U.S. patent application number 13/472899 was filed with the patent office on 2012-11-29 for air cooling unit for data centers.
Invention is credited to Eric Derasse, Stephen Madaffari.
Application Number | 20120298334 13/472899 |
Document ID | / |
Family ID | 47218438 |
Filed Date | 2012-11-29 |
United States Patent
Application |
20120298334 |
Kind Code |
A1 |
Madaffari; Stephen ; et
al. |
November 29, 2012 |
Air Cooling Unit For Data Centers
Abstract
An air handling unit utilizing a humidifier in conjunction with
a heat exchanger to provide a means for free cooling recirculating
return air with evaporatively cooled outside air. A first air
stream comprising outside air can be circulated through the
evaporative humidifier and a first portion of the energy recovery
heat exchanger, while a second air stream comprising recirculated
inside air can be circulated through a second portion of the heat
exchanger. The outside air will be humidified as it circulates
through the humidifier, thereby cooling the outside air to its
adiabatic saturation temperature. The heat exchanger will cool the
recirculating inside air with the evaporatively cooled outside
air.
Inventors: |
Madaffari; Stephen;
(Greenwich, CT) ; Derasse; Eric; (Manhasset,
NY) |
Family ID: |
47218438 |
Appl. No.: |
13/472899 |
Filed: |
May 16, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61491057 |
May 27, 2011 |
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Current U.S.
Class: |
165/104.13 ;
165/96; 62/259.2 |
Current CPC
Class: |
H05K 7/20745
20130101 |
Class at
Publication: |
165/104.13 ;
165/96; 62/259.2 |
International
Class: |
F25D 31/00 20060101
F25D031/00; F28F 27/00 20060101 F28F027/00; F28D 15/02 20060101
F28D015/02; F28D 15/00 20060101 F28D015/00 |
Claims
1. An air handling unit for conditioning air, comprising: a. A
humidifier positioned in a first air stream for humidifying the
first air stream; and b. A heat exchanger positioned partially in
the first air stream and partially in a second air stream, the heat
exchanger capable of transferring heat from the second air stream
to the first air stream.
2. The air handling unit of claim 2, wherein the first air stream
comprises outside air, and wherein the second air stream comprises
recirculated inside air.
3. The air handling unit of claim 2, wherein the humidifier cools
the first air stream up to its adiabatic saturation
temperature.
4. The air handling unit of claim 3, wherein the heat exchanger is
positioned partially within a first air duct and partially within a
second air duct.
5. The air handling unit of claim 4, wherein the humidifier is
positioned within the first air duct.
6. The air handling unit of claim 6, wherein the humidifier is
positioned within a separate air duct connected to the first air
duct.
7. The air handling unit of claim 4, wherein the first air stream
flows through the first air duct, and wherein the second air stream
flows through the second air duct.
8. The air handling unit of claim 7, wherein the heat exchanger
comprises a first portion positioned within the first air duct, and
a second portion positioned within the second air duct.
9. The air handling unit of claim 8, further comprising a supply
fan for circulating the cooled second air stream within a
conditioned space.
10. The air handling unit of claim 9, further comprising an exhaust
fan for discharging the humidified first air stream from the air
handling unit.
11. The air handling unit of claim 10, further comprising a
mechanical cooling device positioned in the second air stream for
further cooling the second air stream before the second air stream
is recirculated by the supply fan within the conditioned space.
12. The air handling unit of claim 11, wherein the first air duct
comprises an outside air inlet and an exhaust air outlet, and
wherein the second air duct comprises a return air inlet and a
supply air outlet.
13. The air handling unit of claim 12, wherein the supply fan
circulates the second air stream successively through the return
air inlet, the second portion of the heat exchanger, the mechanical
cooling device, and the supply air outlet.
14. The air handling unit of claim 13, wherein the exhaust fan
circulates the first air stream successively through the outside
air inlet, the humidifier, the first portion of the heat exchanger,
and the exhaust air outlet.
15. The air handling unit of claim 15, further comprising a
plurality of dampers for controlling the flow of air in the air
handling unit.
16. The air handling unit of claim 7, wherein the heat exchanger is
a heat pipe, the heat pipe comprising a cold deck portion and a hot
deck portion, wherein the cold deck portion is positioned within
the first air duct, and wherein the hot deck portion is positioned
within the second air duct.
17. The air handling unit of claim 7, wherein the heat exchanger is
a heat wheel.
18. The air handling unit of claim 7, wherein the humidifier is an
evaporative humidifier.
19. The air handling unit of claim 3, wherein there is
substantially no exchange of moisture between the first air stream
and the second air stream.
20. The air handling unit of claim 3, wherein the dew point of the
second air stream remains substantially unchanged.
21. An air handling unit for conditioning air, comprising: a. a
humidifying means positioned in a first air stream for humidifying
the first air stream up to its adiabatic saturation temperature;
and b. A heat exchanger positioned partially within the first air
stream and partially within a second air stream, the energy
recovery heat exchanger cooling the second air stream using the
humidified first air stream, wherein there is substantially no
exchange of moisture between the first air stream and the second
air stream.
22. The air handling unit of claim 21, wherein the humidifying
means is selected from the group consisting of an evaporative
humidifier, an ultrasonic humidifier, a spray mist humidifier, a
steam vaporizer, a drum style humidifier, and a disc wheel style
humidifier.
23. The air handling unit of claim 21, wherein the heat exchanger
is selected from the group consisting of a heat pipe, a heat wheel,
and a fixed-plate exchanger.
24. A data center comprising: a. a conditioned space housing
electronic equipment; b. an air handling unit for conditioning the
air in the conditioned space, the air handling unit comprising: i.
a humidifier positioned in a first air stream, the humidifier
capable of cooling the first air stream up to its adiabatic
saturation temperature by humidifying the first air stream; and ii.
A heat exchanger positioned partially within the first air stream
and partially within a second air stream, the energy recovery heat
exchanger cooling the second air stream using the humidified first
air stream; c. an exhaust fan positioned in the first air stream
for discharging the humidified first air stream from the air
handling unit; and d. a supply fan positioned in the second air
stream for circulating the second air stream within the conditioned
space.
25. The data center of claim 24, wherein the heat exchanger is
positioned partially within a first air duct and partially within a
second air duct.
26. The data center of claim 25, wherein the first air stream flows
through the first air duct, and wherein the second air stream flows
through the second air duct.
27. The air handling unit of claim 26, wherein there is
substantially no exchange of moisture between the first air stream
and the second air stream.
28. The air handling unit of claim 26, wherein the dew point of the
second air stream remains substantially unchanged.
29. A method for cooling a conditioned space, comprising: a.
Providing an air handling unit for conditioning the air in the
conditioned space, the air handling unit comprising a humidifier
and a heat exchanger, the heat exchanger defining a first portion
and a second portion; b. Circulating an outside air stream
successively through the humidifier and the first portion of the
heat exchanger; c. Circulating an inside air stream through the
second portion of the heat exchanger to cool the inside air stream;
and d. Supplying the inside air stream to the conditioned
space.
30. The method of claim 29, wherein the circulated inside air is
further cooled by a mechanical cooling device before the circulated
inside air is supplied to the conditioned space.
Description
I. CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of U.S. Provisional
Application Ser. No. 61/491,057 filed May 27, 2012.
II. BACK GROUND
[0002] Data centers--facilities that primarily contain electronic
equipment used for data processing, data storage, and
communications networking--have become common and essential to the
functioning of nearly every sector of the economy to aid business
processes, information management, and communications functions.
Increasing demand for computer resources has led to significant
growth in the number of data center servers, along with a
considerable increase in the energy used by these servers and the
cooling infrastructure that supports them. The cooling
infrastructure for data centers is estimated to account for 50
percent of the total energy consumption of data centers. See U.S.
EPA Report to Congress on Server and Data Center Energy Efficiency,
Public Law 109-431 (August 2007).
[0003] The continuous operation of the electronic equipment
generates a significant amount of heat. The role of data center
air-conditioning systems is to remove this heat from the data
center to keep the components of the electronic equipment within
the manufacturers' specified temperature and humidity ranges.
Cooling in data centers is often provided by computer room air
conditioning units, where the entire air handling unit is situated
on the data center floor. The air handling unit contains fans,
filters, and cooling coils and is responsible for conditioning and
distributing air throughout the data center. In most cases, air
enters the top of the air conditioning unit and is conditioned as
air passes across coils containing chilled water pumped from a
chiller located outside of the data center room. The conditioned
air is then supplied to the electronic equipment (primarily
servers), typically through a raised floor area. Fans within the
servers pull the conditioned air through the servers. The warmed
air then stratifies toward the ceiling and eventually makes its way
back to the air conditioning unit intake. Most air circulation in
data centers is internal to the data center zone. To maintain a
controlled environment, the majority of data centers are designed
so that only a small amount of outside air enters.
[0004] Due the increased energy and capital costs associated with
the expanded use of computer resources, there has been mounting
interest in opportunities for energy efficiency in the information
technology (IT) industry. Air-side economizers are increasingly
being considered as a viable option for lowering the energy usage
of a data center's cooling infrastructure. An air-side economizer
is a type of air handling unit which takes advantage of cold
outside temperatures to provide "free cooling" cycles that reduce
or eliminate the need for the mechanical air cooling (i.e., cooling
via compressors, chillers, cooling media pumps, etc.) employed by
traditional data center air-conditioning systems.
[0005] Given that a data center must run continuously for a total
of 8,760 hours per year, significant energy savings can be achieved
with a typical air-side economizer when the outside air conditions
fall within the allowable ranges. However, the operating hours of
an air-side economizer are dependent on the outside air
conditions--namely, the air temperature and air humidity. An
air-side economizer can provide free cooling any time the outside
temperature is below the required supply temperature and below the
required supply dew point for the controlled environment. The
economizer cycle can provide partial free cooling by reducing the
mechanical cooling load when the outdoor temperature is higher than
the required supply temperature but the outdoor air dew point is
less than the dew point of the return air. In the context of data
centers, the American Society of Heating, Refrigerating and Air
Conditioning Engineers (ASHRAE) has provided the following
recommended and allowable temperature and humidity ranges for data
centers:
TABLE-US-00001 Recommended Allowable Temperature 18-27.degree. C.
(64.5-80.6.degree. F.) 15-32.degree. C. (59-90.degree. F.) Humidity
5.5-15.degree. C. Dew Point 20%-80% Relative (41.9-59.degree. F.)
Humidity
See "Thermal Guidelines for Data Processing Environments", ASHRAE
Technical Committee 9.9 (2004).
[0006] Air-side economizers typically are integrated with a
mechanical cooling system in order to assure the environmental
integrity of the controlled environment regardless of the outside
air conditions. A typical air-side economizer unit is shown in FIG.
1. The flow of air within the ducts of the air handling unit 1 is
controlled by dampers 10, 11, and 12. Cooling coils 15 can be
positioned within the air handling unit 1 to provide mechanical
cooling when needed. An automated control system allows the
economizer to operate in various modes depending on the outside air
conditions, thereby optimizing the free cooling potential of the
air handling unit while preserving the controlled environment. For
instance, during cool weather, the air handling unit 1 can operate
in full economization mode. In this mode, the air handling unit 1
can achieve the targeted supply air temperature without mechanical
cooling by modulating the outside air damper 10 and the return air
damper 11 to achieve the appropriate mix of cool outside air and
warm return air. During mild weather, the air handling unit 1
operates in partial economization mode. In this mode, the outside
air can provide some cooling capacity, but not enough to satisfy
the entire cooling load. Thus, mechanical cooling is required to
supplement the economizer cooling provided by the outside air.
[0007] Air-side economizers have proven to be an effective tool in
reducing energy usage in cool climates and mild climates having low
humidity. However, the efficiencies provided by current-generation
air-side economizers are significantly reduced or altogether
eliminated in humid climates. Humidity control is a concern for
conditioned spaces, particularly in data centers containing
electronic equipment. Exposing electronic equipment to overly humid
outside air can cause condensation to form on the equipment,
thereby negatively affecting the equipment's performance and/or
causing premature equipment failure. In cool, humid climates,
air-side economizer units can utilize dehumidifiers to remove
moisture from the outside air before introducing the air to the
conditioned space. However, dehumidifiers consume a considerable
amount of energy themselves, thus diminishing the overall
efficiencies achievable with the economizer unit. In warm, humid
climates, dehumidification is not a viable option. The
dehumidification of the outside air in the air handling unit is an
adiabatic process. As latent heat is removed from the outside air,
the sensible heat of the outside air will rise. Thus, the
dehumidification of the warm outside air will increase the
temperature of the outside air, thereby reducing or eliminating the
free cooling potential of the outside air.
[0008] Accordingly, there is a need for a new air handling unit
capable of efficient, economizer operation in humid climates.
III. SUMMARY
[0009] The invention disclosed herein is directed to an air
handling unit which utilizes evaporatively cooled outside air as a
cooling medium to cool return air recirculating in a conditioned
space. Because the outside air is not introduced into the
conditioned space, the air handling unit of the present invention
is capable of economizer operation in conditions where the outside
air humidity is above the targeted humidity level for the
conditioned space.
[0010] An air handling unit having features of the present
invention can comprise a humidifier positioned in a first air
stream and a heat exchanger positioned partially in the first air
stream and partially in a second air stream. The first air stream
can be humidified as it circulates across the humidifier, thereby
cooling the first air stream up to its adiabatic saturation
temperature--the temperature that the air stream would achieve if
it were allowed to become saturated adiabatically. The first air
stream--which is now at its maximum free cooling potential--can
then be circulated across the heat exchanger before being exhausted
from the air handling unit. The heat exchanger will transmit heat
energy from the recirculating second air stream to the cooled first
air stream, thereby reducing the sensible heat of the second air
stream. However, because the saturated first air stream does not
come into contact with the recirculating second air stream, the
humidity of the second air stream will not be affected.
[0011] The above summary is not intended to describe each
illustrated embodiment or every possible implementation. These and
other features, aspects, and advantages of the present invention
will become better understood with regard to the following
description, appended claims, and accompanying drawings.
IV. BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a schematic view of a prior art air-side
economizer.
[0013] FIG. 2 is a schematic view of an embodiment of the air
handling unit of the present invention configured for operation in
forced economization mode.
[0014] FIG. 3 is a schematic view of an embodiment of the air
handling unit of the present invention configured for operation in
full economization mode.
[0015] FIG. 4 is a schematic view of another embodiment of the air
handling unit of the present invention configured for operation in
full economization mode.
[0016] FIG. 5 is a schematic view of another embodiment of the air
handling unit of the present invention configured for operation in
full economization mode.
[0017] FIG. 6 is a schematic view of an embodiment of the air
handling unit of the present invention configured for operation in
partial economization mode.
V. DESCRIPTION
[0018] A preferred embodiment of the air handling unit 100 of the
present invention is shown in FIGS. 2-4. The air handling unit 100
comprises a humidifier 110 positioned in a first air stream 190 and
a heat exchanger 120 positioned partially in the first air stream
190 and partially in a second air stream 191.
[0019] In the preferred embodiment depicted in FIGS. 2-4, the
humidifier 110 is an evaporative humidifier, and the heat exchanger
120 is a heat pipe. The heat pipe 120 can comprise a cold deck
portion 121 disposed within a first duct 105, and a hot deck
portion 122 disposed within a second duct 106. The heat pipe, and
the first and second ducts 105, 106 in which the heat pipe is
mounted, can be installed in either a vertical or horizontal
orientation. In alternative embodiments, the heat exchanger 120 can
be a heat wheel, a fixed-plate exchanger, or other known energy
recovery mechanism. The humidifier 110 can be an ultrasonic
humidifier, a spray mist humidifier, a steam vaporizer, a drum
style humidifier, a disc wheel style humidifier, or any other known
means for humidifying air.
[0020] Air is circulated from the air handling unit 100 to a
conditioned space by means of a supply fan 150, while air is
exhausted from the air handling unit 100 by means of an exhaust fan
160. In certain embodiments, the air handling unit can also feature
an integrated mechanical cooling device 140 to supplement the free
cooling provided by the air handling unit 100. A plurality of
dampers 130, 131, 132, 133, 134 control the flow of air through the
air handling unit 100. A computerized control system can be used to
monitor the outside air conditions and automatically change
configurations, or modes, of the air handling unit 100 to maximize
the free cooling potential of the climate while maintaining the
integrity of the conditioned space.
[0021] FIG. 2 shows a schematic view of the air handling unit 100
configured in a forced economization mode. The air handling unit
100 will operate in a forced economization mode when the outside
air is above the targeted dew point for the conditioned space. The
humid outside air is not suitable for being circulated into the
conditioned space, but nevertheless can be utilized as a cooling
media so long as the air is not 100% saturated in its natural
state. In this mode, the first air stream 190 comprising outside
air will be routed successively through the outside air inlet 101,
through the evaporative humidifier 110, through open damper 132,
through the cold deck portion 121 of the heat pipe 120, and then
exhausted by the exhaust fan 160 through the exhaust air outlet
102. The outside air stream 190 will be humidified up to the air's
saturation point as it circulates through the evaporative
humidifier 110, thereby cooling the outside air stream 190 up to
approximately (e.g., within 2%) its adiabatic saturation
temperature before it is circulated through the heat pipe 120.
Meanwhile, the inside air will be in recirculation mode. A second
air stream 191 comprising recirculating inside air will be routed
successively through the return air inlet 103, through open damper
133, through the hot deck portion 122 of the heat pipe 120, through
the mechanical cooling device 140, through the supply fan 150, and
out the supply air outlet 104 and into the conditioned space. As
the recirculating inside air stream 191 goes through the hot deck
portion 122 of the pipe 120, heat energy will be transmitted from
the recirculating inside air stream 191 to the outside air stream
190, thereby reducing the temperature (i.e., the sensible heat) of
the inside air stream 191. Through this process, the inside air
stream 191 will be cooled to its lowest possible free cooling
condition. If additional cooling is needed, the control system can
activate the mechanical cooling device 140 to further cool the
inside air stream 191 to the target supply air temperature. In this
mode, the humidity of the controlled space should not be affected
since the humidified outside air stream 190 does not come into
contact with the recirculating inside air stream 191. While there
may be some air leakage through closed dampers 130, 131, and 134
(leak rate for current-generation dampers being approximately 3
CFM/sq.ft) in this mode, such leakage is negligible. There will be
substantially no exchange of moisture between the outside air
stream 190 and the inside air stream 191, thereby allowing the dew
point of the recirculating inside air stream 191 to remain
substantially unchanged.
[0022] FIGS. 3-5 show schematic views of the air handling unit 100
configured in a full economization mode. The air handling unit 100
will operate in a full economization mode when the outside air
temperature and dew point are at or below the targeted supply air
temperature and dew point. In this mode, the air handling unit 100
can satisfy the cooling load without any mechanical cooling,
thereby allowing the mechanical cooling device 140 to be
deactivated. The control system will modulate the air dampers 130,
131, 133, 134 to obtain the desired supply air temperature and
humidity. For instance, if the outside air conditions are ideal,
the first damper 130 can be opened fully and the conditioned space
can be cooled with 100% outside air (See FIG. 3). If the outside
air stream 190 is too cool, then the first damper 130 and the
fourth damper 133 can be modulated to achieve the appropriate mix
of cool outside air and warm return air (See FIG. 4). If the
outside air stream 190 is too dry, then the second damper 131 can
be opened to direct the outside air stream 190 through the
evaporative humidifier 110 before being supplied to the conditioned
space (See FIG. 5).
[0023] FIG. 6 shows a schematic view of the air handling unit 100
configured in a partial forced economization mode. The air handling
unit 1 will operate in a partial forced economization mode when the
outside air is above the targeted supply air temperature but below
the targeted dew point. In this mode, the outside air stream 190
will be routed through a two-stage cooling system. The first stage
involves the circulation of the outside air stream 190 through the
evaporative humidifier 110 to humidify the outside air to the
targeted level. As discussed above, the humidification of the
outside air stream 110--an adiabatic process--will result in a
proportional drop in temperature. The second stage, if necessary,
involves the circulation of the outside air stream 190 through the
mechanical cooling device 140 to further cool the outside air
stream 190 before it is supplied to the conditioned space.
[0024] Many modifications and other embodiments of the invention
set forth herein will come to mind to one skilled in the art having
the benefit of the teaching presented in the foregoing description
and associated drawings. For instance, in FIGS. 2-4, the
evaporative humidifier 110 and the exhaust fan 160 are shown as
being installed within the first duct 105, while the mechanical
cooling device 140 and the supply fan 150 are shown as being
installed within the second duct 106. However, one skilled in the
art will appreciate that the foregoing components can be installed
in separate, interconnected ducts in an alternative embodiment.
Further, although the air handling unit of the present invention is
described for use as a cooling system for data centers, the present
invention can be utilized as a cooling system for any conditioned
space. Therefore, it is to be understood that the inventions are
not to be limited to the specific embodiments disclosed and that
modifications and other embodiments are intended to be included
within the scope of the appended claims. Although specific terms
are employed herein, they are used in a generic and descriptive
sense only and not for purposes of limitation.
* * * * *