predefined acceptable lower limit (LL),
and less than a predefined acceptable upper limit (UL)?) 1140. If
"no", then the variable TS 1 is set to zero to indicate that system
coolant temperature is out of specification 1150 and processing
returns to system controller 1145. From inquiry 1125, if isolation
valve S.sub.1 has not been shut, processing determines whether
isolation valve S.sub.1 is to be closed 1155. If "no", processing
waits time t, and then proceeds as described above. Otherwise, MCU
control 1 closes isolation valve S.sub.1 1160 and sets the variable
FV 1 equal to 1 1165, and returns processing control to system
controller 1145.
[0075] As noted, FIG. 12 depicts system controller processing with
respect to MCU control 2. As described above in connection with
FIG. 10, the system controller receives as input variable TS2 from
MCU control 2 1200, which indicates whether second system coolant
temperature is within specification (i.e., within a defined range).
The system controller initially determines whether MCU 2 is running
(ST2=1?) 1205. If "no", then processing returns to MCU control 2
1230, with the system controller sending current ST2 and SV2 values
back to MCU control 2.
[0076] Assuming that MCU 2 is running, then the system controller
determines whether the temperature sensed at temperature sensor
T.sub.2 is within specification (TS2=1) 1210. If "yes", processing
returns to MCU control 2 1230. Assuming that system coolant
temperature sensed by temperature sensor T.sub.2 is out of
specification, then the system controller determines whether MCU 2
has been shut down (ST2=0?) 1215. If "no", then the variable ST2 is
set to zero to indicate that MCU 2 should be shut down 1220, and
the variable SV2 is set to zero to direct closing of isolation
valve S.sub.2 1225. These new values are returned to MCU control 2
1230, which acts on the new values as described below.
[0077] Assuming that MCU 2 has been shut down, then processing
inquires whether isolation valve S.sub.2 has been closed (FV2=1?)
1235. If "no", then the variable SV2 is set to zero to instruct
closing of isolation valve S.sub.2 1240, after which processing
returns to MCU control 2 with the new SV 2 value to effectuate
closing of isolation valve S.sub.2. If isolation valve S.sub.2 has
been closed, then the system controller sets the variable ST2 equal
to zero to shut down MCU 2 1245 and issues an alarm (e.g., to a
data center operator), indicating that the cooling system for the
associated electronics rack is shutting down 1250, after which
processing returns to MCU control 2 to effectuate the MCU 2 shut
down.
[0078] FIG. 13 depicts one embodiment of processing implemented by
MCU control 2. MCU control 2 receives as input the variables ST2
and SV2 from the system controller 1300, and initially determines
whether MCU 2 has been shut down (i.e., FS 2=1?) 1305. If "yes",
then processing returns to the system controller 1345. If "no",
then processing determines whether MCU 2 is to be shut down
(ST2=0?) 1310. If "yes", MCU control 2 shuts down MCU 2 1315 and
sets the variable FS2 equal to 1 1320, indicating that MCU 2 has
been shut down, after which processing returns to the system
controller 1345.
[0079] Assuming that MCU 1 is not to be shut down, then processing
determines whether isolation valve S.sub.2 has been shut (FV2=0?)
1325. If "yes", processing waits time t 1330 before reading
temperature sensor T2 1335. By way of example, time t might be
15-30 seconds in operation. Processing then determines whether the
value of temperature sensor T2 is within specification (e.g., is T2
greater than predefined acceptable lower limit (LL), and less than
predefined acceptable upper limit (UL)?) 1340. If "no", then the
variable TS2 is set to zero to indicate that system coolant
temperature is out of specification 1150 and processing returns to
system controller 1345. From inquiry 1325, if isolation valve
S.sub.2 has not been shut, processing determines whether isolation
valve S.sub.1 is to be closed 1355. If "no", processing waits time
t, and proceeds as described above. Otherwise, MCU control 2 closes
isolation valve S.sub.2 1360 and sets the variable FV2 equal to 1
1365 and returns processing control to system controller 1345.
[0080] Turning now to FIG. 14 a method is illustrated for
controlling the MCU set point temperature, T.sub.sp. The method is
implemented by system controller 970. The method begins at block
1405 and proceeds to block 1410, where a first set point
temperature, T.sub.a, is measured. The value of the first set point
temperature is based on the measured dew point temperature,
T.sub.dp, values of the computer room. System controller 970
measures T.sub.dp, using the measured values from fourth
temperature sensor T.sub.4 994 and hygrometer H.sub.1 995.
According to an embodiment of the invention, the value of T.sub.a
varies depending upon the measured dew point temperature, T.sub.dp.
For example, if T.sub.dp is less than 12.degree. C., then T.sub.a
is set to 15.degree. C. However, if T.sub.dp, is greater than or
equal to 12.degree. C., then T.sub.a is equal to the measured
T.sub.dp, plus 3.degree. C. If the value of T.sub.dp is not
rationalized (i.e., the value cannot be obtained, inaccurate, or
unreliable), the value of T.sub.a is set to a default value of
24.degree. C.
[0081] From block 1410, the method continues to block 1415, where a
second set point temperature, T.sub.b, is measured. The value of
the second set point temperature is based on the facility chilled
liquid inlet temperature, T.sub.ci (as measured by T.sub.3 983) and
the rack power, P.sub.rack (as measured by W.sub.1 996). According
to one embodiment, the expression which relates T.sub.b, T.sub.ci,
P.sub.rack is as follows:
T.sub.b=T.sub.ci+(0.000032*P.sub.raak+1.4.degree. C.). If the value
of T.sub.ci is not rationalized, the value of T.sub.b is set to a
default value of 24.degree. C. Moreover, if the value of P.sub.rack
is not rationalized and the value of T.sub.ci is rationalized, then
the value of T.sub.b is equal to T.sub.ci+8.degree. C.
[0082] From block 1415, the method continues to decision block
1420, where it is determined whether the values of T.sub.a and/or
T.sub.b are rationalized values. If it is determined in decision
block 1420 that either T.sub.a or T.sub.b are not rationalized
values, then the method proceeds to block 1425 which depicts system
controller 970 setting a default value for T.sub.sp (e.g.,
24.degree. C.). From block 1425, the method ends at termination
block 1435. However, if it is determined in decision block 1420
that T.sub.a and T.sub.b are rationalized values, then the method
proceeds to block 1430 which depicts system controller 970
selecting the higher value among T.sub.a and T.sub.b as the MCU set
point temperature T.sub.sp. By selecting the higher value, the MCU
can operate with greater power efficiency since the liquid coolant
does not have to be cooled to a lower temperature, while at the
same time ensuring that the MCU setpoint temperature does not fall
below the current dew point temperature, T.sub.dp. The method ends
at termination block 1435.
[0083] Those skilled in the art will note from the above
description that various aspects of the coolant control valve
operations and protocol depicted in the figures may be automated by
provision of an appropriate controller disposed, for example,
within the coolant servicing apparatus, and the use of
solenoid-operated control valves coupled to the controller.
Moreover, according to one embodiment of the invention, system
controller 970 can direct the reduction in the number of
revolutions per minute (RPM) of a liquid inlet pump of an MCU in
response to a reduction in MCU set point temperature, T.sub.sp.
Conversely, system controller 970 can direct an increase in the
number of revolutions per minute (RPM) of a liquid inlet pump of an
MCU in response to an increase in T.sub.sp.
[0084] In the flow charts above, one or more of the methods and/or
processes are embodied in a computer readable medium including
computer readable code such that a series of steps are performed
when the computer readable code is executed by a processor. In one
or more implementations, certain processes of the methods and/or
processes are combined, performed simultaneously, concurrently
(e.g., scheduled quickly enough in time to appear simultaneous to a
person), or in a different order, or perhaps omitted, without
deviating from the spirit and scope of the invention. Thus, while
the method(s) and/or process(es) are described and illustrated in a
particular sequence, use of a specific sequence of processes is not
meant to imply any limitations on the invention. Changes may be
made with regards to the sequence of processes without departing
from the spirit or scope of the present invention. Use of a
particular sequence is therefore, not to be taken in a limiting
sense, and the scope of the present invention extends to the
appended claims and equivalents thereof.
[0085] As will be appreciated by one skilled in the art, the
present invention may be embodied as a method, process, system,
and/or computer program product. Accordingly, the present invention
may take the form of an entirely hardware embodiment, an entirely
software embodiment (including firmware, resident software,
micro-code, etc.) or an embodiment combining software and hardware
aspects that may all generally be referred to herein as a
"circuit," "module," "logic," and/or "system." Furthermore, the
present invention may take the form of an article of manufacture
having a computer program product with a computer-usable storage
medium having computer-executable program instructions/code
embodied in or on the medium.
[0086] As will be further appreciated, the method(s) and/or
process(es) in embodiments of the present invention may be
implemented using any combination of software, firmware, microcode,
and/or hardware. As a preparatory step to practicing the invention
in software, the programming code (whether software or firmware)
will typically be stored in one or more machine readable storage
mediums such as fixed (hard) drives, diskettes, magnetic disks,
optical disks, magnetic tape, semiconductor memories such as RAMs,
ROMs, PROMs, EPROMs, EEPROMs, etc., thereby making an article of
manufacture, in one or more embodiments. The medium may be
electronic, magnetic, optical, electromagnetic, infrared, or
semiconductor system (or apparatus or device) or a propagation
medium. Further, the medium may be any apparatus that may include,
store, communicate, propagate, or transport the program for use by
or in connection with the execution system, apparatus, or device.
The method(s) and/or process(es) disclosed herein may be practiced
by combining one or more machine-readable storage devices including
the code/logic according to the described embodiment(s) with
appropriate processing hardware to execute and/or implement the
code/logic included therein. In general, the term computer,
computer system, or data processing system can be broadly defined
to encompass any device having a processor (or processing unit)
which executes instructions/code from a memory medium.
[0087] While the invention has been described with reference to
exemplary embodiments, it will be understood by those skilled in
the art that various changes may be made and equivalents may be
substituted for elements thereof without departing from the scope
of the invention. In addition, modifications may be made to adapt a
particular system, device or component thereof to the teachings of
the invention without departing from the essential scope thereof.
Therefore, it is intended that the invention not be limited to the
particular embodiments disclosed for carrying out this invention,
but that the invention will include all embodiments falling within
the scope of the appended claims. Moreover, use of the terms first,
second, etc. can denote an order if specified, or the terms first,
second, etc. can be used to distinguish one element from another
without an ordered imposed.
* * * * *