U.S. patent application number 13/279045 was filed with the patent office on 2012-04-26 for flow balancing scheme for two-phase refrigerant cooled rack.
This patent application is currently assigned to COOLIGY INC.. Invention is credited to Adrian Correa.
Application Number | 20120097370 13/279045 |
Document ID | / |
Family ID | 45971974 |
Filed Date | 2012-04-26 |
United States Patent
Application |
20120097370 |
Kind Code |
A1 |
Correa; Adrian |
April 26, 2012 |
FLOW BALANCING SCHEME FOR TWO-PHASE REFRIGERANT COOLED RACK
Abstract
A cooling system distributes fluid to a plurality of docking
bays within a server rack. The server rack includes docking bays
for housing electronics devices. A two-phase fluid-based heat
exchanging system is coupled to each docking bay, which functions
to remove heat from the electronics server. The docking bays are
conceptually divided into one or more sections, and a dynamic fluid
flow regulator is included within a section input line that
supplies a liquid-phase fluid to each section. The section input
line branches into a plurality of parallel fluid paths, one
parallel fluid path coupled to each docking bay in the section. A
fixed fluid flow regulator is included within each branching fluid
pathway. The combination of the dynamic and fixed fluid flow
regulators provides balanced fluid flow to each two-phase heat
exchanging system.
Inventors: |
Correa; Adrian; (San Jose,
CA) |
Assignee: |
COOLIGY INC.
Mountain View
CA
|
Family ID: |
45971974 |
Appl. No.: |
13/279045 |
Filed: |
October 21, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61406084 |
Oct 22, 2010 |
|
|
|
Current U.S.
Class: |
165/104.21 ;
165/185 |
Current CPC
Class: |
G06F 1/20 20130101; H05K
7/20818 20130101; G06F 2200/201 20130101 |
Class at
Publication: |
165/104.21 ;
165/185 |
International
Class: |
F28D 15/02 20060101
F28D015/02 |
Claims
1. A cooling assembly comprising: a. a plurality of fluid-based
two-phase cooling systems; and b. a fluid input manifold configured
to supply a coolant in a liquid-phase to each of the plurality of
fluid-based cooling systems, the fluid input manifold comprises: i.
a fluid input line; ii. one or more dynamic fluid flow regulators
coupled in parallel to the fluid input line, wherein each dynamic
fluid flow regulator is configured to provide a variable fluid flow
resistance; and iii. a plurality of fixed fluid flow regulators,
one fixed fluid flow regulator coupled to each cooling system,
wherein the plurality of fixed fluid flow regulators are arranged
into one or more groups, one group coupled to each dynamic fluid
flow regulator such that all fixed fluid flow regulators in the
group are coupled in parallel to the dynamic fluid flow regulator,
further wherein each fixed fluid flow regulator is configured to
provide a fixed fluid flow orifice.
2. The cooling system of claim 1 further comprising a fluid output
manifold configured to receive two-phase coolant from each of the
plurality of cooling systems.
3. The cooling assembly of claim 1 wherein the fluid output
manifold comprises a plurality of cooling system output lines, one
cooling system output line coupled to each cooling system, and a
cooling assembly output line coupled to each of the plurality of
cooling system output lines.
4. The cooling assembly of claim 3 wherein a diameter of the fluid
input line is smaller than a diameter of the cooling assembly
output line.
5. The cooling system of claim 1 further comprising a frame
including a plurality of docking bays, each docking configured to
receive a heat generating electronics device, wherein one of the
plurality of cooling systems is coupled to one of the docking
bays.
6. The cooling assembly of claim 5 wherein each cooling system is
configured to be mounted to the heat generating electronics device
when the heat generating electronics device is mounted within the
docking bay.
7. The cooling assembly of claim 1 wherein each cooling system
comprises one or more heat exchangers configured to pass the
coolant therethrough.
8. The cooling assembly of claim 1 wherein at least a portion of
the coolant undergoes a phase change within the cooling system.
9. The cooling assembly of claim 1 wherein each dynamic fluid flow
regulator is configured to output a constant fluid flow rate in
response to a range of fluid pressures of the coolant within the
fluid input manifold.
10. The cooling assembly of claim 1 wherein the coolant comprises a
refrigerant.
11. The cooling assembly of claim 1 wherein the fluid input
manifold further comprises a plurality of cooling system input
lines, one cooling system input line coupled between one orifice
tube and one cooling system.
12. The cooling assembly of claim 1 wherein each fixed fluid flow
regulator includes one or more filters.
13. A cooling assembly comprising: a. a frame including a plurality
of docking bays, each docking bay configured to receive a heat
generating electronics device; b. a fluid input manifold configured
to supply a coolant in a liquid-phase to each of the plurality of
docking bays, the fluid input manifold comprises: i. a fluid input
line; ii. one or more dynamic fluid flow regulators coupled in
parallel to the fluid input line, wherein each dynamic fluid flow
regulator is configured to provide a variable fluid flow
resistance; and iii. a plurality of orifice tubes, one orifice tube
coupled to each docking bay, wherein the plurality of orifice tubes
are arranged into one or more groups, one group coupled to each
dynamic fluid flow regulator such that all orifice tubes in the
group are coupled in parallel to the dynamic fluid flow regulator,
further wherein each orifice tube is configured to provide a fixed
fluid flow orifice; and c. a fluid output manifold configured to
receive two-phase coolant from each of the plurality of docking
bays.
14. The cooling assembly of claim 13 further comprising a plurality
of fluid-based cooling systems, one fluid-based cooling system
coupled to each docking bay, wherein each fluid-based cooling
system is coupled to the orifice tube coupled to the docking bay
and to the fluid output manifold.
15. The cooling assembly of claim 14 wherein each fluid-based
cooling system is configured to be mounted to the heat generating
electronics device.
16. The cooling assembly of claim 14 wherein each fluid-based
cooling system comprises one or more heat exchangers configured to
pass the coolant therethrough.
17. The cooling assembly of claim 14 wherein the cooling assembly
comprises a two-phase cooling system and at least a portion of the
coolant undergoes a phase change within the fluid-based cooling
system.
18. The cooling assembly of claim 13 wherein each dynamic fluid
flow regulator is configured to output a constant fluid flow rate
in response to a range of fluid pressures of the coolant within the
fluid input manifold.
19. The cooling assembly of claim 13 wherein the coolant comprises
a refrigerant.
20. The cooling assembly of claim 13 wherein the fluid input
manifold further comprises a plurality of docking bay input lines,
one input line coupled between the orifice tube and the docking
bay.
21. The cooling assembly of claim 13 wherein the fluid output
manifold comprises a fluid output line and a plurality of docking
bay output lines coupled to the fluid output line, each docking bay
output line coupled to one docking bay.
22. The cooling assembly of claim 21 wherein a diameter of the
fluid input line is smaller than a diameter of the fluid output
line.
23. The cooling assembly of claim 13 wherein each orifice tube
includes one or more filters.
24. A cooling assembly comprising: a. a plurality of fluid-based
two-phase cooling systems; and b. a fluid input manifold configured
to supply a coolant in a liquid-phase to each of the plurality of
fluid-based cooling systems, the fluid input manifold comprises: i.
a fluid input line; and ii. a plurality of fixed fluid flow
regulators coupled in parallel to the fluid input line, one fixed
fluid flow regulator coupled to each cooling system, wherein each
fixed fluid flow regulator is configured to provide a fixed fluid
flow orifice.
Description
RELATED APPLICATIONS
[0001] This application claims priority of U.S. provisional
application Ser. No. 61/406,084, filed Oct. 22, 2010, and entitled
"IMPROVED FLOW BALANCING SCHEME FOR 2-PHASE REFRIGERANT COOLED
RACK". This application incorporates U.S. provisional application
Ser. No. 61/406,084 in its entirety by reference.
FIELD OF THE INVENTION
[0002] The invention relates to a method of and apparatus for
cooling a heat producing device in general, and specifically, to a
method of and apparatus for cooling server applications using
fluid-based cooling systems.
BACKGROUND OF THE INVENTION
[0003] Cooling of high performance integrated circuits with high
heat dissipation is presenting significant challenge in the
electronics cooling arena. Conventional cooling with heat pipes and
fan mounted heat sinks are not adequate for cooling chips with ever
increasing wattage requirements.
[0004] Electronics servers, such as blade servers and rack servers,
are being used in increasing numbers due to the higher processor
performance per unit volume one can achieve. However, the high
density of integrated circuits also leads to high thermal density,
which is beyond the capability of conventional air-cooling
methods.
[0005] A particular problem with cooling integrated circuits on
electronics servers is that multiple electronics servers are
typically mounted in close quarters within a server chassis. In
such configurations, electronics servers are separated by a limited
amount of space, thereby reducing the dimensions within which to
provide an adequate cooling solution. Typically, stacking of
electronics servers does not provide the mounting of large fans and
heat sinks for each electronics server. Often electronics server
stacks within a single server chassis are cooled with one or more
fans, one or more heat sinks, or a combination of both. Using this
configuration, the integrated circuits on each electronics server
are cooled using the heat sink and the large fan that blows air
over the heat sink, or simply by blowing air directly over the
electronics servers. However, considering the limited free space
surrounding the stacked electronics servers within the server
chassis, the amount of air available for cooling the integrated
circuits is limited.
[0006] As data centers continue to increase their computer density,
electronics servers are being deployed more frequently. Fully
populated electronics servers significantly increase rack heat
production. This requires supplemental cooling beyond what the
Computer Room Air Conditioning (CRAC) units can provide.
Supplemental cooling systems can include fluid based cooling
systems implemented at the server rack level and distributed to
each electronics server mounted within the server rack. In some
applications, the supplemental cooling system distributes cooling
fluid to each docking bay within the server rack, where each
docking bay is configured to receive an electronics server. The
cooling fluid distributed to each docking bay is distributed to
either a discrete fluid based cooling system included within the
received electronics server, or to a discrete fluid based cooling
system that is part of each docking bay where the discrete fluid
based cooling system is thermally coupled to the received
electronics server.
[0007] When providing fluid to a server rack, careful consideration
must be given to the distribution of the cooling fluid within the
rack. Typically, the fluid path contains one or more parallel
paths. If the fluid flow is a singular series path, then for a
single phase fluid the temperature would rise all along the path.
By splitting the fluid into parallel paths, cooler fluid can be
presented to the devices requiring cooling, such as the electronics
servers, and there is an overall lower pressure drop from the
parallel paths.
[0008] To balance the flow for each of the parallel paths, the
fluid pressure drop can be modified such that the appropriate
amount of fluid flows down each path. In some applications, each
path may require the same amount of fluid, which would then require
the same pressure drop. In other applications, each path may have
its own requirement so the resistance is tailored accordingly. This
works fine for a single phase coolant such as water. The fluid path
pressure drop is largely insensitive to the heat load being
applied. However, in a two-phase cooling system, such as a
refrigerant based cooling system, as heat is transferred into the
fluid, a portion of the fluid undergoes a phase change and changes
from liquid to gas. Two-phase cooling systems are often desirable
because the temperature of the two-phase fluid is constant
throughout the fluid pathway, thereby maintaining a heat exchanger
within the cooling system at a substantially constant temperature.
Because the mass flow rate is the same, the gas must travel at
higher velocity which subsequently causes a higher pressure drop.
If there are multiple parallel paths with the same heat load, then
the pressure drop along each path stays largely the same and the
flow rate stays balanced. However, if the heat load is higher on
one path than the other, then the refrigerant flows more toward the
low load path since the low load path has a lower pressure drop. An
example of this may occur within a refrigerant cooled server rack
having multiple electronics servers. If some electronics servers
are powered on and others are powered off, the refrigerant will
naturally flow toward the electronics servers that are powered off
causing the electronics servers that are powered on to overheat.
One method of addressing this issue is using an active valve system
that closes fluid flow to the electronics servers that are off.
This however is expensive and can be prone to failure. Another
method is that the overall fluid flow can be increased to make sure
there is adequate fluid flow in the path with the high heat load,
but this requires a larger fluid pump and more power.
SUMMARY OF THE INVENTION
[0009] A cooling system is configured to distribute fluid to a
plurality of docking bays within a server rack. The server rack is
configured to house multiple electronics servers, each electronics
server mounted within a docking bay of the server rack. The cooling
system is configured with parallel fluid paths, one fluid path to
distribute fluid to one docking bay. A two-phase fluid-based heat
exchanging system is coupled to each docking bay, which functions
to remove heat from an electronics server when mounted in the
docking bay. The docking bays are conceptually divided into one or
more sections, and a dynamic fluid flow regulator is included
within a section input line that supplies a liquid-phase fluid to
each section. The section input line branches into a plurality of
parallel fluid paths, one parallel fluid path coupled to each
docking bay in the section. A fixed fluid flow regulator is
included within each branching fluid pathway. The combination of
the dynamic fluid flow regulators and fixed fluid flow regulators
provides balanced fluid flow to each two-phase heat exchanging
system coupled to the docking bays.
[0010] In an aspect, a cooling assembly is disclosed that includes
a plurality of fluid-based two-phase cooling systems and a fluid
input manifold configured to supply a coolant in a liquid-phase to
each of the plurality of fluid-based cooling systems. The fluid
input manifold includes a fluid input line, one or more dynamic
fluid flow regulators, and a plurality of fixed fluid flow
regulators. The one or more dynamic fluid flow regulators are
coupled in parallel to the fluid input line, wherein each dynamic
fluid flow regulator is configured to provide a variable fluid flow
resistance. The resistance increases with an increase of pressure
on the inlet side. One fixed fluid flow regulator is coupled to
each cooling system. The plurality of fixed fluid flow regulators
are arranged into one or more groups, one group coupled to each
dynamic fluid flow regulator such that all fixed fluid flow
regulators in the group are coupled in parallel to the dynamic
fluid flow regulator, further wherein each fixed fluid flow
regulator is configured to provide a fixed fluid flow orifice.
[0011] In some embodiments, the cooling system also includes a
fluid output manifold configured to receive two-phase coolant from
each of the plurality of cooling systems. In some embodiments, the
fluid output manifold includes a plurality of cooling system output
lines, one cooling system output line coupled to each cooling
system, and a cooling assembly output line coupled to each of the
plurality of cooling system output lines. In some embodiments, a
diameter of the fluid input line is smaller than a diameter of the
cooling assembly output line. In some embodiments, the cooling
system also includes a frame including a plurality of docking bays,
each docking configured to receive a heat generating electronics
device, wherein one of the plurality of cooling systems is coupled
to one of the docking bays. In some embodiments, each cooling
system is configured to be mounted to the heat generating
electronics device when the heat generating electronics device is
mounted within the docking bay. In some embodiments, each cooling
system includes one or more heat exchangers configured to pass the
coolant therethrough. In some embodiments, at least a portion of
the coolant undergoes a phase change within the cooling system. In
some embodiments, each dynamic fluid flow regulator is configured
to output a constant fluid flow rate in response to a range of
fluid pressures of the coolant within the fluid input manifold. In
some embodiments, the coolant is a refrigerant. In some
embodiments, the fluid input manifold also includes a plurality of
cooling system input lines, one cooling system input line coupled
between one orifice tube and one cooling system. In some
embodiments, each fixed fluid flow regulator includes one or more
filters.
[0012] In another aspect, a cooling assembly includes a frame, a
fluid input manifold, and a fluid output manifold. The frame
includes a plurality of docking bays, each docking bay configured
to receive a heat generating electronics device. The fluid input
manifold is configured to supply a coolant in a liquid-phase to
each of the plurality of docking bays. The fluid input manifold
includes a fluid input line, one or more dynamic fluid flow
regulators, and a plurality of orifice tubes. The one or more
dynamic fluid flow regulators are coupled in parallel to the fluid
input line, wherein each dynamic fluid flow regulator is configured
to provide a variable fluid flow resistance. One orifice tube is
coupled to each docking bay. The plurality of orifice tubes are
arranged into one or more groups, one group coupled to each dynamic
fluid flow regulator such that all orifice tubes in the group are
coupled in parallel to the dynamic fluid flow regulator, further
wherein each orifice tube is configured to provide a fixed fluid
flow orifice. The fluid output manifold is configured to receive
two-phase coolant from each of the plurality of docking bays.
[0013] In yet another aspect, a cooling assembly includes a
plurality of fluid-based two-phase cooling systems and a fluid
input manifold configured to supply a coolant in a liquid-phase to
each of the plurality of fluid-based cooling systems. The fluid
input manifold includes a fluid input line and a plurality of fixed
fluid flow regulators coupled in parallel to the fluid input line,
one fixed fluid flow regulator coupled to each cooling system,
wherein each fixed fluid flow regulator is configured to provide a
fixed fluid flow orifice.
[0014] Other features and advantages of the present invention will
become apparent after reviewing the detailed description of the
embodiments set forth below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] Several example embodiments are described with reference to
the drawings, wherein like components are provided with like
reference numerals. The example embodiments are intended to
illustrate, but not to limit, the invention. The drawings include
the following figures:
[0016] FIG. 1 illustrates a side view of a cooling system within an
electronics enclosure with a side panel removed according to an
embodiment.
[0017] FIG. 2 illustrates the fluid input manifold of FIG. 1.
[0018] FIG. 3 illustrates a partially cut out view of an exemplary
orifice tube 14 according to an embodiment.
[0019] FIG. 4 illustrates an isometric view of exemplary two-phase
heat exchanging systems coupled to a partial section of the fluid
input manifold of FIG. 1.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
[0020] Embodiments of the present application are directed to a
cooling system. Those of ordinary skill in the art will realize
that the following detailed description of the cooling system is
illustrative only and is not intended to be in any way limiting.
Other embodiments of the cooling system will readily suggest
themselves to such skilled persons having the benefit of this
disclosure.
[0021] Reference will now be made in detail to implementations of
the cooling system as illustrated in the accompanying drawings. The
same reference indicators will be used throughout the drawings and
the following detailed description to refer to the same or like
parts. In the interest of clarity, not all of the routine features
of the implementations described herein are shown and described. It
will, of course, be appreciated that in the development of any such
actual implementation, numerous implementation-specific decisions
must be made in order to achieve the developer's specific goals,
such as compliance with application and business related
constraints, and that these specific goals will vary from one
implementation to another and from one developer to another.
Moreover, it will be appreciated that such a development effort
might be complex and time-consuming, but would nevertheless be a
routine undertaking of engineering for those of ordinary skill in
the art having the benefit of this disclosure.
[0022] Embodiments of the present application are directed to a
cooling system that distributes fluid to a plurality of docking
bays within a server rack. The cooling system described herein can
be applied to any electronics sub-system, including but not limited
to, a blade server and a rack server, herein referred to
collectively as an electronics server. A server rack is configured
to house multiple electronics servers, each electronics server
mounted within a docking bay of the server rack. Each electronics
server includes one or more heat generating devices as is well
known in the art.
[0023] The cooling system is configured with parallel fluid paths,
one fluid path to distribute fluid to one docking bay. A two-phase
fluid-based heat exchanging system is coupled to each docking bay,
which functions to remove heat from an electronics server when
mounted in the docking bay. One solution to addressing the pressure
drops associated with the two-phase heat exchanging systems is the
use of dynamic fluid flow regulators. In some embodiments, each
parallel fluid path includes a dynamic fluid flow regulator.
However, dynamic fluid flow regulators are expensive and including
a dynamic fluid flow regulator in each parallel fluid path may be
cost prohibitive.
[0024] Another more passive solution is to artificially raise the
pressure drop on each of the parallel fluid paths such that the
pressure change caused by evaporation is a fraction of the overall
pressure drop. Under these conditions, fluid flow remains largely
unaffected preventing starvation of fluid from hot electronics
servers when there are cold electronics servers, or no electronics
server in the case of a vacant docking bay, in a parallel path.
This can be achieved by using a small orifice on each of the
parallel paths or by using a very thin tube of a predetermined
length to artificially raise the pressure drop. The smaller sized
orifice restricts fluid flow. The amount of fluid flow restriction
is a function of the diameter of the small orifice. As the size of
the small orifice is fixed, so is the fluid flow restricted by the
small orifice. In this manner the small orifice functions as a
fixed fluid flow regulator. A problem with an orifice is that it
can become clogged. Also, a small diameter tube can be crushed or
kinked thus preventing flow altogether. A small tube joined to a
large tube can also be a problem for manufacturing. Damage can
occur to the small tube while brazing a small tube to a larger
manifold tube. These issues are addressed by an orifice tube that
includes one or more filters and a smaller diameter fluid line
positioned so as to float within a larger diameter fluid tube. The
fluid is suspended by a support structure that holds both the
filters in place relative to the fluid line and the fluid line in
place relative to the fluid tube.
[0025] Yet another solution is to combine the use of dynamic fluid
flow regulators and fixed fluid flow regulators. This solution
provides a balance fluid flow in each of parallel fluid paths by
using one or more dynamic fluid flow regulators to form smaller
manifolds for fluid distribution. These smaller manifolds, also
referred to as sections, can additionally supply one or more
parallel fluid paths. The fluid paths within each smaller manifold
are modified to include fixed fluid flow regulators. In some
embodiments, the fixed fluid flow regulators are implemented using
orifice tubes. In some embodiments, the orifice tubes are
configured with one or more filters to minimize or prevent blocking
of a small orifice within the orifice tube. Each orifice tube
provides a metered supply of fluid to the two-phase heat exchanging
system of one of the docking bays. By selecting appropriately sized
orifice tubes, the orifice tubes can each function as an
artificially high pressure drop thus minimizing the effect of a
phase change on the overall pressure of a particular fluid pathway.
This maintains a balanced fluid flow along each of the parallel
fluid paths.
[0026] If by design, a different amount of fluid needs to flow down
each pathway, different orifice tubes having different fixed sized
orifices can be selected for each of the fluid pathways. The
orifice tubes are very good for use in manufacturing because they
include sub-assemblies that are completely enclosed within a larger
pipe or tube, where the sub-assemblies include their own filters in
some embodiments. The sub-assembly can have a stop or bend to fix
the sub-assembly in position within the outer tube.
[0027] FIG. 1 illustrates a side view of a cooling system within an
electronics enclosure with a side panel removed according to an
embodiment. An electronics enclosure 2, such as a server rack,
includes a frame 4 configured with a plurality of docking bays 6.
The cooling system includes an external input line interconnect 8,
a server rack input line 10, one or more dynamic fluid flow
regulators 12, a plurality of orifice tubes 14, a plurality of
docking bay input lines 16, a plurality of docking bay output lines
18, a server rack output line 20, and an external output line
interconnect 22. The external input line interconnect 8 and the
external output line interconnect 22 are coupled to an externally
pumped cooling loop (not shown). The cooling system also includes a
plurality of two-phase fluid-based heat exchanging systems shown
and described below in relation to FIG. 4. Each docking bay
includes one of the two-phase fluid-based heat exchanging systems.
In the exemplary configuration shown in FIG. 1, there are 36
docking bays 6. Each docking bay 6 is configured to receive an
electronics server. The cooling system includes a fluid input
manifold configured to receive a liquid-phase fluid from an
external source and to distribute the fluid to the two-phase heat
exchanging system of each of the docking bays 6. The cooling system
also includes a fluid output manifold configured to receive
two-phase fluid from the two-phase heat exchanging system and to
output the two-phase fluid from the cooling system. The fluid
output manifold includes the plurality of docking bay output lines
18, the server rack output line 20, and the external output line
interconnect 22. In some embodiments, the fluid is a coolant, such
as a refrigerant. Alternatively, the coolant is water. It is
understood that other conventional coolants can be used. The fluid
input manifold distributes the fluid using parallel fluid paths
such that each docking bay receives its own supply of fluid.
[0028] The fluid input manifold includes the external input line
interconnect 8, the server rack input line 10, the one or more
dynamic fluid flow regulators 12, the plurality of orifice tubes
14, and the plurality of docking bay input lines 16, shown in part
in FIG. 2. The server rack input line 10 receives fluid from an
external source via the external input line interconnect 8. The
server rack input line 10 branches into one or more section input
lines 24. Each section input line includes a dynamic fluid flow
regulator 12. The plurality of docking bays is conceptually
partitioned into one or more sections, each section is supplied
fluid by a corresponding section input line. In the exemplary
configuration shown in FIGS. 1 and 2, the docking bays are
conceptually partitioned into four section and therefore the fluid
input manifold includes four section input lines 24 and four
dynamic fluid flow regulators 12. Ideally, the server rack input
line has a branch for each docking bay, where each branching
section input line has a dynamic fluid flow regulator with active
control. In this configuration, where there are N docking bays,
there are N section input lines and N dynamic fluid flow
regulators. However, in practice the dynamic fluid flow regulators
are expensive and in many applications such a configuration is cost
prohibitive. Accordingly, the docking bays are organized into
sections, and each section is fitted with a dynamic fluid flow
regulator in its section input line to provide a macro level of
fluid flow control and adding a fixed fluid flow regulator to each
docking bay input line using an orifice tube to provide a micro
level of fluid flow control. In general, the number of section
input lines varies from one to the number of docking bays, for
example 36. The actual number of sections is an implementation
decision.
[0029] A fluid flow regulator is a device that maintains a constant
fluid flow rate over a given pressure range. In this manner, the
fluid flow regulator functions to restrict fluid flow and therefore
is said to have a fluid flow resistance. In the case of a fixed
fluid flow regulator, an orifice size in the fluid pathway is
fixed. In the case of a dynamic fluid flow regulator, an orifice
size in the fluid pathway varies. In some embodiments, the dynamic
fluid flow regulator includes a spring-actuated orifice. If the
pressure is high, then the spring forces the orifice smaller. If
the pressure is low, then the spring forces the orifice larger.
Opening and closing the orifice enables a constant amount of fluid
to flow through the dynamic fluid flow regulator during ranging
pressure conditions. Each dynamic fluid flow regulator is rated to
provide a constant output fluid flow rate for a given range of
fluid pressures. As applied to the dynamic fluid flow regulators 12
in FIGS. 1 and 2, if pressure increases on the pump side (external
side) of the dynamic fluid flow regulator, then the dynamic fluid
flow regulator resists that increase in pressure by reducing the
orifice opening. For example, the dynamic fluid flow regulator
regulates a substantially constant output fluid flow rate when the
input pressure ranges between 2 psi and 36 psi.
[0030] Each section input line 24 branches into a plurality of
orifice tubes 14. There is one orifice tube 14 for each docking bay
6. Each orifice tube 14 functions as fixed fluid flow regulator
having a fixed fluid flow orifice. It is understood that other
configuration can be used to implement a fixed fluid flow
regulator. For example, a fixed fluid flow regulator can be
implemented using a flat disc having a fixed sized orifice.
[0031] FIG. 3 illustrates a partially cut out view of an exemplary
orifice tube 14 according to an embodiment. The orifice tube 14
includes an outer fluid tube 46 with a filter insert. The filter
insert includes an input filter 34, a fluid line 38, and an output
filter 36. Fluid input from the section input line flows through
the input filter 34 and into an input of the fluid line 38. The
fluid flows through and outputs the fluid line 38, and through the
output filter 36. A diameter of the fluid line 38 determines the
fluid flow rate. The diameter remains fixed. The input filter 34
prevents the fluid line from becoming blocked by particulate. The
output filter 36 provides optional additional filtering. The filter
insert includes a support structure 40 and one or more o-rings 44
for securing the filters and the fluid line in position with the
outer fluid tube 46. The outer fluid tube 46 is reamed such that
the interior diameter is larger at the output opening relative to
the input opening to provide a mechanical stop. Ears 42 on the
support structure 40 are configured so as to function as a stop
against the narrowing interior diameter of the outer fluid tube 46.
In this manner, the support structure 40 can be inserted into the
output opening of the outer fluid tube 46 for a predetermined
distance.
[0032] In some embodiments, the orifice size for all orifice tubes
in a given section is the same. In other embodiments, the orifice
size of the orifice tubes in different sections can be the same or
different. In general, each orifice tube can be independently
configured with its own orifice size.
[0033] FIG. 4 illustrates an isometric view of exemplary two-phase
heat exchanging systems coupled to a partial section of the fluid
input manifold of FIG. 1. FIG. 4 shows four independent two-phase
heat exchanging systems, one two-phase heat exchanging system for
each docking bay. Each orifice tube 14 is coupled to the docking
bay input line 16 via a connector 26. In some embodiments, each
two-phase heat exchanging system includes a fluid header 28, a
fluid header 32, and one or more heat exchangers 30. In the
exemplary configuration shown in FIG. 4, there are six heat
exchangers 30. It is understood that more or less than six heat
exchangers can be used. The fluid header 28 is coupled to the
docking bay input line 16 and to the heat exchangers 30 to receive
liquid-phase fluid from the docking bay input line 16 and
distribute the liquid-phase fluid to the heat exchangers 30. The
heat exchangers 30 have fluid pathways through which fluid flows.
The fluid header 28 is also coupled to the docking bay output line
18 to receive two-phase fluid from the heat exchangers 30 and
output the two-phase fluid to the docking bay output line 18.
[0034] The fluid header 28, the heat exchangers 30, and the fluid
header 32 are configured in any manner such that fluid input from
the docking bay input line 16 is distributed through the heat
exchangers 30 to the fluid header 32 and back through the heat
exchangers 30 to the fluid header 28 and output through the docking
bay output line 18. In some embodiments, the fluid header 28, the
heat exchangers 30, and the fluid header 32 are configured to
evenly distribute fluid across the entire area covered by the heat
exchangers 30. In some embodiments, the fluid header 28, the heat
exchangers 30, and the fluid header 32 are configured such that
fluid flows from the fluid header 28 to the fluid header 32 only
through select ones of the heat exchangers 30, and fluid flows from
the fluid header 32 to the fluid header 28 through other select
ones of the heat exchangers 30. In other embodiments, the fluid
header 28, the heat exchangers 30, and the fluid header 32 are
configured such that fluid flows from the fluid header 28 to the
fluid header 32 and from the fluid header 32 to the fluid header 28
in one, some, or all of the heat exchangers 30. In still other
embodiments, the fluid header 28, the heat exchangers 30, and the
fluid header 32 are configured to selectively provide more fluid to
certain areas of select heat exchangers than to other areas so as
to selectively cool hot spots in an electronic server mounted in
the docking bay. In some embodiments, each heat exchanger is a cold
plate. In an exemplary application, a single flexible cold plate is
used which can be flexed into thermal contact with the electronics
server mounted in the docking bay. Such a flexible cold plate is
described in U.S. Pat. No. 8,000,103, which is hereby incorporated
in its entirety by reference.
[0035] The cooling system is configured to operate as a two-phase
cooling system. In such a system, fluid input to the input fluid
manifold is in a liquid phase, and the fluid output from the output
fluid manifold is in a combination of liquid and gas phase. The
fluid remains in the liquid phase until it enters the two-phase
heat exchanging system coupled to the docking bays. In an exemplary
application, the mass flow rate of the fluid through the entire
cooling system is substantially constant. Since fluid in a gas
phase has a greater volume than the same fluid in a liquid phase,
the output lines in the output fluid manifold are configured with a
greater diameter than the input lines within the input fluid
manifold. Accordingly, the server rack input line 10 has a smaller
diameter than the server rack output line 20. In some embodiments,
the docking bay input lines 16 have a smaller diameter than the
docking bay output lines 18. Configuring the components in the
input path with smaller diameters than the components in the output
path functions to alleviate increased pressure due to the phase
change of the fluid from liquid to gas.
[0036] By using the combination of the dynamic fluid flow
regulators and the fixed fluid flow regulators, fluid flow is
regulated such that there is substantially equal fluid flow to each
docking bay despite the level of heat generated by the individual
electronics servers mounted within the docking bays, even when one
or more docking bays are unoccupied. In conventional
configurations, fluid flow to the unoccupied docking bays would
increase and fluid flow to the occupied docking bays would decrease
due to the lower pressure drop corresponding to the unoccupied
docking bays and the higher pressure drop corresponding to the
occupied docking bays.
[0037] Using a dynamic fluid regulator enables load balancing of
fluid provided to each docking bay. In other words, the fluid flow
rate provided to each section is dynamically adjusted to assure the
same fluid flow rate is provided to each section under changing
conditions. For example, during an initial installation, only a few
electronics servers may be loaded into the server rack. As more
electronics servers are added to a given section, there is a
greater amount of pressure drop as more heat is being generated by
the additional electronics servers. If the load is not balanced
between sections of the server rack, then more fluid would be
diverted away from the section having the higher pressure drop. The
dynamic flow regulators assure that a constant fluid flow rate is
supplied to each orifice tube in the section. In this manner, the
fluid input manifold enables constant fluid flow from low load to
high load situations.
[0038] The gross fluid flow balancing is happening via the dynamic
fluid flow regulators, by branching the input line into sections.
The finer balancing is achieved using the orifice tubes. The output
from the dynamic fluid flow regulator provides a constant fluid
flow and therefore provides an equal opportunity for each docking
bay in the section supplied by the dynamic fluid flow regulator to
receive the same amount of fluid. Some of the docking bays may be
occupied and some may be unoccupied, and some of the electronics
servers in the occupied docking bays may be generating more heat
than others due to their current level of operation. Such
conditions conventionally cause fluid distribution difficulties
because due to pressure drops the fluid would flow to those
electronics servers generating the least amount of heat. By adding
the fixed fluid flow orifice of the orifice tubes, the fluid flow
to the docking bay input lines is balanced. The pressure drop is
dominated by the orifice tube instead of any heat exchanging system
used to cool the electronics server mounted in the docking bay. In
an exemplary application, the server rack is able to provide 600
watts of cooling to each docking bay regardless of whether the
docking bay is occupied or unoccupied, or the level of operation of
an electronics server mounted within the docking bay.
[0039] Equal fluid flow distribution to each docking bay is
achieved as long as the fluid delivered to each docking bay does
not completely evaporate. In such a case, a two-phase condition no
longer exists in the heat exchanging system and the increasing
pressure leads to reduced fluid flow. As such, it is important to
only install electronics servers properly rated to be cooled by the
server rack or to a particular docking bay within the server rack,
as will be described in greater detail below. For example, a 1
kilowatt electronic server should not be installed into a server
rack where each docking bay is rated to cool a 600 watt electronic
server. An exemplary server rack is a 20 kilowatt rack, and the
four dynamic fluid flow regulators have a fluid flow rate of 0.5
GPM (gallon per minute) flow. The fluid flow rates of the dynamic
fluid flow regulators and the orifice tubes determine the cooling
capacity of the server rack.
[0040] In some embodiments, each dynamic fluid flow regulator has
the same rating, for example each flow regulator is a 0.5 GPM flow
regulator. In other embodiments, one or more dynamic fluid flow
regulators can have a different ratings. Having different types of
dynamic fluid flow regulators enables different rated electronics
servers to be loaded into the server rack.
[0041] Design flexibility is enabled by choosing dynamic fluid flow
regulators having desired fluid flow rates, changing the diameter
of the fluid line within the orifice tubes, or a combination of the
two. Additionally, not all of the dynamic fluid flow regulators
need have the same fluid flow rate. Similarly, not all of the
orifice tubes need have the same sized orifices. For example,
although the four dynamic fluid flow regulators shown and described
in regard to FIGS. 1-4 are chosen to have the same fluid flow rate,
one or more of the dynamic fluid flow regulators can be selected
having different fluid flow rates. Similarly, one or more of the
orifice tubes can be have different diameter fluid lines within a
given section, or from section to section. The cooling capacity for
a given docking bay is a function of the fluid flow rates for both
the dynamic fluid flow regulator and the orifice tube for the input
fluid path to the docking bay. Any such combination of dynamic
fluid flow regulator and orifice tube is considered as long as the
corresponding electronics server is rated to the cooling capacity
of the specific docking bay.
[0042] The combination of dynamic fluid flow regulators and orifice
tubes provides an optimization of balancing fluid flow, minimizing
costs, achieving the desired manufacturability, and reliability
with the filtering.
[0043] Although the first stage fluid flow regulators, such as the
fluid flow regulators 12, are shown and described above as dynamic
fluid flow regulators, the cooling system can be alternatively
configured such that one or more of these fluid flow regulators are
fixed fluid flow regulators.
[0044] Although the cooling system is described above as a
two-stage configuration having a first stage dynamic fluid flow
regulator and a second stage fixed fluid flow regulator, certain
applications are also contemplated in which the cooling system has
a single stage configuration. In such a single-stage
implementation, fluid flow rates, flow rate requirements in the
docking bays, and/or the number of docking bays are such that only
a single fixed fluid flow regulator is implemented in the fluid
pathway to each docking bay. In some embodiments, where there are N
docking bays, the server rack input line branches into N parallel
input lines, each input line having a fixed fluid flow
regulator.
[0045] The present application has been described in terms of
specific embodiments incorporating details to facilitate the
understanding of the principles of construction and operation of
the cooling system. Many of the components shown and described in
the various figures can be interchanged to achieve the results
necessary, and this description should be read to encompass such
interchange as well. As such, references herein to specific
embodiments and details thereof are not intended to limit the scope
of the claims appended hereto. It will be apparent to those skilled
in the art that modifications can be made to the embodiments chosen
for illustration without departing from the spirit and scope of the
application.
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