U.S. patent application number 11/209241 was filed with the patent office on 2007-03-01 for systems and methods for cooling electronics components employing vapor compression refrigeration with selected portions of expansion structures coated with polytetrafluorethylene.
This patent application is currently assigned to International Business Machines Corporation. Invention is credited to Daniel J. Kearney, Mark A. Marnell, Donald W. Porter.
Application Number | 20070044493 11/209241 |
Document ID | / |
Family ID | 37709442 |
Filed Date | 2007-03-01 |
United States Patent
Application |
20070044493 |
Kind Code |
A1 |
Kearney; Daniel J. ; et
al. |
March 1, 2007 |
Systems and methods for cooling electronics components employing
vapor compression refrigeration with selected portions of expansion
structures coated with polytetrafluorethylene
Abstract
Systems and Methods of cooling heat generating electronics
components are provided employing vapor compression refrigeration.
In one embodiment, the vapor compression refrigeration system
includes a condenser, at least one expansion structure, at least
one evaporator, and a compressor coupled in fluid communication to
define a refrigerant flow path, and allow the flow of refrigerant
therethrough. The at least one evaporator is coupled to the at
least one heat generating electronics component to facilitate
removal of heat produced by the electronics component. At least a
portion of the at least one expansion structure is coated with a
polytetrafluorethylene in the refrigerant flow path for inhibiting
accumulation of material thereon. The polytetrafluorethylene
coating has a thickness sufficient to inhibit accumulation of
material in a pressure drop area of the expansion structure without
significantly changing a pressure drop characteristic of the
pressure drop area.
Inventors: |
Kearney; Daniel J.; (Ulster
Park, NY) ; Marnell; Mark A.; (Kingston, NY) ;
Porter; Donald W.; (Highland, NY) |
Correspondence
Address: |
HESLIN ROTHENBERG FARLEY & MESITI P.C.
5 COLUMBIA CIRCLE
ALBANY
NY
12203
US
|
Assignee: |
International Business Machines
Corporation
Armonk
NY
|
Family ID: |
37709442 |
Appl. No.: |
11/209241 |
Filed: |
August 23, 2005 |
Current U.S.
Class: |
62/259.2 ;
236/92B |
Current CPC
Class: |
Y02B 30/70 20130101;
F25B 5/02 20130101; F25B 2500/04 20130101; F25B 41/35 20210101;
F25B 41/31 20210101 |
Class at
Publication: |
062/259.2 ;
236/092.00B |
International
Class: |
F25B 41/06 20060101
F25B041/06; F25D 23/12 20060101 F25D023/12 |
Claims
1. A cooling system for cooling at least one heat generating
electronics component, the cooling system comprising: a vapor
compression refrigeration system, the vapor compression
refrigeration system comprising a condenser, at least one expansion
structure, at least one evaporator, and a compressor coupled in
fluid communication to define a refrigerant flow path and allow the
flow of refrigerant therethrough; and wherein the at least one
evaporator facilitates removal of heat produced by the at least one
heat generating electronics component, and wherein at least a
portion of the at least one expansion structure is coated with a
polytetrafluorethylene in the refrigerant flow path for inhibiting
accumulation of material thereon.
2. The cooling system of claim 1, wherein the at least a portion of
the at least one expansion structure comprises a pressure drop area
of the at least one expansion structure.
3. The cooling system of claim 2, wherein the vapor compression
refrigeration system comprises multiple expansion structures
coupled in the refrigeration path, each expansion structure
comprising a pressure drop area coated with a
polytetrafluorethylene in the refrigerant flow path.
4. The cooling system of claim 2, wherein the
polytetrafluorethylene coating has a thickness sufficient to
inhibit accumulation of material in the pressure drop area without
changing a pressure drop characteristic of the pressure drop
area.
5. The cooling system of claim 1, wherein the at least one
expansion structure comprises an expansion valve including an
expansion pin and an expansion orifice defining a pressure drop
area, and wherein the pressure drop area is coated with a
polytetrafluorethylene in the refrigerant flow path.
6. The cooling system of claim 5, wherein the expansion valve is an
electronic expansion valve.
7. A vapor compression refrigeration cooling system for cooling at
least one heat generating electronics component, the cooling system
comprising: a condenser; a first electrically controlled expansion
valve coupled to the condenser; a first evaporator coupled to the
first electrically controlled expansion valve; a second
electrically controlled expansion valve coupled to the condenser; a
second evaporator coupled to the second electrically controlled
expansion valve; a controller providing control signals to the
first electrically controlled expansion valve and the second
electrically controlled expansion valve to control operation of the
first electrically controlled expansion valve and the second
electrically controlled expansion valve; a compressor coupled to
the first evaporator, the second evaporator and the condenser; and
wherein the condenser, the first electrically controlled expansion
valve, the first evaporator, the second electrically controlled
expansion valve, the second evaporator, and the compressor are
coupled in fluid communication to define multiple refrigerant flow
paths, each refrigerant flow path allowing the flow of refrigerant
therethrough, and wherein the first evaporator and the second
evaporator facilitate removal of heat produced by the at least one
heat generating electronics component, and wherein at least a
portion of the first electrically controlled expansion valve and at
least a portion of the second electrically controlled expansion
valve are coated with a polytetrafluorethylene in respective
refrigerant flow paths for inhibiting accumulation of material
thereon.
8. The cooling system of claim 7, wherein the at least a portion of
the first electrically controlled expansion valve comprises a
pressure drop area of the first electrically controlled expansion
valve, and wherein the at least a portion of the second
electrically controlled expansion valve comprises a pressure drop
area of the second electrically controlled expansion valve.
9. The cooling system of claim 8, wherein the pressure drop areas
comprise areas where refrigerant expansion occurs during a vapor
compression cycle of the vapor compression refrigeration
system.
10. The cooling system of claim 8, wherein the
polytetrafluorethylene coating has a thickness sufficient to
inhibit accumulation of material in the pressure drop areas without
changing pressure drop characteristics of the pressure drop
areas.
11. The cooling system of claim 7, wherein the first electrically
controlled expansion valve comprises a first expansion pin and a
first expansion orifice defining a first pressure drop area, and
wherein the second electrically controlled expansion valve
comprises a second expansion pin and a second expansion orifice
defining a second pressure drop area, and wherein the first
pressure drop area and the second pressure drop area are coated
with a polytetrafluorethylene in the refrigerant flow path.
12. The cooling system of claim 7, wherein the cooling system is
for cooling multiple heat generating electronics components, and
wherein the first evaporator facilitates removal of heat produced
by a first electronics component of the multiple heat generating
electronics components and the second evaporator facilitates
removal of heat produced by a second electronics component of the
multiple heat generating electronics components.
13. A method of fabricating a vapor compression refrigeration
system for cooling at least one heat generating electronics
component, the method comprising: (i) providing a condenser, at
least one expansion structure, at least one evaporator, and a
compressor; (ii) providing a polytetrafluorethylene coating on at
least a portion of the at least one expansion structure; (iii)
coupling the condenser, at least one expansion structure, at least
one evaporator and compressor in fluid communication to define a
refrigerant flow path; and (iv) providing refrigerant within the
refrigerant flow path of the vapor compression refrigeration system
to allow for cooling of the at least one heat generating
electronics component employing sequential vapor compression
cycles, wherein the polytetrafluorethylene coating is provided on
the at least a portion of the at least one expansion structure in
the refrigerant flow path for inhibiting the accumulation of
material thereon.
14. The method of claim 13, wherein the providing (ii) comprises
providing the polytetrafluorethylene coating on a pressure drop
area of the at least one expansion structure.
15. The method of claim 14, wherein the providing (i) comprising
providing multiple expansion structures, and wherein the coupling
(iii) comprises coupling the multiple expansion structures in the
refrigerant flow path, each expansion structure comprising a
pressure drop area coated with a polytetrafluorethylene in the
refrigerant flow path.
16. The method of claim 14, wherein the providing (ii) comprises
providing the polytetrafluorethylene coating with a thickness
sufficient to inhibit accumulation of material in the pressure drop
area without changing a pressure drop characteristic of the
pressure drop area.
17. The method of claim 13, wherein the providing (i) comprises
providing an expansion valve as the at least one expansion
structure, the expansion valve including an expansion pin and an
expansion orifice defining a pressure drop area, and wherein the
providing (ii) comprises providing the polytetrafluorethylene
coating in the pressure drop area in the refrigerant flow path.
18. The method of claim 17, wherein the providing (i) comprises
providing an electronic expansion valve as the expansion valve.
Description
TECHNICAL FIELD
[0001] The present invention relates generally to heat transfer
mechanisms, and more particularly, to cooling systems and methods
for removing heat generated by one or more heat generating
electronics components. More particularly, the present invention
relates to cooling systems and methods employing vapor compression
refrigeration.
BACKGROUND OF THE INVENTION
[0002] As is known, operating electronic devices produce heat. This
heat should be removed from the devices in order to maintain device
junction temperatures within desirable limits. Failure to remove
produced heat results in increased device temperatures, potentially
leading to thermal runaway conditions. Several trends in the
electronics industry have combined to increase the importance of
thermal management, including heat removal for electronics devices,
particularly in technologies where thermal management has
traditionally been less of a concern, such as CMOS. In particular,
the need for faster and more densely packed circuits has had a
direct impact on the importance of thermal management. First, power
dissipation, and therefore heat production, increases as device
operating frequencies increase. Second, increased operating
frequencies may be possible at lower device junction temperatures.
Further, as more and more devices are packed onto a single chip,
power density (Watts/cm.sup.2) increases, resulting in the need to
remove more power from a given size chip or module. Additionally, a
common packaging configuration for many large computer systems
today is a multi-drawer rack, with each drawer containing one or
more processor modules along with associated electronics, such as
memory, power and hard drive devices. These drawers are removable
units so that in the event of failure of an individual drawer, the
drawer may be removed and replaced in the field. A problem with
this configuration is the increase in heat flux at the electronics
drawer level. The above-noted trends have combined to create
applications where it is no longer desirable to remove heat from
modem devices solely by traditional air cooling methods, such as by
using traditional air cooled heat sinks. These trends are likely to
continue, furthering the need for alternatives to traditional air
cooling methods.
[0003] One approach to avoiding the limitations of traditional air
cooling is to use a cooling liquid. As is known, different liquids
provide different cooling characteristics. For example,
refrigerants or other dielectric fluids (e.g., fluorocarbon fluid)
may have an advantage in that they may be placed in direct physical
contact with electronic devices and interconnects without adverse
affects such as corrosion or electrical short circuits. For
example, U.S. Pat No. 6,052,284, entitled "Printed Circuit Board
with Electronic Devices Mounted Thereon", describes an apparatus in
which a dielectric liquid flows over and around several operating
electronic devices, thereby removing heat from the devices. Similar
approaches are disclosed in U.S. Pat. No. 5,655,290, entitled
"Method for Making a Three-Dimensional Multichip Module" and U.S.
Pat. No. 4,888,663, entitled "Cooling System for Electronic
Assembly".
[0004] Notwithstanding the above, there remains a large and
significant need to provide further useful cooling system
enhancements for facilitating cooling of heat generating
electronics components, such as one or more electronics modules
disposed, e.g., in a book of an electronics rack of a computer
installation.
SUMMARY OF THE INVENTION
[0005] In vapor compression refrigeration systems employed for
cooling one or more heat generating electronics components, it has
been discovered that material can agglomerate in certain pressure
drop areas of expansion structures within the vapor compression
refrigeration system. During refrigerant/oil transport through a
hot compressor, any long-chain molecules and other typically
non-soluble compounds at room temperature can go into solution in
the hot mixture. These, as well as other physically transported
impurities, then fall out of solution when the refrigerant/oil
cools down. A layer of "waxy" material can build up in the pressure
drop areas and act as a sticky substance which then catches other
impurities. This material has been found to amass on expansion
structures such as expansion valves, and particularly on the pin
and orifice control region in the refrigerant flow path of the
expansion valve. This amassing of material can interfere with the
normal control volumes and interfere with the control of motor
steps (due to unpredictable valve characteristic changes). This is
particularly true when the vapor compression refrigeration system
is employed in a cooling application for removing heat from a heat
generating electronics component as described herein since control
of the valve in this environment is a very sensitive application
and expansion structure geometries are typically very small. To
eliminate all contaminants from the vapor compression refrigeration
system would be too costly, if not impossible. Thus, presented
herein is a solution based on coating only selected pressure drop
areas of the vapor compression refrigeration system to eliminate or
reduce the clogging effect of debris and impurities in critically
tight areas. This application is particularly significant in a
cooling system where little of the expansion valve's available
valve volume is employed during a vapor compression cycle.
[0006] The shortcomings of the prior art and additional advantages
are provided through the provision of a cooling system for cooling
at least one heat generating electronics component. The cooling
system includes a vapor compression refrigeration system. The vapor
compression refrigeration system has a condenser, at least one
expansion structure, at least one evaporator and a compressor all
coupled in fluid communication to define a refrigerant flow path
and allow the flow of refrigerant therethrough. The at least one
evaporator facilitates removal of heat produced by the at least one
heat generating electronics component, while at least a portion of
the at least one expansion structure is coated with a
polytetrafluorethylene in the refrigerant flow path. The
polytetrafluorethylene coating inhibits accumulation of material on
selected pressure drop surfaces of the at least one expansion
structure.
[0007] In another embodiment, a vapor compression refrigeration
cooling system is provided for cooling at least one heat generating
electronics component. This cooling system includes: a condenser, a
first electrically controlled expansion valve coupled to the
condenser, a first evaporator coupled to the first electrically
controlled expansion valve; a second electrically controlled
expansion valve coupled to the condenser, a second evaporator
coupled to the second electrically controlled expansion valve; a
controller providing control signals to the first electrically
controlled expansion valve and the second electrically controlled
expansion valve to control operation of the first electrically
controlled expansion valve and the second electrically controlled
expansion valve; and a compressor coupled to the first evaporator,
the second evaporator and the condenser. The condenser, the first
electrically controlled expansion valve, the first evaporator, the
second electrically controlled expansion valve, the second
evaporator, and the compressor are coupled in fluid communication
to define multiple refrigerant flow paths, each refrigerant flow
path allowing flow of refrigerant therethrough. The first
evaporator and the second evaporator facilitate removal of heat
produced by the at least one heat generating electronics component.
At least a portion of the first electrically controlled expansion
valve and at least a portion of the second electrically controlled
expansion valve are coated with a polytetrafluorethylene in the
respective refrigerant flow paths for inhibiting accumulation of
material thereon.
[0008] In a further aspect, a method of fabricating a vapor
compression refrigeration system for cooling at least one heat
generating electronics component is provided. The method includes:
(i) providing a condenser, at least one expansion structure, at
least one evaporator, and a compressor; (ii) providing a
polytetrafluorethylene coating on at least a portion of the at
least one expansion structure; (iii) coupling the condenser, at
least one expansion structure, at least one evaporator and
compressor in fluid communication to define a refrigerant flow
path; and (iv) providing refrigerant within the refrigerant flow
path of the vapor compression refrigeration system to allow for
cooling of the at least one heat generating electronics component
employing sequential vapor compression cycles, wherein the
polytetrafluorethylene coating is provided on the at least a
portion of the at least one expansion structure in the refrigerant
flow path for inhibiting the accumulation of material thereon.
[0009] 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
[0010] 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:
[0011] FIG. 1 depicts one embodiment of a cooling system comprising
a vapor compression refrigeration system, in accordance with an
aspect of the present invention;
[0012] FIG. 2 illustrates one example of a flowchart that shows how
a Modular Refrigeration Unit (MRU) code which contains a method to
monitor and regulate multi-chip module (MCM) temperature under
primary MRU cooling, a power control code (PCC) which contains a
method to determine and communicate the thermal state or range that
equates to a specific temperature and voltage condition, and a
Cycle Steering Application (CSA) code which contains a method of
matching the various logic clocks to the thermal degrade states
that exist, may interact in a single temperature-power-logic
control system, in accordance with an aspect of the present
invention;
[0013] FIG. 3 depicts a system schematic where the MRU code, PCC
code, and CSA code are physically located in a server having four
processor books or nodes, cooled in primary mode by two MRUs, and
in back-up mode by blowers, in accordance with an aspect of the
present invention;
[0014] FIG. 4 is a cross-sectional, elevational view of one
embodiment of an expansion structure comprising an expansion valve
having an expansion pin and an expansion orifice which are part of
a refrigerant flow path of a vapor compression refrigeration
cooling system, in accordance with an aspect of the present
invention;
[0015] FIG. 5 is an enlarged, cross-sectional view of the expansion
orifice and expansion pin illustrated in FIG. 4, in accordance with
an aspect of the present invention;
[0016] FIG. 6 is an isometric view of one embodiment of an
expansion pin for of an expansion valve of a vapor compression
refrigeration system, wherein material/debris is shown amassed on
exposed surfaces of the expansion pin, which would be in a pressure
drop area of the refrigerant flow path (not shown);
[0017] FIG. 7 is an isometric view of an expansion pin of an
expansion valve of a vapor compression refrigeration system,
wherein the expansion pin is coated with a layer of
polytetrafluorethylene in pressure drop areas the refrigerant flow
path, in accordance with an aspect of the present invention;
and
[0018] FIG. 8 is a cross-sectional, elevational view of an
expansion orifice and expansion pin of an expansion valve of a
vapor compression refrigeration system showing selected pressure
drop areas of the expansion pin and inner surface of the expansion
orifice coated with a polytetrafluorethylene, in accordance with an
aspect of the present invention.
BEST MODE FOR CARRYING OUT THE INVENTION
[0019] As used herein, the term "electronics rack" includes any
frame, rack, blade server system, etc., having at least one heat
generating electronics component 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 books, each
book having one or more heat generating electronics components
requiring cooling. Each "heat generating electronics component" may
comprise an electronic device, an electronics module, an integrated
circuit chip, a multi-chip module, etc. An "expansion structure" is
any structure or area in a vapor compression refrigeration system
where there is a pressure drop, and thus refrigerant expansion
during a refrigerant compression/expansion cycle. As used herein,
the term "expansion structure" includes any structure of a pressure
drop area and adjacent areas where an agglomeration would effect an
expansion structure characteristic, including any thermally
effected conduction zones and any downstream mass transport zones.
Examples of expansion structures include expansion valves,
including electronic expansion valves, thermal expansion valves,
hot-gas bypass valves, or mechanical expansion valves, as well as
other refrigerant expansion structures such as a fixed expansion
orifice in an evaporator. As used herein, an "expansion orifice"
means any opening defined by a component within the vapor
compression refrigeration system, and includes a fixed orifice in
an evaporator, as well as an opening defined by an inner surface of
an expansion valve. Further, the word "refrigerant" is used herein
to refer to any coolant which can be employed in a vapor
compression/expansion system.
[0020] One example of refrigerant within a cooling system in
accordance with an aspect of the present invention is R-134A
coolant (i.e., 1,1,1,2 tetrafluoroethane), however, the concepts
disclosed herein are readily applied to other types of
refrigerants, other dielectric fluids (e.g., fluorocarbon fluid),
or other types of coolants while still maintaining the advantages
and unique features of the present invention.
[0021] FIG. 1 depicts a cooling system 100 as an exemplary
embodiment of the present invention. Cooling system 100 includes a
condenser 104 and two evaporators 106 and 108. Evaporators 106 and
108 cool heat generating electronics components 110 and 112,
respectively. In this embodiment, components 110 and 112 are
multi-chip modules (MCMs), but it is understood that other
components (e.g., single processors, memory) may be similarly
cooled.
[0022] Both evaporators 106 and 108 are supplied refrigerant from a
common condenser 104. An expansion valve 114 receives high pressure
liquid refrigerant from condenser 104 and generates low pressure
liquid refrigerant to evaporator 106. An expansion valve 116
receives high pressure liquid refrigerant from condenser 104 and
generates low pressure liquid refrigerant to evaporator 108.
Expansion valves 114 and 116 are electrically controllable. A
controller 120 provides control signals to expansion valve 114 and
expansion valve 116 to control refrigerant flow and pressure drop
across each expansion valve. In an exemplary embodiment, expansion
valves 114 and 116 each includes a stepper motor that responds to
control signals from the controller 120. The stepper motor opens or
closes an orifice in the expansion valve to regulate refrigerant
flow and pressure drop. Controller 120 executes a computer program
to control the expansion valves 114 and 116.
[0023] The low pressure liquid refrigerant exits the expansion
valves 114 and 116 and is supplied to evaporators 106 and 108,
respectively. The refrigerant in each evaporator 106 and 108 is
converted to low pressure vapor refrigerant, in part, though
further fixed expansion structures 107, 109, respectively, and
provided to a common compressor 122. High pressure vapor from
compressor 122 is supplied to condenser 104. Fan 126 establishes
air flow across condenser 104 to facilitate cooling the high
pressure vapor refrigerant to high pressure liquid refrigerant.
[0024] A plurality of temperature sensors are distributed
throughout the cooling system 100. The sensors may be thermistors
or other known temperature sensors. Sensor T1 measures air
temperature entering condenser 104. Sensor T2 measures air
temperature exiting condenser 104. Sensors T3 and T3' provide
redundant measurement of refrigerant temperature exiting condenser
104. Sensor T4 measures refrigerant temperature entering condenser
104. Sensor T6 measures refrigerant temperature entering evaporator
106 and sensor T7 measures refrigerant temperature exiting
evaporator 106. Sensor T8 measures refrigerant temperature entering
evaporator 108 and sensor T9 measures refrigerant temperature
exiting evaporator 108. Sensor T.sub.hat1 measures temperature at
electronics component 110 and sensor T.sub.hat2 measures
temperature at electronics component 112.
[0025] Each temperature sensor generators a temperature signal
which is supplied to controller 120 and shown as T.sub.in. The
control 120 adjust the expansion valves 114 and/or 116 in response
to one or more of the temperature signals to maintain the logic
modules 110 and 112 at a predefined temperature. Controller 120
controls expansion valves 114 and/or 116 to obtain desired
superheat valves while maintaining each electronics component at a
desired temperature. Each component 110 and 112 may be maintained
at a different temperature or the same temperature, even if each
component has different heat loads.
[0026] Evaporators 106 and 108 may be connected to the refrigerant
supply and refrigerant return lines through quick disconnect
connectors 130. The controllable expansion valves 114 and 116 allow
an evaporator to be removed for maintenance or upgrade while the
other evaporator, condenser and compressor continue to operate. For
example, expansion valve 114 can be closed and the refrigerant from
evaporator 106 removed by the suction of the compressor 122.
Evaporator 106 can then be removed for service, upgrade, etc.
[0027] Although two evaporators are shown connected to one modular
refrigeration unit (MRU) (condenser, compressor, expansion valves
and controller), it is understood that more than two evaporators
may be coupled to each MRU.
[0028] In an exemplary embodiment in accordance with the present
invention, one embodiment joins methods to monitor and control the
temperatures of electronics components 110, 112, to report the
temperature state and to adjust the voltage levels appropriately
and to adjust the various clock speeds which govern CMOS circuits
that are effected by the change in temperature and/or voltage.
[0029] A detailed description of one method of monitoring and
controlling the temperature of a hybrid cooling system 100 is
described below with reference to FIGS. 2 and 3. FIG. 2 illustrates
a flowchart that shows how a Modular Refrigerant Unit (MRU) code
200, which contains a method to monitor and regulate the MCM (i.e.,
one example of a component) temperature under primary MRU cooling,
interfaces with a Power Control Code (PCC) 210, which contains a
method to determine and communicate the thermal state or range that
equates to a specific temperature and voltage condition of each
MCM, and a Cycle Steering Application (CSA) code 220, which
contains the method of matching the various logic clocks to the
thermal degrade state that exist. The MRU code, PCC code and CSA
code, all interact into a single temperature-power-logic control
system generally indicated as 230.
[0030] FIG. 3 shows one embodiment of a system schematic wherein
the MRU code 200, the PCC code 210 and the CSA code 220 are
physically located in a server that has four Processor (PU) books
or nodes 242, 244, 246, 248, respectively, each having an
electronics component or MCM cooled in primary mode by one of two
MRUs 250, 252 and in backup mode by two blowers 254. The backup
blowers 254 provide air cooling of all PU books 242, 244, 246, 248,
for MRU failures or light logic load state. Each MCM is operably
connected to a main system board generally indicated at 256. The
MRU code 200 is in each MRU 250, 252. The PCC code 210 is split
between Base Power Cage Controllers or Base Power Assembly 260, 262
and digital converter assemblies (DCA) cage controllers (DCA 01,
02, 11, 12, 21, 22, 31, 32). The Base Power Assembly 260, 262
provides high voltage DC power to the entire server 240 and the DCA
converts the high DC power to low DC voltages used by each circuit.
The CSA code 220 is located in the first Processor book 244
(labeled PU Book 0) of multi-node server 240.
[0031] Each MCM (not shown) in each PU book 242-248 includes a hat
274 in operable communication with a cooling unit 10 and connected
to a thermal sensor assembly 276. Each thermal sensor assembly 276
preferably includes three thermistors configured to sense a
temperature of a corresponding MCM.
[0032] The thermal sensors are compared for miscompare properties
and for insanity limits to make sure the temperatures measured are
accurate. One sensor is directly sensed by the Modular
Refrigeration Unit (MRU) indicated generally at 278 and the other
two are read by the power supply feeding the MCM power indicated
generally at 280 to insure full redundancy and accuracy of this
reading. The MRU reads an MCM hat thermistor sensor directly
through its drive card to enable continual monitoring and thermal
regulation in case of a cage controller (cc) failover. MCM hat
thermistors that are read by each DCA power supply as well as by
the MRU are compared to each other by the MRU and Power Control
Code to identify any faulty sensors and eliminate the faulty
sensors from consideration generally indicated at 286 in FIG. 2.
This insures redundancy of control and cooling status function. The
power supply thermistor also serves for thermal protection of the
MCMs, dropping power if the temperatures are near damage
limits.
[0033] The control of the primary cooling system is done by using a
Proportional Integral Derivative (PID) control loop of an
electronic expansion valve to each evaporator as described with
reference to FIG. 1 and generally indicated at 290 in FIG. 2. The
PID control loop regulates the coolant flow to each MCM being
cooled. The coolant flow is increased by opening the electronic
expansion valve if the MCM is too warm or is higher than targeted
and the flow is reduced by closing the valve position if the MCM is
too cold or cooler than targeted.
[0034] When the PID control has opened its electronic expansion
valve to the fully open position providing maximum coolant to a
given MCM, the compressor speed then executes its own PID control
loop to deliver additional cooling capacity to the MCM. In other
words, a second PID control loop controls the compressor speed if
the valve regulating the flow of coolant to a respective evaporator
has reached its maximum cooling position.
[0035] Similarly, the blower speed of blower 126 cooling the
refrigerant condenser 104 is controlled by the cooling capacity
needs from the MRU. More specifically, blower speed controls
provide more air for cooling the MRU condenser 104 when the
thermistors T1 and T2 on the condenser 103 and ambient air indicate
that inadequate condensing is taking place. Also, the speed of
condenser blower 126 is increased in a warm ambient.
[0036] MCM power data 284, read by the Power Control Code 210 and
provided to the MRU code 200 every 2.5 seconds, determines if a
given MCM no longer has its clocks functioning. If the MCM power
stays low, indicating a non-functional Processor book, for
sufficient time, the refrigerant coolant supply is stopped by
completely closing the expansion valve to that MCM only and turning
on the backup blowers 254 at a reduced speed. In this manner, other
MCMs in the same server can stay refrigerant cooled while the MCM
that has check stopped or otherwise ceased to function logically
will be air cooled. Refrigerant cooling and MCM without adequate
logic power can lead to condensation forming on its external
surfaces. For example, when regulating light heat loads to a fixed
temperature, the expansion device must significantly close the
refrigerant flow rate, which lowers the pressure and hence the
refrigerant temperature inside the evaporator cooling the MCM. When
the clocks are off, the expansion valve closes so far that the
evaporator pressure may be sub-atmospheric, which creates very cold
local temperatures. These cold local temperatures with low heat
flux and outside regions of the MCM can get cold enough to form
condensate after extended operation in this condition.
[0037] The MRU code 200 also provides a function that enables
virtually all of the refrigerant to be removed from the evaporator
of a corresponding cooling unit before the refrigerant lines are
opened for servicing the MCM or cooling hardware, as discussed
above with respect to FIG. 1. This is provided by closing the
electronic expansion valves for some period before turning off the
compressor, resulting in a partial vacuum that removes the
refrigerant from the evaporator and connecting hoses, The benefits
include better ecology and consistent refrigerant charge before and
after the MRU is reconnected.
[0038] This temperature control code, together with primary and/or
secondary cooling hardware, has the ability to program and run the
MCMs at different or "biased" conditions to enable the MCM to be
tested beyond the normal temperature conditions it sees in actual
use. The temperature bias testing may be done while the logic
voltage is also biased. In the prior art, these bias cooling
functions required special tester cooling hardware and test code
which was costly and inefficient compared to combining this stress
test thermal function in the actual cooling system. Secondary
cooling uses a PID loop also to achieve MCM temperature target that
may be outside of the normal operating range.
[0039] Still referring to FIGS. 2 and 3, a detailed description of
the Power Contol Code (PCC) 210 which principally includes a method
for monitoring the actual thermal or degrade state and for making
suitable power and cooling adjustments, as well as reporting this
state to the CSA code 220, follows below. The thermal states of
each MCM are monitored and the state of each MCM is communicated to
a function that determines the proper clock cycle time, called the
Cycle Steering Application (CSA) code 220. This function tells the
CSA code 220 both which cycle time range of the circuits are now
operating in and whether the cause of the failure of the primary
cooling means has been repaired or not.
[0040] In particular, PCC 210 continually monitors and posts
"cooling state" data to the CSA code 220 indicated generally as
292. The thermal state is defined by discrete temperature ranges
that are associated with a given clock speed as the proper speed to
operate. In other words, the full operating temperature range from
coldest to ambient to shut-down for thermal protection is
subdivided into smaller discrete operating ranges. The coldest
steady state temperature range is called the normal state, and is
the temperature range kept under normal primary cooling means
(e.g., MRUs 250, 252 and cooling units 10). When the primary
cooling means no longer functions properly, the cooling state,
sensed via the MCM sensors 276, is reported as a specific "degrade
state". By way of example, there may be between 2 and 4 degrade
states between normal operation and thermal shut-down, but more or
less are also contemplated, and hence, these concepts are not
limited to between 2 and 4. Within a given degrade state, there
exists one "optimum" set of clock speeds.
[0041] The PCC 210 reads the actual current 294 and voltage 284
being supplied to each MCM as well as its temperature 286. Based on
the leakage characteristics of the CMOS technology, the capacity
left in the power supply providing the current to the MCM, and
operating temperatures, the PCC 210 may either increase or decrease
or leave alone the applied voltage level to each set of circuits
indicated generally 296.
[0042] When the voltage is increased, the increased voltage enables
a higher range of operating temperatures before a given degrade
state is indicated to the CSA code 220 to slow the clocks. Hence,
the higher voltage can delay the need to operate in a slower clock
range. This is because CMOS switches faster at higher voltages
somewhat offsetting the slowing effects of warmer circuits.
[0043] Normally, it is desirable to increase voltage applied to the
circuits to offset some of the slowing effect on circuit switching
of warmer circuits. Typically, a 6% increase in voltage will cause
circuits to switch about 4% faster, offsetting a 25.degree. C.
temperature rise. However, with recent circuit technology, power
increases strongly with higher temperature and increased voltage.
In some cases it may require the voltage to be dropped when the
junction temperature rises significantly, even though this lowering
of voltage will increase the amount of slowing of the clock
frequency that is needed. This disclosure includes all three
voltage responses to loss of normal cooling: doing nothing,
increasing voltage, and lowering voltage. A voltage alteration may
be done to all components in a system or just to specific
electronics components that are exceeding normal cooling
limits.
[0044] Under circumstances where additional leakage currents due to
hotter CMOS circuit temperatures cause concern of either heating
the MCM beyond its safe operating temperature range or requires
additional current than the DCAs are able to provide, the PCC 210
lowers the voltage applied to the CMOS circuits when a temperature
degradation occurs. The effect on the "cooling degrade state" is to
hasten its arrival as the combination of lower voltage and warmer
circuits requires faster clock speed adjustments.
[0045] The PCC 210 takes into account both the MCM temperatures and
applied voltage when it notifies the CSA code 220 of a change in
"cooling state". The PCC 210 continually monitors the MCM
thermistors 276 and provides the MRU with information if a sensor
value is erroneous as well as the actual good values.
[0046] The PCC 210 sends the message to the CSA code 220 when the
first degrade state is reached, indicating that the primary cooling
system is not functioning normally. When it has been determined
that this degrade state is due to a failure of the cooling
hardware, the PCC 210 sets a fault flag for the primary cooling
system, which is not removed until the primary cooling system is
repaired. The PCC 210 posts this interrupt to the CSA code 220.
[0047] The PCC 210 automatically turns on the backup cooling
blowers or cooling fans 254 if the temperatures are above
acceptable levels for the primary cooling system. The fan speeds
are controlled in such a manner that the MCM temperature will not
oscillate between cooling states unless the room ambient also
oscillates.
[0048] The PCC 210 turns on the backup cooling blowers 254 at a
speed to provide a temperature sufficiently above the temperature
the first degrade state occurred so as to prevent "cooling state
oscillation" when the backup blowers 254 are first turned on
generally indicated at 298. Steady state air cooling mode will be
in degrade one or a slower degrade state, but if the backup blowers
254 are turned on immediately after the first degrade state is
posted, then the additional backup cooling may cause a temporary
spike down into the normal range temperature only to be soon
followed by revisiting the first degrade state. It will be
recognized by one skilled in the pertinent art that it is
advantageous to minimize the occurrences of changing degrade
states.
[0049] The PCC 210 continually samples the current and voltage
being used by each MCM and communicates this power data to the MRU
code as MCM powers state 284. The PCC 210 also suitably adjust the
power supply voltage levels at 296 being applied to the circuits.
Raising the voltages will offset some of the speed lost by higher
operating temperatures for some servers still operating in a safe
temperature range and with extra power available from the power
supply. For an MCM within server 240 which is operating near its
upper temperature limit or for which the power supply has no
additional current to supply, the PCC 210 either leaves the voltage
unchanged or lowers it to reduce leakage currents in CMOS circuits.
Hence, by sensing MCM temperatures and current being used by the
MCM, the PCC 210 determines what if any voltage adjustment is
suitable.
[0050] At all times, the existing temperatures and voltage
conditions together define a suitable "thermal state" or range
within which a specific set of clock speeds is optimum. The PCC 210
notifies the CSA code 220 of the proper speed range or "thermal
state" that the MCMS are operating in at all times at 292. This
speed range may also be called a degrade state as described
above.
[0051] The PCC 210 maintains a cooling state for each MCM available
for the CSA code 220 to monitor at any time. The PCC 210 also
provides periodic redundancy checks to insure that the backup
blowers 254 are operating properly. When a primary cooling source
having a fault, such as an MRU, is repaired, the PCC 210 clears
defect status registers set which are visible to the CSA code 220.
Likewise, the PCC 210 also sends an interrupt to the CSA code 220
if the primary cooling system, e.g., MRUs 250, 252, needs
service.
[0052] The Cycle Steering Application (CSA) code 220 provides a
fail-safe method of adjusting the clock speeds in an optimum manner
when the cooling state changes. This method of clock speed
adjustment includes determining if a cooling failure has been
repaired prior to increasing the clock speeds to prevent
oscillating clock speeds. It should be noted that the clock speed
follows the temperature and voltage conditions at all times.
Further, the time from a change of circuit temperature to a
corresponding change in clock speed is slow enough that the
temperatures of the circuits change minimally, less than about
1.degree. C., during this process.
[0053] The CSA node 220 includes an interrupt handler that reads
directly from the PCC 210 the cooling state of each MCM as well as
receiving interrupts on these states.
[0054] For systems with multiple processor books or nodes, the CSA
code 220 determined which MCM has the slowest cooling state. This
is the state that governs the safe clock speed of the system
indicated generally at 310 in FIG. 2. The multiple clock boundaries
on multiple oscillators with predefined ratios are always
maintained.
[0055] The CSA code 220 determines if any cooling defective
hardware registers are set whenever a cooling state is increased
calling for a faster clock speed. If the hardware defect register
is set, it means the cause of the cooling degradation has not yet
been fixed and the change in cooling state is likely due to
transient change in ambient or other transient conditions. Hence,
the server clock speeds are not re-adjusted faster until the
defective cooling hardware is replaced and the register cleared.
This is true even after the machine is re-initial microcode loaded
(reIMLed) or rebooted. If there is uncertainty in the cooling state
due to communication problems, the slowest, safest cooling state is
employed by the CSA code 220.
[0056] When the CSA code 220 determines it is appropriate to make a
change in several clock speeds, it alters the phase lock loops
(PLL) on the clock synthesizers in a sequence of very small steps
until its new targeted clock speed is reached generally indicated
as 312. The phase lock loops are stepwise changes always retaining
the optimum operating ratio between the various clocks that may be
affected. The steps are sufficiently small to pose no risk to
proper operation due to change in clock ratios during this
adjustment process.
[0057] Every step is performed in a two step commit algorithm,
e.g., the current step and the next step PLL values are saved in a
persistent storage concept made up by using SEEPROMS residing on
the current and backup cage controller 262, 262. After the change
is written to the PLL and read back for verification, the saved
current value is updated. This is done to provide protection in
case a speed change is interrupted by a cage controller
switchover.
[0058] The width of the small steps taken on the phase lock loops
is less than the normal jitter of the phase lock loop normal
output. This allows the step variation not to be detected by the
target clock receiving circuitry. In this manner, all of the
affected clocks are stepped in small increments until the targeted
clock speed is achieved.
[0059] The PLLs are on two oscillator cards 263, one in charge, one
in backup mode. At all times the optimum ratio between clocks is
maintained as the phase lock loops are moved in minimal increments
or decrements.
[0060] Prior to power good time, the CSA code 220 issues a
"Pre-Cooling" command to insure that the MCM temperatures are in
proper normal state prior to turning on the clocks. This also
prevents a sudden surge of power from the CMOS logic beginning to
switch. Without pre-cool, this could cause a quick degrade state to
occur because the refrigerant system takes some time to get its
cooling cycle established. When pre-cooled state is reached the PCC
210 notifies the CSA code 220 of the same and IML is initiated.
[0061] The PLLs are initially loaded with a pattern, which is hard
wired on the cards and loaded in parallel at power good time.
Normally, PLLs are loaded serially, but this is exposed to shift
errors which would lead to wrong clock speed settings.
[0062] The exact process of initializing clocks includes first
verifying the right oscillator card 263. Then, the pattern matching
the actual system speed is loaded into the line drivers and read
back to insure that there are no errors or hardware failures. Next,
the loaded and verified pattern is read into the phase lock loops,
with this pattern again read back to be verified. Now the system
clock is started using the phase lock loop output as input. At the
completion of IML, the system is degraded to its slowest clock
state and upgraded back to its normal state with the required
number of small incremental steps to the phase lock loops. This
insures that all necessary patterns can be loaded into the phase
lock loops without system error. This process takes a fraction of a
second to complete on every server that is IMLed.
[0063] The pattern to be loaded for speed adjustment purposes such
as when going from one cooling state to another is generated by a
set of digital I/O lines controlled by the FGAs DIO engines, which
is a part of the cage controller (cc) hardware. The FGAs DIO
engines are digital I/O lines controlled by cage controller code
that interface to the PLLs that control the system oscillators 263.
They are CSA code driven which is running on the PU Book 0 cage
controller (cc). Before changing the PLL pattern due to a change in
cooling state, the existing pattern is monitored to make sure the
adjusting processes were not interrupted, by saving the line
settings of the current pattern.
[0064] The CSA code 220 issues a warning service reference code
(SRC) to the operator whenever the CSA code leaves normal clock
speed. When the service is completed, the PCC 210 removes the error
states and interrupts the CSA code 220. The CSA code 220 removes
SRC once notified.
[0065] The CSA code 220 monitors the actual speeds used for an IML
to assure these speeds are never increased in actual operation even
though the cooling state later permits the increased speed. The
reason for this is that the initialization of "Elastic Interfaces"
(EI) done during IML allows only for speed reduction and its
clearing, not faster speeds than those present during IML
initialization and self-tests.
[0066] Hence, the CSA code 220 notifies the operator that re-ILM
should be avoided while a cooling failure service register is
flagged so that when the cooling hardware problem is repaired, the
server can return to its fast normal speed without needing a
subsequent re-IML. Also contemplated is a repair and verify
procedure that verifies that the clocks have returned to full speed
while a customer engineer is present.
[0067] As a further enhancement on the above-described cooling
system, a polytetrafluorethylene coating is employed on selected
pressure drop areas of expansion structures within the vapor
compression refrigeration system.
[0068] As noted, it has been discovered that material can
agglomerate in certain pressure drop areas of the expansion
structures within the refrigeration system. During refrigerant/oil
transport, certain impurities and chemically reacted byproducts may
come out of solution in the pressure drop areas as the refrigerant
cools down. By way of example, FIGS. 4 & 5 depict part of an
expansion valve, generally denoted 400, which includes a first
element 410 having an expansion orifice 430, and a second element
420 having a tapered expansion pin 440. As shown, the expansion pin
440 controls the amount of refrigerant passing through expansion
orifice 430, where refrigerant is assumed to flow left-to-right in
the drawings illustrated. For the cooling applications described
hereinabove, the expansion pin 440 is stepped open in very small
increments to allow controlled flow of refrigerant through
expansion orifice 430 into a pressure drop area defined between
opposing surfaces 450 of elements 410 & 420
[0069] During refrigerant/oil transport through a hot compressor,
any long-chain molecules and other typically non-soluble compounds
at room temperature can go into solution in the hot mixture. These,
as well as other physically transported impurities, then fall out
of the solution when the refrigerant/oil cools down, for example,
in the pressure drop areas of the expansion structure. A layer of
"waxy" material can build up in the pressure drop areas and act as
a sticky substance which then catches other impurities. FIG. 6
depicts one example of an expansion pin 440 wherein contaminant
material 460 has amassed in certain pressure drop areas of surfaces
of the pin exposed to the refrigerant flow path. This amassing of
material can interfere with the normal control volumes and
interfere with the control of motor steps (e.g., due to
unpredictable vavle characteristic changes). This is particularly
true in a vapor compression refrigeration system employed as
described above since the control of the expansion valves in this
implementation is very sensitive and refrigerant expansion
structure geometries are typically very small. Experimentation has
shown that cleaning contaminant material from the pressure drop
areas of expansion valves will typically fix any valve control
problem resulting therefrom.
[0070] Thus, the solution presented herein is to apply a
polytetrafluorethylene coating to at least portions of one or more
expansion structures within the vapor compression refrigeration
system in the pressure drop areas of the expansion structures. For
example, FIG. 7 depicts a polytetrafluorethylene coating 770 over
an expansion pin 700 of an expansion valve to be disposed within
the vapor compression refrigeration system. In FIG. 8, the
polytetrafluorethylene coating is shown also disposed on the inner
surface of element 710 defining expansion orifice 730 in the
pressure drop area of the expansion valve defined between the
opposing surfaces 750 of element 710 and element 720, that is, the
area which contains the tapered expansion pin 740 as shown. The
polytetrafluorethylene coating can be applied to the exposed
surfaces of a refrigerant expansion structure in the pressure drop
area employing any conventional technique, such as vapor
deposition. The polytetrafluorethylene coating has a thickness
sufficient to inhibit the accumulation of material in any pressure
drop area without changing a pressure drop characteristic of the
pressure drop area. For example, if the expansion orifice is 30
mils in diameter, then the thickness of the polytetrafluorethylene
coating may be 5 microns or less. Again, the goal of applying a
polytetrafluorethylene coating is to make the exposed surfaces
sufficiently slippery in the pressure drop areas of the expansion
structures to inhibit the agglomeration of material onto those
surfaces. This goal is achieved by the combination of refrigerant
force through the pressure drop area and the surface energy
properties of the polytetrafluorethylene, which together will
reduce or eliminate contaminants from agglomerating.
[0071] Although preferred embodiments have been depicted and
described in detail herein, it will be apparent to those skilled in
the relevant art that various modifications, additions,
substitutions and the like can be made without departing from the
spirit of the invention and these are therefore considered to be
within the scope of the invention as defined in the following
claims.
* * * * *